After building some Laser engravers with small diode lasers i finally decided to buy one of these cheapo china 40W CO2 hellfire machines - knowing that they were dangerous in terms of bad electric, high voltages and powerful invisible laser rays.

As said, i knew of the existing problems but with my experience and some research i was confident to be able to deal with that.

K40 40W CO2 Laser Cutter from eBay i choose the orange one with the analog current meter, as i like the color and it was the cheapest ;_)

Once the machine was electrically secured, well grounded and unable to fire the laser with the lid opened i did some test cuts and started taking apart the whole thing to do the modifications i had in mind.

• Extending the working area of the laser to the max possible within the steel case of the k40 (involves new mechanics and moving all electronics to the back)
• Replace the control board by one that is working with grbl and Lasergrbl.
• Change the water cooling to a closed system with a radiator to cool the water.

• Bosch Type 20mm Slot 6 Motedis.de or Banggood.com
  • 1x 2040 750mm
  • 2x 2040 380mm
  • 2x 2020 807mm
  • 1x X-Motor NEMA17 mount
• Various Slot 6 nuts for M3/M4/M5 as well as screws in different lengths

• 1x MGN12 700 or 750mm
• 2x MGN12 350mm
• 3x MGN12H carriage block

• 2x GT2 20T 5mm bore
• 1x GT2 20T 8mm bore
• 3x 20T 5mm GT2 Timing Belt Idler Pulley
• 1x Coupler 5 to 8mm
• 2x Linear Bearing 608
• ~800mm 8mm linear rod
• ~4m GT2 belt

• SC 300T Water Pump
• 240mm Radiator with 2 Fans
• Flow Meter with Thermometer

• Cheapest Air-Pump available
• Power regulator for Pump as it only needs ~10-20% of power to not blow away your parts and overheat.

• 4x T5x2 Trapeziodal screw 100mm
• 4x T5x2 Trapeziodal brass nut
• 4x 20 teeth GT2 Timing Pulley Bore 5mm
• 1x GT2 Closed Loop Belt 2200mm
• 1x 360 Degree High Torque Metal Gear RC Servo Motor

• Mechanics: https://www.tinkercad.com/things/gVlVbyzbIc4 some parts are taken from: https://www.thingiverse.com/thing:3401855/files
• Cooling: https://www.tinkercad.com/things/bzq5l8KrbZv
• Z-Bed: https://www.tinkercad.com/things/4Zyxo3jcf69

• GRBL compatible Board. e.g. MKS DLC 2.0
• BUZ11 FET to control the K40 PSU via PWM - see pics below for wiring. Taken from: https://forum.makerforums.info/t/grbl-1-1f-config-with-prontoneer-cnc-shield/9155/9

First Testcuts

First Engravings

• https://hackaday.com/?s=k40
• https://lasergods.com/
• https://k40laser.se/
• http://replicantfx.com/k40-laser-cutter-rebuild-12x24in-2/