Low & High Pressure Diecasting : Choosing a Pressure Casting Process

In order to select the most appropriate alloy in which to cast a component, designers should first select the most appropriate casting method. This decision is usually based on the anticipated production volumes of the component. It can also be influenced by considerations of the required dimensional accuracy and surface finish.

Once the most appropriate process has been selected, designers should decide upon the alloy which has the mechanical and physical properties most appropriate to the particular application, whilst also considering whether the casting characteristics are appropriate to the chosen process.

The table below will assist you to choose the process most appropriate to your requirements, however it is often neccesary to obtain quotations for more than one process in order to decide which will be the most economic.

				Sand Casting	Gravity Die Casting	High Pressure Die Casting
Tolerances on Critical Dimensions		Up to 25mm Each Additional cm Across Parting Line Ad.		± 1mm ± 0.39mm ± 1mm	± 0.4mm ± 0.02mm ± 0.25mm	± 0.1mm ± 0.016mm ± 0.12mm
Minimum Taper		On Inside Walls On Outside Walls		2° 2°	1° 1°	1° 0.5°
Minimum Wall Thickness		On Small Castings On Large Castings		3mm 5mm	3mm 4mm	1mm 2mm
Minimum Size of Cored Hole				15mm	3mm	2mm
Ability to use Sand Cores				Yes	Yes	No
Surface Finish				Poor 6.5-12.5 m	Fair 4-10 m	Good 1.5 m
Alloys commonly used in this form	Aluminium Zinc Copper		LM5 LM6 LM9 LM16 LM24 LM25 LM27 LM31 ZA3 ZA8 ZA12 ZA27 LG2 PB2	· · · · · · · · ·	· · · · · · · · ·	· · · ·
Typical Production Quantities per annum				1-500	250-50000	2000-500000

The Choice of Process - Sand Casting, Gravity & High Pressure Die Casting