16. Metal processes Flashcards
What can metal processes be grouped into?
- forming
- redistribution
- wastage
What are metal forming processes?
processes in which no material is removed , but materials are deformed to produce required shapes
What are metal redistribution processes?
processes where the metal is changed from one form to another without loss of material
e.g. liquid metal poured into a mould to take a solid shape
What are metal wastage processes?
processes that cut away material to leave the desired shape
What are the metal processes?
- press forming
- spinning
- cupping and deep drawing
- drop forging
- wrought iron forging
- bending
- rolling
- sand casting
- gravity die casting
- pressure die casting (hot chamber)
- pressure die casting (cold chamber)
- investment casting
- low temperature pewter casting
What type of process is press forming?
forming
What is the metal stock form used for press forming?
sheet
What are the key features of press forming?
- shapes sheet metal into 3D forms
- often used in conjunction with robots for lifting the sheet into place
- suitable for mass production or large scale batch production
What products are made by press forming?
- metal seats
- car body panels
- boxes and containers
Draw the process diagram for press forming, with labels.
See flashcards with pic on.
What type of process is spinning?
forming
What is the metal stock form used for spinning?
sheet
What are the key features of spinning?
- product may show parallel lines where the sheet has been forced onto the mandrel
- suitable for mass production or small batch production
What products are made by spinning?
- body of stainless steel kettles
- saucepans
- metal light shades
Draw the process diagram for spinning, with labels.
See flashcards with pic on.
What type of process is cupping and deep drawing?
forming
What is the metal stock form used for cupping and deep drawing?
sheet (round blank)
What are the key features of cupping and deep drawing?
- starts with metal blank
- metal is stretched into shape
- high initial tooling costs
- used for large scale mass or continuous production
What products are made by cupping and deep drawing?
- tube-like shapes such as fire extinguishers, aerosol cans, drinks cans
Draw the process diagram for cupping and deep drawing, with labels.
See flashcards with pic on.
What type of process is drop forging?
forming
What is the metal stock form used for drop forging?
billet
What are the key features of drop forging?
- used for products that need to be tough and hard
- maintains the internal grain structure which retains the strength
- hot metal billet shaped on an anvil or die and then pressed into shape and cooled
- suitable for mass production
What products are made by drop forging?
- spanners
- pliers
- screwdriver shafts
Draw the process diagram for drop forging, with lables.
See flashcards with pic on.
What type of process is wrought iron forging?
forming
What is the metal stock form used for wrought iron forging?
bar
What are the key features of wrought iron forging?
- uses wrought iron (carbon content less than 0.08%)
- can be hand or hydraulic press process
- suitable for one off or small batch production
What products are made by wrought iron forging?
- decorative metalwork such as gate scrolls
- decorative fencing
Draw the process diagram for wrought iron forging, with labels.
See flashcards with pic on.
What type of process is bending?
forming
What is the stock form used for bending?
sheet or plate
What are the key features of bending?
- does not include any punching or trimming of the metal
- simple bending can be carried out in a school or college workshop
- used for large scale batches in industry
What products are made by bending?
- seams on metal edges
- bending sheets for product casings or housings
Draw the process diagram for bending, with labels.
See flashcards with pic on.
What type of process is rolling?
forming
What is the stock form used for rolling?
billet
What are the key features of rolling?
- hot rolling metal results in uniform mechanical properties, no deformation or stresses
- surface usually coated with carbon deposits, which must be removed using acid picking
- cold rolling results in a material that has tighter tolerance and better surface finish
What products are made using rolling?
- hot rolling
- I beams
- angle bar
- plate and channel
- railway tracks
- cold rolling
- filing cabinets
- chairs
- steel drums
- containers
Draw the process diagram for rolling, with labels.
See flashcards with pic on.
What type of process is sand casting?
redistribution
What is the stock form used for sand casting?
molten metal from a billet
What are the key features of sand casting?
- labour intensive process
- not a high quality surface finish
- suitable for one off or small batch production
What products are made by sand casting?
- railway carriage wheels
- wood working clamps
- vices
- motor housings
- bollards
- drain covers
- post boxes
Draw the process diagram for sand casting, with labels.
See flashcards with pic on.
What type of process is gravity die casting?
redistribution
What is the stock form used for gravity die casting?
molten metal from a billet
What are the key features of gravity die casting?
- lower melt point metals such as aluminium, aluminium alloys and zinc based alloys
- relies on gravity to help the metal flow into the mould
- used for thicker mould sections
- used for very large batch and mass production
What products are made by gravity die casting?
- allow wheels
- engine components
- door knobs and handles
Draw the process diagram for gravity die casting, with labels.
See flashcards with pic on.
What type of process is pressure die casting (hot chamber)?
redistribution
What is the stock form used for pressure die casting (hot chamber)?
molten metal from a billet
What are the key features of pressure die casting (hot chamber)?
- lower melt point metals such as aluminium, aluminium alloys and zinc based alloys
- molten metal stored in a chamber then a shot of molten metal is forced into the die
- fast process
- used for very large batch and mass production
What products are made by pressure die casting (hot chamber)?
- toy cars
- collectible figures
- decorative door knobs and handles
Draw the process diagram for pressure die casting (hot chamber), with labels.
See flashcards with pic on.
What type of process is pressure die casting (cold chamber)?
redistribution
What is the stock form used for pressure die casting (cold chamber)?
molten metal from a billet
What are the key features of pressure die casting (cold chamber)?
- lower melt point metals such as aluminium, aluminium alloys and zinc based alloys
- molten metal ladled into the shot chamber and hydraulically pushed into the chamber
- used for very large batch and mass production
What products are made by pressure die casting (cold chamber)?
- toy cars
- collectible figures
- decorative door knobs and handles
Draw the process diagram for pressure die casting (cold chamber), with labels.
See flashcards with pic on.
What type of process is investment casting?
redistribution
What is the stock form for investment casting?
molten metal from a billet
What are the key features of investment casting?
- used for intricate or awkward shapes that would be difficult or impossible to mould using any other casting process
- high quality excellent finish
- wax patterns are cast from a master mould
- repeatable, quality process
What products are made by investment casting?
- cast jewellery
- collectible figures
- hip replacement joints
What type of process is low temperature pewter casting?
redistribution
What is the stock form used for low temperature pewter casting?
molten metal from a billet
What are the key features of low temperature pewter casting?
- used for school or college projects
- can be used with simple MDF moulds
- suitable for one off production or small batch (with aluminium moulds)
What products are made by low temperature pewter casting?
- jewellery
- key fobs
- decorative components
What are the addition/fabrication processes?
- MIG welding
- TIG welding
- oxy-acetylene welding
- spot welding
- soldering
- brazing (hard soldering)
- riveting and pop riveting
What type of process is MIG welding?
addition
What are the key features of MIG welding?
- uses an electrode wire
- suitable for thin-gauge metals, medium carbon steel or aluminium
- uses an inert gas such as CO2 or argon
- suitable for one off fabrication or on an assembly line
What products are made by using MIG welding?
- tubular produts
- climbing frames
- bike frames
- vehicle exhausts
Draw the process diagram for MIG welding, with labels.
See flashcards with pic on.
What type of process it TIG welding?
addition
What are the key features of TIG welding?
- uses a filler rod
- accurate, strong welds but requires high skill
- slow method
- uses an inert gas (argon or helium)
What products are made by using TIG welding?
– stainless steel ladders for boats or swimming pools
- welding stainless steel car exhausts
Draw the process diagram for TIG welding, with labels.
See flashcards with pic on.
What type of process is oxy-acetylene welding?
addition
What are the key features of oxy-acetylene welding?
- uses a steel filler rod
- useful for quick repair jobs or in remote locations where there is no electric power supply
What products are made by using oxy-acetylene welding?
used to weld mild steel sheet, tube or plate where arc welding processes are not available
Draw the process diagram for oxy-acetylene welding, with labels.
See flashcards with pic on.
What type of process is spot welding?
addition
What are the key features of spot welding?
sheet held between two copper electrodes that form a weld when the charged electrodes make contact with the metal
What products are made by using spot welding?
- used to weld mild steel sheet metal at points along a length
What type of process is soldering?
addition
What are the key features of soldering?
- uses a filler material of a lower melting point than the metal being joined
- typically solders are an alloy of tin and copper
What products are made by soldering?
- lightweight applications
- thin gauge metals
- joining precious metals such as gold and silver
- for jewellery
- joining copper pipe in plumbing
What type of process of brazing (hard soldering)?
addition
What are the key features of brazing?
- uses a brass filler rod
- carried out using either oxy-acetylene or a gas and compressed air brazing hearth
- suitable for one off production or small batch
- used to join dissimilar metals such as mild steel sheet to aluminium, copper and nickel
What products are made by brazing?
- lower temperature than welding, so suitable for joining thinner gauge mild steel tude or bar
What type of processes are riveting and pop riveting?
addition
What are the key features of riveting?
- uses two pieces that are overlapped and drilled
- the end of the shaft is then hammered over to join
What are the key features of pop riveting?
- uses a rivet gun (or riveting pliers) and a rivet and pin
- good for where underside of joint is inaccessible
What products are made by using riveting and/or pop riveting?
sheet metal or plate joining
Draw the process diagram for riveting, with labels.
See flashcard with pic on.
Draw the process diagram for pop riveting, with labels.
See flashcard with pic on.
What are the temporary fasteners and joining methods?
- self-tapping screws
- machine screws
- nut and bolt
When are temporary fasteners used?
- where a permanent joining method is not required
- in situations where a product may need to be disassembled or accessed for repair
What are self-tapping screws?
- used for joining thin sheet metal
- pilot hole is drilled through the metal parts to be joined
- as the screw is screwed in, it cuts its own thread, which holds the screw in place
What are machine screws?
- a type of bolt where the thread is the whole length of the shaft
- used to join thicker pieces of metal such as inspection covers on motor or gear housings
- top part to be joined will have a clearance hole larger than the thread on the bolt
- the bolt goes through this and is screwed into a threaded hole in the second piece
- machine screws are often tightened with a spanner or Allen key
What are nut and bolts?
- bolts are similar to machine screws, but instead of being inserted into a threaded hole, the go all the way through both pieces of metal
- a nut is tightened on to the end to keep the pieces together
What are the metal wasting processes?
- milling
- turning
- flame cutting
- plasma cutting
- laser cutting
- punching/stamping
What is milling?
- the work to be machined is clamped on to the table of the machine
- the table can run in the x direction (left and right horizontally), the y direction (forwards and backwards), and the z direction (up and down vertically)
- to cut slots, shape edges or thread holes
What is turning?
- carried out on a centre lathe
- work such as a bar can be held in a rotating chuck and machined to reduce the diameter, and to square or ‘face-off’ the end, thread and drill
- can be done manually or by using CNC lathes
- material is machined by cutting tools held in place in a tool post, which can be moved in and out, and along the bar
What is flame cutting?
- uses oxy-acetylene gas and a special flame cutting torch to deliver a very intense and focused flame above 3500 degrees
- used to cut low carbon and alloy steel plate
- has an additional jet of oxygen to intensify the flame and pierce the metal
- does not require electricity
- disadvantage is that it is difficult to maintain a parallel line with high levels of tolerance
What is plasma cutting?
- plasma is a super-heated ionised gas that is electrically conductive
- plasma cutter will use this to transfer the energy from the power supply to a conductive material such as steel plate
- the heat generated by the plasma can be as high as 28,000 degrees, which quickly burns through the material and blows it away
- the resulting cut is fast and clean
What is laser cutting?
- process can be used in industry for precision cutting metals
- lower-powered lasers are readily available in schools and colleges to cut manufactured boards and acrylic sheet
- uses the power from a high powered laser beam that is directed through optics
- the laser head contains a lens that focuses the laser into a fine beam for cutting and engraving
- usually have a very fine tolerance
- laser cutting is more accurate and uses less energy than plasma cutting, but cannot cut the same thickness of material
- in industry, laser cutting is typically used to cut flat sheet material, but not able to cut the same thickness as plasma cutting
What is punching/stamping?
- uses computer controlled machines that stamp out sections of sheet material
- uses the shearing action on a sheet metal placed between an upper tool (punch) and lower tool (die)
- suitable for small and medium size production runs
- normally used for processing materials from 0.5mm to 6mm thickness
