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With the torch able to "float" up (like a shock on a 58 Buick Roadmaster), when it moves towards the material and the tip hits the top of the material, it shoves the torch (and holder) up and trips the switch. The distance it has to move between first striking the plate and striking the switch is overtravel (switch offset) and remains the same as a constant. That value then is put into the POST as a constant (variable) that is used to raise the Z the correct amount each time (4th step above)
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TOM CAUDLE
www.CandCNC.com