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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 1 Examinations 2011/
Module Title: Manufacturing Systems
Module Code: MANU 8004
School: Mechanical & Process Engineering
Programme Title: BSc (Honours) Process Plant Technology BEng (Honours) Mechanical Engineering BEng (Honours) Biomedical Engineering
Programme Code: EPPTE_8_Y EMECH_8_Y EBIOM_8_Y
External Examiner(s): Mr K. McCarthy, Mr G. Reilly, Mr G. Clerkin, Dr L. McNamara Internal Examiner(s): Michael P O’Mahony
Instructions: Answer THREE Questions
Duration: 2 hours
Sitting: Winter 2011
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.
(a) Define the following terms in the context of Work Measurement Standard Performance Qualified Worker (8 Marks)
(b) List FIVE headings under which Relaxation Allowances are applied. (5 Marks)
(c) Compare Direct Time Study to Predetermined Motion Time Systems as means of Work Measurement, indicating advantages and disadvantages of each and when one system would be preferred over the other. (10 Marks)
(d) Activity sampling has been used to study the performance of a simple stamping machine. The data is shown in the table: Machine idle 8% Machine being setup 12% Machine operating 65% Machine being cleaned 10% Machine jammed 5% Using the work sampling approach estimate the number of samples which would have to be taken to achieve an accuracy of +/-5% on the “Machine Operating” figure at a 95% confidence interval. If 250 samples were actually taken, what accuracy would be achieve at a 95% confidence interval for each of the above figures. (10 marks)
(a) Explain how Labour Specialization reduces Labour costs. (5 Marks)
(b) A small electrical appliance is to be produced on a single model assembly line. The work content and precedence is listed in Table Q3. The estimated annual demand is is 100,000 units/yr. The line will operate 50wk/yr, 5 shifts/wk, 7.5hrs/shift. Previous experience suggests that the uptime efficiency of the line will be 96% and repositioning time lost per cycle will be 0.08min. (i) Draw the precedence diagram (6 Marks) (ii) Required hourly production rate (2 Marks) (iii) The cycle time per station (2 Marks) (iv) Use the Rank Positional Weight method, obtain a suitable allocation of work elements to work stations in the assembly line. (12 Marks) (v) Calculate the balance delay and balance loss (2 Marks) (vi) Suggest a means of improvements (4 Marks)
Table Q Step Time (min)
Description Steps that must precede 1 0.2 Place frame in work holder and clamp --- 2 0.4 Assemble plug, grommet to power cord --- 3 0.7 Assemble bracket to frame 1 4 0.1 Wire power cord to motor 1, 5 0.3 Wire power cord to switch 2 6 0.11 Assemble mechanism plate to bracket 3 7 0.32 Assemble blade to bracket 3 8 0.6 Assemble motor to brackets 3, 9 0.27 Align blade and attach to motor 6,7, 10 0.38 Assemble switch to motor bracket 5, 11 0.5 Attach cover, inspect & test 9, 12 0.12 Place in tote pan for packaging 11
(a) Define LEAN (5 Marks) (b) List the Steps to making a process Lean (7 Marks) (c) Compare the approach of LEAN against that of OPT (9 Marks) (d) Four Products A, B, C and D are processed on three work centres in sequence WC1, WC2 and WC3. Processing times, material costs and selling prices are shown in Table Q4. The plant operates 52.5 hours per week with costs of €8000 per week, excluding materials. The market will purchase any quantity that the plant can produce , provided that all four products are sold and the weekly output of any one product does not exceed any other by a factor of more than five. Compare the net profit of the plant using :
Traditional maximizing per unit profit and Maximum utilization of bottleneck resource (OPT approach)
Table Q Processing Times (min) Product Selling Price €
Material Costs €
WC1 WC2 WC
A 40 10 12 8 1
B 55 20 8 7 6
C 46 15 10 4 7
D 70 30 15 4 2
(12 Marks)
