I make specialized flapper valves that are similar to O-Rings. The current model uses aluminum sheets as base disks that adhere to the rubber (2 part urethane). The rubber is poured into the waxed mold and then topped with an aluminum piece. Unfortunately, there is currently no way to remove the rubber from the mold without damaging the mold or rubber material.

The mixing, degassing, pouring, and subsequent removal of the rubber must be done perfectly in order to create a seal. Since this process is done almost entirely by hand, there is a large margin of error and I end up with a lot of waste. Not only that, but I spend an extensive amount of time cleaning the mold to remove even the specks of dust. Also, I believe the aluminum piece may be preventing the rubber from moving easily making it more difficult to get a good seal with even the slightest imperfection. I should also note that the center hole is what gets worn away the fastest and is my most common issue with age.

Previous thoughts have been to weld handles to the aluminum pieces to make removal easier. However, welding would warp the aluminum. Another idea was to put screws through the aluminum but this would result in a rubber piece with holes/tears. A different idea was to remove the aluminum entirely and make the rubber much thicker. The center hole would still need to be reinforced though and this method may reduce the life of the flapper valve. Current implementation has added "ears" to the edge of the aluminum but as these sit flush against the mold, they are still near impossible to remove without damaging the mold.

I am not an engineer nor am I familiar with this type of work so pointing me in the right direction, any thoughts, and any comments are appreciated; thank you!

  • $\begingroup$ If the thermal properties of the aluminum are not essential, a plate of magnetic stainless steel (400 series) might be a way to remove without creating hot-spots or cold-spots due to the addition of handles. Also if the only problem with handles is warping, then a grinding step may restore flatness??? $\endgroup$
    – Pete W
    Jan 14 at 23:00

1 Answer 1


This community is not dead, but it is assuredly populated by people (like me) who make a living by being paid to solve problems exactly like yours.

Now, it is common for small design and manufacturing firms to design products and processes that they lack the expertise to troubleshoot when things go wrong on the factory floor. It is also common for them to lack the money to hire experienced troubleshooters to solve those problems. This is a fact of life...

Anyway, here are some ideas.

Review the mold design and be sure to include generous draft angles throughout, of order ~1.5 degrees per side.

Consider including either a stripper plate, ejector pins or ejector blades to the mold design to pop the part out of the mold when finished.

Machine the white mold base out of teflon.

Buy you some industrial-grade mold release compound and spray it onto the mold surfaces before each run.

Send out the aluminum lid piece for teflon coating. Most big cities have a teflon shop that resurfaces commercial cookware with fresh teflon. Seek one out.

If you do not know what draft angles, mold release, stripper plates, ejector blades or pins are, you really have no business trying to run a process like this, and you should consider farming out the manufacture of the valve membrane to someone like Vernay Laboratories in Ohio.


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