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Author Topic: Big Power Amplifier  (Read 3713 times)

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Big Power Amplifier
« on: December 15, 2010, 05:20:05 PM »
Hello World,
I'm a big fan of Mach3, on my Tormach Mill and my sefl-built CNC router table.  Now I'm building a 'real' machine, a 20' long Plasma Pipe Cutting Machine.  The rotary axis rotates a 1500 lb pipe, this calls for real motors and real amps.  Question, do any of you know of a drive system in this power leauge that will interface with Mach3, given it's printer port means of communication?
Thanks to all,

Offline Hood

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Re: Big Power Amplifier
« Reply #1 on: December 15, 2010, 05:30:49 PM »
Depends on the size you need and your budget. I use Allen Bradley DSD drives on my machines, the spindle on my lathe has a 12.5KW motor with a 22KW drive, cost of these new would be in the region of £8000 ($12,500) but I bought mine off eBay for £420

So what do you reckon is the size of motor you would need?
I would imagine you could gear the motor as I suspect the rotation wouldnt have to be anything like the speed of a big servo (2000rpm or so)

Hood
Re: Big Power Amplifier
« Reply #2 on: December 15, 2010, 05:44:37 PM »
Thanks for the quick (instant) reply.  You're right, I can gear the rotary down, but I also have a long X axis to move the torch on and I want to keep all the equipment apples to apples.  I haven't determined the final power needed yet but it's more than 'hobby'.  So these drives have a printer port means of communication?  I'll look into these immediately.
How do you have time for biz, as much as I see you on this forum?  But glad you are!
Thanks again,

Offline Hood

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Re: Big Power Amplifier
« Reply #3 on: December 15, 2010, 06:00:19 PM »
Most modern servo drives can be used with Step/Dir input, lots of people use Yaskawa and Omron but you also have the chinese ones on the market now as well as the SureServo from automation direct.

Wouldnt worry about having different gearing and motor sizes on different axis, its normal practice and as each axis drive/motor is tuned they will work exactly the same. I do prefer to keep the same make of drives on each axis but thats just a personal preference as theoretically it should not make a difference as long as you have them tuned correctly.

I use the SmoothStepper rather than the parallel port, it basically takes the places of the parallel port and does the pulsing rather than the computer having to do it and it can pulse up to 4MHz where the PP is 100KHz max and usually 60 or lower to be safe.

Your other option would be to use old (dumb style) analogue amps and use something like the DSPMC of Galil or Kflop/Kanalog to interface to Mach.

Hood
Re: Big Power Amplifier
« Reply #4 on: December 15, 2010, 07:17:55 PM »
Once again, thanks.
Didn't make myself clear enough, not worried about different ratios, speeds, sizes of motors on the various axis on the same machine, just want to keep the same hardware, electronics, like you say.  Less to sort out, less to remember.  How does SmoothStepper deal with THC, well I hope?  Forget the analog, I'm a believer.
Thanks again,

Offline Hood

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Re: Big Power Amplifier
« Reply #5 on: December 15, 2010, 07:39:25 PM »
THC doesnt work in SS at this point in time, or at least I think its still the case.
Hood
Re: Big Power Amplifier
« Reply #6 on: December 17, 2010, 09:03:48 AM »
One more question/clarification on this topic please.  So your PC's output is to the SS and the motors talk to the AB drives, what is the interface do you use between the SS and drives in this setup?
Once again, thanks for your help on this,

Offline Hood

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Re: Big Power Amplifier
« Reply #7 on: December 17, 2010, 09:14:12 AM »
The SS sends out Step/Dir signals to my breakout board then on to the  drive and the drive then commands the motor to move as per the instructions it has received (Step/Dir)
The step/dir signals from the SS are single ended and the drives can accept them but it can also accept differential inputs so I prefer to use them. I made up a small circuit board with line drivers which plugs directly into my breakout board so the step/dir signals come from SS to Breakout then get turned into differential Step/Dir signals (Step+/Step-, Dir+/Dir-) and they go to my drives.

Differential signals are much less likely to suffer from noise so thats why I use them when the drives can accept them.


The other I/O to the drive I work via my PLC as it can talk direct to Mach via Modbus and output/receive 24v I/O from/to the drive. If no PLC is used then relays or some other form voltage converter could be used to lower/increase the voltage.

Hood
Re: Big Power Amplifier
« Reply #8 on: December 17, 2010, 09:32:49 AM »
So to clarify; The SS sends out single ended signals and you had to build a board that converted them into differential, step and direction + and -, as they leave your breakout board in route to the drives.
Can you recommend a breakout board up to the task?

Very appreciated, thank you

Offline Hood

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Re: Big Power Amplifier
« Reply #9 on: December 17, 2010, 09:53:48 AM »
I use the PMDX 122 breakout on all my machines and would certainly recommend PMDX boards as I think they are top quality. They also do a board now that the SS fits onto which many now go for.

The differential signals are not a necessity but to me it is preferred especially as the drives can accept them.

Hood