Stamping cost drivers and how to negotiate them

The cost stack behind a stamped part

A stamped part price is built from a small number of lines: material, conversion, tooling amortisation, finish, scrap recovery and overhead. The split between them changes with the part, the volume and the region, but the structure is stable.

A buyer who asks for a lower piece price without knowing the split is asking the supplier to choose which line to cut. That usually means a cut in margin, a cut in inspection or a cut that will be recovered later through a change note. A should-cost model gives the conversation a structure.

The numbers below are illustrative, not a quote. They show the shape of a cost stack for a mid-volume stamped part so that a buyer can see which lines are worth challenging.

Material and scrap

Material is usually the largest line, and it is set by the blank size, the strip width, the gauge and the alloy. The blank size is decided by the part outline plus the carrier and the edge allowance. A small change in the nesting can remove a strip width or a station, and that change compounds across the volume.

Scrap is part of the material line. The skeleton left after the part is punched has value, but only if it is clean and sorted. A mixed strip with a plating or a coating may be worth less. Ask how the supplier accounts for scrap: is it credited at the purchase price, at a recovery rate or not at all?

The gauge is the other lever. A part designed at a non-standard thickness may need a special coil order, a longer lead time and a higher price. Moving to a standard gauge can save more than a small negotiation on the piece price, provided the function allows it.

Alloy choice matters as well. Copper, brass and stainless steel move with different markets. If the part can use a lower-cost alloy without losing conductivity or spring, that is a design decision with a direct cost effect.

Tooling and amortisation

Tooling is a fixed cost. It should be quoted as a separate line with the number of stations, the expected life and the maintenance assumption. When tooling is folded into the piece price, the buyer cannot tell whether the amortisation is spread over the quoted volume or over a volume the supplier hopes to see.

The number of stations drives both the tool cost and the press time. Every station adds a punch, a die block, a spring and a maintenance point. A design change that combines two features into one station can reduce the tool cost and the cycle time at the same time.

Tool life and maintenance belong in the negotiation. A cheaper tool with a short life may cost more over a three-year programme. Ask for the expected strokes between maintenance, the spare parts list and the ownership terms. If the tool is paid for by the buyer, the ownership and transfer terms should be in writing.

Press time and cycle time

Conversion cost is the press rate multiplied by the cycle time, plus the setup and the handling. The cycle time depends on the stroke rate and the number of strokes per part. A progressive die makes one part per stroke, so the cycle time is close to the press stroke time plus the feed.

The press rate depends on the tonnage and the size of the machine. A large press with a long bed costs more per hour than a small high-speed press. A part that needs a large bed for a small feature may be paying for capacity it does not use.

Setup time matters at low volume and almost disappears at high volume. If the annual volume is a few thousand parts, the number of setups per year can be a larger cost than the press time. That is the point where a different process, such as laser cutting or a compound die, may be cheaper.

Finish and secondary operations

Plating, coating, deburring, tapping, welding and assembly are secondary operations with their own handling cost. They are often quoted as a per-piece adder, but the handling between operations can be the larger part of the cost on a small part.

Pre-plated coil can remove a plating step and a handling step, but it puts the coating through the die. If the coating survives the bend and the shear, the saving is real. If it cracks, the rework or the reject cost can exceed the saving.

Deburring is a good example of a hidden cost. A part that needs a manual deburr has a labour line that scales with volume and a quality risk that scales with the operator. A design change that moves the burr to a non-critical face can remove the operation.

An illustrative cost split

The table gives a structure for a should-cost review. Replace the illustrative shares with the values from the supplier quote and the buyer's own model, then challenge the lines that differ.

Negotiation moves that hold

The most durable saving is a design change. Remove a station, widen a tolerance that does not affect function, move a hole away from a bend or change a finish to one that is easier to apply. Each of those reduces cost for the supplier as well as the buyer, which makes the saving stable.

The second is a volume commitment. Tooling amortisation and setup cost fall per piece as the volume rises. A commitment in exchange for a price break is a normal trade, provided the buyer understands the inventory and liability that come with it.

The third is a change in the commercial structure. Separate the tooling from the piece price, agree a scrap credit, index the metal price or fix the currency for a period. These do not change the part, but they remove risk from the quote and can lower the price without cutting quality.

What does not hold is a demand for a lower price with no change in scope. The supplier either accepts a lower margin, which is not sustainable, or reduces something the buyer cannot see. A should-cost conversation is more useful than a percentage target.

What not to squeeze

Inspection, maintenance and material certification are the three lines that are easy to cut and expensive to lose. A quote that is low because it assumes no first article, no gauge study and no tool maintenance is not a lower cost; it is a transfer of risk to the buyer.

The same applies to packaging. A cheap pack that allows parts to rub in transit produces rejects at the customer, and the cost of sorting them is usually higher than the saving on the carton.

A good negotiation ends with a price that the supplier can hold and a scope that the buyer can audit. If the price is below the material and conversion cost in the should-cost model, the difference will appear somewhere else in the programme.