Poor rib design can actually make a part weaker—not stronger.
How do you like your ribs? We recommend well done because failure to observe basic design rules on thickness, height and radii could lead to premature failure of an otherwise flawlessly designed part. Poor rib design could also create cosmetic problems in a part or slow molding time.
The primary purpose of ribs in plastic design is to improve the stiffness of the structure. Ribs do this by increasing sectional properties, specifically the moment of inertia. Because stiffness is a function of moment of inertia and Young’s modulus, you can also improve stiffness by increasing the modulus of the material. You can do this either by using more glass fiber or by using a material with a higher modulus. However, there are often practical and economic limitations to this approach.
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