Traditional snap-fit design methods focus exclusively on design of an individual locking feature such as a cantilever hook or an annular lock. Location and orientation of other significant features on the two joined parts are not considered. This paper presents: (1) a comprehensive design methodology for nesting plastic parts via snap-fits and, (2) the concept of a part nesting table to encourage good design practices.

This nesting approach is based on relatively new methodologies and guidelines for arranging features on a plastic part. The authors advocate a nesting which is a statically determinate assembly and minimizes the use of snap-fit features. The advantages of such an assembly include robustness with respect to tolerance and warpage concerns, maximum utilization of existing “natural” part features, and a reduction in the number of locking features needed. The entire process is presented as an improved paradigm for attachment design and assembly.

It presents the concept of a part nesting table to help designers produce nested plastic assemblies. In this approach, degrees-of-motion to be removed are represented as columns in a table, and individual features are entered as rows. Advantages of this structured approach include recognition of under constrained and weakly constrained assemblies, identification of over constrained assemblies, and first-level optimization of lock location and assembly direction. Work is continuing on computer implementation of this approach so that force and moment values can be deduced at the feature level.

This content is only available via PDF.
You do not currently have access to this content.