What Drives the Cost of a Zamak Bezel Ring?

Four lines carry the price of a bezel ring: tooling amortisation, casting and trim, polish and turning, plating and trial fit. The 4.5 g of Zamak 5 in the ring is the smallest of them, which is why a quote built on weight is wrong by a wide margin.

The ring is cast to ASTM B86 AC41A and finished on post-machining and plating lines, so each line follows a different driver. Comparing two quotes line by line is possible only when both suppliers break the price the same way.

Which steps does a bezel-ring quote contain?

Eleven process steps sit behind the four lines: die casting, gate removal, tumbling, polishing, CNC turning of the bore, step and outer diameter, degreasing and activation, copper, nickel, chrome and drying, then inspection.

The steps group unevenly. Casting and gate removal scale with shots. Tumbling and polishing scale with surface area and handling, turning with setups, and plating with rack density and layer count.

A quote that lists only casting and plating is missing the two steps that change most between suppliers: the turning setup that holds the 0.05 mm roundness and the polishing pass that precedes it.

Why does plating cost more than its 18–27 µm suggests?

Because the thickness is small but the handling is not. Three metals mean three baths, three rack loads and three chances to reject the part, and the ring is handled between each of them.

Rack density drives the price more than the layer thickness does. A ring takes rack space by its diameter, not by its weight, so the same rack holds fewer rings than it would hold small parts, and the cost per ring rises with the diameter.

Colour adds a third driver. A colour match to ΔE ≤1 needs a first article and a chip comparison, and a colour change reopens both. That work is quoted as a first article rather than as a line item on the plating price.

Where does the press-fit trial sit in the quote?

In its own line, next to plating. The trial uses the mating case and a force band of 200–600 N, and it is the only check that proves the coated ring still presses.

The trial is not a one-off cost at the start of a program. Every colour change, every plating thickness change and every new case lot reopens it, because the fit depends on the coating and on the case.

Suppliers who leave the trial out are not cheaper; they have moved the check to the customer's assembly line, where a failed press costs the ring and the labour around it.

Why does a small ring carry a large tooling share?

Because the tool is priced by cavities and life, not by part size. This ring runs in a six-cavity tool built for 400,000 shots as a design target, and the tool cost is divided across that shot count.

A small ring spreads the tool over more parts per shot, which helps, but the tool itself is not cheaper for being small. The six cavities, the 8407 inserts and the ring gate cost what they cost.

The share per ring therefore falls with the order quantity and rises with every engineering change made after the tool is cut. A wall change, a gate change or a cavity change is a tool change, and it resets the amortisation.

How does quantity change the per-piece price?

Quantity moves the tooling line and leaves the other three roughly flat. Doubling the order halves the tooling share per ring; it does not halve the casting, polishing or plating time.

Three inputs belong in the enquiry beside the quantity: the number of colours, the number of trial fits, and the drawing revision. Each one adds a first article or a setup that the piece price cannot absorb.

A supplier who quotes from weight will be low on a heavy ring and high on a light one; a supplier who quotes from the four lines will be comparable. Send the drawing with the colour count and the trial requirement, and the quote can be compared line by line.

The turning setup and the polishing pass are where two quotes usually diverge, so ask for those two lines by name before comparing totals.