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TPU Filament

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bostonman:
I'm uncertain who has tried TPU filament, however, for fun, I ordered a roll, downloaded a gasket from Thingiverse, and printed it.

The settings were somewhat arbitrary based off quick research and an infill of (I believe) 40%. To my amazement, the gasket was flexible and durable. After bending it several times and tugging somewhat hard, it didn't break.

Feeding the TPU into the extruder (Anet A8) appeared to be more difficult because it's very flexible unlike PLA (the only other filament I have experience with) and kept bending as I fed it. After a minute or two I felt the filament feed further down, and, to my surprise, fed through without the need to dismantle the extruder.

After more reading, it seems TPU is good for temperatures up to 90 degrees C which makes it borderline for using as a gasket on an engine. Someone online printed gaskets for his lawnmower and did a year long test. The carburetor gasket and valve cover gasket held up fine without leaking or breaking.

I'm a bit surprised it can't handle much above 90 degrees C though because it melts at 200+ degrees C when printing. From reading, my bet is it may handle short term which makes it ideal if you're in a bind and need a small gasket such as a broken snow blower during a storm.

For anyone interested who hasn't experimented, I recommend trying this stuff for fun.

Veteran68:
I have some TPU I bought just before mothballing my 3D printer during our move in 2021, so never got a chance to try it. I *just* this weekend got the printer back up and running and dialed in. Spent most of the weekend catching up on printing backlogged items I've been needing.

I've had a direct drive extruder upgrade on the shelf now for probably a year, and I bought it mainly for the improved TPU handling. Though you can feed TPU through a traditional Bowden setup, it can be tricky and inconsistent. I have some ideas in mind for some TPU prints and look forward to trying it.

bostonman:
I don't have the Bowden hooked up, but a few articles did state it can get clogged.

The durability and flexibility impressed me. I keep several parts on hand for my snowblower including a roll of gasket material should I be in a pinch, but think it's cool this stuff can be used as a gasket.

The only conflict I didn't understand is not handling temperatures above 90 C when it prints at 200+ (I think the range is 210 to 230).

Otherwise, my initial post was to mention how fun the TPU is to print with.

Veteran68:

--- Quote from: bostonman on February 19, 2024, 05:02:09 pm ---The only conflict I didn't understand is not handling temperatures above 90 C when it prints at 200+ (I think the range is 210 to 230).

--- End quote ---

I'm not a materials engineer, but I'd assume that it's not as much about the melting point as it is about structural integrity. Being a soft material already, it's only going to get softer with heat. Using it in high-temp situations, especially where stress is applied, may well produce undesirable results even when well below the melting point.

Whales:
It's not just TPU, most of the plastics you put through a printer have 100 or more degrees C difference between the printing temperature and the maximum recommended temperature for the final part.    eg:

PLA: Print ~200, don't use above ~60
PETG: Print ~220, don't use above ~70

Reasons for this:

1. The glass transition zone is not a sudden thing, it's gradual.  The part is already softening as you raise it to even 50degC.  It's possible to extrude at 150degC if you provide enough force.

2. Layer adhesion.  Filament layers don't stick to each other well at lower temperatures.  You'll take the part off your bed and it will instantly split into many pieces.  I tried printing nylon whippersnipper line once at too low of a temp, the print looked goregous but the moment I took it off the bed it disintegrated into hundreds of sheets of blue paper (even sounded like paper)

Some plastics can have their crystal structure changed via annealing to increase temperature resistance. I have not tried this.

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