melting polystyrene with halogen linear tubes ?

05 Aug 2007 The normal approach to build the vacuform oven is to run a bunch of nichrome wire across some ceramic posts and hook it up to a powersource.

But I don't have any idea where to get nichrome wire. I do however know that the efficiency of a halogen lamp is about 5%, which means that 95% of the power pumped into it is converted to heat.

I tried heating up a piece of 5mm thick polystyrene using a 500W halogen lamp and was able to bend it after only a minute or 2. That's promising.

Here's a picture of the bent plastic:
[G2:11637]

Most circuits in this house are 230V at max 16A, which means about 3500W max (with some to spare...). I have 3 circuits with a 25A fuse especially for the cooking plates. Such a circuit would get me about 5500W.

I'll be using a regular circuit for the vacuform, which means I can only put 7 500W halogen lamps in the vacuform. Another option would be to use 400W or 300W lamps, to have 8 or 11 lamps in there. I like the 11 lamps idea, because it's close to 9, which would make a nice 3x3 configuration.

I've created a heat distribution simulator to calculate what the heat distribution of a linear tube would be on a flat surface. I wasn't trying to make it efficient, but I just wanted to practice some python ;)

The program picks a random point on one of the configured linear tubes and then shoots a ray of light in a random direction. If the ray hits the flat surface (at a configured distance from the lamp), that spot is heated up.

This technique is similar to stochastic raytracing, except that I have no idea if it's even accurate for anything :)

The whole thing can be downloaded here:
http://www.singularity.be/Trashcan/heat-distribution.tar.gz

An AVI movie can be found here (2.2MB)
http://www.singularity.be/Trashcan/heat-distribution.avi

And an animated GIF is here (18MB)
http://www.singularity.be/Trashcan/heat-distribution.gif

I will probably write a better simulator soon (I have lots of python to practice...)