Feed Gears Slipping in Flexible TPU

walleywalker
Posts: 8
Joined: Sat Sep 08, 2018 10:02 pm

Feed Gears Slipping in Flexible TPU

Postby walleywalker » Tue Nov 06, 2018 8:34 pm

I'm trying to run Push Plastic's TPU material but my drive gears on my Pro 2 keep slipping and ruining my print. I've got my flow feed rate down to 8mm/s and it's still slipping! I even have my filament spool on a ball bearing with near no resistance.

Can more aggressive feed gears be purchased and swapped in or is this a design flaw in the Pro 2 where the distance from the feed gears to the extruder is huge?

What size gears should I get if there are replacements available?

walleywalker
Posts: 8
Joined: Sat Sep 08, 2018 10:02 pm

Re: Feed Gears Slipping in Flexible TPU

Postby walleywalker » Tue Nov 13, 2018 7:03 am

I'm come to realize that this is a design flaw, or design compromise, in the Pro2. Both L and R feed gear sets on the Pro2 are FAR more removed from the extruder head than the L feed gear set on the N2. Because of this the printer is basically acting as a bowden type extruder for both L & R heads on the Pro2, where the N2 left extruder is more setup like the traditional direct drive extrusion layout.

The very soft TPUs bind and then slip on the Pro2 (both L & R) even during loading with zero filament or spool resistance, nozzle temps up to 250C, and drive gears that have been cleaned with rubbing alcohol.

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Shelton
Posts: 273
Joined: Thu Jul 12, 2018 8:34 pm

Re: Feed Gears Slipping in Flexible TPU

Postby Shelton » Tue Nov 13, 2018 7:22 am

Pro Plus 2 and no problem with gear slipping... turn retraction off first. This is very important to print very soft materials. And adjust preload spring.

walleywalker
Posts: 8
Joined: Sat Sep 08, 2018 10:02 pm

Re: Feed Gears Slipping in Flexible TPU

Postby walleywalker » Tue Nov 13, 2018 3:05 pm

I've been running with retraction off and my preload all the way tightened.

The Push Plastic TPU is basically a wet noodle in flexablity. Maybe I should try setting slightly less soft.

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Shelton
Posts: 273
Joined: Thu Jul 12, 2018 8:34 pm

Re: Feed Gears Slipping in Flexible TPU

Postby Shelton » Tue Nov 13, 2018 3:10 pm

Gears are clean without and debris on it?

walleywalker
Posts: 8
Joined: Sat Sep 08, 2018 10:02 pm

Re: Feed Gears Slipping in Flexible TPU

Postby walleywalker » Tue Nov 13, 2018 6:59 pm

Just cleaned the gears out completely after taking the whole feeder unit apart. There was a small amount of red pigment from a earlier very powdery red TPU from the same manufacterer that I was able to clean out.

I am running fairly smooth right now! The real big difference is that I am now bypassing the bowden tubes entirely and just pulling the filament out by hand and letting it pull directly into the feeder head, making for zero friction on the filmament before the feeder gears. It's running pretty well, but this obviously is not sustainable because I have to hand pull more filament every 5 minutes or so.

I'm looking into purchasing some PTFE bowden tubing to see if it offers a low enough friction coefficient for the system to run on its own without my assistance.


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