home built laser system

Posted on Feb 7, 2014

I have developed an inexpensive control system (less than $70) that can be used to both get more cutting power out of a DC discharge laser and significantly improve cutting accuracy for home built laser systems. The control system implements a control technique known as Pulse-Per-Inch (PPI) control. PPI control involves pulsing the laser every tim

home built laser system
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e the head travels a certain distance. PPI control allows a CNC laser to produce consistent cuts at the same power level setting over over a wide range of speeds. In effect, pulsing the laser as a function of distance along a cut decouples the power input to cut from the speed that the head travels. Therefore, the speed and acceleration of the CNC system have minimal bearing on the cut characteristics. Furthermore, the unique transient rise response of a DC discharge laser allow PPI to deliver more power to a cut in comparison to the same laser system with just on/off control. A while back, I was active on a forum in which we were discussing the time it takes to turn a laser on and off and how that relates to engraving control. One of the forum members from Full Spectrum Engineering posted a high-speed intensity spectra for the cheap DC discharge lasers that we use for DIY laser cutters. I was quite surprised by the spectra. I expected to see a nice exponential rise to set power level, but what we saw was a rapid rise to a very high power level (nearly double the set value) followed by an exponential decay to a set value. The Spectrum in question is shown below (credit for the spectrum rests with Full Spectrum Engineering). The yellow square wave is a 5ms pulse sent to the laser power supply. The green spectra is the intensity spectra of the laser. For whatever reason, the magnitude of the spectra is upside down (I think...

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