Friday, March 19, 2010
No peel, no warp, no backlash
I got Slice and Dice working well enough to let me do some serious R&D. After a side excursion with partial STLs of hands and naked ladies, I got back to work on the herringbone rack and pinion technology.
My first exercise was to see if I could print single herringbone pinions without having a lot of meltdown problems. Skeinforge had a lot of problems in that regard. In fact, Slice and Dice let me do that.
I printed it pretty much solid for strength and paused it for a couple of minutes midway through the print and let it cool down for a few minutes. No problems. This one was printed with 0.25 layers.
Next came the rack. I decided to use the exercise last night to press the limits of Slice and Dice. I figured that I ought to be able to print a 250 mm diagonal layout rack. That let me find a half dozen limits bugs in the S&D code and get them cleared away. I also decided to see if I could print a useful 0.1 mm layer.
In fact, I could. Here we are about halfway through the print.
It took about an hour, by the way.
Here it is, complete.
And a closeup of the teeth.
For some reason the extruder is not shutting off between layers. While that is easy enough to clean up with side cutters, I'll be diving into my code to see if I can sort that out in the next few days.
The pinion gear mates with the rack with no backlash.
I didn't make much of an effort to clean up the pinion which you can see in this outdoor pic.
I've found that the colour rendering is always better outdoors.
Finally, for those of you who haven't a sense of scale looking at the Rapman print table.
My next task will be to figure out how to put the pinion on a printed, extended shaft so that it can be secured from both sides and mate with the short axled NEMA 17 that will drive it. Then it will be a matter of integrating my Pololu Allegro 4983 microstepping driver board into my I2C bus and driving the thing from my Microchip 18F4550 uC board.