Liquid Nitrogen Cooling

[jdh5556]

Has anyone ever heard of or knows if there is a way to use Liquid Nitrogen to cool a mold vs. chiller water? Thanks.

[Suhas]

I would think this would not be uniform. But this could be a good idea for cooling cores and such. What has been your experience?
Suhas

[jdh5556]

As you know, with the price of oil going up, that means the price of Polypropylene has gone up. At my company, I'm working on changing over our Polypropylene jobs to HDPE as a cost savings. We also run a lot of gas assist jobs, so I got this idea of seeing if we can use the nitrogen (in some way) as a way to cool down the molds to help with the heat transfer of the HDPE material. So just a thought for now, but was wandering if anyone has tried this before.

[rickbatey]

I feel there are two reasons this will fail: 1-severe stress will be molded into the parts. 2-the sudden quenching of the mold steel will cause premature stress failure of the mold inserts/base. Also how many people will have freeze burns just trying to set or pull a mold; let alone when a hose fails. Besides won't it have to transform from liquid to gas to cool, then you may need to add an exhaust hood over a press.
I must admit there are times when warming a mold decreased the cycle time and yielded much improved parts.
Rick.

[Ashley]

I feel there are two reasons this will fail: 1-severe stress will be molded into the parts. 2-the sudden quenching of the mold steel will cause premature stress failure of the mold inserts/base. Also how many people will have freeze burns just trying to set or pull a mold; let alone when a hose fails. Besides won't it have to transform from liquid to gas to cool, then you may need to add an exhaust hood over a press.
I must admit there are times when warming a mold decreased the cycle time and yielded much improved parts.
Rick.

I agree Rick , that is why we are going scientific. A lot of times a warmer mold will yield better cycle times, better quality, and better performance of the product.

[Suhas]

Rick, Fantastic answer! - Like it.
Suhas

[Pilot]

I can imagine, how it can work, But I have only one issue with tool stress. Main important think is heat transfer through wall of the tool.
For fast cycle you need a thin wall (between cavity and cooling chanel). This wall must be strong enought to overtake press from injection and holding press and thin as much is possible. ???? .... you have to solve this exercise.
Try to read this two links. http://utwired.engr.utexas.edu/lff/symposium/proceedingsArchive/pubs/Manuscripts/1995/1995-56-Sachs.pdf and US patent 5516470 https://docs.google.com/viewer?url=www.google.com/patents/US5516470.pdf

[Suhas]

As Rick rightly says and adding to that, you will not be able to use this directly to cool the part. One will have to get creative and come up with ways that will cool overheated pins and other stuff. As Pilot says, the thermal cycling is also a problem.
Suhas