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The open source phone by Dooba, called "Trill" is awesome. Open source PCB with a 3D printed enclosure. Beautiful little OLED display. Making a cellphone has been my objective for about a year - I even have most of the parts already. Sadly I haven't had the time to sit down and really work on it. But my cellphone is on it's last leg (And I've had it since 2012 - so it can be considered archaic at this point). I really don't want to buy another phone - so Trill is on my wishlist.

A look at the spindle slipping due to low contact friction with the holder, Z axis probing to prevent warpage, and counterweight springs to give a favorable failure mode for the spindle.

The demands of graduate school were taking their toll last month and I wasn't able to give OCI the love it deserves. But I'm back to work now! The Z axis was not getting enough current from the stepper driver on the ramps board. This is because the entire spindle assembly weighs 1kg - and is straining out the stepper motors. When moving in small increments, the motors will skip steps and move inconsistently (see data from Circuit Mill Development Log: Z Slip). Often times the spindle would slip downward while cutting, causing some catastrophic results.

I've noticed that the circuit mill in development is having issues with small adjustments (0.3 mm). During small movements, the axis will do one of two things - it will either not move at all, or it will move too far. For example in the picture below, the left pattern was done keeping the Z axis at a steady height. The right pattern was done with the Z axis adjusting to keep the cut level. As you can see, the mill appears to be "slipping" over time, and the bit cuts further and further into the board.

Here's a fun video showing all of the work that went in to prototyping, testing, and manufacturing television sets in the 1950's.