K40 Adjustable Focus Head-Quick focus guide tools

thingiverse

When I purchased my K40 Laser machine, a Chinese clone available on the flea market, I decided to overhaul it from scratch. It had never been used with the defective software or powered up with the main PCB. Everything was removed, completely re-wired, and is now powered by a GRBL "CNC" nano controller. This upgraded model features 255 gray-scale engraving capabilities and several safety-related upgrades: a water coolant flow switch, door open switch, digital coolant temperature display, and current display. These are essential components that should have been included from the start but were omitted due to Chinese profit margins and tight budgets. I also upgraded the mirrors and cutting head, where a small issue arose - setting the correct height. The head is focus adjustable, but most tools on Thingiverse wouldn't fit or be usable without precise measurements. Time to calculate distances and create a user-friendly guide tool to help set the correct focal point for surface etching/engraving and cutting 1-10mm thick acrylic and wood. The lens in my cutting head is located deep within the air assist nozzle assembly (40.95mm from the bottom exit hole) and has a focal length of 50.8mm. With these starting numbers, I can design a simple tool with graduated steps for setting the correct depth for cutting different thicknesses of wood and acrylic, as well as the exact level for surface engraving. This guide may be of no use to others, but it's a step in the right direction for anyone wanting to remix or adjust this tool. No two air assist focus adjustable heads are exactly alike, even though they're produced similarly. The rubber O-ring between the lens and body (air seal ring) varies in size, so precise measurements are necessary to get the correct numbers for creating your own guide. These tools are designed for a fixed lens setting of 40.95mm (one picture shows measurement details). The original tool is available on Tinkercad, where you can clone it to your account: https://www.tinkercad.com/things/lmg8WSInKae or import the STL into a CAD package and tweak the settings before printing. Four different sets are included: * K40_Quick_focus_guide_V: a vertical stacked single block * K40_Quick_focus_guide_H: a horizontal stacked single block * K40_Quick_focus_guide_nn: an individual key-style model with a keychain hole * K40_Quick_focus_guide_fs: a full set of individual key-style models ready to print in one go This tool can be printed using FDM (2 shells and 10% infill) or resin (if hollowed and vented, "not tested in resin yet").