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Die Casting Presentation

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L G

on 28 November 2013

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Transcript of Die Casting Presentation

Injection
Very high pressure, from 10-100MPa

Method depends on machine type

Constant temperature

Time taken is typically less than 0.1 seconds
Cooling
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
Cold Chamber
Preparation
Cleaning
Lubrication
Clamping
1
2
3
The Shakeout
The casting is shed of its excess material

Harvested scrap can be reused
Ejection
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
Cons:
Jargon Buster
Die Casting
The Process
Die casting is used to create metal shapes by forcing molten metal into a mould called a die.


The Die
1)
Preparation
of the die halves
2)
Injection
of the shot into the cavity
3)
Cooling
of the metal
4)
Ejection
of metal from the die cavity
5)
The Shakeout
, the trimming of excess metal from the casting
Pros:
Loic Gueganton and Fergus Shaw
What is die casting?
The Shot
The Casting
Very high start up cost
Slight porosity is common
Compatibility limited to select metals
Highly accurate
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
The runner is a channel in the die that delivers the molten metal to the cavities between the dies.
The
Five Steps
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.
Semi-solid -
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

Ability to
repeat castings accurately and quickly
is excellent. This helps counter the very high start-up costs.

However, defects can occur, manifested most commonly as
misruns
and
cold shuts
, but issues with
porosity
,
inclusions
, and
hot spots
, can also cause weaknesses and imperfections in the casting.
Comparisons with other processes
In summary...
Hence it is the most productive casting process
Hot Chamber
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
isolated
, and is ladled into the shot chamber for each new casting.

Injection system usually orientated
horizontally
.

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.
Material Compatibility
Difficult for ferrous metals to be die cast

Aluminium and copper alloys can only be cold chamber die cast
Typical Shapes and Applications
Misruns
Occurs when the molten metal does not completely fill the die cavity, leaving gaps
Cold Shuts
Occur when two fronts of liquid metal do not fuse correctly in the cavity
Porosity
Gas porosity is the formation of bubbles in the casting when the molten metal cools
Inclusions
An inclusion is an inpurity contained in the casting, coming from eroded material in the furnace or ladle linings
Hot Spots
Hot spots are areas on the metal surface that cooled faster than other areas, making them much harder than the surrounding material
Electronics
Plumbing
Aerospace
Medicine
Dental Equipment
Connector Housing
Aluminium Pipe Parts
Networking
Modem
Toys

Transportation
Full transcript