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E1 extruder motor harness broke a wire at the crimp.
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Description

Quiver 1 came back with a broken motor wire it looks like this:

There are a couple theories as to why this happened:

  1. The wires are interfering with the x-motor mount at the x-home position. This effect is worst on some machines than others.
  2. The repeated bending stresses on the wire during toolhead actuation are concentrated at the crimped termination. This was originally reported in T3429.
  3. the microfit 3.0 connector is oriented horizontal and the JST is oriented vertical but all the wire lengths are the same resulting in more stress on the far (white) wire.

Event Timeline

kent created this task.Mar 14 2019, 8:54 AM
kent triaged this task as Normal priority.
Steven added a subscriber: Steven.Mar 14 2019, 8:57 AM

@kent do you have a photo of the cabling before the ties were removed? In the photo provided there is no zip tie to strap the motor wires to the rest of the cabling.

kent added a comment.Mar 14 2019, 9:44 AM

@Steven Here is an image @matth took from before it was taken apart.

kent changed the edit policy from "All Users" to "LulzBot Hardware Products (Project)".Mar 14 2019, 10:31 AM

@kent it looks like that was crimped incorrectly. It doesn't appear to have broken or come loose at the insulation which would mean the insulation was not crimped into the pin from what I can see.

kent added a comment.Mar 14 2019, 2:12 PM

It is hard to tell from the pictures, but I took a closer look and the crimp appears to be done as intended/expected. If you look closely, you can see the indentation in the insulation in the first photo in this thread. I'll see if I can get some better photos.

I circled in red where you can see the evidence of the crimp being installed onto the insulation. It's pretty tiny, but it is there. It doesn't take too much repeated wiggling and tugging before the insulation pops out on these JST's since there is so little engagement even on a "perfect" crimp.

There is another picture of the crimp itself where you can see the remains of the broken conductor strands in there.

kent reassigned this task from kent to Steven.Tue, Apr 2, 8:07 AM
Steven reassigned this task from Steven to west.Fri, Apr 12, 7:57 AM
Steven added a subscriber: west.

@west there is no certainty if this will be a larger issue once printers are in the field but we should at least get a few alternatives considered if the change needs to be made quickly.

tutley added a subscriber: tutley.Fri, Apr 12, 8:06 AM

we may want to add 5mm or so to that side of the harness for some additional slack. In the photo it appears those wires are pulled pretty tight. Also in the photo they are bending around the end of the sleeving, where we can have the motor wires come out of the side of the sleeving to alleviate this hard turn.