Vacuum Chamber Construction

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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

After a bit of a school enforced break, I've finally managed to find some time over the summer holidays to return to the machining of my vacuum chamber. Using a carbide spot drill, a pilot hole was drilled and then subsequently enlarged to 3/8 size with a number of drill bits. I now plan on using a step drill to enlarge the whole to close to its final size and finally a boring head to take the hole to the precise diameter. The second hole visible in the photos below is from an earlier machining attempt that didn't work out.
image1.JPG
image2.JPG
I do however have a question about workholding. I'm using 4 toe clamps on a tilting table to hold my workpiece in place. The hemisphere seems to come loose rather regularly with the setup. After monkeying around with it for a bit I was able to find a seemingly stable solution that held the workpiece securely, but I wanted to know if there was a better way to go about holding the hemisphere. Or if I'm simply setting up the toe clamps in a way that doesn't use them effectively.
image3.JPG
John Futter
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Re: Vacuum Chamber Construction

Post by John Futter »

Toe clamps directly to mill slide bed
t bolt through the hole in the top with machined aluminium disc to fit hole now held top and bottom you will need to offset mill head to correct angle to bore hole.

enjoy
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Thanks for your suggestion John, I've cobbled together a better workholding solution as a result. A t-bolt in the middle of the hemisphere is connected to a long bolt, which has a couple washers on the end. I plan on adding a dab of superglue between the washers to hold them together as a unit and make assembly and disassembly of the work piece a little bit less finicky.
image1.JPG
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Before returning to school I was able to complete the first angled port on one of my hemispheres. Now that I have the series of operations figured out I anticipate that I'll be able to complete the remaining ports much more quickly. I'll likely be able to get to it over winter break or failing that early spring once school breaks for the summer. A cheap step drill from china performed very well to rough out most of the hole and a boring bar was used to take it to final dimensions. Initially the boring bar was too long and excessive chatter resulted, but I switched to a much shorter tool and chatter was greatly reduced and surface finish improved drastically.
image1(1).JPG
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Richard Hull
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Re: Vacuum Chamber Construction

Post by Richard Hull »

Great work! You are using the exact same tilt table I use on my milling machine to do such work.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

After a school enforced break, I've managed to pass all my classes for the semester and have found some time to work a bit more on the machining of the hemispheres. I've successfully completed a second angled port on one hemisphere. What took me most of summer to finish with interruptions and mistakes in machining process took me the better part of an hour this time. I anticipate I'll be able to finish the remaining ports within the next few weeks. Then I can move on to learning to how to TIG weld!
hemisphere2.JPG
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Machining has been completed on one hemisphere and the angled ports have been started on the second hemisphere.
small.JPG
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Richard Hull
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Re: Vacuum Chamber Construction

Post by Richard Hull »

Gee! That is some aggressive machining with ports-a-plenty.

I trust once the flanges that hold the system halves together are welded, that you have clearances for the ports, which I assume are CF stubs.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Yes, I'm copying Andrew Seltzmann's design that he's posted on his website. I doubt my machining tolerances are as good as his though, I've been using an edge finder and tilting table instead of the precision rod and indexing head setup he used. I've got a single half nipple CF port you can see partially hidden in the photo. I've been using it to test fit as I machined out the port holes. I've checked the port against the flanges which I also have and all fit quite well.

I figured that 10 ports would allow for some flexibility, it seemed a waste to build a vacuum chamber and then not be able to reconfigure it if in the future I wanted to monkey around with sputtering or semiconductors or some other project requiring high vaccuum.

I have the following general plan mapped out for the fusor chamber.

2 On Axis Ports:
TurboPump Connector
High Voltage Feedthrough

8 Off-Axis Angle Ports:
Pressure Sensor
ViewPort
Hydrogen Ion Gun
Boron Ion Gun
Quadrupole Mass Filter - based on Rapp Instruments design posted here
3 spare ports

I view this project as a rather long term thing for educating myself and gaining useful skills, I'm not planning on attempting Deuterium based fusion, many people have succeeded at that on this forum and I would like to try something new. If at the end of this none of my ideas work out I'll merely have gained a bunch of useful skills, which I view as a pretty good deal. My plan for the next year or so is to complete the chamber, power supply and high voltage feedthrough, and pump system. This will allow me to generate a plasma, and then I can begin working on the more advanced components. While I have most of the individual components all require some work, for example I have a small turbopump however I have to design a controller for it as I don't have the funds to purchase one new.
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Richard Hull
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Re: Vacuum Chamber Construction

Post by Richard Hull »

You are doing it the right way and the best way. Do a little and learn a lot. Do a little more, read and practice the skills. You will succeed in fusing even if your ideas don't pan out. As you note, it is a win for you that will give you skills for a lifetime of future endeavors. Each skill is another tool... a tool that you can't go to the store and buy. The "hands-on imperative" is ingrained into all doers.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

I've now completed machining of the ports for the vacuum chamber. Up next is an order to lds vacuum for the remaining parts I need and some practice welding.
image1.jpeg
ian_krase
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Re: Vacuum Chamber Construction

Post by ian_krase »

That is a lot of holes.
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Richard Hull
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Re: Vacuum Chamber Construction

Post by Richard Hull »

I mentioned that before above....An awfully hole filled chamber. Lots of CF stubs and lots of blank offs unless you are shooting for ion guns aplenty. At least he won't be at a loss for hassle free "add ons", if needed, in future.

On page two Nicolas gives a full, optimistic, listing of what is planned for each port. Until they are all in place, that means blank offs during early work.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
ian_krase
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Re: Vacuum Chamber Construction

Post by ian_krase »

In the excellent but extremely grognardy and complicated Kerbal Space Program mod KSP Interstellar, we see this fusion reactor, which appears to be a fusor-type reactor with ion guns.

Image

This makes me think of it.
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

While I source the final vacuum components for my chamber I figured I could work a bit on the pressure sensor. I've got a vacuum thermocouple gauge, and a spare Tiva C series board lying around. I figured I would use one to monitor the other, I've been planning on picking up Forth for awhile and this seemed like a good project to start with. Mecrisp is a publicly available version that supports my board so I'm working on getting a connection made to the board.
image1(1).jpeg
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

This is an end of summer update. My purchase from LDS vacuum arrived at the end of July, and I now have the necessary hardware to complete the vacuum chamber. While I had intended to complete the welding by the end of August, getting setup for TIG welding has taken longer than anticipated (as always seems to be the case). The local makerspace does not have a TIG welder, and I've had to turn to other means. I've purchased a small TIG machine on Amazon from HitBox, and while it turns on, sourcing all the other components, such as TIG electrodes, a small bottle of Argon gas, a regulator, 220V dryer plug adapter, has been an education in and of itself. Its taken me the whole month of August to obtain all the bits, sharpen the electrodes, find a bottle supplier, get the bottle filled etc... I'm returning to school this Tuesday and will have to pack away the hardware for the summer. This means I'll likely return to work on my simulation when time allows, and hopefully at Christmas I'll be able to find some time to work on welding of the chamber. I'll be on a co-op term from January to April so ideally I'll be able to complete the chamber after work hours during the winter.
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Re: Vacuum Chamber Construction

Post by ian_krase »

Where are you doing your welding? Do you own a house with a garage, or do it somewhere else, or what?
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

I don't own a house unfortunately, I had planned on appropriating the dryer plugin in my parent's laundry room and running an extension cable outside through a window so I didn't have to worry about the fumes/gas. The welding machine I've bought is quite small and portable so it shouldn't cause too much of an issue. If I'm welding in the winter I'll look at heading to the local makerspace with my setup as I believe they're wired for 220v and have a large ventilated bay.
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Just a short update, I've managed to get the mecrisp-stellaris version of forth loaded onto my board and am now monkeying around with the language in my spare time!
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

After completing another semester of school in Victoria, I'm now on an 8 month co-op in Edmonton. I've joined the local makerspace and setup my TIG welder for the first time tonight. I'm currently practicing on some scraps of steel I've got lying around, and boy do I need it! I'll probably keep practicing until I feel comfortable and then go ahead and start welding the components of my vacuum chamber. At the moment I've got a lot to learn, and I'm just trying to get better at controlling the puddle.
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Richard Hull
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Re: Vacuum Chamber Construction

Post by Richard Hull »

Keep practicing, you will get there. Getting the current set right and your speed during the weld is critical. The puddling, if done well, will sort of set the speed of movement automatically as you get familiar with it.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Vacuum Chamber Construction

Post by John Futter »

Nic
You need some scraps of stainless about the same thickness as you are going to weld in anger
stainless is very much different from steel to weld --infact I find stainless much easier --but I was taught how to weld on Stainless

good Luck
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Thanks for the tip John, I found a metal supermarket up here in Edmonton and picked up some 304 SS offcuts of about the same thickness as my chamber. Last night I was able to get setup and make some passes, the photo below shows some of my handiwork. I started on the right just passing the electrode and controlling the puddle, then I added in the filler rod. Wasn't great to start but the welds started to improve. At that point I'd mucked up my electrode and had to regrind which accounts for the mess after a few decent lines. When I went to restart the welding mask I was using started to go on the fritz, it wasn't auto-darkening properly. I'd read some decent reviews online that I thought justified me saving a bit of money on some safety gear from China. Rather than try and fix it I think I'm just going to write off the cost since I bought the cheapest I could find and spend a bit of money on a half decent one.
IMG_0918[1].JPG
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Re: Vacuum Chamber Construction

Post by Rich Feldman »

I can attest that sunburn is a risk if you skip the gloves and long-sleeve shirt, buttoned up at least as far as the bottom of welder's mask.

Even TIG welding can occasionally pop & launch a shower of sparks,
actually incandescent droplets of steel which you don't want to fall into your shoe or pocket.
All models are wrong; some models are useful. -- George Box
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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause »

I've continued to practice my welding, and its slowly improving. A lot of the work still looks pretty ugly, but I did my first joint last night and I can reliably put down an ok line on a flat piece of steel. I've got to monkey with a bunch of settings around my TIG torch, but the fabrication series on youtube has been a big help and has answered a lot of questions I've had. I've got to grab a bit more Argon gas as I've only got a small tank, but mostly I think I just need some more time in the saddle.
IMG_0933[1].JPG
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