Permanent Mold Tooling: Cost, Life, and Refurbishment

The die is the biggest decision in permanent mold casting. It is the line item that makes buyers hesitate, the reason the per-part price falls, and the asset that keeps producing years after the first purchase order. Here is what goes into one, what it costs, why it lasts as long as it does, what refurbishment means, and who cuts it.

What a permanent mold die is

A permanent mold is two or more steel blocks machined so that, when closed, they form the cavity of the part along with the gating and risers that feed it. Cores for holes and pockets are steel where the geometry allows a straight pull, and sand where it does not. The die mounts in a machine that clamps it shut, tilts it for the pour, opens it, and ejects the casting. Between shots the die is coated with a refractory mold wash that controls how fast heat leaves the metal and protects the steel from the aluminum.

Most of the cost is machining time in hardened steel. Aluminum cuts fast; a steel block hard enough to survive tens of thousands of shots cuts slowly, and the cavity, gating, vents, ejector pin holes, cooling, and core pulls all come out of it. A single-cavity die for a small bracket is a modest tool. A multi-cavity die for a large housing with slides and several sand cores is not.

A low pressure permanent mold die with a slide, cut in the Protocast tool room. Slides and cores are what move a die from the low end of the cost range toward the high end.

What a die costs

Protocast publishes ranges because buyers need them to plan. Small parts with simple geometry start around $35,000 to $40,000. A permanent mold rarely comes in below that, because the steel itself is expensive and it has to be hardened to last. Large parts with moving slides for undercuts and multiple cores can reach $200,000. Most of the tools that cross the sales desk are under $100,000, so the middle of that range is where a typical housing or bracket lands.

Ranges from Protocast. Every quote is built from the part.

For comparison, a precision sand pattern for the same part might be about $10,000. The trade is in the piece price: a sand casting that costs $250 to $300 each can come down to a fraction of that in permanent mold once the die is paid for, which is why the sand versus permanent mold guide puts the crossover at only a few hundred pieces a year.

Why it lasts about 40,000 shots

Aluminum is poured at roughly 1,250 to 1,450 degrees Fahrenheit. Every shot heats the cavity surface and every ejection lets it cool, so the steel cycles thermally thousands of times. Eventually fine heat-check cracks appear at the surface, edges and gate areas wear, and dimensions drift. Protocast’s rule of thumb is about 40,000 shots before refurbishment. The die does not have to be replaced at that point; it comes off the machine for attention and goes back to work. Several things move that number:

• Mold wash and preheat discipline. A die that is preheated properly and coated consistently sees less thermal shock and lasts longer.
• Part geometry. Sharp inside corners and thin steel sections between cavity features are where heat checking starts. Generous radii in the part design protect the die as much as they protect the casting.
• Alloy. The aluminum casting alloys Protocast pours, 356 and 357 among them, are kind to tooling compared with some higher-copper or higher-iron alloys.
• Run length. Long continuous runs at a stable temperature wear a die more slowly than frequent short runs that cycle it hot and cold.

What refurbishment involves

Refurbishment is not a new die. It is welding and re-machining worn areas, polishing heat-checked surfaces, replacing ejector pins and core pins, and re-qualifying the first castings against the drawing. The work is a fraction of the original tooling cost and, done at the right time, returns the die to full production for another long run. The same tool room that cut the die handles it.

Who cuts the die

Permanent mold dies are cut in Protocast’s own tool room whenever possible, on the same group of eight CNC machines that handle post-cast machining. Domestic tooling partners are still used when the shop is at capacity or when a particular design is one the tool room would rather not take on, so the answer to “who cuts it” is Protocast first, a domestic partner when needed. Three practical points follow from that.

• Engineering changes. A die cut in the building can be revised in days, with the toolmaker and the foundry in the same conversation.
• Tryout. First shots, gating adjustments, and requalification happen where the die was made.
• The die stays put. The customer owns it, Protocast stores and maintains it, and it never travels between runs.

Customer-owned dies between runs. They are stored, maintained, and refurbished at the foundry.

Who owns the die

The customer does. The purchase order for tooling buys the die outright, and it stays at the foundry for production. Ask for the ownership terms in writing with the quote; they are standard, and having them on paper matters on a multi-year program.

How to think about the cost

Divide the die cost by the volume you expect it to produce. A die good for 40,000 shots before refurbishment on a program running 5,000 pieces a year covers eight years of production, and the tooling contribution per part is small. The same die for a one-time run of 200 pieces is expensive per part, and that is the case where sand casting or printed sand is the better answer. The sand versus permanent mold guide shows where the crossover usually sits.

What is inside a permanent mold die

Tooling questions to settle before the quote

• Cavity count. One cavity is the simplest die. Two or four cavities cut the per-shot cost on small parts but raise die cost and require a balanced gating design.
• Cast-in inserts. Steel or bronze inserts can be placed in the die and cast into the part, for wear surfaces or threads. They add handling per shot.
• Identification. Part numbers, cavity numbers, date wheels, and logos can be cut into the die and appear on every casting.
• Family tooling. Related parts can sometimes share a die base with interchangeable inserts, which spreads the cost across a product line.
• Machining fixtures. Designed alongside the die so the datum surfaces cast cleanly and locate reliably.

Caring for a die between runs

A permanent mold die at rest is cleaned of coating residue, inspected for heat checking and wear, lightly oiled, and stored on site. Before the next run it is preheated on a schedule, recoated, and the first shots are checked against the last qualified samples. This routine, more than anything else, is what carries a die to and past the 40,000-shot mark, and it is one reason to keep the die where the parts are made.

How Protocast fits in

Protocast has cut its own tooling since 2005, first patterns and matchplates, and later permanent mold dies as well. Eight CNC machines cut permanent mold tooling and machine castings; three more are kept for sand pattern tooling only, because the pattern board throws dust that would contaminate the coolant on the machines that cut steel. When a program is ready to move from sand to permanent mold, the engineers who reviewed the prototype design the die.

Frequently asked questions about permanent mold tooling