Parker Majestic CNC surface grinder

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10 Aug 2019 20:53 - 10 Aug 2019 21:02 #141883 by Alloy Craft
I picked up a used parker majestic 6x18 surface grinder on ebay. for the price I paid i figured there was something wrong with it, and of course I was right. Mechanically it is in excellent shape, cnc system on the other hand is not. It uses Whedco ac servos and drives, the cnc controller is built into one of the servo drives and talks to an hmi. of course the program for the machine is corrupted and parker does not have a copy or support this system any more. There is a guy that used to work for them that knows these systems but his quote to just come look at it was around $5000, and he couldn't guarantee me he could fix it. So I think its time to convert this machine over to linux cnc.

The machine has ballscrews on x and y and a lead screw running through a worm gear reduction on z. I will be replacing the drives and servos to new analog ac servos and drives. The machine for some reason has a linear encoder on Y, I would like to relocate this encoder to the Z axis and feed back to linux. This means I would need to close the position loop . Im not sure how to best do this in linux. There is some play in the worm gear assembly so I imagine driving it with a servo while using the linear encoder feedback in linux could cause some issues with vibration and following errors.

Also looking for some suggestions on hardware, either mesa or pico systems. Not a lot of IO on this machine so I think some thing simple should do.
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Last edit: 10 Aug 2019 21:02 by Alloy Craft.

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11 Aug 2019 07:18 #141898 by pl7i92
the best way to go for this AC Servo systems is on a 7i77
if you like ethernet adaption think of a 7i92 driving the 7i77

can you give us a image of the Servo Drivers

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11 Aug 2019 21:48 #141932 by Alloy Craft
Here is a photo of the drives. 2 are the same and the one that is the nc controller is a different part number. I believe these will run in velocity mode, however the motors use resolvers so it kinda limits your options. Also the drives are only configurable using a serial port and CCS which I don't have.
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13 Aug 2019 18:48 #142072 by andypugh
For a resolver system I used the 5i24 + 7i49 on my lathe and I am very happy with the results.

But... My resolvers connect to LinuxCNC and I suspect that yours connect to the drives? In that case you will need to figure out if the drives output a simulated quadrature for the motion controller to use.

My lathe (and mill) use a dumb drive (8i20) and do commutation in software. This works but would probably be a retrograde step in your case if you have working drives.

The 7i49 will _not_ work if the resolver excitation is from the drives, so don't rush out and buy one...

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15 Aug 2019 17:15 #142256 by Alloy Craft
The resolvers do go into the drive, and unfortunately there is no simulated quadrature output. So they are already removed from the machine and heading to ebay. Looking at some Yaskawa drives and motors right now. On the mesa boards, is there an an advantage in latency by running a ethernet 7i92 vs a 5i25, or 6i25 card? I dont have a pc picked out yet but I was leaning toward a an intel Nuc

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15 Aug 2019 17:35 #142261 by andypugh
You could have kept the motors and replaced only the drives.

STMBL and Mesa 8i20 both work well with LinuxCNC and resolver motors.

(so much that I took an encoder off of one of my motors and fitted a resolver...)
I don't think I got a photo of the servo before I butchered it:
photos.app.goo.gl/EYRsyXFrZftsGJNBA
Is the motor with encoder and brake:
photos.app.goo.gl/iXmYxJVQnW3DMZKL8
Is the same motor without the brake and with a resolver, now somewhat shrter so that it would fit in the lathe apron.

(Sorry for the digression)

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22 Aug 2019 16:42 #142854 by Alloy Craft
The motors are samarian magnet and run resolvers that I could not find any specifications on so I decided to go with new drives and motors. I have already purchased 900 watt Yaskawa motors and drives for the machine. I know 900 watt is a bit overkill but the 900 watt was actually much cheaper than the 500 watt set up I wanted on ebay. I used these same drives on my last retrofit and they are easy to setup and have auto tune. Next I need to get my mesa stuff ordered.

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22 Aug 2019 18:24 #142869 by tommylight
How much did they cost ? And where ?

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26 Aug 2019 21:24 #143251 by Alloy Craft
The servo drives are yaskawa sgdv-7r6a01 around $250 each, the motors are sgmgv-09adc61 they were $315 each. Both found on ebay.
The following user(s) said Thank You: tommylight

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