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I am making a cylinder of polypropylene that must be pressurized (2 bar). The rough dimensions of the current design (A) are 7 cm tall, 5 cm in diameter, and wall thickness of 1-2 mm. The issue is that the end plate (disc) begins to bulge when the pressure is increased.

I want to make a new design that is stiffer. Is there a shape/pattern that is better in terms of preventing bulging than naively increasing thickness?

I want to maximize stiffness (prevent bulging) while minimizing the thickness of the end plate. I don't care about how much material I use. I.e. if the stiffness is the same solution B and C are equally good.

Constraints

  • The end plate must be flat on the inside, but there are no constraints on the outside shape.
  • The final product must be injection moldable.

enter image description here

Faur
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2 Answers2

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"... while minimizing the thickness of the end plate. I don't care about how much material I use." Those statements are in conflict with each other. If the end plate must be flat on the inside, you have constraints on the design.

To reinforce the end plate without increasing thickness, consider a web of plates perpendicular to the end plate. If properly tapered, it can be injection molded. The thickness of the webs will determine strength, along with the depth that the web encompasses.

The photo below is of an experimental rats "maze" from ResearchGate.net but represents an exaggerated image of my suggestion.

rats maze radial reinforcement

You can set the height of the walls of the maze to meet your requirements, as well as add additional walls and/or extend them to the center, as your cylinder is not required to contain rats.

This suggestion does increase the thickness, however, but it also does not as as much material as would a flat thicker plate.

fred_dot_u
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This is a minor addition to Fred_dot_u's answer.

Regarding the radial stiffeners the best shape for the stiffeners (minimizing the deflection for a given weight would be a stiffener with the following shape (in green).

enter image description here

This optimization only makes sense if you have large production numbers, otherwise you can use plain rectangular profile for the stiffeners if production is small.

It is best that the stiffeners are all connected in a central hub like the following.

enter image description here

NMech
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