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Mach3 spindle RPM OFF!
« on: January 25, 2018, 05:25:52 PM »
I put M3S1000 in the MDI and the spindle turns on and runs CW (which I want) but the RPM goes to 1250rpm.  I put a magnetic sensor on the pulley so I know exactly what the spindle is really spinning in RPM.  I check it with my hand held tach as well and its right on.   Back ground on my setup.  In the C32 instructions it says to run the spindle at max RPM (4000 for spindle) and adjust the trim pot for 10VDC, I did that.  When I tell Mach3 to go too 4000RPM it goes to 4100RPM.  Very confused on how to make this RPM match the requested RPM and help or ideas would be awesome.

Tread Mill motor
2.5hp
21 tooth timing belt pulley
DC board KBMM 225D set 90vdc 1.5HP resistor

spindle set up
18 tooth timing pulley
G0704 mill spindle

System setup
C32 board  (CNC4PC)
ESS (smooth stepper)
encoder to C52 board 3rd port on the ESS(Smooth Stepper)

Frequency set to 300
PWM % 5
PWM checked

Smooth Stepper config set to PWM
Freq 300
PWM checked

Spindle Pulley settings
Pulley 1 max speed set 4000rpm
ratio set to 1
Re: Mach3 spindle RPM OFF!
« Reply #1 on: January 25, 2018, 06:38:25 PM »
Hi,
the DC voltage to frequency converter is unlikey to be that linear. As it stands you have 100 rpm error at 4000 rpm
ie 2.5% error, is that not close enough?

Craig
My wife left with my best friend...
     and I miss him!
Re: Mach3 spindle RPM OFF!
« Reply #2 on: January 25, 2018, 07:02:53 PM »
I don’t think you will get better than that with a motor to controller mismatch like that.  Are you running the motor in its normal direction? The brushes are offset for rotation in one direction only on many tread mill motors. Running backwards my treadmill motor went up in flames!
Re: Mach3 spindle RPM OFF!
« Reply #3 on: January 25, 2018, 07:04:34 PM »
I don’t think you will get better than that with a motor to controller mismatch like that.  Are you running the motor in its normal direction? The brushes are offset for rotation in one direction only on many tread mill motors. Running backwards my treadmill motor went up in flames!
Re: Mach3 spindle RPM OFF!
« Reply #4 on: January 25, 2018, 07:38:28 PM »
Oh am I bad I meant CCW not CW.  Thats what I was thinking that the mismatch would be to great.  I think the machine will be a whole lot better when I get the leeson 2.5HP motor mounted and run it with the Hitachi WJ200 VFD Through Mach3.  I will then be able to get what I want.  I tried everything that I can think of and nothing gets them to match, oh well.
Re: Mach3 spindle RPM OFF!
« Reply #5 on: January 25, 2018, 07:58:44 PM »
Hi,
an open loop controller like Mach3 is not likely to result in a really accurate speed with either a DC motor or a VFD driven
induction motor.

You could achieve very tight speed control with a servo but a 2.5hp servo and drive will set you back a pretty penny!
Do you actually need such tight speed control? Forget bragging/swaggering rights, this is about what you need not want
you want.

Craig

My wife left with my best friend...
     and I miss him!
Re: Mach3 spindle RPM OFF!
« Reply #6 on: January 25, 2018, 08:18:57 PM »
Well I know people who are getting the  speed they want using mach3 through a VFD.  Now how they are doing that I am not sure, but I do know that they are using a 3 phase motor.  Any insight would be good.
Re: Mach3 spindle RPM OFF!
« Reply #7 on: January 25, 2018, 10:38:58 PM »
Hi,
a three phase induction motor and a VFD will usually get within a few percent open loop. Beyond that level of accuracy
you have to go closed loop.

Most VFDs will accommodate an encoder and will get you to very close, an AC servo on the other hand will be accurate to
within a few thousands of a percent and will maintain ANGULAR accuracy of better than a quarter of a degree.

Still I have to ask 'Do you really need that level of accuracy', I like lots of others spent a lot of time and money trying to get
the speed spot on only to find that except in a few unusual situations it doesn't matter that much.

Craig
My wife left with my best friend...
     and I miss him!
Re: Mach3 spindle RPM OFF!
« Reply #8 on: January 25, 2018, 10:53:35 PM »
Well your right it does not but for later when I want to put a lathe together, from my understanding it needs to be spot on.  I will have to do some more research on this very subject.  Correct me if I am wrong with the 3 phase motor and the VFD combo I will be able to do rigid tapping?  From what I have read that is correct but I could of read that wrong.
Re: Mach3 spindle RPM OFF!
« Reply #9 on: January 26, 2018, 01:11:50 AM »
Hi,
have you done any turning on an ordinary lathe? If you have then you'll know that speed needs to be right but its not supercritical.

For threading on a lathe accurate speed is not that critical but a CONSTANT speed is important. Any and every time you take a cut on a lathe the spindle slows a little
bit. Trying to minimize the speed variation is the key to threading with Mach3/4.

Rigid tapping is a term more commonly applied to mills than lathes but the idea is that a spindle turns a tap, usually fairly low speed, say a few hundred rpm, and the feed
axis advances the pitch of the thread with each revolution of the tap. When the bottom of the thread is reached the spindle decelerates, the reverses and the feed axis
follows suit and backs out. Whats critical is not the speed but the angular accuracy of the synchronization of the spindle/tap and the feed axis. Ordinary DC and 3 phase
induction motors with a VFD are not really suitable, for rigid tapping you really need a servo spindle, that is to say a spindle which can maintain angular position.

Rigid tapping is pretty ambitious for a hobby machine. Single point lathe threading is achievable.
My wife left with my best friend...
     and I miss him!