UNIVERSITI MALAYSIA PAHANG
BMM3643 (Sem II 2012/13)
1. a) What distinguishes machining from other manufacturing processes? b) What is a machining center? c) How important is the control of cutting-fluid temperature in operations performed in machining centers? Explain. (8 marks) * Answer. a) In machining, material is removed from the workpart so that the remaining material is the desired part geometry. b) A machining center is a CNC machine tool capable of performing multiple types of cutting operations involving rotating spindles (e.g., milling, drilling); the machine is typically equipped with automatic toolchanging, pallet shuttles to speed workpart changing, and automatic workpart positioning. c) The control of cutting-fluid temperature is very important in operations where high dimensional accuracy is essential. As expected, the fluid heats up during its service throughout theday (due to the energy dissipated during machining), its temperature begins to rise. This, inturn, raises the temperature of the workpiece and fixtures, and adversely affects dimensionalaccuracy. Temperature-control units are available for maintaining a constant temperature in cutting-fluid systems.
2. a) What are the primary considerations in tool selection? b) What is the advantage of a helical-tooth cutter over a straight-tooth cutter for slab milling? c) What are the consequences if a cutting tool chips? (8 marks) * Answer. a) Primary considerations in tool selection are i) What material is going to be machined ii) what process is going to be used, iii) what are the cutting speeds, feeds, and depths of cut needed, iv) what is the tool material, v) what are lubricants going to be used. b) Helical toothed cutters enter the workpiece progressively.