Getting Ready to Modify K40 - Tips?

Hi all, brand new here!

I finally decided to take the plunge into the K40 world and am in the process of deciding what upgrades to do and how I am going to accomplish them. I have been spending lots of time researching the upgrades and while some things seem straightforward, other actions still make me scratch my head. Below I have included the K40 that I ordered as well as a “dream list” of things that I want to do to the machine. I haven’t received anything yet, but can’t wait to get started!

Here is the unit I ordered: 40W CO2 Laser Engraver - 8x12” Work Area - OMTech Laser

Here is the list of things that I would like to do:

  • Remove digital panel and convert to analog
  • Cohesion3D Board + Lightburn
  • Lightburn Camera
  • Remove stock exhaust and install blower at the end of the duct work
  • Water flow gauge and temp sensor
  • mA meter and potentiometer
  • Digital display of power in V for easy tracking of settings for different materials
  • Air assist (haven’t decided between 12v fan, compressor, or aquarium pump)
  • Add a couple of PC cooling fans in the compartment with the LPS for good air flow

I also want to add on/off switches on the panel for the following:

  • Air assist
  • Water pump
  • Exhaust
  • Laser engage
  • Red dot (I would like to choose when this is on rather than constantly being on as I assume it will ship)
  • LED lights (again, would like to be able to turn these on and off as desired)
  • On/Off for PC pans in the LPS compartment

Momentary switch for:

  • Laser test fire


My main questions at this point are:

  • How feasible is it to have master on/off switches for items like water pump, exhaust, air assist on the panel? I really would love to have the switches on the panel as opposed to turning them on/off from a power strip for example.

  • Is 1 additional power supply enough to power the accessories mentioned?

  • Is there anything on the stock LPS that would need to be changed/upgraded?


I am sure more questions will arise once I actually dig into this, but wanted to get ahead and continue my research while I wait.

I plan to follow some advice I saw on another thread and make a schematic of everything the way it is before I change anything to reference later if needed. I also plan to take plenty of photos for reference.

Thanks in advance for any and all tips or advice you may have!


In the K40 rebuild I’m doing, the air assist and exhaust are controlled via solid state relays with switches on the front panel.
I did this so I could keeps all mains voltages away from the front panel. Power switch is relocated to the rear, right of the cabinet. LED lights are also switched on the panel.
A flow sensor switch is wired in series with the laser enable switch on the front panel and later will add door interlocks, in the same circuit.
I’ve fitted a 24/12/5V supply (Meanwell RT85D) to power the steppers (24V), lights and SSR (12V) and Raspberry Pi (5V).

1 Like

Lots of good updates. One I didn’t see was to add a 24V5A power supply to power the Cohesion3D board so that the LPS is less likely to overheat and it provides more power to the stepper motors. You can use DC-DC step-down voltage regulators to give you 12V for LEDs or 5V for laser pointer.

The mA meter is a must and I would not power up the machine without something connected to show you the mA through the laser. Those digital displays have prematurely killed many laser tubes and some at even 40% were over driving the tubes.

So a mA meter, 10 turn 1K POT to adjust max laser voltage and the little 5V digital volt meter display will be very handy. Well, handy as in after 3 or so years you might notice your peek current is lower than it used to be and say 2.4V on the meter now needs to be 2.5V to get the same 18mA peek current. These tell you your tube status and also let you keep the peek power the same so when you pull up a design with 20mm/s and 55% power for cutting 3mm plywood it will make the same cuts even though the tube is aging.

This will direct you to which air assist compressor to get. hint ~1100GPH $45 on amazon

1 Like

All C3D boards purchased in the last 1-2 years come with a power brick included as part of the package.


While I appreciate your enthusiasm, I wouldn’t do anything until I worked with a stock K40 for a while and figured out its’ strengths and weaknesses…And quite truthfully, your biggest gains are going to be in upgraded optics and understanding the software. I have a comparatively barbaric k40 with homemade z table and air assist and it is still an incredibly capable little machine once you figure it out.

1 Like

At least the analog ammeter and (not listed above) interlocks belong on the “do before you fire the laser” list in my opinion, so I disagree with running it full stock initially.

Sounds like a good plan! I definitely still need to plan exactly where everything would go, interesting idea to keep mains voltage away from the front panel too.

I’ve read about that power supply. Nice that it has 5, 12, and 24V. That would probably be sufficient to run all the accessories and switches through yeah?

I forgot to add the interlocks to the list, but yes, I absolutely plan to add those right away. Safety first is my approach to getting into this.

1 Like

Would a 5, 12, and 24V supply replace the need for step down regulators in order to run the various things like red dot, lights, etc?

I appreciate the link for the air assist!! Looks like that air compressor you suggested will be a good choice.

The mirrors and lens upgrade are one of the items I also forgot to add to the list above, sounds like they will be a good choice.

I’m sure this will all take me a while to accomplish, so it’ll be pretty basic early on as I learn the machine. Though I do plan to take the necessary steps towards safety before firing it up.

1 Like

Definitely. Though step-down is cheap, and the current needs for 12V and 5V are low and @raykholo shipping a good PS with every c3d might change the calculus here. Buck converters are now “popcorn parts” to buy in bulk and use for whatever you need…

I also would advise getting the machine running with stock parts before making any changes. This is important if you want anything replaced by the seller who will want it to be a stock configuration.

Draw simple boxes in all 4 corners and in the middle on simple material at low powers. I often use card stock for simple tests. Your not looking for high power ability, just verifying the whole system works end to end.

Then add interlocks followed ENDLESS upgrades…


@donkjr would you recommend doing this test prior to adding the mA meter as well?

I am running from a Mac, so I know I will have to swap the board to even get the laser working with my computer. As far as I am aware that is a very simple plug and play swap so as long as other components work during the test I should be good to go as far as getting up and running?

IMO you can use the machine w/o the milliampmeter just to do a basic test. If you really want to see the current you can temporarily put a meter in series with the cathode.
The best approach is to get a machine baselined then add one change at a time if possible.

You can expect something going wrong with each change, but you can also count on us to help find it. :wink:

If you could find a PC that would help you get the entire tool chain working. If not then imo the c3d with lightburn is the next choice and closest to PnP.


K40 Whisperer works with the stock M2Nano board and it says it’ll run on Mac. I used it on Linux when I first got my K40. K40 Whisperer

1 Like

@donkjr I appreciate that! I can see how much everyone helps out here, which is why I decided to join. Looking forward to learning from you and everyone else!

1 Like

@dougl I saw that K40 whisperer can run on Mac, but it requires quite a bit of work to get it to work. Terminal commands, etc. I started to play around with that, but never had any luck getting it to work. I felt like the upgrade to a C3D was bound to happen at some point so I decided why not just jump right in from the get go!

1 Like

yes but the one benefit of getting it running is being able to validate the basic operation of your machine before you start doing things to it.

Have you ever tried booting your computer from a USB drive? Ubuntu Linux is free and can be put onto a USB drive and usually with full internet functionality so you can then install K40 Whisperer and try that just to validate your machine. Maybe even a virtual machine with Linux on it and the same.

Not just plug-n-play but lots of information on the internet on doing it and if you ever had an interest in the raspberry Pi’s, they are Linux based and you’d have a little more understanding of some things.

Without a display on the laser cutter to operate the machine without a computer there are hoops to jump through but it’s all about learning new things.

1 Like

Could someone please explain (or link) how the digital voltage display showing actual laser power is hooked up?

1 Like