ME3162/ME3162E
NATIONAL UNIVERSITY OF SINGAPORE
ME3162/ME3162E – MANUFACTURING MANUFACTURING PROCESSES
(Semester I : AY2009/2010)
Time Allowed : 2 Hours
INSTRUCTIONS TO CANDIDATES:
1.
This examination paper contains ELEVEN (11) questions and comprises TEN (10) printed pages.
2.
Answer ALL questions.
3.
This is an OPEN-BOOK EXAMINATION.
PAGE 2
ME3162/ME3162E
QUESTION 1
Figure 1
The food container shown on the right in Figure 1 is produced by deep drawing from 1 mm stainless steel sheet. Its diameter is 145 mm and its height is 64 mm. Calculate the smallest number of drawing operations required to produce it. Assume the cup corner radii are relatively sharp (d/r >> 20) and there is no ironing. Neglect friction, and progressively use Crane’s constants of 40%, 25%, 15% and 10%, respectively. (6 marks)
If the yield strength of the material is 250 MPa, what is the force needed for the first draw? (3 marks)
Calculate the punch and die sizes required to produce the blank (taking the allowance as 50 microns and clearance as 10% of thickness). (4 marks)
On the left of the picture is the carrier, made of the same material of thickness 1 mm and width 20 mm. How is it produced and joined? Ignore the latch on top. (8 marks)
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ME3162/ME3162E
QUESTION 2
Figure 2
(i)
The base of an electric steam iron (Figure 2) is simply a 2 mm aluminium plate with 3 mm holes for the steam to pass through. If the holes have to be dimensionally accurate, which one of these processes would you use? (a) Drilling (b) EDM (c) Piercing with a punch (d) Die cast the plate with the holes in situ (3 marks)
(ii)
If the holes do not need dimensional accuracy, which one of these processes would you use? (a) Drilling (b) EDM (c) Piercing with a punch (d) Die cast the plate with the holes in situ (3 marks)
(iii)
If the holes are only 0.1 mm diameter, which one of these processes would you use? (a) Drilling (b) Piercing with a punch (c) EDM (d) Die cast the plate with the holes in situ (3 marks)
(iv)
If the iron is just an ordinary iron with no holes for steam to pass through, which one of these processes would you use to manufacture the aluminium plates? (a) Rolling and stamping out the shapes (b) Die casting (c) Machining from a sheet (d) Investment casting (3 marks)
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ME3162/ME3162E
QUESTION 3
Figure 3
Which of the following is the reason why Gillette stainless steel razor blades (shown in Figure 3) must be attached by laser spot welding and not other methods? (a) (b) (c) (d)
The blades are too small for joining by other processes Stainless steel is a very good conductor of electricity High accuracy is needed for the weld positions The blades are disposable, so the weld joints need not last long (3 marks)
QUESTION 4
Figure 4
The dental equipment shown in Figure 4 is made of low carbon stainless steel. Which one of the following is the most likely process for manufacturing them? (a) (b) (c) (d)
Heat the metal, extrude through a hexagonal die, bend to shape Heat the metal, forge to shape using progressive forging dies, trim flash Cold draw the extruded bar through progressive dies, heat the material to above recrystallisation temperature, bend to shape while hot Cold draw the extruded bar through progressive dies, bend to shape at room temperature (3 marks)
PAGE 5
ME3162/ME3162E
QUESTION 5
Figure 5
(i)
Each panel of the cast iron filigree decorative structure of this food centre at Lau Pa Sat (shown in Figure 5) is cast in one piece and not joined from several smaller cast iron components. Which are the main reasons? (a) Joining is too time consuming and the melting point of cast iron is too high (b) Cast iron cannot be welded properly and the melting point of cast iron is too high (c) Joining is too time consuming and cast iron cannot be welded properly (d) Joining is too time consuming and the dimensional tolerances are not important (3 marks)
(ii)
Why is it not made of PVC (polyvinyl chloride)? (5 marks)
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ME3162/ME3162E
QUESTION 6
Figure 6
Figure 6 shows a lectern used for giving speeches. It is made of acrylic, a transparent thermoplastic. Which methods of joining the acrylic plates are suitable? (a) (b) (c) (d)
By heat seal or by adhesive By solvent or by friction welding By heat seal or by friction welding By solvent or by adhesive (3 marks)
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ME3162/ME3162E
QUESTION 7
Figure 7
(i)
The dustpan shown in Figure 7 is made of polypropylene. What is the most suitable method for manufacturing it is bulk? (2 marks)
(ii)
How would you manufacture the vertical handle if it were hollow PVC (polyvinyl chloride)? (2 marks)
(iii)
How would you manufacture the vertical handle if it were hollow aluminium? (2 marks)
(iv)
How would you manufacture the vertical handle if it were hollow mild steel? (4 marks)
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ME3162/ME3162E
QUESTION 8
Figure 8
Figure 8 shows a piston from an engine cylinder. It is made of aluminium. Compare its properties if it were produced by forging and by casting. (4 marks)
QUESTION 9
210 mm diameter and 300 mm long steel shafts are to be machined from bars stocks of 225 mm diameter and 400 mm length using a lathe of 100 KW motor running at an efficiency of 50%. The machining time for both roughing and finishing operations should be completed in 12 min. The specific cutting energy ps, for the work material is 2.73 GJ/m3, and the time taken to load and unload a workpiece is 1min. Select proper cutting speeds, feed rates, depth of cuts, tool materials and type of rake angles for both roughing and finishing operations. (14 marks)
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ME3162/ME3162E
QUESTION 10
In a particular turning operation, the cost of the labour and machine time in resetting a cutting edge is $10.00, the cost of each throw-away insert having eight cutting edges is $12.00, and the cost of the insert holder is $800 and it can be used for 1000 inserts. The initial cost of the lathe was $100,000.00 which is amortized for 6 years. Machine running costs including labour and overheads but neglecting depreciation are estimated at $8.00/hr. The Taylor tool-life equation for this turning process is as follows: vt0.25 = 25 where v is the cutting speed (m/s), and t is the tool life (s). Calculate, for minimum cost conditions, the tool life, in seconds and cutting speed in metres per second, if the machine is to be used on a (a) single-shift, 40 h/wk basis, and (b) double-shift, 80 h/wk basis. Assume 50 working weeks per year. (14 marks)
QUESTION 11 (CHOOSE THE RIGHT ANSWER)
(i)
If aluminium is to be machined in small quantity which of the following tool materials should be economical? (a) (b) (c) (d)
Ceramic Tungsten carbide High speed steel Diamond (2 marks)
(ii)
Which of the following rake angles will should be used to machine hard materials? (a) (b) (c) (d)
– 15 degrees – 5 degrees + 15 degrees + 5 degrees (2 marks)
(iii)
Which of the following statement is correct? (a) (b) (c) (d)
Tool life increases with the increase of cutting speed Tool life decreases with the increase of cutting speed Cutting speed has no influence on tool life None of the above (2 marks)
PAGE 10
(v)
ME3162/ME3162E
Which of the following statement is correct? (a) (b) (c) (d)
Tool life is shorter in intermittent/discontinuous machining Tool life is shorter in continuous machining Tool life is not dependent on type of machining None of the above (2 marks)
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