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Engineering Materials

Design Guide

When designing parts for thermoplastic injection molding, it’s important to consider a set of design guidelines. These will help you design parts that can be molded without issues and meet the requirements with respect to structural performance, weight, cost and aesthetics.

DSM Engineering Materials design guide

Thermoplastic materials as a construction material have a lot to offer in a wide variety of applications. They are available in a broad range of base polymers and can be tuned to meet specific requirements by including additives. Depending on the plastic concerned, the benefits of thermoplastic materials include their high strength to weight ratio, non-conductive properties, flexibility and chemical resistance.

To make optimal use of the inherent characteristics of thermoplastic materials, one must be aware that there are specific guidelines for designing with plastics. By applying these guidelines consistently, the result will be a part that can be mass-produced smoothly and lives up to the expectations in terms of dimensions, properties and appearance.

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  • Draft angle

    Part surfaces parallel to the draw direction of the mold should be tapered to facilitate ejection of the part after molding.

  • Radii and chamfers

    When designing in plastics, applying radii or chamfers to sharp corners is of key importance for a parts manufacturability, dimensional accuracy and load-carrying capacity.

  • Wall thickness

    Specifying a parts nominal wall thickness is the first step in determining its manufacturability, performance and cost.

  • Bosses

    A boss is mostly a cylindrical protrusion on a part that can act as a positioning aid, a fixation point or a bearing surface.

  • Holes

    A hole in a part can have many functions, including acting as a fixation point, offering passage to other parts and reducing a parts weight.

  • Coring

    In the design of injection molded plastic parts, thick sections should be avoided. Coring, locally eliminating material in these sections, is a way to pursue a uniform wall thickness.

  • Undercuts

    If a part has an undercut, it means that it can’t be ejected from the mold without taking specific measures regarding tool construction or additional operations during the molding cycle.