K40 Laser Engraver/Cutter Upgrade and Installation

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I decided to get one of the ubiquitous cheap chinese lasers and see what i could do with it.

I did not plan to reinvent the wheel on the conversion and setup of the machine as there is a lot of information out there pertaining to this.  I plan to document my conversion as it differs from the others both mechanical/electrical and cosmetic.

There are two basic variations of the K40, Analog Controls and Digital Controls.  I elected for Analog.  I found mine on eBay and it was $313 shipped from a California warehouse.  I will not bore you with the "here it is the day it arrived" pictures as it looks Just Like all the rest of them....

I elected to ditch the original controller and the lousy Corel Draw 12 and plug in routine as sourcing the program and then still not being able to vary the laser power in software did not appeal to me.  The universal opinion of the software/controller combination is "it sucks" and I never even bothered to try it.  The machine was only fired up to verify it worked.

I elected to run the SBASE MKS v1.3 a clone of the Smoothie Controller as the desired model of which was not available at the time I decided to purchase the las.   There are a number of variations on the Smoothie Ware boards, this and the.   There are a number of variations on the Smoothie Ware boards, this and the Cohesion being the most common.  Read up on Smoothie


Smoothie Clone The Sbase boardis readily available and generally costs around $50.   This is a clone of the Smoothie Ware board and so far seems compatible.  Expect some pushback on the Smoothie forums if you ask for help.  The people making this board have not played entirely fair with the open source practice.is readily available and generally costs around $50.   This is a clone of the Smoothie Ware board and so far seems compatible.  Expect some pushback on the Smoothie forums if you ask for help.  The people making this board have not played entirely fair with the open source practice. 

Setup of the controller was pretty straight forward and simple.  I had to flip the direction of the Y Axis stepper and make an adapter Y cable to plug in the X and Y axis Min end stops.

Along the way I purchased a kit of plugs and sockets for both the JST-XHP and the Black Single Row headers found on PC motherboards.  I also upgraded to a ratcheting type crimper for these as well.






  To facilitate connections from the board to the outside world I got a Micro SD Card extension and a panel mount USB B extension.  I designed the part with Fusion 360 and printed it on my 3D printer.

I have posted the file on Thingiverse

The SD Card Socket is a snug fit through the opening and a bead of super glue keeps it in place.

This give a nice finished look to the outside of the machine and allows for easy removal of the memory card as well as access to connect the PC during use.

I elected to use the LightBurn software, which I highly recommend!!


After a few months of use and frustrations with intermittent controller crashing I decided to run with a Smoothie Board which I finally found on eBay.  First step was to gut out the original controller and control panel.  After the ripping and tearing was completed, I commenced to update the control panel of the laser to support the Smoothie:

Control Panel I       Control Panel II

A piece of thin aluminum plate was machined on the CNC mill and then covered with a sheet of polyester Laser printed material so the labeling would look nice and professional.  Now that I have the laser and if I were to remake the control panel, I would use Cermark to burn the labeling onto the aluminum plate.  Right side image shows the back of the display prior to the commencement of the wiring.  The original (shown here) was replaced with one that had a full scale of 20ma as the tube current would typically be 15-16 ma.



Control Panel III         Control Panel IV

  The original Pot was re-used along with the master On/Off switch.  The E-Stop switch has not been wired yet in this view.   The E-Stop kills everything but the chiller and cabinet ventilator.  Right side shows the functional panel in operation.  The small digital display in the upper left is for a thermocouple that is installed in a whirly-gig flow meter behind the unit that provides a visual indication of water flow.  As a rule the meter on the control panel, sensing the output temperature of the tube runs within  a half to one degree of the chiller's temperature display.  I could not resist the homage to Douglas Adams...



Smoothie Board Test   Smoothie Board on Adapter plate

Then I installed the Smoothie Board.  When I first tried to do this the 4 channel board was universally not available and the 5 channel quite a bit more expensive than I wanted to invest.  Adventures with the controller cherishing with the Maker Base unit really taught me a lesson.

Here is a bench test of the Smoothie Board 5C.  On the right is the board mounted to a metal plate that allowed me to use the original mounting holes in the cabinet, keeping the outside neat without any extra holes.  For anyone interested, here is my final configuration file.  Bear in mind, the configurations include the settings for a 4th axis, which I am using for a Z Table, described later.


Power Panel II   Power Panel I

Next was to get rid of the cheesy power input socket on the back of the  unit and add some power output.  Multiple outlet sockets needed to be added to control the Chiller, Vent Fan, Air Assist and a Vacuum Pump.  The vacuum pump is for fixtures to hold flat plates.  The input receptacle was replaced with a heavier duty model that does not have a light duty fuse holder incorporated.  A fuse holder was installed in a more convenient location on the right side of the cabinet.


Sliding Platform   Vent adapter

A drawer type platform was installed to allow easier access to the back of the machine and also to allow long pieces of stock to be cut in my plate shear which is mounted to the bench to the right of the laser.  I 3D printed an air duct adapter as the supplied ventilation blower has been known to fail early in life.  I mounted an inline 4" duct fan under the wall cabinets and used flexible foil duct to connect it to the outside vent fitting installed in the wall.


Vent Hose Connection    Chiller

Here's the adapter and duct installation.  Tube cover was removed to facilitate the installation.  The unit is rolled out from the counter, this shows how the moving platform facilitates access to the rear of the unit.  The chiller is shown at right.  I elected to get a "real" chiller that has a compressor to help keep the tube cool.  The smaller chillers that are more commonly available are thermo-electric Peltier units.  The unit holds 8L of water.  I use distilled water with a couple of ml fish tank algicide.


Dlow Meter 

The whirly-gig flow meter.  Decidedly low tech, but gives an immediate indication of water flow.  The thermocouple for the temperature display in the control panel is mounted here.  The flow meter is mounted in the return line from the laser tube.  I use the temperature display on the chiller to indicate the input temperature of the cooling water to the tube


Z Table

The original working platform that was installed in the laser was basically designed to hold small parts for engraving.  Most of the working area was lost.  I removed this and then designed and built a Z Table that could be controlled by the software.


Z Table Bearing Supports   Z Table Assembled Corner

I 3D printed four corner brackets which us pairs of "skate board" bearings.  Pockets were sized so the bearings are a mild press fit.  Short pieces of Acme lead screw and some timing belt pulleys complete the assemblies.  One end of the four shafts were drilled and tapped for 10-32 machine screws to hold the shaft into the bearing packs.  I used Helicoils to provide a tight grip of the screws that hold the corners to the bottom plate.  Is is actually not needed, but as I was designing this as I built it, I figured I would be taking it apart multiple times.  This proved to not be the case.


Z Table Assembled I   Z Table Assembled II

Top side shot before the upper deck has been installed.  Top and bottom plates are made from 1/8" aluminum sheet.  Simple belt tensioning setup eliminates the need for precise motor placement and/or belt calculation.  Drive is a 2:1 reduction.  The four neodymium magnets hold the table into position in the bottom of the cabinet and make it easy to remove if needed.  Future plans for a rotary fixture made me think about the ease of which I could change the work area.


Hole in Cabinet   Z Table Ready to Install

A dam made from Frog tape was used to contain the chips while drilling the hole to clear the stepper motor.  I elected to have the motor protrude from the bottom of the table as opposed to hanging out to the side.  This allowed the table to be larger in width.  In the right shot, the magnetic feet have not been installed so I did not have to fight them while setting up the location and other issues. 


Upper Limit Switch   Lower Limit Switch

Detail of upper limit switch mounting.    Striker for the upper limit switch attaches to the frame of the laser.  Right side shows the lower limit switch and adjustable striker.  To maximize the travel the adjustable stop was implemented.


Upper Limit Switch Striker   Upper Limit Switch Striker Installed

The strikers are make to be interchangeable depending on which work surface is being used.  Neodymium magnets are used to hold them in place.  The threaded rod allows fine tuning to the adjustment to achieve good focus on the part.  When starting the laser, i run the Home All Axis command in the Smoothie Controller.   The focus is set to the top of the work surface being used and during use the thickness of the material is entered into Lightburn.  The Z table politely moves the required distance when the job is run.


Striker Assortment   Z Table Fences

The assortment of strikers is stuck to a metal bar behind the laser.  The colors are arbitrary and were based on what was loaded in the 3D printer or my mood at the time.  For different work surfaces or fixtures there will be a specified striker.  In the case of a fixture that is placed on the bare bed or the honeycomb substrate, the Home All function is run with the specified striker.  I also added a fence at the X0 and Y0 edges of the table.