PA-CF vs TPU: picking the right filament for a UTV part

Every part we sell starts with the same question: is this thing supposed to hold a shape, or absorb a hit? That single answer picks the filament, and getting it wrong is how you end up with a bracket that cracks on the first cattle guard.

PA-CF — carbon-filled nylon — is our default for anything structural. Radio covers, gauge pods, clamp mounts. It is dimensionally stable through the heat-soak a dash sees in August, it resists the ester-based cleaners people spray on interiors, and the carbon fill dramatically reduces warp on long flat panels. The tradeoff is that PA-CF is hygroscopic. It drinks moisture out of the air, and a wet spool prints stringy, weak parts. We dry every spool for 8 hours at 70°C and print out of a heated dry box, which is genuinely half the reason our parts fit.

TPU is the opposite tool. It is a rubber, not a plastic, and its job is to survive deflection. Grommets, shims, trim edging, anything that gets clamped or pinched. A TPU part will bend to 90 degrees and come back; a PA-CF part in the same spot snaps. But TPU has no business being a load-bearing bracket — it creeps under sustained load, so a whip mount printed in TPU will slowly droop over a season.

The failure mode we watch for is not strength, it is fatigue. Off-road loading is not one big hit — it is ten thousand small ones. PA-CF handles high-cycle vibration well as long as the wall is thick enough that the load path never runs through infill. That is why our clamp mounts run 1.4 mm walls: not for peak strength, but so the fastener bosses never see a hollow section.

What we do not use: PLA anywhere on a machine, ever. It has a glass transition around 60°C, and a black dash in the sun will pass that on a warm afternoon. If someone is selling you a PLA dash part cheap, that is why it is cheap.