Dies

Translating Ideas Into Shapes

Aluminum extrusion dies can be made to form a wide array of shapes and sizes. Here we provide answers to some of the most frequently asked questions.

Understanding product requirements

Effectively translating customer product requirements into extruded, fabricated and finished components is one of the daily challenges facing experienced die engineering professionals. It’s a process that starts with extensive information gathering followed by an evaluation of how the shape fits into the customer’s manufacturing plans. To that end, a checklist of product and specification details is required from the customer before engineering can quote a shape. These include: alloy type, cut length, finish required, exposed surfaces, size of order, yearly volume and end use of product.

The extrusion die is a steel disk (typically H13 tool steel) with the intended cross-section of the final extruded product cut through it. Dies are broadly grouped as solid dies, which produce solid shapes, and hollow dies, which produce hollow or semi-hollow shapes. Combinations of a solid, semi-hollow and/or hollow shape may be incorporated into a single die.

What is the difference between a hollow, semi-hollow and solid shape?

Hollow, semi-hollow and solid are the three general categories of extruded shapes. A shape is described as hollow if a completely enclosed void exists anywhere in its cross-section. In a semi-hollow shape, a void is only partially enclosed. A solid shape is one which is neither hollow nor semi-hollow.

What are some of the considerations that impact cost?

Several factors can influence the actual tooling cost for a specific shape. To minimize cost and maximize production, the practice is to build as much functionality into the die as possible. Actual tooling costs are driven by press size, part weight per foot, difficulty of shape, number of holes and the need for a backer and/or bolster.

For long production runs, it is advisable to either use two dies to complete the order or run the job in stages. Sometimes a two-piece extrusion may dramatically reduce the cost of secondary fabrication. Also, the smaller of the two extrusion pieces may be less costly to produce, both in terms of metal and tooling costs.

How does one decide on the number of holes to be built in a die?

The number of holes is determined by the circle size and the weight per foot of the profile (which determines the maximum run out per billet).
Other key factors are:

• Exposed areas of profile
• Length the profile will be ordered in
• Surface finish: mill, paint, or anodize
• Alloy
• End use of profile

What are backers and bolsters and why are they important?

Each die must have a backer and bolster for support, otherwise breakage will occur. Backers and bolsters are back-up support tooling for the die — normally three to four inches thicker than the die for the backer, and 10 to 14 inches thicker for the bolster. The same configuration as the die is cut into the backer and bolster, only much larger to allow the extruded shape to pass through them. A normal die package typically includes a die and a backer. In some cases, a bolster may need to be purchased. There are times when standard house backers and bolsters can be used, depending on the size, configuration, wall thickness and tolerance of the profile.

What tolerances are routinely produced?

Aluminum extrusions are manufactured routinely to the close-dimensional tolerances required for parts that must fit snug with other parts. Cost is minimized when an extruded product is designed to function at standardized production tolerances as defined by the Aluminum Association or other standard tolerance tables. However, tighter, custom tolerances can be specified, when necessary, and are maintained by an ongoing commitment to quality. You should confirm specific tolerance requirements with your die engineer.

How is a die run?

Each die is initially inspected for cracks and die lines before polishing. Once polished, the die is assembled with proper support tooling before being placed in the die oven for preheating. Preheating temperatures range from 800 to 900 degrees F, depending on the type of die (solid, hollow, etc.). Once the test sample is run on a new shape, the die is nitrided, which hardens the surface of the die up to .007 inches deep.

The manufacturing process control card and print for each die is signed off by a die corrector and sent to the press. In turn, the die is released for production.

How “unique” can my designs be using aluminum extrusions?

Aluminum extrusions offer designers unrivaled freedom from “standard” shape restrictions, unavailable with any other material.