Engineering - Processes Flashcards
What are the 5 materials used in injection moulding?
Polystyrene
Nylon
Polypropylene
Polythene
ABS
Describe injection moulding
Granules of plastic powder are poured or fed into a hopper
A motor turns a thread which pushes the granules along the heater section which melts then into a liquid. The liquid is forced into a mould where it cools into shape
The mould then opens and the shape is removed
What are the 6 advantages of injection moulding?
Very complex 3D shapes can be produced
High volumes can be produced with consistent quality
Vary fast compared to other moulding processes
Little labour costs
Little waste
Little to no finishing of the parts is needed
What are the 2 disadvantages of injection moulding?
High initial set up costs
Moulds are expensive to make
Describe blow moulding
The plastic is fed in granular form into a hopper that stores it
Heated plastic granules are injection moulded into a pre-form shape which is positioned into a mould
Air is forced into the mould which forces the plastic to the sides giving a hollow shape
The mould is cooled and then removed
What are the 5 materials used in blow moulding?
HDPE
LDPE
PP
PVC
PET
What are the 4 advantages of blow moulding?
Once set up, blow moulding is a rapid method of producing hollow objects
Well suited to low and high production
Many types of plastic can be used
Can be less expensive than injection moulding
What are the 4 disadvantages of blow moulding?
Limited to hollow parts
Moulds can be expensive
It is difficult to produce shapes that don’t allow easy extraction from the mould
Difficult to produce triangular shapes
Describe rotational moulding
Moulds are loaded with a precise amount of thermoplastic powder
The moulds are clamped together
The mould is then rotated in a heated chamber and the thermoplastic is melted. The continuous rotation ensures the thermoplastic covers all of the inside of the mould
The product is then extracted
What are the 5 materials used in rotational moulding?
Polyethylene
Polypropylene
PVC
Nylon
Polycarbonate
What are the 6 advantages of rotational moulding?
A hollow part can be made in one piece with no seen lines or joints
Ideal for rigid, tough and flexible shapes
No material waste
Different types of product can be moulded together on one machine
Surface textures can be applied by texturing the mould
Moulds are cheaper than for injection and blow moulding
What are the 2 disadvantages of rotational moulding?
Only hollow shapes can be produced and more complex shapes need injection and blow moulding
The plastic used must be ground down into a fine powder which takes money and time
Describe thermoforming
Sheet plastic is held securely between the 2 halves of the mould
The plastic is heated just above its softening point
The mould halves close and a vacuum is applied through the lower mould
The upper mould ensures the required amount of detail is achieved
What are the 4 materials used in thermoforming?
ABS
Polypropylene
Acrylic
Polycarbonate
What are the 2 advantages of thermoforming?
Low cost process
Works well when creating smooth shapes that need extra detail
What are the 3 disadvantages of thermoforming?
Deep moulds can result in thin and stretched parts of the product
Limited to simple designs
Trimming is often required creating some waste
Describe vacuum forming
A sheet of plastic is heated to a temperature ready for forming
A mould is pushed up into the plastic sheet
A vacuum is turned on and this pumps out all of the air beneath the sheet
The sheet has the shape of the former pressed into its surface
What are the 4 materials used in vacuum forming?
ABS
Polystyrene
Acrylic
Polycarbonate
What are the 4 advantages of vacuum forming?
Available to schools
Simple process
Can be made from a range of materials
Suitable for one-off and large scale production
What are the 3 disadvantages of vacuum forming?
Additional processing required to trim excess material
Moulds can’t have vertical sides
You can only have undercuts with special moulds
Describe plastic extrusion
Granules of plastic powder or granules are poured or fed into a hopper
A motor turns a thread which pushes the granules along a heater section
The heater softens the plastic which is then forced through a die
As the plastic leaves the die, it is cooked
The exercises product is then cut to the required length
What are the 4 materials used in plastic extrusion?
Plastics
Aluminium
Wood-plastic composites
Ceramics
What are the 2 advantages of plastic extrusion?
The best way to make long products with the same profile
Only requires simple dies
What are the 2 disadvantages of plastic extrusion?
Parts need to be cut to shape, assembled or drilled
Not suitable for one-off productions because it produces very long parts
Describe calendaring
Pre-mixed thermoplastic is fed into rollers
Rollers are heated to just just above thermoplastic softening temperature
The plastic is forced through a gap roller to determine the thickness of the final product
The final roller chills the material
What are the 2 materials used in this process?
Thermoplastics
Cellulose acetate
What are the 4 advantages of calendaring?
Produces long continuous rolls without joins
Excellent for producing large quantities of flat sheets
Can be combined with printing or lamination
Very good at handling heat sensitive polymers as it produces very little thermal degradation
What is the disadvantage of calendaring?
Suited to large scale production only
Describe compression moulding
Compressed plastic powder is placed between the 2 halves of the mould
The mould is heated to a temperature that causes the long chain molecules of the plastic to link together
The mould is held together for a period of time to allow all plastic to link
What are the 2 materials used in compression moulding?
Thermosetting plastics
Ceramics
What are the 5 advantages of compression moulding?
Ideal for thermosetting plastics
Long production runs
Low set up and mould costs compared with injection moulding
Little waste material
Ideal for creating solid parts with thick walls
What is the disadvantage of compression moulding?
Limited complexity of shapes produced
Describe dip moulding
A mould is dipped into a bath of liquid / molten plastic
The mould is removed from the plastic having been coated with a layer of the plastic
The mould is cooled and the end product is removed from the mould
What are the 3 materials used in dip moulding?
PVC
Polyurethanes
Latex
What are the 4 advantages of dip moulding?
Highly cost effective for short production runs
Prototypes and formers can be produced very quickly
No split lines in the final product
Suitable for large production runs
What is the disadvantage of dip moulding?
Limited to simple shapes
Describe blanking and piercing
When a sheet of metal has a hole punched through it, this is piercing
When a part to be used is punched out of a sheet metal, it is a blank
These processes require punches which use a shearing action
What is the material used in piercing and blanking?
Sheet metal (usually aluminium)
What are the 3 advantages of blanking and piercing?
Can produce many different shapes
Can be used for any sheet metal
High level of accuracy
What are the 3 disadvantages of blanking and piercing?
Limited to size of stock materials
If the material is not fully utilised, there can be a lot of wastage
Restricted to sheet material
Describe plasma cutting
Plasma cutting is a stream of ionised gas that becomes so hot it vapourises the metal being cut
It can be done with hand-held, manual or CNC control
What is the material used in plasma cutting?
Any electrically conductive metallic metal (usually stainless steel or aluminium)
What are the 4 advantages of plasma cutting?
Economical process when creating small batches
Provides smooth clean cuts
Sheet material thinner than 8mm may distort
Large range of materials
What are the 2 disadvantages of plasma cutting?
Uses a lot of energy
High amount of waste
Describe laser cutting
A highly accurate form of cutting and decorating materials using a fine beam of light controlled by a CNC machine
What are the 4 materials used by laser cutters?
Card
Soft woods
Thermosetting plastics
Some metals
What are the 5 advantages of laser cutters?
Can engrave or cut depending on the power output
Highly complex shapes
Suitable for batch production
Very accurate
More materials than plasma cutting
What are the 4 disadvantages of laser cutters?
Can leave burn marks
Uses a lot of energy
High amount of waste
Not suitable for large scale production
Describe 3D printing
Additive layer manufacturing to make 3D objects from a digital model
Material is heated, printed and then it cools quickly
What are the 2 materials used in 3D printing?
Thermoplastics
Some metal alloys
What are the 2 advantages of 3D printing?
Any designed object no matter its complexity can be printed
Great for prototyping until it is perfect
What are the 2 disadvantages of 3D printing?
Illegal objects can be printed
Takes a very long time to print one batch
Describe press forming
Sheet metal materials are loaded into a hydraulic press and clamped into the blank holder
The punch forces the material through the die to take the shape of the punch
What are the 4 materials used in press forming?
Steel
Copper
Brass
Aluminium
What are the 3 advantages of press forming?
High stiffness of final products
Can be carried out at room temperature
Suitable for medium and high production
What are the 2 disadvantages of press forming?
High level of stresses needed to overcome resistance of metal being pressed
High tooling costs
Describe sand casting
A pattern is made
Each part of the pattern is placed on a base board
A drag is placed over it
Sand is packed around the pattern
Mould halves are fitted together with locating pins
Molten metal is poured into the running gate
Once the metal solidifies, the mould is broken open
What type of materials are used in sand casting?
Low melting points
Commonly aluminium, copper alloys, lead etc.
What are the 4 advantages of sand casting?
Low cost process
Easy to operate
Advanced sand casting can produce very detailed and intricate parts
Flexible levels of production
What are the 3 disadvantages of sand casting?
Can be labour intensive
Unit costs can be high when used for one-off production
Parts may be require a lot of finishing
Describe high pressure die casting
Molten metal is poured into a chamber
An injection piston or plunger forces the molten metal under high pressure into the casting cavity
The pressure is maintained until the metal solidifies
Injector pins are used to push the components out of the die
What are the 2 most common materials used in high pressure die casting?
Aluminium
Zinc
Usually low melting points
What are the 4 advantages of high pressure die casting?
Suitable for metals with low melting points
Ideal for complex shapes
High level of detail can be achieved
Excellent surface finish
What are the 3 disadvantages of high pressure die casting?
Expensive so it is only suitable for high production
Parts are not guaranteed to have high structural strength
Excess material requires additional trimming
Describe sintering
Materials are crushed into a powder
The powder is compacted into a die which will give the product being made its final shape
The compacted shape is then heated so that the powder particles bond
What materials are used in sintering?
A variety of metals, plastics, glass and ceramics
What are the 4 advantages of sintering?
Good surface finish
No wasted material
Useful for processing materials that can’t be processed in any other way
Produce complex shapes
What are the 3 disadvantages of sintering?
There can be problems with shrinkage
Allows use of otherwise waste materials
Requires many different stages
Describe drop forging
Very large forces are exerted onto a pre-heated metal billet between the 2 die halves
It is used as a refining process large numbers of similarly shapes objects are needed
What materials are used in drop forging?
Most ferrous materials
Some non-ferrous materials like aluminium and titanium
What are the 2 advantages of drop forging?
Very strong products
Can be forged cold to reduce energy usage
What are the 2 disadvantages of drop forging?
It can be very expensive
Significant dangers working with hot metals
Describe wood laminating
Adhesive is applied to the face of each veneer
Each veneer is stacked on top of each other
Veneers are clamped into position in a die
The adhesive dries and the shape is formed
What material is used in wood laminating?
Wood veneers (usually birch)
What are the 4 advantages of wood laminating?
Suitable for different production scales
Range of thicknesses allowed
Creates strong and lightweight products
Can be combined with other materials to enhance properties
What are the 2 disadvantages of wood laminating?
Involves many steps
Restricted to bends in a single direction
Describe steam bending
Wood is steamed and softened by hot steam to make it more moist to make it softer
Once the wood is steamed it is more flexible
What materials are used in steam bending?
Hard woods
What are the 4 advantages of steam bending?
Has good aesthetic appeal
The most effective technique for bending solid wood
Can be done with simple equipment
Parts with strong weight to strength ratio can be produced
What are the 3 disadvantages of steam bending?
Only high quality hard wood can be used
Not suitable for applications that require precision
The bend radius depends on the wood used
Describe die cutting
The sharp edges of the cutting die are brought down on to a thin sheet material
The material can be cut, creased and perforated in one step
What 4 materials are used in die cutting?
Card
PVC
PET
Polypropylene
What are the 4 advantages of die cutting?
Low set up cost
Cost effective for batches
Many shapes can be cut with single step
Large batches produced very quickly
What is the disadvantage of die cutting?
3D products need to be assembled by hand
Describe brazing
The metal to be joined must be cleaned so that grease and dirt is removed
Flux is brushed along the joint to prevent oxidation taking place on the metal surfaces
Pressurised gas and air is fed through a nozzle and ignited
The joint is heated with the flame until it eventually becomes so hot that it becomes red in colour
A brazing rod (copper-zinc alloy) is pushed gently against the joint
The rod will begin to melt and run along the joint
This is done until the whole joint is brazed
What are the 2 materials that are processed with brazing?
Copper
Steel
What are the 4 advantages of brazing?
Low cost
Suitable for many production scales
Complex and intricate joints can be achieved
The bond is extremely strong
What are the 3 disadvantages of brazing?
Requires a high degree of cleanliness
The joint colour is often different to colour of the material being joined
Not as strong as a welded joint
Describe TIG welding
TIG generates heat via an arc of electricity jumping from a tungsten electrode to the metal surfaces to be welded
The heat is sufficient to melt the joint edges
The electrode is coated in flux which when melted prevents the joint from oxidising
What are the 4 materials that are processed by TIG welding?
Titanium
Also: carbon steel, stainless steel and aluminium
What are the 3 advantages of TIG welding?
Using electricity decreases sparks, smoke and fumes
Less contamination in the weld than brazing providing better quality joints
No tooling costs
What are the 3 disadvantages of TIG welding?
Requires a lot of set up and is hard for new users to learn
More expensive and takes longer than some other types of welding
Requires quite a lot of skill and practice
