Unit 9 - Metal Forming Process Flashcards
What is press forming?
- Press forming shapes from sheet metal into 3D forms
- E.g. low carbon steel / aluminium
- Common in mass production
- Dies are made from hardened steel
What is spinning?
- A way of forming sheet metal giving radial symmetry
- Kettles, saucepans are made this way
- used in mass and batch production
What is cupping and deep drawing?
- Used to form tube like shapes from sheet metal
- E.g. fire extinguisher, aerosol cans
- Deep drawing is when the depth of pressing exceeds the diameter
- Corners of the punch are rounded so the metal stretches
- High set up costs
What is drop forging?
- Used to shape hot metal, used when the product needs to be tough and hard
- spanner’s, pliers
- Hot metal is forced into shape under great pressure therefore creating a new shape
- Mass production, can vary though
What is wrought iron forcing?
Wrought iron has a low carbon content making it malleable and easy to shape
What is scrolls?
- Wrought iron is heated in a forge then shaped
- Scroll formers and twisting bars help make intricate shapes
- One-off, limited batch production
What is bending?
- A press brake is used for bending sheet or plate metal
- Stock material is clamped between a punch and die
- Break holds the metal and lowers the punch to bend the metal into shape
What is rolling?
- Used to reduce the thickness of metals
- Used to make structural steels like beams, bars and channel for the construction industry
- Used with hot metal that has been heated above recrystallisation temperature
- Can result in surface carbon deposits but has no deformation or stresses
What is die casting?
- Uses a lower melting point metal e.g. alluminium, pewter, and zinc
- It is high cost initial costs and can make complex items
- High quality finish items
- E.g. alloy wheels, metal toys
How does die casting work?
Molten metal is fed into the die (mould) and where it cools
Ejector pins ensure the casting releases from the die
What is sand casting?
- used to form high melting point metals
- made from special moulds made from ‘green sand’
- used for engine blocks, post boxes and train wheels
- one-off, batch
How does sand casting work?
A pattern is used to make the mould. The mould and a able to be opened in halves so the cooled metal can be removed
What is investment casting?
- used to cast items with awkward shapes that would be difficult to mould using any other casting process
- can be used by many metals
- produces a high quality finish
- repeatability is achieved
What is pewter casting?
- the metal has a low melting point and is often used in schools
- ideal for jewellery
- can be shaped by common tools
What is MIG welding?
- used to weld thin gauge metal such as aluminium and steels
- heat is generated from an electrode
- workpiece is clamped to the negative connection
- e.g. climbing frames, bike frames
How does MIG welding work?
What does MIG stand for?
- used a filler wire as an electrode
- the wire electrode melts in the arc and fills the gap between the two metals
- welding torch is gently swirled to form a bead of weld
- Metal Insert Gas
What is TIG welding?
What does TIG stand for?
- is used to weld stainless steel, aluminium and copper alloys
- an electric arc welding process
- the tungsten does not melt in the process, a filler material is added separately
- uses a gas shield of argon or helium
-Tungsten Insert Welding
What is spot welding?
- welds sheet metal together without a filler material
- heat and pressure are applied to the area to be welded
- surfaces are joined by heat generated from resistance to an electric current
What is oxy-acetylene welding?
- used to weld low carbon steel sheet, tube or plate
- mixes two high pressure gases ( oxygen and acetylene ) forming a very hot and intense flame
What is soft soldering?
- used low melting point metals (solder) to join metals together
- traditionally a tin/led alloy with a low melting point (320 degrees C)
What is hard soldering?
- uses a higher temperature than soft soldering
- it is used to join precious metal like gold and silver
- a flux must be applied to prevent metal oxidisation
What is brazing?
- uses either an oxy-acetylene flame or gas and compressed air brazing hearth
- needs a lower temp than welding as brazing melts lower
- not as strong as others
What is riveting?
- is semi-permanent joining method used to join sheet or plate metal
- are metal fasteners that have a head at one end and a shaft or tail the other end
What is cold-formed rivets?
- require access to both sides of the sheet material
- they are installed with a ‘set’ and ‘snap’ which domes the ends while pressure is applied
What is pop riveting?
- quick and easy to use
- not very strong
- require a pop riveting gun
- ideal where the underside of the joint is inaccessible
- a form of pop rivets is used in aircraft production
How does pop riveting work?
- create a semi-permanent fixing between two thin sections of metal
- the gun applies pressure to the rivet by pulling the shank until it breaks
- this action splays the inserted end to create the bond
What are self tapping screws?
- cut their own thread as they are screwed into sheet metal/some plastics
- used in panel products which require maintenance
- some can create their own hole, a pilot hole is advised for a precise and accurate result
What are machine screws?
- a type of bolt with a fine thread
- used in motor and gear housings and in many electronic product castings
- different types include: cheese head, round head, counter sunk
- identified by their length, diameter and head profile
What is the purpose of nuts and bolts?
- they are passed all the way through, then a nut is tightened at the other end
- some types of nut, like castle and nylon are designed to be loose
What is a wasting process?
- involve the removal of material by cutting
- they produce waste or unusable material
What are milling machines?
- cut vertically or horizontally but some advanced mills can now cut on many axes
What is complex milling?
- used to create highly accurate machine parts
- the workpiece and the rotary cutting tools move through x, y and z axes
- completely geometry can be creating using a 4th and 5th axis
- can be done manually and with a CNC
What is 3D milling?
- some mills use multi-tooled cutters to waste the workpiece
- mills can be used to create holes, chamfers, slots
- slots can be machined using special cutters with accurate profiles
- milling is suitable for one-off intricate components but can be set up to run repeatedly as part of batch production
What is turning?
- a centre large or engineer’s large is used to turn metal
- the workpiece is held with a three or four jaw Chuck, the cutting tool moves in two axes
- a Chuck can also be fitted to the tail stick for centring and drilling
- longer workpieces are often centred using the tail stock
What is a centre lathe?
- centre lathes use single point cutting tools usually made from HSS or silicone carbide
What is a manual turning lathe?
- manual turning
- can produce bespoke and one-off pieces
What are CNC turning?
- use multi-tool heads which change tools automatically for a given task
- CAD programmes allow complex and accurate shapes to be repeated quickly and efficiently
Name as many lathe turning techniques (out of 6)
- facing
- parallel turning
- taper turning
- parting
- drilling
- knurling
What is flame cutting?
- uses oxyacetylene gas and a flame cutting torch to focus a flame up to 3500 degrees C
- oxygen intensifies the flame and forces the molten metal out
- used to cut low carbon and alloy steel plate
What is plasma cutting?
- plasma is an ionised gas which is electrically conductive at very high temperatures
- plasma cutting generates a faster, cleaner cut than flame cutting
- suitable for one off and batch production
- applications: sculptural signs and bespoke gates
How does plasma cutting work?
- can be manual or done by CNC
- electric arc is sent though plasma cutting gas and out a constructed opening
- can cut steel, aluminium, stainless steel etc up to 150mm thick
What are metal laser cutters?
- a high powered laser beam is directed through optics at the workpiece on the laser bed
- the beam focus, speed and power can be adjusted
- lasted melts the metal and compressed air/gas blows the molten metal clear
- fine beam allows for high levels of accuracy
What is laser cutting
- can be used on sheet metal
- cannot cut metal plate that is too thick
- fast, high accuracy levels and high quality finishes
- high energy consumption
- suitable for one-off to large batch production
What is punching and stamping?
- stamping pierces the metal sheet to cut out a shape or slot -> the cut outs are recycled
- blanking creates cut out parts for further processing and recycled the original punch sheet
What are the two main reasons finishes are applied to metals?
- enhance appearance (aesthetics)
- ferrous metals rust over time - some metals do not form a strong oxide layer to protect them from corrosion so something is added to help protect them
What does cellulose paint provide metal with?
- colour and a barrier against corrosion
- needs multiple layers
- high quality finish
- contains VOC’a
- workpiece must be degreased before hand
- used on cars
What does acrylic paint provide metal with?
- water-based, durable and hard wearing
- usually require heat, professional equipment
- up to 24 hours to cure, doesn’t take many coats (e.g. 2/3)
- application include bicycles
What is electroplating?
- uses a desired metal to coat a (usually) cheaper base metal
- provides a protective layer with increased aesthetic appeal
- negative electrode is the object to be plated
- positive electrode is the coating metal
- electrolyte solution is a solution of the coating metal
How do sealants work?
- block the passage of air and fluids through metal points
- used on metals that are usually polymer based and act as a gasket, often in machinery
- help prevent decay/ corrosion
What are preservatives for metal?
- can provide temporary or long term protection
- often used in moulds or dies to prevent atmospheric corrosion or condensation build up
- mainly oil-based, used on machine beds
How does anodising work?
- aluminium work piece is immersed into an acid electrolyte bath
- electric current is passed through it
- cathode in the tank, aluminium cast as an anode
- magnesium and titanium can be anodised
What does anodising do to a workpiece?
- mainly on aluminium
- provides a hard wearing corrosion resistant surface
What is galvanising?
- costs iron or steel with zinc
- zinc is the protective layer
How does galvanising work?
Zinc carbonate forms when zinc is exposed to air and water
This layer is extremely resistant to corrosion and very strong
What is the zinc hot dipping method?
A workpiece is coated using a four stage process to ensure a good bond is made
- good for large pieces and thick coverage
What is included in the zinc hot dipping method?
- workpiece dipped into molten zinc bath at 830-850 degrees C
- then cooled, cleaned up and inspected to insure even thickness and good coverage
- good for large pieces and thick coverage
What are the first two parts of the anodising process?
Pre-treatment
- cleaning
- brightening / etching
What is done in the anodising process after pre-treatment?
Electrolysis
- the acid (electrolyte) is in a bath
- aluminium in in the acid alongside the cathode
- aluminium acts as anode
- electric current is passed through aluminium
What is the last two parts of the anodising process?
Post-treatment:
- colouring
- sealing
Finished
What can planting and metal coatings do?
- Increase wear and lubricity
- Offers a thermal barrier/improved conductivity
How does planting work?
- done using physical vapour deposition (PVD)
- uses heat and pressure to o fuse metal together
What is polymer coating?
-provides a thick, wear, water resistant and an air tight finish
How does polymer coating work?
- the metal is heated to 230 degrees C
- it’s dipped into a tank of fluidised polymer powder as warm air blows around it
- the heat from the metal bonds the metal and the polymer together
- then cooled and if solidifies
What is powder coating?
- provides an even coat
- move hardwearing than paint
- sprayed through an air gun
How does powder coating work?
- the charge creates a strong attraction between powder and the workpiece
- the piece is baked in an oven where the coating melts and bonds to metal
What is cathodic protection?
- Sacrificial anodes are used to control the corrosion of a metal surface
- The process makes the metal protected with an electrochemical cell
- The anode is bonded to the surface which corrodes instead of the metal
- Used in pipelines, fuel, oil rig foundations, and boat hulls
