3D Printed Pocket Cat: A Practical DIY Guide

A pocket cat is a small enclosed shell with a flexible inner volume. In CAD, model the outer wall first and keep it between 2.0 mm and 3.0 mm. Below 2.0 mm the part flexes too much at the opening and the layers shear apart after a few dozen uses. Above 3.0 mm you lose the compliance that makes the part comfortable, and print time climbs without adding life.

The opening is the weak point. Give it a rolled lip with a 1.5 mm radius instead of a sharp edge. Sharp edges concentrate stress and tear at the layer lines. A radius spreads that load across several layers and roughly doubles the number of cycles the part survives before cracking.

Add a 0.6 mm chamfer on the first layer footprint. It reduces elephant-foot squeeze and makes the print easier to remove without prying. Keep the internal cavity smooth; any rib or boss inside the cavity becomes a dirt trap that you cannot reach with a brush.

TPU at 95A shore is the default for this kind of part. It bends without cracking, tolerates repeated flexing, and prints on most direct-drive extruders. Softer grades such as 85A feel better but are hard to feed through a Bowden tube and tend to string badly on small openings.

Skip PLA. It is stiff, brittle, and starts to soften near 60 °C, which is well within the range of a warm car or a hot wash. The part will not survive normal handling. PETG is a middle option: tougher than PLA, but still rigid enough that thin walls crack at the lip.

Whatever you choose, buy filament with a stated base polymer and no recycled content for a body-contact part. Cheap blends vary batch to batch, and you have no way to know what additives are in them. Ask the supplier for the safety data sheet before you print.

Run a 0.4 mm nozzle at 0.2 mm layers. Thicker layers bond poorly in TPU and delaminate when the part flexes. Wall count matters more than infill here: set three perimeters and 100% infill so the shell is solid, not a lattice. A hollow interior collects moisture and cannot be cleaned.

Slow the print to 20–30 mm/s for TPU. Fast extrusion on a flexible filament causes under-extrusion and gaps between the wall and the infill, which become crack initiation points. Keep the part cooling fan low, around 30%, so adjacent layers still bond.

Print the body with the opening facing up. This puts the layer lines perpendicular to the flexing direction and keeps the lip strong. Printing it flat gives a smoother surface finish but the lip splits along the layer seam within a few uses.

After printing, trim the seam with a deburring tool and rinse the part in warm water with mild soap. Let it dry completely before use. If you plan to store it, keep it out of direct sunlight and away from anything above 50 °C.

Our own shop runs metal additive and CNC work, and we tell people plainly: a metal pocket cat is a bad idea. Metal parts are rigid, they conduct heat quickly, and they pull heat away from skin on contact. That is uncomfortable at best.

The bigger issue is porosity. Laser powder bed fusion leaves micro-voids in the surface unless you run hot isostatic pressing and post-machining, and even then the surface is abrasive. A rough, porous surface on a body-contact part traps residue and cannot be cleaned reliably.

Cost and lead time settle the argument. A single metal print of this geometry runs through powder handling, support removal, and finishing steps that make no sense for a consumer item. Metal additive earns its place on load-bearing parts, not on this.

Where metal does fit: brackets, heat sinks, impellers, manifolds, and housings that carry structural load or need tight tolerances. If your project has moved past a personal item and into a product with a real mechanical requirement, that is the conversation worth having.