Question before purchase. I am adding an 80w laser to my existing cnc. I will cut up to 3/4" acrylic and engraving. I spoke with someone and was informed that when engraving the 50 mm lens will work ,and use 75mm when cutting 3/4" acrylic. I was told to accomplish this I could just exchange the lens in the laser head. To be clear there will be multiple passes in cutting the 3/4" material My question is if I have the distance between the laser head and material set do I also adjust "Z" height when exchanging lenses for cutting different materials. My second question is in cutting multiple passes what issues will I encounter, that is quality of cut, burning etc. What procedures should I have in place to successfully cut materials. One answer on the forum was to raise the "Z" inbetween passes. Is this necessary and what parameters are used to determine the amount of change. Thank you for your help in building this project. Tony wish In-Tech Systems