TPU Fail or no?

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dseebauer
Plasticator
Posts: 7
Joined: Fri Sep 05, 2014 2:32 pm

TPU Fail or no?

Postby dseebauer » Wed Jul 25, 2018 11:07 pm

Hi All,

I was recently trying to print some TPU for the first time. Well I did print a couple calibration cubes when I first got it, but then it sat around a for a while. The first cube I printed was great (for a cube anyway). The layering was nice and the resin was some what clear (translucent green).

I am using SainSmart generic TPU in translucent green. ( https://www.amazon.com/dp/B00TI3JUSI/re ... B072LYRQ84 )

Recently I was trying to print a much more complicated model to see what was possible. However, I had a lot of trouble getting it to extrude this time around. At the beginning with TPU, I had to replace my EZStruder with a modified Thingiverse extruder to even do the cubes and now trying again with that setup (which prints PLA and ABS pretty well) I had a very hard time getting anything out. The parts finally printed, however the quality was horrible, and I had to dial up the flow rate to about 150% to get them done. Below is a link for some images of what I ended up with. As you can see there is a ton of artifact from the support removal as well from the heavy stringing. The images are from after cleaning them up. I should have take a pic of them before support removal, sorry.

https://imgur.com/a/6VNml6N

My question is this. How typical is this of the resin type? I am guessing no based on all the great images I see on the interwebs. If it is not typical, I am hoping to get some advice for the next project. I printed these at 235C, 50C Bed, 100% fill after drying the material for about 5 hours at 140F in a convection oven. FWIW, I have a stock PEEK hotend. I did notice this material drewls a lot at that temp, but lower and it would not extrude.

Thanks in advance!!
Dave

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rootboy
Printmaster!
Posts: 213
Joined: Wed Mar 12, 2014 2:34 am
Location: Lewisburg, Tennessee

Re: TPU Fail or no?

Postby rootboy » Mon Aug 20, 2018 2:09 am

I did notice this material drewls a lot at that temp, but lower and it would not extrude.


That's a sign of moisture in your filament. Try upping the drying temp or the drying time. Just be sure to keep the oven under TPU's Glass Transition temp (AKA, melting point).

We use a Dremel 3D Digilab 3D45 at work, and printing in nylon was impossible after the roll have been out of the bag for a few days (even with it resealed in a baggie with desiccant bags). So I bought a metal ammo can from Tractor Supply that would hold two *Dremel* spools at a time (the Dremel spools are just over 7", a normal spool is about 8"), and I "modded" a 240 volt heating element to run at 30 volts (we have tons of these heating elements here at work, so it was handy). I limit the temp to "cozy warm", no danger of it overheating at all. Total cost, about ten bucks.


For home, I just bought a toaster oven that will hold the bigger spools that we use:
https://www.amazon.com/gp/product/B078S ... XFS4&psc=1

I'll mod it to limit its max temperature to no more than 150F and just leave it running (outside, preferably).


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