Structural Modeling of Profiled Edge Laminae (PEL) Tools

Abstract

Profiled Edge Laminae (PEL) tooling is a thick-layer Rapid Tooling (RT) method that involves assembling an array of laminae—each having a uniquely profiled and beveled top edge—together in a precise and repeatable manner by registering each lamina’s bottom edge and an adjacent side edge to a fixture that has precisely machined edges. The processed laminae are then clamped or bonded into a rigid tool for use in manufacturing (e.g., as a thermoforming mold). Because a PEL tool is inherently more compliant than a solid tool, manufacturing personnel who are considering its use are understandably concerned about excessive tool deflection, which may lead to unacceptable changes in tool shape, decreased tool life due to high stresses and increased wear, and part dimensional errors. The ability to predict deflection (i.e., shape changes) in a laminated construction, either clamped or bonded, is extremely important to promote widespread acceptance of the PEL method. This paper develops basic analytical structural models for both clamped and adhesively bonded PEL tools, which will allow tooling designers and engineers to predict how changing various design parameters (e.g., the number of laminations, tool material, unclamped length of laminations, bonding adhesive, adhesive thickness) affect a tool’s stiffness. Deflection results from these models are shown to agree very well with experimental results. The usefulness of these analytical models is then shown by a design example. Finally, FEM modeling of PEL tools is demonstrated and shown to provide results that agree reasonably well with experimental results. FEM modeling may allow for prediction of shape changes to a PEL tool characterized by a complex three-dimensional surface and subject to arbitrary structural loads.