The Die Casting Process -Technical Guide for Engineers and Buyers

The die casting process is a cyclic, high-pressure metal forming method that produces near-net-shape components from non-ferrous alloys. This guide covers the complete process in technical detail -from melt preparation through final inspection -with the process parameters that determine part quality.

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Process Overview

Each die casting cycle consists of six repeating phases:

1. Die close and clamp -Die halves close under hydraulic pressure equal to or greater than the injection force
2. Metal injection -Molten alloy injected into the cavity at controlled velocity
3. Intensification -Secondary pressure applied after cavity fills to suppress porosity
4. Solidification -Part cools under pressure until mechanically stable
5. Die open and ejection -Ejector pins push solidified part from cavity
6. Lubrication and reset -Die sprayed with release agent before next cycle

Total cycle time ranges from 15 seconds (small zinc parts) to 3- minutes (large aluminum structural components).

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Cold Chamber vs Hot Chamber Process

Cold Chamber Die Casting

Used for aluminum and magnesium alloys. The injection system is outside the melt furnace. Each cycle requires manually ladling or auto-ladling metal into the shot sleeve before injection.

Key parameters:

Parameter	Typical Range
Injection pressure	35-75 MPa
Gate velocity	20-30 m/s
Metal temperature	620-700°C (aluminum)
Die temperature	180-260°C
Cycle time	30-120 s

Hot Chamber Die Casting

Used for zinc alloys. The injection gooseneck is permanently submerged in the melt. Metal is automatically drawn and injected each cycle -faster and more consistent than cold chamber.

Key parameters:

Parameter	Typical Range
Injection pressure	7-15 MPa
Gate velocity	30-40 m/s
Metal temperature	400-430°C (Zamak)
Die temperature	150-220°C
Cycle time	15-25 s

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Critical Process Parameters and Their Effect on Quality

Parameter	Too Low	Too High	Optimal Effect
Injection velocity	Cold shuts, misruns	Turbulence, porosity	Complete fill, minimal gas entrapment
Metal temperature	Cold shuts, poor fill	Die soldering, porosity	Good fluidity without alloy degradation
Die temperature	Premature solidification, cold shuts	Soldering, long cycle	Balanced fill and solidification
Intensification pressure	Shrinkage porosity	Flash, die damage	Dense, pore-minimized structure
Clamping force	Flash at parting line	-	Tight die seal, no flash

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Melt Preparation and Alloy Control

Alloy quality directly determines casting soundness. KastMfg's melt preparation procedure includes:

• Chemistry verification -spectrometer analysis of each melt before casting
• Degassing -rotary degassing with nitrogen or argon to reduce dissolved hydrogen
• Temperature control -thermocouple monitoring, holding at ±10°C of target
• Slag removal -skimming before each ladle

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Vacuum-Assisted Die Casting (VADC)

For pressure-critical parts (hydraulic manifolds, sealed enclosures), KastMfg offers vacuum-assisted die casting. A vacuum system evacuates the die cavity immediately before injection, reducing trapped gas by 60-70%. Parts produced with VADC can be T6 heat treated without blistering and reliably pass pressure leak tests.

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Process Control and Monitoring

Every shot at KastMfg is monitored and logged:

• Injection velocity profile (slow shot + fast shot)
• Peak injection pressure and intensification pressure
• Die surface temperature (pyrometer, thermocouple)
• Cycle time

Statistical Process Control (SPC) charts are maintained for all critical process parameters and critical dimensions. Alarms trigger when parameters drift outside control limits.

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From Process to Part -What Determines Final Quality

The die casting process determines:

• Dimensional accuracy -function of die precision, thermal expansion, and process stability
• Internal soundness -function of injection velocity, pressure, and melt quality
• Surface finish -function of die surface quality, lubrication, and fill conditions
• Mechanical properties -function of alloy, solidification rate, and heat treatment

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KastMfg Manufacturing Co., Ltd. Email: yaoqingpu1983@gmail.com | Phone: +86 138 1403 4409 No.6, Rungu Road, Nanjing, China