Sunday, December 25, 2011

CNC or Moco?

Decisions, decisions... I had one afternoon of free time to work on the project before the holidays. I had most of the parts for the DIY CNC, and the 5mm acrylic parts had also arrived for the alternate plastic version of the Moco head.  I knew i couldn't do both in such a short time so i had to pick one. This time, i decided to have a go at the CNC mill, the reasoning being that if i got that working properly, it would help with the motion control stuff too. Better to have the tools than the product at this point.

CNC mark zero point five.
So i started to bolt stuff together. The CNC mill/3d printer/ whatever uses a lot of the parts from Halsugrip system - i had them readily available. It says something about the versatility of the aluminium profiles that it didn't really take that long before i had the frame done using the standard length pieces (i had done some testing previously which obviously did help). For the linear motion, i used sliding bits on the profile grooves, for now. Will see if that works for real. The linear motion in all axes is powered with Nema 17 stepper motors, which rotate M10 threaded rods.

I bought the zero backslash leadnuts and threaded couplers from dumpster cnc. The quality of the parts seems to be very good. The only complain is that the couplers, while made for a metric system, use imperial hex grub screws for tightening the coupler to the rods and the axle. And of course, i have no imperial hex keys. I guess a trip to the hardware store is needed, or maybe i will replace those with my own screws.

As far as the laser cut parts for the machine go, they're mostly 6,6mm delrin. Wised up from previous mistakes, i tried to make them as adjustable as possible - no exact positions for fixing screws but rather grooves where the screws can be slided around at least a little. Nevertheless, many parts didn't fit at all as is, i had to saw, drill etc. them to bolt my Frankenstein CNC together. Its surprising how despite checking measurements multiple times, and even making a 3D version of the finished gear to see everything fits together before ordering, when i actually get the stuff on my hands, it rarely works the first time.

In theory, the CNC is now built - i have all axes assembled, motors and lead screws in place etc. Unfortunately, i didn't have the time to connect the electronics and bolt on the dremel-like cheap Cotech tool to actually try it out. The design is far, far away from being optimal, so it will be interesting to see what happens when i do. But that will have to wait untill next time...

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