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I know extremely little about control electronics, so maybe this is a dumb question. Is it possible to hook up a MPG to a knee mill with power feed (60v DC servos)? Or do MPGs only work with a CNC controller/servo drives on board? In other words, how hard would it be to setup the wheel seen on most MPG to run a servo motor in steps/continuously?
Hi,
yes you could run a servo from an MPG, depending on the servo of course. If the servo is an older analogue type then you need an analog output motion controller and suddenly your looking
at a substantial investment approaching a CNC control. If however the servo, or a the stepper, if it is a stepper, is Step/Direction controlled then something like a simple PLC or maybe
an Arduino type microcontroller could supply the required pulses to the servo/stepper drive and monitor an MPG. This would be in the nature of a DIY electronics project but could
be done for under $50. A PLC might cost a few hundred.
There are quite a few hobby CNC setups that are very low cost, many of which could be used...even if quite a bit of the controllers capability is left on the table.
Craig
Hi Craig, thanks for the reply. The machine was originally a CNC knee mill, but when the control died I could not justify spending the time/money to build a new control, I also did not feel like I had the expertise to put a control like that together either. Anyhow, I figured I could just put speed controllers on the motors and run the machine like a manual with power feed.
A pendent would be even better then just fwd/rev and speed control on the motors though, at least that would give me some fine control if I could get it to pulse .01" or something with each click of the pendant wheel.
The name tag on the motors on the xyz axis shows this. Not sure if that tells you if they are analogue or not.
HEDS-5500#A06 encoder
DC servo
.25 HP
3.75A
63vdc
2000rpm
The old drive boards had delaminated, so there are currently no servo drives. If those are required for an MPG, it would probably put the MPG idea out of my budget, since the cheapest ones I can find are $130+ each.
Hi,
(I rather suspect those servos are analog and trying to re-use them will be neither cheap or easy.) Strike that.
Actually doing a little research suggests that they may be just plain servo motors fitted with an encoder. They would be suitable for Geck0 320's. You need one per servo,
about $130 each.
The next step up is AC servos, not the old school DC types, but they'll cost around $500 each, plus you still have to control them.
You need to put a price on what you want to spend, and that will determine one, if its possible, and two, what sort of technology fits that budget.
Craig
I was trying to stay within the $300 range for the MPG project. I was either going to make my own MPG from a hand wheel/pulse generator or just buy a cheap one. If I have to get servo drives though, I think that would put this project out of my budget. I will probably just setup the machine with some speed controllers for the servos to have power feed for now.
I went down the cnc retrofit rabbit trail a while back. The servos I have are pretty underpowered for a machine of this size, so I would want to upgrade to something like the DMMtech AC servos. At about $500 each for servo+drive, ancillary electronics and a control like Acorn+software, I was looking at $2500-$3000. Quite a lot more then some switches and a $100 DC speed control and my wife was not ok with such a large expense for a hobby.
Hi,
I don't think $300 is going to cut it.
A cursory estimate is $420 for three Gecko302's, $150 power supply, $50 MPG, plus Arduino say $50 and your programming, or a PLC $500.
So you might get away with under $1000, but not by much, and more likely in the region $1000-$1250.
Craig