Metal Casting Flashcards
Manufacturing Processes
What does the sand-casting manufacturing method produce?
POTENTIALLY NOT IN EXAM BUT GOOD TO LEARN
Forms high melting point metals into components.
Bollards
Heavy duty park benches
Post boxes
Train carriage wheels
Drain covers
Etc.
What production method does sand casting used and where does it happen?
POTENTIALLY NOT IN EXAM BUT GOOD TO LEARN
Typically, one-off or batch production. Never continuous/mass production.
Its slow and labour intensive.
Often carried out in specialist factories called foundries.
Uses moulds made from sand which are only single use.
What sort of finish is given to sand casted products?
POTENTIALLY NOT IN EXAM BUT GOOD TO LEARN
Not at all high-quality as the molten metal picks up the grainy texture of the sand.
Explain the sand-casting process (simply).
POTENTIALLY NOT IN EXAM BUT GOOD TO LEARN
- A pattern (replica of item to be cast) is made and divided into 2 halves. Its placed on the bottom of a steel box (drag) which is tightly packed with sand.
- Drag is turned over and a cope (second box) is clamped over the top, so the patterns line up. Wooden stakes are placed in the cope to later form the sprue and riser. Sand is packed into the cope and a small depression is made around the sprue for a pouring basin.
- Cope/drag are disassembled, connecting channels are cut to join the sprue to the pattern and then to the riser, cope/drag reassembled. Vent holes can be made to allow gases from casting to escape.
- Molten metal is poured into the basin. Flows into cavity and when flows up the riser it indicates the cavity is full.
- Once cool, the sand is removed. The sprue, riser and channels are cut using a hacksaw and the casting is ready for machining.
What products are die casted?
Moulds lower melting point metals, like aluminium and zinc-based alloys.
Alloy wheels
Toy cars
Collectible figures
Doorknobs
Handles
All have a high-quality surface finish.
What production method produces die-casted products? Why?
Very large batch and mass production.
Because it uses reusable tool steel moulds which are very expensive and complex to make.
What are the two types of die casting?
Gravity Die Casting
Pressure Die Casting
-Hot chamber
-Cold chamber
What sort of parts does Gravity Die Casting produce?
Makes parts that have a thicker and heavier section than pressure die casting, but a thinner section than sand casting.
In the middle.
It’s the simplest form of die casting.
What products are made using Gravity Die Casting?
Intricate parts for devices, such as phones and laptops.
Housings (casings for parts)
LED housing
Spoons, pots, etc.
What is the difference between Hot and Cold Chamber Die Casting?
How the molten metal is fed into the die.
Hot Chamber
Metal is heated directly in the casting machine (built-in furnace). Best for metals with a low melting point: zinc, lead or tin.
Cold Chamber
Metal is melted in a separate furnace and ladled into the die. Best for metals with high melting point; aluminium, copper, brass alloys.
Why is Cold Chamber Die Casting used to cast aluminium?
The aluminium would pick up iron from the steel chamber in hot chamber die casting.
What polymer process is like the Die Casting process?
Forming polymers using Injection Moulding.
What is the other name for Investment Casting?
Lost-Wax Casting.
What are some examples of Investment Casted products?
Used to cast intricate/awkward shapes.
Collectable figures
Jewellery
Medical applications e.g. hip replacement joints.
What metals are used in Investment Casting?
Stainless steel, brass, aluminium and carbon steel.
Wide range of metals are suitable.
Excellent finish and allows for repeatability because the wax patterns are cast from a master mould.
Explain the Investment Casting process.
If several items are to be cast, wax patterns may be joined together in a ‘tree’.
1. The wax pattern is dip coated with a refractory clay which is fired in a kiln. The wax burns away, leaving a hollow clay mould.
2. The molten metal is poured into the clay mould, and it’s allowed to cool.
3. The clay mould is then broken away, revealing the casting inside.
4. The runner and channels are machined off.
What is Pewter?
An alloy with a low melting point.
Usually an alloy of tin and copper (sometimes silver).
What products are produced using Low Temperature Pewter Casting?
Ideal for making small scale items.
Jewellery
Key fobs
Decorative components
Often used in school/college projects and commercial crafts.
What production method does Pewter Casting use?
It depends on the material of the moulds.
Its easy to make moulds from a range of materials, so its suitable for one-off production.
Therefore, moulds can also be made from aluminium and steel which have a higher melting point than pewter, so can be reused.
This would enable it to be done on a large scale.
What is the process of Low Temperature Pewter Casting?
This is for one off production…
1. A mould is made (of MDF/Plywood/Modelling Foam) which includes a sprue.
2. The mould is clamped together (leaving the sprue to pour the metal into).
3. The pewter is melted in a ladle and poured into the sprue. Once cooled its removed.
4. The sprue is removed with a hacksaw.
5. The casting is filed and polished to finish.
What does the diagram for Pewter Casting look like?
Google it.
