Bad Servo on KMB1 ElectroCraft 07 02 03 049

I have a set of servos that may work.

Your story sounds a little hard to believe, do you think that it was a retrofit attempt gone bad?

i

No, it was originally a CNC machine, and all the parts have Hurco tags. I think something ran into it while it was warehoused. The fiberglass cover over that motor looks different than all the rest of the paint. Like it was newer or off a different machine or something. As far as encoders its not uncommon for 20-30 year old plastic to fall apart. The encoder on the X axis looked smashed. The one on the Y axis was intact, but crumbled when I touched it. I was a little surprised that there was no encoder or even a pigtail for one on the Z axis.

You want to call me and talk about those servos? (how big, voltage, shaft size, etc)

Or if its more convenient just drop me an e-mail with motor specs/model/price to: bob(at)yumabassman(dot)com

My cell is (nine two eight) 580 - one two seven zero

Or if you don't have free long distance eight hundred 296 nine 765

It was sold as a non working machine, so I was surprised when I went to pick it up and was told that it mostly did work. I was planning on retrofitting it anyway. If any of the servo motors etc are good its really a bonus.

Bob

Ok... I found the Z-axis encoder and why I didn't see a pigtail for it. Its way up under all that heavy metal on the head on top of the ball screw rather than on the motor.

Based on your description, you don't WANT another of these motors in used condition! It will be crumbling, too. What you want to do is figure out if the motor is a standard NEMA size, or even close, and then search for other motors to fit.

Jon

A mixture of coolant and way oils is pretty hard on most plastics. There are some that seem really resistant, like used by Fanuc, but many others do deteriorate when exposed to all that muck in the typical shop.

Jon

That's good. Do you know if the busted encoders are the usual differential quadrature 5v type?

i

The encoder crumbled. Not the motor. The motor looks like it took a nasty hit. The other two motors are fine.

You want to match the four bolt pattern holding the motor on. You most likely have a size 42 (4.2 inch space) but may have a size 34. That's the two most common. It would be nice to match shaft size but its not that big a deal to make up something to fix this.

I'd for sure swap out both X and Y encoders. If Z isn't a stone bitch to get at, I'd swap it too. The plastic is the same age everywhere. I suggest USdigital.com a good source for replacement encoder kits. Get the differential, they are worth the extra $20.

I'm an empty box kind of refit guy. tear everything out and figure what you can re-use. Most likely a DC power supply and some contactors are about it. This makes ringing out your wiring out to sensors etc. easy.

I suggest AMC servo amps. make this search your friend.

Right now, there are some B25A20 amps that are perfect for your X and Y but watch for a better price. Your spindle sounds like a DC servo but double check. If servo we need to know what voltage it ran at. That B40A20 unit is a likely candidate.

These servo amps only work with EMC not Mach. I suggest EMC because of one HUGE strength over Mach. It has true servo feedback - the control knows where your machine is. Mach is an open loop stepper control.

Jon Elson is your best source for interface cards. he's been doing EMC sence before it was named.

Just my 2 cents.

Karl

Agree

Agree.

This approach worked VERY well for me.

No comment, it depends on his servos.

I am not so sure, I thought that Mach could also run servo motors also.

He also has great product support.

i

...

Pete is going to jump all over this one, so listen to his opinion also.

Mach sends out step pulses only, no feedback. A work around step to servo amp is made to use servos with Mach. A huge kludge in my opinion. I will conceed this is an opinion not held by all.

Karl

Karl Townsend fired this volley in news: snipped-for-privacy@4ax.com:

If Mach 3 does nothing more than simulate an open loop stepper when using servos, then I owe you a debt of gratitude. I was considering a Mach3 conversion kit for my R2E4. I wouldn't touch it with a ten foot pole if that is true!

Thanks.

LLoyd

I would find out, to me a CNC system that does not do servos (or use a step emulation layer) is kind of worthless. Interesting.

i

Me too, but I was working up my nerve to tackle that. I was thinking that I would save the DC power supply if I can figure out exactly what parts are it. Its got a Mitsubishi VFD also that may be salvageable.

I have been studying the AMC cards quite a bit. spent several hours reading materials and researching last night after a very informative phone call from Iggy. Thanks Iggy. I really appreciate it.

That is something I definitely need to figure out. I'm already pretty familiar with Mach, have figured out work arounds for some of its limitations, and I have confidence in my ability to setup a stable PC to run it. My first attempt at EMC was a failure. I just didn't get it. Sounds like it might be necessary to go pound on that wall some more.

I looked at several of his setups on his website last night as well.

Why do you think that? It looks like a large 3 phase motor to me. 6 leads going into it plus a ground. The Mitsubishi inverter tends to support that. It doesn't look anything like a conventional servo and its about ten times the size, LOL.

Speaking of VFDs. I had been looking at rotary phase converters to power this machine, but why not just use a 1 phase in 3 phase out VFD rated for the horsepower of the motor? It looks like the net cost would be about the same. If I empty box the machine its not going to make any difference to the rest of it.

And speaking of empty box... Any reason to keep that huge control box on that big swing arm. Seems like its just in the way.

P.S. It looks like Iggy's spare servos run to fast for this machine. Anybody else got some that might work? Yes, I have been shopping around too.

It is a 3 HP 3 phase motor.

This is DEFINITELY the way to go.

I recently helped my friend rewire a Hurco KM1 to 220v from 440v, so I know something and my memory is still fresh.

The way the KM1 works is that it is a three phase mill, but only so to run the spindle motor, the optional coolant pump and the optional chiller whatever (my friend had neither).

All control stuff runs from 1 phase ONLY. No weirdness like in other machines (say my Bridgeport) that need all three phases to run the control.

So, converting it to single phase is very easy.

If your control is bad, this becomes your only choice. Does the control boot? Got pictures?

post a pic.

I put a monitor and a drawer cabinet into mine, works great.

I sold a shipload of Fanuc A06 motors a while ago... $100 each.

i

Yea, DC power supply is easy to keep for you. In my case, it needed three phases to get DC, but you need only 1 phase.

I am also an empty box kind of guy, like Karl.

>

You are welcome. These AMC guys are also good because you can call them on the phone, ask, and speak to an intelligent human being who speaks English and is located in the US.

Their manuals are first class too.

You can get plenty of people to help you out. emc-users mailing list and myself come to mind. emc-users specifically is an awesome place to hang out.

I am personally happy too.

i

And servo transformer too, is a 1 phase thing.

i

OK, yes a VFD is the way to go. At some point you'll want a VFD brake resistor and a spindle encoder. Don't need to do this right away.

Send a link to pics of this again. I often put a flat screen monitor and keyboard on the operator input panel. I'm thinking that's what this is. If so, a jog handwheel, jog buttons and Mcode switches will be very nice future upgrades

is your existing motor beyond repair? Take it loose and put a 12 volt charger on the big leads. if it still turns you could rebuild the bearings and brushes. Or if it doesn't turn it still could be just bearings and brushes. Otherwise, ebay is your friend.

Yep, the VFD should be good.

a power supply is easy to spot. You have a transfomer then a rectifier that's nomrally a little black square box with four leads, sometimes more than one. Wires come from the AC to the transformer to the rectifier and then on to a bunch of round metal cans (capacitors)

Karl