Hot plate stirrer to dissolve PLA

I made an hot-plate with magnetic stirrer to dissolve PLA support structures with heated sodium hydroxide. It can also be used to smooth ABS prints with acetone vapors :


It is powered by a 19V / 4A laptop power supply, the "brain" of the device is an Atmel atmemga328.
The plate temperature is regulated and read using a 10k ntc thermistor, the bath temperature can also be regulated using an external temperature sensor, also a 10k ntc thermistor.

The motor is made from 4 coils wound between large washers, the coils are powered by the stepper motor driver to create a rotating magnetic field :

The stir bar is also home-made from a small magnet salvaged from a CDrom drive, two M4x10mm screws and two printed shells :

The schematics, boards, firmware source are available on the wiki page : [reprap.org]

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

And I can also use it to do some acetone vapors smoothing :

From left to right :
- raw print with 0.1mm layers
- smoothed with 2ml of acetone
- smoothed with 4ml of acetone
- smoothed with 6ml of acetone

That is beautiful work, Petrus! Excellent documentation too!

Hello, great project! Can you explain the coils a bit more detailed. Like number of turns, wire AWG...

Cheers!

Honestly, I didn't made any calculation, I took some 0.25mm diameter wire from a stepper motor, and I wound it 100 turns.