Be aware that these are not professional machines and do not meet safety standards. OK for "at your own risk" hobby work, but not for a business. If somone was injured e.g. blinded at work the company would have no excuse and theier insurance company may not cover them either.

Robert G8RPI.

A bit of science: The effect of intense heat on marble is quite different from that with graphite. Marble (calcium carbonate) decomposes at red heat into quicklime (powder) and carbon dioxide. Turn off the laser heat and the process stops. Graphite, in the presence of air, burns away, and once hot enough it continues to burn without needing the laser heat. If there is no oxygen, in a vacuum, the graphite will get hot but nothing else happens until a very high temperature is reached. Remember that crucibles for melting brass etc are often made of graphite. But with a powerful laser in vacuo it should be possible to melt graphite. The power is needed because graphite is quite a good conductor of heat, so it might be better to the job in a draught of some non-reactive gas (argon, perhaps nitrogen?) to take the heat (and the molten carbon) away.
My reference says C melts around 3800 centigrade – the highest temperature in a comprehensive list.

This should not stop you trying, as my negligible experience in this area is likely to be as limited as some others, and it would be interesting and useful to find out more.

Regards, Tim

Edited By Tim Stevens on 19/08/2021 18:50:14

The windscale fire was burning graphite. Helped by them turning up the wick on the cooling fans in an attempt to blow it out. Only when a hero decided to direct a fire hose into the inferno did they put it out. Probably a matter of scale, I suspect a small piece would self extinguish

I think the guide vanes on V2 rockets were graphite but the hot gas didn't contain oxygen, so they did not burn away

Hi Nigel,
I've also used the ML10 system. It is low power <5mW and needed no special precautions other than not looking directly into the beam. And it's visible so you can avoid i and have blink reflex. That employer also built various instruments with higher, but still low, power visible lasers up to a couple hundred milliwatts. Those had to have fixed covers and interlocks. When working on them with covers off they had to be in a controlled area with trained operators and safety goggles.
For a muti-watt invisible laser, a stray reflection escaping a gap in a cover can cause permanent damage and you won't even see it.

A side story, at that job I used to do personal work on the premises ( how I miss the prototype machine shop with manual & CNC lathes and mills, surface grinder exc). I was working on flash tube driven Nd-Yad laser from a naval rangefinder. Iwas just working with the flash tube driver and had the cavity blocked and a blank on the output. Unknown to me the production managey wh was also the laser safety officer was in the factory and saw the flash of the tube and when I told him what it was he nearly had a fit! Made me have an eye exam so If I'd done any damage I could not say it was done at work later.
I asked if they were going to pay for an exam evertime I played with that or one of my other lasers (Ar-ion, CO2 etc) at home…… He didn't have an answer for that. I'm careful and have proper goggles for all my high power lasers (often costing me more than the lasers). Not burnt spotson my retinas.

Robert G8RPI.

Development cost's, precsion optical and mechanical components, lot's of electronics for starters. There is a big difference between making somthin that works as far as an semi-skilled user can tell and may not be reliable. and one that meets proper specifications and maintains performance during use and has to be supported. Also a reptutable supplier will use quality, properly approved safety components. A cheap hobby laser may have none. For example the laser blocking windows look like orange plastic but there are lots of plastics and lots of dyes. To ensure safety you have to use plastic that comes with compliance certification and the plastics maker has to have certification for their materials to support that. This may mean virgin polycarbonate and expensive dyes. A cheap hobby machine will use the cheapest orange plastic they can find and not bother about it's actual performance. This does not just apply to lasers I've seen cheap machine tools with brittle plastic (probably polystyrene) "guards" that broke if you tried to adjust them by holdng the edge. Proper ones are mde from polycarbonate ot thick acrylic.
Also important for relatively small quantity technical equipment is the cost of certification. To properly prove compliance for all the safety aspects costs a huge amount of money. This has to be covered by sale of a small number of machnes.

Robert G8RPI.

As noted earlier an Nd-YAG laser is preferred to cut / engrave graphite. This is 1.06nm (1064um) wavelength compared to 10.6nm for CO2.. These are both infra-red wavelengths.

Robert G8RPI.