Author Topic: Lathe Spindle Speed Control  (Read 3469 times)

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Offline SteveK

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Lathe Spindle Speed Control
« on: August 30, 2012, 10:14:03 AM »
Hi,
I'm new to this forum.
I'm in Yahoo and have used MACH for years now.
I'm fixing up a Hardinge lathe fo CNC.
I have changed many machines but on this one I want variable speed with the work diameter.
I how know the PWM  works but it's not as straight forward as that.
The Hardinge has a variable "V" belt spindle drive like a Bridgeport mill.
There is a 575 VAC 3 phase motor driving the screw that changes the position of the variable pulleys.
I can change the 3 PH motor to a DC motor with gears, belt, whatever
Is there a way to compare RPM with the adjusting screw location?
I've been looking and I have found nothing about a variable speed spindle compared to work piece diameter.
Any help would be appreciated.

Offline Hood

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Re: Lathe Spindle Speed Control
« Reply #1 on: August 30, 2012, 10:34:30 AM »
You could probably fit a stepper or servo and then set it up as an axis, you can calculate out what position relates to what speed so that when you command a speed the motor will move the pulley to the correct position.
Hood

Offline SteveK

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Re: Lathe Spindle Speed Control
« Reply #2 on: August 30, 2012, 10:42:19 AM »
I did find another string about using macros to contol the spindle but it used firm RPMs not variable.
I don't know how to write macros.
I was trying to think of a way to use a PLC (TECO SG2-12) to compare the pulses from MACH to the pulses coming from the actual spindle and hit the realys in the PLC to make a DC motor go up or down.
Does/will MACH even do what I require? Compare work piece diameter to RPM?
I have not seen anything about this type of operation.

Offline Hood

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Re: Lathe Spindle Speed Control
« Reply #3 on: August 30, 2012, 10:50:34 AM »
Ah ok you are talking about CSS (Constant Surface Speed) Mach does it, well sort of, it doesnt work correctly unfortunately if in G95 mode which to me is really the only really useful way to use it, what happens is the axis slows or speeds when the spindle is increasing/decreasing. If in G94 then it seems to work fine but the issue then is you are not keeping a constant FPR.
It is not possible to do CSS properly in Mach3 but Mach4, I am assured, will do CSS properly.
Hood

Offline mr.c

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Re: Lathe Spindle Speed Control
« Reply #4 on: August 30, 2012, 11:07:48 AM »
I converted a Hardinge HLVH to CNC. I haven't done anything toward CSS but there are a couple of options. You could drive the spindle motor with a VFD or ,rather than changing the speed adjustment motor, wire in relays from your break out board to the 2 push button switches on the machine. If they are normally open switches(which they probably are) you could still leave those switches as functional at the machne control.
That leaves you with trying to figure out how to trigger the relays to control the speed. There are folks here that can help with that. I would be interested in that as well,though I probably will put a bigger 3 ph motor to drive the spindle and use the VFD that I use to drive my Bridgeport and other machines to drive the Hardinge. I have had issues with not enough power to the spindle with the original belt drive. Mostly a belt slippage issue. But it spoils a part and often a tool when it happens.
« Last Edit: August 30, 2012, 11:17:49 AM by mr.c »

Offline Hood

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Re: Lathe Spindle Speed Control
« Reply #5 on: August 30, 2012, 11:24:57 AM »
There have been a few Hardinge  retrofitted and I know that Wayne Weedon (fdos) did his and used a Siemens (I think) VFD and he was very happy and said there was plenty spindle power with it.
Hood

Offline SteveK

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Re: Lathe Spindle Speed Control
« Reply #6 on: August 30, 2012, 11:35:14 AM »
I've been a CNC operator for 25 years now, I couldn't think of the term CSS.
That's exactly what I want. ( I miss the high end machines)
I have a variable 1HP DC 1800 RPM motor (220VAC input) mounted in but I need the varidrive for facing large diameters and CCS makes things more automatic.
The vari drive also gives the spindle strength at low RPM.
I have the DC motor hooked up to the FWD/REV lever on the machine.
I do intend to use the limit switches in the vari drive, i believe there are a few along the way but i will use the top and bottom limits.

WHERE CAN I GET INTO THE MACH4 BETA GROUP?
I was part of the TURBO-CNC beta group before I went to MACH.

CSS would be a really neat feature on my machine.
I attached a pic of progress....
Cutting my own XL timing pulleys, only the spindle and X is done so far....

Offline SteveK

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Re: Lathe Spindle Speed Control
« Reply #7 on: August 30, 2012, 12:28:21 PM »
Now I'm leaning towards having 3 'gears' on the vari drive and using the DC drive for the actual varying
I may be able to hook up the original locating switches on the screw, there are 3 positions, i believe.
i may be able to have mach switch gears somehow.

Offline Hood

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Re: Lathe Spindle Speed Control
« Reply #8 on: August 30, 2012, 01:31:59 PM »
That would be a good option I think, I was going do do something similar on my lathe, my lathe originally had a 11Kw  induction motor which went via a gearbox that had electromagnetic clutches so I could change speeds whilst it was running but the problem was fixed ranges. I was going to fit a VFD and have the spindle speeds variable within these ranges but a 12.5Kw servo and a drive came along at the right price so I use that instead direct to the headstock. I have left the backgear in the train as I thought I may have needed it on occasion but the servo is so powerful I have never needed it.

Hood

Offline simpson36

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Re: Lathe Spindle Speed Control
« Reply #9 on: September 06, 2012, 01:07:07 PM »
Take a look at this video and see if you might get some ideas from how I implemented CSS (I called it 'AutoSpeed Mode').

What is does is collect Z or Y axis position from MACH thru ModBus and a Brain program and uses it to calculate the RPM and generates the Step/Dir stream to the 4th axis Servo drive.

You might be able to do something similar except instead of generating the step/dir signals for the spindle motor, have a lookup table for the vari drive positions and send the appropriate commands to the vari-drive actuator (be it a stepper, servo, hydraulic cylinder, solenoid, or whatever)


http://www.youtube.com/watch?v=vBLuF_F2_qs