Close

days of mushy-brain

A project log for 2.5-3D thing

a tiny-but-scalable three-ish axis-system *from* laser-cuts

eric-hertzEric Hertz 08/10/2015 at 10:281 Comment

This is the initial-concept for a snap-together drum/driver-pulley... two "forks" cross-over each other and pass-through each layer of lasered-circles. (despite using transparency, the renderings don't show the forks passing-through the cylinders).

I'm trying to figure out how to account for material-thickness variances (they only guarantee 10% tolerance)... so I'm thinking "forks" coming from each side with serrated edges that when compressed together will ratchet into ever-tighter compression. It's frustrating, at this point.

Also trying to figure out how these pulleys will actually be mounted... so-far I'm thinking two additional small-circles (like the red ones) on either end (outside the green)... these'll ride inside a cutout mounting-plate on either-side. It's hokey, and the amount of drag...? yeah. But it's the best I can think of. Makes hand-driving a bit difficult, having to maneuver your fingers around the mounting-plates... but, again, it's the best I've come up with. Maybe a crank extending from one of the forks on the outside of the mounting-plate, but then there's torquing on one "fork" which might cause twisting... I'm not opposed to glue, but I'd *like* to not need it in the long-run.

Initial calculations suggest the driver/drum pulley can have a

relatively small radius and still have the cable physically attached to

the drum at one point, just a few (ten-ish?) turns are necessary for full-motion, so no need to worry about slippage...

Anyways, for attaching the motors, I'm visualizing yet another circle with a +-shaped cutout that slides onto the protruding part of the "forks"... But, the + doesn't really work with a motor-shaft attached in the center... so then a four-hole mate at the bottom (in the image) with longer fork-prongs...? But, then, there's the serrated/ratchetting thing that was discussed earlier... so, yeah... my brain's gone to mush again.

In reality, this whole project is ridiculous... and more-so trying to do it without a prototype or ten of these various mechanisms. I've got a perfectly good inkjet-printer mechanism just waiting to be hacked into a 2-axis system... attach a dremmel and probably could make many of these parts for prototyping...

and, yahknow, what was the original purpose of all this, again? I think, somewhere in all this, was the idea "yahknow, it'd be nice to have access to a CNC-machine to make cases for things, etc..." which would certainly be a heck-of-a-lot easier to do off-the-bat with this lasering-order...

Oh, and, apparently the bit-banged UART receiver isn't working yet, which is surprising, to say the least, as I/O is clearly working, and precision-timing is clearly working, as well... Seems like that'd've worked pretty much right-off-the-bat. Is it the 3.6V signals feeding into the 3.3V Inputs? No, I tried feeding through a diode and a pull-up at 3.3V... so...? And the outcome is *really* weird... it seems to be echoing *several* 0xff's each time I transmit *one* byte to it. (and raw transmission from it, rather'n an echo, works perfectly fine). So, yeah.

(WAIT! Is it the fact this system's so fast...? I might've forgotten to increase those timer-comparison integer-sizes on the receiver, as I had to do on the transmitter.... TODO!)

Yeah, this is all as of several days ago, I'm just trying to remind myself the status.

Discussions

Eric Hertz wrote 08/10/2015 at 10:33 point

alas... I did, in fact, consider the integer-sizes already, and did, in fact, fix them in the receiver-code... but maybe not quite...

  Are you sure? yes | no