Community challenge #10: Milling plastics (closed)

Submission (old project, but why not get the ball rolling) part 1:

Description: Several years ago, I CNC’d my Atlas lathe, just because. This was a very large project, as I rolled my own controller. I dabbled at it for several years, so by the time I heard of GRBL, or got my Nomad, I was better than half way.

Last year, I made a few changes based on my experience, and two of those are presented here:

The ones I will show here are a mount used for stepper drivers to control cooling (Big Easy Driver replaced the original for the leadscrew) and a decent mount for the leadscrew stepper to replace the cranked up sheet metal mount I threw together for development, and left in place since it worked. Noisy like crazy, though, and limited quality of work on the machine. No damping, poor stiffness, and lots of surface area is all bad choices for for mounting steppers.

The main panel has the operator controls for manual use (feed and threading) and holds the electronics.

This is the interior when I was part way through refitting last year. There are a number of parts visible that came out of the Nomad, including a couple circuit boards (the rotary quad encoder control board is not visible in the housing) and most of the parts for the rotary encoder (rough cast on a $US200 3D printer, then machined on the Nomad to tolerance).

First, the airflow guide:

You can see the fan on the left, underneath the leads to the terminal block.

HDPE, milled on the Nomad. The CAD design shows what it looks like better:

Note the form of the channel. The driver is cooled by the copper mass and vias on the circuit board, so the goal was to maintain good flow over the board surface. There are a couple copper pins I added that reach out into the airflow under there. This took the operating temp from at the limit to about 20C above ambient running full current.

The work was done in Inventor, though Fusion360 will do everything I did here, but slower. The machining steps:

An adaptive clearing for the majority of the material removal with a 1/8" two flute, 10KRPM, 1000mm/min feed



A ball end was used for the fancy surfaces. Morphed for the slope, which makes any scalloping be in line with the airflow, followed by Scallop for the more vertical sides and fillet blend:


Then the drilling. The drill operation here was to locate the holes, and they were finished on another machine for practical reasons. A Nomad is not a drill press. The torque isn’t really there for deep drilling, so if it can be finished on a more suitable machine, why torture the poor beast?


(Part two with the stepper mount to follow)

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