Monday, December 18, 2006


Documenting Tommelise...

I was going blind working on the xy positioning stage firmware so I decided to take a few hours off and take a shot at documenting the actual structure of Tommelise.

What you see is pretty close to what is built.

I did, however, iron out a few of the smaller and more obvious problems that I have in the bootstrap Tommelise as built so that anybody wanting to go in this direction won't have to hit the same problems I did.

You can download the .aoi file for Tommelise here. I've scaled the model in inches since it is made of US module furniture grade poplar boards. If you shop for this sort of wood please note that the width of the boards is a half-inch less wide than listed, that is, a three inch board is actually 2-1/2 inches wide and so on. Thickenesses are typically a quarter-inch thinner than listed. Thus a 3x1 inch board is actually 2.5x.75 inches.

This model is a work in progress. It's not all there right this moment, but there is enough there to get someone started. I'll be adding to it and sorting out the order of the parts listing a bit later.

Looks pretty good, but I'm sure things can be fine-tuned in that model. It looks like you went for a larger number of small parts, which would be easier to repstrap/cnc when things come to a head.

I'd look at the stability of this and see if there aren't ways to trim things down a little. The 45deg supports might not be needed with 3-4 bolts holding it to the frame already.

Anyway, always building big, eh? What was the working area of this version, and how much weight do you figure the head will handle, in case someone wanted to use this repstrap as a woodcarver or engraver as well as an extruder.
***What was the working area of this version***

250 x 250 x 75 mm

***in case someone wanted to use this repstrap as a woodcarver or engraver as well as an extruder***

Interesting that you should ask that question. My son asked the same thing yesterday afternoon. Initially, I pointed out that the Mk II only weighed a couple of ounces and that weight really wasn't significant. My son then noticed that I had strapped a 4 inch C-clamp onto the x-axis positioning stage that holds the z-axis and that that thing weighed at least two pounds.

I think that it would probably cope with a Dremel router head with a flexible rotary cable. The Dremel could then be strapped to the x-axis positioning stage and the router head at the end of the rotary cable would be on the z-axis positioning stage.

I'd suspect that with the current state of lateral stability of the z-axis that you'd be well-advised to take very shallow cuts with the router. That would slow things down a bit, but it could, I suspect, be used that way.
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