Hi Sal,
Great! It looks like there is nothing wrong with your equipment, the PM940M nMotion and VFD are working and so is Mach3! By my count you must have about everything working the way you want it!!! Sounds like you are ready to make something cool. Congratulations!
However, since you posted the two videos, and I see your G-code changed between the two runs, I think I realize some of the confusion. You must be trying to use two different pulley set ups in Mach3. This is as should be if you are trying to have your machine calibrated to the world i.e. other folks g-code.
Clearly, the gear box label on the PM940M is screwball! The label reads: position 1 and indicates a speed from ~90 to 980 rpm and for position 2 it indicates 1000 to 3200 rpm. This is incorrect! The reading for position 1 is ok, but for position 2 it should read something like ~290 to 3200 rpm. That is, the gear knob only changes the mechanical ratio by a factor of about 3.2x. So why would the lower limit not be ~90x3.2~290. As one turns the gear knob from position 1 to position 2 the intermediate gearing is changing to make the spindle turn faster for the same motor speed. It is not magically interacting with the computer! The motor is turning at the same motor RPM range (which is a min to max as the frequency changes from the min to the max). So I prefer to think of the Mach3/nMotion signal to the VFD as simply 0 to 10 volts DC. 0 volts signal from the nMotion causes the VFD to put out an almost zero frequency 220 volt sinewave and when at 10 volts from the nMotion the VFD puts out the 220 volt drive at its maximum frequency. (I think this is around 400 cycles per second).
So in the Mach3 settings one has the choice of spindle speed settings via the choice of pulley settings. However, all these do is to cause the DC voltage going to the VFD to range. The settings in my Mach3 set up only uses a single pulley setting for a maximum speed of 1000 RPM. So Mach3/nMotion sends 10 volts to achieve the maximum spindle speed and 0 volts to cause the minimum spindle speed. So when the G-code setting is S1000 the Mach3 knows that this is the maximum speed and sends out 10 volts. For S500 it sends out 5 volts and so the spindle speed is 5/10 =1/2 of the max motor speed. With out changing any of the Mach3 setting nor any of the G-code If one moves the PM940M gear knob to position 2 the speed would be 3.2x faster.
So when I write G-code, I like to think of the S1000 value not as an actual speed, but as a percentage x 10 of the maximum possible spindle speed. When I write my G-code, I know that S1000 will cause a spindle speed of 1000 rpm when on gear box knob setting #1, but the same S1000 code will cause a spindle speed of 3200 rpm when the gear box knob setting is #2.
Additionally, I am not for sure why PM puts the lower limit on the gear box 2 position to be ~1000 rpm. Clearly, one can run it at slower speeds than 1000 rpm while the gear box is on the high setting.
My only thought on this is that motors are designed to run at 60 Hz. Not 0 nor 400 Hz. So we know that this motor will not be as efficient or have as much torque at the extreme low or high frequencies of the VFD, but as long the motor does not burn out it is ok. The motor getting hot depends more on the load that you put it under than the speed. Clearly if you try to turn the motor very slowly while the gear box is set to the high position, 2, then the motor may stall and then motor will over heat quickly. However, my guess is that when you are trying to use the high spindle rpm values (gear setting 2) you are not going to be turning large diameter tools into steel anyway! You are probably cutting wood or plastic or other soft materials.
One last comment. You may not recall, but I measured my spindle speed verses the Mach3 programmed speed. At S0 setting the spindle turns slowly, a few rpm, maybe 50. The Mach3 speed control does not really start to kick in until spindle is going at about 100 rpm. When at S1000, full speed, the spindle speed was a few percent, 5-10% off from what it was suppose to be. Likewise, while not terrible, it was not linear between the Mach3 settings and the actual speed. So, one should not worry about the exact speed all that much.
Have fun and let me know how things are going.
Dave L.
Great! It looks like there is nothing wrong with your equipment, the PM940M nMotion and VFD are working and so is Mach3! By my count you must have about everything working the way you want it!!! Sounds like you are ready to make something cool. Congratulations!
However, since you posted the two videos, and I see your G-code changed between the two runs, I think I realize some of the confusion. You must be trying to use two different pulley set ups in Mach3. This is as should be if you are trying to have your machine calibrated to the world i.e. other folks g-code.
Clearly, the gear box label on the PM940M is screwball! The label reads: position 1 and indicates a speed from ~90 to 980 rpm and for position 2 it indicates 1000 to 3200 rpm. This is incorrect! The reading for position 1 is ok, but for position 2 it should read something like ~290 to 3200 rpm. That is, the gear knob only changes the mechanical ratio by a factor of about 3.2x. So why would the lower limit not be ~90x3.2~290. As one turns the gear knob from position 1 to position 2 the intermediate gearing is changing to make the spindle turn faster for the same motor speed. It is not magically interacting with the computer! The motor is turning at the same motor RPM range (which is a min to max as the frequency changes from the min to the max). So I prefer to think of the Mach3/nMotion signal to the VFD as simply 0 to 10 volts DC. 0 volts signal from the nMotion causes the VFD to put out an almost zero frequency 220 volt sinewave and when at 10 volts from the nMotion the VFD puts out the 220 volt drive at its maximum frequency. (I think this is around 400 cycles per second).
So in the Mach3 settings one has the choice of spindle speed settings via the choice of pulley settings. However, all these do is to cause the DC voltage going to the VFD to range. The settings in my Mach3 set up only uses a single pulley setting for a maximum speed of 1000 RPM. So Mach3/nMotion sends 10 volts to achieve the maximum spindle speed and 0 volts to cause the minimum spindle speed. So when the G-code setting is S1000 the Mach3 knows that this is the maximum speed and sends out 10 volts. For S500 it sends out 5 volts and so the spindle speed is 5/10 =1/2 of the max motor speed. With out changing any of the Mach3 setting nor any of the G-code If one moves the PM940M gear knob to position 2 the speed would be 3.2x faster.
So when I write G-code, I like to think of the S1000 value not as an actual speed, but as a percentage x 10 of the maximum possible spindle speed. When I write my G-code, I know that S1000 will cause a spindle speed of 1000 rpm when on gear box knob setting #1, but the same S1000 code will cause a spindle speed of 3200 rpm when the gear box knob setting is #2.
Additionally, I am not for sure why PM puts the lower limit on the gear box 2 position to be ~1000 rpm. Clearly, one can run it at slower speeds than 1000 rpm while the gear box is on the high setting.
My only thought on this is that motors are designed to run at 60 Hz. Not 0 nor 400 Hz. So we know that this motor will not be as efficient or have as much torque at the extreme low or high frequencies of the VFD, but as long the motor does not burn out it is ok. The motor getting hot depends more on the load that you put it under than the speed. Clearly if you try to turn the motor very slowly while the gear box is set to the high position, 2, then the motor may stall and then motor will over heat quickly. However, my guess is that when you are trying to use the high spindle rpm values (gear setting 2) you are not going to be turning large diameter tools into steel anyway! You are probably cutting wood or plastic or other soft materials.
One last comment. You may not recall, but I measured my spindle speed verses the Mach3 programmed speed. At S0 setting the spindle turns slowly, a few rpm, maybe 50. The Mach3 speed control does not really start to kick in until spindle is going at about 100 rpm. When at S1000, full speed, the spindle speed was a few percent, 5-10% off from what it was suppose to be. Likewise, while not terrible, it was not linear between the Mach3 settings and the actual speed. So, one should not worry about the exact speed all that much.
Have fun and let me know how things are going.
Dave L.
