Auditing a Die Casting Factory in China: Focus on the Process

This is the first in a series of articles about the way we do process audits.

When I look at the quality assurance agencies that offer services to importers in China, they all seem to prefer “horizontal” requirements (quality system, social compliance, environment…), rather than on industry-specific needs.

So we have developed ways to evaluate a factory’s production processes. In this article we’ll cover die casting factories.

What is die casting?

The basic principle of die casting is the process of injecting molten metal under high pressure into a mold called a die. The process of die casting involves a furnace to melt the metal, non-ferrous metal, die casting machine and a die.

The two most commonly used metals in die casting are aluminum alloys and zinc alloys, which can be used to produce complex components in a mass quantity for a vast variety of industries.

There are two different methods, the hot chamber and the cold chamber, each method has its own dedicated style of casting machine.

In a hot chamber process, the molten metal is held in a melting pot and melted in a furnace which is located on the machine, the molten metal flows into the shot chamber through an inlet at the plunger, the plunger then pushes the molten metal into the die under high pressure.

The hot chamber process is used for metals with low melting points and that have high fluidity such as tin and zinc.

In a cold chamber process, the molten metal has to be ladled into the shot chamber; this can either be carried out manually or by a robot, the plunger then pushes the molten metal into the die under high pressure.

The cold chamber process is used for metals with a higher melting point such as aluminum alloys and copper alloys.

Die casting is generally used to produce non-ferrous uniform parts with a good surface finish and good dimensional accuracy and stability in high volumes.

As usual, Wikipedia shows photos that are nicer than those we have taken (and free of any confidentiality agreement, too).

How our auditors check a die casting process

Our engineers report back on detailed checklists that are organized in 11 sections:

• Production Capacity
• Technical Capability
• Process Controls
• Material Parameters
• Process Cycling Parameters
• Preventative Maintenance
• Preventative Maintenance Effectiveness
• Tool/Die Storage
• Tool Design & Manufacturing Capabilities
• Housekeeping
• Tooling Efficiency

The objective for the importer is to assess the risks associated with a particular Chinese manufacturer, and to evaluate their capability.

Maybe some readers want to share their experiences with this process and the main ways it can go wrong?