10 Ways How to Fix Bulging on 3D Prints – First Layer & Corners


3D prints can experience bulging, especially at the first layer and top layer which can mess up the quality of your models. I decided to write an article detailing how to fix these bulges in your 3D prints.

To fix bulging in your 3D prints, you should make sure your print bed is properly leveled and cleaned up. Many people have fixed their bulging issues by calibrating the e-steps/mm to extrude filament accurately. Setting the right bed temperature can help as well since it improves bed adhesion and first layers.

Keep on reading for more information on fixing these bulges in your 3D prints.

What Causes Bulging on 3D Prints?

Bulging on 3D prints includes blobs on corners, bulging corners, or rounded corners. It is a situation where the 3D print doesn’t have sharp corners instead they look like they are deformed or not printed properly.

This usually happens to the very first or a few initial layers of the model. However, the problem can also occur at any other stage. Many reasons can be a cause of this issue while some of the major causes behind the bulging on your 3D prints include:

  • A bed that isn’t leveled properly
  • Your nozzle being too close to the bed
  • Extruder steps not calibrated
  • Bed temperature not optimal
  • Printing speed too high
  • 3D printer frame not aligned

How to Fix Bulging on 3D Prints – First Layers & Corners

The issue of bulging can be resolved by adjusting different settings ranging from bed temperature to print speed and flow rate to the cooling system. One thing is satisfying as you don’t need any additional tools or don’t have to follow any hard procedures to get this job done.

Below are all the fixes briefly discussed while including the actual users’ experiences with bulging and how they get rid of this issue.

  1. Level your print bed & clean it
  2. Calibrate extruder steps
  3. Adjust the nozzle (Z-Offset)
  4. Set right bed temperature
  5. Enable hotend PID
  6. Increase the first layer height
  7. Loosen Z-stepper mount screws & leadscrew nut screws
  8. Correctly align your Z-axis
  9. Lower print speed & remove minimum layer time
  10. 3D print and install a motor mount

1. Level Your Print Bed & Clean It

One of the best ways to resolve bulging issues is to ensure that your print bed is leveled properly. When your 3D printer’s bed isn’t level properly, your filament won’t be extruded evenly on the bed which can lead to issues of bulging and rounded corners.

You also want to make sure there isn’t any dirt or residue on the surface which can negatively affect adhesion. You can use isopropyl alcohol and a soft cloth to clean up dirt, or even scrape it off with your metal scraper.

Check out the video below by CHEP that shows you the simple way to level your bed properly.

Here is a video by CHEP that will guide you through the whole bed leveling procedure in a manual way.

One user who has been 3D printing for years claims that many issues that people experience such as bulging, warping and prints not sticking to the bed are mostly caused by an uneven print bed.

He experienced bulging in some of his 3D prints but after going through the bed leveling process, he stopped facing bulging issues. He also suggested that cleaning should be considered an integral thing to do before printing a new model.

The video below shows bulging in the second layer of his models. It would be a good idea for him to make sure the bed is level and cleaned up properly.

What could be causing the bulges and un even surfaces? First layers were perfect but after the second layer there seems to be a lot of bulging and rough surface causing the nozzle to drag through it? Any help appreciated. from ender3

2. Calibrate Extruder Steps

Bulging in your 3D prints can also be caused by an extruder that hasn’t been properly calibrated. You should calibrate your extruder steps to make sure you aren’t under extruding or over extruding filament during the printing process.

When your 3D printer is in action, there are commands that tell the 3D printer to move the extruder a certain distance. If the command is to move 100mm of filament, it should extrude that amount, but an extruder that isn’t calibrated will be above or below the 100mm.

You can follow the video below to properly calibrate your extruder steps to get higher quality prints and to avoid these bulging issues. He explains the issue and takes you through the steps in a simple manner. You’ll want to get yourself a pair of Digital Calipers from Amazon to do this.

One user who faced issues with bulging in his 3D prints initially tried to decrease his flow rate by a significant amount which isn’t advised. After he learned about calibrating his extruder steps/mm, he only adjusted the flow rate by 5% to print his model successfully.

You can see the bulging first layers below.

Bulging first layers :/ from FixMyPrint

3. Adjust the Nozzle (Z-Offset)

A great way to tackle the bulging issue is to set the nozzle height at a perfect position using Z-Offset. If the nozzle is too close to the print bed, it will press the filament too much which results in the first layer having extra width or bulging out of its original shape.

Slightly adjusting the nozzle height can efficiently resolve the bulging issues in many cases. According to 3D printer hobbyists, a rule of thumb to set the nozzle height as one-fourth of the nozzle diameter.

That means if you are printing with a 0.4mm nozzle, a 0.1mm height from the nozzle to the bed would be appropriate for the first layer, though you can play around with similar heights until your 3D prints are free from the bulging issue.

One user solved his bulging problems by having his nozzle be the optimal height from the print bed.

Check out the video below by TheFirstLayer that guides you on how to easily make Z-Offset adjustments on your 3D printer.

4. Set Right Bed Temperature

Some people have fixed their bulging issues by setting the right temperature on their print bed. The wrong bed temperature on your 3D printer can cause issues such as bulging, warping, and other 3D printing problems.

I’d recommend following your filament’s bed temperature range which should be stated on the filament spool or the box it came in. You can simply adjust your bed temperature in 5-10°C increments to find the ideal temperature and to see if the problem gets resolved.

A few users did mention that it worked for them since the first layer can expand and takes a longer time to cool down. Before the first layer cools down and gets solid, the second layer gets extruded on top which puts extra pressure on the first layer, leading to the bulging effect.

5. Enable Hotend PID

Enabling your hotend PID is one way to fix bulging layers in 3D prints. Hotend PID is a temperature control setting which give instructions to your 3D printer to automatically adjust temperature. Some temperature control methods don’t work effectively, but hotend PID is more accurate.

Check out the video below by BV3D on PID auto-tuning a 3D printer. Many users have mentioned how easy it is to follow and the terms are explained well.

One user who was getting bulging layers on their 3D prints found that enabling hotend PID solved their issue. This issue does look like something called banding due to how the layers look like they are bands.

They were printing with a filament called Colorfabb Ngen at 230°C but were getting these weird layers as shown below. After trying many fixes, they ended up solving it by doing the PID tuning.

View post on imgur.com

6. Increase the First Layer Height

Increasing the first layer height is another good way to resolve bulging because it will help in better layer adhesion to the print bed which will directly lead to no warping and bulging.

How to Fix Bulging on 3D Prints - Increase Initial Layer Height - 3D Printerly

The reason this works is that you bring about better adhesion in your 3D prints which reduces the chances of experiencing the bulging effect in your models. I’d recommend increasing your Initial Layer Height by 10-30% of your Layer Height and seeing if it works.

Trial and error is important with 3D printing so try out some different values.

7. Loosen Z Stepper Mount Screws & Leadscrew Nut Screws

One user figured out that loosening his Z stepper mount screws & leadscrew nut screws helped to fix bulges in his 3D prints. These bulges were happening at the same layers in multiple prints so it was likely to be a mechanical issue.

You should loosen these screws to the point that there is a little bit of slop in it so it doesn’t end up binding the other parts with it.

When you unplug your Z-stepper and fully loosen up the bottom motor screw of the coupler, the X-gantry should freely fall down if everything is properly aligned. If not, that means things aren’t freely moving and there’s friction happening.

The coupler spins on top of the motor shaft and only does this when things are properly aligned or it will grab the shaft and possible spin the motor as well. Give this fix of loosening up the screws a go and see if it fixes your issues of bulges in your 3D models.

8. Correctly Align Your Z-Axis

You could be experiencing bulges on the corners or first/top layers of your 3D print due to a bad alignment of your Z-axis. This is another mechanical issue that can plague the quality of your 3D prints.

Many users found that 3D printing a Z-Axis Alignment Correction model helped with their Ender 3 alignment issues. You have to correct the bend in the carriage bracket.

It required a hammer to bend the bracket back into place.

Some Ender 3 machines had carriage brackets that were improperly bent at the factory which caused this issue. If this is your issue, then correctly aligning your Z-axis will be the fix.

9. Lower Print Speed & Remove Minimum Layer Time

Another method to resolve your bulging issues is a mixture of lowering your printing speed and removing the Minimum Layer Time in your slicer settings by setting it to 0. One user that 3D printed an XYZ calibration cube found that he experienced bulges in the model.

After reducing his Print Speed and removing the Minimum Layer Time he solved his issue of bulging in 3D prints. In terms of the printing speed, he slowed down the speed of perimeters or walls to 30mm/s. You can see the difference in the image below.

View post on imgur.com

Printing at higher speeds leads to a higher level of pressure in the nozzle, which can result in extra filament being extruded on the corners and edges of your prints.

When you decrease your printing speed, it can help to resolve bulging issues.

Some users have fixed their issues of bulging in 3D prints by reducing their print speed by about 50% for the initial layers. Cura has a default Initial Layer Speed of just 20mm/s so that should work just fine.

10. 3D Print and Install a Motor Mount

It might be that your motor is giving you issues and is causing bulges on your 3D prints. Some users mentioned how they ended up fixing their issue by 3D printing and installing a new motor mount.

One specific example is the Ender 3 Adjustable Z Stepper Mount from Thingiverse. It’s a good idea to 3D print this with a higher temperature material like PETG since the stepper motors can get hot for a material like PLA.

Another user said he had the same issue with bulges on his models and ended up fixing it by 3D printing a new Z-motor bracket that has a spacer. He 3D printed this Adjustable Ender Z-Axis Motor Mount from Thingiverse for his Ender 3 and it worked great.

After trying these fixes on your 3D printer, you should hopefully be able to clear up your issue of bulging on the first layers, top layers or corners of your 3D prints.

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