What Drives the Cost of a Zamak Bezel Retaining Ring?

A zinc die casting quote for a bezel retaining ring follows nine process steps, and most of the money sits in the tool, the claw trimming, the plating jig and the press-force check. The ring weighs 1.8±0.2 g, so metal is a small share. Each failure mode on the drawing adds a check to the quote.

A Ø26 × 2.0 mm ring in Zamak 5 to ASTM B86 AC41A carries a 0.8 mm wall and three claws at 120°, all design targets. Those callouts set the cavity count, the trim time and the plating rack space.

Which steps does a retaining-ring quote contain?

Nine steps run from the shot to the box: die casting, degating, tumble deburr, trim the inner claws, polish, degrease and activate, nickel plate, dry, inspect. Degating cuts the runner and overflow off. Each step adds a piece or a batch cost, and two quotes for one drawing can differ.

Casting and degating ride on the shot; trimming, polishing and plating run per piece. Two items exist only because of the claws: the trim that holds 1.2±0.05 mm height, and the press-force check at 80–200 N. Tumbling comes first, since a burr at the claw root changes the cut.

Why does an 8-cavity tool still cost per piece?

An eight-cavity tool at a 500,000-shot design target spreads its cost over the batch, not over the 1.8 g weight. A first order pays for the whole tool, so its share per ring runs higher than a repeat order's. The block is 8407, chosen for that shot count.

Cavity count also sets the casting side. Eight parts leave the die on a typical 15–25 s cycle, so press time per ring falls as cavities rise. Die cost per ring moves the other way, with the shots an order consumes.

Where does claw trimming sit in the price?

Claw trimming is priced as a separate line because it is a separate operation. The ring leaves the die with claw height near target but outside the 1.2±0.05 mm band, and claw trimming cuts each of the three claws into it. Deburring an edge and holding a height window are different jobs.

The 120° index at Ø0.1 mm adds a second reading. Trimming also sets the press: a claw left high lifts the crystal, a claw cut low lets it move. A change to claw height re-prices the trim, and its gauge belongs in the first-article report.

Why does plating a 1.8 g ring cost more than its weight?

Plating is priced by rack space and handling, not by the 1.8 g the ring weighs. A Ø26 mm ring takes a rack slot like any part, and the 0.8 mm wall plus the inner cavity need a jig that reaches faces the anode cannot see. Shielding that cavity is handling time before the tank.

The finish spec sets the rest. Nickel at 3–5 µm is one pass, while a Cu 8–12, Ni 5–8 and Cr 0.1–0.3 µm stack is three at 13.1–20.3 µm total. The inner cavity plates thinner than the outer band, so coverage is read on an X-ray at 3 µm or more. Each layer and each X-ray is a priced step.

What has to be quoted besides the piece price?

Tooling amortization, first-article inspection and the test list belong beside the piece price, not inside it. First-article inspection checks the first parts off the tool. The drawing supplies the inputs: Ø26.0 0/-0.05 mm outer diameter, 0.8±0.05 mm wall, 1.2±0.05 mm claw height, 0.05 mm flatness and 1.8±0.2 g weight.

The test list carries the omitted cost. A press-force bench checks the 80–200 N window, an X-ray film reading holds the 3 µm floor, an ASTM B571 thermal-shock check follows, and an ASTM B117 96 h salt-spray run closes the release. A quote that returns one price leaves those lines for the first invoice.

Send the drawing with the claw height, the finish stack and the test list marked, plus the batch the tool will run. Those inputs let a second supplier price the part on the same basis.