The K40 Laser Cutter


A brief overview of the K40 Laser Cutter

The K40 laser cutter is a cheap, Chinese made 40 watt CO2 laser engraver and cutter. Typically, you will see them on places like ebay in a pale sky blue and light grey. They have some significant positives but a number of negatives as well:


  • Low cost
  • Easily upgradable
  • Accurate


  • The basic software supplied with the unit is awful
  • Software requires a dongle
  • Poor fume extraction
  • Default work area is too small
  • No air assist

And I am not going to mention safety as I have already 'laser’ed my thumb once.

I’ll will come back to the software as there is an easy fix for this one.Firstly lets address the hardware issues:

1. Default work area is too small:
This is the standard ‘out of the box’ setup for the workarea on a K40:

The large silver bordered hole in the bed is the clamp for the material you are working on. As you can see it is pretty small. The first thing I did was remove the clamp and put a piece of steel, cut to size, in the hole. This worked great and increased my bed. The next thing I did was cut the fume extractor back. This may seem mad when fume extraction is another issue but that issue is to do with the extraction fan, not the extractor tube in the unit. Finally I found a piece of clear vinyl tube on the forwards/backwards rail that limited the movement of the head at the front of the machine (no stop switches so you can over drive it). I removed about 25mm from this stop so I could get the laser cutter head as far forward as possible. This increased my available cutting area to 230mm x 340mm. Not a bad cutting area. My final modification the bed was to lower the whole bed by 12.5 mm and add some aluminium standoff. This improves the underside of the material as it is cut, a solid metal bed reflects the laser and adds burns to the underside of the material. So my cutting bed now looks like this (admittedly in need of a clean and yes the extractor was cut with my dremmel and needs cleaning up :face_with_raised_eyebrow:).

2. Poor fume extraction
The poor fume extraction is due to a huge, poor quality fan that doesn’t fit:

My next upgrade will be to replace this fan with a sealed plate on the back of the unit, that actually fits and then connect this via a tube to a higher quality extractor unit.

3. No Air Assist
Air assist is when you pump compressed air over the cutting point as the laser cuts. It helps in two areas:

  1. It stops the smoke hanging around a getting in the way of the laser - so you get better cuts and your optics need less cleaning.
  2. It reduces the risk of fire. If you cut plywood you will often see flames (which is scary) but with air assist no flames and a cleaner cut.

So I added Air Assist with a 3d printed nozzle and a piston compressor from an airbrush painting rig. There are lots of variants of air assist nozzles on thingiverse but I went with this one in the end: and it works very well on my setup. Just a length of silicon tube to connect it to the compressor.


So now we need to address the software.

Laser Cutter Software
The default supplied software with the laser cutter is terrible. It is clunky, not very accurate and requires you to have a dongle plugged in when you run the machine. Cutting is done by connecting your K40 to a PC via USB, so my surface was a pain to use as it only has one USB port, I used to have to hook up via a usb hub.

Thankfully, there is a true hero out there that can save us from Chinese software. Please give a big hand for Scorch Works and K40 Whisperer . K40 Whisperer takes a colour coded SVG file and lets you vector cut, raster engrave and vector engrave. Plus you can do it all without a dongle!!! Your vector cut lines are red, your vector engrave lines are blue and your raster engrave lines are black. Its that easy.

Scorch Works have even created a plugin for InkScape to allow you to export your designs in a zip file with each layer in a separate engraver file and a copy of the svg design.

It is truly bliss to work with, especially after the standard software so if you get a K40 head over to Scorch Works and grab a copy of K40 Whisperer - on top of all that it is free and they have done some tutorial videos!!! You can even engrave photos using raster engraving and their neat halftone/greyscale mode.


Very cool stuff here for sure. When I have the need I am going to strongly consider one. Right now I have to many CAD projects to finish before I add another device to play with.

Thank You for sharing this detailed info. It sure has helped me understand this quite a bit more. I am sure it will help others as well.


My pleasure and I will get a video done today and upload it.


Thank You Carl!!!

Very informative and well presented!!! I’m still on the sidelines for now … Venting is not a critical concern for me. I will not be using a laser cutting unit in my house. Now I am in California so I best not create too much SMOKE!!! Mostly kidding… :wink:


So here is a very poor quality, and bumbling video. It shows the k40 both engraving and cutting. The final part of the video shows a vector cut without air assist. You will see the flames.


I love it. Sweet Example on the Raster Engraving.


I just had to screenshot it and share it here. Thank you for showing how the machine works. And thanks for using the logo as an example.


And a slightly better look at the end result. I definitely had the power too high for the engrave, you can see it is around 1.5mm deep, deeper than I normally go for. What is worth noting that even when I was running the engrave over power we still got good detail, particularly around the cogs that make up the eyes.

Edit: they say great minds think alike lol


I noticed that, it caught my attention at the detail it was able to achieve.


One final example of a larger piece that was cut on the K40. This is my original test cut of the chassis for the Robotics Hobbyist Hexapod robot. It was cut in 3mm plywood. As you can see it has nice clean edges and the holes have cut very well. The slight damage on the arm in the lower right was due to me cutting at a slightly too low power rating, hence I didn’t cut all the way through on that arm and in my rush to free the piece, I chipped it. Not an issue as this was a test cut for me to see if my electronics would fit the chassis before I cut it in acrylic.


Absolutely fantastic job!!! Big thumbs up!!! :+1:t2: