Bridging is one of the most useful skills in 3D printing—creating horizontal structures that span gaps without using support material. It saves time, reduces filament waste, and avoids post-processing headaches. But many users struggle with sagging, stringing, or failed bridges.
This expert guide reveals how to print perfect bridges without supports by dialing in slicer settings, choosing the right materials, and applying real-world printing techniques. Whether you’re printing functional parts or intricate models, mastering bridges will take your prints to the next level.
What Is Bridging in 3D Printing?
Bridging is the process where a printer lays down filament between two points in mid-air—like a suspension bridge. No supports underneath, just solid anchors on both ends.
Why It Matters
- Saves time and filament by eliminating supports
- Leaves a cleaner finish (no support scars)
- Ideal for vents, slots, and hollow structures
- Enables more creative, support-free designs
Common Bridging Problems (and What Causes Them)
| Issue | Likely Cause |
|---|---|
| Sagging bridges | Printing too hot or too slow |
| Stringing between gaps | Inadequate retraction or excessive temperature |
| Poor adhesion at ends | Low flow rate or anchor points too short |
| Drooping infill | No bridging settings enabled for infill lines |
Understanding the cause is the first step to solving it.
Essential Slicer Settings for Bridge Success
Every slicer has bridge-specific settings. Here’s what to focus on:
1. Bridge Speed
📌 Recommended: 25–40 mm/s
- Slower speeds help the filament stretch cleanly without sagging.
- Higher speeds can cause filament to drag and droop.
✅ Lower is usually better, but don’t go too slow—your filament needs momentum to bridge across.
2. Bridge Flow Rate (or Bridge Extrusion Multiplier)
📌 Recommended: 110%–125%
- Slightly over-extruding during bridges improves adhesion and supports the line mid-air.
- In Cura: Bridge Flow Rate
- In PrusaSlicer: Bridge Flow Ratio
✅ Increase cautiously—too much can cause blobs.
3. Bridge Fan Speed
📌 Recommended: 100%
- Cooling is critical. Rapid solidification prevents sagging.
- Enable full fan speed during bridging moves only.
✅ Use this even if you usually print with reduced cooling (like PETG).
4. Minimum Bridge Anchor Length
📌 Recommended: At least 3–5mm per anchor
- Bridges need strong foundation points on both ends.
- Modify your design or orient the model so anchor points are solid.
✅ Ensure both ends of the bridge are supported by fully solid perimeters or walls.
5. Disable Support in Bridge Areas
- Many slicers allow support overrides for bridges.
- Look for options like “Don’t support bridges” (Cura) or “Avoid bridging perimeters” (PrusaSlicer).
✅ This gives slicer more freedom to handle bridges efficiently.
Recommended Print Settings for Different Materials
| Material | Temp Range | Bridging Tips |
|---|---|---|
| PLA | 190–210°C | Ideal for bridging. Use max cooling, moderate flow. |
| PETG | 220–245°C | Use slower speeds, full fan, minimal retraction. |
| ABS | 230–250°C | Keep chamber enclosed; bridging works but more difficult. |
| TPU | 210–230°C | Avoid long bridges—rubbery filament sags easily. |
| Nylon | 240–260°C | Use drier filament; difficult to bridge cleanly. |
📌 Always dry hygroscopic filaments like PETG or Nylon for best results.
Expert Techniques for Bridging Without Supports
1. Orient Your Model for Natural Bridging
Rotate the part so bridge spans are short and anchored cleanly. Avoid bridging across large circular openings—print those vertically instead.
2. Use Chamfers or Self-Supporting Angles
Design overhangs at 45° angles to reduce or eliminate the need for bridging altogether.
3. Enable Ironing (Optional)
Some slicers allow “ironing”—where the nozzle gently flattens top layers. It can help smooth bridges after successful completion.
4. Test Your Printer’s Bridge Limit
Use a bridge calibration model (like this one on Printables) to test maximum bridge span your printer can handle. Tune settings based on the results.
5. Tune Retraction and Travel Moves
Stringing on bridges is often caused by:
- Under-retraction
- Travel moves through the gap
📌 Increase retraction distance/speed slightly, and enable combing or avoid crossing perimeters.
Best Bridge Test Models to Try
| Model | Purpose |
|---|---|
| Bridge Test Tower | Tests various bridge lengths |
| Mini All-in-One Test | Combines bridges, overhangs, and gaps |
| Benchy (rear roof) | Quick real-world bridge test |
| Calibration STL (45° supportless test) | Pushes slicer and material limits |
Post-Processing Bridged Prints
Sometimes, bridges may show fine strands or small droops. Try these methods:
- Heat gun smoothing: Use briefly at low heat
- Fine-grit sanding: 400+ grit to polish underside
- Flush cutters: Remove loose strands easily
Avoid using too much force—bridges are often slightly weaker than supported areas.
FAQs
Q1: How long of a bridge can I print without support?
Most well-tuned printers can bridge up to 30–40mm with PLA. Higher-end machines may achieve 60mm+.
Q2: Why does my PLA bridge droop even with cooling?
You may be printing too hot or with insufficient fan speed. Try reducing temperature by 5–10°C and increasing fan.
Q3: Can I bridge with PETG or ABS?
Yes, but it’s harder. Reduce print temps, slow down speed, and increase fan (PETG) or use a closed chamber (ABS).
Q4: Should I always avoid supports for bridges?
Not always. For bridges over 60mm, or in high-detail models, supports may be more reliable than risk failure.
Conclusion
Mastering bridges without supports is a milestone for any 3D printing enthusiast. With the right slicer settings, filament choices, and model orientation, you can print clean, efficient, support-free spans that save material and look amazing.
Start small, test frequently, and dial in your bridge game step-by-step. Once tuned, you’ll be able to tackle even advanced models with confidence—and zero supports.