30Sep

Tooling Guidelines for Aluminum Die Casting

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Quite often I receive requests to quote parts for die casting and the purchaser may or may not realize what is involved in designing and fabricating a mold that will produce a quality die cast part in high volume quantities.

I am also surprised when new customers have tooling to transfer from an existing source and they are not fully aware what type of tooling they have purchased from their current vendor.

For this reason I am presenting a brief overview of what a die cast mold is and how to approach the purchase of a new mold with a convenient checklist developed by the North American Die Casting Association. This checklist is a valuable tool to assist the purchaser and the die caster in making decisions in a concise manner during the product launch.

 The Process

The die casting die or mold is a closed vessel into which molten metal is injected under high pressure and temperature, then rapidly cooled until the solidified part is sufficiently rigid to permit ejection from the mold.

 Tooling

Dies, or die casting tooling, are made of alloy tool steels in at least two sections, the fixed half (cover half) and the moving half (ejector die half), to permit removal of the castings. The dies also may have moveable slides, cores or other sections to produce holes, threads and other desired shapes in the casting.

 Openings

A hole in the fixed die half allows for the molten metal to enter the die and fill the cavity. The ejector half usually contains the runners (passageways) and gates (inlets) that route molten metal to the cavity.  Dies also include locking pins to secure the two halves, ejector pins to help remove the cast part, and openings for coolant to help cool the mold and solidify the molten metal.

A very important accessory required to run any die cast mold is called a Shot Sleeve.  The Shot Sleeve is a hollow tube that is inserted into the hole in the fixed half of the mold when it is set in the die cast machine.  The Sleeve protrudes out from the die horizontally and there is a small opening in the top of the Sleeve where the molten metal is poured in preparation of the plunger injecting the metal into the mold.  The Shot Sleeve needs replacement at certain intervals and is very important to the process.  Quite often when molds are moved from a die caster, the Shot Sleeve is not sent with the mold which creates issues for the purchaser due to the lead time to fabricate a new Sleeve.

 Making the Mold

The two die halves run in a die casting machine that is operated at the required temperatures and pressures to produce a quality part to net-shape or near-net-shape customer specifications. When the die casting machine closes, the two die halves are locked and held together by the machine’s pressure.  The surface where the ejector and the fixed halves of the die meet and lock is referred to as the “die parting line”.  The total projected surface area of the part being cast, measured at the die parting line, governs the clamping force of the machine.

For longevity of operation in this environment the die casting die must be built from high-quality tool steel of exacting specifications, heat-treated to the required hardness and structure ( Guidelines from NADCA exist for this reason), with dimensions of the die and cavity machined to exacting specifications.

The customer’s product design requirements directly affect the size, type, features, and cost of the required tooling. The items involved in the tooling decision include the number of cavities, number of core or slide requirements, weight of the die, machining, finish requirements, polishing and plating to name just a few.

A convenient checklist of die construction considerations, intended for use in discussion with your custom die caster, appears here:

C-8-2-231x300C-8-1-232x300 

This Checklist can also be found on Premier’s website at:

http://diecasting.com/resource-center/purchasing-checklists/.

The team at Premier will be able to review any part designs and review the tooling required for your part based on items detailed in the above checklist.

Please forward your RFQ to Sales@diecasting.com

By Leonard Cordaro, President of Premier Die Casting Company

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