Tuesday, March 13, 2007


Still printing...

I took a close look at the poplar veneer board that I was using and discovered that it had warped in our dry, winter air. I then cut an 8" x 11" piece of foamboard and taped it down, only to discover that my glass xy working surface is 2 mm lower on the right side (+x) than the left and that foamboard warps, too.

Fortunately, foamboard can be firmly taped down on my tempered float glass working surface and shimmed on the right-hand side to correct for the leveling error.

I then scaled up a slice of a cube .stl file 30x and printed it out to see whether I was getting the perimeter and cross-hatching right. That scaling feature of the Control Panel is really handy for diagnosing problems.

I put the extrusion head a touch too close to the foamboard, in fact about .25 mm into the foamboard. With that in mind let us look at a few features on the photograph.

The perimeter extrusion didn't actually start till a bit into the first side. This was pure sloppiness on my part for not properly priming the Mk 1. There are several commands that I have to send to Tommelise in sequence to have that happen currently and I simply didn't do them. I plan on writing a full priming routine for the Control Panel before too long. Certainly, the commands are there to do it in the firmware. I just haven't so far.

This is a bug in the Control Panel code. I should be turning the extruder off between paths and I'm not. I should also raise the extruder about a half mm between paths, too. I've got the commands to do all that, but again haven't done it yet.

This black bit is actually a scorch mark on the paper surface of the foamboard. While the Mk 1 doesn't reach the legendary Fahrenheit 451 at which point paper bursts into flame at about 400 degrees it is plenty hot enough to scorch paper.

Now here's the real puzzler. The cross-hatching simply isn't filling the slice but instead is tucked into one corner. I've got some sort of scaling problem in the PC-side Slice and Dice or Control Panel code, I think, but so far I haven't been able to understand what is happening to cause that.

Looks like an "off by 1" x 2 error on the far sides. Hope that helps :)
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