This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Injection Moulding Process – 2”.
1. Which of the following processes of moulding is widely used for the manufacturing of bottle caps and automotive dashboards?
a) Compression moulding
b) Transfer moulding
c) Injection moulding
d) Jet moulding
View Answer
Explanation: Injection moulding is a manufacturing process which uses thermoplastic and thermosetting plastic materials to make products like bottle caps, automotive dashboard, combs etc. In this process, material is fed into a barrel of high temperature, then by mixing it is forced into a mould cavity where it solidifies and gets hardened.
2. Complex shape of parts or components cannot be formed by the injection moulding process.
a) True
b) False
View Answer
Explanation: Injection moulding is a most common and dominant of all the other plastic processing methods. The process of injection moulding is very versatile and can produce very complex shaped components with the application of multisided moulds. In this process, even components with metal inserts can also be produced.
3. Components from injection moulding process are made very expensive due to the application of very costly equipment.
a) True
b) False
View Answer
Explanation: In injection molding process, dies are costly to produce parts; the dies can be used to form thousands of parts at very faster rate, so that cost of components reduces that implies this method is very economical for large scale production which can produce any simple or complex products in abundant amount.
4. The three mould technique is generally preferred than the two mould technique in injection moulding process.
a) True
b) False
View Answer
Explanation: The design in three mould technique has some advantages that it allows more even distribution of melt into the sides of mould cavity. And also provides more automation to the moulding process in comparison with two mould technique. So, the three mould technique is always preferred than the two mould technique in injection moulding process.
5. Which of the following cooling systems is used in injection moulding process to increase solidification rate of components made?
a) Air jet cooling system
b) Water cooling system
c) Cooling with free convection
d) Cooling with fins
View Answer
Explanation: The cooling system is made by including some passages in the mould walls that are usually connected to an external pump. Cool water is circulated through the passages to extract heat from the hot polymers or plastics components made in the injection moulding process. This cooling system increases the solidification rate which basically reduces the production time.
6. The moulding directions in injection moulding can affect the cost of equipments used in the process.
a) True
b) False
View Answer
Explanation: The moulding directions involved in injection moulding process basically determines number of cams or inserts which to be used in the process. And if the number of inserts used is more, then the cost involvement will also be more. The moulding is always made in such a way to optimize number of cams as well as the cost.
7. The flow of plastic in the mould cavity is more proper and smooth if the thickness of the component made is very small.
a) True
b) False
View Answer
Explanation: In injection moulding process, if the component thickness is very small, then the plastic flow is prevented due to high friction. The flow can also be restricted if the gate is very far away from the features of the geometry, or a obstruction in path of flow may also result in prevention of flow.
8. Shrinkage of the plastic parts in mould cavity can results in generation of sink holes in the plastic.
a) True
b) False
View Answer
Explanation: Shrinking of plastic in mould cavity can result sink holes which are a type of defect that can ruin the product. To avoid such defects, cross-sectional thickness should be maintained uniformly throughout the component. And ribs and gussets must be used which provides mechanical strength to the parts made in the mould.
9. A heavy surface finishing is always required for components made in injection moulding machine.
a) True
b) False
View Answer
Explanation: Injection moulding is very advantageous when it needs to manufacture intricate parts in abundant quantity. In injection moulding machine, components are often moulded directly in the machine with surface finish and other features like color thereby excluding the secondary finish, which also excludes the cost of further machining.
10. In injection moulding process, ribs are generally provided for the reinforcement to avoid sink marks from the component.
a) True
b) False
View Answer
Explanation: In order to have reinforcement, ribs can be used which mainly avoid the problem of marks formed on the parts. Reinforcing ribs are generally provided perpendicular to the parting line and made thinner than the mould walls. It is always recommended that the thickness of the ribs should lie between 40% and 60% of wall thickness.
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