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Problem with spindle speed
« on: June 25, 2020, 11:22:52 AM »

I am new to the world of CNCs and really know nothing about it. The last few months have been such a steep learning curve but I really enjoy it! I purchased a CNC router around 8 years ago and didn't do anything with it. This year I decided to set it up.

First thing I did was change the BOB because I wanted USB compatibility. I then changed the inverter because somewhere along the way I fried it. I then spent around 2 months trying to get the inverter to work with the spindle.

Now all is done, inverter is set up nicely, spindle works flawlessly and computer is finally connected to the inverter and can control the spindle.

My main issue now is:

1) I have set the minimum frequency of my inverter to 120Hz and max at 400Hz. When I switch the spindle on in mach3, it ramps up to the displayed frequency. However, once I increase the frequency above roughly 270Hz, it will not go below it. That gives me a spindle frequency range of 270-400Hz only. The strange thing is that if I started it at 0% which is 120Hz, it will remain at that frequency and anything below 270Hz I will be able to go back down to 120Hz.
2) After I increase the freq and come back down to 270Hz, the speed fluctuates when it is around 270Hz.

I have done no setup to mach3 spindle settings, don't really know where to start. Would appreciate any help in this issue.

Offline reuelt

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Re: Problem with spindle speed
« Reply #1 on: September 14, 2020, 02:59:16 AM »
I am guessing you are using an AIR COOLED spindle rather than a WATER COOLED spindle.

Min RPM of an AIR COOLED spindle is 16,000
Which is correct exactly 270/400 x 24,000 RPM.

The FAN of an AIR COOLED spindle cannot run slower because, it cannot cool the motor. So the minimum FAN speed restricted the minimum speed of the Spindle.

If you are using a Water Cooled Spindle, your water pump must be big enough.
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