It feels a bit strange to be working on my projects in the midst of this Covid-19 crisis but since the advice is social distancing - I guess it is an appropriate activity. Hopefully isolation will slow the rate at which the virus is spreading so that a mitigation strategy can be implemented.
I've been working on my low power (5.5W) laser setup that I've described in previous blogs. I've recently been doing some lightweight cutting of 2.5mm thick craft wood. I've been using a scrap 2"x4"x5" block of wood to cut against but I need something larger for general purpose cutting and also should use something that doesn't burn.
Here is the setup I've been using. You can see the burn marks from cutting a square and also where I burned through when I was adjusting settings for engraving cardstock.
The bed of the CNC base is 7 inches deep and 12 inches wide so I got a 6"x12"x1/8" aluminum plate and drilled mounting holes at the corners. I also used some 1/4-20 hardware and some springs so that I could have the capability to level the bed. Here's the parts along with some guides that I printed to do material alignment.
And the finished assembly.
To provide a convenient way to make the leveling measurements I printed an adapter for a Digital Dial Indicator Gage to mount it to the spindle holder.
I'd like to have a way to do the laser focus calibration automatically so I've considered buying the serial interface cable for the dial indicator but I want to see if I can use a mini Lidar time-of-flight sensor instead to do a non-contact measurement. The absolute accuracy of the TOF sensor at 40mm is probably only 2mm but I'm hoping the measurement repeatability would be good enough to use for focusing. I'd like the repeatability to be about +/- 0.25mm but I think +/- 0.5mm would be okay. The other accuracy problem would be the reflectance of the material I'm cutting/engraving but it would be fun to give it a try.