Bridging speeds: My incorrect mental model and an unintuitive result

Tl;dr: I assumed that bridging speed should be as fast as possible so the plastic doesn’t have a chance to droop. That assumption is incorrect. In fact, most printers will have best results with much lower speeds. The Artillery Genius, Prusa Mini, and Ender 3, all get great bridges at 25mm/s speeds. Here’s a video by Breaks’n’Makes that taught me this.


I got my first 3D printer; the Artillery Genius, about 4 months ago. For the first few months, I was happy just learning the basics and printing fun models, stuff like this.

As I’ve gotten more comfortable with 3D printing, I’ve also grown more curious and have started to experiment. Right now I’m particularly interested in seeing how well I can “dial in” my print profile to produce the best prints possible on the Artillery Genius.

Recently, I upgraded my slicer; PrusaSlicer to the latest version, which is 2.3.1 as I’m writing this post. This comes with profiles for the Artillery Genius built in, so I was looking forward to using these optimized profiles.

In the profile I was using before the upgrade, I had the bridging speed set to a very high number, 100mm/s. My thought was that laying down an unsupported strand of plastic should be done as quickly as possible so that it doesn’t have time to droop.

I was quite surprised to see that the default profile in PrusaSlicer had the bridging speed set to a much more conservative value, around 25mm/s. I then checked the bridging speed setting that comes with the profile for the Prusa Mini, my other printer. Here too the speed was set to a much lower value than what the printer was capable of achieving. Around 30mm/s I think.

I knew that the profiles in PrusaSlicer, especially for the Prusa machines were very well tuned. My understanding of bridging speeds was thus wrong and I needed to learn more about this.

This led me to this excellent video by Breaks’n’Makes, where Joe shows different tests he did for dialing in the bridging parameters for his Ender 3. He tests a number of parameters, but the speed; which is what I was interested in the most, produced best results at 25mm/s.

This confirmed what I was seeing in the PrusaSlicer profiles, and also gave me a number of different parameters to test. I’ll be doing these tests on my Artillery Genius as well and will be writing a blog post and creating a video about the process on my YouTube channel.

The point of this post is to just say that for people who are just starting with 3D printing technology, our intuitions about things can be way off, because we have the wrong mental models for how the technology works. The only way to get better is to question your assumptions, and run tests.

But that doesn’t mean you can’t or shouldn’t have fun. I didn’t start by looking into dialing in my printer the day I got it. I spent a few months just playing around and learning the basics.

Today the hardware and software are good enough that you can get started without having to spend time figuring out these details. You only need to dive deeper when you encounter an issue or want to increase your understanding of something.

If you got into 3D printing because you have stuff to print, you can go a long way without ever needing to tweak any of these settings. It’s just as plug and play as a laser printer from any reputable manufacturer like HP, Epson, Canon, etc.

Finally, I write this blog because I think that I can contribute to this space. I’m a beginner, so I have a beginners perspective on things. I have assumptions that might make sense to me but are wrong. If you’re starting out in 3D printing, you might have similar assumptions. I hope that this and other posts I write in the future will be helpful to other beginners out there who are looking to learn more about this exciting technology.

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