K40 Laser Engraver/Cutter
This is the "classic" inexpensive Laser Engraver Cutter from China.  Similar lasers that do the same thing (but better and more repeatable) cost $3000 and up.   This one cost $600 CAD.  It is known affectionatly(?) as the K40, 40 being the power of the CO2 laser, 40 watts.  There is a great following on the Internet for this tool.
Here are some "as delivered" photos.  Hover over a photo for description
Back of laser showing laser tube, has to be water cooled.  Water tubes at bottom center go into the reservoir where there is a fish tank pump.  The big hole on right side is blower outlet to get rid of smoke and particulates.  i have a large hose attached to vent to the outside
Power supply inside the right compartment  5V, 24V, and 40,000 volts
Control panel.  E-stop, key start, and digital power control.  I'm replacing the bottom part of this panel.
Just unpacked, film protecting window
Panel wiring...pretty basic
Original control board, replaced with Cohesion control board.
Post it Note used to see where the beam hits.  It should be dead center
Pile of post it notes used in one session.  Very difficult to do alignment.
Instead of notes, which fell off, I started using masking tape.  Note the black holes where the laser hit and burned the tape
Engraved and cut wood and acrylic
Letters cut out of foam.  Try doing this with scissors
First real job, to make a diffuser for a camera photo light.
I tried engraving on a mineral sample
Piece of foam I cut out.
Wood star, painted yellow
Duct tape on wood, engraved
Engraved with too much power: made a stencil.
Perfect square cut in 1/8" acrylic, can't get it this fine any other way (like filing and sanding)
This heart cut out of plastic duotang cover
1/8" wood cut with laser. It burns it but is so quick and precise, the cut gets made without rough edges.
I spray painted  some wood, then cut out pieces
Vinyl material
the "20" is about 1/8" high!  Note how sharp it is.  I put white paint in it as a test for future
Wood cutouts from above, with engraving
Hardwood engraving, note the sharpness of the "print".  Full photo below
Made this for Valentine's Day, 1/8" acrylic sheet
Vinyl covered ceramic magnet material
kichen tile engraved perfectly
Raster engrave on wood.  I can do better, this was a quick test.  This is from photo of Sunshine.
Engraving on wood
Engraved a small clip board, hardwood.
same clipboard
Manila file folder cardboard cutout of a new panel I'm making.  This is a perfect way to test fit parts like switches before committing to cutting into more expensive material.
engraving on hardwood.  this stuff is great to work with.
another raster engraving of an image, on wood.  This is Queenidog.
Made this "Air Assist" nozzle on 3D printer, blows smoke away from the laser burn
Bad, cheap, limit switch to shut off laser when door opened.   Found it enabled by panel on right side because of the sloppy fit.
Better, more robust, and away from the edge for more positive engagement
original laser head.  There's a mirror in the top and a lens in the bottom
Better head with bigger lens and air assist hose input
Better lighting for the cutting platform, when door down.
mirror#2.  chinzy mount, hard to adjust mirror postion
cheap original mount next to nicer/berter machined unit.
new mirror mount installed
Thursday, March 10, 2022
I am a hacker.  Now that I have everything working, I changed a bunch of stuff, to make the $600 engraver into a $1500 engraver. 

Copyright 2022 Queenidog - All Rights Reserved
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As built (as delivered)
Sunday, April 24, 2022
The first order of business was to align the mirrors.  There are two stationary and one moving mirror to get the laser beam to where it can do some work.   The beam must be sharp, precise, and perfect at all corners of the work area.  (Hover over photo for description).  Very frustrating procedure.  Every once in awhile when the laser seems to be faltering at the far right side (most out of focus), I check and must realign mirror 2.

Sunday, April 24, 2022
Coreldraw and a program called LaserDraw comes with the tool, but before I even started, I read on numerous web pages and YouTube to throw these out and use the free drawing program called Inkscape and laser control software called K40 Whisperer.  The latter is a very simple program that all users should start with, then upgrade after they know how everything works.  I used the Whisperer many times, then upgraded to Lightburn software used with the Cohesion 3D control board.  More features and better control, plus only one program needed, not two.

Work Samples
Sunday, April 24, 2022
Below are a number of items I made with the freeware.  In each case I was testing the laser on a particular product: leather, wood, painted metal, leather, etc. and making notes on: 1) material, 2)Raster engrave/Vector Engrave/ Vector cut, 3) power used, 4) number of passes, and finally, 5) Result description.  At the end of my spreadsheet I put a checkmark or an X, to indicate Go or No-Go. 
Future Enhancements
Sunday, April 24, 2022
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Screenprint of design made with Lightburn
Panel cut out of 40# paper, to test part placement
I first tried engraving red acrylic then filling the cuts with white paint.   Didn't turn out well.
Panel cut out of 1/8" white acrylic
Red enamel paint over white acrylic
After engraving painted panel (red on white acrylic)
Original control panel
Testing after wiring
Panel wiring
Laser current meter.
New water termperature gauge
Control Panel
Sunday, April 24, 2022
It seems that most who buy a K40 have the need to modify the control panel.   The original is kind of lame with no individual control over the auxiliary equipment, like air purge, extraction fan, water pump.   All these  would start when the key switch was turned on.

I made my panel out of 1/8" acrylic and used switches and relays to control equipment.   I KEPT the digital panel (upper right in photos below), unlike most who ditch it in favour of a potentiometer to control the laser current.

Hover over a photo for description, photos are in order left to right.

Copyright 2022 Queenidog - All Rights Reserved
Video of Laser engraving Darth Vader Mayan calendar