Question 1

a) A cylindrical feedstock of length = 35.4 cm and diameter = 10cm is subjected to turning using a high speed steel tool. For thistool, n and C values in the Taylor tool life equation are 0.125 and70 m/min, respectively. The cost for hiring an operator and usingthe machine tool are $82 per hour. The tooling cost per edge ofcutting is $5. Loading and unloading the part on to the machinetakes about 4 min, and it takes about 2.5 minutes to change thetool. At a feed rate of 0.25 cm/rev, calculate:

(i) cutting speed for maximum production rate,

(ii) tool life [minutes], and

(iii) cost per unit and total cycle time of a produced part.

b) On a rectangular stock of aluminium alloy [tensile strength =305 N/mm² and yield strength = 215 N/mm²] with dimensions of length= 320 mm and width = 30 mm, peripheral milling is performed on thetop surface. The diameter of the carbide milling tool is 60 mm,with 8 teeth. The milling tool is centred along the workpiecewidth. At cutting speed of 80 m/min, chip load of 0.17 mm/tooth,and a depth of cut of 5 mm, calculate the following:

(i) the time to complete one machining one pass across thesurface, and

(ii) the rate of maximum material removal during this cut.

Question 2

a) List and describe the five processes that cause wear at theinterface of the tool and chip and the interface of tool and workin machining. What are the two major factors which enhance toolwear mechanisms? Explain in detail.

b) List and describe the three main processes that causegrinding wheel wear. Define Grinding Ratio and explain in detail,the relationship between grinding ratio, surface finish, and wheelspeed using a plot.

Question 3

a) In an Electrochemical Machining process, the feedstock ismade of an aluminium alloy (Ultimate Tensile Strength=572 MPa,Tensile Yield Strength=503 MPa). The desired time to machine a hole(?=10 mm) through a 20 mm-thick part is 2.1 min at a feed rate of0.18 mm/s. What are:

(i) the efficiency of the process in %, and

(ii) the current requirement in amps to achieve this machiningtime target?

b) Describe in detail the process of circular sawing with theaid of a freehand sketch. What are the two major mechanisms bywhich circular sawing is achieved and what materials are commonlyused as circular saws of each type?