Die Casting Cycle Time and Cost Per Part

The Cycle Time Components

A die casting cycle includes ladle or pour, shot, intensification and dwell, die open, part extraction, die spray and blow-off, die close and clamp. Fill time is a fraction of a second; solidification and cooling usually dominate. Cold chamber machines used for aluminum and magnesium have a longer pour and shot sequence than hot chamber zinc machines, which are typically faster.

Part thickness, die temperature control, alloy and spray practice all push cycle time. Automation matters too: robot extraction, in-die trim and automated spray can tighten cycle and reduce variation, but they add capital and maintenance cost.

• Cooling time is set by wall thickness and die thermal design
• Spray and blow-off time depends on die complexity and automation
• Cold chamber cycles are generally longer than hot chamber
• In-cycle waiting on operators or robots shows up as lost shots

From Cycle Time to Cost Per Part

Start with machine hourly rate, which should include depreciation, maintenance, energy, floor space, labor allocation and furnace cost. Divide shots per hour by one over cycle time, multiply by cavity count to get parts per hour at 100 percent, then apply realistic uptime and yield. Add metal cost for the full shot weight including runner, biscuit and overflows, less recovered value if remelted at your cost basis.

Add trim press time, deburr, machining, impregnation, finishing and packaging. Tooling is then amortized separately. The result is a defensible cost that shows exactly which line a pricing negotiation will touch.

Realized Versus Quoted Cycle Time

Quotes often use the engineered cycle at best conditions. Actual output reflects die changes, warm-up shots, setup scrap, downtime for die maintenance, shot sleeve and plunger tip issues, and the lag from slower shifts. Compare quoted parts per hour against actual good parts per hour over a month by machine and die.

The ratio is effectively an OEE for the part. If realized output runs 20 to 30 percent below quote on a family of parts, the issue is not your estimator, it is that the machine rate you are charging does not match the machine you run.

• Track shots and good parts by die and machine, not just by job
• Separate planned changeover from unplanned downtime
• Include warm-up and first-article shots in scrap
• Review realized rate by part family monthly

Picking the Right Machine Tonnage

Quoting on the wrong machine skews cost. Clamping tonnage must hold the die against injection pressure across the projected area, with margin. A part quoted on a 800 ton machine that actually runs on a 1,000 ton machine carries a higher hourly rate.

Conversely, forcing a part onto a smaller machine to save rate can raise flash and scrap. Keep a machine capability table with tonnage, shot size, platen size and automation, and let the quote tool pick the intended machine. Check that the scheduled machine matches the quoted machine; if not, flag the cost difference.

When Detailed Cycle Costing Is Not Worth It

For low-volume parts with high secondary machining content, die casting cycle precision matters less than machining cost, and a simpler rate-based estimate may be enough. The detailed model pays off when you run high volumes on dedicated cells, where a few cents per part multiplies into real money. If you do not yet capture shots and good parts per die, start there before building a sophisticated model on assumptions.