8 die casting defects and how to overcome them

Die casting is a manufacturing process that uses high-pressure molten metal to create intricate metal parts. It is a versatile process that can be used to produce a wide variety of parts, including automotive components, electronics housings and medical devices.

While die casting is a reliable process, it can sometimes produce defects. This article discusses some of the most common die casting defects, their causes and solutions.

Die casting defects

When zinc die casting first became available, it quickly gained recognition as a lightweight and cost-effective alternative to other alloys such as tin and lead. Over the past century, zinc alloys have made steady progress. While zinc has always been recognised for its high strength, the introduction of the Zamak family, and now the revolutionary EZAC™ alloy, has further enhanced the suitability of zinc alloys for hot-chamber die casting across a wide range of applications. Prior to the introduction of EZAC™, zinc was often overlooked for applications requiring high tensile strength, especially at high temperatures. Additionally, most zinc alloys exhibited low creep resistance compared with other materials. These areas for improvement were the primary focus during the creation of EZAC™, resulting in a zinc alloy that surpasses previous limitations.

Heat checks

Heat checking is localised cracking or surface damage that can occur on the die casting mould. It is caused by thermal stress and cycling, which can be exacerbated by factors such as inadequate cooling, excessive overspray or thick mould sections.

Soldering

Soldering is the formation of a thin metal layer on the casting surface. It is caused by erosion or dissolution of the die material due to uneven cooling, localised high temperatures or improper metal flow. Soldering can be prevented by improving cooling, optimising part design, and improving metal flow management.

Cracks

Cracks are fractures or separations that can occur in the die casting. They can be caused by stress concentration, rapid cooling and uneven thermal gradients. Cracks can be minimised by evaluating casting geometry, adjusting process timing and enhancing thermal management.

Dimensional issues

Dimensional issues involve deviations from the required dimensions and tolerances in the die-cast part. They can be caused by unrealistic drawing tolerances, variations in process parameters and thermal expansion effects. Dimensional issues can be minimised by optimising tolerances, controlling process parameters and considering thermal effects.

Flash

Flash is excess material that escapes between mould halves, forming thin fins or flanges on the casting. It can be caused by insufficient machine tonnage, die wear or misalignment, and suboptimal process parameters. Flash can be prevented by ensuring adequate machine tonnage, carrying out regular die maintenance and optimising process parameters.

Shrinkage porosity

Shrinkage porosity is characterised by voids or cavities formed due to the shrinkage of molten metal during solidification. It can be caused by non-uniform wall thickness and abrupt section transitions in the part design. Shrinkage porosity can be minimised by optimising casting geometry and implementing effective thermal management.

Flow marks (cold flow, non-fill, etc.)

Flow marks appear as visible lines or streaks on the casting surface due to the flow of molten metal during mould filling. They can be caused by flaws in part geometry and inadequate gate and runner design. Flow marks can be minimised by refining part geometry, using flow simulation software and implementing real-time monitoring.

A comprehensive understanding of common die casting defects, their causes and practical solutions is pivotal to engineering high-quality castings. By implementing the solutions discussed in this article, manufacturers can effectively address defects, improve production efficiency and deliver products that meet exacting quality standards.