22.10.2009 IE 301 EXTRA RECITATION 1) The Big Black Bird Company (BBBC) has a large order for special plastic-lined military uniforms to be used in an urgent military operation. Working the normal two shifts of 40 hours, the BBBC production process usually produces 2500 uniforms per week at a standard cost of $120 each. Seventy employees work the first shift and 30 the second. The contract price is $200 per uniform. Because of the urgent need, the BBBC is authorized to use around-the clock production, six days per week. When each of two shifts works 72 hours per week, production increases to 4000 uniforms per week but at a cost of $144 each. a) Did the productivity ratio (in monetary terms) increase, decrease, or remain the same? If it changed, what percentage did it change? b) Did the labor productivity ratio increase, decrease, or remain the same? If it changed, by what percentage did it change? c) Did weekly profits increase, decrease, or remain the same? 2) A large manufacturer of pencil sharpeners is planning to add a new line of sharpeners, and you have been asked to balance the process, given the following work element times and precedence relationships. Assume that cycle time is to be the minimum possible. The work elements can be defined using the following predecessor relations: Work element a b c d e f g h a) b) c) d) e) Immediate Followers b d d g f g h - Length (minutes) 0.2 0.4 0.3 1.3 0.1 0.8 0.3 1.2 Draw the precedence diagram. Assign work elements to stations according to largest candidate rule. Determine the balance delay (percentage of idle time) and line balance efficiency. Compute the hourly rate of output if the line efficiency is 90% Determine how many units of demand can be satisfied in a year assuming that there exists 420 minute in a shift 11 shifts in a week. f) g) What is the shortest cycle time that will permit use of only two stations? Apply the positional weight heuristic to find a solution for part f. Is it a feasible solution? So, is this cycle time feasible? h) Determine the percentage of idle time (balance delay) and line balance efficiency. i) j) What is the daily output under the arrangement in part g, if the line efficiency is 90%? Determine the hourly production rate that would be associated with the maximum cycle time, if the line efficiency is 100%. 3) The final assembly of personal computers requires a total of 12 tasks. The assembly tasks can be defined using the following predecessor relations: Task 1 2 3 4 5 6 7 8 9 10 11 12 a) b) Draw the precedence diagram. Immediate Predecessors 1 2 2 2 2 3,4 7 5 9,6 8,1 11 Time 12 6 6 2 2 12 7 5 1 4 6 7 Assuming the firm wants to have 32 computers to be produced in a 8 hour-day shift. Considering that the line efficiency is 100%, assign the tasks to workstations in order of greatest following tasks / most follower (Tiebreaker: greatest processing time) c) d) Calculate balance delay and line balance efficiency. Assign the tasks to workstations in order of greatest positional weight, under the same assumption. e) Calculate balance delay and line balance efficiency. 4) The standard time for a manual material-handling work cycle is 2.58 min per piece. The PFD allowance factor used to set the standard was 13%. During a particular 8-hour shift of interest, it is known that the worker lost a total of 53 min due to personal time, rest breaks, and delays. On that same day, the worker completed 214 work units. Determine a) b) c) The number of standard hours accomplished. Worker efficiency. The worker’s performance level is rated to as 115. Is it reasonable to rate the worker’s performance as 115?
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