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MakerGear M2: Platform Z-axis Switch Repeatability

Having run off four quick prints with identical settings, I measured the thickness of the skirt threads around each object:

Skirt Thread Consistency

Skirt Thread Consistency

They’re all slightly thicker than the nominal 0.25 mm layer thickness, but centered within ±0.02 mm of the average 0.27 mm. Tweaking the G92 offset in the startup G-Code by 0.02 would fix that.

The 0.29 mm skirt surrounded the first object, which had a truly cold start: 14 °C ambient in the Basement Laboratory. After that, they’re pretty much identical.

Some informal measurements over a few days suggests the actual repeatability might be  ±0.05 mm, which is Good Enough for layers around 0.20 to 0.25 mm.

The larger skirt suggests that the platform has a slight tilt, but the caliper resolution is only 0.01 mm.

When I realigned everything after installing the V4 hot end, the last set of thinwall boxes looked like this:

Thinwall Calibration Cubes - 5 copies

Thinwall Calibration Cubes – 5 copies

Their heights were:

4.96 5.01
4.98
4.91 4.92

Not enough to worry about, in any event, sez I…

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  1. #1 by madbodger on 2015-04-09 - 10:15

    I remember seeing a show about stock car racing, where they were matching tires to a millimeter of diameter. One of the drivers asked if they could go to half a millimeter. The tire supplier looked annoyed and pointed out “We’re working with rubber and string here, guys!” I think the same thinking applies here. It’s goopy plastic, and like you said, it’s Good Enough.

    • #2 by Ed on 2015-04-09 - 10:26

      Consistency is a virtue; the relocated switch has that pretty much nailed down.

      For a 0.20 mm first layer, the difference between 0.15 and 0.25 is visually obvious; that much change generally indicates that I’ve inadvertently whacked the platform.

      There’s some work on auto-alignment for the M2, but the hardware seems stable enough that I think more gimcrackery would just get in the way.

  2. #3 by Red County Pete on 2015-04-09 - 11:44

    truly cold start: 14 °C ambient

    Wish I had that. I have lots-o-space in the barn/shop, but the heater is set to keep water from freezing. 3 °C is a good start on a winter’s morning… I usually wait till the afternoon before doing anything temperature sensitive. The stove will get me to a comfortable temp, but it takes time.

    • #4 by Ed on 2015-04-09 - 11:55

      You’re a better man than I am, Gunga Din…

      Some folk wrap elaborate temperature-controlled boxes around their M2, but the results seem marginal for anything other than large ABS objects and the high temperatures require putting the electronics box outside. I think actively cooling the steppers would be in order, too, as they’re really not designed for operation at 50 °C ambient.

      One of the projects on the to-do pile involves a baffle around the hot end to redirect the bed fan air; the heater runs at nearly 100% duty cycle with the fan on. Printed ducts hang entirely too much material on that one little screw for my liking, but perhaps I’m too fussy.

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