How to Print Sunlu TPU on a Stock Ender 3 V2

Printing flexible filament on a Bowden-tube printer like the stock Ender 3 V2 is challenging but achievable with specific modifications and slicer settings. Sunlu TPU 95A is one of the most forgiving flexible filaments for Bowden setups because of its moderate Shore hardness and consistent diameter tolerancing. This guide covers the hardware modifications, slicer settings, and print sequence needed to get reliable TPU output on an unmodified or minimally modified Ender 3 V2.

Why TPU Fails on Bowden Setups

Flexible filament buckles under compression forces inside the long PTFE tube. When the extruder pushes and pulls, the flexible strand folds against the tube wall instead of transmitting force to the nozzle. The fix is to eliminate retraction entirely and minimize every other force that could cause buckling.

Required or Recommended Modifications

Modification	Type	Priority
Capricorn XS PTFE tube	Hardware (~$10)	Essential
Metal extruder arm replacement	Hardware (~$8)	Essential
TPU extruder guide insert (printed in PETG)	Printed part	Strongly recommended
Direct drive conversion (Micro Swiss DD)	Hardware (~$60)	Optional but eliminates most problems

The stock plastic extruder arm on the Ender 3 V2 has a gap between the drive gear and the PTFE tube entry point. Flexible filament buckles into this gap immediately. Replacing the arm with a metal version or printing a guide insert that closes the gap is the single highest-impact fix available.

Slicer Settings for Sunlu TPU 95A on Ender 3 V2

Parameter	Setting
Nozzle Temperature	220–230°C
Bed Temperature	30–40°C
Retraction Distance	0 mm (disabled)
Print Speed	15–25 mm/s
Travel Speed	100 mm/s maximum
Fan Speed	50–75%
Combing	Enabled
Z-Hop	Disabled
Flow Rate	95–98%

Print Speed Is the Most Critical Setting

The single most important setting for Bowden TPU is print speed. At 40+ mm/s, the extruder must deliver filament faster than the flexible strand can consistently compress in the tube. At 20 mm/s, there is enough time for the soft filament to be pushed through reliably. Never attempt to increase speed until every other setting is stable. Even on a well-tuned Bowden setup, 30 mm/s is the practical ceiling for reliable Sunlu TPU printing.

Retraction Must Be Zero

Disable retraction completely. Any retraction will buckle the filament in the tube. Use combing (avoid crossing perimeters) to route all travel moves inside the part, so any ooze falls inside the cavity rather than across open air. The residual internal stringing is structurally irrelevant and invisible in assembled parts.

Recommended Filament Dryer

A dedicated filament dryer is the single most impactful tool for consistent prints. The Sunlu Filadryer S2 holds accurate temperature with a circulating fan, accommodates standard spools, and includes a pass-through hole for drying-while-printing. It is the dryer referenced throughout this guide.

View Sunlu Filadryer S2 on Amazon →

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Frequently Asked Questions

Can I print TPU on the Ender 3 V2 without any modifications?

You can attempt it, but expect jamming at the extruder gap within the first few prints. The stock plastic arm is the limiting factor. A metal arm upgrade costs under $10 and eliminates the most common failure mode. Without the modification, success depends heavily on spool diameter consistency and ambient temperature.

My TPU keeps jamming at the extruder. What is wrong?

Buckling at the extruder entry is the cause in 90% of cases. Check three things: the gap between the drive gear and PTFE coupling (close it with a guide insert or metal arm), the PTFE tube connection at the hotend (must be flush with no gap), and print speed (drop to 15 mm/s and work upward from there).

Does Sunlu TPU need to be dried before printing?

Yes. TPU is highly hygroscopic and should be dried at 55°C for 6 hours before printing. Wet TPU shows as surface bubbling, irregular extrusion width, and a characteristic popping sound. Even a new spool from a non-vacuum bag may arrive with enough moisture to cause problems, particularly at the slow print speeds required for Bowden TPU printing.