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Introduction

FUBAR Labs has an old Full Spectrum Laser 40w CO2 Hobby Laser Cutter / Engraver that was rebuilt in late 2011. The unit is based off of the "cheap Chinese laser units" that are easily found on eBay. It has a simple stepper controller board that hooks to a parallel port.  Working area is about 10.5" x 12.5".  Z-Axis/focus is manually set.



Currently the laser supports:

  1. Continuous Wave (CW) vector cutting/engraving
  2. Pulses Per Inch (PPI) vector cutting/engraving
  3. Raster Engraving



General laser cutting information can be found at Wikipedia. Dive deeper with links at the bottom.==Safety Considerations==

  1. USE COMMON SENSE. The laser combines high voltage, water, toxic fumes, fire, and dangerous invisible laser beams into one cheaply made and cobbled together unit. Lots of things can go wrong. Think about them and work to mitigate the risks to yourself, people around you, your workpieces, the unit, and FUBAR in general.
  2. Wear safety glasses
  3. Do not leave the unit unattended
  4. Be aware of the state of the laser. It could easily be on when you are not expecting it to be.
  5. Be aware of the potential for fires. Have a plan to deal with them.

TODO

  1. Ground the bucket
  2. Software laser power control (or at least some kind of digital power control)
  3. Water Flow / Temperature Monitor
  4. 4" - 6" adapter for exhaust fan

Startup Checklist

  1. Verify laser unit is off (Keys removed)
  2. Hook up ventilation to the outside
  3. Turn on power to Laser Surge Strip
  4. Verify Water Flow (as of 3/23/2011 there's no practical way to do this)
  5. Boot PC (Choose Ubuntu and the "Real Time" kernel)
  6. Power up 12v Supply
  7. Power up laser unit

CW / PPI Vector Workflow Overview Laser Workflow PDF

Image
  1. Have an idea
  2. Draw or import into Inkscape (Inkscape Setup Notes)(Inkscape Templates)
  3. Generate GCode
  4. Load into EMC2
  5. Verify GCode (remove z axis components!)
  6. If using PPI, make sure you use M3 S### -- with ### being the pulses per inch
  7. Run at high speed with laser off to verify job placement
  8. Check Focus
  9. Run on test materials (Cardboard works well!)
  10. Check Focus
  11. Turn on air assist compressor and set to 20PSI
  12. Run on final materials at final speed
  13. Check water flow and temperature while the job is running
  14. Verify air assist pressure (20PSI)

Raster Workflow

In addition to the above startup and below shutdown checklists, please follow the above vector steps concerning focus, air assist, etc.



Currently, raster gcode is made by hand. I recommend checking the README at Ben Jackson't Github. Additional notes on the Fubar config are here.

M3 S1         (enable spindle)
;M68 E0 Q0.2   (choose an engraving power) (this is not applicable to our laser, yet)
F720        (choose an engraving feed rate -- 720in/min is our max at the moment)
(Format: O145 call [pic] [x] [y] [w] [h] [x-gap] [y-gap] [overscan])
O145 call [999] [2] [2] [1] [1] [0.0033] [0.0033] [0.5]

This will find the file *-999.* on the desktop and print it at x=2", y=2" in a 1" square.



Press start in EMC2. If it can't find the file, it will pop up a dialog to select the file. Generally I just go that route and select a file.



You will want to fiddle with the power settings to get the best engraving effect, but do not exceed 16ma when you press the laser test button.

Shutdown Checklist

  1. Shut down laser unit (Press big red button; turn keys to off; remove keys)
  2. Shut down 12v power supply
  3. Shut down computer
  4. Verify water tubes are submerged (this is to prevent air from entering the system)
  5. Remove power from laser surge strip
  6. Clean up your mess.

Key components and Resources

  1. http://www.buildlog.net open source laser design, as well as a great forum that deals with laser cutters
  2. http://inkscape.org/ open source vector drawing program
  3. http://www.twot.eu/ Inkscape plug-in for creating "tabbed boxes"
  4. http://cnc-club.ru/forum/viewtopic.php?t=35  gcodetools, extremely awesome open source plugin for Inkscape that turns the vector graphics in Inkscape into gcode
  5. http://www.linuxcnc.org/ EMC2: Linux based, open source machine controller software.  This is what takes the gcode from Inkscape/Gcodetools and turns it into actual electrical signals, causing the stepper motors to move, and the laser to fire.
  6. Ben Jackson's EMC Configuration / HAL for rastering, PPI, and magic z axis

Other Interesting Links

  1. Inkscape Extension / Plug-in list
  2. Box-o-tron: http://www.thingiverse.com/thing:383 "makerbot" style box making script
  3. Possible extension for hatch fill of closed curves: http://www.thingiverse.com/thing:4943
  4. Article discussing PPI (Pulsing the laser) with an Arduino-based solution
  5. What Can You Do With a Small Desktop Laser Cutter?
  6. another box maker: http://www.keppel.demon.co.uk/111000/111000.html

Sources for Materials

  1. Lowes and Home Depot: they have 1/4" hardwood boards and plywood.  The hardwood is nice, but the plywood is not great for laser cutting
  2. buildlog.net "Sources for Materials" forum

Technical Reference

  1. Stepper Driver Reference

ScrewTurn Wiki version 3.0.5.600. Some of the icons created by FamFamFam.