Ice Fixture

[MattW]

A search didn't turn up anything on this, so I thought I would share... I was handed a plastic part that had a bunch of approx 5mm across sort of square posts sticking up, with the request to take 4mm off the top. I tried supporting them with wax, which worked great for the support portion, but the wax reacted in a negative way with the plastic, which subsequently crumbled. So I filled the part with water and froze it. This worked great, and cleaned way easier than wax.

 

The interesting side story is the freezer. We have a walk-in "-80" freezer here, that I hadn't been in before. You are getting a bit chilly after 30 seconds inside. It turns out that it is -80C, that works out to -112F.

[Zero]

thats actually a really cool idea...as long as your fixture doesn't melt away before you're done needing it..

[Guest CNC Apps Guy 1]

ROFL @ Matt... -112 F. I'm sure you went in there with your short sleeve shirt on also right??? LOL

[MattW]

Yep, short sleeves. I was thinking "this isn't that bad" when I first walked in (and thinking it was a mere -80F), but that went away pretty quickly. It really hits you when you walk out- "I'm cold and I wasn't in there very long". There are some beefy parkas outside the door, I will be wearing one if I have to be in there more than a minute.

[ReDEyZZ]

Be careful I live in central canada, I had frosbite after being outside for less than 3 minutes , in -45C deg weather it hurts like a bi^%$.....quote from webpage....- 50 and colder Uncovered skin will freeze in less than two minutes. Wear face protection. Outdoor work or travel is not recommended.brrrrrrrr

[Randy Morton @ Clem Industrial]

Jarret, I live in Edmonton too. Don't give such accurate impressions of our country. =] It's cold enough 13 months of the year, I don't want think about it today when it's only -42 c here.

[Surface]

Witte makes a freeze plate which works great to hold parts. The ice suspends the part, keeping it much flatter than a vacuum or magnet. I think they call it an Icevice.

[Lars Christensen]

Never thought of using ice as support for something like that, thank you for sharing Matt

[Matthew Hajicek - Singularity]

You can also get some Bismuth based alloys that melt at your choice of temperatures from about the boiling point of water down to below room temperature. I'd been thinking that some of this with a melting point of about 150° - 170°F would work well for fixturing flimsy parts. You could put the fixture in hot water to load and unload, and it would be solid at room temp.

[Steve Hattori]

We use the bismuth, and it works great. Its called "Cerromet" and you can get it from Mcmaster- Carr... Never tried ice, but i don't have a -112F freezer, either... Cool idea, though!...haha

[Camdude®]

we used to have a lathe job that we filled with water and froze. worked well on our thin walls apps, just had to be careful not put in too much and expand the part when the ice expanded.

[88Matt]

Thanks for the info. Matt.

 

What was your tolerence? How much distortion did you get when the water froze?

[Jeff Kemper]

Get out the margarita blender and make an ice water "slurpie", pre-cool part and fixture; will reduce or eliminate any expansion issues.

[MattW]

Tolerance? "take about 4mm off the top". I didn't measure it, but it wasn't visibly deformed.

 

 

The part holds little vials that sit flush with the existing top. We needed some clearance so a gripper could come down and grab the vial.

 

I've seen (pictures) of the Witte Icevice, I think their literature says -20 is optimal. For an experiment, I put this on an aluminum block with a film of water. It was sticking really good, but the aluminum got to room temperature in about 5 minutes. If we put our physicist hats on, water has "an extraordinarily high latent heat of transformation" associated with going from ice to water, so it will stay solid for a while. For this particular part, I just threw it on a manual mill and gave it a haircut (posts only, not the perimeter).

 

I have also used the cerro-bismuth alloys for holding a series of parts I cut out of a single block. It worked great for aluminum, I melted out the alloy in hot water. The parts were floating on top of the alloy, and the alloy didn't stick to the aluminum at all. It left residue on stainless when I tried it there.