Laser Rebuild – Part 7 (Finishing Up)

Now that the laser is firing all the way through the beam path and the path can be controlled by the computer, we’re down to the detail:

Controlling the Laser

I don’t have too much to say here because I got incredibly lucky and someone else did all the heavy lifting for me.

Users on Buildlog.net have done lots of work making it possible to control the laser from EMC2.  User BenJackson has published his configuration files and adapting them to my machine was a piece of cake.

His configuration file includes a custom HAL component that does PPI (pulse per inch) control.  With this configuration, I have three “knobs” I can turn to adjust how the laser cuts or engraves material.

• Feed Rate controls how fast the laser is moving over the material
• PPI controls how many 3ms pulses are delivered for each unit of travel (inch or mm)
• Laser Power.  EMC2 can vary the PWM signal to the laser power supply to control the power delivered to the tube.

By playing around with these three, I’ve found I can go from drawing a light brown line on a piece of paper all the way up to burning clear through 5mm wood or 1/4″ acrylic!  Very Nice!   I’ve got plenty of learning still to do but it’s looking good.

Cooling

The basic buildlog setup is a 5 gallon bucket of water, and an aquarium pump.  I need to tidy up my setup but it’s working for now.  The only part I’m missing is a flow switch.  The control card has an input for a switch that is tied into the safety interlock.  It should prevent the laser from firing if the water isn’t flowing.  I don’t have a switch yet so I’ve hotwired around it.  Not good.

 Shroud

The glass tube hanging off the back makes me nervous.  I’m not sure if there’s any dangerous radiation emitted from the sides of the tube, but I’m not taking any chances.  Besides, it’s just a matter of time before I drop the broom handle or something else on to the tube and bust it.  I had a local sheet metal shop bend and weld up a shroud that fits over the tube and screws to my mounting rails.  After painting it, I think it came out nice.

Exhaust

When the laser is burning anything, and especially plastics, it puts off a lot of smoke and foul smelling crap.  I have a big dust collector for the CNC machine.  I’ll add a drop near where the laser will end up so I don’t have a dryer hose trailing across the floor.

And the results?  This is 1/4″ plywood cut through.