# Paraffin wax becomes a precision linear actuator

Melt a block of paraffin with a TEC, let it push on a hydraulic cylinder, and you get a micrometer-level actuator. BubsBuilds calls it a "waxtuator."

- Category: Hardware (build)
- Made by: [BubsBuilds](https://www.youtube.com/watch?v=KF2R5GGfRHM) on YouTube
- Original: https://www.youtube.com/watch?v=KF2R5GGfRHM
- On Afterware: https://afterware.xyz/p/paraffin-wax-becomes-a-precision-linear-actuator

## Can I build this?

- Difficulty: Advanced
- AI-buildability: 2/5 (Most of the work is machining an aluminium block, sealing a hydraulic system and degassing wax, with only the temperature control and sensor logging being code AI can write.)
- Time: A few weeks
- Cost: $150–400
- Parts: Paraffin wax, TEC element, Aluminium block, Hydraulic cylinder, Displacement sensor
- Tools: CNC or machining tools, Vacuum degassing setup, Temperature controller

Estimates based on the original write-up. How the AI-buildability score works: https://afterware.xyz/ai-buildability

## Starter prompt

```
Based on "Paraffin wax becomes a precision linear actuator" on Afterware: https://afterware.xyz/p/paraffin-wax-becomes-a-precision-linear-actuator

Write firmware for an ESP32-C3 that drives a TEC through a MOSFET H-bridge with PID control. Read temperature from a thermistor on an aluminium block and a displacement sensor on a hydraulic cylinder. Log position against temperature and hold the cylinder at a setpoint.
```

## Story

Paraffin wax expands about 1.15 times in volume when it goes from solid to molten. BubsBuilds characterized that expansion across the full solid-to-liquid temperature range and turned it into a controllable actuator. In his tests, a gap of less than 5 µm held steady over twelve hours, as long as the wax temperature stayed controlled.

Paraffin conducts heat poorly, so the build runs multiple channels through an aluminium block and melts the wax with a TEC element. The wax presses on a working fluid, which pushes a hydraulic cylinder. Water worked at first but fought the wax at the interface and caused trouble during vacuum degassing. Ethylene glycol was a better fluid but brought its own hassles. The water version used a displacement sensor to calibrate the whole setup.

## Resources

- [Build video](https://www.youtube.com/watch?v=KF2R5GGfRHM)

Tags: wax motor, paraffin, thermoelectric cooler, hydraulic, linear actuator, precision

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