K40 style CO2 laser cutter mods.

[JMS1972]

Here's a few things I've done to my CO2 laser. These are sold on eBay and Amazon for around £300. The generic name is K40 and a quick Google search will pull up loads of web sites dedicated to modding these.

They are sold as 40Watt lasers but the length (which affects power) is too short so realistically they are 30watts.

Max usable size is A4 but only if you move the limit switch nearer the back.

I've added air assist which performs two functions it increases cutting power (think blowing on embers to get a fire going) and protects the lens from smoke.

3D printed nozzle. Air bleeds into the central cone as well as to tip of nozzle.

Runs off a beefy aquarium pump.

The best beam focus was a few mm off the bed so I use nuts to raise work up and also as end stops round the edges.

The brown tar is a feature of cutting MDF and plywood. Hence the need to improve extraction.

The extraction port was filled with some packing foam to only extract from above the bed (work is raised up so smokes on underside). The standard fan is backed up with an axial 4" high flow extractor venting outside as the smoke is surprisingly very toxic

 

[JMS1972]

The standard power control is digital

the problem being the numbers don't mean anything so I added a milliamperes meter in series with the HV supply to the laser tube. Careful doing this as it's about 15kV (yes kilo-volts)

Laser power is proportional to current so this is an accurate way of measurement.

 

[JMS1972]

The laser works better at lower temperatures so water is run through the laser tube continuously I have a big bucket of water with the supplied submersible pump. I monitor the temperature with a cheap probe.

It's a good idea to have some sort of flow monitoring I've not fitted mine yet.

I've made a little heat exchanger for the water with fans etc but haven't plumbed it in yet. Works like the water cooled TIG torch coolers.

 

[My Old Landy]

That's a great write up, thanks for showing your setup

 

[Red'n'Black]

How much work are they to set up and keep all the optics aligned?

I tried to interest work in getting one of these, we do a lot of prototyping and test jigs in perspex and polycarbonate. But they didn't trust the 'eye safety' aspects of a £300 ebay machine, and a UK built one with all the approval certs etc would be 10X the price.

 

[Other Daniel]

Fascinating
Keep it coming, please.

 

[JMS1972]

How much work are they to set up and keep all the optics aligned?

I tried to interest work in getting one of these, we do a lot of prototyping and test jigs in perspex and polycarbonate. But they didn't trust the 'eye safety' aspects of a £300 ebay machine, and a UK built one with all the approval certs etc would be 10X the price.

Initial setup was fiddly I spent a few frustrating hours getting the three mirrors aligned. Once setup I haven't had to touch it but mine only gets occasional use.

Most people add an interlock switch on the lid to prevent the laser firing when open. I burnt my hoodie sleeve only yesterday so should probably do that too before I slice a finger off....

For commercial use I'd suggest looking at the 60 watt laser cutters which are a few grand and built to a much higher standard.

 

[JMS1972]

The real beauty of these is the design flow is really simple (for CAD).

I draw designs using Inkscape (free Vector graphics drawing program). You use three colours to define the shapes

Pure Red - Cut
Pure Blue - Vector engrave
Pure black - Vector engrave.

With a finished drawing I size the "paper" to fit the design.

You save the design as a SVG format file and load it into a great free program called K40 Whisperer.

This talks to the laser cutter via USB and allows you to control things like cutting speed and starting point. It converts the design into commands the cutter understands (G-Code maybe?)

These two programs are free and much better than the junk supplied with the cutters. (Hacked commercial software).

 

[Red'n'Black]

Initial setup was fiddly I spent a few frustrating hours getting the three mirrors aligned. Once setup I haven't had to touch it but mine only gets occasional use.

Most people add an interlock switch on the lid to prevent the laser firing when open. I burnt my hoodie sleeve only yesterday so should probably do that too before I slice a finger off....

For commercial use I'd suggest looking at the 60 watt laser cutters which are a few grand and built to a much higher standard.

That would scare the bejesus out of me, especially as the beam is invisible.

I appreciate the beam diverges once past the focus point but isn't the eye-safe limit something like 5 mW? Looks like lots of shiny reflective surfaces in there. Do those safety glasses give much protection at that sort of power level?

 

[JMS1972]

A few things I've made for the workshop.

Quick and dirty collet stand for Pultra lathe.

Tool rack for nut spinners.

Box for collets. There is a website that will design the finger jointed box for you I just added text and holes.

"MakerCase - Easy Laser Cut Case Design" https://en.makercase.com#/

 

[JMS1972]

That would scare the bejesus out of me, especially as the beam is invisible.

I appreciate the beam diverges once past the focus point but isn't the eye-safe limit something like 5 mW? Looks like lots of shiny reflective surfaces in there. Do those safety glasses give much protection at that sort of power level?

I run the laser with the lid shut normally. I also always wear decent quality laser goggles with the correct wavelength filtering when faffing about.

You have to be a bit careful with assumptions on what is reflective etc as its a different wavelength to visible light.

 

[Barking Mat]

Interesting, thanks.

Good write up.

 

[pcwizme]

I have a k40 sat on my self doing nothing, (really should get it sold) that I put a cohesion 3d board in that means you can use light burn. But I upgraded to a 50w (sometimes wrongly called a k50), thats now sat doing nothing cos I upgraded to a 100w omtech.


k40's are great except for the electrics can be slightly dodgy, and the supplied extractor fan is basically dangerous.

 

[ukracer]

Rather like a 3D printer. Needs work to make it useful
Does it actually cut the wood or just engrave it?

It would be nice if @MattH could show his at work one day.

 

[pcwizme]

Rather like a 3D printer. Needs work to make it useful
Does it actually cut the wood or just engrave it?

It would be nice if @MattH could show his at work one day.

The do cut wood but not massivly fast but faster and more accurate than a hand saw @MattH has some lovely lasers judging by the photos he has posted

 

[JMS1972]

Rather like a 3D printer. Needs work to make it useful
Does it actually cut the wood or just engrave it?

This is very much the bottom of the cost / quality curve

Easily cuts 3mm at half power. It's a lot better than the unguarded 3mW blue laser engraving machines

It would be nice if @MattH could show his at work one day.

 

[JMS1972]

I have a k40 sat on my self doing nothing, (really should get it sold) that I put a cohesion 3d board in that means you can use light burn. But I upgraded to a 50w (sometimes wrongly called a k50), thats now sat doing nothing cos I upgraded to a 100w omtech.


k40's are great except for the electrics can be slightly dodgy, and the supplied extractor fan is basically dangerous.

Interesting is the K50 the much bigger machine with the variable height bed? Or did you just put in a bigger tube?

 

[pcwizme]

Interesting is the K50 the much bigger machine with the variable height bed? Or did you just put in a bigger tube?

its a 300x500 bed, with an adjustable bed height, a pass through. and a "50w" tube, (although realistically its a 45w tube really )

 

[JMS1972]

its a 300x500 bed, with an adjustable bed height, a pass through. and a "50w" tube, (although realistically its a 45w tube really )

Ah yes much more serious bit of kit. Couldn't really justify the extra spends on one of those really the K40 is used for the occasional workshop job and some hobby stuff

 

[pcwizme]

Ah yes much more serious bit of kit. Couldn't really justify the extra spends on one of those really the K40 is used for the occasional workshop job and some hobby stuff

Thats the other one I am getting ready to sell... as the newer 100w is the one that does 100% of what I do now, cuts 9mm ply with ease.... the 100w has 700x500 adjustable bed