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Die Casting Presentation
Transcript of Die Casting Presentation
Very high pressure, from 10-100MPa
Method depends on machine type
Time taken is typically less than 0.1 seconds
In a hot chamber machine, the metal is melted down in situ, and the shot chamber is submerged in it.
Hot chamber is the preferred method, however it is only compatible with some metals.
Pressure of between 5 and 30 MPa.
Cooling usually takes between 2-5 seconds
More complex shapes require longer due to the slowing down of the flow of heat
Time taken depends on the size of the cavity and the wall thickness
The casting is shed of its excess material
Harvested scrap can be reused
After cooling time has expired, die halves are opened
Pins in the ejector die push the casting to free fall out of the die
This smooth ejection is made possible by the lubricant of water and oil, and this is resprayed on the inside of the dies after ejection
Die casting is used to create metal shapes by forcing molten metal into a mould called a die.
of the die halves
of the shot into the cavity
of the metal
of metal from the die cavity
, the trimming of excess metal from the casting
Loic Gueganton and Fergus Shaw
What is die casting?
Very high start up cost
Slight porosity is common
Compatibility limited to select metals
Wide variety of shapes
Fast. Like, REALLY fast.
High quality surface finish
Inserts can be included
Little or no post-machining needed
Low-fluidity metals can be cast
Castings have very favourable material properties
Two blocks of tool steel with a shape cut out of each, pressed together to form a cavity in the middle.
This refers to the amount of molten metal that is injected into the cavity between the two dies, including the runner.
The casting is the final product created by the process.
The runner is a channel in the die that delivers the molten metal to the cavities between the dies.
of Die Casting
Variants of the standard die casting process:
Pore free -
used when porosity has to be completely eliminated, the cavity is filled with oxygen instead of air before the injection step.
Heated-manifold direct-Injection -
used when a part can be cast multiple times in a single shot. Multiple nozzles lead from a heated manifold, injecting each cast individually.
The injected metal is in a state more solid than the molten metal used in traditional die casting. The consistency can be described as 'slushy'.
Accuracy and Repeatability
Highly dimensionally accurate
- can be as good as within 0.2% of casting dimension
repeat castings accurately and quickly
is excellent. This helps counter the very high start-up costs.
However, defects can occur, manifested most commonly as
, but issues with
, can also cause weaknesses and imperfections in the casting.
Comparisons with other processes
Hence it is the most productive casting process
Fast, accurate, efficient, repeatable, economic and versatile
Used for alloys with
high melting points
, e.g. aluminium, copper, and magnesium.
Main difference to hot chamber is that the molten metal supply is kept
, and is ladled into the shot chamber for each new casting.
Injection system usually orientated
Injection pressure of between 13 and 130MPa.
Pressure and cost separates die casting from similar casting processes i.e. sand casting and permanent mould casting.
Pressure entails better surface finish, dimensional accuracy, and less porosity.
High startup cost means die casting is only cost-effective for large scale production.
Difficult for ferrous metals to be die cast
Aluminium and copper alloys can only be cold chamber die cast
Typical Shapes and Applications
Occurs when the molten metal does not completely fill the die cavity, leaving gaps
Occur when two fronts of liquid metal do not fuse correctly in the cavity
Gas porosity is the formation of bubbles in the casting when the molten metal cools
An inclusion is an inpurity contained in the casting, coming from eroded material in the furnace or ladle linings
Hot spots are areas on the metal surface that cooled faster than other areas, making them much harder than the surrounding material
Aluminium Pipe Parts