Question

a) A workpiece (φ-75 mm, 1 275 mm) is machined using turning at a feed rate of 0.25 mm/rev. At a cutting speed- 3.5 m/s, the turning tool is ineffective after machining 3 parts, and at a cutting speed = 2.5 m/s, the turning tool is effective for producing 20 parts. Calculate the Cutting Speed that will allow 30 parts to be machined between tool changes [20 marks] b) An aluminium alloy workpiece (tensile strength - 325 N/mm2 and yield strength-275 N/mm2) has dimensions of length -275 mm and width- 32 mm. Peripheral milling is performed on top surface is performed using an 8-teeth carbide milling tool with φ-60 mm, centred with respect to the width of the workpiece. At cutting speed of 96 m/min, chip load of 0.16 mm/tooth, and a 6 mm deep cut, calculate: (i) Time to complete one machining pass across the surface (ii) Rate of maximum material removal for this cut. [20 marks] c) A workpiece (length-25 cm and φ-8 cm) is subjected to turning using a cemented carbide tool. For this tool, n and C values in the Taylor tool life equation are 0.125 and 500 m/min, respectively. The hourly rate for combined operator and machine time is $72 per hour. The tooling cost per edge of cutting is $8. Loading and unloading the part on to the machine requires 2.4 min, and it takes about 2.6 min to change the tool. At a feed rate of 0.28 cm/rev, calculate: (i) Cutting speed that will result in maximum production rate, (ii) Tool life in minutes (iii) Cost per unit and total cycle time of 1 produced part [30 marks]

Answer 1

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