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.

Step 1: Result

You can use audio to measure the speed. I did it.

Step 2: Work

How i did so much panels manually ? Well i will explain that next time. Thanks for reading.

Boyan Petrov LZ1FOB

Step 3:

Not quite good simulation, but it works a little bit better.

<p>Would be nice if you could share your LTSpice file.</p>
<p>With pleasure, but the simulation is not very correct.</p><p>The actual shape of the voltages on the capacitors is another.</p><p>I intend to do more realistic simulation, but decided it was not so important in this case. </p><p>I will attach the file as a step.</p>

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