Aluminum Die Casting – Types of Die Casting Dies

Many potential new purchasers of die castings do not understand what a die casting mold looks like or what the different types of molds that can be constructed are. The purchase of a mold is a large expenditure for the customer base and many times die cast quotes do not clearly define what type or quality of mold that is being offered thus creating an “apples to oranges” price comparison in the evaluation of a project.

There are various types of die casting dies and each serves a critical need for the customer.

The choice of which type of die casting die the customer requires is usually determined by the following:

  • Size of the part to be cast
  • Volume of parts required either annually or over the life of the project
  • Requirements for “family” sets of parts
  • Desirability of core slides to replace a machine operation
  • Requirements for cast-in inserts to avoid assembly operations

Production Dies

These are the most common types of tools produced. They range from a single-cavity die with no slides, to a multiple-cavity die with any number of slides. The cavities are made from high-quality tool steel, retained in a quality holder block. The tool steel is heat treated to exacting standards that increase the life of the die cavities. Slides are components in the die that allow the casting to be formed with undercuts thus eliminating secondary machine operations and reducing part cost for higher quantity parts.

Production dies are built to critical dimensions, coring the maximum amount of stock from the casting, and allowing the agreed-upon amount of machining.


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Left Graphic: 1 Cavity Production Die

Right Graphic: 6 Cavity Production Die


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Left Graphic: 3 cavity family mold – 1 cavity of part A & 2 cavities of part B

Right Graphic: Unit frame with Die A & Die B. Die A is a unit mold with 1 cavity; Die B is a unit mold with 3 cavities. The center is part of the unit frame.

Unit Dies

A unit die is a special type of production die that is used for lower volume and smaller sized parts. It is a lower cost production tool that has a standardized main die frame and replaceable cavity units. These replaceable units are designed to be removed from the main die frame without removing the standard frame from the die casting machine.  This feature allows for quicker die set up time and becomes more effective for lower volume production runs.

The most common commercial types of unit dies are single and double unit holders. These types of dies are generally used for smaller parts, or a family of parts, with no slides or a mini­mum number of slides. Unit dies limit the use of core slides because of the configuration needed for interchangeable unit inserts and the limited space available.

 Trim Dies

The trim die is a tool that trims the runner, overflows, and flash from the casting. The trim dies are single or multiple cavity tools, made in the same configuration as the die casting die.

Depending on the shape of the casting, the trim die may be a simple open-and-close trim die or it may include as many slides as the die casting tool. In some cases multiple station trim dies will be used for successive trimming operations.

Trim dies require as much attention to detail in design as the die casting tools, and the use of quality materials should be specified to extend their productive life. They also reduce the labor cost in the deflashing of the die casting.

Die Materials

The grade of tooling materials to be used in the construction of a die casting die should be specified as high quality, at a minimum, and preferable premium quality. These requirements are based on the extremely high temperatures and pressures used in die casting production.

Tooling grade requirements will vary depending on the tooling component, the alloy being die cast, the critical character of the cast part design and the long-term production quantities desired. Every aspect of the proposed product’s design and production specifications must be discussed with the die caster before tooling material can be selected.

If you have any parts that may be a candidate for the die cast process please send your part prints and files toSales@diecasting.com

By Leonard Cordaro, President of Premier Engineered Products

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