Build a plastic heat bender or Nichrome controller
August 26, 2013
I am attempting to build a thermal plastic bender to create mounts and parts for my robots. Basically a piece of nichrome wire heats up a small area of the plastic which allows me to bend/form it by hand. The nichrome wire I have, came out of an old space heater. It is formed into 1/4 inch coil. I don't have a clue to the metal contact or diameter (pretty darn thick since it was an old heater.)
I tried connecting it directly to a 12v 2.6 Ah SLA battery. A short section of about 6 inches coiled. The direct connection proved to be too much current and almost instantly brought it to a bright glow. Probably 2-3 seconds before I disconnected it for fear it would burn out. Much to hot to use for plastic forming... Smelting gold, maybe :-)
The examples of the bender I have seen use a variac transformer to control the current. I don't have one, so my question is, will an adjustable power supply using a variable resistor / lm350 circuit have the same type of control 'dimming'/reducing the heat (or am I way off on the concept here?) using a circuit such as this: http://diyaudioprojects.com/Technical/Voltage-Regulator/
I am learning as I go, so I may be totally off in this application. But it seems it would act the same for a dc battery driven circuit (instead of an ac driven variac transformer.)
Here is what I think needs to happen.
The original heater had a type of thermostat to control the heat. Heat sensitive wire would allow contacts to close and send power to the coils. A type of mechanical voltage control. I can't place this 'thermostat' into the project. It would interfere with the plastic being above the heat source. So I am attempting to control the heat radiated by reducing/increasing the voltage to the heating element.
Thanks for any assistance.