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Author Topic: manual G Code commands gives inverset spindle speed  (Read 1344 times)

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manual G Code commands gives inverset spindle speed
« on: December 10, 2017, 08:53:46 AM »
Hi Guys,
I've owned a Chinese X61500GT for a couple of years now. Using a licensed copy of Mach 3, and AKZ250 USB BOB that came with it.
Today I noticed that when I  input G code to start the spindle, ie M3 S5000, the spindle starts ok but is going ALOT faster than 5000 RPM.
If I do the same for 24000 RPM, the spindle is spinning ALOT slower than 24000 RPM, so the commands appear to be 'reversed'. How is this even possible?
I have no idea if the speeds are correct when cutting jobs as I don't have a tacho on the spindle yet?

I don't recall changing anything that may cause this and it was ok when I commissioned the Router, when I first got it.
I am using external pots to vary spindle speed and feed, so I can adjust during a run. They have always worked ok. I did have to solder another connector to the board as it onlt came with one, but that went without issues....

Does anyone have a any inkling as to what 'setting' maybe causing this?


Offline ger21

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Re: manual G Code commands gives inverset spindle speed
« Reply #1 on: December 10, 2017, 11:04:29 AM »
How is this even possible?

Is this a VFD? Is it using an analog control voltage? If so, where is the voltage coming from? And have you measured the voltage?

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Re: manual G Code commands gives inverse spindle speed
« Reply #2 on: December 11, 2017, 09:27:22 AM »
I am a CNC newbie but have some electrical knowledge..
AKZ250 appears to be outputing a 5V PWM signal to a Nowforever  VSD, which is expecting a 0 to 10V signal.
I assume that this is a 'bodgy' way to control the VSD with this BOB. I am looking into wiring in a PWM to DC converter to get more accurate speed control.

I had problems with my PC today, so I couldn't do any tests. Will try tomorrow.

Re: manual G Code commands gives inversed spindle speed
« Reply #3 on: December 16, 2017, 04:37:57 AM »
I had some time today to look at this. I went through the documentation that came with the Router and now my
'reversed' speed problem is fixed. I have no idea what caused it but it must have been something I did....