Ribs

Plastics One Injection Molding

Many times the stiffness of a part must increase because of the load applied to the part design. One of the easiest ways to cure this problem is change the part geometry by adding ribs. The use of ribs is a practical way and economical means of increasing the structural strength of a part. But there are guidelines that govern adding ribs without causing sink marks or surface blemishes to your parts.

1) Rib thickness should be less than wall thickness. A rib thickness of 60% to 80% of nominal wall thickness is recommended.

2) To increase stiffness increase the number of ribs or "gusset plates", another feature designed to strengthen the plastic part.

Height: max. height of three times nominal wall thickness of part
	Spacing: minimum of two times nominal wall thickness of part between ribs

3) For a given stiffness, it is better to increase the number of ribs, not the height.

4) For thick ribs "core out" the rib from the back. This creates a hollow space underneath the part and maintains a uniform wall thickness.

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