Manufacturing Processes - Squeeze Casting Process
Squeeze Casting Manufacturing Process
Squeeze Casting
Squeeze casting fits in the general category of casting as a manufacturing process. Casting has been around for approximately 6000 years, so squeeze casting is a relatively new development; being introduced along with other pressurized casting techniques during the mid 1800's.
The squeeze casting process uses an accurately measured or metered quantity of molten metal which is poured into a heated mould via a launder. The mould is closed to produce an internal cavity in the shape of the required component.
The molten metal is forced/displaced into the available space of the die cavity. As with most casting processes, using a permanent pattern, the mould is coated with a suitable release agent and for squeeze casting it is usually in the form of a graphite coating.
Pressure continues to be applied to the molten metal until it has solidified and forms the required component. The press is then withdrawn and the component is ejected.
Squeeze casting is most suited to the production of light alloy components in large production quantities. Retractable and disposable cores can be used to create complex internal features.
Pros
- Offers a broader range of shapes and components than other manufacturing methods
- Little or no machining required post casting process
- Low levels of porosity
- Good surface texture
- Fine micro-structures with higher strength components
- No waste material, 100% utilization
Cons
- Costs are very high due to complex tooling
- No flexibility as tooling is dedicated to specific components
- Process needs to be accurately controlled which slows the cycle time down and increases process costs.
- High costs mean high production volumes are necessary to justify equipment investment
Light alloy castings can be produced in complex 3D shapes using the squeeze casting process and are stronger than plastic equivalents.
Squeeze Casting Machine
Manufacturing Processes - Compression Moulding
There are many similarities between squeeze casting and compression moulding, the obvious difference being that compression moulding is used primarily for the production of plastic components. It is widely used for thermo-setting plastics but can also be used for some thermo-plastic plastics or composites.
It is a closed permanent mould process that fits under the general manufacturing process of casting, much the same as squeeze casting. Heating of the charge will initiate softening or a chemical reaction that allows the material to be displaced.
A charge of preheated plastic material is placed inside a heated die. A punch is then brought down to compress the plastic and displace it into the mould cavity. Once set the punch is removed and the component ejected, usually after it has been allowed to cool.
Pros
- Tooling and machine costs relatively low compared to other permanent mould casting processes.
- Very little waste material, but with thermosetting plastics it cannot be recycled.
- Mould changing is fast
Cons
- Limited to simple shapes due to short flow lengths of plastic
- Process uses dedicated tooling
- Operator dependent
- Can be affected by premature chemical reaction, air entrapment and failure to fill the cavity resulting in reject components
- May require re-entrant angles for some materials i.e. plastics which are flexible at demoulding temperatures.
Squeeze Casting - Additional Resources
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