Saturday, November 30, 2013

New autoleveller software


Content moved to my web page:  Autoleveller

 Shimming the Spider

I use Lovejoy spider couplings between my steppers and the drive screws.  When last I used auto levelling, I noticed the Z axis stepper was making fine adjustments, but there was too much play between the couplers, and most of that fine movement was lost.  I carefully trimmed a strip of aluminum from a soda can and carefully wrapped it around the rubber coupling spider.  You can see a bit of this shim in the video below.  No play in the coupling.  Here is a short video of the Z-axis in action during board milling.  I was surprised how much it moves!

FWIW, here is a photo of one half of the coupler (the threaded rod is 1/4-20).  For reference are the original spiders I used from Jameco.  I actually had no problem with them, I just "felt better" with the big, beefy, professional spiders!

Anti backlash nuts

I figured some of the problem might be with backlash, so I crafted a home made set of anti backlash nuts for each of the axis'.  Before threading the rod into the coupling, I put on a square nut and a spring, then compressed the spring before treading into the coupling.  What is not in the photo are two small aluminum "L" brackets that sit on either side of the square nut to prevent it from turning.


Here is the outcome.  This is consistent across the entire board.  Although not a complex design, it was demanding and a sufficient test.  Here is a 20x magnified shot of a 9mil trace.  This run my tool was too deep, it should have been 16 mils wide.  I still have the old habit of routing deeper to avoid 'air milling'.  Next board I'll back out the tool 1 mil.

What I am looking at is the consistency of the trace width.  Horizontal, vertical and diagonal the width is spot-on.  also, the lines are very straight edged.

PCB Milling tip

I covered the copper with a good layer of WD40 before milling.  This made a HUGE positive difference.  The edges of the copper were milled very clean, just a light once-over with a ScotchBright pad was all it took.

Click for larger image
Here is the same magnification on a different board, cut earlier, without the mods and without WD40.  This image is after sanding with 120 grit paper!


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  2. Great job!
    About your anti backlash nut, shouldn't the square nut be either attached to the carriage or attached to the main nut (with linear moviment allowed)?


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