1.4 Forming, redistribution and addition processes Flashcards
What are the 3 paper and board forming processes?
1 Die cutting and creasing
2 bending
3 laser cutting
What are die cutters used for?
To cut out paper or card ‘nets’ or ‘developments’. which, when folded and assembled, will form a 3D shape such as a box.
What is the process of die cutting and creasing?
1 Die cutters use a plywood substrate board into which steel cutting dies and creasing rules are inserted.
2 Rubber pads fixed to the press help to prevent the paper or card sticking as the press moves up or down.
3 The stock material is placed under the board, and aa press pushes the board into the board material, which then cuts out the net.
4 Where parts of the net are to be folded, the creasing rules score the paper or card. The creasing rules are not as high as the cutting die, and they are also blunt, so they do not cut the stock material.
What is the papers and board process of bending?
1 The stamped-out net is placed onto a folding table.
2 Some die cutting presses might be equipped with moving parts that help to bend or fold parts of a net automatically.
3 Some of the trickier finishing might be done by hand.
Why is the use of lasers becoming more common when manufacturing paper and boards prototypes?
Due to their speed, accuracy and the high level of detail that is possible. They are also very flexible
What are the 10 polymer processes?
1 vacuum forming
2 thermoforming
3 calendering
4 line bending
5 lamination (lay-up)
6 injection moulding
7 blow moulding
8 rotational moulding
9 extrusion
10 compression moulding
What type of production does vacuum forming use and why?
It is normally limited to to small-scale batch production due to it being a slow process.
However, if a larger scale of production is required, moulds can be made from cast and machined aluminium.
What products are made using vacuum forming?
lightweight trays
box inserts and liners
coffee cups
yoghurt pots
What is the process of vacuum forming?
- The mould is placed on the bed of the machine, which is called the platen. The platen is lowered to the bottom of the machine.
- Polymer sheet is clamped over the mould and a heater is pulled over the polymer sheet.
- When the polymer sheet has softened, the platen is raised into the polymer and the heat is removed.
- The vacuum pump is switched on, which sucks the polymer onto the mould.
- Once the polymer has cooled and returned to a solidified state, the platen is lowered and vacuum switched off.
- The mould is removed from the moulding. Excess polymer is then trimmed off.
What products are made from thermoforming?
bath
fruit punnets
cake boxes
sandwich boxes
What is the process of thermoforming?
A very similar process to vacuum forming, except there is an additional mould that is pressed onto the surface of the polymer sheet at the same time as the vacuum is applied, sucking the polymer down on to the mould below. The two moulds trap the softened polymer in between them, giving extra detail to the moulding.
What products are made using the calendering process?
thin polymer sheet and film
What type of production system does calendering use?
continuous
What is the process of calendering?
- It works by heating pellets of thermoplastics so that it melts into a dough-like consistency.
- It is then extruded between a series of heated rollers so that it becomes squashed and stretched to make it thinner.
- It is then finished on colling rollers, before being chopped into standard stock sheet sizes, or in the case of polymer film, it is rolled up for storage and distribution.
What products are made using line bending?
acrylic boxes
shelves
point of sale displays
What type of production is line bending suitable for and why?
one-off or limited batch production because it is quite slow and is a labour intensive process.
What is the process of line bending?
- Turn on the strip heater.
- Place the thermoplastic on the strip heater, aligning the heated strip with where you want the bend.
- Ensure that you keep turning over the plastic to heat both sides evenly and avoid burning the plastic and making it bubble.
- Once the plastic is hot enough to bend easily, place it in the jig to create the required angle for the product and allow it to cool.
What products does the lamination process make?
3D products from fibre-glass composites such as glass-reinforced plastic.
boats
yachts
kayaks
trains
What is the process of lamination for moulding glass-reinforced plastic?
- A mould or former in the shape of the product is prepared. This might be made from timber, manufactured boards or high density foam.
- The mould is coated with a release agent such as wax or PVA, or is covered with parcel tape.
- A top layer of gel coat is applied. The gel coat of polyester resin often mixed with a pigment to give a colour to the moulding. The resin might also have additives included to prevent degradation from UV and hydrolysis.
- Fibreglass matting is cut to size and laid over the former. Polyester resin is brushed onto the matting and a small roller is used to push out any air bubbles that may form and to smooth out the matting (this process is called stippling). The matting is available in a range of stock forms including chopped strand, woven and ‘tissue’, which is a fine grade matting for covering the surface.
- Step 3 is repeated until the desired thickness is achieved, and fine tissue matting is used on the top layers. A vacuum bag may be used to compress the layers of GRP before it sets.
- The GRP is allowed to set.
What products are injection moulded?
vacuum cleaners
clip fastenings
screw posts
battery housing
circuit board holders
(complex parts)
What type of production does injection moulding use and why?
large-scale mass production or continuous production, due to the high costs of the equipment and the moulds.
What is the process of injection moulding?
- Thermoplastic granules are poured into the hopper.
- An archimedian screw is rotated by a motor. This pulls the granules through the chamber and past electric heaters.
- The heaters melt the granules of polymer.
- When a sufficient charge if polymer has melted and formed at the end of the screw, a hydraulic ram forces the screw thread forward. This injects the polymer into the mould.
- The mould is water cooled, which enables the molten polymer to harden quickly.
- The mould opens and ejector pins push the moulding out.
- Any excess polymer is trimmed off the moulding. Formers and jigs may be used to maintain the dimensional accuracy of the moulding while it cools and hardens completely.
What products use the blow moulding process?
bottles
wide range of hollow products
Which polymers are used for blow moulding?
PET
LDPE
HDPE
PP
What type of production does blow moulding use and why?
continuous production due to the high set-up costs associated with the equipment and moulds
What is the process of blow moulding?
- The polymer is fed into the hopper.
- Sn Archimedean screw pulls the polymer through a heated section, melting the polymer.
- The melted polymer is extruded as a tube, which is called ‘parison’.
- The mould sides close around the parison and air is injected into the mould, forcing the polymer to the sides.
- The polymer is allowed to cool for a few seconds, the mould opens and the finished bottle is ejected.
What are the two types of blow moulding?
parison
preform
What types of products are made using rotational moulding?
traffic cones
kayaks
water tanks
children’s play equipment
What types of polymers are used for rotational moulding?
HDPE
PP
What type of production is normally used for rotational moulding and why?
large-scale batch or mass production due to the high set-up costs
What is the process of rotational moulding?
- Polymer powder or granules are loaded into a mould, which is clamped and sealed.
- The mould is transferred to an oven where it is heated to 260-370 degrees Celsius, depending on the polymer being used. The mould is rotated slowly (fewer than 20 rotations per minute) around two axes, and as the polymer is heated, it coats the inside of the mould.
- Once the polymer has achieved the correct thickness, the mould is cooled. Usually a fan and/or water is used to cool the polymer.
- When the polymer has solidified, the part will shrink slightly, allowing it to be removed.
What products are made from extrusion?
solid rod
hollow tubes
angles sections
What type of production does extrusion use?
Continuous
What is the process of extrusion?
- Polymer granules are loaded into the hopper.
- the Archimedean screw moves the polymer granules past the heaters.
- The heaters soften the polymer.
- When sufficient polymer has melted, the hydraulic ram pushes the Archimedean screw, forcing the polymer through a steel die. The shape of the die determines the shape of the extrusion.
- The extrusion may be supported by rollers as it leaves the die and is cooled by water or air.
- The extrusion is then cut to the desired length.
What polymers are used for compression moulding?
thermosetting polymers such as urea formaldehyde and melamine formaldehyde.
What products are made from compression moulding using urea formaldehyde?
electrical light fittings
switches
electrical plugs
What products are made from compression moulding using melamine formaldehyde?
polymer plates, bowls and mugs for picnic sets
children’s table sets
What is the process of compression moulding?
- A ‘slug’ of pre-weighed thermoset polymer is inserted into the pre-heated moulds.
- The moulds are closed and hydraulic pressure is applied. The pressure ensures that the polymer takes the shape of the mould.
- The moulds remain closed while cross-linking takes place and the thermoset ‘cures’.
- When the moulding has cured, the machine opens and the product is removed.
- Excess polymer known as ‘flash’ is removed.
What are 7 metal forming processes?
1 press forming
2 spinning
3 cupping and deep drawing
4 drop forging
5 wrought iron forging
6 bending
7 rolling
What type of products is press forming used for?
bar body panels, metal seats, boxes, containers
What type of metal is used for press forming and why?
carbon steel and aluminum because of their malleability and ductility
What type of production does press forming use and why?
mass production or large-scale batch production due to the cost and complexity of making the dies
What is the process of press forming?
1 Sheet metal is clamped over a die of the product that will determine the final shape of the pressing.
2 A hydraulic press pushes the die into the sheet metal. Cutting blades may be included to punch holes into the sheet and trim the excess from the edges.
3 The hydraulic die is lowered and the presses sheet component is removed.
4 The sheet may be placed into further press forming machines for additional pressing, where the shape is complex.
What type of products are made from spinning?
stainless steel kettles, saucepans or other products with radial symmetry.
How can spun products be identified?
Parallel lines that are formed on the surface of the metal during the process
What type of production is used when spinning metal products?
Spinning is typically used in mass production, and can be set up using computer controlled machines so that thousands of identical products can be made. However, as the formers are relatively simple, it can be used in batch production, particularly where dome-shaped items need to be made but the quantity required does not justify the costs associated with press forming.
What is the process of spinning?
1 A former called a ‘mandrel’ is pout into the chuck. The sheet metal blank is held in place between the mandrel and the tail stock.
2 The roller tool is moved into the blank and is rotated with the mandrel. This starts to stretch the metal over the mandrel.
3 The roller tool is moved along the mandrel as pressure is maintained against the rotating blank.
4 The roller tool is moved to the end of the mandrel, while still maintaining contact with the blank. This finishes the shape of the product.
5 The finished product is removed from the mandrel.
6 Excess material is trimmed off following the spinning process.
What products are made from cupping and deep drawing?
tube-like shapes such as fire extinguishers and high pressure aerosol cans.
When does it change from cupping to deep drawing?
It is considered deep drawing when the depth of the pressing exceeds the diameter.
What type of production is used for cupping and deep drawing and why?
mass or continuous production is identical items due to the high setup costs
What is the process of cupping/deep drawing?
1 The pressing blank is clamped over a deep drawing die using a pressure pad or clamping ring known as a retainers.
2 A hydraulic press moved the deep drawing punch to be in contact with the blank. It then pushes the blank into the die cavity to make a cup shape.
3 The ‘cup’ is then pressed further down through the deep drawing die to make the desired tube shape.
When do manufacturers use drop forging/
When the finished product needs to be tough (impact resistant) and hard. Drop forging allows hot metals to be formed and maintains the internal grain structure and thus the strength required.
What type of products are made through drop forging/
spanners, pliers and screwdriver shafts
What type of production does drop forging use?
Mass production due to the fact that the dies are dedicated to making one specific item.
What is the process of drop forging?
1 A die is made from cast tool steel (which resembles a mould) and this is secured to the top of an anvil.
2 A ram is also equipped with a die that resembles a mould.
3 The metal ‘billet’ to be forged is heated to above its recrystallisation temperature. This stops the product from work hardening as it cools, which would make it brittle.
4 Using tongs, the heated billet is placed by an operator into the anvil die and the hydraulic ram is brought down with force. This makes the hot billet spread around the shape of the die.
5 The ram is lifted and the completed product removed for cooling and finishing.
What does it mean by the recrystallisation temperature of a metal?
The temperature below the melting point shape of the metal at which point it is possible to change the size and shape of the grains that make up the metal
What type of production does wrought iron forging use?
It is suitable for one-off or limited batch production because there is no requirement to make formers or dies to shape the product.
What is the process of wrought iron forging?
1 The wrought iron is heated in a gas or coke-fired forge.
2 It is then shaped by holding it with tings, hammering it over an anvil or using tool such as scroll formers or twisting bars.
What type of production does bending use?
Can be done as a one-off production method. However, in industry where press brakes are used, it is more typically used in large-scale batch production
What is the process of bending?
1 Clamp the stock metal between a matching punch and die.
2 A hydraulic, pneumatic or mechanical brake holds the metal sheet or plate, and lowers the punch to bend the material to shape.
3 Modern press brakes use a device known as a back gauge to accurately position the piece of metal, so that the brake bends the metal in the correct place.
What types of dies used in press brakes are used in bending metals?
V shaped
90 degree
radius
What are the 2 types of rolling?
1 hot rolling
2 cold rolling
What is hot rolling?
When the metal has been heated above its recrystallisation temperature.
What is cold rolling?
When the metal has been heated below its recrystillisation temperature.
What is metal rolling?
A metal forming process in which the stock metal material is passed through sets of rollers to reduce the thickness of the material.
What is the advantage of hot rolling?
It results in material with mechanical properties that are uniform throughout the sample. It will not have any deformation or stresses which could result in a fault in the material.
What is the disadvantage of hot rolling?
The surface is usually coated with carbon deposits, which have to be removed using acid pickling.
Hot rolled materials have a more generous tolerance applied to their dimensions because of the carbon deposits on the surface.
What is the advantage of cold rolling?
It results in a material that has a tighter tolerance because carbon deposits are not formed during the rolling process. The surface finish of cold rolled metal is therefore much better.
What type of products does cold rolling metal produce?
home appliances, filing cabinets, chairs, steel drums, electrical cabinets, containers, saucepans
What are the 4 metal redistribution processes?
1 sand casting
2 die casting
3 investment casting
4 low temperature pewter casting
What type of production does sand casting use and why?
one-off and batch production due to the process being slow and labour intensive and the moulds are only single use
What is a disadvantage of sand casting?
Sand casting does not give a very high-quality surface finish because the molten metal will pick up the grainy texture of the sand.
What is the process of sand casting?
1 A ‘pattern’ is made, usually from wood. This is a replica of the item that will be cast, and it is placed in the bottom of a steel box called a ‘drag’. The drag is then filled with sand which is packed or rammed in tight around the pattern and levelled.
2 The drag is turned over and a second box called the ‘cope’ is clamped into position over the top of the drag. The top half of the pattern is placed into this to mate with the bottom half of the pattern. Wooden stakes are positioned in the cope. These will form the sprue or runner and riser later in the process.
3 Sand is packed into the cope around the runner, riser and pattern. A small depression is made on the surface around the spruce to make a pouring basin.
4 The cope and drag are separated, and the stakes and patterns are carefully removed. Connecting channels are cut to join the sprue to the pattern cavity, and from this to the riser. The cope and drag are then reassembled and the mould is ready for pouring to begin.
5 Small metal spikes may be inserted and removed to make vent holes. These will allow gases from the casting process to escape.
6 The molten metal is poured into the pouring basin. It flows down the runner, into the cavity. When the cavity is full, the molten metal flows up the riser, indicating to the worker that the cavity is full. Once cool, the sand is removed to reveal the casting. The runner, channels and riser are cut off with a hacksaw and the casting is ready for machining.
What metals are used in die casting?
aluminium
alloys of aluminium
zinc-based alloys