# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DawCooqPOTI
- **Gondola URL:** https://gondola.cc/posts/67970788-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/ad0975f42e.jpg
- **Posted:** 2026-07-13T22:57:57.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

A keycap is injection-moulded to tolerances of a few hundredths of a millimetre, and you slowly destroy one every few million keystrokes without noticing.

It starts with polymer choice, and the two candidates behave nothing alike in the mould.

- ABS is amorphous. It flows beautifully, captures fine mould detail, and shrinks only 0.4 to 0.7 per cent on cooling. Its weakness is the surface: polymer chains abrade under a fingertip until the texture polishes into that greasy shine.
- PBT is semi-crystalline. Higher melting point, better solvent resistance, a drier and grainier feel. But crystallisation means it shrinks 1.5 to 2 per cent, so the steel cavity is cut deliberately oversize: the mould-maker must predict the final part before it exists.

Molten polymer enters the tool near 250 degrees, is packed under holding pressure to fight shrinkage as it solidifies, then ejected in seconds.

Then the harder problem: putting a legend on it that survives.

- Pad printing: a silicone pad lifts ink from an etched plate and stamps the cap. Cheap, sharp, and it wears off.
- Laser etching: the beam ablates the surface, leaving a recess that can be infilled. Durable, but limited to suitable resins.
- Dye sublimation: dye vapourises near 200 degrees and diffuses into the polymer matrix itself. The legend sits inside the plastic rather than on it, so it cannot wear away. It also cannot go light on dark, since you cannot sublimate white into black.
- Doubleshot: two injections. The first moulds the legend as a solid three-dimensional slug. The tool rotates, and a second shot forms the cap body around it. The character runs the full depth of the cap. To wear it off you would have to wear through the cap.

Then the cross-shaped MX stem, roughly four millimetres across with 1.2 millimetre slots, where a few hundredths decide between wobble and a split cap.

The things we touch most are the things we least look at.

#stemantics #engineering #materialsscience #manufacturing #mechanicalkeyboards

## Stats

- **Views:** 15,218
- **Likes:** 62
- **Shares:** 0
- **Comments:** 1

## Tags

engineering, materialsscience, manufacturing, stemantics, mechanicalkeyboards

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