Getting this K40 up and running

Greetings! New here, first post.

A few years back (in November, actually) I was gifted a K40 on Facebook Marketplace; guy had upgraded to an Epilog and was feeling generous.

Due to living situation at the time (3rd floor walk-up apartment, community garage, etc.) I couldn’t do anything with it so it sat in storage. Fast-forward to June 2022 when I moved to a rental house with a converted garage to workshop (yay me). SO, I’ve finally gotten off my duff and started working on this thing again. Built a cart for it to sit on so I can move it around the shop easily.
I’m going to be attempting to finally start a fab shop in Q1 of '24 (CNC machine, etc) so I want to see how much use I can get out of this before I have to replace it.

• Unknown hours on the tube but I suspect there’s plenty of life left.
• Needs an interior light.
• Needs cooling system.
• Needs air assist pump; tubing and nozzle are there.
• Has 6442S-B(EC) controller that needs a firmware upgrade.
• Has roller; not sure which orientation it should be in when in use. (The frame of it is also slightly tweaked and it doesn’t sit exactly flat.)
• Has 6" exhaust port. Can I use a 6" to 4" reducer, with an in-line fan?

I’ve already determined that it’s best I invest in an actual chiller and not rely on any other option. Should I use coolant as well?
I’ll also need whatever tool/method is used to measure the head-to-material distance.

Bottom line: I’m looking for whatever advice you kind folk have that’ll make this a shorter setup/re-learning curve (I worked with an Epilog back in '09 when I was employed at a local makerspace, so it’s not totally new to me…just out of practice)

Thanks in advance!

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Doubly ahead of the curve having experience and asking for advice before lighting a spark! :tada: :grin:

It’s worth taking a look through the K40 Intro at the top of the page — it will answer some questions, I think. Like coolant: distilled or deionized water with algaecide only. Also suggested air assist pumps.

Roller usually used as alternative Y axis so aligned with X axis typically.

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Unless there is a compelling reason, I’d suggest you do not upgrade the firmware…

Are you using RDWorks?


That’s a 500x300mm (~20x12") “50W” machine with Ruida controller. It’s dramatically better than a K40.

Check if the distance from the tip of the nozzle to the worktable is the same in all four corners.

Inspect and clean the optics. Order some new ones either way. It’s good to have spares at hand.

The head isn’t that great, but it’s usable.

The controller logs the on time, processing time, laser on time, and how far each axis has traveled. You can read that info with RDWorks (free) or LightBurn ($120). You can use either software to drive the machine.

Also take a look at the label on the tube. There should be a manufacturing date on it.

The rotary which used to be bundled with these machines is a very basic “hot dog” rotary which only works with cylindrical objects. Put two rubber bands on the item to prevent it from slipping on the knurled rollers.

The machine has to be turned off when you unplug the Y motor and plug the rotary in. The homing routine can be aborted by pressing Esc.

I’d remove the built-in axial exhaust fan. I’d use a 6" hose and a 6" mixed-flow inline fan close to the exit. A 4" circle only has ~44% of the area of a 6" one. The geometry of a reducer also adds quite a lot of resistance. Avoid a reduction in diameter if possible.

The distance from the tip of the nozzle to the focal point is probably around 10mm. You can determine it with a ramp test. Once you know the distance, you can make a focus spacer or step gauge.

I recommend to install an analog 30mA ammeter if the previous owner didn’t already do that.


When I first bought my K40 laser, I asked the same question as I wanted a consistent cooling solution which gave me maximum cutting session time with minimum hassle, I did briefly consider purchasing a professional chiller but I could not justify the cost at twice what I paid for my second-hand K40 and I did post my DIY solution on this site. This is based on placing my water reservoir including 2 water radiators to maximise heat interchange inside a second-hand desktop freezer which provides the cooling. My rather large pump providing a level of heating back into the water which stops it freezing and a water thermostat switches the freezer on and off. I also incorporated an auto switch-off valve if the flow were to stop. The other understanding I have is that the temperature should lie between the tight limits of between 18 to 22C to maximise tube life which it does. The solution works surprisingly well and consistently gives me long cutting sessions at a little over £100 investment.