K40 Chinese laser

[Colin G3YHV]

Hi all !  I wonder if any other members have a K40 laser engraver ?
Been playing with it for a week now and having great fun.
Made a few important mods to it -  like a switch on the lid so you cannot laser yourself.
Replaced the chinese mainboard with a much better one (Mini gerbil)
and a flow meter on the water supply -  ( feeding a pic )
Colin

[top204]

I had one until I had to sell it a couple of years ago to pay a household bill. :-(

It was a good unit and I did some modifications to it to make sure the gas suction was a lot better, and that the nozzle would supply more air pressure to the item being cut/engraved. I once placed a cylinder of nitrogen as the flow to neutralize combusion somewhat, and it worked extremely well with plywood. I also increased the oxygen content of the flow for items that needed a quick burn at a higher rate, or steel that needed a strong burn for engraving.

I placed a seal on the top window hatch, so inside it, it was an enclosed space, so the pressure of the feed and the suction flow made it a very clean, pressurised, atmosphere, which made a huge difference to the burn quality.

I also changed the control board so I could feed it with standard G-Code instead of all that DXF, SVG and Coral draw nonsense. :-) I was going to make the laser strength controllable from the G-Code, as the Z axis parameter, but I had to sell it before I could do that. :-(

Make sure you lubricate the X and Y belts and bearings with a silicon based lub, and check them regularly for slackness, otherwise, you will get wobble in the tracks it cuts, or no true 90 degree turns or true circles. Remember, it is Chinese, so "quality" of the machinery used in it doesn't exist, so it has to be regularly checked. LOL Don't use too high a current for the laser, otherwise, the cheap mirrors used in it will burn in a short period of time. I found that out myself and had to buy a set of better quality mirrors, and they also made a big difference in the quality of the burn, and allowed the focus of the beam to be improved quite a lot. I still remember when I was aligning the mirrors, I forgot the invisible laser beam and burned my knuckle when my finger went in front of the mirrors with the laser on. :-) It hurt like hell for a few days. LOL

On the internet, you get all of this rubbish about using distilled water etc for the laser tube cooling, but as long as you live in a place that has a softer water, the standard tap water does just the same job. But filtered water will do in areas that have harder water. I placed some anti-freeze in the water and some anti-mould liquid in it, just to keep the water a bit longer before it had to be replaced. Make sure there is not a large air bubble in the tube occasionally, because they can, over time, cause a hot spot on the glass and fracture it, but I found the anti-freeze made the water softer and allowed it to flow better without too many bubbles in the tube. Suction of the water through the laser tube is better than blowing the water through it, and it causes fewer bubbles in the tube because it is not blowing pressure into it. It actually pulls pressure from the tube and thus does not tend to form large air spaces.

[Colin G3YHV]

Thanks Les , thats all very useful info.
My replacement mainboard also supports variable power from the laser
And the software I am running called LIGHTBURN is brilliant, so I have one software package
that does design to burn in one go ( unlike the cnc machine).  I have also boosted the airflow
and it goes out through a hole I drilled in a window. I am about to add the air assist to the laser
to help blow away the fumes and ashes. I sprayed a piece of FR4 board with etch primer -  and laser off
some tracks using isolation routing and was surprised how good it looks. finer than I could
manage with an engraving bit and no leveling problems, cutting and engraving acrylic
is fantastic.
Colin