In my last post about stays, I mentioned that I have started working on a caraco... Well, since then not much has happened - the mock is still sleeveless and I am procrastinating a lot. I even figured out why. I hate the stays I made so much that I can't imagine putting them on to fit sleeves on the jacket. I have decided to stop working on the jacket for now and make another pair of stays that I will hate less and it definitely has to be front-lacing! No way I ever make back-lacing stays again, not until I hire a maid. That's the sewing plans for the next 6 months or so. But since the laser project has intervened, I am not sure about the estimate for the stays and the jacket. Anyway, to the laser!

First of all - why??? One can buy a CO2 laser [tube] on everyone's favourite eBay/AliExpress etc for what I think is a very reasonable price. I don't own one myself, so I can't say anything about their quality and longevity but apparently, they work fine. My laser is far from that, I am somewhere halfway in the building process and the money I have already spent on it is likely more than 60W laser from AliExpress. I am scared to tally the price because it will make me question my sanity :-)

Most of the expenses are there because I am starting from scratch. I don't have any kind of laboratory equipped with even basic tools. Such as a vacuum pump, a rather basic tool :-) OK, before this project I had a couple of woodworking tools but that's it. My biggest investment up to now is the aforementioned vacuum pump. During the project, I also have decided to buy a 3D printer. The beast helps a lot to save time. Instead of me sweating with a coping saw, I now comfortably spend my time in FreeCAD and offload manufacturing of parts to the printer.

The project will hit one year mark in Feb 2020 and I am afraid unless it fails before that date, it might not be ready till then. I still need to pump more money into it. The vacuum part of the project is ready but that's 1/3 of the project. I don't have anything for the electrical part - a neon sign transformer and a variable transformer aka variac. And for the gas supply - CO2, obviously, but also N and He. I have a very vague idea of how I am going to get them, apparently where I live (Prague/CZ) laser gas mixes are not available for individual purchase. So, either I'll have to get 3 cylinders, 3 pressure regulators, figure out mixing... or just resort to a typical home laser scenario with my own breath as a source of CO2 :-) Since this first laser/prototype is unlikely to have a useful level of power output, I will definitely want to save on an expensive gas supply.

It seems instead of talking about why I want to build a laser I succumbed to whining again. Let's return back to the why question. Let me show you a book I had when I was a kid.

It is in Russian and the title page says Warsaw, 1975. The book has about 600 pages and they are full of electronics projects ranging from some flashing lights and other noisemakers to robots and yes, a laser based on a ruby crystal.

As you can see there is zero Arduinos, RPIs or MOSFETs involved :-) Even when I say robots, for this book it means a couple of transistors, relays and photosensors at best. While this is hardly impressive for the year 2019 it is refreshing to see what can be achieved with just a couple of transistors.

For 12 years old me, most of the book was far beyond me due to my age and availability of tools and supplies. So, to answer the why question, simply because it is the time! I always wanted to do technical projects but something would always stop me, from financial situation to personal problems that affected me throughout many years of my life. Finally, I am happy to be in the part of my life where I can enjoy building things without thinking about what I am going to live on in 10 years. Alas, not because I am suddenly rich, but because I don't care :-)

This is getting long, I am going to call this post a sad introduction to the project and later I'll cover technical bits and the decisions I make on the project, to document them for my future laser projects. For now, there is a couple of photos covering the first six months of the project.

I should mention that no, it doesn't take that much effort. Most of the time the project was/is on hold while I figure out its feasibility, i.e. where would I get ZnSe output coupler??? I still don't know if the one I got is any good, unfortunately, I'll know only at the very end... Then I would spend time saving up for the vacuum pump or collecting all necessary brass fittings. It turned out that no shops around me have anything smaller than 10-12mm diameter fittings, so again shopping online, waiting for deliveries or wasting money on local but still remote shops where postage is more expensive than a tiny part I need.

My second attempt at an adjustable mirror holder. I made it resemble the design of the real thing, but the plastic was not rigid enough, it was obvious that mirror adjustment will turn into one big hell. 
New rigid mirror holders and the current state of the project at the time of writing. The tube is sealed, [almost] doesn't leak and the needle valves for the pump and gas mix are there.

If you are not quite into lasers, the retro-futuristic hose coils are to prevent the current from the tube leaking into gas/vacuum system. That would be extremely dangerous given that a neon transformer I plan to use is 15KV/35mA. In other words, the hose length has to be longer than the tube length, to make sure the current stays in the tube and doesn't make a detour on needle valves and further to gas container/vacuum pump.

My seal making kit.

I decided not to go for the usual "JB Weld the crap out of it" way of sealing the tube, at least for now. Instead, I design and print custom moulds that I use for both tube ends and for mirror "socks" to seal them on flanges, prevent scratching and for later adjustment. I don't have a proper vacuum gauge yet. All I can say for now is that it doesn't leak like crazy but I will have to make another pass on one of the tube seals, there is still room for improvement. Acetoxy silicone is not the best thing to put in a mould, it needs humidity to cure, curing more than a 1-2mm thickness in a mould is problematic. I use WD40 as a release agent that I mist with water and pack moulds with wax carving tools, they are indispensable to make sure silicone gets into every nook.

One of the custom seals, fixed in place with teflon tape for now.

A somewhat strange form is because I use a Liebig condenser for the tube, one of its ends is flared and not easy to seal well. This one took a day to half-cure, I was able to extract it from its mould and let it finish curing. Loctite SI 5940 I use is very soft, so striation from 3D printing doesn't affect its performance.