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Poor Quality Bridges

· 5 min read
Pranav G.
Pranav G.

Poor Quality Bridges​

What Is It?​

Long bridge segments in your 3D prints can sag a little due to the lack of supports or high printing temperature. In these cases, the filament lines drool down and spoil the appearance of your 3D prints. Excessive sagging ruins the bridge's structural integrity and might even cause interference issues with mating components.

What To Check?​

  • Print temperature
  • Print Speeds
  • Support settings
  • Fan settings
  • Print geometry

How To Fix It?​

Lower The Print Temperature​

A high printing temperature will melt the filament to a higher degree, increasing its viscosity. The increased viscosity will make the filament flow easily out of the nozzle. This tendency is not favorable for bridges, as the molten filament will drool quickly once extruded, resulting in dropping segments underneath the bridges.

Additionally, the filament might take more time to cool down, increasing the chances of sagging bridges.

If your 3D print has several bridges, you can calibrate the filament temperature in 5 °C intervals compared to your typical settings. It should improve the quality of bridges and improve the print's quality.

Slow speeds will facilitate good adhesion with the previous layers of the bridge, reducing the prints' sagging. Additionally, with a slow extrusion speed, the filament will have adequate time to cool down and solidify quickly.

However, if you print too slowly, the extruded filament can drool down instead of forming a fine thread with the nozzle. Try reducing the current print speed in 10-15 mm/s intervals till you notice an improvement in the quality of your bridges.

Increase Cooling Fan Speed​

If the extruded filament is not cooled quickly, it'll drool down, affecting the quality of your bridges. It's always recommended to set the cooling fan speed to 100% while printing bridges. Some slicers have specific settings which let you control the fan speed for the bridge sections in your prints.

The exceptions, in this case, are ABS and other high-temperature materials. It would be best if you didn't use a cooling fan with these materials; otherwise, you might experience layer splitting and warping issues. The best solution with these materials is to print at low speeds and reduce the printing temperature.

Use Supports​

Support pillars reduce the gaps between two overhang points and hold up the bridge segments. They can reduce the sagging of the bridges and improve the quality of these sections. You'll have to fine-tune the support settings to reduce the side effects of support pillars on your print's surface.

Reduce the Filament Flow Rate​

A high flow rate will increase the chances of the extruded material drooling when printing in thin air. It will affect the quality of your bridges and also ruin the appearance of the bridge segments due to the extra material.

Try to keep a 60% or 70% flow rate for your bridge sections. Some slicers have specific Bridge settings for this scenario, using which you can control the filament flow rate for bridges.

Weak Infill Pattern​

What Is It?​

Infill is a unique aspect of 3D printing that allows you to use less material but still maintain the structural integrity of your 3D printed part. However, incorrect infill settings might result in weak infill structures, which reduce the overall strength of your prints. This setting is crucial with functional and load-bearing components where part strength is an essential factor.

A weak infill pattern appears like a webbed structure inside your 3D prints rather than looking like a solid pattern of lines. If your prints fail despite high infill density, the extruded infill lines are weak and do not provide the necessary strength to your 3D prints.

What To Check?​

  • Infill Print Speed
  • Infill Density
  • Infill Flow Rate

How To Fix It?​

Lower the Infill Print Speed​

Usually, the infill speed is kept more than the standard printing speeds as the appearance of infill perimeters doesn't matter much. But, with high print speeds, the material might not flow properly, leading to under-extrusion in certain infill sections. It will result in a webbed infill structure, compromising the strength of the part's infill.

Try printing infill at 100 -120% of the typical print speeds. This value should help you achieve a delicate balance between print quality and infill quality.

Increase the Infill Flow Rate​

A high flow rate and low print speeds are an excellent combination to ensure that the nozzle extrudes adequate material at a good pace. If you're noticing gaps in your infill patterns, try to increase the flow rate for infill by 5-10% until you achieve a smooth and solid infill line pattern.

Increase Infill Density and Infill Line Width​

Increasing the infill density percentage will add more material within the cavity and increase the strength of your 3D-printed part. But, this will consume more filament and increase the overall printing time.

Similarly, if your infill lines are too thin and flimsy, try increasing the infill line width. This value should help you achieve thicker lines and reduce the chances of weak infill patterns.