Mar 7, 2019

Bridging (3D Printing) – 6 Tips & Tricks for Perfect Bridges

Whether you have a little or a lot of experience with 3D printing, you have probably experienced the frustration of messy bridges. Hopefully this article will help you print clean bridges with a couple easy tips and tricks!

Bridging (3D Printing) What Is Bridging?

3D printed bridge prototype. Source: Marcin Traczyk / ZMorph

Bridging in 3D printing is an extrusion of material that horizontally links two raised points. However, if you are reading this article, the bridges in your prints are probably not too horizontal. Don’t beat yourself up. Bridging problems are extremely common, and (take a deep breath) are relatively easy to eliminate.

So, let’s dive into some quick tips and tricks to bring the best bridging 3D printing results!

Bridging (3D Printing) Test Your Printer

A tricky bridging test successfully 3D printed. Source: walter / Thingiverse

Before you begin tweaking settings, it is important to see how well your printer can (or can’t) bridge. Try printing this Bridging Test. In one print, you will be able to see what bridge lengths are hard for your printer. 50 – 100 mm bridges are good. 150+ mm bridges are excellent. If this test doesn’t turn out well, don’t worry. This is just to figure out the extent of the problem.

Bridging test print: Bridging Test by Thingiverse user walter

Bridging (3D Printing) 1. Increase Cooling

Print fan for cooling extruded material. Source: Connor TeVault / Elon Technology Blog

When trying to optimize your printer’s bridging capabilities, first increase your print cooling (print fan speed). If you are printing bridges with a low print cooling, the filament will just sink into a big mess of molten plastic. Start at 100% fan speed, and keep an eye out for bridging improvements.

However, if you are noticing clogging or poor layer adhesion, your fan is too high! Bring it back down in 5% increments, and move on to the next easy fix.

Bridging (3D Printing) 2. Decrease Flow Rate

An extreme case of over-extrusion. Source: Simplify3D

For material to cleanly bridge a gap, it must set quickly. So, if too much molten filament is flowing from the nozzle, it will have not time to set. This will most likely make your print look like London bridge falling down. By decreasing your Flow Rate (or Extrusion Multiplier) in your slicer, your printer will be able to extrude a steady flow of filament that can cool into a beautiful bridge. 

Bridging (3D Printing) 3. Decrease Temperature

Temperature towers showing the different capabilities at different temperatures. Source: brunofporto / Thingiverse

This next tip is very similar to #2. If your nozzle temperature is too high and too much filament is allowed to flow from it, the printing material will have not have enough time to cool and set. This will probably result in filament sticking to your nozzle or forming a very messy bridge.

To test the different temperatures, you will need to manipulate the g-code to get the temperature to change with each level. To get to this option in Cura, Select ‘Extensions’ → ‘Post processing’ → ‘Modify g-code,’ and add the ‘Vary Temp With Height’ plugin. From here, you can input the height increment (for how often you want to change temperature) and temperature increment (for how much you want to change it). The designer offers the necessary code for Slic3r and Cura in the Thing Details.

Temperature test print: Customizable Temperature Tower by quirxi

For more information about print temperatures for different materials, read The Best Printing Temperature for Different Filaments.

Also, 3D Printer Calibration Guide – How to Calibrate Your 3D Printer is a great start to fine-tuning your filament settings.

Bridging (3D Printing) 4. Decrease Print Speed

A clean, successful bridging test. Source: Adam Adikimenakis / YouTube

High print speed can also affect bridge quality. If your nozzle is moving too fast, the filament will not have time to adhere to the previous layer or set in time to bridge a gap. High print speeds can result in huge messes.

Try decreasing your print speed in 10 mm/sec increments until you see some improvement. Don’t go too slow though. If your nozzle is moving too slow, the filament will be suspended in the air for too long and will eventually droop. So play around with some speeds, and you are bound to find the perfect one.

Bridging (3D Printing) 5. Adjust Model Orientation

Letters Y, H and T 3D printed following the 45° rule. The Y can be printed without support! Source: Perry Cain / 3DHubs

If you are completely tired of tweaking settings to get longer bridges or you don’t have the time to start, try orienting your model to totally (or mostly) eliminate bridges in the model. Just remember the 45° rule. If an overhang is over 45°, you will need supports.

If you are especially brave, check out How To Master 3D Printing Overhangs Exceeding 45°.

Bridging (3D Printing) 6. Add Supports

Bridge successfully printed with supports. Source: Scott Cahoon / Matterhackers

Speaking of supports…why not use them? Supports will eliminate your worries about messy bridges. They may be a pain to remove, but check out this All3DP article: 3D Printing Support Structures – All You Need To Know in 2019 to get the best support structures from your machine. (NOTE: Make sure that you will be able to remove supports after printing. Some models make this removal process nearly impossible.)

Bridging (3D Printing) Related Articles

Checking dimensional accuracy of a 3D print. Source: Alastair Jennings / All3DP

License: The text of "Bridging (3D Printing) – 6 Tips & Tricks for Perfect Bridges" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.

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