Type of rubber recommendation 1

[Paul Hins]

I am looking for a recommendation for the type of rubber to make a square profile O-ring that meets the following criteria

1)The O-ring will be subject to temperatures down to -45ish Celsius (-50ish Fahrenheit) and still remain flexible enough to apply the following pressure.
2)The O-ring will be subject to compression pressure of 101.3 kPa, 851.8 kg total (14.696psi, 1878lb total)
3)The O-ring needs to be made of food safe material.
4)Material is such that it could be mixed and cast in a mold in a home workshop environment. ​

The dimensions of the O-ring are as follows

A = 318mm
B = 324mm
C = 2.5mm


Any recommendations would be greatly appreciated.

 

[Pud]

Item (4) leaves you with silicone or polyurethane.
Items 1-3 you'll have to check with manufacturers.


Politicians like to panic, they need activity. It is their substitute for achievement.

 

[Compositepro]

I think only a student would consider molding their own o-ring. Wby?

Why square rather than round? Why not use cord stock? I bet there are a number of misconceptions involved in the reasoning. But, perhaps not.

 

[Pud]

I hope the op realises that elastomer do not reduce in volume when a force is applied. That's why 'O' rings sit in rectangular or trapezoidal grooves.


Politicians like to panic, they need activity. It is their substitute for achievement.

 

[Paul Hins]

COMPOSITEPRO, I can make the mold fairly easily, but I am wondering if it would be better to simply laser cut it it out of EPDM. Although I am not sure if the laser would cut it clean or melt it.

The gasket that I need to make fits inside a deep (approx 1" deep) grove and there is the edge of a cylinder that comes down inside the grove. These are existing components that I have no control over. But I need to seal between these two. I am afraid a round profile O-ring would slip to the side of the cylinder as it comes down. The wall of the cylinder is only about 3mm.

The cord stock would have to be glued at the ends would it not? I am not sure it would be perfect enough. The application forms a vacuum down to about 400 micron. I may also need to be making quite a few of them.

 

[Paul Hins]

PUD, That is probably a good thing that it does not reduce in volume. It would make a better seal I think as material bulges out.

 

[3DDave]

An o-ring can take as much force but applies it to a smaller area, increasing the resistance to pressure differential which is what a seal is intended to do. I've only used square/rectangular seals when it made retaining the seal with the cover removed much easier - a similar thing was done on some engine cast valve cover for much the same reason but there the pressure differential is close to zero so it mostly stopped oil from migrating.

In any case, if either shape is over-confined then it will tend to get pinched out of the groove and fail to seal well at all.

 

[theone1211]

nice info.

 

[BridgeSmith]

I am wondering if it would be better to simply laser cut it it out of EPDM. Although I am not sure if the laser would cut it clean or melt it.

Yep, much easier. Laser should cut it cleanly. It might melt the edges a little, which would probably help it seal.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[Compositepro]

Surface finish of a rubber seal is very important. Laser cutting would be inappropriate.

Cord stock does not need to be glued. Rubber seals to rubber as well as anything else. Glue residue and missalignment are additional problem issues.

I don't understand the description of the geometry given. A drawing would help a lot. It still seems a round cross-section would work. You need to understand the functional differences between an o-ring and a gasket.