Zinc Die Casting Process and Design Considerations

The zinc die casting process is a common metal forming process widely used in automotive, electronics, home appliances, construction, and other fields. Zinc alloy has good fluidity, wear resistance, corrosion resistance, and excellent surface treatment performance, making it one of the preferred materials in the die casting industry. This article will provide a detailed introduction to the zinc die casting process and discuss the key considerations in die casting manufacturing process.

Overview of Zinc Die Casting Process

The zinc die casting process involves injecting molten zinc alloy into a mold and rapidly cooling it under high pressure to form a shape. The basic process includes the following steps:

Mold Design and Manufacturing

The mold is the core of the die casting manufacturing process, and its design directly affects product quality and production efficiency. The mold is typically made of high-strength steel and has a complex cavity structure to ensure the zinc alloy can fill it uniformly and form the desired shape.

Melting and Pouring

Zinc alloy is heated in a furnace to a molten state, usually controlled at temperatures between 400°C and 450°C. The molten zinc alloy is injected into the mold through a pouring system. The design of the pouring system must ensure that the metal can quickly and evenly fill the mold cavity, avoiding defects like porosity or cold shuts.

High-Pressure Forming

After injecting zinc alloy into the mold, a die casting machine applies high pressure (typically hundreds to thousands of tons), causing the zinc alloy to rapidly cool and form in the mold cavity. High-pressure forming helps improve product density and surface finish.

Cooling and Ejection

The formed zinc alloy part is cooled in the mold for a period until it solidifies completely. Then the mold opens, and the ejection mechanism pushes the part out of the mold. The cooling time depends on the part's thickness and shape.

Post-Processing

After ejection, the zinc alloy part usually requires post-processing steps such as deburring, polishing, and surface treatment (e.g., electroplating, spraying) to improve its appearance and performance.

Considerations for Zinc Alloy Die Casting Design

When designing zinc alloy die castings, designers need to consider multiple factors to ensure manufacturability, functionality, and cost-effectiveness. Below are key considerations for the design process:

Wall Thickness Design

The wall thickness of zinc alloy die castings should be as uniform as possible to avoid areas that are too thick or too thin. Excessive wall thickness can lead to uneven cooling, causing shrinkage or deformation, while too thin wall thickness can result in inadequate filling or insufficient strength. Typically, the wall thickness of zinc alloy die castings is controlled between 1.5mm and 4mm.

Draft Angle

To facilitate ejection, the side walls of zinc alloy die castings should have a certain draft angle. The draft angle usually ranges from 1° to 3°, depending on the part's shape and height. Too small of a draft angle increases the difficulty of ejection and may damage the part.

Fillet Design

Appropriate fillets should be designed at the corners of the part to avoid sharp angles. Fillets can reduce stress concentration, enhancing the part's strength and the mold's life. Typically, the fillet radius should be no less than 0.5mm.

Rib Design

To increase the part's strength and rigidity, ribs can be designed at suitable locations. The thickness of the ribs is usually 50% to 70% of the main wall thickness, and their height should not be too high to avoid affecting the metal flow and filling.

Hole and Slot Design

When designing holes and slots, deep holes and narrow slots should be avoided as they increase mold manufacturing difficulty and may result in poor filling. The diameter of holes should be no less than 2mm, and the width of slots should be no less than 1.5mm.

Surface Treatment Considerations

Zinc alloy die castings usually require surface treatments such as electroplating or spraying. The design should consider the requirements for surface treatment, avoiding overly complex textures or deep recesses that could affect the surface treatment's effectiveness.

Mold Life and Cost

Mold design and manufacturing are crucial in the die casting manufacturing process. The mold's life and cost directly affect the product's production cost. During the design process, the mold structure should be simplified as much as possible to reduce its complexity and manufacturing difficulty, thereby lowering mold costs and extending its life.