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Cork Institute of Technology
Bachelor of Engineering (Honours) in Mechanical Engineering- Award
(NFQ Level 8)
Summer 2006
Manufacturing Engineering
(Time: 3 Hours)
Instructions: Answer FOUR questions Answer ONE from each Section Use a separate answer book for each section
Examiners: Mr. M. P. O’Mahony Dr. G. Kelly Dr. M. Woods Mr. D. Fallon Mr. J. E. Hegarty Prof. M. Gilchrist
Section A
Q1. (a) EDM has been widely adopted by toolmakers; Wire EMD for Press Tools, Ram EDM for Plastic injection moulding tools. Discuss the reasons for this and highlight issues that may need to be taken into consideration. (9 Marks) (b) In EDM, what is the purpose of the dielectric and explain why flushing is necessary. What would be the consequences of inefficient flushing? (7 Marks) (c) Compare ElectoChemical Grinding to conventional grinding, explaining the reasons why ECG is the preferred choice for certain processes & why it is unsuitable for others. (9 Marks)
Q2. (a) Laser cutting is increasing being used by industry to make parts from sheet metal. Discuss the reasons for this. (15 Marks) (b) In what circumstances would Abrasive Water Jet cutting be used instead of Laser cutting? (5 Marks) (c) What are the advantages of Electron Beam Welding? (5 Marks)
Section B
Q3. (a) Describe with the aid of diagrams the meaning of the terms (^) relaxation , (^) reconstruction and selvedge , in relation to surfaces of materials. (7 marks) (b) A sample is placed within a vacuum chamber. The surface is contaminated from being under atmospheric conditions. Name and briefly describe TWO methods, which may be used to obtain a clean surface on the sample. (6 marks) (c) A sample of chromium steel is to be analysed. It is to be checked for precipitates of chromium carbide and for contaminants with concentrations as low as 0.005% at its surface. The steel contains 0.30 % C; 0.80% Mn; 8.50% Ni and 18.00% Cr in addition to the iron. The techniques AES, SAM and static SIMS are available for analysis. What information can each of these techniques provide on the sample? What limitations does each technique have for this particular analysis? (12 marks)
Q4. (a) Sketch the Force-distance approach curve for a cantilever of a scanned force microscope approaching a sample. Indicate the regions of attractive and repulsive forces. Also sketch under the relevant regions of the graph the diagrams illustrating deflections of the tip and cantilever. (6 marks) (b) State ONE disadvantage of taking a Sa measurement to characterise a region of a surface. How does a Power Spectral Density plot improve on this? (3 marks) (c) Describe with a diagram the operation of the optical detection system of a scanned force microscope when the tip detects a surface feature. (8 marks) (d) A flat glass reinforced polymer composite material is to be analysed using the Lateral Force Microscopy technique with a Scanned Force Microscope. What property of the glass and polymer is applicable to this imaging technique? Describe with the aid of a diagram, how a 2-D image is obtained by this technique. You should explain the role of the cantilever/tip, the optical imaging system, and the surface property of the glass, in the formation of the image. (8 marks)
(b) Eight polypropelene mouldings are to be molded using the runner layout shown in the figure below. The runners leading directly off the sprue have a diameter of 6mm and the runners leading to the cavities are 5mm in diameter. The gate leading from the runner to the cavity can be can be considered to be rectangular, and is 3mm wide, 2mm deep and 1.6mm long. Calculate the injection pressure at each cavity if the injection pressure at the sprue is 80 MN/m^2 and the flow rate through the sprue is 56.1 x 10 -6^ m^3 /s. State all assumptions used. (15 Marks)
γ [s-1 ] η[Nsm-1]
Characteristics of Polypropelene at 210◦C
Runners φ 6mm
100mm
100mm
100mm
Runners φ 5mm Cavity
Gate 3mm wide 2mm deep 1.6mm long
Sprue
Runners φ 6mm
100mm
100mm
100mm
Runners φ 5mm Cavity
Gate 3mm wide 2mm deep 1.6mm long
Sprue
Section D
Q7. (a) The nature of Material Requirements Planning sometimes results in in-feasible
schedules, when checked against capacity. Discuss in detail how and why this problem occurs and what solution has been put forward by other systems such as Optimised Production Technology. (10 Marks) (b) What is ERP? Discuss how ERP has evolved from MRP and MRPII? (8 Marks) (c) Contrast the Push versus Pull nature of the MRP and JIT approaches respectively. (7 Marks)
Q8. Discuss any three of the following:
(a) Synchronous Manufacturing/Optimised Production Technology. (b) Price break models for Economic Order Quantity. (c) Agile Manufacturing. (d) Inventory costs for items of independent demand. (e) The history of manufacturing: the three revolutions. (25 Marks)
