Liquid Nitrogen... for freezing... anyone have any thoughts?

[Wis Bang]

I attended a training session for drivers at Liquid Carbonic. They used O2 but the one trainer walked out into the plant with a cheap plastic thermos bottle to get the O2 to freeze the rose and shatter it on the floor. Personally I don't know if it will help the op.

I rode along on an N2 delivery to the place that made the hamburgers for burger king. This machine took the ground beef and plopped burgers on a stainless steel conveyor tunnel and hamburger hockey pucks plopped off the conveyor into a plastic bag inside a box. The N2 eliminated the paper sheets between the individual burgers, as well as the labor to insert them and no chance of some not freezing thoroughly in a conventional freezer.

All forms of Cyro transport rely on a vacuum between the inner and outer shells. We were told to mention any trailer with frost as that was a sign the vacuum was failing. Con-Edison has underground transmission lines, sealed with lead and filled with the same cooling oil as a transformer. we would bring a trailer to spot on the street in the city and they would hook it up to freeze the oil to open the lines for repairs. We would bring a trailer load every day and pump it into the spotted trailer until they were finished and the trailer with the worst vacuum was the one spotted. They needed the continuous flow of LN2 to keep the oil frozen...it all went into the atmosphere.

Grab a stainless Stanley thermos at Wal-Mart and search out some with a bottle or bulk tank and get a sample, take it home and freeze a test piece of foam and try to mill some. If you used hand tools, you could even do the test with LO2 [-294F VRS -310 for N2] if that's easier to find. O2 supports combustion but does not burn on it's own. The trainer described it saying if you entered a room that was 100% O2 with a lit cigarette, it would immediately burn down to the end no explosion. Hospitals have a concrete pad so the hose is not laying on asphalt and Liquid O2 and oil DOES explode. The surgeon in a rush always parked on the pad and them Mercedes DO leak oil the janitorial staff used to cuss when they had to clean it.

Please re-read the warnings above about the propensity for it to boil off and the potential hazard for oxygen deprivation.

After the frozen rose the trainers asked if we knew why the sky was blue the he poured some into a beaker and once the vapor cloud allowed the bottom to stay cold enough you saw the liquid was sky blue.

 

[PILOON]

Not all that long ago I made up some large lettering for a friend using foam.
I used 12 volt battery, some nichrome wire and made up a jig to allow me to position the foam foe hot wire cutting.
Worked like a charm!
We primed, and painted the letters and glued them to his building facade.
T hey even sell some devices to cut foam.

 

[TheMan419]

My only comment is that if you get the liquid nitrogen look up how to use it to make ice cream. You won't be sorry.

Sorry I don't know anything about foam or how to cut it. But I like ice cream

 

[Dadnatron]

Islandtractor: I have thought about the layered technique, and that would be an option in which a waterjet would shine. But, I'd rather see that my 'easiest idea' won't work before I move to alternatives.

To give a little history.

I'm a Neurointerventional Radiologist and Pain Management MD. I've been working on people's brains, necks, and backs for 20+ years. About 3 years ago, I began waking up throughout the night with tingling in both my arms. I would wake up about 6 times a night. No pain, but the tingling was in the C8 nerve distribution. (outside of my both hands) Being who I am... I 'knew' what the problem must be, and also being who I am... I hopped in my MRI machine to confirm my dreaded diagnosis. And low and behold... I was clean as a whistle. No physical findings on my MR at all. So I was stumped. I was still waking up with the symptoms, but there was nothing 'causing them' ... until I began recognizing how I was positioned when I was waking up. I noticed my head was in an awkward position, and that it was 'comfortable' but would invariably result in the tingling in my hands. I knew the issue, and knew I had to refrain from postitioning myself in such a manner. However, I was doing it in my sleep, and therefore, had no control.

I bought about 10 different pillows in an effort to get some solid sleep. All without improvement. None of them worked to keep me in alignment. I knew what was necessary, but nothing was available. So, finally, after a horrible night of non-sleep, I grabbed an old foam mattress and a carving knife. I spent a few hours cutting that thing up into a shape which would position me comfortably but prevent me from moving into an ergonomically 'bad for me' position. And low and behold... it worked. Since my initial pillow design, I have not had a single night of the tingling in my hands. I have modified it several times to improve the functionality while laying on my back and both sides. There truly is a difference in all 3 positions and the pillow takes each of them into account. For instance, when I sleep on my right side, I sleep with my arm up beneath the pillow, but when I sleep on my left side, my arm is down.

All in all, I have studied this issue and talked with my patients and almost all I have spoken with wish they had better pillows. For those who are happy with their current pillow, I am happy, because my goal is to help people feel better. And there are enough people who can use my help that I don't need to coerce those who already are happy with their situation.

I've made about 20 pillows for patients, all by hand, and to a one, they said they wouldn't let me take them back if I paid them $1000. I've modified about half, after they have taken them and found certain issues. But each patient who has a pillow helps me make the next one better.

My biggest issue now, is actual production. I just need a working system in which I can go from CAD to pillow. I have acquisition, modification, and modeling figured out. I just need the CAD to pillow ability.

Concerning 'printing...' I have no idea, but the type of foam I've been using wouldn't work. However, I am not saying that might not be an option in the future, and I'll have to look in to that. I'd like that option best, because I'd have no waste.

And Jimmy... I understand. These are not for everyone and certainly not for those who have a system which works for them. I have been using gel impregnated open cell foam for that very reason. I am absolutely sure that if I can get this working, I will be able to hire a 'foam guy' who can help design a more efficient and breathable foam. I am still using 'off the shelf' foam, but I know enough about the physics of foam, to know that I can have better when I have a system in place that can use in in bulk. I can have what I need made for me. Your concern is a common concern, but in the 20 patients I have done so far, none have felt this was significant enough to preclude them from desiring the pillow.

 

[Kyle_in_Tex]

A cheap laser would be best, and less messy for a layered pillow.

I thought of one more option, but not sure if it will work depending on what type foam you use. Ozone. It will eat away many types of foam. You could mount an ozone generator to a tube mounted on a CNC and strategically "melt" away the foam. (If it is O3 susceptible).

 

[teg]

tingling... outside of my both hands...

Where do I sign up for one of these pillows???

 

[jwstewar]

We bought our nitrogen tank used. Ours holds 18 Liter and needs to be filled every 8 - 10 weeks or so. I think we paid $250 for it. It costs us $50 each time we get it filled. We use it to store goat semen. So try some agricultural sites on facebook and see if you can find a used one. I see them in various areas of the country for reasonable prices.

 

[damartin]

I do machining as a hobby, metal lathe and milling machine in my shop out back. I have also worked in the industrial gasses for 30 years. I worked at the bulk plants producing liquid N2, O2, Argon and worked a lot with liquid Hydrogen and also CO2. My background is in the maintenance of the plants, instrumentation, controls, mechanical and electrical. But I have also worked a lot with the products. I do have a fair amount of experience with machining and with very cold stuff.
I really think that liquid N2 will be too cold and the foam will be too brittle, also as mentioned displacing of O2 in the area that you are be working would be dangerous.
I believe there are people who do exactly the type of thing that you want to do for other uses. If so you just need to find out their methods, most likely NOT a closely guarded secret. I have a feeling that they probably use high speed CNC routers but the type of cutter is the key piece of information that you need. It may be as simple as a very course, very sharp carbide burr or similar. I could be wrong, just my opinion.
I would post your question at the home shop machinist, there are many people there with a lot of knowledge and experience machining all types of materials. It's worth a try and costs nothing.
Here is a link, The Home Shop Machinist & Machinist's Workshop Magazine's BBS . I hope I'm not breaking any rules by posting a link to another site on here. Good luck.

Dwight

 

[GLyford]

Saw a video of someone making car seats...they beveled the foam with an abrasive disk (about 1-1/2" or so) in an air die grinder.

 

[damartin]

I do machining as a hobby, metal lathe and milling machine in my shop out back. I have also worked in the industrial gasses for 30 years. I worked at the bulk plants producing liquid N2, O2, Argon and worked a lot with liquid Hydrogen and also CO2. My background is in the maintenance of the plants, instrumentation, controls, mechanical and electrical. But I have also worked a lot with the products. I do have a fair amount of experience with machining and with very cold stuff.
I really think that liquid N2 will be too cold and the foam will be too brittle, also as mentioned displacing of O2 in the area that you are be working would be dangerous.
I believe there are people who do exactly the type of thing that you want to do for other uses. If so you just need to find out their methods, most likely NOT a closely guarded secret. I have a feeling that they probably use high speed CNC routers but the type of cutter is the key piece of information that you need. It may be as simple as a very course, very sharp carbide burr or similar. I could be wrong, just my opinion.
I would post your question at the home shop machinist, there are many people there with a lot of knowledge and experience machining all types of materials. It's worth a try and costs nothing.
Here is a link, The Home Shop Machinist & Machinist's Workshop Magazine's BBS . I hope I'm not breaking any rules by posting a link to another site on here. Good luck.

Dwight

After I posted I was curious and did a search at the website that I posted and didn't find what I thought I would. And that would have been that it can be "machined" if the proper cutter is used. There were some posts about rubber and that grinding works well for that but not about cutters that work well for foam rubber. at the time of my first post I was pretty sure it was just a matter of finding the proper cutter and it could be done. Now I'm not so sure, I also searched Practical Machinist and found nothing definitive about a cutter that works with foam rubber. I then searched the web and did find this CNC - CNC Machine Cuts Acoustic Foam, Cushions and Bed Bridges it looks like they do some sort of "machining" of foam rubber but I think all of their cuts are in a straight line not free form. I found a few posts here and there about freezing it and the people had varied success but nothing about the magic bullet that works well for foam. I still think liquid N2 may be more trouble that it is worth and may be too cold and cause the foam to break. I did think about some of the new refrigerants that replace R22 and are legal to buy without a license that may not be too cold for your use.
I did use liquid N2 at times over the years for freezing various things, think bearing shaft and such. Good luck, I may research it a bit more and if I find anything I'll post it up. I would still join the Home Shop Machinist and post the question there as there are a lot of knowledgeable people there that could be very helpful. Again, good luck in your search.

Dwight

PS GLyfords post was interesting, maybe grinding is a workable solution.

One more thought, I think it may be worth a try to "machine" the foam rubber with a wire brush made for a die grinder and run at a fairly high speed. Here is a link to the style that I was thinking of, the kind without the twisted wire may work best, don't know.
Grinding Wire Brushes - Grainger Industrial Supply