K40 Laser – First 48 Hours

I recently bought an Ortur Laser Master 2 which is marketed as a 20 watt laser but it is truly about a 5 or 5.5 watt output power diode laser.  It’s an amazing device for engraving wood and cutting thin materials.  In other words it has some limitations.  I’m having so much fun with it but the forums are full of stories of parts failures.   If you have a hobby device and it fails it’s not the end of the world, however if you are making money with the device you probably should have a 2nd one at the ready, or at least buy spares, such as another controller board and laser module.

So that’s where I’m at.  I made my first couple of sales and I realized that if I can make a buck or two I’ll lose credibility real fast if my machine goes down and I can’t deliver.  So I decided to pick up another machine.  After all they are cheap.  Around $300 or so.

K40 Mini Laser

Then I (re)discovered the K40 Laser.  K40 isn’t a name brand but rather a gigantic swoosh covering a range of inexpensive cloned Chinese 40 watt CO2 lasers.  K40’s are made by several manufacturers and sold by untold number of secondary retailers especially on the Chinese electronics websites (Aliexpress, Banggood, etc.) and eBay.  The quality range varies from great to absolutely horrific.  You need to carefully source your supplier and do lots of research before buying one of these things.

That being said, these machines are a platform for upgrades and lots of the people who buy them don’t much care if they work or not.  They will make them work and improve and upgrade them in the process.   In fact I’d love to find one broken that someone was selling for a song.  After 48  hours with this thing  I’m pretty confident I could rebuild one and repair parts can be sourced cheaply.

What you get with a K40 is a very basic CO2 laser with an output power of 30 to 40 watts, which is substantially more powerful than the diode lasers.  Remember I said the Ortur was a 20 watt laser?  That is the input power.  Also a K40 can be had for just a little bit more money than an Ortur Laser Master 2.  The price seems to vary from about $350 to $450 or so.

Finding a reputable dealer is tricky.  If you know anything at all about China or Chinese businesses they’ll slap some crap in a cardboard box, take your money, and then be evasive as hell when you need help.  Lasers are pretty complex devices that require alignment especially after a trip around the globe, so generally you’ll receive a device that you will have to COMPLETELY set up and align yourself.

There is one company though called OMTech who imports the lasers from China and then runs them through an upgrade and quality assurance process.  Most of the time on the internet you will hear people say that their OMTech Laser worked right out of the box and was aligned properly.  Plug and play.  Not so with a lot of eBay retailers.   Also because they are US based you’ll get your laser in days instead of the usual weeks or months it takes to import something from China.  I bought mine from their eBay store and received it in 3 days.

A whole community has sprung up around the K40 and it has been a viable platform for a few years now.  The laser is cheap, which makes it a prime candidate for hackers and makers to employ their skills on.  A few key, and inexpensive upgrades and you have taken a very basic laser to a whole new level.  It is a very capable device.

The “big” K40 seems to have been phased out (or at least it looks that way to me) and has been put in a smaller case which they called “the upgraded version” and which the forum dudes call “the Mini”.  The only real difference though is the size of the laser tube that comes with the unit.  The mini has like a 633 mm long tube and the K40 of old had a 700 mm tube in it.

TRANSLATION:  Longer tube = more power.

You can still put a 700 mm or even bigger of a laser in a K40 mini but it will stick out of one end a little bit.  There is a removable cover that allows for this and of course people have designed covers to protect the longer laser tubes.

So that is a brief rundown on the K40 as I understand it.

I decided to go with the OMTech K40 Mini which has a drag chain, and laser dot guidance which are two major, must do upgrades.  It does not have an Air Assist but I have 3D printed one up but just haven’t installed it yet.  My intent is to not do any upgrades until I ensure mine is working perfectly for at least a couple more days.

The “new” lasers from OMTech are branded as “Preenex”.  I think the general consensus on the laser forums is that OMTech Preenex stuff is pretty good to go.

Software support is kind of dodgy though.  The Chinese send some software and most video reviews show the reviewer chucking the software in the trash.  It is some kind of cracked Corel Draw version I believe.  What most people use is the Open Source software program called Inkscape and laser control software called K40Whisperer from Scorch Works which is also free.  it is a very adequate software mix but there is a learning curve.  I figured it out pretty quick.  You have to draw red, blue, or black outlines on your intended cuts in Inkscape for K40 Whisperer to interpret the cutting or etching.   It sounds harder than it is.

Bar none, without question, cause, or doubt though the BEST LASER CUTTING SOFTWARE IN THE WORLD is something called Lightburn.  It is NOT free and costs $40 forever however you lose the ability to upgrade the program after 12 months.  Seems there is an annual fee after that if you want the latest upgrades.  Hey, upgrade every couple of years or when a new, must have feature gets delivered.

Okay, here is the problem with Lightburn as it relates to the K40.  It DOESN’T relate!  The K40 uses a controller card called an M2Nano.  Lightburn won’t work with that card.  What you can do though is to upgrade the controller card.  One somewhat inexpensive solution is called a Mini-Gerbil from AwesomeTech.  Take the M2Nano out and drop in replace it with the Mini-Gerbil and suddenly your K40 works with the best laser cutting software in the land.   This of course turns your $400 machine into a $500 machine.

Before I set it up I 3D printed a 4″ round exhaust fitting and cut a board to fit my window sill to exhaust the cutting smoke and fumes outside.  Still needs some weather stripping on the ends, but you get the idea.

Exhaust port for K40


Also I picked up a 5 gallon bucket and some distilled water to circulate through the laser tube.

Setup was a snap and only took a few minutes.  First make sure the water flows through the laser tube, and that there are no leaks or big air bubbles in the tube.  Ground the unit, plug it in and connect the USB to the computer.  Whoops, almost forgot the exhaust port vented outside.

OMTech Preenex Branded K40


One of the most gigantic headaches users have is aligning the mirrors.  My machine had perfectly aligned mirrors right out of the box.  Not only that the mirror screws had RTV sealant or a tamper seal or something on them.  Good quality assurance step by my estimation.  Here’s a quick video showing the alignment.

Within a few minutes I was using the free software K40 Whisperer I talked about earlier and made a raster, a vector and a cut.  It’s obvious that I need to spend some time learning about the settings and speeds and getting used to the nuances of the machine.  It is different than using my Ortur Laser Master 2, that is for sure.

I did have one humorous moment setting it up.  There was no power whatsoever to the unit.  I’m an electronics Tech Rep for DOD so I started troubleshooting.  I decided the Emergency Stop safety switch or power switch was bad.  Called OMTech Support and the tech asked me if I had disengaged the Emergency Stop switch.  “Huh?”.   He said “Push down and turn it” and sure enough it popped up.  And then it worked!  Oh Dopey Me.

E-Stop Unlocking

Oh well.  I told my story on the K40 Facebook group and to my surprise a whole bunch of people admitted to the same sin.  Some more technically advanced than me.

I really can’t say enough good stuff about OMTech though.  There are some real horror stories on the internet regarding K40’s and of course a lot of people gravitate towards the cheapest price they can get.


My laser from OMTech was shipped very quickly, arrived undamaged, and VERY well packed. Again the mirrors were aligned to perfection and the laser seemed focused at the height I used for cutting (just over 50mm).

Here’s a thing or two or five that I don’t like:

  • The paint job is awful.  It looks okay but I went to give it a wipe down with a paper towel and a drop or two of isopropyl alcohol.  The chalky paint started transferring onto the paper towel.   No harm, no foul, but shitty paint obviously.
  • The tactile buttons on the control panel look sketchy, all uneven and wonky looking.  They all work but it looks like pretty cheap membrane push button material.
  • The laser tube has clear tape on it to hold stuff down during shipping and I just left it on the tube.  Taking it off would have surely removed all the warning stickers and I see that most people just leave it on as well.
  • The built in exhaust fan is okay but nothing to write home about.  My understanding is that this newer fan assembly is way better than previous K40’s.  I can only imagine what a joy that must have been.

Still, for $400 this guy is a bargain.  The only thing it lacks upgrade wise is an Air Assist and an analog milliamp meter.  There are a bunch of folks that swear you need the milliamp meter and of course some other folks that swear you don’t.  The crowd that says you need it seems to outnumber the ones that say you don’t though.   I bought an upgrade card called a Mini-Gerbil that seemingly does the math for you and allows you to control the intensities from software (Lightburn).  If you plug in to the machine that 18mA’s is 100% power then  the software will do the rest (until the tube gets older and weaker, then you can adjust numbers if necessary to reflect laser power in a weakening tube).

So here is the real deal.  If you have an M2Nano card you NEED a milliamp meter.  Install one.   If you have a card such as a Mini-Gerbil that sends gcode commands a milliamp meter is redundant.  It doesn’t hurt to have one but power is controlled in software and therefore isn’t totally necessary.  

So anyway here is a pic of my very first practice burn, a simple Raster etch.  A Star Is Born.


Sky is the limit here folks.  I’m going to try to use this machine for cutting materials which the Ortur just isn’t powerful enough to do.  I did zip through some 3mm plywood with ease though but some appreciable burning.  An air assist and greater working knowledge of the cutter settings will straighten that situation up.

My Mini-Gerbil card will be here in a couple of days and then I’ll update my blog with that experience.  Lightburn really is WAY BETTER software than Inkscape/K40 Whisperer.  I am not knocking Inkscape and K40 Whisperer, oh no, I just like Lightburn a lot better.  There is a lot to be said about free and Open Source software.  If you’ve ever used Lightburn you know what I’m saying.


  • Air Assist
  • Mini-Gerbil
  • Maybe, maybe not install milliamp meter
  • Maybe upgrade the mirrors soon

I call this K40 laser setup a raging success.

I would like to add more point.  These things are not toys and can catch things on fire.  Get a decent extinguisher and keep it nearby.  I asked a fireman I know to recommend one and he pointed me towards this one from Kidde.  That is an Amazon link but they can be purchased locally in most places.   BE SAFE!



One thought on “K40 Laser – First 48 Hours

  1. Pingback: Laser Engraving Fundamental Skills - John's Tech Blog

Leave a Reply

Your email address will not be published. Required fields are marked *