Step 6: Troubleshooting

Complete 3D printing troubleshooting guide. All common FDM 3D printing problems and their solutions.

It’s amazing what your 3D printer can produce. However, we’ve all had those infuriating moments when, despite everything, a simple model just refuses to print successfully.

We’ve had our fair share of print failures here at Moose 3D. With that, direct from our 3D printer troubleshooting experience, we’ve put together what we hope is the most comprehensive guide available to diagnose and fix common 3D printing problems, regarding both FDM technology.

Issues with warped prints, print bed adhesion, layer shift, and other 3D printing errors are not unique to FDM. Fear not though as we’re starting to expand this guide to reflect the rise in affordable desktop 3D printing, offering comprehensive 3D printing troubleshooting advice for those of you up to your elbows in wasted filament with nothing to show for your troubles.

Out of Filament

Nothing is printing even though the model has been set and configured correctly in the slicing software. However, try as you might when repeatedly sending the print to the printer still nothing happens bar the odd spit of filament emerging from the nozzle. Alternatively, a model is part way through the print and the filament extrusion stops but the nozzle continues to print into air.

What's causing this?

It’s an obvious problem that’s unmissable in many printers such as the Prusa i3 style machines where the filament reel is in full view, but on other printers such as XYZ DaVinci, Cel Robox and Ultimaker machines, the issue isn’t always immediately obvious.

These and many other printers either encase the filament within the design of the printer, or the filament hidden round the back.

Of course, some printers feature smart spools that feedback data to the software and highlight if the filament reel is close to, or out of material. However we all like to tinker and use our tweaked firmware or third-party software, and these sometimes work around such failsafes. And then other printers simply don’t feature any type of failsafe at all.

In all cases, especially with Bowden-style extrusion systems, you’re going to have to extract some remaining filament and then feed in fresh material.

Solution:

Check to see if the spool has run out of filament and replace it, if you have a filament runout sensor, it should beep and pause the printer, check the cables are still plugged in and have not slipped out.

Nozzle Too Close to Print Bed

Inexplicably, despite loading the filament and the print head moving without a hitch, no filament is depositing on the print bed.

What's causing this?

Quite simply, your nozzle may be too close to the print bed. If you’ve somehow tuned your print bed to mere microns from your nozzle opening, it’s unlikely the melted filament has room to escape. At best your print will be missing its first layers and have a higher chance of not sticking once the filament does extrude. At worst, you’ll cause a backup of melted filament in your hot end, possibly leading to a blockage.

Solution:

Z-AXIS OFFSET
Just raising the height of the nozzle slightly can often help. Most 3D printers in their system settings will allow you to set a Z-axis offset. To raise your nozzle away from the print bed you’ll need to increase the offset into the positive value. This also works for the reverse, with a negative offset helping to address your prints not sticking to your bed.

Be careful though, too high of an offset and it won’t stick to the platform.

LOWER THE PRINT BED
Alternatively, if your printer allows for it, you can achieve the same effect by lowering your print bed. This is the more troublesome fix though, as it requires you to re-calibrate and level the bed for even prints.

Blocked Nozzle

You initiate a print job but whatever you try, nothing comes out of the nozzle. Extracting the filament and reinserting doesn’t work.

What's causing this?

A small piece of filament has been left behind in the nozzle after changing spools, often because the filament has snapped off at the end. When the new filament is loaded, the piece of old filament that is left in the nozzle doesn’t allow the new filament to be pushed through.

A little printer maintenance can go a long way to reducing the chance of problems like a blocked nozzle affecting your extrusions. In fact you’ll often find that before a clog even appears, there is old carbonized filament sitting inside your nozzle. It can and will sit there for weeks or even months without you realizing, but there will be small signs in the quality of your prints.

The effects are often overlooked; such as small nicks in the outer walls, small flecks of dark filament, or small changes in print quality between models. These defects are often simply put down to the slight variations we come to expect from 3D printers, but really there could be something a little more sinister going on. A cleaning method known as the Atomic Pull or Cold Pull (which we detail below) can clear this up.

You’ll commonly see this if you frequently switch from a PLA to ABS, for example. A small amount of PLA is left in the nozzle, and it is heated beyond its normal melting point. That can mean it will carbonize and burn.

Likewise, switch between ABS and Nylon and again you’ll witness something similar. It’s not uncommon to see a wisp of smoke appear briefly as the new filament is fed through.

Solution:

UNBLOCK WITH A NEEDLE
If you’re lucky then unblocking can be a quick and straightforward process. Start by removing the filament. Then using your printer’s control panel (if it has one) select the “heat up nozzle” setting and increase it to the melting point of the stuck filament. Alternatively, hook your printer up to a computer running compatible control software and heat the nozzle using that. For PLA set the temperature to 220 °C. Once the nozzle reaches the correct temperature, use a small pin to clear the hole (being careful not to burn your fingers). If your nozzle is 0.4mm then you need a pin that is smaller; an airbrush cleaning kit works perfectly.

PUSH OLD FILAMENT THROUGH
If you find that the nozzle is still blocked, then you may be able to push the filament through with another bit of filament. Start by removing the filament as before and then remove the feeder tube from the print head. Heat up the hot end to 220 °C for PLA and then use another piece of filament to push this through from the top to try to force the stuck filament in the nozzle out. Usually, if the new filament hasn’t succeeded in unblocking, then the extra pressure you can exert by hand might just do the job. However, don’t push too hard as you’ll risk bending the horizontal printer rods.

Once the end clears use a needle to push through the nozzle and a brush to clean any filament excess.

DISMANTLE AND REBUILD THE HOT END
In extreme cases when the nozzle remains blocked, you’ll need to do a little surgery and dismantle the hot end. If you’ve never done this before then it’s a promising idea to make notes and take photographs so you know where everything fits when you reassemble. Start by removing the filament, then check your printer’s manual to see exactly how to dismantle the hot end.

Print Head Misses the Bed

There’s really no missing this one. At its most severe the noise will instantly alert you that something is very wrong.

When the printhead misses the bed it will usually also have reached the limit of either the X or Y position. As the head tries to travel beyond its furthest point noise will be generated through slipping belts, grinding cogs, or the head simply trying to rip through the side of the printer.

It’s very unlikely that your printer will succeed in producing a print in this state. And while it’s easy to fix, it’s not a problem that can be overlooked or dealt with at a later time.

What's causing this?

Misconfiguration, wrong printer selection, or worn-out or broken end stops are all common issues.

If the problem starts with a new printer, then the likelihood is that something is amiss with the printer’s configuration. Run through the setup process again and ensure that you have the correct firmware version for your printer.

Accidentally selecting the wrong printer from a dropdown list in your slicer program can be a common cause for this 3D printing problem. For example, trying to print using Ultimaker Go using print files configured for the Ultimaker 2.

When you set up your printer ensure that you have specified the correct print volume, again either in the printer’s firmware or through software. If the printer thinks it has a bigger print platform than it has then it’s going to try to use it, even if it’s not there.

If your printer is usually fine and then the problem occurs suddenly, start by double-checking your print preparation software. Something may have reset or been altered by an update! It’s not unusual for software to either revert to the default settings or to automatically select the latest printer version, even if that’s not the one you’re using.

And if all else looks fine then it could be that one of your ends stops in the printer has stopped working.

If this happens it can all get very messy.

Solution:

CHECK SLICER FOR CORRECT PRINTER
Before trying anything else make sure that you have the correct printer selected in your printing software. All printers are different so even if the print beds of two printers are the same it’s highly unlikely the other dimensions and settings will match exactly.

UPDATE FIRMWARE
If you’ve just purchased the printer and this issue is happening, make sure you have the latest version of the firmware installed. Once updated run through the setup process and double-check all settings, especially around the size of the print area are correct.

CHECK END STOPS
This will take a little more effort to diagnose. Watch the print head move. If it tries to push past the furthest point of one of its axes, check that an end stop hasn’t disconnected. If all looks fine (and none of the above steps fixed the issue for you) then replacing the end stops with new ones should be your next step.

Snapped Filament

The filament spool still looks full, and when you check there appears to be filament in the feed tube, but nothing’s coming out of the nozzle. This is more of an issue with Bowden feed printers than direct feed as the filament is hidden so breakages aren’t always immediately obvious.

What's causing this?

Caused by a number of issues but primarily old or cheap filament. Although the majority of filaments such as PLA and ABS do last a long time, if they’re kept in the wrong conditions such as in direct sunlight then they can become brittle. Then once fed into the printer no amount of adjustment is going to help.

Another issue is filament diameter, and this can vary through manufacturer and batch. Sometimes if the idler tensioner is too tight then some filament that still has a good amount of life left in it can snap under the pressure.

Solution:

REMOVE THE FILAMENT
The first thing to do is to remove the filament from the printer in the usual way. In the case of the Ultimaker select Maintenance and Change Material. As the filament will usually have snapped inside the tube, you’ll need to remove the tube from both the extruder and hot end. Then heat the nozzle and pull out the filament.

TRY ANOTHER FILAMENT
If after reloading the filament it happens again, use another filament to check to see if it’s not just the old brittle filament that should be disposed of.

LOOSEN THE IDLER TENSION
If the new filament snaps check that the idler tensioner isn’t too tight by loosening all the way. As the print starts, tighten until there is no slippage of the filament.

CHECK THE NOZZLE
Check the nozzle isn’t blocked and give it a good clean.

CHECK FLOW RATE AND TEMPERATURE
If the problem continues check that the hot end is getting hot and to the correct temperature. Also, check that the flow rate of the filament is at 100% and not higher.

Stripped Filament

Stripped or slipping filament can happen at any point of the print process, and with any filament. The result is that no filament is extruded from the hot end bringing your print to an abrupt end.

What's causing this?

Blockage, loose idler tensioner, wrong hot end temperature, these are just a few of the common causes, but all are typically easy to correct. The result of the problem is that the knurled nut or toothed gear in the extruder is unable to pull or push the filament through the printer. As the motor spins the small teeth on the gear that would usually grip and feed the filament through the system, instead wear it away until there is no longer any grip, and the gear and filament slip.

Solution:

HELP FEED THE SYSTEM
If the filament has just started to slip, you can usually tell by the noise and the appearance of plastic shavings, then apply some gentle pressure to the filament to help it through the system. This will often help to get the machine to print smoothly again.

ADJUST THE IDLER TENSION
Start by loosening the idler, feed in the filament and tighten until it stops slipping. Filaments vary in diameter so although the idler will absorb some difference in diameter some filaments will require fine adjustment.

REMOVE THE FILAMENT
In most cases you’ll need to remove and replace the filament and then feed it back through the system. Once the filament has been removed, cut the filament below the area that shows signs of slipping and then feed it back into the system. If the filament has snapped it may be past its usable best. Try it again and if it snaps again and you find the filament appears brittle discard and use another filament.

CHECK THE HOT END TEMPERATURE
If you have just inserted a new filament as the issue started, double-check that you have the right temperature.

Extrusion Stopped Mid-Print

Sometimes, for any of several reasons, the hot end will stop extruding molten filament.

What's causing this?

Typically, this 3D printing problem is attributable to two parts of the printing process — either something is wrong with your filament supply, or there’s a problem with the hot end/nozzle itself. It could be as simple a case as your filament has run out. Some printers obscure the spool, so you never know! Or it could be too tight of an idler on your extruder resulting in stripped filament that isn’t being fed into the hot end.

Alternatively, you could have a blockage in your hot end, preventing any further filament from being extruded.

Solution:

CHECK YOU HAVE ENOUGH FILAMENT
A little obvious, but even the best of us has momentary lapses in concentration. Many slicers now give a material estimation for your prints and judging that against the weight of your spool of filament and how much is left on it can give you a feeling for if there’s enough filament to complete your print.

CHECK FOR STRIPPED FILAMENT
Stripped filament can be responsible for a print failing mid-way through and can be caused by a myriad of issues. Check out our dedicated 3D printing troubleshooting tip on how to deal with stripped filament.

CHECK FOR A CLOGGED NOZZLE
A nozzle caked in old burnt filament can cause a few different print issues, one of which is blocking any new extrusions from being laid down. Check out our dedicated 3D printing troubleshooting tip on how to deal with a clogged nozzle.

CHECK FOR SNAPPED FILAMENT
An issue that affects Bowden-style extruder setups, snapped filament can cause a disjoin between the extruder and hot end. Thankfully, it’s easy to diagnose and fix, but it may be a sign that your filament is past its best. Check out our dedicated 3D printing troubleshooting tip on how to deal with snapped filament.

Print Doesn't Stick to Print Bed

Losing a print due to it not sticking to the print platform is a common issue and one that’s usually relatively easy to resolve. Unfortunately, a 3D print can break free at almost any time, from the first layer through to the last, which is especially infuriating.

Of course, it’s not always the printer’s fault and if you’ve tried to print a model that only has a small amount of contact with the platform then undoubtedly that’s going to be the issue. Imagine you’re trying to print a plane and the only contact the model has with the print platform is the wheels. It’s therefore unlikely to print without some type of build plate adhesion and brim, and that’s before you even start to look at supports.

Luckily because this problem is so common there are many straightforward ways to solve it.

What's causing this?

The most common cause is simply that the print just doesn’t bond to the surface of the print platform. The filament needs a textured base to adhere, so to solve the issue you’ll need to create a better bonding surface.

An unlevel print platform can be another major issue. If the platform is uneven then for some parts of the print the nozzle won’t be close enough to the platform to correctly extrude and bond the first layer.

Calibration can also be a major issue, over time the distance between the nozzle and platform can increase to the point where the initial layer is dragged rather than pushed into the print platform.

In all these cases you’re likely to see a spaghetti of filament appear above your half-formed model, just filament spaghetti or parts of your model dotted around the print platform.

Solution:

ADD TEXTURE
To increase the chances that filament will bond to the platform you need to add another material to add texture. The most common solution is to apply a thin layer of stick glue to the print platform, which can then be easily washed away with hot water. Another alternative for PLA is to add decorator’s tape. For filaments that require a heated platform of 40º and above, there is a variety of special tapes now available that are a little more heat resistant.

LEVEL THE PRINT BED
Every printer has a different process for print platform leveling, some like the latest Prusa models utilize an extremely reliable auto leveling system, others such as the Ultimaker have a handy step-by-step approach that guides you through the adjustment process. Refer to your printer’s manual for how to level your print bed.

ADJUST THE NOZZLE HEIGHT
If the nozzle is too high then the filament won’t stick to the platform, too low and the nozzle will start to scrape the print off. Find the Z-axis offset option in your printer’s settings and make small adjustments — into the positive to raise the nozzle away from the bed, and negative to lower it closer.

CLEAN THE PRINT PLATFORM
If you’re printing on a material such as glass, every so often it’s a clever idea to give it a good clean, especially if you frequently apply glue. The grease from your fingerprints and the excessive build-up of glue deposits can all contribute to the non-stickiness of the print platform.

APPLY BUILD PLATE ADHESION
Some models will print fine without a brim, but smaller items and those with only a small footprint in contact with the platform will require some type of Build Plate Adhesion. These can be added in your slicer software- — look for “Brim” and “Raft”.

Brim will add a single layer of a specified number of perimeter lines radiating out from where your print contacts the print bed; it’s the least wasteful of the two, and in our experience is the better option, provided you don’t mind taking a knife to your print to trim the brim away.

Raft adds just that to your print. Depending on the parameters you specify, you will get a shadow of your print’s footprint, printed in a thicker, better-adhering layer. Your print is then printed as usual on top of this. Rafts tend to create a rough, unpleasant surface where it touches your print, and use up more material than a brim. The benefit of a raft though lies in being able to simply snap the part off.

ADD SUPPORTS
As well as adding build plate adhesion, if your model has complex overhangs or extremities be sure to add supports to hold the print together during the process.

Supports Fell Apart

Printing complex models will require a support or two, and whilst supports can be a pain to remove, they’re unfortunately an essential part of modeling.

The job of support is simple, it supports, but occasionally they fail, leaving your model unsupported. You’ll notice that as your print is extruded parts of the support structure will look uneven, cracks may appear, or they’ll just start to look stingy.

Not only are the supports failing but the additional filament is ruining your model rather than ensuring it prints correctly.

What's causing this?

Support structures are complex things, and most slicer applications will provide you with several options. It’s all too easy to stick with the default settings, but this doesn’t guarantee success with your 3D printed overhangs. An important consideration is the type of support that will keep your model steady and supported throughout the print.

Lines and zig zags are easy to remove after the print has finished, but offer less rigidity during the print process. Triangles and grids offer more support but can be a pain to remove.

Take a simple bridge structure with thin uprights and then think about the supports. They will have a great deal of work to do keeping the model rigid, if you’ve opted for lines or zig zags then the likelihood is the model will move during the print process, breaking the delicate supports as it goes.

A rigid structure like a grid would be a better option.

Some slicing software enables you to print supports without platform adhesion. If this is the case then the small footprint of the support will struggle to bond directly with the print platform.

Finally, watch your printer print. If the printer is moving or vibrating more than it normally does, then check the details and just ensure that everything is tight. Once you’ve run through all the usual checks make sure to rerun the calibration process.

Solution:

SELECT THE CORRECT SUPPORTS
Look at the type of model you’re about to print. If there are large overhangs that connect sections of the model and these have good contact with the platform, try using lines or zig zag supports. If the model has less bed contact or needs much stronger supports, use grid or triangle supports.

ADD PLATFORM ADHESION
Make sure you have added some type of platform adhesion, such as a brim, so that the mounts have plenty of foundation to bond to.

INCREASE THE SUPPORT DENSITY
Try this as a last resort. Increasing the support density will offer your model a denser structure to rest on and will be less affected by any model movement but will be much tougher to remove.

CREATE IN-MODEL SUPPORTS
Supports that are overly tall can be susceptible to weakness. By adding a tall block as part of your print that ends just below where the supports are required, the supports are given a solid base without the need to print tall and weak.

CHANGE FILAMENT
Filament can become brittle as it reaches the end of its usable life span, and this usually shows in the quality of the supports. Swap the filament for a fresh reel and see if the problem improves

CHECK EVERYTHING IS TIGHT
Printer shakes and wobble can be a real issue. Give your machine the once over and make sure that everything is tight and re-calibrate if needed.

First Layer is Messy

The first layers of a print can often prove problematic. It could be that the print simply does not stick (which we covered with a different 3D printing troubleshooting tip, up top), or you’re finding unwanted lines that cause the bottom shell to have an unexpected look. Additionally, it’s entirely possible for any fine detail on the bottom of your print to congeal into a blur with little semblance of any surface design.

What's causing this?

These 3D printing problems are typical signs that the print bed hasn’t been leveled properly. If the nozzle is too far away from the bed, the bottom surface often shows unwanted lines, and/or the first layer does not stick. If the nozzle is too close, blobs may be the result.

Where you find detail is becoming undefined and blurry, the chances are your print bed temperature is a little too high.

Solution:

BALANCE BED TEMP & COOLING
To stop elephant foot from appearing in your 3D prints the base layers of the model need to be cooled sufficiently so that they can support the structure above. Apply too much cooling however, and you risk the base layers warping. Getting the balance right can be tricky, start by lowering the temperature of the print platform by intervals of 5 degrees, (to within +/- 20 degrees of the recommended temperature). If your Bottom / Top Thickness is set to 0.6mm then start the fan at a slightly lower height.

LEVEL PRINT BED
Often many print issues can be traced back to the level of the print platform. Each printer has a slightly different technique for print platform leveling. Start by calibrating yours according to your printer manufacturer’s recommended procedure.

Try printing a calibration cube and watch how the printer lays the filament on the bed. From printing the cube, you should easily be able to see if your bed is level from how evenly (or not) your layers are on the bed.

Similarly, you will be able to see if the nozzle is too close to the print platform and scraping through the molten filament, or too high and causing the filament to build up and blob.

RAISE THE NOZZLE
Just raising the height of the nozzle slightly can often help but be careful too high and it won’t stick to the platform.

CHAMFER THE BASE
Another option is to chamfer the base of your model. Of course, this is only possible if you have either designed the model yourself or have access to the original file. Start with a 5mm and 45º chamfer but experiment a little to get the best result.

Print Bows Out at Bottom (Elephant's Foot)

The base of the model is slightly bulging outwards, an effect otherwise known as “elephant foot”.

What's causing this?

This ungainly print defect can be caused by the weight of the rest of the model pressing down on the lower before they have properly cooled back into a solid – this is particularly an issue when your printer has a heated bed.

Solution:

USE A HEATED PRINT PLATFORM
The easiest solution is to use a heated print platform and set the temperature to a point just below the plastics melting point. This is called the “glass transition temperature”. If you get that temperature right, then the first layer will stay flat on the print platform. The print platform temperature is often set by the slicer software. You’ll normally find the recommended temperature for your filament printed on the side of the packaging or on the spool.

APPLY AN ADHESIVE TO THE PRINT BED
If you still find your print lifting at the edges, then apply a tiny amount of stick glue or 3DLac evenly on the bed to increase adhesion.

TRY A DIFFERENT PLATFORM TYPE
Change your print bed to one that offers better adhesion. Manufacturers such as Prusa use a PEI (Polyetherimide) print surface that offers excellent adhesion without glue. XYZPrinting supply textured tape in the box with some of their printers, a large sheet of masking tape, and again adding this works excellently, although only with nonheated print platforms. Zortrax 3D printers have a perforated print bed, models weld themselves to this surface eliminating the issue completely.

LEVEL THE PRINT PLATFORM
Print platform calibration can be another cause, run through the calibration process to check that the bed is level and nozzle height is correct.

INCREASE CONTACT
Increasing the contact between the model and bed is an easy fix and most print software has the option to add rafts or platforms.

ADJUST ADVANCED TEMPERATURE SETTINGS
If all else fails, then you’ll need to look at your advanced print settings both on your printer and in your printer software. Try increasing the print bed temperature by increments of 5 degrees.

In the slicer software look at the fan cooling, this is usually set so the cooling fans switch to full power at a height of around 0.5mm, try extending this to 0.75 to give the base layers a little more time to cool naturally.

Even if your printer has a heated print platform, it’s always recommended that you use glue and regularly calibrate the bed level.

Print Edges are Bending (Warping)

At the base of the model, the print bends upwards until it’s no longer level with the print platform. This can also result in horizontal cracks in upper parts and cause your print to come unstuck from the print bed.

What's causing this?

Warping is common as it’s caused by the natural characteristics of plastics. As the ABS or PLA filament cools it starts to contract very slightly; the problem of warping arises if the plastic is cooled too quickly.

Solution:

USE A HEATED PRINT PLATFORM
The easiest solution is to use a heated print platform and set the temperature to a point just below the plastics melting point. This is called the “glass transition temperature”. If you get that temperature right, then the first layer will stay flat on the print platform. The print platform temperature is often set by the slicer software. You’ll normally find the recommended temperature for your filament printed on the side of the packaging or on the spool.

APPLY AN ADHESIVE TO THE PRINT BED
If you still find your print lifting at the edges, then apply a tiny amount of stick glue or 3DLac evenly on the bed to increase adhesion.

TRY A DIFFERENT PLATFORM TYPE
Change your print bed to one that offers better adhesion. Manufacturers such as Prusa use a PEI (Polyetherimide) print surface that offers excellent adhesion without glue. XYZPrinting supply textured tape in the box with some of their printers, a large sheet of masking tape, and again adding this works excellently, although only with nonheated print platforms. Zortrax 3D printers have a perforated print bed, models weld themselves to this surface eliminating the issue completely.

LEVEL THE PRINT PLATFORM
Print platform calibration can be another cause, run through the calibration process to check that the bed is level and nozzle height is correct.

INCREASE CONTACT
Increasing the contact between the model and bed is an easy fix and most print software has the option to add rafts or platforms.

ADJUST ADVANCED TEMPERATURE SETTINGS
If all else fails, then you’ll need to look at your advanced print settings both on your printer and in your printer software. Try increasing the print bed temperature by increments of 5 degrees.

In the slicer software look at the fan cooling, this is usually set so the cooling fans switch to full power at a height of around 0.5mm, try extending this to 0.75 to give the base layers a little more time to cool naturally.

Even if your printer has a heated print platform, it’s always recommended that you use glue and regularly calibrate the bed level.

Infill Looks Messy and Incomplete

The internal structure of your print is missing or broken.

What's causing this?

There are several reasons for the misprinting of the internal structure. The most common is incorrect settings within the slicing software, but it can also be due to a slightly blocked nozzle.

Solution:

CHECK THE FILL DENSITY
In your slicing software check the infill density. A value of around 20% is normal; any less than this and you’re likely to have issues. For larger prints, you may want to increase this to ensure that the model has enough support.

DECREASE INFILL SPEED
The speed at which the infill is printed can have a major effect on the quality of the structure. If the infill is looking weak then decrease the infill print speed.

CHANGE THE INFILL PATTERN
Most slicing software enables you to change the internal structure. You can have a grid pattern, triangle, honeycomb, and more. Try selecting a different option.

CHECK YOUR NOZZLE
It might be that there is a slight blockage in the nozzle. While the blockage doesn’t affect the printing of the thicker exterior walls, because there is less flow for the internal structure the filament is getting caught.

Gaps Between Infill and Outer Wall

When you look at the top or bottom of the print, you can see a slight gap between the infill and the outer perimeter walls.

What's causing this?

Gaps between the perimeter and top layers used to be a frequent problem, but as printer accuracy has improved and the support for varied materials extends, it’s now less of an issue than it was.

However, the new wave of advanced materials is far less forgiving than the likes of PLA and ABS, and we’re starting to see a slight resurgence of the problem.

Gaps are caused by the filament used for the infill and outer walls not meeting and bonding. Handily, it’s one of the easiest things on this list to fix.

The most obvious cause of the problem is that the infill overlap is not set, or it’s set to zero. This means that the slicing software is telling the printer not to allow the two parts of the print to meet.

Another issue could be the order in which you have set the infill and outer walls to be printed. If you’re printing the perimeter first, then there is little or no overlap which can again cause the problem.

Solution:

CHECK THE INFILL OVERLAP
This is by far the most common issue and is easy to resolve. In your slicing software locate the ‘Infill Overlap’ option and increase the value.

  • In Cura, this is set to 15% by default. Raise it to 30%.
  • In Simplify3D you’ll find the option in ‘Edit Process Settings > Infill > Outline Overlap’. Again, increase the value. This setting is linked to the extrusion width, so the % value will be a % of whatever your extrusion width is. When adjusting this setting always keep it below 50% or you’ll start to see the effects of the overlap in the outer perimeters of your print.

 

PRINT INFILL BEFORE THE PERIMETER SHELL
If you’re printing with a thin outer wall the structure of the infill can show through. If this happens then you can switch the order by which the printer lays down the infill and perimeter layers. For example, in Cura check to see if you have ‘Infill prints after perimeters’ ticked.

INCREASE HOT END TEMPERATURE
Some of the latest advanced materials such as XT-CF20 are a little less forgiving when it comes to spreading due to the carbon fibers that make up part of their structure. When printing with these materials you may find that a slight 5-10º increase in hot end temperature makes all the difference.

LOWER PRINT SPEED
Okay, so you may be in a rush to get the printout, but printing at higher speeds can cause all sorts of issues if the printer isn’t perfectly calibrated. If you need to print quickly you can still avoid gaps by decreasing the speed of the top layer.

Infill is Visible from the Outside

The final print looks fine, but an outline of the internal support structure can be seen through the walls of the print. This is also often referred to as ghosting.

What's causing this?

The issue with ghosting happens due to the infill encroaching into the path of the perimeter. This effect is most visible when your print has thin walls. The problem is caused by the infill structure overlapping with the perimeter line as it’s being laid down. Although this ghosting is an issue it’s actually an important part of the printing process, as it helps the internal structure bond effectively to the external walls. Luckily, it’s quite easy to overcome.

Another cause of ghosting can be that you have set an incorrect wall thickness in relation to the nozzle size that you’re using. In normal printing conditions, wall thickness should be related to the nozzle size, so if you have a 0.4mm nozzle the wall thickness should be a multiple of this: 0.4, 0.8, 1.2, and so forth.

Solution:

CHECK THE SHELL THICKNESS
Make sure that the value you have selected for the shell thickness is a multiple of the nozzle size.

INCREASE THE SHELL THICKNESS
The easiest solution is to increase the shell thickness. By doubling the size, it should cover any overlap caused by the infill.

USE INFILL AFTER PERIMETERS
Most slicing software will enable you to activate Infill prints after perimeters.

  • In Cura open the ‘Expert Settings’ and under the Infill section tick the box next to ‘Infill prints after perimeters’
  • In Simply3D Click ‘Edit Process Settings’ then select ‘Layer’ and under ‘Layer Settings’ select ‘Outside-in’ next to the ‘Outline Direction’.

CHECK PRINT PLATFORM
Check around the model and if you see that the effect is more prevalent on one side than the other, the effect could be due to calibration. If so, run through the usual calibration process.

PRINT SHELLS TO YOUR ADVANTAGE
Depending on the type of model that you’re printing you can use the internal and shell printing order to your advantage. When you want a high-quality print with a good surface finish where the actual strength of the model isn’t important, select print from the Outside-in. If, however, the strength of the print is paramount, then select Print from Inside-Out and double the wall thickness.

The reason for the difference in strength is that when you print from the Outside-in you eliminate the small amount of overlap that causes the ghosting issue, but this also means that the actual structure won’t create the same bonding strength between the internal and external structure due to the lack of overlap.

Cracks Have Appeared in Tall Objects (Delamination)

There are cracks on the sides, especially on taller models. This can be one of the most surprising issues in 3D printing as it tends to manifest itself in larger prints and usually happens while you’re not looking.

What's causing this?

In a print’s higher layers, the material cools faster. The heat from the heated print bed doesn’t reach that high, and because of this, adhesion in the upper layers is lower.

Solution:

EXTRUDER TEMPERATURE
Start by increasing the extruder temperature; a good start would be to increase it by 10ºC. On the side of your filament box, you’ll see the working hot end temperatures, try to keep the temperature adjustment within these values.

FAN DIRECTION AND SPEED
Double-check your fans and make sure that they’re on and aimed at the model. If they are, try reducing their speed.

Layers Don't Line Up Well (Layer Shift)

As the print is forming, there appear to be a few issues with the quality. Look closer and you see that the layers aren’t aligning quite as they should. Look at the internal support structure and again the pattern looks slightly out. The outer wall, rather than being smooth, features slight misalignments that cause an uneven face. It’s highly likely that the issue only affects the print in one direction; front to back or left to right.

What's causing this?

Over time the parts of your 3D printer — such as nuts, bolts, and belts — will become loose and require a tightening. The effect of misaligned layers is like the cause of the more pronounced effects of shifting layers and there is no doubt that there is a crossover. If left unchecked, this problem will eventually result in shifting layers, but as the issue starts the visual effect on the prints is far less pronounced and can look quite different. The cause is usually linked directly to a loose belt.

Solution:

CHECK THE BELTS PART I
Start by checking each of the belts is tight but not overly tight. You should feel a little resistance from the two belts as you pinch them together. If you find that the top section of the belt is tighter than the bottom, then this is a sure-fire sign that they need a tweak and tighten. Some printers, such as the Original Prusa i3, come with belt tensioners built into them. Others can be retrofitted with 3D printed ones. If neither of these is an option for you, you may have to get your hands dirty and manually tighten the belt.

CHECK THE BELTS PART II
The printer belts are normally just one continuous loop hooked around two pulleys. A common issue is that over time the belt can slip on one pulley and gradually gets tighter on the top compared to the bottom — or vice versa — and again this can cause misaligned layers.

CHECK THE RODS ARE CLEAN AND OILED
Over time debris can build up on the rods, causing odd patches of higher friction which in turn can affect the free movement of the head and again cause layer shifting. A quick wipe and re-oil of the rods usually solves the issue.

CHECK FOR BENT OR MISALIGNED RODS PART I
If you see the print head falter at certain points, then it could be that one of the rods has become slightly bent. You can usually tell by switching off the machine so there’s no power going through the steppers and then moving the print head through the X- and Y-axis. If you feel resistance, then you know something is amiss. Start by seeing if the rods are aligned. If they are, remove them and roll them on a flat surface. If any are bent, then it will be obvious.

CHECK FOR BENT OR MISALIGNED RODS PART II
Many printers use threaded rods rather than lead screws and although these do the job, they do tend to bend over time. Don’t worry about dismantling your printer to see if they’re straight, simply use control software such as ‘Print run’ to move the print head up or down. If one of the Z-axis rods is bent, you’ll instantly see. Unfortunately, it’s almost impossible to accurately straighten a rod once it’s bent, but on the upside, it’s a good excuse to replace the old threaded rods for lead screws.

CHECK THE DRIVE PULLEYS
These are usually connected directly to a stepper motor or to one of the main rods that drive the print head. If you carefully rotate the pulley, you’ll see a small grub screw. Holding both the rod and the attached belt, give the belt a tug to force the pulley to turn. You should find that there is no slip between the pulley and stepper or rod. If there is tighten the grub screw and try again

Some Layers are Missing

There are gaps in the model because some layers have been skipped (in part or completely).

What's causing this?

The printer failed to provide the amount of plastic required for printing the skipped layers. For infrequent skipped layers, this can be referred to as temporary under-extrusion. There may have been a problem with the filament (e.g. diameter variation), the filament spool, the feeder wheel, or a clogged nozzle.

Alternatively, friction has caused the bed to temporarily get stuck. The cause may be that the vertical rods are not perfectly aligned with the linear bearings.

It’s also possible that there is a problem with one of the Z-axis rods or bearings. The rod could be distorted, dirty or suffering from excessive oil.

Solution:

MECHANICAL CHECK
It’s good practice to give your 3D Printer the once-over every now and again and the appearance of gaps in your 3D print is always a good sign that now is the time to give your 3D printer some love and attention. Start off by checking the rods and make sure that they’re all seated into either bearings or clips and haven’t popped out, shifted, or moved even slightly.

ROD ALIGNMENT CHECK
Make sure that all rods are still in perfect alignment and haven’t shifted. You can often tell by switching off the power (or disabling steppers) and then gently moving the print head through the X and Y-axis. If there is any resistance to the movement then something is wrong and it’s usually easy to tell if this is due to misalignment, a slightly bent rod or problem with one of the bearings.

WORN BEARING
When bearings go, they usually let you know about it by creating an audible din. You should also be able to feel uneven motion in the print head and when printing the machine looks like it’s vibrating slightly. If this is the case unplug the power and move the print head through the X and Y to locate the region of the broken bearing.

CHECK FOR OIL
Lubricating the joints is easy to forget, but keeping everything well-oiled is essential to the smooth running of the machine. Sewing machine oil is ideal and can be purchased from almost any haberdashery at an inexpensive price. Before you go applying liberally just check that the rods are clean and free of dirt and printing debris — a quick wipe of the rods before applying a fresh coat of oil is always a clever idea. When all rods look clean just dab on a little, but not too much. Then use printer control software such as Print run to move the head through the X and Y axis to make sure that the rods are evenly covered and moving smoothly. If you add a little too much oil don’t worry just wipe some off with a lint-free cloth.

UNDER-EXTRUSION
The final issue could be under-extrusion. Check out our dedicated 3D printing troubleshooting tip for under-extrusion here.

Print Leans When it Shouldn't

As the print forms it starts to lean. Instead of being straight and true, vertical edges are printed at an angle, and this angle isn’t consistent throughout the print. The severity could be increasing and decreasing at various stages.

What's causing this?

The cause of the issue is generally quite simple; one of the pulleys attached to a stepper motor is slightly loose, or one of the belts is rubbing against something and stopping the full travel of the head. All you need to do to correct the issue is to make sure that none of the pulleys are slipping and the grub screws that hold the pulleys in place are all tightened.

Although this should be a quick and straightforward fix, one issue you may experience as you go to tighten the pulleys is that the small grub screws that tighten onto the shaft of the motor aren’t always that easy to access. Firstly, diagnosing which pulley is causing the issue and then getting access to that pulley can be tricky and time-consuming.

Solution:

CHECK X- AND Y-AXIS
If your print is leaning to the left or right, then you have an X-axis issue. Back to front and you have a Y-axis problem. Once you’ve diagnosed which it is you can then check the belts and pulleys. If you have a printer such as the Prusa i3 then the process is straight forward, as the steppers are directly connected to the main drive belt. For the Ultimaker and other printers, the process can be a little trickier.

CHECK THE BELTS AREN’T RUBBING
Look around each of the belts and ensure that they’re not rubbing against the side of the machine or any other components. Also, check to see that the alignment of the belts is correct. If one is at a slight angle, then this can cause issues.

TIGHTEN THE STEPPER MOTOR COUPLER GRUB SCREW
Once you diagnose which axis is causing the issue, use an Allen key to tighten the corresponding coupler’s grub screw that attaches to the stepper motor.

CHECK ROD PULLEYS
More complex machines such as the Ultimaker 2 have a series of belts and pulleys. The main X and Y rods at the top of the machine feature eight pulleys. Go around each of these on the affected axis and tighten the grub screws for each. It’s unlikely that these will cause any slip but if one is loose then a belt may misalign.

Overhangs are Messy

You load your print into your slicing software, and everything looks good. Hit print and you find that some parts of the model print fine, whilst other parts end up as a stringy mess. OK this might seem obvious, and the issue of overhangs is often seen as a 3D printing newcomer mistake. But it’s surprising just how often even experienced 3D printers are hit with an overhang issue.

What's causing this?

The process of FFF requires that each layer is built upon another. It therefore should be obvious that if your model has a section of the print that has nothing below, then the filament will be extruded into thin air and will just end up as a stringy mess rather than an integral part of the print.

Really the slicer software should highlight that this will happen. But most slicer software will just let us go ahead and print without highlighting that the model requires some type of support structure.

Solution:

ADD SUPPORTS
The quickest and simplest solution is to add supports. Most slicing software will enable you to do this quickly.

  • In Simplify3D click Edit Process Settings > Support > Generate support material; you can the adjust the amount, pattern, and settings.
  • In Cura just select the desired support type from the Basic settings.

CREATE IN-MODEL SUPPORTS
Supports generated by software can sometimes be intrusive and result in support material getting stuck in impossible to remove places. Creating your own in your modeling application is a suitable alternative. It takes a bit more skill but can enable some fantastic results.

CREATE A SUPPORT PLATFORM
When printing a figure, arms and other extrusions are the most common areas that cause problems. Using supports from the print bed can also cause issues as they often must span quite large vertical distances; for structures that are supposed to be easily removed and fragile, this distance is prime for causing problems.

Creating a solid block or wall under arms etc and then creating a smaller support between the arm and block can be a great solution.

ANGLE THE WALLS
If you have a shelf style overhang, then an easy solution is to slope the wall at 45º so that the wall supports itself and removes the need for any other type of support.

BREAK THE PART APART
Another way to look at the model is to break it apart into separate prints. With some models this enables you to flip what would be an overhang and instead make it a base. The only issue with this is that you then have to find a way of sticking the two parts back together.

Print is Unusually Weak/Looks Wrong (Non-Manifold Edges)

Parts of your print are missing, or the final print is weak and falls apart despite the exterior quality of the print looking fine. Sections of the print look completely different from the print preview or the final print has geometry errors that make no sense.

What's causing this?

Non-manifold edges are a common cause of misshapen or odd prints. Non-manifold edges are the edges of models that can only exist in the 3D space and not the physical world.

For example, if you have two cubes in the real world and try to overlap them directly, it’s physically impossible as the solid outer walls prevent the two objects from intersecting.

In the 3D world you can simply intersect the two, they still exist as individual objects, but the software we use distinguishes between them regardless of the perceived oneness as we look at them.

To get the two to print correctly, the objects need to be merged so that any inner walls are removed and an object with a single undivided inner cavity is left.

Another common cause is if you have an object such as a cube and delete one of the surfaces. You have an object with a hole, it might look like a shape with five sides, but it only exists in the virtual 3D space, this is geometry with no physical form.

Although you can see the outer walls in the software, the walls that meet the hole only have dimensions on two axes. The third dimension which we see as the thickness of the wall is only illustrative and has no physical dimension. When it comes to slicing the model, the software does its best and, in many cases, will repair the hole. However, in more complex models, the effects can be interesting to say the least.

Solution:

USE LATEST SLICER SOFTWARE
Most of the latest slicer engines all support the automatic fixing of non-manifold edges but it’s still good practice to ensure that your models are correctly formed and print ready.

FIX USING STL FILE REPAIR SOFTWARE
If you’re already using the latest slicer software, then you might have noticed a notification telling you that your STL file features some non-manifold edges. Some software can fix this for you of course, and if you’re slicer can’t then there’s a suitable selection of STL file repair software that can be used on both desktop and the web. It’s a simple and easy task, just upload your file to your chosen software, let it identify any broken sections, then follow the instructions. If you didn’t get a notification on your slicer but your prints are coming out as a weird, messy blob this suggests you have some non-manifold edges in there. Try STL file repair software. It might not fix the problem, but it’s certainly something to try.

FIX ‘NON-MANIFOLD’ IN SIMPLIFY3D
In edit ‘Process settings’ click the ‘Advanced’ tab and select ‘Heal’ next to ‘non-manifold segments.

USE THE LAYER VIEW
In your slicer software use the layer view to check through the model so you can see where the issues appear. A quick slide through the layers will often highlight an easy to fix problem.

USE MODELING SOFTWARE TO FIX ISSUES
One of the easiest ways to fix models with non-manifold edges is to use software; Programs such as Blender and Meshmixer both have features built in that will quickly enable you to highlight problems with your models and fix them prior to slicing.

MERGE OBJECTS
Really, it’s better to fix your 3D models prior to importing them into your slicing software. To do this, make sure that when you have two objects that do intersect or overlap you choose the appropriate Boolean function to either intersect, merge or subtract.

Fine Detail Not Printing Correctly

Your 3D printer is a finely tuned workhorse able to churn out prints one after another without issue. But then when it comes to a print with fine detail, your printer isn’t producing the results you expect.

Edges and corners that are supposed to be pin sharp and crisp have a defined curve and softness, and intricate details are far from perfect.

What's causing this?

There are several issues that can affect the quality of printing when it comes to fine detail.

The most common cause of low detail prints is, of course, the layer height. If you have a low resolution (high layer height) set for your printer then you’re not going to be able to get silky smooth prints, regardless of how good your printer is.

Nozzle size is another obvious issue. There’s a very delicate balance between nozzle size and fine print quality. In a production environment, a 0.5mm nozzle is ideal. For general purpose, a 0.4mm, and fine detail 0.4mm or smaller.

The smaller nozzle will also mean that your machine will need to be finely tuned as any issues will be amplified.

Nozzle temperature is all important, as your printer needs to be able to extrude the plastic smoothly. When it comes to detail make sure your nozzle is clean prior to starting, even the slightest build-up of filament or a small blockage will highlight in the print.

Print speed will also have a huge effect on the detail; for detailed prints go as slow as you dare. You may have to adjust the fan speed to accommodate the increase in extrusion time. Some printers even benefit from the extruder fan being switched to its lowest setting (or even off).

Filament brands spend a fortune fine tuning their formulas to create a smooth flowing and setting filament. Although cheaper brands might look the same, the tolerances of diameter chemical composition can vary, and this inconsistency will again be highlighted in the final print.

Finally check that the print platform is level. Even the slightest error in the level will have repercussions throughout the print when printing at high resolutions. Finding a good calibration print is an effortless way of checking just how well your printer is tuned.

Solution:

INCREASE THE RESOLUTION
Increase the resolution — a tighter, lower layer height will give successful prints a smoother finish.

NOZZLE DIAMETER
The smaller the nozzle diameter the higher detail you can print. But a small nozzle also means lower tolerances, so your machine needs to be highly tuned.

MAINTAIN YOUR PRINTER
Any additional friction from slightly misaligned rods or loose belts will be instantly apparent in your print. Ensure everything is tight and aligned.

CLEAN YOUR NOZZLE
Before starting a detailed print make sure that your nozzle is clean.

SLOW IT DOWN
Reduce your print speed — a nice slow extrusion is less prone to error.

USE QUALITY FILAMENT
Selecting the right material from a quality filament manufacturer is a key to excellent quality prints.

CHECK PLATFORM LEVEL
Run through your printer’s calibration procedure to check that the platform is level.

Ripples and "Echoes" in Print (Ringing)

The effect of visual waves or rippling on the print surface is one of those minor and annoying problems that many of us simply overlook. It has a habit of coming and going, and there really does seem to be no consistent reason for the issue.

The effect is normally very subtle and appears as a wave or ripple through the surface of the print, it’s position and severity can also change.

Most people will simply overlook the problem. Other than a slight visual effect on the surface the effect of these ripples has little other effect on the quality of the final 3D print, except of course in the most severe of cases.

What's causing this?

The issue of waves in your 3D prints is usually down to one of two things, and more commonly a combination of the two.

Vibrations and speed. 3D print manufacturers do an awful lot to their machines to make sure that the small vibrations created by the motors are kept to an absolute minimum. Lift a printer like the Ultimaker 3 and you’ll see exactly what we mean, even the small Cel Robox Dual packs in some significant weight.

This weight helps to minimize vibrations through the machine but doesn’t eliminate it. Those small vibrations can travel through the furniture, floorboards, or any surface you’ve seen fit to adorn with your printer.

The next time you start your 3D printer up look at the surface that it’s on, then as the printer prints check to see if the table is sturdy enough to properly support the machine.

Vibrations can also be amplified by poor maintenance and worn linear bearings. Regularly check that your printer is clean, free of fluff, grit and dirt, and remember to keep the rails oiled.

When the printer’s off check the quality of the linear bearings and make sure that the movement of the print head is smooth, you can do this by moving the head with your fingers. Make sure everything is cool before you start.

As you’re checking the maintenance make sure that all the bolts and bits within the machine are good and tight, especially if you built the machine yourself.

Waves will also be an issue if you try to print too fast, the simple solution here is to simply drop the print speed, this will solve the problem in many cases.

If you still need to print fast, then try increasing the flow and extrusion temperature.

Finally, and this is one for the more advanced users, and that’s firmware acceleration. This adjusts the speed of the head as it prints and changes direction, its function is to help prevent ringing. Here there are two functions that you should look at and this will change depending on the machine.

Look for acceleration and jerk, there are several values listed, start by lowering the jerk and then the acceleration during printing.

Solution:

REDUCE VIBRATIONS
Make sure that the surface you use for your 3D printer is solid and as the printer prints there are no visual vibrations.

CHECK THE BEARINGS
Linear bearings wear over time, with the printer off check that all are still running smooth.

MAKE SURE EVERYTHING IS TIGHT
It’s amazing how one loose bolt can affect print quality, as part of your maintenance routine make sure everything is bolted and tight.

ADD OIL
Check all the rods are clear of dust and dirt and then add a drop of oil to ensure everything is well lubricated.

SLOW DOWN THE PRINT
Reduce the print speed.

ADJUST THE FIRMWARE ACCELERATION
One for advanced users only, check the printer’s firmware and adjust the values in the code for the acceleration and jerk, you’ll then need to upload the firmware back to your machine.

Scars on Print

Horizontal lines appear across the top layer of your print, usually diagonally from one side to another.

What's causing this?

A 3D print is created by laying down successive layers, one after the other. As each layer is set the print head moves through the X and Y axis. Once the layer is complete the head lifts through the Z-axis and returns to the start point to set down the next layer.

It is at this point that visible lines or scaring can occur. These can be caused by several printer settings, but the problem is due to filament oozing or the nozzle physically scratching the surface.

Combing is one of the major offenders. Combing confines, the print head to the printed area of the model. If there is any excess filament, it oozes across the rest of the print. Alternatively, the head doesn’t lift high enough and the hot nozzle drags across the surface, leaving a scar.

Over extrusion is another less common cause, as the head lifts excess drags across the surface leaving a trace of filament. On larger flat surfaces you may see the diagonal line fade across the surface.

Too high a temperature is a less probable cause but with some cheaper or older filaments the residual heat of the nozzle can lead to filament oozing from the nozzle, again leaving a trail as the nozzle shifts.

Solution:

COMBING
Combing keeps the print head over the already printed areas of the model and therefore reduces the need for retractions. Whilst this increases print speeds it can cause the scaring. Switch combing off and, in most cases, this will clear the problem but expect longer print times.

RETRACTION
If you’ve switched off combing and the issue remains, try increasing the retraction amount. If the problem persists, then look at over-extrusion or the nozzle temperature.

CHECK THE EXTRUSION
How you adjust the flow rate of the filament will vary depending on your printer. Using Cura and the Ultimaker series you’ll find the flow details on the machine in the material settings for the Ultimaker 2, on the Ultimaker 3 you’ll find them in the Custom settings in the Cura software.

Reduce the flow rate by 5% and print a calibration cube to check if the filament is extruding correctly and eliminating the issue.

NOZZLE TEMPERATURE
The tolerance of decent quality filaments should negate the issue in principle, but if your filament has been sitting around for a while, exposed to moisture or sunlight, you may find that the filament’s tolerances to temperature has reduced. Decrease the hot end temperature by 5 ºC and try again.

Z-LIFT
Filament isn’t the only issue; if the head doesn’t lift high enough from the surface of the print, then the nozzle itself can cause the scarring as it travels from one layer to another. On older printers you’ll need to re-calibrate if there are no Z-lift or Z-hop settings, otherwise increase Z-Hop or Z-Lift in 0.25mm increments.

Print Looks Stringy and Droopy (Over-Extrusion)

Over-extrusion means that the printer supplies more material than needed. This results in excess material on the outside of the model printed.

What's causing this?

Typically, the Extrusion multiplier or Flow setting in your slicing software is too high (see the section above)

Solution:

EXTRUSION MULTIPLIER
Open your slicer software and check that you have the correct Extrusion multiplier selected.

FLOW SETTING
If that all looks correct then decrease the Flow setting in your printer’s software.

Print Layers Look Uniformly Thin/Weak (Under-Extrusion)

Under-extrusion is the term given to the printer not supplying sufficient material for the print. Under-extrusion has many telltale signs — most significantly thin layers, unwanted gaps and even missing layers entirely.

What's causing this?

There are several potential causes. First, the diameter of the filament used does not match the diameter set in the slicing software. Secondly, the amount of material that is extruded is too low because of faulty slicer software settings. Alternatively, the flow of the material through the extruder is restricted by dirt in the nozzle.

Solution:

CHECK THE FILAMENT DIAMETER
Start with the simplest issue, have you set the correct filament diameter in the slicing software? If you’re unsure about the diameter the value along with the recommended temperature is usually printed on the box.

MEASURE THE FILAMENT
If you’re still not getting the results, you want and filament flow is the issue, then use a set of calipers to double-check the filament diameter. You should be able to tweak the filament diameter settings accurately in the slicer software settings.

CHECK THE HOT END FOR DEBRIS
After printing, most printers will lift the printhead away from the print base. Quickly check that the nozzle is clear from a build-up of filament and dirt.

SET THE EXTRUSION MULTIPLIER
If there is no mismatch between actual filament diameter and the software setting, then then the extrusion multiplier (also referred to as the flow rate or flow compensation) may be too low. Each slicer application will handle this slightly differently, but the principle is to increase this value in steps of 5% until you see the problem is gone.

Print Looks Melted and Deformed

Filament is surprisingly resilient to all types of misconfigurations, including overheating of the hot end. It’s for this reason of resilience that noticing your hot end is too hot isn’t always as easy as you’d think it would be.

A sign of this can be the appearance of uneven layers; when you take a closer look you can see that it’s not so much uneven as melted. Again, our model shows this subtly on the cabin, and to a far greater effect on the chimney where it starts to look a little like wax running down a melted candle.

Overheating filament can also cause huge issues with accuracy, especially when it comes to threaded holes you have printed. Finding that some holes are correct, and others are too small is often an initial sign that the temperature could be too high.

What's causing this?

Normally, having too hot a hot end or overheating is an easy fix. There needs to be a fine balance between melting the filament so that it will flow, and enabling the filament to solidify quickly so that the next layer can be applied to a solid surface. Before you go adjust the temperature, however, first make sure that you have loaded the correct material settings for your 3D printer (as part of the filament loading process). If you have, then it could be that you need to adjust the temperature just a touch.

Solution:

CHECK THE RECOMMENDED MATERIAL SETTINGS
This might seem obvious, but just double-check that you’ve given the printer the correct details about the material. The latest filament temperatures range from between 180 – 260ºC or thereabout, so it’s surprising how easy it is to get this wrong.

DECREASE HOT END TEMPERATURE
In the printer or software settings decrease the hot end temperature. Depending on the severity of the overheating, drop the temperature in 5ºC intervals.

INCREASE PRINT SPEED
If the filament isn’t being discolored then you could try speeding up the print speed.

ADJUST FANS
Check that the cooling fans are directed at the hot end. Check that they’re in the right position and if possible, boost their speed to increase airflow over the cooling filament.

Pits and Hollows in Top Layer (Pillowing)

The top surface of the print shows unsightly bumps or even holes.

What's causing this?

The two most common causes are improper cooling of the top layer and that the top surface isn’t thick enough.

Solution:

FILAMENT SIZE
Pillowing is an issue that can affect all 3D printers, however, it’s far more common on those using 1.75 mm filament. If none of the other tips below help, try switching to 2.85mm filament if you can.

CHECK THE FAN POSITION
Cooling can be a cause of pillowing. As the print starts your printer’s fans will typically be set to low or off and after the first few layers, they should kick into action. Check that the fans around your hot end start spinning, especially toward the end of the print. If they are functioning fine, then the issue could be that they are not directing sufficient airflow over your print. There are a variety of 3D printable mods to alter your print airflow.

SET FAN SPEED IN G-CODE
Another cooling issue happens when each successive top layer of molten plastic is applied. As it covers the inner support structure it needs to be cooled quickly to avoid falling into the holes between the supports. The speed of the fans can be adjusted in the G-Code.

A common G-Code for Fan On is M106 and is M107 Fan Off. By those control lines, you just need to set the Fan speed to maximum for those top layers.

For example, looking at the G-Code (generated in Cura for printing on a Prusa i3) for a 1cm x 1cm cube printed at 0.1mm layer height, we can see that there are 97 layers. Knowing that we have a ‘Bottom / Top Thickness setting’ of 0.6mm we can look back to; LAYER:91, then in the subsequent line add M106 S255. M106 sets the fan going and S255 sets it to full blast.

INCREASE TOP LAYER THICKNESS
The easiest solution is to increase the top layer thickness. Most applications will enable you to do this in the advanced section, under the ‘Bottom / Top Thickness setting’. You’re aiming for at least 6 layers of material normally and up to 8 for smaller nozzles and filaments. If your layer height is therefore set to 0.1mm then set the ‘Bottom / Top Thickness setting’ to 0.6mm. If the effect of pillowing still exists, then bump it up to 0.8mm.

Web-like Strings Cover the Print (Stringing)

There are unsightly strings of plastic between parts of the model.

What's causing this?

When the print head moves over an open area (also known as travel move), some filament has dripped from the nozzle.

Solution:

ENABLE RETRACTION
Retraction is a crucial factor when it comes to quality of finish and can be enabled through most slicing software. Its function is simple and works by retracting the filament back into the nozzle before the head moves. The idea is that it avoids molten filament from trailing behind the head creating thin strings in its wake.

Most applications such as Cura offer a one-click activation option. This uses a set of default parameters and is perfectly adequate, but for fine-tuning there are customizable options that give greater control. Adjusting the minimum travel of the head before retraction is activated, for example.

MINIMUM TRAVEL (MM)
Reducing the minimum travel is usually the quickest fix for stringing if the standard retraction isn’t doing the job. Drop the value in 0.5mm increments until the stringing has stopped.

JUST CUT THEM OFF
This isn’t the most elegant of solutions but simply taking a scalpel to the strings is quite often the quickest and easiest solution.

Print Has Lost Dimensional Accuracy

When you’re designing a product in your CAD application, the dimensions you’ve painstakingly planned need to be perfectly reproduced by your 3D Printer.

However, when it comes to bolting your product together, you find that all that accurate measurement and design has gone to pot. Nothing aligns, the holes are the wrong size, and nothing fits.

Print dimension accuracy is one of the few areas of 3D printing where it’s highly likely that your printer is fine. Before checking the printer for faults, double-check that the dimensions of the 3D model are correct.

With that done, then you can look to the printer to find the cause.

What's causing this?

Let’s start with the measurements and the most frequent problem. First, check that you’re working in real-world measurements; cm and mm are best, although inches are also a workable unit for 3D printing. Mix the two up between your 3D model and slicing engine, and you’ll quickly spot the error.

If all is fine with the unit selection, then double-check the physical measurements of the parts. When it comes to measuring, always measure twice!

Now if you have separate prints that need to fit together, such as a male-to-female connector, or screw and hole, then make sure the insert is slightly smaller than the hole you’ve created for it.

For example, if you have an M5 screw and you’ve created a 5mm diameter hole for it to go in, then it’s not going to fit (at least not without some muscle and determination). To solve this, increase the hole size by 0.1mm for a fine print and 0.2mm for a low-quality print. Print and try again. If it still doesn’t fit enlarge it a little more.

If the hole looks oval, the issue is not necessarily the hole’s size.

If you’ve created a low polygon shape, then the likelihood is that your hole is no longer round and instead has slightly straightened edges. When printing an object with holes, always ensure you keep a moderate polygon count to keep those smooth round holes for things to fit in.

The same goes for custom shapes that need to fit together. Reducing the polygon count of one object can cause all sorts of issues if the two sections have rounded edges that need to interconnect.

Once you’ve finished checking everything with the model’s dimensions, it’s time to turn your attention to the printer. The first few layers are all important when it comes to print accuracy. Print out a test cube 50mm x 50mm and use digital calipers to check the measurements; make sure you print the cube at the same layer height you’ll be printing your final model. Firstly, check the overall height to see if it equals 50mm, if it does then all is fine on the Z-axis. If not, then carefully measure the top 20 layers — these should equal 20mm. If this is correct but the overall height is wrong, then it’s likely that the first few layers are causing the issue.

To resolve this, check the height of the nozzle from the print platform and that it’s within the margin of error for your printer in relation to the layer height. If your nozzle height is 1mm from the print platform and your layer height is 2mm, you may find too much filament is being laid down in that first layer and causing the issue. If this is the case, either recalibrate your printer and ensure the nozzle to platform distance is increased or reduce the layer height.

Now check the X and Y dimensions. If they’re approximately 1mm smaller than they should be, but all proportions look correct, it could be due to filament thermal contraction. This is common with ABS; to correct this, work out the percentage of error and increase the scale of the print to compensate. Using high-quality filaments is the best way to avoid this.

Back to the hole and have a look inside; if the walls look smooth then everything is ok. If you see the layers protruding slightly then this could be a sign that the nozzle is too hot, and the filament is oozing after it’s been laid down.

If the hole looks oval, then it could be that one of your belts is loose or there is a slight misalignment of the X- and Y- axes. Check all are tight, and everything screwed into place as should be.

Solution:

CHECK WORKING UNIT OF MEASUREMENT
In your 3D printing application make sure you have the correct real-world dimensions selected.

DOUBLE-CHECK THE MEASUREMENTS
If you’re designing a part that needs to connect with other objects, double-check your measurements and use a digital caliper.

OVER-SCALE SCREW HOLES
If you’re making a screw hole, create a virtual 3D M5 screw with a diameter slightly larger than it should be and use this to extract/create a Boolean subtraction from the model you need the hole to appear in.

INCREASE POLYGON COUNT
Reducing the polygon count of your models can cause issues with the slightly flattened edges. Make sure you keep polygons within a reasonable count for smoother gradients and better fits.

TEST PRINTER ACCURACY WITH TEST CUBE
Use a 3D Print Calibration Cube to check the X, Y, and Z dimensions of your print.

CHECK NOZZLE TEMPERATURE
Try reducing your print temperature if there are blobs and other stray extrusions on the inside of your print’s holes.

CHECK BELTS AND RAILS
Check over the belt tension and make sure all axes are straight and correctly aligned.

Print Offset in Some Places

The lower and top layers shift so that you get a stepping effect through the print. Usually, it’s quite subtle, but the image below shows a print with a more pronounced effect.

What's causing this?

There’s a variety of reasons for shifting layers, and these can be as simple as someone knocking against the printer during the print process. More complex causes can be bent or misaligned rods, or even the nozzle catching on the print and causing a slight shift in platform position.

Solution:

CHECK THE PRINTER HAS A STABLE BASE
Place the printer on a stable base and in a location where it will avoid being knocked, poked, and fiddled with. Even a small nudge of the printer can shift the print base and cause issues.

CHECK THE PRINT BED IS SECURE
Many 3D printers use some form of detachable print bed. Although this is handy when it comes to removing prints and avoids damage to the printer, it also means that over time clips and screws can work loose. Make sure that when you reinstall the print platform it’s clipped or bolted tightly in place to avoid any slip or movement.

WATCH FOR WARPED UPPER LAYERS
A print’s upper layers can easily warp if cooled too quickly. As the layers warp, they rise and can cause an obstruction to the nozzle as it moves. In most cases the print will release from the platform, but if it doesn’t the powerful stepper motors can push the print and platform around. If your prints are suffering from warping in the upper layers, try reducing the speed of the fans slightly.

REDUCE PRINT SPEED
It is possible to speed up the print times for your machine by increasing temperature and flow. However, whilst this may result in the filament flowing in the correct quality the rest of the machine may struggle to keep up. If you hear a clicking during printing this could be a sign that the printer is going to fast. If you do hear a click the first port of call is to check that the filament isn’t slipping, before you look at the actual printer speed. You can adjust your printer’s speed easily enough in any good slicing software.

CHECK THE BELTS
If layers are still shifting, then it’s time to check the belts. A quick check is to just go around all belts and pinch the two together. The tension in each belt should be the same, if not then you’ll need to adjust the belt position to even out the belt tension. Over time the rubber belts will stretch (You can often tell if they do as they’ll start to slip on the drive pulleys), if there is quite a bit of play in the belts then it’s time to replace them with new ones. Over tight belts can also be an issue, but this is usually only a problem if you’ve built the machine yourself. Some printers such as the Prusa i3 have belt tensioning screws that enable you to easily adjust the belt tensions.

CHECK THE DRIVE COUPLERS
These are usually connected directly to a stepper motor, and one of the main rods that drives the print head. If you carefully rotate the coupler, you’ll see a small grub screw. Hold onto the rod and taking hold of the attached belt and then tug the belt and try to force the pulley to turn. You should find that there is no slip between the coupler and stepper or rod. If there is, tighten the grub screw and try again.

CLEAN AND OIL THE RODS
Over time debris can build up on the rods which means that at some points along their length they encounter an increase in friction. This can affect the free movement of the head and cause layer shifting. A quick wipe and re-oil of the rods usually solves the issue.

CHECK FOR DEFORMED RODS
If you see the print head falter at certain points, then it could be that one of the rods has become slightly bent. You can usually tell by switching off the machine so there’s no power going through the steppers and then move the print head through the X- and Y- axes. If you feel resistance, then you know something is amiss. Start by seeing if the rods are aligned, if they are then removing the rods and roll them on a flat surface. If any are bent, then it will be obvious.

Bridges are Messy

Bridges are a stretch of plastic that is extruded between two raised points. If you have two columns with a 5 cm gap, then the beam that sits on top between those two points with nothing below is the bridge.

Most filament is surprisingly resilient to bridging, and with a finely tuned printer the distance achievable when bridging can be surprising. However, you know something isn’t quite right when your printer starts to fail to bridge even the smallest gap.

The most obvious sign is when the printer fails to successfully bridge gaps between 1 and 3 cm. The extrusion may be too thin, filament sags, or simply flows down the height of the bridge rather than across.

What's causing this?

Finding the underlying cause of bridging issues is typically easy and much of the diagnosis comes through the look of the failed bridge.

It’s also worth noting that the way that different slicer applications handle bridging is quite different, with applications such as Simplify3D having a special Bridge option that will adjust extrusion and cooling for the best results.

The most common related issue is that the gap you’re trying to bridge is just too big, this distance will vary with each printer and material. You can usually tell if the gap is too great as the filament will start to sag in the middle or collapse.

Cooling is another major issue; the filament needs to be cooled quickly for it to be able to support itself between the two columns.

Extrusion speed is equally important, if the print head moves too quickly then the speed and vibrations will inevitably cause instability before the filament has set.

Too high extrusion temperature will often result in bridging, again showing sagging of the filament. If the extruded filament is of different thicknesses, then you know this is the issue.

Solution:

CHECK THE BRIDGING CAPABILITIES
You can make a test print with columns and bridges of different distances to check how far your printer will go, start with a 5cm gap, and then increase, anything between 5 and 10 is good, 15 would be exceptional.

ADD SUPPORTS
A quick and easy fix is to simply add supports below the structure

INCREASE FAN SPEEDS
Boost the extrusion fan speed to ensure that the filament cools quickly, the faster the filament sets the larger the bridge it will be able to create.

DECREASE EXTRUSION SPEED
Fast extrusion is an absolute no when it comes to bridging, you need slow and steady as the filament needs to have time to set as the distance is bridged.

USE SIMPLIFY3D
This dedicated 3D print software features a bridging option and will automatically recognize any areas of your print that require greater cooling and slower extrusion speed

Print is Stuck to Print Bed

Prints welded to the print platform are as common as prints not sticking at all. Annoyingly quite often you’ll experience both issues in one day, and usually by solving one you create the other.

The main fix to this 3D print issue is balance.

Spotting the problem is simple. Once the print has finished it just won’t budge. In fact, it’s welded so firmly you could lift the weight of the printer by the print (tempting as it may be, don’t).

What's causing this?

When the filament is warm it’s designed to be tacky so that as each layer is extruded it will stick together. As the print base is warm the filament that makes contact will remain slightly tacky until completely cool.

A print with a large surface area that’s in direct contact with the base can be plain stubborn to remove. It really does just bond with a suction-like effect.

Old print platforms can become overly textured with layers of glue or small pits in the glass acting as anchors to the print. Over time this texture can create an almost unbreakable bond. Some print platforms are perforated by design, and typically they give the most difficult to remove prints.

Cheap filament can also be the culprit for a ridiculous print bed bond. Although the filament melts fine, it doesn’t always solidify completely.

Solution:

HAVE A LITTLE PATIENCE
You’ve waited hours for the print, so waiting a little longer for the print to cool down completely isn’t going to hurt. After some cooling time, it may release of its own accord. As the filament cools it solidifies, losing the tackiness that is needed for the layers to bond.

USE A PALETTE KNIFE
Many 3D printers come with them, but you can find one at any decent hardware store. If you’ve left it for an hour and the print is still stuck firm, release the build plate from the machine and place it onto a desk with something to support the print base from behind. Ideally a wall. Then carefully use the knife to work around the edge and prize the print free.

GIVE THE PRINT PLATFORM A CLEAN
It may not help with the present print, but if your print platform is clogged with glue then it’s time to give it a clean. Future prints may not exhibit the same unbreakable bond. If the print is still attached run it under hot (not boiling) water and gently use a palette knife to scrape off any surface glue. Leaving it to soak in hot water will release the print as well but take care to only apply this tip to removable print bed surfaces.

After the print releases, make sure the platform is cleaned and inspected for any pits in the glass. If there are then flip the glass over and use the smooth side. If both sides show signs of pitting buy a new one.

STICK IT IN THE OVEN
There are times when hot water just won’t budge a print, if you have a glass or other heat-resistant platform with no plastic or electronics attached and it’s possible to remove it from the printer, pop it in the oven. Set the temperature to 100º and then use a pallet knife to see if you can move the print. If not increase to 120º and leave for five minutes and try again. Increase the temperature until you have removed the print, or the print has melted and can be scraped away (ensure you wear heat-proof gloves). The latter extreme will be at the expense of sacrificing your print.

DON’T USE CHEAP FILAMENT
On so many levels cheap filament is a false economy. It can bond to your print platform in ways that no other material known to man can and is perfectly suited to welding printheads and extruders together once cooled. The only tangible way to avoid the issue is to completely avoid cheap filaments.

MAKE SOME HOLES
This requires a little foresight, but by creating a few holes in the design of the print base you can avoid some sticking caused by too much surface contact and suction.