Zinc alloys are some of the cheapest metals available. Despite a low price point, they have good mechanical strength, are easily machined, and resist mechanical shocks well. Complex components are often initially die-cast and then have critical features machined into them, reducing overall machining time and cost. The automotive industry makes extensive use of CNC machined zinc alloys.
Zinc (denoted as Zn on the periodic table) is a relatively common non-magnetic metal. It is typically alloyed with aluminum, magnesium, and copper. This class of zinc alloy is referred to by the name Zamak (the term originated as an acronym for the element names in German: “Zink, Aluminium, Magnesium, and Kupfer”). These alloys are usually supplied in the form of ingots due to their extensive use in die-casting applications. Zinc has excellent damping capacity; it is highly ductile and exhibits long-term dimensional stability. Die-cast Zamak alloys maintain high levels of precision and therefore require less machining to bring the part into the required tolerances.
|Application||Zinc alloys are used for a range of applications to include cosmetic vehicle parts, complex part housings, and fuel system components.|
|Advantages||Resistance to shock loads, Good wear resistance, Long-term dimensional stability|
|Disdvantages||Not suitable for extreme-temperature applications|
|Lead Time||Lead time is generally a minimum of 3 days. However, this can increase depending on availability or if the parts are to be internationally manufactured.|
|Tolerances||Machining tolerances depend on the zinc alloy used, but a tolerance of 0.005” (0.13mm) is generally achievable.|
|Wall Thickness||A minimum wall thickness of 0.03” (0.8mm) is achievable. This can vary depending on the ratios of wall thickness to planar dimension. The specific zinc alloy will also affect the achievable minimum wall thickness.|
|Max Part Size||The maximum size of the part is determined by the machines available and the complexity of the part.|
The Zamak 3 alloy contains 4% aluminum while less than 1% is composed of copper and magnesium. Zamak Zinc alloys exhibit similar machinability to copper but are less abrasive to tooling. Automotive part shells and small electric motor casings are typical applications for this type of zinc.
|Tensile Strength, Yield (MPa)||Fatigue Strength (MPa)||Elongation at Break (%)||Hardness (Brinell)||Density (g/cm^3)|
Zinc alloys respond well to a wide range of surface finishes. Some of the more common finishes for CNC machined zinc are listed below:
Zinc is a cheap material, so at least some cost savings are built-in. However, to further leverage these savings, refer to the tips below.