Re:Open-source metal 3D printer
by merrillii on Friday October 24, 2014 @05:09PM
(#8506009)
Heating things with a laser is not quite as easy as you might think. Different materials will absorb different wavelengths of light at different rates. So for example a 1um laser might not heat white polyethylene enough while it would melt black ABS. Hot air has the advantage that it is always a consistent temperature regardless of the material.
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Use a laser diode pulsed with pulse width modulation, at perhaps 1KHz, duty cycle < 80%. During the off period, view the hot area with two photodiodes behind different-wavelength IR filters. The ratio between the outputs gives you the temperature. Go closed loop on temperature.