Saturday, February 17, 2007
First print for Tommelise
The blobs on the corners happened because I had to type in a new move xy command while the extruder was still pumping. I'm a fairly fast typist, but not that fast. The splay on the top side of the right box happened because I did a typo in coordinates. Positioning looks pretty good. I need to find a flatter piece of corrugated cardboard though.
The trace on the far right is my best effort. The flow was running a bit fast making the HDPE trace 1.25 mm wide. For scale the box is 30.5 mm on a side.
One thing, I crossed extrusion traces several times and it appears that HDPE will make strong joins between extrusion traces.
So that looks promising. Is it hard to find cardboard that is flat enough? I would think it would often have a slight compound curve to it... I notice it can be sensitive to fluctuations in humidity. If it is left on a non-porous surface it will sometimes curve after a few hours!
I did a few tests, and molten plastic should stick just fine to the silicon, but once it cools and hardens, it should pop right off!
This would also provide a smooth finish on the backside of the extruded object...
In any case, I took a moment to smear a blob of white silicone onto a scrap piece of plywood. I used two straight metal rods from a printer as guides on each side, and a disposable knife blade as a spreader. I should have only swept the blob once, the other passes just introduced ondulations and defects as the silicone -very- quickly forms a thin film and disturbing it messes things up.
I now have a little area of 10 by 7 cm or so, about 5mm thick. I'll try stuff with it tomorrow once it has cured.
I'm trying to order the parts for my extruder controller board, and am at a loss for figuring out what i need, and what length of nicor wire to use...
I posted a message on the other forum, but no one's come along and responded!
Using the old high school physics formula
and shifting terms
R = V/I
to get 2 amps of heating you need...
R= 12.34/2 = 6.17 ohms
That means that you need
(6.17 ohms)/(10.32 ohms/ft) = 0.6 feet or 7.2 inches of nichrome 80
It's important to remember that this 7.2 inches of nichrome includes the leads away from the the heating coil you make of it and that nichrome is near impossible to solder to anything else, or itself for that matter so you'll need a compression connector like a screw terminal to connect it to copper supply lines. Because it gets hot you'll also need a screw terminal that can handle heat.
Could be handy! :)
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