broken stepper wire?

[ron_churches]

Hi,

I have a 2005 PRT Alpha with ASM911AA motors. Today I received new pinions from Shopbot to replace the badly worn originals. I very carefully removed the motors in order to do the swap and made sure not to ever let the motors hang from the wires or pull on the wires in any way.

While cleaning off the old grease in preparation for the new gears I noticed the insulation leading into the motor itself had pulled away from the motors strain relief. Upon closer inspection, not only did I see the bare ground wire strand, but what looks like a white wire that was either cut back or broken. I've attached a picture of the problem but it's kind of hard to see from the photo. Is there any chance that there are unused wires in the motor harness or am I looking at sending the motor to Shopbot for repair.

I REALLY need my machine to be back up and running as I'm in the middle of cutting a large quantity of parts for my most important customer - and of course they need them NOW!

I'm hesitant to power the machine up until this question is resolved, I would really hate to do any more damage than is necessary.

Thanks,
Ron

[Brady Watson]

The white wire is part of the Alpha encoder system. It should not affect the function of the motor itself, but it *may* cause an error fault in the Oriental driver. This could cause problems if it does go into 'Alpha mode' where it needs to self correct, and it has no idea where it is in relation to the other motor.

It appears from your pic that this was not installed with proper strain relief or it got yanked. You have to yank pretty hard to pull those wires out. So when you fix/replace it, make sure you've got some slack and that it is zip tied well to the gantry.


Here's the thing...SB will most likely not repair the motor, they will sell you a replacement. You can also buy a replacement motor yourself via OrientalMotor.com for $298 - If you are dextrous and careful, you can repair the wire yourself. The hardest part will be deailing with the white plastic strain relief collar without pulling the wires off the motor. If you can get in there and repair it properly then you'll save yourself some cash. Properly means, soldering it, shrink wrapping it and buttoning it back up again.

I pulled the dust cap and strain relief block off for you so you can see what you are working with. Do not attempt to work on this with the cable plugged into the motor driver. Turn off control box and pull the motor cable from the driver. Also, DO NOT attempt to remove the screws from the pinion/shaft side of the motor - you will kill the motor because you will demagnetize it.

You'll need a good #2 screwdriver to pull off the end cap & a 2.5mm hex to remove the strain relief. Don't be scared...just be deliberate.

http://i772.photobucket.com/albums/yy8/braidmeister/Alpha.jpg

Hope that helps...

-B

[ron_churches]

Thanks for the quick reply. That's exactly what I was hoping to hear. I'm going to attempt the repair myself. Wish me luck!

[dana_swift]

From your photo, it does not look like the wires are probably broken, just the sleeve pulled out of the strain relief like Brady pointed out.

My bet is his solution will do it.

My addition is to use wire ties to provide extra support for the cable.. the inner conductors may have flexed quite a bit and no point in pushing them over the edge.

Having spare parts, including a stepper is nice if you can afford them. I bought mine from one of the forum members. Then you can replace immediately, and repair when you get a break.

D

[ron_churches]

How many wires are actually supposed to be attached to the ASM911AA motor? After dis-assembly , I've discovered 4 wires (black,white,purple,brown) which are soldered to the circular PCB, and four more (blue,yellow,green,red) which run into the motor itself. The cable has 10 wires but only 8 are used at the connector.

The broken or cut wire I initially thought was white is possibly light blue or light grey and I can see another wire which is orange that is cut or broken also. Is it possible Shopbot used a 10 conductor cable but only 8 wires were needed?

[Brady Watson]

The other 2 wires are allocated for a brake.

You should have 4 thinner wires going to the encoder PCB. (black,white,purple,brown)

You should have 4 thicker wires going to the motor windings. (blue,yellow,green,red)

Anything else is vestigal for that motor.

-B

[ron_churches]

After putting the PRT back together with new pinions, following the assembly instructions closely, I am happy to report that my bot is now cutting better than ever. As for the motor wiring - not the first time I've "repaired" something that didn't really need fixing. However, I did manage to feed the cable back through the strain relief as it should be. Thanks for the info!

Ron

[Brady Watson]

Ron - No problem! Glad you got her back up & running. If for nothing else your time spent is paying you back with peace of mind.

Now all y'all know what it looks like inside an Alpha motor ;)

-B