Die Casting

Die cast parts often show small marks or seams caused by how the metal is injected and released from the tool. These are normal and part of the process, but they can be reduced or improved through finishing.

What to Expect on a Die Cast Part:

• Gates and vents are needed to let metal in and air out — these will leave small marks.

• Ejector pins help push the part out of the tool — they also leave visible circles or dents.

• Flash is thin excess metal around split lines that appears where the tool separates.

How We Improve the Finish:

• Clipping removes the larger metal feed and vent points after casting. This can be done mechanically or hydraulically.

• Because casting alloys don’t break as cleanly as steel, some small leftover marks (called “witness”) are normal.

• If a cleaner finish is needed, we can machine the area using CNC to smooth it out.

Surface Finishing Options:

After clipping, we can further improve the part’s appearance using:

• Shot blasting or tumbling to smooth sharp edges and reduce flash

• Powder coating to apply colour and cover minor marks

• Nickel plating or chromate coating for corrosion protection

Note: Die cast parts don’t anodise well, and over time the surface may darken from oxidation. A surface finish is recommended for appearance and protection.

Tooling timelines depend on complexity but typically range from 6–10 weeks including sampling and validation.

While die casting offers rapid, near-net-shape metal production, not all features can be formed in the die itself. Some must be machined after casting to achieve the required function or tolerance.

Design Limitations for Casting

Some features are better suited to post-cast machining, such as:

• Holes not aligned with the split line

• Parallel-sided features (draft is required for ejection)

• Threads, especially if the axis is not along the split line

• Undercuts or complex internal forms

CNC Machining Capabilities

• GUK Magnetics offers multi-axis CNC milling and turning to finish components to specification.

• CNC provides high repeatability and is used for nearly all post-cast machining.

• This enables tight tolerances and complex geometries that can’t be achieved through casting alone.

Insert Features and Strength Zones

• High-load features (e.g. tapped bosses) may require added strength.

• Press-fitting stainless steel inserts is often preferable to casting around them.

• Some components (e.g. motor shafts) can be cast around, depending on design.