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Oven Design

 
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walhalla



Joined: 10 Mar 2013
Posts: 4
Location: Canada

PostPosted: Mon Jul 22, 2013 7:52 pm    Post subject: Oven Design Reply with quote

I am looking into building a new oven in my research I have seen them made different ways, what is a good efficient, and a well designed oven some questions
Opinion on Materials
Is it a good idea to have a taper
Would stainless mesh be good to lower heat in over heated areas
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Josh
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trapperdale
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Joined: 07 Jun 2009
Posts: 106
Location: fresno, california

PostPosted: Tue Aug 13, 2013 7:27 pm    Post subject: Reply with quote

Hi Josh,

sorry no one has made a reply.....
they need to know what type of machine you are building
overhead oven?
how big?
zones ?
what material will you be working with?
watt density needed?
production or one or two parts per day?
shading and reflecting is used to fix hot and cold spots under the heater
in production machines we want less than a 5* temp variance in sheet temp.

Dale.
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spektr
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Joined: 07 Jan 2008
Posts: 425

PostPosted: Fri Aug 16, 2013 10:22 am    Post subject: Reply with quote

been quite busy, but 'd be assembling the tile squares based oven.
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trapperdale
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Joined: 07 Jun 2009
Posts: 106
Location: fresno, california

PostPosted: Wed Aug 21, 2013 5:23 pm    Post subject: Reply with quote

did you post up the tile square info on this site???????
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crashmann
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Joined: 27 Sep 2005
Posts: 501

PostPosted: Thu Aug 22, 2013 2:25 pm    Post subject: Reply with quote

Check out the second picture in this thread:

http://www.tk560.com/phpBB2/viewtopic.php?t=1832

This is a large vacuum forming machine and the heaters are made from coiled nichrome wire mounted to either Hardibacker cement board or another type of similar material, resistant to high temperature fatigue.

The part you don't see are the electrical supply connections at the ends of each coil, and that is where the math and engineering come into play.

The Thurstan James flip flop style vac table does a good job for getting started in vacuum forming, and I've pulled tons of stormtrooper parts with that setup. It heated 32" x 24" sheets of plastic from underneath using an oven built from Hardibacker cement board and nichrome coils. It was powered by a single 120 volt AC circuit running at 20 amps. The hinge in the middle gave me great leverage in stretching the HIPS over molds that were way too tall.

Check out the video to see it in action:
http://www.youtube.com/watch?v=hTQrSCGZyUE

Eventually the single piece of Hardibacker for the oven base cracked creating a very dangerous situation. I replaced it with 5 smaller pieces of Hardibacker suspended by ceiling tile grid and with room for heat expansion and contraction. The person I sold the rig to has not reported any cracking yet.

Check out this thread for way too much discussion about Hardibacker cement board:
http://www.tk560.com/phpBB2/viewtopic.php?p=9543&highlight=#9543
(the second page shows a tiled overhead heater arrangement)

An overhead oven does not heat the plastic as efficiently because you are mostly using radiant heating with infra-red, and you are losing the advantage of convective heating.

So, what size table are you planning to build?

Are you doing a flip flop Thurston James style, or an overhead Protoform style?

How many volts for your supply, 120 or 240?

How many amps on the circuit breaker?

Return with these answers, and we can point you in the right direction Very Happy

Charlie
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walhalla



Joined: 10 Mar 2013
Posts: 4
Location: Canada

PostPosted: Sun Oct 20, 2013 7:02 pm    Post subject: Reply with quote

The unit is 24 x 24 inches
It is not an overhead unit
It will not be used for production, Just for a hobby
It will be 120 volts and I am unsure of the Amps in the circuit breaker

I have a electrician who is going to do the wiring I am just looking to get it all organized and prepared
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Josh
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