Metal Processes Flashcards
Forming
Processes in which no material is removed, but materials are deformed to produce required shapes
Redistribution
Processes where the material is changed from one form to another without loss of material e.g. Liquid metal poured into a mould to take a solid form
Wastage
Processes that involve the removal of material to leave the desired shape
Press forming
Using a punch/male die (made from die steel) to shape sheet metals into 3D forms
Material needs to be ductile
Increases hardness, stiffness and structural strength of the material
Forming
Suitable for mass-production or large scale batch production
Products:
Metal seats
Car body panels
Radiator panels
Spinning
Used to produce 3D curved forms from sheet metal
A rotating mandrel is forced into the sheet metal shaping it
Forming
Suitable for mass production or small scale production
Used for:
Body of stainless steel kettles
Saucepans
Metal light shades
Cupping and deep drawing
A deep drawing punch is used to stretch the metal press blank into shape
Forming
High initial tooling cost
Used for large scale mass or continuous production
Products:
Fire extinguishers
Aerosol cans
Drinks cans
Drop forging
Hot metal billet is shaped on an anvil or die and then pressed into shape and cooled
Forming
Used for products that need to be hard and tough
Maintains the integral grain structure hence retains strength
Suitable for mass production
Used for screwdrivers, pliers and screwdriver shafts
Wrought iron forging
Uses wrought iron (carbon content less than 0.08%)
Forming
Can be hand or hydraulic press process
Suitable for one off or small batch production
Used for decorative metalwork such as gate scrolls and decorative fences
Bending
Using a punch and die to bend the metal to the desired angle
Forming
Can be carried out in a school workshop
Used for large scale batches in industry
Rolling
Used to make a billet thinner and of uniform thickness
Hot rolling - uniform mechanical properties, no deformation or stresses. Carbon deposits on the surface must be removed
Cold rolling - tighter tolerance and better surface finish
Hot rolling - l beams, angle bar, plate and channel and railway tracks
Cold rolling - filing cabinets, chairs, steel drums and containers
Sand casting
Mould is constructed in two halves made out specially treated sand
Redistribution
Halves are put together and runners, risers and vents are added to the top half
Labour intensive process
Not a high-quality surface finish
Suitable for one off or small batch production
Uses:
Railway carriage wheels
Wood working clamps
Vices
Gravity die casting
Molten metal is poured into a two part metal mould using gravity to help the metal flow into the mould
Redistribution
Used for metals with lower melting points - aluminium, aluminium alloys and zinc based alloys
Used for thicker mould sections
Used for large batch and mass production
Products:
Alloy wheels
Engine components
Door knobs and handles
Hot chamber Pressure die casting
A plunger is used to force a shot of molten metal from the chamber up the gooseneck into the die
Redistribution
Fast process used for very large batch and mass production
Used for lower melting point alloys - aluminium, aluminium and zinc alloys
Products:
Toy cars
Collectible figures
Decorative door knobs and handles
Cold chamber pressure die casting
Molten metal ladled into the shot chamber and hydraulically pushed into the die
Redistribution
Used for lower melting point metals - aluminium, aluminium and zinc bases alloys
Investment casting (lost wax casting)
Wax mould is baked in ceramic, molten metal is poured in burning away the wax. The ceramic coating is then smashed open to leave the solid metal
Used for intricate and awkward shapes - difficult or impossible for another casting method
High quality finish and repeatable - wax patterns are cast from a master mould
Products:
Cast jewellery
Collectable figures
Hip replacement joints
Low temperature pewter casting
Molten pewter is poured into simple MDF moulds
Uses for school or college projects
Suitable for one off production or small batch production (aluminium moulds)
Products:
Jewellery
Key fobs
Decorative components
MIG welding
A wire fed consumable electrode and an arc shielding gas to weld two pieces of metal together
Wire is fed from a spool
Current, feed rate and power can be altered
Addition
Inert gas - CO2 or argon
Suitable for thin gauge metals such as medium carbon steel or mild steel
Products:
Tubular products - climbing frames, bike frames and vehicle exhausts
TIG welding
Uses a filler rod, tungsten electrode and a shielding gas to weld two pieces of metal together
Addition
Uses argon or helium
Accurate, strong welds but requires high skill levels and is quite slow
Uses:
Stainless steel ladders for boats and swimming pools
Car exhausts
Oxy-acetylene welding
Uses oxygen and acetylene to fuel a torch to melt a steel filler rod into the joint
Addition
Useful for quick repair jobs or when no electric power supply is available
Uses to weld mild steel sheet, tube or plate when no arc welding processes are available
Spot welding
Sheet held between two copper electrodes that form a weld when the charged electrodes make contact with the metal
Addition
Used to weld mild steel sheet metal at points along a length
Soldering
Uses a filler material of a lower melting point than the metal being joined typically this is an alloy combining steel and copper called solder
Addition
Requires flux to prevent oxidation
Weak join
Used for:
Circuit boards and electrical components
Joining precious metals - jewellery
Joining copper pipe in plumbing
Brazing (hard soldering)
Similar process to soldering except it uses a brazing torch and a brazing rod (brass filler rod)
Addition
Used to join dissimilar metals such as mild steel to aluminium
Lower temperature than welding so it is suitable for joining thinner mild steel tube or bar
Requires high skill
Flux is need to prevent oxidation
Can be aesthetically pleasing
Riveting and pop riveting
Two pieces of sheet metal are drilled and overlapped, a rivet is then hammered into the hole to form the join
In pop riveting a rivet gun and a rivet and pin, this is good for when the underside of the join is inaccessible
Metal processes - forming
Press forming
Spinning
Cupping and deep drawing
Drop forging
Wrought iron forging
Bending
Rolling
Metal processes redistribution
Sand casting
Gravity die casting
Hot/cold chamber pressure die casting
Investment casting
Low temperature pewter casting
Metal processes - addition
MIG welding
TIG welding
Oxy-acetylene welding
Spot welding
Soldering
Brazing
Riveting and pop riveting
Uses of hot/cold chamber pressure die casting
lock mechanism components for sliding doors
door locks
electrical components
Advantages of die casting
High quality surface finish
Highly accurate
Rapid cooling of components makes pressure die casting suitable for large-scale production
Using alloys with a low melting point results in lower energy costs
Temporary fasteners and joining methods
Self-tapping screws - used for joining thin sheet metal, the screw is inserted into the pilot hole and it cuts its own thread
Machine screws - a bolt whereby the thread is the whole length of the shaft, used to join thicker pieces of metal such as covers on motor or gear housings. Top part has a large clearance hole whilst the other part has a thread that the bolt screws into
Nut and bolts - go all the way through both pieces of metal, a nut is tightened on the end to keep the bolt in place
Why must metals be centre punched before drilling?
To provide an accurate starting point
To prevent the drill from slipping/guide the drill
