All that figuring is for 2000 watts because that's the most you can get out of a 120 volt outlet. You have not established that you need 2000 watts.

That much heat could raise a pound of water (or probably plastic) 227 degrees F in 2 minutes (if it didn't boil). Add that to 70 degrees at room temperature and you're at nearly 300 degrees F. That sounds excessive to me.

 

I wonder if a better plan wouldn't be to rig up a bunch of light bulbs instead of the nichrome wire. It's just a question of getting energy out of the wall outlet and into the material to be heated, right?

(While you can still get incandescent bulbs, that is. Fluourescent or LED ones won't do this job.)

 

Ehhh...Not on the top ten list. Compared to nichrome or quartz heaters, light bulbs are:

Hard to buy and getting worse
guaranteed to fail in a few hundred hours
fragile
bulky
expensive
not designed to survive at ambient temperatures in excess of 200F

 

You guys are a bunch of evil masterminds around here aren't you?

Lifesavers, regardless.

Many thanks.

(when I wrote "working calculator" I had just tried to use that thing. No idea how you got it to cooperate)

Video of same basic idea & operation of the machine:

 

the way i'll use the machine depends on what I'm making & how many. Or just the order in which I pick things up and put them down in the shop that day. No real rhyme or reason to it, just another tool in the arsenal.

 

You guys are a bunch of evil masterminds around here aren't you?

Count on it!

 

4. I'm trying to avoid ceramic mounting hardware. At first I loved the idea and wanted to go all out with it, but it's pricey, and you still need mounting hardware to fasten IT down, so it's parts on top of parts. Which is what I meant by "complicated mounting solutions" in my original post and why I'm so keen on a wire tie or pins

If you have more time than money, the 'backer board' material can be used to make mounting hardware for your coils.

 

All that figuring is for 2000 watts because that's the most you can get out of a 120 volt outlet. You have not established that you need 2000 watts.

That much heat could raise a pound of water (or probably plastic) 227 degrees F in 2 minutes (if it didn't boil). Add that to 70 degrees at room temperature and you're at nearly 300 degrees F. That sounds excessive to me.

Ok, so just to confirm this before I order my wire:
With http://www.amazon.com/E-Age-50-220V...cp_2_FB98?ie=UTF8&refRID=0EN2YCPCQ9MGPQSV9D87 (in the mail) maxed out @ 16 amps, 125 volts, 2000 watts, I can jack 284 inches of 17 gauge wire up to 1280* F, Correct? To get into my ballpark of 115 inches I'd coil around 1/4" ID (just to make life a little easier)

If you have more time than money, the 'backer board' material can be used to make mounting hardware for your coils.

Yeah you're right that could definitely work. I never thought of that. But the guy that can sit and carve all those out, is definitely not me. (haha)

 

Yeah you're right that could definitely work. I never thought of that. But the guy that can sit and carve all those out, is definitely not me. (haha)

Pretty simple really, and would take only a little time. Saw out rectangular blocks, then drill a hole on one side of them the size of the nichrome coil, do this on the same side of all the blocks. Then turn the blocks 90 degrees and drill a hole for the screw. Instant wire support, and safer than bailing wire to backer board approach.

You could even make them simpler. Cut strips of the board the width of the backer. Then drill the holes for the nichrome coil in the pattern desired. The turn 90 degrees and drill the screw holes.

 

@FUBARed

All that figuring is for 2000 watts because that's the most you can get out of a 120 volt outlet. You have not established that you need 2000 watts.

That much heat could raise a pound of water (or probably plastic) 227 degrees F in 2 minutes (if it didn't boil). Add that to 70 degrees at room temperature and you're at nearly 300 degrees F. That sounds excessive to me.

You want to heat a 24" x 24" x 0.125" sheet of acrylic (2.6 lbs) from 70F to the forming temperature (about 320F) in 120 seconds with specific heat of 0.35 BTU/(Lb*F) = about 2000 watts at 100% efficiency transferring the heat to the work piece. I think you will have to be happy with 3 to 5 minutes unless you design a really good enclosed box - but then you risk scorching your work pieces and you need a really good temperature control system.

 

Shortbus and Gopher brought the final pieces of the puzzle.
You have everything you need now.
I might even suggest you don't buy a dimmer because this is going to require more than 2 minutes at full power.

 

@@FUBARed
One more thought, you should probably have a heated hood that is about 30% longer and wider than your work piece so you can get even heat. If the heated hood is the same size as your workpiece, then you will get greater heating int he center and cool edges. That may be ok (depending on your form) but usually not a good thing. You can use a visual vector system to make sure you have equal heating of your work piece (draw side view of your heating elements and your work piece - then draw lines from heating elements straight down, then from neighboring heating elements down at 45-degrees left and right. Make sure all areas of your work piece have an equal number of vectors hitting it.).

 

@@FUBARed
One more thought, you should probably have a heated hood that is about 30% longer and wider than your work piece so you can get even heat. If the heated hood is the same size as your workpiece, then you will get greater heating int he center and cool edges. That may be ok (depending on your form) but usually not a good thing. You can use a visual vector system to make sure you have equal heating of your work piece (draw side view of your heating elements and your work piece - then draw lines from heating elements straight down, then from neighboring heating elements down at 45-degrees left and right. Make sure all areas of your work piece have an equal number of vectors hitting it.)

It never ceases to amaze how far you guys will go to help a complete stranger. Especially being I basically come here and throw my hands up in the air and say "I don't know how, do it for me."

This is good information and something I was thinking about. My overall sheet size will be 24x24 so I'm figuring a 23-22-1/2" area that can be heated. The new hardware everyone provided has changed my plan around quite a bit. I now have 3-6 times the amount of wire to work with and an extra 500-600 degrees over what I had come up with by myself. I've never heard of the vector approach before, and it's very interesting. So with all this extra leeway I'll try a lot more. Thanks.

@@FUBARed
Also, particle board is not a very good option for a support of the coils - it will brown and char unless you are sure your wire will never exceed about 350 F. You should look for some glass panels to insert between heating elements and particle board (LCD TV glass should work well - 30" panels would be good if you can find a few dead ones at your local recycling center - tungsten carbide PCB drill bit works well).

I think we've got two different materials in mind. Or maybe I'm confused with what material you're referring to.

Because I would never consider using a material with such a low burning point like standard M/HDF or particle boards in a rig that can reach temperatures as high as 1200F. That's a sure fire recipe for disaster, and likely someone's Death. I just wanted to spell that out for anyone that comes across this post in the future and might get confused by terminology or not know better. The material I'm using for every single surface that will be exposed to heat is a very high temp ceramic/mineral concoction with a safe working temperature of 1900F. Nothing I'm using in the construction of this oven comes from Home Depot or the like. It's all coming directly from specialty manufacturer's through the use of my Federal ID number. (my U.Y.H & C.Y.A disclosures) But I'm totally gonna pick up some drill bits because that's just cool.

 

It never ceases to amaze how far you guys will go to help a complete stranger. Especially being I basically come here and throw my hands up in the air and say "I don't know how, do it for me."

Basic philosophy: I don't mind helping someone that is willing to help himself.
(If you're not going to actually DO anything, don't waste my time.)

 

The material I'm using for every single surface that will be exposed to heat is a very high temp ceramic/mineral concoction with a safe working temperature of 1900F. Nothing I'm using in the construction of this oven comes from Home Depot or the like. It's all coming directly from specialty manufacturer's through the use of my Federal ID number. (my U.Y.H & C.Y.A disclosures) But I'm totally gonna pick up some drill bits because that's just cool.

Good, I was a little astonished when I looked at the image in the first post, it looked like something that could burn.

thanks for the update. And, most of us are problem solvers and just check in to see if there are any interesting stories/problems where we can through our $0.02 and see if anyone likes our ideas.

 

Good, I was a little astonished when I looked at the image in the first post, it looked like something that could burn.

thanks for the update. And, most of us are problem solvers and just check in to see if there are any interesting stories/problems where we can through our $0.02 and see if anyone likes our ideas.

Actually so was I but when I tracked them down, they're pretty popular.

 

Obviously I couldn't get that to work. How did you get it to go longer than 35 inches???
Well, now it works.
Working for 16 amps, the limit for U.S. outlets, and the 125 volts I get at my house:

88.75 inches of 22 gauge is real close to melting at 2500 F
142 inches of 20 gauge @ 1860 F
181.25 inches of 19 gauge @ 1660 F
222 inches of 18 gauge @1480 F
284 inches of 17 gauge @1280 F
and that's about the end of it.

I'll bet the mfg uses 3 hundred inches of 18 gauge nichrome for a clothes dryer and coils it to get it down to 4 feet long and stretchy.

was this nichrome 60 or 80?
17 gauge 60 = .33 ohms/ft
17 gauge 80 = .96 ohms/ft

Believe it or not, 17 gauge nichrome is proving difficult to find. what I did find is a buck a foot compared 18 which is practically free.

I'm wondering if 18 is a good substitute.
I'd run the same 300" at a lower temp. Unless there's not enough juice to do the job. Or I could be overcomplicating it in my head by looking at too many diff scenarios at once. I'm just damned anxious to order something and get to work. Plus, I'm out of town for a week without a comp. Stir crazy!

 

The chart lists the resistance of 18 gauge as .4219 ohms per foot.
17 gauge is displayed as .3333 ohms per foot.

Use the chart to find the proper length of 18 gauge wire. 223.75 inches.
That is the minimum length to use up 16 amps at 125 volts.
Make it longer and it will use less amps.

Your problem is that you are not using the chart provided. It isn't only us that can click on the link and move the sliders.

 

The chart lists the resistance of 18 gauge as .4219 ohms per foot.

Your problem is that you are not using the chart provided. It isn't only us that can click on the link and move the sliders.

I almost punched my computer in the face last time I tried to use that. But fair enough.

 

I failed on the first try, too.
See post #14.
Persistence, dude.