16 - Metal processes Flashcards
What are the three types of metal processing?
- Forming
- Redistributing
- Wastage
Press forming
-forming
Used to form sheet metal into 3D forms
-Metal sheet placed over hydraulic die
-Hydraulic press lowered to push the sheet into the shape of the die
-Hydraulic die then lowers to remove the formed metal
Suitable for mass production and large-scale batch production
Spinning
-forming
Used to form sheet matal into rounded objects, e.g a kettle
-Sheet metal is spun while rollers push and shape the sheet metal to form the shape of the mandrel
Mass production or small-batch production
Cupping and deep drawing
-forming
Uses metal blank stock form
-Metal blank is held over a cavity and pushed down by a deep drawing punch to form the shape
-Forms tube shaped objects, e.g a fire extinguisher
Large-scale mass or continuous production
Drop forging
-forming
Lower die on anvil, upper die on Ram.
-Heated metal billet placed on the lower die, then pressed in to shape by the upper die and cooled
-It is heated to just above recrystalisation temperature
Makes products which need to be tough and hard, e.g a spanner
-Suitable for mass production
Wrough iron forging
-forming
Metal is heated then hammered, bent, rolled into desired shape on an anvil
-Uses wrough iron (carbon with a carbon content of <0.08%
-Bar stock form
Suitable for one-off or small-batch production
Bending
-forming
-Sheet metal placed over a V-shaped die
-Punch is then lowered, pushing the metal into the V-shape to form an edge
Used for large-scale batches in industry
Rolling
-forming
Thicker metal (billets)
-goes through rollers which compast and thin out the metal
-can be hot rolling (no deformations or stresses) or cold rolling (tighter tolerance, better finish)
Sand casting
-redistribution
Mould created in sand
-molten metal is poured into the mould and left to cool
-used for metals with high melting points
Labour intensive, doesn’t produce a high quality finish
Suitable for one-off or small-batch production
Die-casting
-redistribution
Molten metal from a billet is poured into a die
-usually relies on gravity for the molten metal to take the dies shape
-used for metals with lower melting points, e.g aluminium
Often used to make door knobs
Very large-batch and mass production
Investment casting
-redistribution
Exact replica model is made with wax
-model submerged in refectory clay, placed in kiln
-wax is melted, leaving a perfect mould in the clay
-molten metal then poured into the mould and left to cool
Used for intricate designs, e.g jewellery
It is repeatable, as the wax model is made from a master mould
Low temperature pewter casting
-redistribution
Two-piece model made from MDF
-molten pewter poured in to the mould and left to cool
-mould can then be split into its two halves to release the formed metal
Mostly used in school projects
Can be one-off production
Used to make small decorative items
