Today’s Zinc Casting Technology for Tomorrow’s Markets

Although manufacturing by zinc die casting has a long history, new developments in alloys and in die casting technology continue to make the zinc die casting industry relevant in today’s modern world.  Zinc die casting is a low-cost process that produces components with high precision and performance.

Zinc die casting is an exceptionally cost-effective manufacturing process. For instance:
 

• Zinc die castings can be cast net-shaped, eliminating most if not all secondary forming operations.
• The strength, bearing and wear properties of zinc die casting allow for consolidation of parts which reduces or removes the need for secondary inserts or fasteners.
• Zinc provides the best surface finish of cast metals allowing easy application of decorative coatings by plating or painting.
• The melting temperatures of zinc alloys are very low compared to other competing alloys such as aluminum, magnesium, copper, and steel components. This means:
  • Tooling (die) life is up to 10 times longer than other casting processes.
  • Cycle times are much faster due to zinc’s low heat content.
  • Energy costs are lower.  

As a rule of thumb, functional or nondecorative castings that weigh up to about one pound (in zinc) are very cost effective compared to other processes, and when a decorative surface plating is required, much larger castings can be manufactured at lower plating costs.
 

How do zinc alloys demonstrate high precision and performance?

Zinc alloys can be cast to very tight tolerances and specifications. Net shape casting eliminates the need for subsequent machining. Zinc alloys can be cast with the lowest draft angle and more easily cast with zero draft (in some designs). The dimensional stability allows easy maintenance of critical dimensions throughout a production run and allows for pressure-tight connections without gaskets.

In most applications zinc die castings are stronger and can have higher performance than many other alloys and processes. Depending on the zinc die casting alloy chosen, yield strength can range between 32-57 ksi (221-396 MPa), elongation can range between 1 percent to 13 percent, and hardness can be achieved up to 120 Brinell.

Due to Zinc’s low melting temperature, applications at higher temperatures pose a challenge for zinc alloys; however, if the stress levels are low enough, zinc die castings may still be a cost savings option.  In these cases, further investigation and discussion with a zinc die casting professional is suggested.

Density is only a perceived challenge for zinc.  The density of zinc is 6.6 grams per cubic centimeter, which is approximately 2.5 times heavier than a typical aluminum alloy. In some cases, this weight difference is embraced and used to help stabilize (vibrational dampening) components or improved haptics (feel/sensory). However, today’s engineers take advantage of zinc’s combination of higher strength and fluidity to design thin wall and complex shaped components in zinc that compare in strength and weight to lighter alloys, but at lower manufacturing costs.

What new die casting technology is available?

Today’s zinc die casting processes consists of all the latest manufacturing technology including closed loop control systems, shot monitoring, temperature-control units, and vision systems. One of the most recent advancements in die casting technology is the ability to cast components without runner systems. This technology not only dramatically improves casting quality, but also further improves cycle time, energy costs, and efficiency (more cavities per die). Using this technology helps lower the overall carbon footprint.

What about recyclability?

Zinc die casting alloys are very recyclable.  According to the International Zinc Association (IZA), approximately 30 percent of first-use zinc production is made up directly of “reused zinc,” such as scrap and oxides.  At the die casting facility, production scrap is often remelted at rates of up to 50 percent, depending on size and shape of the scrap  Zinc is a “self-cleaning” alloy. The dross that is formed during the process is lighter than the alloy, and therefore rises to the top of the melt and is easily skimmed. The resulting dross can also be recycled and re-used in various primary productions of zinc. Over the past decade, zinc recycling has doubled, and continues to grow in the industry.

Why is zinc recommended for tomorrow’s markets?

Today’s global manufacturing is complex and competitive. Engineers are becoming increasingly cognizant of today’s demand for low-cost manufacturing, carbon neutrality and recycling. In addition, global geo-political risks continue to rise, making onshoring to North America more common.  Growing and future markets such as robotics, alternative energy, electric vehicles, and accessories are perfect for the zinc die casting industry, especially as engineers incorporate new alloys and die casting technology available to them.
 
Ryan Winter is vice president of engineering services for Eastern Alloys Inc., a manufacturer of zinc-based alloys. Martin Gagné is principal of ZELIXIR Inc., a technology and market development company.