Thursday, September 9, 2010

Radiant Heat

I figured that shining a light on a matte-black surface would be more efficient than hooking up wires to my moving Y build platform.

After getting some black construction paper to 100 deg C in less than a minute... I was worried about having too much heat with my 150W radiant heater bulb. Not the case as it turns out.

I bought some matt black high-temperature paint, cut a 2mm aluminum plate to my table size (30x24), wiped it with acetone and sprayed it matte-black.

A couple hours later I rested it on a thermocouple, on my MDF build platform, and turned the light on it at a distance of about 30cm, normal to the surface.

The temperature under the plate topped out in about 8 minutes, at 77 deg C. I put a piece of glass on it, and when it took another 10 minutes to get back to 80 deg, I canceled the operation, realizing that the top surface of the glass would be cooler than the plate anyways.

Next was a layer of Kapton on top. The temperature quite quickly came up to 80 to 90 deg. C. The tape obviously absorbs IR.

I decided to print a Wade's large gear, as I had printed one the night before on acrylic, mostly successfully, but with a bit of warp.

I positioned the light at a 45 deg. angle, aimed into the extruder's hot-end. Temperatures were still about 90ish in front of the extruder, as measured by my IR non-contact thermometer. (I checked with the heat-light off for a sec to be sure it wasn't effected.)

I couldn't get my ABS natural to stick to it, I even wiped it with acetone... Someone on IRC was talking about 'drymount' adhesive spray, which I had laying nearby.. so gave it a try in desperation. (Amazing what you'll do when you have an audience on IRC watching a webcam feed ;-)

Drymount worked great for getting the print to stick.

And the 80 - 90 deg C surface temperature, plus whatever the natural ABS makes internally from the light, works for keeping the print straight.... where it's warm...

But the backside was cooler.. by quite a bit... and showed quite bad shrinking... even worse than my whole gear was exhibiting on acrylic for some reason.. I aborted the print when I saw the back lifting.

It's clear to me that to do this, would need 2 150 watt lights, front and back... resistive heat is starting to look pretty good to me.

1 comment:

  1. Glad to see that this worked so well! I think that four lights, one at each corner, would work best, of course you could use lower wattage.