Manual TPU Feeder V1

Why I made this

I print a lot of TPU 90A and I keep it in a drybox with a bowden line running to the

printer. Loading it is the worst part. Soft filament buckles the moment you push it,

so you end up standing there feeding it a centimetre at a time, and if you let the

printer's extruder pull it in instead you are waiting several minutes.

So I went looking for a manual feeder. I found plenty. None of them did what I needed.

They all have the same problem: the drive gear is always clamped. That is fine while

you are loading, but the moment the print starts, that same grip is dragging on the

filament the printer is trying to pull. With TPU that is exactly what you do not want.

A couple of designs had a release, but they released by loosening a screw - which means

you are unscrewing and re-screwing the same plastic thread every single print, and it

will strip.

I could not find anything that just worked, so I designed my own.

What it does

One lever, two positions.

Clamped - flip the dial until it clicks past the stop. A roller pushes the filament

up into a 16-tooth drive wheel and holds it there with about 55 N. Turn the big knurled

wheel and the teeth bite the TPU and drive it down the tube. The whole bowden run loads

in seconds.

Released - flip the dial back. The roller drops 1.9 mm clear. Nothing is touching

the filament any more. The printer pulls through a plain 4.2 mm channel with zero extra

drag, exactly as if the feeder were not there.

No screw to undo. No spring to fit. Two M3 screws hold the whole thing together and

that is the entire hardware list.

Print it in PETG

Not PLA. This matters more than usual, because the arm is not just a lever - the narrow

section between the pivot and the tail is the spring. It flexes about 3 mm every time

you close the lever. In PETG that works out at 32 MPa, which the material handles fine.

PLA is roughly 1.75× stiffer, so the same deflection becomes about 56 MPa and the beam

cracks, usually after a handful of cycles.

PCTG and ABS are fine too. Everything else prints in whatever you like.

Specs

Size: 74 × 43 × 23.5 mm, free-standing, sits inline on the tube

Filament: 1.75 mm - tuned for TPU 90A, works with anything

Connections: 2 × PC4-M6 push-fit - M6 thread, not M10

Clamp force: 55 N at the roller

Release clearance: 1.9 mm below the filament

Hardware: 2 × M3×10 |

Supports: none, anywhere

Material: about 50–60 g of PETG