Generally, zinc die casting tolerances are superior to those of aluminum and magnesium die castings. Zinc die casting can produce repeatability of less than ±0.001" for small components, often rivaling machining tolerances. Few other processes can easily achieve the same net shape performance. Many components are die cast to net shape and require no further machining. Due to zinc's ability to be cast with high accuracy, often complex assemblies are redesigned to consolidate component assemblies into a complex net shape casting, achieving substantial cost savings.
In general, zinc alloys machine rapidly, with minimal tool wear. Machining rates often rival those of free machining brass, and can be three times faster than for influences the selection of ZAMAK and ZA alloys over competitive materials. To review various machining guidelines for Zinc castings please visit our technical library.
Exceptional casting fluidity is displayed by all zinc die casting alloys, which provides superior thin-wall castability, regardless of the casting process employed. The recommended typical minimum wall thickness in zinc die castings has been reported to be 0.040" (compared to 0.060" in Aluminum die casting). However, due to todays improved die casting and alloy technology, die casting components have been produced with wall thicknesses as low as 0.008".
This thin wall capability combined with zinc's high strength allows components to be designed in zinc with the same strength and weight as aluminum die casting. With the cost savings advantages of the zinc die casting process.
Draft angle is the taper on the surface of a die required to facilitate removal of the cast part from the die cavity. In general, zinc alloys can be die cast with less draft angle than competitive materials. In fact, zinc components can sometimes be cast with zero draft angles. This is usually not possible with aluminum or magnesium alloys. Zero internal draft permits net shape manufacturing resulting in lower cost production.
The ZAMAK alloys, ZA-8 and ZA-12 have excellent dimensional stability characteristics. ZA-27, however, may require a stabilization heat treatment to minimize aging effects where exceptional tolerances are required. Our technical library has several downloadable files on dimensional stability of zinc die casting components.
Zinc die casting is unique in its ability to mass-produce complex parts to close dimensions, often consolidating multiple components into a net-shaped product. However, at times joining is still necessary. For these cases, a variety of joining and fixing methods are available including riveting, staking, crimping and spinning. These types of joing methods utilize zinc's high ductility, allowing for large amounts of deformation. Other methods of joining such as using inserts, spring clip fasteners, adhesive bonding and cast metal joining are also used to join zinc die castings to other components.
To learn more about joining and fixing zinc die castings to other components please download the following article: Joining & Fixing Zinc Alloy Die Castings