I bought the JTECH 3.8W laser. Was originally planning the 2.8 one, but I hadn’t been to the site in a while and just saw the more powerful one. Figured why not.
To get the stickers off, mineral spirits will sort of work and acetone will definitely work. Just be careful that you don’t get acetone on any table or floor finish or any ABS parts if any.
It is easy to create a gcode file that just does a few dozen mid air squares at the limits of your machine and moves the Z up and down. This will really smooth out the zinc coating on the conduit.
Alan, A very simple and even more stupid-sounding question: Did you ever calibrate your printer? Sounds to me like it is somehow off a precise 1:1 scale. Make a few simple boxes with defined dimensions and measure them - if you haven’t done that already. If you have, repeat the test, just to be sure. All three axes.