What is a press mold used for?

Materials that are packable rather than pourable: clay, bath bombs, cold-process soap, compressed powders and shredded plastic. You pack the die, press the piston, and eject. If your material is liquid, use a pour mold instead.

Why do my bath bombs crumble when ejected?

The mix is too dry, or it was not packed hard enough. The target is barely damp, just holding together when squeezed in your hand. Pack in layers, pressing between each, and press slowly holding at the end rather than squeezing quickly.

Why are my parts different heights each time?

Inconsistent packing rather than a mold fault. Weigh the charge for each press instead of filling by eye, and apply the same pressure each time.

What filament should I print the die in?

PETG with 4 perimeters and 30 to 40% infill. Pressing applies real force, especially with compressed powders, and a die that flexes gives inconsistent parts while an under-built one cracks.

How do I stop the part sticking in the die?

Dust the cavity with cornflour, or wipe a trace of oil in it for clay. Sanding the cavity smooth once helps every press after that, since rough printed walls grip more.

Press Mold Generator · Free STL Mold Maker

Press Mold Generator: die + piston press mold for clay, soap & bath bombs

Upload an STL, OBJ or 3MF to begin

Get a print-ready press mold: a die & piston, for clay, soap & bath bombs

Generating mold…

What a press mold is

A press mold is a matched die and piston pair. You pack the die with a material that is stiff rather than pourable, press the piston down, and the material takes the shape of the cavity. Nothing is poured and nothing cures in the mold, so you can turn a batch out one after another.

This is the right tool for packable materials: clay, bath bombs, cold-process soap, compressed powders, shredded plastic. If your material is liquid, you want a pour mold instead.

How it works

Pick a shape or upload your own, round or rectangular.
Set the size and the depth of the cavity, which decides how much material each press takes.
Print the die and the piston. They are generated as a matched pair with clearance already built in.
Pack, press firmly, then push the piston through from the back to eject.

Packing well

Overfill slightly. Material compacts under the piston, so a level fill gives you a short part.
Pack in layers for anything crumbly, pressing between each, rather than filling and pressing once.
Press slowly and hold. A quick squeeze traps air pockets that split the part as it dries.
Bath bombs want to be barely damp. Too wet and they activate in the mold; too dry and they crumble on ejection.

Print settings

Setting	Use	Why
Walls	4 perimeters	The die takes real force on every press
Infill	30 to 40%	A die that flexes gives inconsistent parts
Layer height	0.16 to 0.2 mm	The cavity finish transfers to the part
Material	PETG	Stiffer than PLA and survives repeated pressing
Orientation	Cavity opening upward	No supports inside the cavity, which is the surface that matters

Common problems

The part crumbles when I eject it

Usually too dry, or not packed hard enough. Add a little moisture, pack in layers, and press slowly holding at the end. For bath bombs the target is barely damp, holding together when squeezed in your hand.

It sticks in the die

Dust the cavity with cornflour, or wipe it with a trace of oil for clay. Rough printed walls grip more than smooth ones, so sanding the cavity once helps every press after it.

The parts come out different heights

Inconsistent packing rather than a mold problem. Weigh the charge for each press instead of filling by eye, and use the same pressure each time.

The die cracked

Not enough wall or infill for the force you are applying. Reprint in PETG with 4 perimeters and 30 to 40% infill. Pressing is surprisingly high-force, especially for compressed powders.

Related tools

Two-part pour mold Silicone mold housing Cookie & clay cutter Texture roller Full press mold guide