UNIVERSITY OF MALTA

FACULTY OF ENGINEERING

B.ENG.(HONS.) IN MECHANICAL ENGINEERING Year I SEMESTER II

JUNE 2012 SESSION OF EXAMINATIONS

MFE1202 Fundamentals of Manufacturing and Machining 23rd June 2012

9.15-11.15 hours

STATIONARY: ONLY NON PROGRAMMABLE CALCULATORS ALLOWED

This paper contains FOUR questions. You are to attempt THREE questions.

1) a. Define the term lean manufacturing and provide five examples of how this

principle can be practically implemented within a manufacturing facility. (9 marks)

b. Define the term manufacturing capability and provide one example of how manufacturing capability can be assessed or tracked.

(6 marks) c. What is concurrent engineering?

(4 marks) d. The following list states a number of manufacturing-related processes. Provide a

written (with the aid of sketches) description of the principles of operation, typical applications, advantages and disadvantages for TWO of these processes from ANY category.

Conventional machining processes: Milling, Broaching Non-Conventional machining processes: Ultrasonic drilling, water-

jet cutting, Electric Discharge machining Solidification processes: Casting (metals), Injection Moulding

(plastics) Joining processes: CO2 welding, Laser Welding Others: Laser cutting

(14 marks)

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2) a. You have been tasked with planning a grinding operation for a non-hardened

aluminium material. The machining time is more critical than the surface finish requirement. Present recommendations on the following whilst justifying your answers:

i. the grain material ii. the grain size

iii. wheel grade (soft or hard) iv. bond material to be used.

(10 marks) b. Very briefly, how would you adjust the grinding wheel speed and depth of cut

parameters, wheel structure and grain size requirements, should a finishing operation be required to improve the surface finish?

(4 marks) c. What is the role of the bonding material used for the construction of grinding wheels?

(4 marks) d. Consider a turning operation and answer the following questions:

i. List the three primary modes of cutting tool wear. (3 marks)

ii. What are the two principal locations on a cutting tool where tool wear occurs? Provide a simple sketch to illustrate.

(3 marks) iii. Provide a labelled sketch of tool wear growth versus time for one of the wear

mechanisms/locations provided in the previous question. (3 marks)

e. A steel rod is to be turned. The tool life decreases from 80min to 20min due to an increase in cutting velocity from 60m/min to 120m/min. Given that the Taylor tool life equation is VTn = C, determine the cutting velocity when the life of the tool is 40min. Assume that the cutting tool material and geometry, machining conditions and environment, remain constant throughout the different operations.

(6 marks)

3) a. Using a basic sketch describe the orthogonal cutting model.

(5 marks) b. Identify the two forces that can be measured directly during a manufacturing

operation. Furthermore, sketch the force diagram illustrating the six forces involved in orthogonal cutting, together with their resultant force and the rake, friction and shear plane angles.

(10 marks) c. An orthogonal cutting process adopts a rake angle of 10. The chip thickness prior to

cut and after cut are 0.25mm and 0.55mm respectively. Use this information to determine:

i. The shear plane angle ii. The friction angle

iii. The coefficient of friction iv. The shear strain caused during the cut.

(12 marks) d. A continuous chip with a Built up Edge (BUE) is undesirable due to its adverse effect

on workpiece surface finish. Explain this occurrence and provide two examples of how the BUE can be minimised to improve surface finish.

(6 marks)

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4) a. A 40mm blind hole is to be created using a drilling operation. The geometry of the

drill bit can be described by the following parameters: Diameter 18mm, point angle 135. A cutting speed 200mm/s and a feed of 0.3mm/rev are to be used.

i. Determine the cutting time in minutes (5 marks)

ii. Determine the material removal rate in mm3/min (3 marks)

iii. When considering the point angle that has been selected for the cutting operation, would you expect the workpiece to be a soft non-ferrous or harder material?

(2 marks) b. With the aid of diagrams, describe in some detail and with the aid of diagrams the

differences between peripheral milling and face milling (8 marks)

c. Briefly define the term forming when considering the machining of a feature within a workpart geometry. Provide one example of a forming machining operation. (3 marks)

d. A rectangular workpiece of width 80mm and length 350mm is to be machined by a face milling operation in order to remove a depth of 4.5mm from its surface across the whole surface area. A 100mm diameter cutter with four cemented carbide inserts is to be used. The cutting parameters to be employed are as follows: Cutting speed of 3.5m/s, feed of 0.3mm/tooth. Determine the following:

i. Machining time required to complete one pass across the surface (7 marks)

ii. Material removal rate during cutting (5 marks)

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