Intermittent endstop problem (Taz 6)

The latest problem I’m having with my Taz 6 is intermittent false endstop triggers while printing. It seems to be happening primarily on the Y-axis but it has happened on the X-axis a few times as well.

Here are the details of the problem I’m having:
Let’s say I try to print something in the small to medium range (relative to the maximum envelope) that I’ve printed many times before. It may work flawlessly the first time. Then the next time I try to print it it will start off fine then midway through the print (different points each time) one of the endstops (usually the Y-axis) will send a false trigger message (confirmed by digital readout) which locks the movement along that axis but the print will attempt to continue spewing filament all over the place (see picture attached). In some cases if I immediately try running the same print again it will work. In some cases it will take 2 or 3 tries. Sometimes I give up.

Here is the troubleshooting I’ve done so far:

  • Tested endstops with multimeter. All showed good.
  • Tested endstops by commanding table to move and manually triggering them. All functioned normally.
  • Verified spade connections at each endstop are in place and tight
  • Verified all exposed wire harness connections are in place and tight
  • Verified no apparent damage to any wiring outside control box
  • Verified no snags occuring to wiring throughout full motion of the table

So what’s next? Has anyone else had this problem?

Have you tried checking limit switch continuity by checking continuity at rambo connection while someone moves the bed forwards and backwards?

When my heater wire went bad, it was a stress fracture. The shielding was still there but the wire had broken inside. It would give good contact in all positions except for one position when the wire was bent in the right place when the bed was in a specific location.

It’s something to try and I know it’s how I found my issue.

I’ve never seen or heard of a Taz doing that, 6 or otherwise. I would have it replaced under warranty. If it’s on the Y axis, its one of the two limit switches on the bed belt mount itself, which go through a moving wireing harness. I would suspect an actual wiring fault possibly, or maybe a bent connector pin in intermittent contact? The bed wiring is fairly straightforward, you can see the whole path here and it’s a very simple circuit. Something would have to be physically closing that loop to trigger it. Have you replaced the limit switches? I’m wondering if rapid print speeds coupled with a weak limit switch spring internal mechanical setup due to a hypothetical defect in one switch might cause it? Those switches are usually pretty robust, but it’s either that, a wireless harness issue, or a really weird Rambo board issue.

I think you both nailed it. After experimenting with different orientations of the harness/loom that run to the table limit switches I found one that is working consistently which points to there being a faulty wire in the mix. I haven’t yet identified the offending party but I will try to track it down when I can afford some machine downtime.
Thanks very much for your help with this!