Introduction
After testing various types of flexible filament (TPU and TPE) in our DunaTech workshop, I can confidently say working with this material is challenging, but the results are worth it. This type of filament is perfect for flexible parts like phone cases, seals, or wheels. However, not all printers are designed to handle it without specific adjustments. Here’s how to do it correctly. In this practical guide, I’ll walk you through every step — from hardware prep to slicing tweaks — so you can print flexible filament without the usual headaches.
Preparing Your Printer
The single most important factor for success with flexible filament is your printer’s extruder setup. Direct-drive extruders handle TPU and TPE far better than Bowden systems because the filament path is short and stiff. Before you start printing flexible filament, make sure your printer is ready for this material. In my tests, Bowden extruders were less effective than direct-drive extruders due to the distance between the motor and the hotend. Here are the essential steps:
1. Use a Direct-Drive Extruder
– **Advantage:** Shorter distance for the filament to travel, reducing the risk of clogs.
– If your printer has a Bowden setup, consider upgrading to a direct-drive extruder. I’ve seen many users convert their Ender 3 or CR-10 with a $20 kit — it’s a game-changer for flexible filament.
2. Adjust Flow and Speed
– **Recommended Speeds:** Keep the print speed between 20-30 mm/s to prevent filament tangling. Going faster than 30 mm/s often causes under-extrusion or jams.
– **Flow:** Adjust the flow to 105%-110% if you notice layers not adhering well. In my experience, TPU from brands like eSun or Overture needs that extra push to fill gaps.
3. Use a Proper Nozzle
– Opt for nozzles of 0.4 mm or larger to avoid blockages. A 0.6 mm nozzle is even better for flexible filament, as it reduces backpressure.
– Ensure the nozzle is clean before starting. A cold pull with nylon can remove any debris that might cause clogs.
Software Configuration
The slicing software is key to achieving good results with flexible filament. When we tested pre-configured profiles in Cura and PrusaSlicer, we noticed they required specific adjustments. Set the following parameters to get reliable prints every time:
1. Minimal Retraction
– Reduce retraction to 1-2 mm (or disable it) to prevent the filament from twisting inside the extruder. With TPU, retraction often does more harm than good — it can grind the filament or cause jams. I usually set retraction to 1 mm at 20 mm/s for direct-drive setups.
2. Layer Height
– Use a layer height of 0.2 mm for a balance between detail and adhesion. Going lower than 0.15 mm can cause the nozzle to drag through the soft material, while 0.3 mm layers may not bond well.
3. Travel Speed
– Set a low speed (~60 mm/s) for non-printing movements. High travel speeds can yank the filament out of the nozzle, causing stringing or blobs. I keep travel acceleration under 500 mm/s² for flexible filament.
Useful Tips for Printing Flexible Filament
Here are some tricks we discovered in the workshop after printing over 10 kg of TPU. These tips will save you time and frustration:
– **Use a Heated Bed:** Keep the bed between 50-60 °C to improve adhesion. Without heat, the first layer tends to curl up, especially with softer TPU (Shore 85A or lower).
– **Additional Adhesives:** If the filament doesn’t stick well, try Kapton tape or glue stick. I’ve had great results with a thin layer of PVA glue on a glass bed — it releases easily once the bed cools.
– **Storage:** Store the filament in an airtight bag with desiccant to prevent moisture absorption. Wet TPU prints like a nightmare — you’ll see bubbles and stringing everywhere. A filament dryer set to 45°C for 4 hours works wonders.
– **Printing Multiple Parts:** If you’re printing several small objects, space them out on the bed. Flexible filament tends to warp less when each part has enough room for the first layer to cool evenly.
Troubleshooting Common Issues
Even with the best setup, problems may arise. Here’s how to solve them based on real workshop experience:
1. Extruder Jams
– **Cause:** Printing speed too high or excessive retraction. The filament buckles inside the extruder gear.
– **Solution:** Lower the speed to 20 mm/s and reduce retraction to 1 mm or less. Check that your extruder tension isn’t too tight — it should grip the filament without crushing it.
2. Layers Not Sticking
– **Cause:** Insufficient flow or layer height too high. The nozzle isn’t squishing the filament enough.
– **Solution:** Increase the flow to 110% and set the layer height to 0.2 mm. Also, lower your Z-offset by 0.05 mm to get better first-layer adhesion.
3. Filament Not Advancing
– **Cause:** The filament is too soft for the Bowden system. The flexible material compresses instead of pushing forward.
– **Solution:** Switch to a direct-drive extruder. If that’s not possible, use a stiffer TPU (Shore 95A or higher) and keep the Bowden tube as short as possible.
4. Stringing and Oozing
– **Cause:** Too much heat or no retraction. Flexible filament oozes easily at high temperatures.
– **Solution:** Lower the nozzle temperature by 5-10°C (try 220°C for TPU). Enable coasting in your slicer to reduce pressure at the end of each path.
FAQ
Can I use flexible filament with any printer?
Not all printers are compatible. Printers with direct-drive extruders perform better than Bowden setups. If you have a Bowden printer, you can still print flexible filament, but stick to stiffer TPU (Shore 95A) and keep speeds below 20 mm/s.
Do I need a heated bed?
Yes, a heated bed at 50-60 °C improves the adhesion of the first layers. Without it, the print may warp or detach, especially with softer TPU. A PEI sheet or BuildTak surface also helps.
How can I prevent the filament from breaking inside the extruder?
Lower the print speed and adjust the retraction to minimize stress on the filament. Also, make sure your extruder gear isn’t too tight — it should grip without crushing the filament. Dry filament is less brittle, so store it properly.
What’s the best temperature for flexible filament?
Most TPU prints well between 220-240°C. Start at 230°C and adjust based on your printer and brand. Too hot causes oozing; too cold causes poor layer adhesion. TPE usually needs 10-20°C less than TPU.
Conclusion
Working with flexible filament requires patience and precise adjustments, but the results are impressive. If your printer is properly set up and you follow these tips, you’ll be able to print flexible parts without issues. Remember to start with a direct-drive extruder, keep speeds low, and dry your filament. If you have more questions, leave a comment or check out our article on how to use a Sovol filament dryer to keep your materials in perfect condition.
— The DunaTech Team