Poor 3D Printing Bridging: 6 Effective Solutions for Improving It

3D printing is a challenge for most enthusiasts and makers, requiring continuous learning and deep understanding so as to effortlessly print perfect objects. We've previously discussed many common printing issues on model surfaces, such as 3D print stringing, bottom warping, over-extrusion, and more. Today, we aim to explain another problem in FDM/FFF 3D printing: bad 3D printer bridging. Bridging is a commonly used tool that can save your material and time because it doesn't require any support and still achieves good quality. Let's delve into this quick guide to avoid poor bridges on your objects.

What is Bridging in 3D Printing?

3D Printed Bridge

(3D printer bridging test)

Bridging, as its name indicates, refers to the horizontal overhangs between two points of a 3D print without any layer supports underneath. Printing a short bridge with thin layers doesn't need support, and it can suspend the material perfectly in mid-air. However, larger bridges relies on adequate support, which is vital for successful printing. Bridges are similar to 3D printing overhangs, requiring support if necessary to achieve perfect results. Good 3D printer bridging typically presents a solid structure. Conversely, poor-quality bridges tend to sag, lack precision, exhibit loose filament strands, and even collapse or break.

What Are the Causes of Poor Bridging?

There are many reasons behind the failing bridging, primarily influenced by temperature, print speed, and material you use, and they affect the final result. Fortunately, this issue is relatively easy to eliminate. Here's why the printer didn't extrude your desirable and intended straight line:

  • The printer hotend is too hot.
  • The cooling is Insufficient.
  • The material extruded too quickly and too much.
  • No supports are used for large bridges.

How to Fix Bad 3D Printing Bridging

Method 1: Lowering print temperature

If the print temperature is set too high and isn't suitable for the filament you're using, it can lead to the bridging problem. To achieve the best printing quality, different materials require different temperatures. PLA typically prints between 190-210°C. Meanwhile, higher-temperature materials like ABS, ASA, and PETG require much hotter temperatures than PLA. PETG filament, for example, needs at least 220°C, whereas ASA filament typically prints in the range of 240°C - 260°C. You can start by checking the recommended temperatures from the material manufacturer, then print small test models, gradually reducing the temperature by 5°C each time until the bridge quality improves.

Method 2: Increasing cooling

Increasing cooling allows the molten filament extruded from the nozzle to quickly deposit and harden into a solid structure, preventing 3D print bridges from sagging. Begin with enabling print cooling and maintain a 100% fan speed when printing the bridge section. It's important to note that if the printing temperature is too low and combined with intense cooling, it may lead to nozzle clogging or poor bed adhesion in the first layer.

Method 3: Reducing print speed

Reducing your printer speed can effectively alleviate poor bridging issues. Imagine that when the print head moves rapidly and the extruder pushes out the filament in a quick motion, the filament doesn't have enough time to solidify, resulting in bent or fractured layers in the bridge. You can run your 3D printer at its regular speed first. If the issue still exists, gradually decrease the print speed in increments of 10mm/s until the print quality gets better.

Method 4: Decreasing extrusion multiplier

The extrusion multiplier (or flow rate) controls the amount of filament extruded. When this setting is too high, an excess of molten filament is pushed out without enough time to solidify, causing various problems like 3D print blobs, rough top layer surfaces, and poor 3D printing bridges. Typically, using 100% basic flow rate for PLA will get good results. So you can test and gradually reduce it by increments of 5% to 10% for improvements.

Method 5: Using supports for large bridges

If none of the methods mentioned above can work, try generating supports for long bridges, as this can significantly enhance the chances of success. However, removing the supports afterward may leave noticeable marks on the surface, requiring post-processing for smoothing if necessary. Alternatively, for extremely long bridges where the printer cannot achieve good results, consider splitting the bridge 3d model's STL file into parts. Then, print them separately and finally assemble them together.

Method 6: Printing with high-quality filament

High-quality 3D Printer Filament

It's possible that the issue does not stem from your printer or slicer settings but rather from the use of low-quality filament, which results in 3D prints with poor bridges. One of the keys to successful 3D printing is always using high-quality filament. Opt for trusted brands like Anycubic, offering 1.75mm PLA filament, which is easy to print and arrives in neat, sealed packaging, available in up to 15 color choices.

Moreover, keeping your filament dry is crucial for proper storage. When the filament absorbs moisture and dust, these impurities can cause a clogged nozzle, affecting print quality and dimensional accuracy. It's recommended to seal and store the filament in a dry ambience once it's been opened and used. Wet filament is not irreversible and you can easily dry it using some tools. I recommend you check out this article on 'How to Dry Filament'.