Print Settings for TPU 70A

Sovol SV04 IDEX
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I am showing here the solution which I’ve found to print the TPU with shore 70A.

The test print can be seen here: [Sovol SV04 TPU 70A Settings - YouTube]

Filament used: Recreus Filaflex TPU Shore 70A

The key factors are:

  • frequent and long retraction
  • slow speed
  • extruder tensioner completely loosed

I know that using retraction with TPU may seem strange, usually on the web everybody says that the retraction must be disabled with TPU. For the SV04 is the opposite: massive retraction fixes the problem.

If you don’t setup retraction this way, the filament will get stuck inside the extruder, because its pushed until it compresses and modifies its shape and then cannot flow anymore.
Once the filament gets stuck, the gear will grind it and then it gets thin and it cannot be pushed anymore through the extruder.
Retraction makes sure the filament realigns inside, undoing the compression, so it can flow through the extruder.
Retraction must be frequent: the retraction must happen before the filament is deformed permanently by compression and ground by the gears, otherwise it cannot be recovered and the print is compromised and has to be restarted form the beginning.

Here below you can see the options for Cura. I am using Cura 5.2 for Mac with the Sovol SV04 profiles.

Cura Options:

  • Print speed: 20mm/s

Travel:

  • Enable retraction: yes
  • Retract at layer change: yes
  • Retraction distance: 10mm
  • Retraction speed: 50mm/s
  • Retraction extra prime amount: 0
  • Retraction min travel: 1.5
  • Max retraction count: 10000 (should be infinite)
  • Max extrusion distance window: 10mm
  • Combing mode: all
  • Max comb distance with no retract: 30mm
  • Retract before outer wall: no
  • Z Hop when retracted: yes
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Update: Z Hop when retracted: NO

This seems to prevent some stringing.

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Update:

  • Retraction distance: 6mm (reduced from 10: reduces risk of blocking the filament)
  • Retraction speed: 35mm/s (reduced from 50: reduces risk of blocking the filament)
  • Retraction Extra Prime Amount: 1mm^3 (new setting: prevents gaps after starts)
  • Nozzle Switch Extra Prime Amount: 1mm^3 (new setting: prevents gaps after starts)

NOZZLE CLEAN BEFORE PRINT !!
I discovered why sometimes soft tpu is not printed despite correct options: nozzle is clogged.
I STRONGLY suggest to CLEAN the nozzle BEFORE each print.

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