RepRap: Blog

Much progress with the linear axis driver as I recover, now my guts are where they should be once more. The drivers' longer arms had to be re-shaped because they collided with the Nut Bar, the limit switch can now be repositioned, an overall shape is emerging for the Axis Driver base, and the pantograph flexures no longer hang up on each other.

You can see that the blue and yellow flexures are held in slightly different cases. Those are just what developed as I was adjusting the available travel up and down the Drive Screw. The latest improvement though is adding a Lower Nut Bar that provides a bearing surface right next to the Drive Screw Coupling (only fitted on the blue one, not that it's terribly visible). This reduces the tendency of the drive screw to wobble. It might seem obvious to do that, but I've been telling myself that it shouldn't be necessary. Well, after some introspection lying in a hospital bed I think I was being stupidly stubborn and I've put one in.

As result the new driver seems more consistent, even though it looks like it's made from a kid's construction toy - which it essentially is - and I'll create a proper case design for V0.05 now I know where the bits need to go. I've managed to keep the shape compatible with the V0.04 too. That way I can move to V0.05 and still give people who want to play with the new driver on old hardware the option. I've not adapted it for the Z axis yet, so that'll sill need a V0.04 Driver for a while.

So, testing with the new X & Y axes. The "FAB" logo was done at 25μm/pixel, the "Hello World" at 30μm. A major advance here is that the slide was not manually repositioned at all - the new Axis Driver has a significantly enlarged working area and stays sufficiently linear throughout it. To me there appears to be a lot less overall variation in dot spacing. The 'o's are the same size and silly things no longer happen to the 'W'.

I'm not happy enough with the Z axis though, which I tweaked from image to image. That's why the dots are different. Originally I just wanted to get on with deposition experiments, but that'll need multiple layers. I've reached the point where I want the Z axis to be repeatable like the X & Y axes are now, rather than merely sufficient for initial experimentations. I could waste a lot of time on layers if the Z isn't being consistent.

So priority list: Everything on github, new version, new Z driver, deposition experiments.

# posted by vik-olliver @ 9:01 AM