A Thermal Copier is required for the Thermal Screen Printing process which I use in a Graphic Communication Technologies class I teach. Unfortunately Thermal Imagers are no longer being manufactured. As a result, obtaining one has become difficult.
There is a market for used Thermal Copiers on ebay and a few niche websites are selling old stock. But, each 10+ year-old machine can cost $750 or more. Instead of buying a machine that may not survive for much longer (with questionable access to repair parts) I want to explore an alternate solution…
I have started this page to document my best efforts to fix, to recreate, or to make a thermal copier.
Pictures of the Machines:
How it Works:
Thermally-Sensitive Materials – Special materials that are heat sensitive are put through the machine. When parts of the material are heated chemical reactions occur.
- Overhead thermal transparencies – These have a layer of Silver Salt/Silver Halide. When any part of it is heated that part turns dark brown.
- Riso Thermal Screen – These silk screens have a special emulsion on it. When heated, the emulsion burns off exposing the screen.
- Spirit Master Paper – ?
Internal Heat Lamp – A special lamp inside the machine heats the original image – a carbon-based photocopy – causing the black toner on the original to heat up (the white areas deflect the light and don’t get as hot). While the black areas of the original are hot, it is pressed against the heat-sensitive material. The lamp is only an indirect heater to the developing.
Exposure Time – The thermally-sensitive material needs __ seconds of heat at __ degrees for the chemical reactions to occur.
Heat Lamp – Carbon Toner heats up best from light with wavelengths of 0.7 – 1.2 microns, which is “Near Infrared” or “IR-A” light. A 1500 watt IR bulb generates __ joules of radiated heat and light per second.
- Carbon Toner Absorption Spectrum: http://www
1500watts = __ joules/hour = __ joules/second
(_ joules/sec) x (_% heating efficiency) / (_bulb length) = _ joules/inch-second
Heating Time – For the black toner to reach __ degrees. With a 1500 watt bulb it will take __ seconds to reach that temperature.
- Specific Heat of Toner: http://www
(_ degrees) – (72 degrees room temp) = _ degree change
(_ specific heat of toner) * (degree change) = _ joules
(__ joules) / (_ joules/inch-second) = _ seconds
Design Idea #1:
Two rollers are positioned like a laundry wringer. One roller is a glass tube with the Infrared Lamp inside to provide exposure at the point of contact. The other roller is a motorized rubber roller to grip the materials and feed it through. Pressure is applied downward on the rubber roller to hold the materials together.
This setup is similar to the “Apollo Portable Thermal Copier“.
Design Idea #2:
No mechanized parts.
This setup is similar to the original flatbed.
Test #1 – Infrared Heat Bulb:
I bought an Ir Heat Bulb (250Watt) from a hardware store and tried shining it on a Riso Thermal Screen + Photocopy. I had some success, but it took 15+ minutes from 4inches away and the results were not usable.
Perhaps this is giving off more heat than Ir light. I wish I knew how to tell what type of Ir this is producing and how much.