Re: Annealing Oven for Acrylic / PMMA / Perspex / Plexiglas - Searching for Parts

From: Christopher Tidy (cdt22_at_cantabgold.net)
Date: 02/28/05 

Date: Mon, 28 Feb 2005 02:58:53 +0000 (UTC)

>>>I'm looking to build an annealing oven for Acrylic / Perspex /
>>>Plexiglas / PMMA. Nothing fancy just functional, I'm intending to use
>>>MDF to create a box structure to which I will add a hinged door and
>>>some heating elements. The annealing process is only to about 80C/175F
>>>so I'm happy that the wood will do the job.
>
> I think that the temperature is too high for normal electrical
> insulation (fan motor).
>
> Someone correct me if I am wrong. ( I am sure someone will :-) )
>
> Bill K7NOM
>
> Bill

I've got a useful table of safe motor winding temperatures here (in a
book called Electric Motors by Jim Cox). It says <100 C is safe for all
motors, 100-125 C safe for most motors, and 125-155 C safe for high
temperature motors. Now these are winding temperatures, which will
naturally be some way above the ambient temperature, but I suspect you
could get away with putting the right kind of motor inside an oven at 80
  C. Many electric ovens contain a small fan powered by a shaded pole
induction motor, and while the fan isn't actually in the oven, it's
between the oven at the outer casing, so it must still get pretty hot.
Shaded pole motor are very inefficient anyway, so they are built for
getting hot. You should be able to find one free if you're interested.
They're used in old record players, dishwasher and washing machine
pumps, electric ovens and plenty of other applications.

Best wishes,

Chris

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