1 H Narcus Metallizing of Plastics Reinhold Publishing Company 1960 Mandrel Design and Preparation

Mandrels may be made to reproduce accurately external or internal surfaces. The reproduced surface will be precisely the same as the surface upon which plating is initiated. The final plated surface will be rougher as the plated thickness increases. Design features of importance are avoidance of deep grooves or recesses, avoidance of sharp internal angles, and maintenance of liberal radii on corners. Figure 1 illustrates mandrel design considerations that should be followed.

Fig. 1 Factors to consider in electroforming mandrel design. Source: Ref 2

Permanent mandrels for electroforming concentric shapes must be designed with a draft or taper to permit removal of the mandrel without damaging the electrodeposit or the mandrel. If this is not possible, expendable mandrels must be considered. ASTM B 450 provides more guidelines in the design of electroformed articles (Ref 3). Preparation of mandrels for electroforming is detailed in ASTM B 431 (Ref 4). Special design considerations are often given to permanent mandrels being developed for complex parts that are to be produced in mass quantities or are of a complex nature, requiring speedy release from the mandrel. In these cases, knockout blocks or key release sections are designed into the mold, mandrel, or matrix to ensure quick and positive release and multiple uses of the master form.

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