Polymaker HT-PLA-GF Filament 1.75mm 1kg

The stiffest thing in the Polymaker range that still prints like PLA. HT-PLA-GF is glass-fibre reinforced, so it comes off the plate hard and dimensionally stable, with a dry matte surface that hides layer lines almost as well as the Matte does.

Anneal it and it holds its shape near 115°C under light load — genuinely useful for jigs, tool mounts, brackets in a warm engine bay, or anything that has previously drooped on you. Two things to sort before you order: it needs a hardened nozzle, and it will not run in an AMS Lite.

At a glance

Worth knowing

A hardened nozzle is not optional. Polymaker list it as a requirement on the data sheet, alongside annealing. Glass fibre is abrasive and will open up a brass nozzle's bore surprisingly quickly — you'll see extrusion width drift before you work out why. Hardened steel is cheap next to a ruined print farm's worth of parts.

This is the one Polymaker filament we do not recommend running in an AMS Lite. Use it from the external spool holder, or from an AMS or AMS 2 Pro.

Annealing is where the heat resistance comes from. Off the plate, heat deflection is 59.7°C at 1.8 MPa and 75.5°C at the lighter 0.45 MPa load. Thirty minutes at 100°C takes those to 84°C and 114.7°C. Thin-walled parts are better annealed at the lower end of the 80–100°C range, or they can warp.

It is stiff and it is brittle — 3794 MPa modulus and 50 MPa tensile, but only 2.8% elongation at break. It will snap rather than bend, and layer adhesion in Z is the weak axis at 23.7 MPa, so orient load-bearing features accordingly. As with HT-PLA Pro, the 148°C Vicat figure you'll see quoted is an unloaded measurement — design to the heat deflection numbers, not that one.

Storage

Polymaker specify drying at 60°C for 6 hours. Keep it sealed with fresh desiccant — glass-filled filaments pick up moisture readily and a wet spool prints rough and weak.

As filament takes on moisture you'll hear popping or hissing at the nozzle, then see stringing and rough surfaces, and eventually the strand goes brittle enough to snap in the tube. That's almost always moisture, not technique — dry it and it usually comes back.