ME4261/ME4261E
NATIONAL UNIVERSITY OF SINGAPORE
ME4261/ME4261E – TOOL ENGINEERING
(Semester II : AY2012/2013)
Time Allowed : 2 Hours
INSTRUCTIONS TO CANDIDATES:
1.
This examination paper contains FOUR (4) questions and comprises FOUR (4) printed pages.
2.
Answer ALL FOUR (4) questions.
3.
All questions carry equal marks.
4.
This is an OPEN-BOOK EXAMINATION.
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ME4261/ME4261E
QUESTION 1
(a)
(b)
Clearly state if the following statements are true or false. Give the correct answer if it is found to be false. (i)
For a fixture two tenon must be used and they must be on a single slot on the machine table.
(ii)
Short post may cause jamming and hence use long post during locating a part using the hole.
(iii)
Conical Locators are used to locate from the axis of a cylindrical feature, when the diameter of that feature is not accurate.
(iv)
Fool proofing pin can be used to locate the workpiece so that both improper loading and accurate location can be achieved.
(v)
In a 4-2-1 locating scheme all pins must be fixed except one pin on the primary datum plane.
(vi)
Recess must be provided around the locating pin so that the chips and dirt can be accumulated.
(vii)
During mass production fast acting clamps can be used to secure the workpiece.
(viii)
During the machining of brittle material place the jig plate such that the gap between the workpiece and the plate must be at least of 1 to 1.5 diameter of the hole.
(ix)
For large volume production, plate clamps can be used to clamp more than two workpieces simultaneously.
(x)
Two clamping forces can be directed against each other to ensure that the workpiece is rigidly secured. (15 marks)
A batch of 10 pieces of an Aluminum part to be machined is given in Figure 1. Design a fixture to mill ‘Face C’ of the workpiece. All other operations are completed and assume the missing dimensions. In your proposed solution clearly indicate the supporting, locating and clamping methods. (10 marks)
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ME4261/ME4261E
Face B
Face A
6x dia 18mm PCD 160mm
Face C
Figure 1
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ME4261/ME4261E
QUESTION 2
A batch of 1000 pieces of an Aluminum part to be machined is given in Figure 1. Using neat sketches propose jig(s)/fixture(s) to machine the following features: Operation1: To machine face A of diameter 200mm using a lathe Operation 2: To machine 6 holes of diameter 16 mm having the pitch circle diameter of 160 mm on Face B using a vertical machining centre. All dimensions are in mm. All other operations are completed and assume the missing dimensions. In your proposed solution clearly indicate the supporting, locating and clamping methods. (25 marks)
QUESTION 3
A tungsten carbide single-point cutting tool for rough turning of cast iron (250 BHN) workpiece is to be designed. If the workpiece diameter is D = 150 mm, the feed rate is f = 0.6 mm/rev (1 in = 25.4 mm), the tool height is set 3 mm above workpiece rotation axis, the tool orientation setting angles are G = +15, H = 0 and L = 0, determine the optimum tool rake angle o , optimum tool relief angle o , optimum tool inclination angle , optimum tool side cutting edge angle end s, and optimum tool end cutting edge angle e. (25 marks)
QUESTION 4
A tungsten carbide single-point cutting tool is used for rough turning of a steel workpiece 9 2 (u = 1.1 x 10 N/m ). If the tool angles in tool-in-hand system are o = +5 , o = +6, = 0 , s =+ 20, and e =+ 25, the tool feed rate is f = 1.6 mm/rev, the workpiece diameter is 30 mm, the tool is set 2 mm below the workpiece rotation axis, the tool orientation setting angles are G = 0 , H = 0 and L = +5 , (a)
Calculate the working rake angle oe , working relief angle oe , working inclination angle e , working side cutting edge angle se , and working end cutting edge angle ee, (15 marks)
(b)
Tell and explain whether or not each of the 5 working rake angles are optimum to the cutting process. (10 marks) 3 2 (Note: 1 psi = 6.894 x 10 N/m )
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