Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Monty on January 29, 2010, 05:56:35 PM
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OK here is the issue.
I would really like to be able to have spindle positioning on my lathe. The problem is the spindle drive needs an add on card to do that and they are basically not available anymore.
It will however take a +/-10V analog signal for direction and speed.
Is there some type of card to convert step and direction to analog 10V that would allow me to put an encoder on the spindle and drive it like another axis? If so would this still work in typical turn applications. How would you get around the spindle sensing issues for threading?
Monty
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There used to be a board called the pixie that did that but its no longer made. I have heard Rutex do one but have not heard of anyone using one.
You would have to use SwapAxis() to change between spindle and axis depending on what you were wanting to do, ie positioning, rigid tapping etc you would swap spindle to A via macro, normal turning and threading you would swap back again.
Hood
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Hood,
So I would still need the 1 per rev signal for standard lathe operations? The encoder would only be useful for rigid taping etc. after swapping the axis.
First I've got to get the rest of the ghosts out of the machine.
Do you know a good Exorcist specializing in electronics? ;D
Monty
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I was presuming when you mentioned encoder that your motor is a servo and the drive can close the loop to your motor, is that correct?
Hood
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Yes,
It has an encoder. The positioning was done with an add on board. It could position either the motor or the load. depending on where you put the encoder. But I can't use any of that functionality because I can't get the board and even if I could it would be a real pain to interface.
What I had in mind was to move the PID loop to the +/-10V controller. So it would read the encoder on the spindle and move the motor to the commanded position. My drive would be a "dumb" amp at that point. The analog controller would receive speed and direction instructions from Mach. Rather inelegant I admit, but the only way I can get here from there without a new spindle drive.
Monty
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I believe this is what you need: http://pico-systems.com/spindac.html
Regards,
Ray L.
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Ray,
That would work great if mach handled PID loops within the computer. It would work with EMC. But to work with mach I've got to have something with encoder input to handle the PID loop.
It may not exist.
Oh well, I might just have to start on the 5 axis machine.
Monty
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As said Rutex do one so might be worth giving them an email. There are other options but more expensive such as the Kflop/Kanalog and DSPMC and really too expensive for just a spindle.
What kind of servo/size? might be better looking for another drive.
Hood
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Hood,
It's a Yaskawa 5.5 KW.
I can do a lot of the things I want to accomplish using the 4th axis on the Bridgeport, but it makes a terrible mess and the additional setups are a pain. It would be great to be able to do it all in one shot in the lathe with all the mess contained. Plus I can use flood coolant.
I'm not really sure it's feasible without a brake on the main spindle. I'm not sure how well the motor can maintain position under load.
I'll contact Rutex
Thanks for lead.
Monty
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If the Rutex lead doesnt go anywhere maybe keep your eyes open on eBay, I have picked up a lot of servo drives on there and the most I think I have paid was £180 for a new 22KW one.
Hood
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Monty
have just seen this on UK Ebay, not really sure about it as I have not fully read the spec sheet yet but looks like it may be worth looking into, few things I see from my initial look is 25KHz clock rate is typical, 50KHz max, so not great, also -15 0 +15v output which I am not sure if it could be scaled or not. Maybe an email to the guy would give some answers.
http://cgi.ebay.co.uk/ASERVO-server-amplifier-interface-CNC_W0QQitemZ230431000642QQcmdZViewItemQQptZUK_BOI_Industrial_Automation_Control_ET?hash=item35a6c20842
http://www.eaziform.co.uk/files/CNCComps.pdf
Hood
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Thanks Hood,
I'll check it out.
Monty
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I have been looking and it seems weird to me, seems to have at least 4 axis Step inputs but the Dir is a common pin for all, cant see how that would work.Also the -15 0 +15 seems weird as most commercial CNC is -10 0 + 10 from what I have seen, no mention of scaling it but I suppose it may be possible to do that with the motor tuning.
Hood