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I've built and done some simple tests on a TEVO Tarantula but I've noticed some pretty dramatic under extrusions.

My equipment:

  • TEVO Tarantula;
  • Jim Brown's easy config fork of Marlin;
  • Titan extruder (came with printer).

I've updated the firmware with the 400 steps as advised and calibrated the extrusion with the 100 mm method:

  • When I run the calibration with the Titan extruder, only the 400 steps is fine and works as expected;
  • When I connect the Bowden tube to the hotend and calibrate (at 200, 225 and 250°C), I see only ~50 mm of extrusion.

I've disassemble the hot end, changed filament and I can't see any signs of blockage. The Bowden tube in the hotend is not showing any signs of melting etc. and it is pushed all the way down to the hotend, as per the instructions.

So, what's going with this?

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  • $\begingroup$ are you measuring an extruded amount of filament? $\endgroup$
    – profesor79
    Mar 22 '18 at 22:12
  • $\begingroup$ i followed this: www.instructables.com/id/How-to-calibrate-the-Extruder-on-your-3d-Printer/ Basically, measure the filament going in, mark it for 100mm, extrude 100mm and see where you mark is (on the incoming filament). $\endgroup$
    – cbrulak
    Mar 22 '18 at 22:47
  • $\begingroup$ how long is the ptf tube? do you hear any clicks during extrusion? $\endgroup$
    – profesor79
    Mar 22 '18 at 22:53
  • $\begingroup$ ptf tube is pretty long. And i don't hear clicks. $\endgroup$
    – cbrulak
    Mar 22 '18 at 23:09
  • $\begingroup$ are you sure the gear attached to the extruder stepper motor is screwed tight? I had an under-extrusion problem with my Anet A8, which was caused by a loose extrusion gear that was slipping over the motor shaft. $\endgroup$
    – Tooniis
    Mar 23 '18 at 9:58
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Summarizing for correct understanding: you measured 100 mm without the hotend heated and attached and about 50mm attached and at temperature but not hearing any clicks using a pretty long Bowden tube?

Bowden setups require a little more torque to push the filament all the way to the hotend. I've experienced this with my own 2.85 mm setup when I converted a 1.75 mm BullDog extruder to accept 2.85 mm filament. Your problem is most probably caused by filament not being gripped by the extruder gear and causing slipping on the filament (this does not necessarily mean that you hear clicking!). The Titan is a geared extruder so you should get more torque than a direct setup; this is exactly why you don't hear clicking, the gear turns but does not move the filament. Please inspect your filament after the extruder by removing the Bowden tube; ideally this should show you a regular pattern of the extruder gear.

What you can do to prevent this is to put more pressure on the filament by adjusting the pressure of the spring. In my setup I use some screws to get the spring out of the equation and clamp it directly only tightening the screws by hand (when switching filament I need to unscrew these).

You should also PID tune your hotend to be sure that the heater is optimally tuned to keep the hotend at a certain temperature level.

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I did a test on 50cm ptf tube, and according to result I had to increase steps/mm to 440. Thet tube have a straight connection between extruder and hotend.

  1. Please verify that there is no bends on the the ptf tube as that is huge obstacle to push for extruder
  2. If you have a short piece of ptf tube - please calibrate and compare results,
  3. Validate electrical connections as a very little loose can lead to missed steps
  4. Put a marks on the plastic gear on titan and observe if there is a smooth movement during extrusion
  5. Put a marks on the filament in about 5mm and observe how it is consumed
  6. Very that filament is easily provided from spool, and spool rotates freely
  7. Do a test on prepared piece of filament to validate previous
  8. There is a thing on tingverse that is cleaning filament and oiling it to decrease the inner tube tension, or just put some drops kitchen oil on the filament and in the tube
  9. Replace stepper motor with one of the axis as there ale all same shiped with tarantula
  10. Increase hotend temperature by 5,10, or more

  11. Add more tension on the extruder regulator

I think I exhausted my check list, as I was struggling a lot with my tarantula, and found it very brittle to use.

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