Polymer Manufacturing Processes

Question 1

Injection moulding

Answer 1

Injection moulding is a manufacturing process in which a molten material is injected into a mould to shape a product

Question 2

Injection Moulding Advantages (3)

Answer 2

Quick, low labour cost, high output

Question 3

Blow Moulding

Answer 3

Blow molding is the process of forming a molten tube (parison or preform) of thermoplastic material and placing the parison or preform within a mold cavity and inflating the tube with compressed air, to take the shape of the cavity and cool the part before removing from the mold. Any hollow thermoplastic part can be blow molded.

Question 4

Blow Moulded Items (4)

Answer 4

Industrial bulk containers
Car under hood parts
Toys
Medical supplies

Question 5

Extrusion Blow moulding stage 1

Answer 5

Plastic is melted and extruded into a hollow tube (parison)

Question 6

Extrusion blow moulding stage 2

Answer 6

Mould closes and the parison is gripped in place

Question 7

Extrusion blow moulding stage 3

Answer 7

Air is blown into the parison which then inflates it to the container, bottle, part etc.

Question 8

Extrusion blow moulding stage 4

Answer 8

After the plastic has cooled the mold is broken and the part ejected

Question 9

Extrusion blow moulding stage 5

Answer 9

Any excess material is removed from the mould be trimming with a knife

Question 10

Why use blow moulding

Answer 10

To create a hollow plastic part which has thin walls

Question 11

Injection blow moulding

Answer 11

In this process, The hot material, still on the core pin, is then indexed to the blow molding station where it is blown into a bottle and allowed to cool. The bottle is then indexed to the next station and ejected.

Question 12

Injection blow moulding vs extrusion blow moulding

Answer 12

Injection blow moulding adds more physical detail like more precise detail in the neck and finish (threaded) area than extrusion blow molding.

Question 13

Stretch blow moulding

Answer 13

Like injection blow moulding, the material is injected. It is then presented to the blow mold in a conditioned state, but before final blowing of the shape, the preform is stretched in length as well as radially.

Question 14

Stretch blow moulding uses (2)

Answer 14

To create wide mouthed jars

Used to make speciality products where high production rates are not required

Question 15

Blow moulding vs injection moulding similarities (2)

Answer 15

Both are high production

Create cost effective plastic parts and products

Question 16

Blow moulding vs injection moulding differences (2)

Answer 16

parts made by injection molding and parts made by blow molding is that injection molding creates solid parts, while blow molding creates hollow parts.
Injection moulding makes rigid walls whereas blow moulding makes smooth walls for things like bottles

Question 17

Vacuum forming

Answer 17

where a sheet of plastic is heated to a forming temperature, stretched onto a single-surface mold, and forced against the mold by a vacuum.

Question 18

Vacuum forming stage 1

Answer 18

place the mold in the machine then lower it down into the machine to prepare it for its function.

Question 19

Vacuum forming stage 2

Answer 19

place the material on the frame and then clamp omit down so it is locked in place and cannot move

Question 20

Vacuum forming stage 3

Answer 20

place the heater over the thermo plastic for 30sec or any other specified time so it is springy and not rigid

Question 21

Vacuum forming stage 4

Answer 21

remove the heater and pull the mold onto the plastic so it begins to take shape

Question 22

Vacuum forming stage 5

Answer 22

Suck the air out from below the mold and plastic so the plastic fills the mold and takes shape

Question 23

Vacuum forming stage 6

Answer 23

Lower down the platen then remove the clamps holding the plastic down

Question 24

Vacuum forming stage 7

Answer 24

Remove the plastic from the frame which should be easier because of the rake angle in place on the mold an you have your finished product

Question 25

Vacuum forming products (6)

Answer 25

• Baths & Shower Trays
• Yoghurt Pots
• Boat Hulls
• Machinery Guards
• Refrigerator Liners
• Sandwich Boxes

Question 26

Disadvantages of injection moulding (3)

Answer 26

High initial tooling and machinery cost.
Part design restrictions.
Small runs of parts can be costly

Question 27

Injection moulding stage 1

Answer 27

Clamping - the two halves of the mold must first be securely closed by the clamping unit. Each half of the mold is attached to the injection molding machine and one half is allowed to slide. The hydraulically powered clamping unit pushes the half’s together.

Question 28

Injection moulding stage 2

Answer 28

Injection - The raw plastic material, usually in the form of pellets, is fed into the injection molding machine. During this process, the material is melted by heat and pressure. The molten plastic is then injected into the mold very quickly and the buildup of pressure packs and holds the material. The amount of material that is injected is referred to as the shot.

Question 29

Injection moulding stage 3

Answer 29

Cooling - The molten plastic that is inside the mold begins to cool as soon as it makes contact with the interior mold surfaces. As the plastic cools, it will solidify into the shape of the desired part. However, during cooling some shrinkage of the part may occur. The packing of material in the injection stage allows additional material to flow into the mold and reduce the amount of visible shrinkage.

Question 30

Injection moulding stage 4

Answer 30

Ejection - After sufficient time has passed, the cooled part may be ejected from the mold by the ejection system, which is attached to the rear half of the mold. When the mold is opened, a mechanism is used to push the part out of the mold. Once the part is ejected, the mold can be clamped shut for the next shot to be injected.

Question 31

Injection moulding products (3)

Answer 31

Plastic bottle caps
Toys
Medical equipment

Question 32

Blow moulding materials (2)

Answer 32

Polyester

Resin