Why cut knurling patterns is the dinosaur of die casting

Die casting might not be regarded as a dynamic type of engineering by many, but changes are afoot in the industry when it comes to knurling patterns.

In the past, if you needed a knurl pattern created on a machined metal surface, it was cut with a knurling tool. There's nothing wrong with this traditional technique, but it is time consuming, has a large margin for error and adds an extra step to the design process.

It doesn't have to be this way though as die cast knurling provides a much needed update to the pattern process by adding texture to the surface of a machined part during die-casting.

This approach provides designers with greater options for design as surface texture can be cast for function and styling as the textures, cut patterns and variations of surface can be applied to compound curves and follow surface geometry. For example, a designer could incorporate a grip feature to the surface of the machined part or a company logo for branding purposes.

Die cast knurling is much quicker than cut knurling as it removes an entire step from the manufacturing process; instead of inserting an already cast piece of metal into a knurling machine, the casting and knurling is done in the one machine at the same time.

Just because the process is quicker, it doesn't mean that quality suffers; as the texture is applied to the die casting tool, it is reproduced exactly in each component.

As with any engineering process, there's always room for error, but these problems can be designed out of the process. For example, with die cast knurling, a designer will need to think about the tool part line and draft taper to ensure the feature can be cast, and this means the knurls need to be modified with draft taper so that these can be ejected from the tool.

Including subtle changes to the knurl's raised sections (for example by making the edges, fillets and draft rounder) can make releasing the metal from the tool easier and therefore make ejection seamless.

To avoid the knurl pattern being disrupted by parting lines, the gate locations can be carefully aligned with the knurl's geometry at the parting line to eliminate the tell-tale flat sections.

The world of die casting is constantly changing and new techniques such as die cast knurling take real design skill. What is clear, however, is that it can produce fantastic results at a much better cost than traditional techniques.

Mike Brettell is Dynacast UK's managing director.

Mike Brettell

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