Maker Hacks

Best K40 Laser Upgrades – Upgrading my Laser Engraver Part 3

Best K40 Laser Upgrades – Upgrading my Laser Engraver Part 3


I am on a mission to make my Chinese K40 Laser Engraver work like a much more expensive USA name-brand machine.

Update to Part 2 – Brain Boosting

Previously, I bought and installed a new mainboard of electronics, and a filter for the pungent smoke.

I am happy to say, while the filter still feels a let-down, the Smoothie board has been a fantastic success when combined with the LightBurn software. Read about the purchase in the previous article.

Grey-Scale Control Using the Smoothie Board and LightBurn

Optics Upgrade

While the laser was meant to have been unused, I did notice some wear, either from actual use, or just as likely, testing. Also, from what I could tell, the optics were not the best.

I bought a lot of moist cleaning wipes, but really I needed new mirrors and
a lens.

Cleaning is essential to get the best out of a 40w laser

I went ahead and bought some not-top-of-the-line-but-good ones.

Right away I seemed to get more power and cleaner lines out of the machine.

Bed Removal

The K40 comes with a metal bed that seems like a good idea, but in fact it makes focusing the laser more difficult, because your z height is not adjustable, and obviously focus is vital if you are going to get clean, strong cuts.

Bed begone!

Once I had removed the bed, I could cut a focus-tool and stack material under the
workpiece to allow me to position the piece 50.8mm from the base of the lens. This is the sweet-spot for “top focus” (ie. engraves), then you compensate appropriately for deeper cuts.

Air Assist

To mitigate the charring and smoke, which is not just an issue on the workpiece, but also damages the lens, I bought an air-assist nozzle. Now, some experts say you don’t want to do it this way – the air should blow horizontally – but for now it will be an improvement on no air.

Another speed bump here. My airbrush compressor would not switch on, regardless of how I set the pressure dial, plus the connections were of the wrong type.

Fortunately, I have an air pump that runs off D batteries for inflating, well, inflatables. Things like camp beds and floaties.


  • Inline Bilge Pump
  • Requires 12v into +/-
  • Venting far, far away

As mentioned, the air filter didn’t really filter anything. For now I am using an inline pump (12v) and piping the smoke out of the garage using an extension tube. It’s better, but I am hoping new pumps/fans I have ordered to test will do a better job.

Clean power with UPS

I was getting some strange chatter in comms between the Dell laptop and the laser. The USB cable I bought along with the Smoothie board was supposedly good quality, so assuming it was power fluctuations, I bought a new UPS for the office and placed my old one out in the garage.

UPS is probably a good idea for long jobs anyways

Seemed to help a lot – especially when I blew power using the shop vac AND 3d printing AND running the CNC AND the laser.

What next?

Right now, in total, I have probably spent around $1,300 CAD, including the laser itself. That’s still giving me a lot of room to upgrade, considering even the most basic Glowforge is, what, $2,500 USD before shipping? And a Full Spectrum or Trotech would be much more than that.

The smoke extraction and ventilation
is still not great. I need to add those new
fans, and seal up the laser case. It’s bad enough breathing the glue from plywood, without adding acrylic fumes and such.

Next, cooling. These laser tubes operate best below 18c and even before firing the laser the ambient temperature out in the garage has been hitting 35c.

The bucket of distilled water approach to cooling was not going to work for me.

Yeah, lots of people swear by it, and it is the cheap solution, but I could already tell for my situation it wasn’t ideal.

I ordered a CW-5200 industrial chiller. It’s an actual chiller, as it refrigerates rather than just circulates water. So far after the laser, it is my biggest purchase for this setup. The more reasonably priced 3000 is just a commercial version of the bucket approach.

It’s sat in the house waiting for me to feel fit and strong right now, I will report back with another update.

Expensive, but probably cheaper long-term than lots of laser tubes



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