RV4s rewire

[trev]

Well I have a machine with intermittent operation of movement. I changed all parts other than the wiring in the arm. I even replaced the wiring in the head to the arm. The problem is with the rotation of the nozzle. It skips steps and it's intermittent.

I am wondering if the best course of action at this stage would be replace the loom in the column leading to the arm. Anyone done anything like this. or worked on this wiring loom? Any recommendations for reliable wire to use to replace it?

Any info/suggestions welcome.

Trev

[Mike]

Before rewiring I'd try changing all the connectors in the path to that motor - IMO a connector is a more likely issue than a wire.
Start with big D-sub at the bottom ( I've had a pin fail & burn on this), and any of the IDC 0.1" header connectors - I've had these fail in feeders and have also replaced all the ones that connect to the stepper driver boards.

For diagnosis, as the stepper coils will have a pretty low resistance, doing a resistance measurement at the stepper control board while wiggling everything may be a way to find a bad connector.

If you have access to a thermal camera, might be worth a look around to see if you have any hotspots on connectors and cabling, which would probably be visible when not moving, as there will still be significant current in the stepper coils.

[trev]

Thanks, hopefully I can find the time soon. Want to upgrade the OTF camera at the same time

[LeoBodnar]

I don't know what RV4 head looks like but I have been looking at replacing QPlacer head PCB and the connectors were really poorly made. IDC crimp did not cut through the wire insulation in 3 out of 4 places. In fact it popped out while I was handling it.

The choice of using IDC connectors for high dynamics moving machinery is surprising.
Leo

Before rewiring I'd try changing all the connectors in the path to that motor - IMO a connector is a more likely issue than a wire.

[Mike]

I'd be interested to see some pics of the QPlacer internals - mostly just curiosity, but might be of interest to anyone else that comes across one, not that there are likely to be many ou there.
 

[LeoBodnar]

I have a lot of pictures but they are mostly of details while I was working on repairs or servicing local parts. Let me know what you are interested in.

[spiyda]

Its an old thread, but I finally bit the bullet and rewired the arm on the machine I use...

I only found one fault and two almost fault,

The solid Blue wire was broken inside ... again  ..  I'd replaced part of it where it goes through the wrist joint, but this time it had broken where it goes through the elbow joint.

One almost fault was two out of seven strands remaining on one of the solder bucket terminals on the back of a D connector.

The other almost fault was that where three earth wires connect to a single solder bucket, the joint was tenuous at best and fell off when touched.

For this rewire, I used a 40 Way Pin PCB Female Socket Header Connector 2.54mm and cut it down to the lengths of the plugs..  3 x 4 way  1 x 8 way and 2 x 5 way   

The new wires were soldered on tugged to e sure they were on well and heatshrink applied..

Under the deck, where the wires were easily accessible they were soldered to the Header socket or the "D" type solder buckets,  but to be honest I cheated and connected inline to the quite a few of the wires on the larger "D" type as they were close together and a bit fiddly..  since they never move in that area, I thought it was a safe compromise.

I made one mistake on the bottom 4 way on the arm but found it by using a continuity tester to check my spare machine against the rewired machine. It tuns out it had been repaired before and the repairer had changed the wire colour inside the main column !!

If I were to do this again, I would be more methodical and map the wire positions on the arm to where they go in the various connectors under the deck..

Anyway, after all that, ( it took about 10 hours altogether) I'm now confident that there are no wiring faults and I'm hoping that the intermittent faults I'd been having are a thing of the past !

FYI there are about 23 wires that pass through the arm, I didn't have all the various colours, just 2 sets of 12 colours and some permanent markers.

For some insane reason I chose one of the hottest days of the year to do it, very relieved its over and the she still works!

[trev]

Nice update on requiring your machine. Given me a little bit more motivation to put it higher up the list of things to do. It's a good idea to inline connections to the connector already there.

[spiyda]

Nice update on requiring your machine. Given me a little bit more motivation to put it higher up the list of things to do. It's a good idea to inline connections to the connector already there.

Cheers Trev, And the good news, she is behaving much better after the rewire, she did need the tool positions re calibrated using my two ball method as she was not releasing tools after all the disturbance, but properly placed about 60 boards with no errors and no repicks.   

Chris