Robert,
When I have a fully-implemented Z-axis, I often use Ryan’s focus script to find the BEST focus when my laser is already in place and operating on a machine. You start with the Z-axis height too close to the material to possibly focus and then run the script. It burns 10 lines, each 2mm higher than the one previous, leaving the Z-axis 20mm above where you started. If the best focus point is found within the 20mm you traversed you should see a “gradient”… thicker lines surrounding thinner lines. Then you count from the top down to the finest/thinnest line and lower your Z-axis by the linecount you counted times 2mm; i.e. 6 lines X 2mm = 12mm below where you finished. I personally believe that this is the best way focus a machine that is fully-functional and has a true Z axis.
The method I showed above can be done as soon as you unbox your laser module… especially if the PWM board is included. No engraving machine is needed. Just lay it all out on the table, hook the laser module to the PWM board and plug in the power brick, Then use the buttons on the PWM board to turn on “TEST” mode and it comes on at the lowest power setting (001) … you should see a dot. Sliding the module by hand, against a guide or some sort (a wooden ruler is great!), you slide back and forth to quickly find the general area of minimum dot. Fine tune by making smaller back and forth movements and you’ll quickly zero in on the best/smallest dot… just like tuning the note with a trombone slide or cello string.
Sure the same thing can be done when mounted on your machine. I just find it easier to look down on it all from above rather than bending down and looking sideways to try to read my measurements or make an adjustment.
There’s many different ways to do this, of course. I just like what Neje has done to supply everything needed to do a quick and dirty test of the laser… right out of the box.
– David