Monday, July 20, 2015

Automatic Spindle Speed Control for my CNC

One of the issues I always had with my small CNC 3040 was that I had to manually set the spindle speed in the frequency drive using a knob and chuting the  speed with a tachometer. Each tool change or job type (rough or fine) requires different spindl;e speeds.

I found in EBay a small electronic board that converts Pulse Width Modulation to an Analog voltage. It is possible to set the Match 3 software (this is the software that controls my CNC) to output a PWM signal in one of the port pins. The frequency drive can also be set to use a 0 to 10 volts signal to set the motor speed.

This is the link

It has some good information in how to calibrate the output.

Below is the small PC board as I installed in the control unit. The circuit needs 24 volts for power that are available in the control’s power supply.


The 0-10 volts output are should be connected to the analog input on the frequency drive:


The PWM input signal to the new circuit should be connected to one of the output pins. in my case I used the A axis on the CNC control board hat corresponds to the output pin 9.


On the mach 3 software it is necessary to adjust the following settings:




The last part is to set the frequency drive parameters to allow speed control via the analog input. The drive of my machine is a Chinese HUANYANG ELECTRIC


I spent a lot of time searching in the Internet for a manual until I found it in a Chinese site. Thanks to Google automatic page translate!

These  are the parameters to change:



PD0000 set to 1 to be able to make changes

Pd002 set to 1 to use the external terminal


PD070 set to 0 to use 0-10V control

Once it is running it is necessary to calibrate the output using the potentiometer in the new circuit

The system works OK although it is not very linear but for milling plastics, wood and soft metals it is OK. I am very happy and it is working really good and helping me to avoid mistakes.



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