Reducing the Speed of PROXXON MF70
I had problems when I milled plastics. They melt because of high speed of my PROXXON MF70. The minimal RPMs are around 5k. So I had to slow down them.
The regulation of the speed is phase control with triac. I used simple circuit of additional RC circuit and a trimer. This way, the phase capacitor C1 is charged and discharged with additional current trough variable resistor R3 and phase voltage on C2. You can achieve 5 to 95% regulation that way.
The additional elements are soldered on the original board. There is enough space for this.
Be careful of voltage and power ratings! The values I used are
R4 150k/2W Carbon type C2 330nF/250VAC Polyester (WIMA) R3 100k/1W linear trimmer (PIHER)
Be careful when tuning! The whole board is not isolated and can cause electrical shock. Keep this in mind all the time, please.
Result
You can use audio to measure the speed. I did it.
Work
How i did so much panels manually ? Well i will explain that next time. Thanks for reading.
Boyan Petrov LZ1FOB
Not quite good simulation, but it works a little bit better.