My goal with this design was to have the laser be easily attached and detached from the printer, while being secure and stable, and allowing for a maximum of the build platform to be available. The mount slides under three of the four screws on the top of the extruder assembly for ease of attaching and detaching. I added connectors a foot or so above the mount so that the main part of the cabling for the laser and fan can stay attached to the printer between uses. I can change between printer and laser cutter in about a minute.
I am using the PWM controlled fan from my Ultimaker to drive the laser. This posed a little bit of a challenge because there are two fans driven in parallel and if one is out of the circuit then you have no fans. The driver effectively takes a fan out of the circuit so I needed to put a DPDT switch in place to swap between printer and laser. The over challenge was that the Ultimaker 2 drives fans at 24V and the driver wants 5v. A little voltage divider and that problem was solved and the voltage the driver sees is now about 6v maximum.
One last problem that will likely cause me to move to the LED PWM...when the fan is activated there is a spike of voltage! Not sure why but it is enough to be noticeable when the laser fires and in the start of the burn.
In the next post I am going to talk about calibration and my first cut.