3D Printing Blobs and Zits: How to Avoid Them

Benchy Blob 2

3D printing has taken the world by storm. Everyone wants to get their hands on a printer for creative and useful purposes. But whether you’re a newbie in need of help or a printing veteran who wants to improve the quality of their work, zits and blobs have got to go!

3D printing zits and blobs are small to medium-sized imperfections that form from incorrect measurements and other malfunctions. You can avoid them by making a few simple adjustments that don’t take too long at all.

The rest of this article will cover some essential topics related to removing zits and blobs:

  • What are zits and blobs?
  • How to prevent zits and blobs when 3D printing
  • 3D printing troubleshooting tips

What Are 3D Printing Zits and Blobs?

3D printers are impressive inventions that allow us to make tools and other items at home. However, they come with a decent learning curve that can turn beginners away from them. Unfortunately, there’s such a massive potential right around the curve that many people don’t end up getting used to.

Finding a zit or a blob on your printed items could mean one of two things: 

  • The 3D printer made an error
  • You made a user error 

These blobs can look hideous or unsightly compared to the creation that you’ve made. It can be discouraging to see them after spending so much time on the design. Fortunately, they’re not too hard to fix in most situations.

When excess plastic builds up, it can leave divots and bumps all over the surface. You might not be able to see them from far away, but they’re there. Once you look closely or hold the item, it can feel scratchy or bumpy all over. Again, you shouldn’t worry! They’re fixable and avoidable.

You’ll often notice that two parts of plastic could be overlapping in the machine. When they overlap, a slight movement or bump could cause these zits. They’re small in comparison to your printed item, but these blemishes can completely ruin it nonetheless.

When you’re trying to fit two parts of plastic together, you’ll find that it’s always tough to avoid blobs and zits. However, the next section has a few suggestions to help you prevent them from happening. 

How to Prevent Zits and Blobs When 3D Printing

Preventing the issue starts with finding out where it’s occurring. 

Although they all cause the same problems, there are a handful of causes for zits and blobs. For example, you might be using far too much plastic. This excess plastic causes the printer to overload in a sense, filling in gaps that don’t exist and using excess materials.

If the extruder is priming too much plastic, you might notice problems occurring at the start of the perimeter. A quick solution to this common problem is to create a negative on the restart distance to prevent an overlap. Instead of beginning right when the plastic melted, it’ll start slightly beyond this location. The result is a smooth, blob-free surface.

The extruder nozzle could also be the culprit. It’s the primary tool that creates your 3D printed items, making it easy to see why several issues could occur there. When the pressure starts to build up inside of the nozzle, it might produce way more plastic than you need for the project at hand. This excess pressure causes blobs that can string along or mound all at once.

Adjusting the coasting setting on your 3D printer will relieve pressure right before the perimeter. Since this is often the area that a 3D printer causes zits and blobs, it’ll have smooth pressure throughout the project. You won’t have an excess dump or release of pressure, shooting plastic and ruining the surface.

All speeds need to be set on the same value, producing a uniform level throughout the project. If one part prints slowly, but a quicker process follows it, it can cause an array of problems to the item. To avoid this issue, make sure that everything is moving slowly. 3D printing is a matter of patience, so don’t rush it!

If all else fails, you can manually adjust the 3D printer right when the blob occurs. It’s often hard to find out unless you already know where it’s going to happen. You can manually move the starting point to prevent overlapping. Try setting it over to the back of the project or somewhere that isn’t as crucial to the appearance. In the end, this will help to smooth the surface significantly.

On the other hand, you can also take on the problem after it ends. If you’re not worried about a little bit of elbow grease, you can quickly sand the zits and blobs right off of the surface. Since 3D printers use plastic, you can’t go as quickly as you would with a wooden item. Instead, you need to wet the plastic and sand it slowly and constantly. Otherwise, you’d scratch and damage the surface even worse than it already is.

3D Printing Troubleshooting Tips

Sometimes the issue doesn’t even appear on the outside of the printed object. You might look at it and think that everything seems perfect. Unfortunately, there is an array of interior errors that can impact the item’s integrity. For example, poor infilling will lead to a fragile object that looks great but breaks easily.

If you look at the inside of a 3D printed item, you’ll notice that it’s covered in lines. These lines are simply the infill pattern created by the printer. However, it should look like a solid object rather than a porous surface. Changing the infill pattern, adding more plastic, or slowing the speed can prevent all of these errors.

A 3D printer that has an incorrect infill pattern for the item in question could be a user error. If you don’t have enough plastic in the machine, it attempts to finish the entire project regardless of how little it has to work with. Since the outside is the most important area, it’ll look fine but feel weak.

There are all sorts of issues caused by a 3D printer that’s moving too fast. We often become impatient since it can be a very slow process.

However, it’s always better to have a perfect result that takes a while rather than a porous, fragile or otherwise imperfect result that’s quick. Many zits, blobs, and gaps can be solved by slowing all of the settings down.

Increasing the extruder temperature is another way to fix common problems. Since it pumps out plastic throughout the process, you might notice a dull or scratched surface. This dullness or scratchiness occurs because the plastic isn’t able to fully melt and form to the object that you’re trying to create. Try to increase the extruder temperature by about 5 to 10 degrees at first.

You can also try to look for a clog throughout the machine. Clogs will cause gaps, weak points, and incorrect shapes all around the object. They can also cause internal damage to your 3D printer if they get bad enough. Fortunately, once the pressure is relieved, you’ll be right back where you started in good condition.


Here are the key points you should take away from this article:

  • Zits and blobs are the divots and bumps that appear when excess plastic builds upon the object you’re printing. These can appear due to user error or machine error. 
  • There are several potential causes of zits and blobs. The extruder priming too much plastic, the extruder nozzle producing too much plastic, and improper coasting settings are all possible causes. 
  • You can solve other problems with 3D printing by increasing the extruder temperature, looking for clogs in the machine, and slowing the print speed down. If none of these tips work to solve your issue, your best bet is to search the internet for a solution. 

Make sure you check out our YouTube channel, and if you would like any additional details or have any questions, please leave a comment below. If you liked this article and want to read others click here.


I'm Rob, the founder of 3dprintscape.com. I’m a Marine Corps vet with a master’s degree in Information Systems and have been working in the technology field for over a decade. I started working with 3D printers because I was fascinated by the technology and wanted a hobby that my kids and I can enjoy together.

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