Bridging is a critical feature in 3D printing that allows your printer to lay filament across open gaps without using supports. Mastering this technique enables faster prints, less material use, and cleaner results. However, poorly tuned slicer settings often lead to sagging bridges, stringing, or failed spans. This guide explains the best slicer settings and techniques to improve bridging performance and successfully print over gaps without support structures.

What Is Bridging in 3D Printing?

Bridging occurs when the printer extrudes filament between two points with no support beneath it. This process tests your printer’s ability to maintain proper tension and cooling while the filament spans open air. Good bridging results in straight, flat lines of filament with minimal sag. Poor bridging shows drooping, broken strands, or surface imperfections underneath the bridge.

Printing clean bridges without supports requires a combination of hardware reliability, proper material cooling, and optimized slicer settings.

Why Bridging Settings Matter

Improving bridging settings allows you to:

• Avoid time-consuming and difficult support removal
• Reduce filament usage and print time
• Achieve smoother undersides in open structures
• Produce functional parts like ventilation holes, overhangs, and mechanical gaps

Even with a well-tuned printer, default slicer settings often fail to optimize bridge quality. Tuning specific settings for bridges is essential.

Key Slicer Settings for Strong, Clean Bridging

1. Bridging Speed

Recommended Setting:
Reduce bridging speed to 20–30 mm/s.

Why It Matters:
Printing slower during bridges allows the extruded filament to stay taut as it cools, minimizing droop. Fast speeds stretch the filament too far before it has time to solidify, resulting in sagging.

How to Set It:
Most slicers, including Cura, PrusaSlicer, and SuperSlicer, have dedicated “Bridge Speed” or “Bridge Flow” settings that can be adjusted independently of regular print speed.

2. Bridging Fan Speed (Cooling)

Recommended Setting:
Use 100% fan speed during bridging.

Why It Matters:
Immediate and strong cooling solidifies filament as it spans a gap, helping it hold its shape. Without adequate cooling, the bridge will sag under its own weight.

How to Set It:
Enable “Bridge Fan Speed Override” in your slicer and set it to maximum (100%) during bridges.

Caution:
For high-temperature materials like ABS or nylon, cooling should be used sparingly or only in short bursts to avoid warping.

3. Bridging Flow Rate

Recommended Setting:
Decrease bridge flow rate to 90–95%.

Why It Matters:
Slightly under-extruding during bridging keeps the filament tighter and reduces the chance of drooping. Over-extrusion leads to excess material that collapses before cooling.

How to Set It:
Adjust “Bridge Flow” or “Bridge Extrusion Multiplier” if available in your slicer.

Test incrementally to find the best balance between sufficient adhesion and minimal sag.

4. Bridging Wall and Infill Settings

Recommended Setting:
Enable special bridging behavior for top layers and infill.

Why It Matters:
Slicers often generate top surfaces and infill that cross gaps. Applying bridge-specific parameters to these layers ensures consistent performance across the model.

How to Set It:

• Enable options like “Apply Bridge Settings to Infill” or “Bridge Skin Support Thresholds.”
• Use higher top layer counts (6–8 layers) to allow bridging strands to anchor onto previous solid surfaces.

5. Layer Height and Line Width

Recommended Setting:
Use lower layer heights (0.1–0.2 mm) and slightly wider extrusion width for bridges.

Why It Matters:
Thinner layers result in less weight for the filament to support mid-air. Wider lines offer more surface area to grip onto anchor points at each side.

How to Set It:

• Use a 0.1 or 0.2 mm layer height for models requiring precise bridging.
• Set bridge line width to 110–120% of your nozzle diameter.

6. Short Travel Distances Between Anchor Points

Recommended Setting:
Design and orient models to minimize bridge length.

Why It Matters:
The shorter the gap, the easier it is for the filament to stay taut. Reducing the distance between support points makes even poorly tuned bridges look better.

How to Achieve It:
Adjust model orientation in the slicer to place bridges across the X or Y axis, not diagonally, and use design software to add intermediate ribs or geometry to shorten unsupported spans.

7. Enable Bridging Angle Control

Recommended Setting:
Align bridges along simpler axes where possible.

Why It Matters:
Bridging across stable, fixed axes reduces the movement complexity of the print head and makes cooling more effective. Bridging at off-angles increases the chance of sagging.

How to Set It:
Use slicer controls to rotate the model or manually override bridge angle directions where available.

Additional Tips to Improve Bridging Without Supports

Use a Bridging Test Model

Printing a small bridging test model lets you visually compare different settings in minutes. Identify at what length your printer begins to struggle and tune parameters accordingly.

Reduce Nozzle Temperature Slightly

Lowering nozzle temperature by 5–10°C can reduce filament flow rate, making bridges cleaner. Be cautious not to go too low, or layer adhesion will suffer.

Use Quality Filament

Cheap or inconsistent filament may sag more easily, absorb moisture, or extrude unevenly. Dry, high-quality filament prints better bridges with more predictable behavior.

Upgrade to a Cooling Duct

If your part cooling fan struggles, upgrade to a more focused duct or dual-fan setup. A well-aimed fan dramatically improves bridge solidification.

Best Bridging Settings by Material

PLA

• Fan speed: 100%
• Bridge speed: 20–25 mm/s
• Bridge flow: 90–95%
• Excellent bridging ability with proper cooling.

PETG

• Fan speed: 60–80%
• Bridge speed: 20 mm/s
• Bridge flow: 95–100%
• More stringing than PLA; cooling and flow balance is key.

ABS

• Fan speed: 20–40% (or off)
• Bridge speed: 20 mm/s
• Bridge flow: 95%
• Use caution with fans to avoid warping.

TPU (Flexible)

• Fan speed: 60–80%
• Bridge speed: 15–20 mm/s
• Bridge flow: 95%
• Very limited bridging capability; avoid large unsupported spans.

Common FAQs About Bridging Without Supports

Why does my bridge sag or droop?

This is usually due to high speed, poor cooling, excessive flow, or long unsupported spans. Slower speeds and higher fan output typically improve results.

Should I increase or decrease flow rate for bridging?

Slightly decreasing flow to 90–95% helps keep the filament taut. Excess material causes sagging before it cools.

What’s the longest bridge I can print?

With optimized settings, most well-tuned printers can bridge 20–40 mm successfully. Advanced printers with good cooling may reach up to 60 mm.

Can bridging replace supports entirely?

Not in all cases. Bridging works well for horizontal gaps but is not a substitute for supporting complex overhangs, steep angles, or disconnected parts.

Does nozzle size affect bridging?

Yes. A 0.4 mm nozzle is most common and performs well. Larger nozzles produce thicker, heavier lines and may bridge poorly unless speed and cooling are tuned carefully.

Conclusion

Bridging without supports is one of the most useful skills in 3D printing. By fine-tuning slicer settings such as bridge speed, flow rate, cooling fan output, and layer height, you can produce strong, clean bridges with minimal sag. Combining these settings with thoughtful model orientation, smart design, and quality filament will allow you to eliminate unnecessary supports, reduce post-processing, and improve overall print efficiency. With testing and practice, you can consistently span large gaps and unlock more advanced, efficient printing strategies.