custom heating element with PID controller

Thread Starter

byakk0

Joined Nov 29, 2015
57
back to ground zero looks like.
I haven't had much time to work on this project in the past few months, but all attempts at using other sources of heat have failed in one way or another.
I'm looking into 240v, and if all else fails I'll just run a cord to my dryer outlet, but my electrical panel is currently full and I'm not sure if I can replace single gang for double or double gang for quad...need to explore the panel a little deeper.

But anyway, still needing to figure out the best way to make a custom heating element. The area I need to heat will be 12x32. I'm thinking kanthal wire and coiling it around some althread. Just a matter length and how to wire it to what...
 

djsfantasi

Joined Apr 11, 2010
9,156
Ok, having read through the posts, I’m going to add my 2 cents.

Heat lamps are unlikely to work efficiently, unless unusual geometry is used for the frame or the lamps are a very specific geometry relative to the desired frame.

Custom coil design is almost necessary. The heating element must be arranged so that the outer elements are closer together than the central elements.

Also, the area covered by the elements must be larger than the frame. The walls between the element and the frame must be tapered AND consist of a laminate of an IR reflective surface and a heat resistant material. I.e., a steel outer surface and a concrete (Durarock) inner surface. This volume should be the most efficient, otherwise your process will waste time heating the air and insulation

You need a heating design to provide a uniform heat, especially along the edges of the plastic which typically disperses/loses heat along the frame.
You need an extremely even source of heat on the area of the plastic sheet. Otherwise the vacuum formed piece will not uniformly conform to the model.

The cooling effect of the vacuum draw cannot be discounted. To fight this effect, the plastic must be heated uniformly with a high degree of control.

I vacuum-form many pieces for commercial animatronics. It took me a while to learn the above principles. I offer my comments to save you some time.

IMHO
 

Thread Starter

byakk0

Joined Nov 29, 2015
57
Thanks for the insight, DJ. That actually helps immensely.
Some of my trial designs were partially tapered, and looking back it makes a lot of sense having the heating element larger.



Ok, having read through the posts, I’m going to add my 2 cents.

Heat lamps are unlikely to work efficiently, unless unusual geometry is used for the frame or the lamps are a very specific geometry relative to the desired frame.

Custom coil design is almost necessary. The heating element must be arranged so that the outer elements are closer together than the central elements.

Also, the area covered by the elements must be larger than the frame. The walls between the element and the frame must be tapered AND consist of a laminate of an IR reflective surface and a heat resistant material. I.e., a steel outer surface and a concrete (Durarock) inner surface. This volume should be the most efficient, otherwise your process will waste time heating the air and insulation

You need a heating design to provide a uniform heat, especially along the edges of the plastic which typically disperses/loses heat along the frame.
You need an extremely even source of heat on the area of the plastic sheet. Otherwise the vacuum formed piece will not uniformly conform to the model.

The cooling effect of the vacuum draw cannot be discounted. To fight this effect, the plastic must be heated uniformly with a high degree of control.

I vacuum-form many pieces for commercial animatronics. It took me a while to learn the above principles. I offer my comments to save you some time.

IMHO
 

shortbus

Joined Sep 30, 2009
10,045
According to me, try to use a heating element or nichrome wire to cut the fiber and as well as acrylic sheet.
This wasn't about cutting or bending plastic, but was about making a vacuum former. To soften and form a sheet of plastic over a object/mold. He is on another forum with me. He ended up getting some toaster ovens and using the heating "calrods" and controls from the ovens to do this. I may be wrong but don't think he comes here anymore.
 

Thread Starter

byakk0

Joined Nov 29, 2015
57
Yeah. Not cutting or bending the plastic.
What is SSLA?

Here's my current solution (been meaning to post pics for a while now)
completely modified a toaster oven, including using the controls.
Much of the metal is recycled from a scrap yard.
Heater box on the left and platen on the right with a formed part.
Needs a little revision but works just fine for my needs.
 

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shortbus

Joined Sep 30, 2009
10,045
Hi byakk0, hope you don't mind me answering for you. Hadn't seen you here for quite a while.

Did the information on the steel help you?
 

Thread Starter

byakk0

Joined Nov 29, 2015
57
On my metal meet post you mean? If so, I'll have to go re read. This has been a long drawn out back-burner project so some things skip my mind.
 

Janis59

Joined Aug 21, 2017
1,834
RE: The glorysong to Kanthal.
At over 1000 C indeed are only two well alternatives, Kanthal wire or silicon carbide rods. Avoiding the brittle rods so the Kanthal may seem the modern day wonder but it NOT PROVIDES the self insulation like all fehrals (and especially Nichrome) does. So because of need for distancer mechanical constructions at so low temperature like 500 C the ultimate choose ought show onto Nichrome wire.
By the way, endstations where the wires are screwed to something ought wear the double or more better the four-fold wire cross section. Always the burn-off happens there, but with two-folded winkled wires rarely and with four-folded never.
 
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