Poor Man's 200 Dollar Plastic Heat Strip for Pennies!




About: I'm an electrical engineer specializing in software. My hobbies consist of software, hardware, and design. I dabble with industrial design.

Want to bend sheets, tubes, sticks of plastic?
Don't want to buy a 200 dollar heating base?
Build one for pennies! (free if you go dumpster diving)

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Step 1: Materials and Tools

For a totally free unit, dumpster dive for these materials:
- Toaster oven (cylindrical, rod-like, non bent, heating elements)
- Sheet metal (I used old brass door kick protectors)
- Outlet plug (old extension cord or whatever)
- Light dimmer
- Wiring nuts (or soldering gun)
- Liquid electrical tape (optional)
- metal pipes (optional)

- Garden Shears (or anything that cuts sheet metal)
- Dremel or drill
- Pliers

Step 2: Dismantling the Toaster Oven

Rip apart the toaster oven. Bash it, unscrew the case, use the jaws of life, just dismantle the oven and retrieve the heating elements. Keep as many as possible, because you can make the heating strip as long as required.

Step 3: Building the Base/heat Strip and Wiring.

-Take the sheet metal (must be longer than the heating element, or series of heating elements if you wish to make the heat strip longer) and cut out tabs to be bent perpendicular to the rest of the sheet metal.
- Drill holes on the tabs to thread the heating element through.
- Wire one lead of the power cable to one lead of the dimmer switch, and the other lead of the dimmer switch to one lead of the heating element.
- Wire the other lead of the power cable to the other lead of the heating element.
- (Since the heating elements work on A/C current, you can disregard rectifying the current, and you can disregard which lead of the power cable goes to which lead of the dimmer or heating element.)

- Mount metal pipes (with nuts and bolts or cut tabs on the sheet metal and bend them in towards the pipe) parallel to the heating element, with an about 1 inch gap from the element.
- Apply liquid electrical tape to seal any exposed wires (don't want to be electrocuted. I used tape)

Step 4: Using the Heat Strip

Without the optional metal pipes:
- Turn on heating strip, adjust the dimmer for the right temperature (I usually turn it on all the way, then reduce the heat.)
- Hold the sheet of plastic hovering about half an inch over the heating strip. The edge of your intended bend should be parallel to the heat strip.
- Once the plastic starts drooping just the teeniest bit (you may also try and bend the plastic a bit to judge when it's good enough to start bending), move it away from the heating strip and bend. You may use a jig for definite angle bends. (I use square wooden dowels for right angles. I pin one against the bending edge and slide the other dowel under the soft plastic to fold and keep it at a right angle.)

With the metal pipes:
- Same as before, but you do not have to hold the plastic sheet while the plastic is softening, just leave it resting on the metal pipes.

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    46 Discussions


    Do you think this could be done using "long" halogen floodlight bulbs as the element? I'm just thinking they give out alot of heat, with the electric safely contained inside a nice glass case. and if done with only a strip exposed as mentioned below you would have a clear indication of where the heat was going as it would be going the same way as the light. I think I may have just thought of my first instructable.

    1 reply

    Reply 2 years ago

    Lol when I read Halogen lamp my thought went towards the Easy Bake ovens.
    Actually if you could come up with an instructable for such a lamp along with easy to use jigs to curve plastics (as opposed to a 90 degree crease. ) that would me awsome


    10 years ago on Introduction

    While using an iso-transformer could be a nice safety measure it is not necessary. Even commercial grade thermoforming heat strips typically do not use ac isolation. Think about it electric range burners do not use iso-transformers, they get direct ac line current through a thermostatic rheostat (which is what a light dimmer is). The same applies to toaster ovens. I speak from experience working in the plastics industry for many years. I have built multiple heat strips using the exact technique described in this article with great success. Just my $.2.

    6 replies

    I'm sure you are very experienced in the plastic industry, but you mathematics is clearly lacking; "$ .2" is twenty cents, not two cents. Just my $ .02. XD


    Reply 5 years ago on Introduction

    I'm sure you're great at mathematics, but your editing and grammatical skills are clearly lacking. You used "you mathematics" instead of "your mathematics," and a semicolon instead of a colon in your statement above. ;-)


    Reply 8 years ago on Introduction

    Since he has years of experience in the industry he's valuing his opinion at 10x the going value for opinions.


    11 years ago on Introduction

    Back in the 50s & 60s, all the kids I knew that put together model airplanes & cars had figured out that the transformer from their old electric train set would cut thru plastics like butter.. They just bent some appropriate sized wire into the most useful shape, screwed the ends to the transformer poles, and did all the custom modifications in no time. It took a bit of fiddling to move the plastic at the right speed & not burn it, but adjusting the transformer knob helped also. I doubt they could even sell electrain train transformers without a ton of sissified safety devices now, so probably a modern train transformer won't work without some real modification.

    5 replies

    Reply 11 years ago on Introduction

    Most model train transformers can't do the amps for this, and will cut out on you. Some (mostly older) ones will, but you risk overloading them and Bad Things happening... especially if you don't use a thin, high-resistance wire like an appropriate size of stainless steel fishing leader. A bunch of rc guys have gotten bad results with model train and doorbell transformers, especially when combined with random cutting wires. (Guitar strings, etc.)


    Reply 11 years ago on Introduction

    I wish I could remember the details, but we were only about 12 or 13 when this was going on, which puts it back to when dinosaurs ruled the earth. Al I really remember was the buzzing of this big black transformer as they turned the dial, and how the wire glowed bright red, and I think they had to dial it back to keep from making a mess of the melting plastic edge. Not being into the models myself, it was just an interesting thing to watch, for me. This was about 1958, and it might have been a more powerful transformer, since the kids I watched had unusually big model railroad setups, what we called "two-board" outfits -- several sheets of plywood and a lot of complicated routing & trains. They also used the transformer trick to cut up plastic to make little signs & buildings for the model trains. I believe they tried balsa wood also, but it burned too badly. Surprising we ever survived childhood without the EPA and the Consumer Product Safety Commission.


    Reply 5 years ago on Introduction

    Surprising we ever survived childhood without the EPA and the Consumer Product Safety Commission
    A lot of People down those agencies. But just think how many injuries would occur with the current status of greed in Corporations and other businesses.
    How many toys would be laced with lead and other harmful chemicals if the Government didn't step in and regulate those things.

    Some argue that the market would take care of that. I have serious doubts about that. I'm of the opinion that the insistence for more and more profits without those agencies would cause an unending cycle of lower and lower quality and safety.

    Remember how bad things got when the finance market was deregulated. And this was the second time that Wall Street caused a such a deep world wide economic downturn.

    If they do their job correctly, we will have all the advantages of a Free Enterprise System, without the disadvantages of a greedy capitalistic system. That takes proper balance, not limiting valid useful products and merchandise.


    Reply 5 years ago on Introduction

    OH look! I asked a question without using a question mark. I wish I could break that habit.


    Reply 11 years ago on Introduction

    Actually, considering we were all into serious salmon fishing (Washington State), stainless steel fishing leader was always at hand & might have been the "wire" I remember.


    6 years ago on Introduction

    Nice! I am cannibalizing the controls from the toaster also- the timer and temp controls are already there, so I am gutting it instead of smashing it [that comes later].


    7 years ago on Introduction

    Pretty awesome make-shift heater. Certainly a different purpose than these heaters, but still nice not to have to spend so much: http://www.regaltool.com/Drum-Heaters-Barrel-Warmers

    Just as a thought would this work for bending an arch into a strip of plexi-glass? If anyone has any idea's on how to get a peice of plasic into an arch please tell.

    2 replies

    I would imagine it might need a bit of trial and error if you are going to use an standard oven. a temperature of between 140-160 degrees centigrade works best  for rigid foam pvc sheets.
    An easier way in DIY situations might be to build a jig or former the required shape, and use a hot air paint stripping gun, applying localised heat and working your plexigalss around the Jig.
    You must clamp it in position and allow it to cool completely before removing it, If it is anything like rigid foam it will hold its shape.
    Thai plastwood have a series of guides to working with plastic. Check out: www.thai-plastic-wood.com/plastic-uses.html


    Reply 10 years ago on Introduction

    A while back, I wanted to bend a strip into a parabola, and was trying to think of ways to do it. I saw a video a while back where someone placed a sheet ontop of a parabolic dish and stuck it in the oven. For a strip, perhaps if you taped the ends so that you're adding tension (curves it parabolic like) and place it flat in the oven, that might work.