1

UNIVERSITY OF MALTA

FACULTY OF ENGINEERING

B. ENG (HONS.) YEAR IV

MAY/JUNE 2013 SESSION OF EXAMINATIONS

MFE4210 Introduction to Tool Design and Manufacture 11th June 2013

9.15 11.15 hrs.

This paper contains four questions. You are to answer any three.

N.B. Page 5 will be collected.

Stationary: Use of calculators is allowed.

1. Figure 1 on Page 3 shows an injection mould to manufacture V-belt pulley halves.

a) Explain briefly what type of mould is it? (5 marks)

b) What is the name and main function of component no 11, 13, 19, 21, 30, 31 and 34?

(14 marks)

c) What type of gate is used? Explain briefly advantages and disadvantages of using this

type of gate. (6 marks)

d) Explain briefly the process how the part and sprue are demoulded in this mould type.

(8 marks)

2. Plates with a hole, as shown in Figure 2a on Page 3, are to be injection moulded using a

8-cavity mould.

a) Explain where the part should be gated. (6 marks)

b) Using the drawing on Page 5, sketch the flow pattern of the melt with the gate position

you decided in 2a) and determine the position of possible entrapped air and weld line(s)

(10 marks)

c) If a balanced cavity layout, as shown in Figure 2b on Page 4, is used for this 8-cavity

mould:

2

i. Explain why there is still imbalance (quality variation) despite the balanced cavity

layout. Explain and group the cavities that deliver the same part quality.

(10 marks)

ii. In the very first sampling process, it was determined that some parts were not fully

filled. From which cavities would you expect that the unfilled parts come from?

Give reasons for your answer.

(7 marks)

3. For flange bushings, as shown in Figure 3 on Page 4, a 2-cavity injection mould is to be

designed.

a) Choose a suitable gate position and explain briefly the reasons for your choice.

(6 marks)

b) Select a suitable gate type and give the reasons for your selection.

(6 marks)

c) With regard to the ejection system:

i. What are the five main criteria to design ejection system?

ii. Which values you need to calculate the ejection force?

(9 marks)

d) Sketch the respective mould and include the main components such as ejector pin,

cavity core and also vents if necessary. (12 marks)

4. Thin circular covers, as shown in Figure 4 on Page 4, are also to be manufactured using

injection moulding.

a) Explain briefly what type of gate you would choose and where you would position it.

(6 marks)

b) Sketch and explain two possible methods to eject and two methods to cool such parts.

(10 marks)

c) Considering your answers in a) and b), do you need to add venting channels? Give

reasons for your answer. (5 marks)

d) Sketch the respective mould and also include the main components.

(12 marks)

3

Figure 1: An injection mould for V-belt pulley halves

Figure 2a: Plate with a hole

4

Figure 2b: Runner layout for the part in Figure 2a

Figure 3: Flange bushing

Figure 4: Thin circular cover

5

NAME OF STUDENT: ____________________________ I.D. NO: _______________________

---------------------------------------------------------------------------------------------------------------------------

INDEX NO:__________________