Retrofit of Precix 5x10 CNC

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02 Mar 2020 03:01 #158930 by wefixprecix
What servo drives are you using? The original Copley's or AMC's? Pay attention to my user name. Those gold motors are Astromech's with a Renco encoder. They are very old. Precix stopped using them in 2002. They were a very problematic motor/encoder when new. I have good used and New replacements for those Astromech/Renco's. If those encoder cables running through the flexible raceways are original, I would be looking at those to be a lilely cause of your problem. I get customers calling me every month about symptoms like yours. Always to diagnose a encoder cable running through the X-axis flexible raceway as the cause. Imagine a metal coat hanger bending back and forth until it finally breaks. Now imagine that coat hanger with plastic insulation around it. Imagine what happens when the flexible raceway does the tight 180 degree bend at the point of the broken coat hanger. You can imagine how this is causing the effect you are experiencing. I can help you with cabling also. I just had a customer;s machine in my shop with the same issues. I replaced his encoder cables and his machine has been running perfectly in production for 3 weeks with without any problems. And in case you think I am FOS, I will give you his ph number and you can call him yourself to discuss what his machine was doing before and after It was repaired.
Russ.

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02 Mar 2020 04:26 #158937 by Todd Zuercher
I've delt with both failing encoders and cables. When my encoder went it was much harder to diagnose, more intermittent and random than the failing cable.

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02 Mar 2020 20:43 #159025 by randypetersen
Thanks Russ, I emailed you back in December trying to get some costs on belts. I will email you again see if you have pricing on motor/cable/belts for a 5x10 precix. So you think it's the cable? or the motor? It's pretty old, and the X axis is the only Astromech motor, the rest are Magmotor.

Thanks Todd, so what I have is also very intermittent.


I tried to move the X and Y this afternoon and the X was still dead. So I switched the connectors going into the back of the controller, then the X worked and Y was dead. So my cabling going from back of controller to MESA board was ok. Switched them back.

Then I switched the X/Y on the connection on the gantry. Then tested it and both of them now work. So it's back to working for the moment, but I am too scared to actually power it up.

I am almost inclined to replace the motor and cabling. Looking at replacing the X motor Astromech with a Magmotor like the Y axis. They aren't too expensive on ebay or if Russ can get me a deal.

Hard to figure out if it's a bad motor or cable I suppose? Since it was working for usually a week or two before it screwed up.

Anyone have any recommendation on cabling? Maybe I should replace that first.

As always, thanks for your input!

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02 Mar 2020 21:01 - 02 Mar 2020 21:03 #159029 by Todd Zuercher
I would look hardest at the cabling. Check for any obvious physical damage to the cables (kinks, pigtailing, split or worn insulation...). Can you swap just the motors between X and Y keeping the cables where they were? Then run/test the machine for a while and see if the problem follows the motor or stays with the cable. That way you can isolate whether the problem is from the motor or cable.

I've used Igus for encoder cabling they have some very nice stuff. Replacing encoder plugs by hand is a pain, so if you can buy your cables pre-made it is usually money well spent.
Last edit: 02 Mar 2020 21:03 by Todd Zuercher.

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02 Mar 2020 21:06 #159030 by randypetersen
Ha! I just was on their website, read some good things about them on another forum. Thanks Todd!

I got a decent soldering station here and think I could do it, but I will look at premade ones as well.

After thinking about it for a while I am thinking more and more it's cabling. Seems like happens more often when I am running the X by itself during a long run, like a homing.

I will take the cable out and inspect it. I will probably look at getting some replacement cable. I think the cables have 15 pins but I am only using about half for the encoder.

Wonder when I build new cable could I run 2 wires for each encoder in case one dies? :)

I could also switch wires for the X/Y and see if it dies on the Y, that would be a good test, just not sure if I want to push GO on the machine with it acting up.

THANKS!

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02 Mar 2020 21:15 #159035 by Todd Zuercher
On the machine's I've worked with it is usually less work to swap motors than it is the cables. (large routers)

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02 Mar 2020 23:49 #159049 by randypetersen
Yep, replacing a motor might be less work. Actually I checked the spare parts box the guy gave me when I got the machine and he had a replacement "astromech" motor which has a post-it note saying "Good" on it. So I can replace that and switch the X and Y wires then if the Y fails I'll know it's a bad cable.

I hate losing control of the machine though, I might just buy the cable and replace the encoder cables as well.

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05 Mar 2020 13:56 #159254 by andypugh
It's a lot of posts to go back through, so forgive me if this has been mentioned, but it might be worth hooking up the quadrature-error outputs (if you are using a Mesa card) to give a chance of detecting _some_ cabling or encoder errors.

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05 Mar 2020 14:03 #159255 by randypetersen
Thanks Andy!

Why didn't I think of that? I am using the Mesa 7i77 and 7i92m boards.

Give me a minute while I look up what "quadrature-error outputs" are. :)

thanks,
Randy

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05 Mar 2020 14:14 #159257 by andypugh
Note that it won't detect a single missing channel, and in that case a fast-moving axis will look like a static dithering axis, so might still run away.
You could also look at connecting the pid,N.saturated output, which will catch another class of problems.

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