Question 1 (100 marks)
a) An overhead trolley conveyor is configured as a continuous closed loop. The delivery loop has a length of 120 m and the return loop is 80 m. All parts loaded at the load station and are unloaded at the unload station. Each hook on the conveyor can hold one part per time and the hooks are separated by a distance of 4 m. Conveyor speed is 1.25 m/s.
i. Maximum number of parts in the conveyor system,
ii. Parts flow rate; and
iii. Maximum loading and unloading times that are compatible with the operation of the conveyor system?
b) Compute the cycle time and production rate for a single-machine robotic cell for an 8hour shift if the system availability is 90%. Also determine the percent utilization of machine and robot. On average, the machine takes 30 s to process one part. The other
robot operation times as follows:
Robot picks up a part from the conveyor 3.0 s
Robot moves the part to the machine 1.3 s
Robot loads the part onto the machine 1.0 s
Robot unloads the part from the machine 0.7 s
Robot moves to the conveyor 1.5 5
Robot puts the part on to the outgoing conveyor 0.5 s
Robot moves from the output conveyor to the input conveyor 4.0 s
Question 2 (50 marks)
CCA Ltd. is a composite boat manufacturing company based at Gold Coast, Queensland. The manufacturing of a type of family fishing boat has been divided into 5 work elements.
To analyse the efficiency, the production manager performed a work measurement and the recorded element times for the first five cycles are shown in the following table with a performance rating (RF) for each element.
Element Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Performance rating % (RF)
1 1.34 1.68 1.45 1.76 1.52 115
2 2.50 2.75 2.67 2.55 2.45 105
3 3.11 3.22 3.15 4.21 3.38 110
4 4.11 4.23 4.56 4.22 6.42 90
5 5.51 5.43 5.22 5.34 5.55 120
Note: all element times are recorded in hours.
(a) Based on the times observed through five cycles, determine their normal times for the cycles and the normal time for the whole job.
(b) Calculate the standard time, if there is a fatigue allowance of 8 % and a contingency allowance of 7.5%.
(c) If a worker is employed on a 5 day, 37.5 hour/week with 1.5 hours per day for breaks, how many workers are needed for a daily production of 25?
Question 3 (50 marks)
(a) Briefly define the two basic types of inspection and explain the difference between inspection and quality control testing.
(b) Who are the internal customers of a business? And why are they important from a quality perspective.
(c) What are the three primary technical tools used for quality control and improvement.
Question 4 (100 marks)
A proposal has been submitted to replace a group of assembly workers, each working individually, with an assembly line. The following table gives the individual work elements
Element Te (min) immediate predecessors
1 1.0 -
3 0.8 1,2
4 0.3 2
5 1.2 3
6 0.2 3,4
7 0.5 4
8 1.5 5,6,7
The demand rate for this job is 1600 units/week (assume 40 h/week) and the current number of operators required to meet this demand is eight using the individual manual workers.
a) Construct the precedence diagram from the data provided on work elements.
b) Use the (i) Kilbridge and Wester rule and (ii) ranked positional weights method to assign work elements to stations, respectively.
c) What is the balance delay for the solutions?
d) The initial cost to install the assembly line is $2,000,000. If the hourly rate for workers is $50.00/h, will the assembly line be justified using a 3-year service life? Assume 50 weeks/yr. Use a rate of return of 10%.