Monday, 20 September 2010

Plan to Action

After extensive "planning", I'm starting to turn theory into reality. I've spent quite some time on playing around (ahem - I mean designing) with an engineering CAD software package to design the z-axis of the cnc router. It's fun, but also awfully slow when you are just only starting to learn the software. At some point, I spent around 3 hours to "design" a board with 6 holes in it. With pen and paper, that might have taken slighty less time. But then, it's all for fun and not for profit...

So, here the the overview engineering drawing of the z-axis I have begun to built this afternoon. I am choosing a design where z-axis stepper motor moves up and down with the drill, so, the drill will be mounted on the large back plate. The small square front plate will be the connection point to the y-axis.

z-axis design intent.
Like all good plans, this one may need changing too...

There are a number of concerns, but maybe with medication I might be able to sleep tonight...
  • I'm choosing a fairly long z-axis (shafts 400mm; movement 250mm) as I aim to do some artistic 3D-shape cutting and maybe plastic extrusion. However, this makes the z-axis more prone to bending/errors.
  • I lack experience with linear bearings, so I have no idea if a 150x150mm square arrangement of 4 bearings will be robust and stable.
  • My stepper motor to threaded rod - connection will be via a clamped plastic hose. The stepper will have quite a bit of force at such a small clamp-radius, so I don't know if that might tear up the hose.
  • The best I can cut by hand is to about 1mm. That will not be enough to keep precision linear bearings parallel and happy. I'm oversizing the screw-holes to have some adjustment capability. But will that be enough (or too much) ?
  • I haven't solved the problem of mounting the actual drill to the board yet.
  • I'll be mounting the ball-bearing near the stepper motor to the mdf board with a metal clip and a couple of screws. That bearing will carry the entire weight of the drill, stepper motor, cutting forces, etc. Not sure how that will fare.
  • The entire approach of using a threaded rod and a single nut (M12) to move the system is a bit scary. Will it get too hot and lock up, or will it have too much friction ? Well, it's experimental.

Hopefully I'll have some free time tomorrow to complete it and then we'll get some answers...

1 comment:

Justin Templar said...

Great technical drawing, just wonder if the rod will hold all of that weight? Ummm