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I want to melt a bed of plastic powder so that the powder bed once melted then cooled form a solid sheet of plastic.

In order to melt the powder I thinking of passing a nichrome (Ni80/Cr20) wire over the bed without the wire touching the bed. With the direction of motion of the wire perpendicular to the length of the wire.

The heat from the wire should radiate from the wire and pass into the plastic powder in order to melt the powder is this possible? Is it possible to to melt plastic powders through heat radiation from a nichrome wire.

Conditions:

  • I can use a wire of any diameter. Single wire or multiple wire in parallel.

  • Melting temperature of plastic used is 270-300°C.

  • Any distance between the wire and the powder bed is possible. Close distance between the wire and powder is preferred.

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    $\begingroup$ This sounds like an engineering question rather than a physics one. After all, we can use a wire of radius one kilometre heated to 1000 C at some finite distance (in vacuum, on a friction-less plane) to do it... but you are actually interested in something that can work practically. That involves trade-offs like cost, safety, reliability etc. this SE does not do. $\endgroup$ – Anders Sandberg Apr 5 at 12:05
  • $\begingroup$ I believe to heat something to 300 C with radiative heat alone would require such high wire temperature that the NiCr would quickly oxidise to beyond useful. $\endgroup$ – Gert Apr 5 at 12:12
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    $\begingroup$ It's one of these things that 'on paper' looks promising but in reality will be very difficult to make work. $\endgroup$ – Gert Apr 5 at 12:22
  • $\begingroup$ @Gert. Multiple wires can work wonders, and the OP is willing to consider this. $\endgroup$ – Guy Inchbald Apr 5 at 17:06
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Yes it is perfectly possible - I used to get into trouble doing things like this as a kid. When I grew up powder-coated steel, made in exactly this way, was common for industrial furniture.

If you use a single wire then smooth, exact movement will be critical or the plastic will end up wavy. Running several wires close together, either in series (same current, higher voltage) or parallel (same voltage, higher current) will help smooth the sheet. The usual way is to wind a spiral of nichrome resistance wire around a ceramic rod (i.e. a traditional heating element) and apply AC mains across it. You could use a variac transformer or modern switched-mode equivalent to adjust the heat, much like an electric toaster.

If you try to go too fast, only a thin layer at the top will melt. If you slow down then the plastic will have more time to melt a bit deeper but you must also turn the power down or the top will start to overheat and give off toxic fumes. If you want a thick sheet, you may need to lay it down in several layers.

Make sure your workspace is well ventilated!

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