16 Common 3D Printing Problems and Solutions

3D printing is usually a great deal of fun, but it can also be a massive source of rage and frustration. You know that feeling; try as you might, that gosh-darned 3D print won’t turn out right. Why does it keep going wrong?

ALL3DP to the rescue with our comprehensive 3D printing troubleshooting guide. We’ve detailed the 16 most common 3D printing problems, so you can quickly diagnose the issue you’re experiencing, together with a series of recommended solutions.

Read how and when these 3D printing problems occur, and the steps you can take to avoid them in future.

3D Printing Problems #1: Warping

Warping: The front corner of this pyramid has lifted up.

What’s the problem? 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.

What’s the cause? Warping is a common 3D printing problem, which happens when the first layers of heated plastic are cooling down too rapidly and begun to contract. This causes the edges of the model to bend upwards.

3D printing troubleshooting:

1. Use a heated print bed to keep the plastic at a temperature just below the point where it gets solid. This is called the “glass transition temperature”. This way, the first layer will stay flat on the print bed.
2. Increase adhesion of the first layer to the print bed by spreading a tiny film of glue evenly on the bed.
3. Make sure the level of the print bed has been calibrated properly.
4. You may consider adding a raft or pads to increase platform adhesion.
5. Another option is to tweak the cooling fan, so it doesn’t get switched on until after a certain number of layers have been printed, or adjust the percentage so it’s not operating at full power.

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

3D Printing Problems #2: Elephant Foot

Unsightly bulges at the base.

What’s the problem? The base of the model is slightly bulging outwards, otherwise known as “elephant foot”

What’s the cause? This ungainly effect can also be caused by the weight of the rest of the model pressing down the first layers, when the lower layers haven’t had time to cool back into a solid – particularly when your printer has a heated bed.

3D printing troubleshooting: It’s tricky to find the right balance between getting rid of warping and avoiding the elephant foot effect. To minimize bulges at the base of your model, we recommend leveling the printer bed and moving the nozzle a little further away from the bed (but not too far, otherwise the print won’t stick). Additionally, lower the bed temperature slightly.

If you’ve create the 3D model yourself, put a small chamfer at the bottom of the model. Start with a 5mm and 45º chamfer, and experiment to get the best result.

3D Printing Problems #3: More First Layer Problems

Warping because of the small footprint (left); Uneven first layer (right)

What’s the problem?

• The first layer does not stick properly, and some parts come loose.
• There are unwanted lines at the bottom.

What’s the cause? 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.

Also important: the print bed has to be as clean as possible. Fingerprints on the plate can prevent the first layer from sticking to the plate.

3D printing troubleshooting:

1. Use your printer software to re-level the print bed.
2. Clean the bed of fingerprints.
3. Apply a fine film of glue before printing.

3D Printing Problems #4: Lower Parts Shrink

What’s the problem? The lower part of the model caves in.

What’s the cause? This happens when the temperature of the heat bed is too high.

Plastic being heated and extruded behaves like a rubber band. First it expands, and when cooling down it shrinks. The heat from the bed only rises to a certain height (depending on the temperature). Up to this height, the extruded plastic stays warm – and malleable – longer than the plastic layers above the height. This way it may yield under the weight of the upper layers and cave in.

3D printing troubleshooting: A simple tactic here is to reduce the bed heat. In some printers the default bed temperature is 75ºC, whereas the recommended temperature for PLA is 50 – 60ºC. Additionally, set the fan in the printer to fully blow at the lowest height.

When printing small models, we recommend you print two copies or two different objects. This way the print head will take more time to print one layer after the other.

When printing models with a large footprint, do not reduce bed temperature too much — otherwise the edges may warp.

3D Printing Problems #5: Skewed Prints / Shifted Layers / Leaning

Shifted layers in Fred Kahl’s “3D printer hangover”

What’s the problem? The upper layers are shifted.

What’s the cause? This is a mechanical fault with the printer, either because:

• The head does not move easily on the X or Y rods.
• The rods are not aligned correctly, i.e., they are not 100% square.
• One of the pulleys is not fixed properly to the axis.

3D printing troubleshooting:

1. Turn the printer off and check whether you can move the head easily along the rods with your hands. If the head moves stiffly or it moves more easily in one direction, apply a drop of machine oil to the rod.
2. To see if the rods are correctly aligned, move the head to the left and the right side of the printer and check that the distance between the sliding blocks and the pulleys are equal on both sides. Repeat this for the front/back of the printer. If you notice misalignment, loosen the screws on the two pulleys of the rod in question. Nudge the sliding block a bit until the rod is aligned again, then tighten the screws. Repeat for the other rod.
3. Check to see if the screws that hold the pulleys in place are secure, and tighten them if necessary.

3D Printing Problems #6: Layer Misalignment

Flawed layer alignment.

What’s the problem? Some layers in the middle of the objects have shifted.

What’s the cause?

• The printer belts aren’t well tightened.
• The top plate isn’t fastened and wobbles around independent of the bottom plate.
• One of the rods in the Z axis is not perfectly straight.

3D printing troubleshooting:

1. Check the belts and re-tighten them, if necessary.
2. Check the top plate and fasten it, if necessary.
3. Check the Z axis rods and replace them if they’re not 100% straight.

3D Printing Problems #7: Missing Layers

What’s the problem? There are gaps in the model, because some layers have been skipped (in part or completely).

What’s the cause?

• The printer failed to provide the amount of plastic required for printing the skipped layers. This is called (temporary) under-extrusion. There may have been a problem with the filament (e.g. the diameter varies), the filament spool, the feeder wheel or a clogged nozzle.
• 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.
• There is a problem with one of the Z axis rods or bearings. The rod could be distorted, dirty or had been oiled excessively.

3D printing troubleshooting:

1. Check the rods and bearings for problems and fix them. If there is too much oil, for example, remove it.
2. If you suspect misalignment of rods and bearings, consult your printer’s documentation to see how to correct it.
3. Finding the cause for under-extrusion is more cumbersome.

3D Printing Problems #8: Cracks In Tall Objects

What’s the problem? There are cracks on the sides, especially on taller models.

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

3D printing troubleshooting: Increase the extruder temperature; a good start would be to increase it by 10ºC. Also experiment with increasing the bed temperature by 5 – 10ºC.

3D Printing Problems #9: Pillowing

Pillowing: The top surface shows bumps and/or holes.

What’s the problem? The top surface shows unsightly bumps or even holes.

What’s the cause?

• The typical cause is improper cooling.
• The top surface is not thick enough.

3D printing troubleshooting:

1. Set the cooling fans to top speed when the top surfaces are printed.
2. Make sure the top surfaces are at least 6 layers thick.

3D Printing Problems #10: Stringing

Stringing: Unwanted strings of plastic between the parts of the object.

What’s the problem? There are unsightly strings of plastic between parts of the model.

What’s the cause? When the print head moves over an open area (otherwise known as travel move), some filament has dripped from the nozzle.

3D printing troubleshooting: Most printers have a feature called retraction. When retraction has been enabled, the printer retracts the filament in the nozzle before a travel move. This way, no surplus plastic can drip from the nozzle and produce strings. Make sure you enable retraction in the slicing software for your printer, but be aware that this can prolong the time required to print an object.

3D Printing Problems #11: Under-extrusion

What’s the problem? Under-extrusion is when the printer cannot supply the material needed (or as fast as needed). Under-extrusion results in thin layers, in layers with unwanted gaps, or in missing layers entirely.

What’s the cause? There are several possible causes:

• The diameter of the filament used does not match the diameter set in the slicing software.
• The amount of material that is extruded is too low because of faulty slicer software settings.
• The flow of the material through the extruder is restricted by dirt in the nozzle.

3D printing troubleshooting:

In Simplify3D, you set the filament diameter in the Edit Process Settings dialog.

1. Check the filament diameter and the diameter setting in the slicing software – correct the software setting, if necessary. The filament diameter is printed on the spool or on the package: if not, measure it using calipers.
2. If there is no mismatch between actual filament diameter and the software setting, the extrusion multiplier (or flow rate or flow compensation) setting may be too low. Increase the setting in 5% steps and restart printing. In Simplify3D open the Edit Process Settings dialog and go to the Extruder tab – the Extrusion multiplier setting of1.0 corresponds to 100%; in Cura open the Material tab and increase the Flow setting (you may need to enable the Flow setting through the Preferences dialog).
3. Check to see if there is a partial blockage in the nozzle and remove it.

3D Printing Problems #12: Over-extrusion

What’s the problem? 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 the cause? Typically, the Extrusion multiplier or Flow setting in your slicing software is too high (see the section above)

3D printing troubleshooting: Correct the Extrusion multiplier or Flow setting in your printer’s software.

A Flow setting way over 100% in Cura may result in over-extrusion; the Flow setting (right) is only visible when you check the Flow option in the Preferences (left).

3D Printing Problems #13: Gaps in the Top Layers

What’s the problem? There are holes or gaps in the top layers.

What’s the cause? To save print material and to speed printing, the interior of a model is not printed 100% solid. Instead, some kind of infill is printed, typically only 30% of the material, the rest of the model remains hollow. Only the top layers (and the walls and the bottom) are printed 100% solid. The are gaps in the top layers can have these causes:

• There are too few solid top layers.
• The infill percentage (for the interior) is too low.
• Underextrusion (see 3D Printing Problems #11).

3D printing troubleshooting:

1. The first corrective measure when you notice holes or gaps in the top surface: Increase the number of solid top layers in the slicing software. There should be at least 0.5mm of solid layers (how many layers that means depends on the layer height). The additional solid top layers do not add height to your printed model. When you increase the number from 3 to 5, for example, the last 5 layers are printed solid (instead of 3).
   In Simplify3D, you increase the number of solid layers on the Layer tab in the Edit Process Settings dialog. In Cura, use the Shell Thickness setting on the Quality tab to increase the solid top layers (plus the solid bottom layers and the outside walls).
2. When the hollow gaps in the model are too wide, because the infill percentage is only – say – 10 or 20% – the solid layers may sag. If adding more solid top layers does not correct the problem, increase the infill percentage in the slicing software. This will increase the filament consumption.
   In Simplify3D, the infill options are found on the Infill tab in the Edit Process Settings dialog. In Cura, you’ll find the Infill Density setting on the Infill tab.
3. To correct underextrusion.

3D Printing Problems #14: Visible Lines in the Bottom Layers

What’s the problem? The bottom layers have visible lines.

What’s the cause? The gap between the nozzle and the print bed is too wide.

3D printing troubleshooting:

In Cura, you can increase the thickness of outer walls and the top and bottom layers.

1. Make sure your print bed is leveled correctly.
2. Reduce the height of the very first layer – depending on your printer and the filament used, you may go down to 0.1mm (this, however, requires that the print bed is absolutely level).

How to level the print bed and adjust the gap between the nozzle and the print-bed.

3D Printing Problems #15: Scars on the Top Surface

What looks like scratches is in fact oozing of the filament when the printhead travelled over the piece.

What’s the problem? There are visible scratches and scars on the top surface of the model.

What’s the cause? The marks are caused by the nozzle that moved across the top surface.

• They are actual scratches as the nozzle scrapes over the surface.
• These marks are plastic oozing caused when the nozzle traveled across the surface (but did not touch the surface).

3D printing troubleshooting:

For the example above the, the Retraction Vertical Lift value in Simplify3D was too low.

1. To avoid scratches and reduce oozing: Increase the vertical lift (or Z-hop) setting for your printer. This setting controls how far the nozzle is lifted up above the last layer printed when travelling (without printing). In Simplify3D, you change this setting on Extruder tab of the Edit Process Settings dialog; make sure the Retraction option is enabled and increase the Retraction Vertical Lift setting. In Cura, set Enable Retraction and Retraction Distance (in the Preferences dialog) and increase the Retraction Distance value on the Material tab.
2. To reduce oozing more, force the printer to do a retraction before a travel move. In Simplify3D, disable the Only retract when crossing open spaces and Minimum travel for retraction options on the Advanced tab on the Edit Process settings dialog. In Cura, set the Minimum Travel Distance to 1 and Minimum Extrusion to 0. Please note that this will increase print time.

3D Printing Problems #16: No Filament Comes Out of the Nozzle

What’s the problem? The print bed is empty! There’s no filament coming out of the print-head.

What’s the cause?

• The nozzle is clogged by carbonized material from previous print processes.
• There is a problem with the feeder. The feeder motor may be defective, the pressure the feeder puts on the filament is too low or the filament has ground.

3D printing troubleshooting:

1. If the nozzle is clogged, clean it according to the printer manufacturer’s instructions.
2. If the motor is defective, have it replaced. Consult the printer’s documentation to see how and where to change the pressure settings – and check whether the settings are correct. If the filament has ground down, replace it.

(All images are copyright their respective owners.)

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