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

[Dadnatron]

I don't think a waterjet will work because I need to cut 3D not all the way through the foam. Think of scooping out a half moon but leaving the backside. (these aren't that simple, but if you can think of a way that will take a block of foam, and cut a half sphere out of the center without cutting all the way through, then the rest of the cutting is likely to be possible with that machine as well.)

 

[GLyford]

does anyone have any ideas about how I could gain access to a flatbed CNC router, doesn't need to be 4D, just a regular 'sign' router would work, in order to test these bits?

Are you near any sort of "makerspace"? Google lists a couple in KY (Kre8now, NKY) but I can't see their webpages from work to see what machines or policies they have.

 

[Dadnatron]

I'll check that out. I did find one in Indianapolis and have sent them an email asking what they have available. I have looked into another in Indy a year ago. But they didn't have anything that would help, and they guy I contacted and acted interested in partnering flaked out and never followed up.

I would really like to find a partner, either on the 'foam expert or CNC expert' side. I have the medical side, idea, and end result figured out. What I need is someone in the production side which can help it get through the middle in a functional way.

A year ago, I thought about 'getting a Masters' at Purdue, because if I did, I would have access to their materials lab. But, alas... I bought a horse farm instead and now I have to look at other avenues. I don't have the extra time to take classes just to have access to equipment.

 

[teg]

I've done a little work with LN and Dry Ice. Not knowing your foam, I think LN will make it too fragile to work on. We use LN to crush up leaf and plant parts in a Mortar and Pestle.

Dry Ice we just use it to keep things frozen... but never exposed either to foam. Would be "cool" to see what happens (pun intended).

We fill our (borrowed) Dewar from the larger nitrogen tank on the first floor. The big tank, I think were 50 gallons (3 feet?? across and 5 feet tall??), if I remember correctly, we fill our Dewar with 0.70 kg of liquid (~1.5 pounds). The Dewar tank was pretty large, 20" tall and 10" diameter (just estimating). {edit - Label says it's 4 liters so about a gallon}.

Good luck... not sure any of this was useful...

PS. forgot I had some photos (less, it didn't happen...)

View attachment 518272

(smaller photo)

 

[newbury]

Have you looked into how the foam will "freeze"?
As an excellent insulator it may be difficult to freeze with N.
What happens if you just leave a block in a normal chest freezer turned down as far as possible overnight?

 

[CincyFlyer]

Soak the foam in water, freeze and shape frozen???

That was my thought; that's how the machine some contact lenses!

 

[Dadnatron]

Have you looked into how the foam will "freeze"?
As an excellent insulator it may be difficult to freeze with N.
What happens if you just leave a block in a normal chest freezer turned down as far as possible overnight?

I have frozen it in the freezer, and it firms up, but not enough. I don't know what will happen with the LN. The Dry Ice might be enough.

 

[Drunkwater]

How big is your CNC setup? I'm thinking you could pick up an old chest freezer off craigslist and run the entire rig inside the freezer, or if it's bigger than a benchtop unit, build a larger enclosure and scavenge the compressor and coils. If this is more than a one-off project, the cost and practicality of N2, CO2 etc will quickly add up.

 

[IslandTractor]

I have frozen it in the freezer, and it firms up, but not enough. I don't know what will happen with the LN. The Dry Ice might be enough.

Dry ice is available as pellets about the size of popcorn. Just pour some in the bottom of a cooler, put your foam in and fill with more dry ice pellets. Probably will take a few hours to cool down.

 

[CalG]

I bet there is an abrasive paper /disc/flap wheel of some kind that will "mill" soft foam without any additional support. Just the foams own propensity to return to shape and inertia. One might need to move slowly, and have good dust removal.

3M abrasive products would be a start.