Archive for November 13th, 2012

Thing-O-Matic: Cable Control

The alert reader will have noticed two slip faults in the jellyfish cookie cutter:

Jellyfish Cookie Cutter - on build platform

Jellyfish Cookie Cutter – on build platform

Look closely…

  • Above the wide lip, to the right (+X)
  • Below the top edge, to the front (-Y)

Those failures came from two separate cable snags that stalled the X and Y stepper motors for about 1 mm of travel. Fortunately, I wasn’t paying attention and, by the time I figured this out, the thing was nearly built, so I let it run to completion. The thick base plate accounts for most of the plastic, anyway.

First, the cable bundle on the right snagged on the socket-head cap screw just in front of the X axis limit switch (hidden behind the bundle here). This picture, taken after the +12 V pin in the HBP connector burned through, shows the typical snarl of wires inside a Thing-O-Matic:

Thing-O-Matic - HBP cable routing

Thing-O-Matic – HBP cable routing

The rewired thermistor cable snagged on the bulldog clip holding the top aluminum plate. This picture, taken after the thermistor pads fell off the HBP, shows the filler plate I put in place to prevent the cable (entering from the top and passing below the white cable on the HBP) from jamming in the gap between the Y axis stage and the case, but you can see how the bulldog clip handle could snag it when the platform moves rearward from the front left corner (+X +Y):

HBP Thermistor cable - snag shield and bulldog clamp

HBP Thermistor cable – snag shield and bulldog clamp

The fat gray cable flat against the case in that picture carries the X axis stepper drive signals up-and-over the Y axis. The thinner gray thermistor cable emerges from the electronics bay inside the case corner, then arches in from thetop.

My buddy Aitch recently gave me a few meters of corrugated wire loom, so I moved the bulldog clip rearward and bundled all those loose HBP wires in one tidy snood:

Thing-O-Matic - X axis cable loom

Thing-O-Matic – X axis cable loom

I’m sure something else will go wrong, but the machinery looks marginally less haphazard and the cables don’t snag while I’m watching…