An automated car wash serves customers with the following serial process: pre-tr

Question

An automated car wash serves customers with the following serial process: pre-treat, wash, rinse, wax, hand dry. Each of these steps is performed by a dedicated machine except for the hand dry step, which is performed manually on each car by one of 3 workers. The steps of the process have the following processing times: Pre-treat: 1 minute per car Wash: 4 minutes per car Rinse: 2 minutes per car Wax: 3 minutes per car Hand dry: 9 minutes per car If the car wash has a demand of 18 cars per hour, what is the flow rate of the process? (Do not round intermediate calculations. Round your answer to 2 decimal places) 15.00cars per hour a. If the car wash has a demand of 18 cars per hour, what is the b. utilization of the machine that performs the Wax process? 90 percent (Round to nearest integer)

Explanation / Answer

Hand dry operation takes 9 minutes per car and 3 cars can be hand dried simultaneously by 3 workers.

Therefore, average flowtime of the hand dry process = 9 /3 = 3 minutes / car

The Capacity of the process will be determined by the bottleneck activity and the activity with longest flow time will be the bottleneck activity. The activity with longest flow time is WASH which is 4 minutes per Car.

Thus flow rate of the process will be 4 minutes per car or 60 minutes / 4 minutes = 15 cars per hour

FLOW RATE OF THE PROCESS = 15 CARS PER HOUR

Since flow rate of the process at steady state is 15 cars per hour,

Maximum number of possible waxing in line with process capability = 15 waxing per hour

However,

Maximum capacity of the waxing process ( @ 3 minutes/per car ) = 20 cars per hour

Therefore,

Utilization of the machine that performs the waxing process

= Maximum number of possible waxing / Maximum capacity of waxing process x 100

= 15/20 x 100

= 75 %

UTILIZATION OF THE MACHINE THAT PERFORMS THE WAX PROCESS = 75%

Time taken by each customer at a local bank = ( Time out – Time in )

Thus , sum of time taken by 10 customers in local bank ( minutes)

= 8 + 10 + 23 + 18 + 27 + 20 + 7 + 14 + 13 + 29

= 169

Thus , flow time of customers = Sum of time taken by 10 customers / 10 = 169/10 = 16.9 minutes

FLOW TIME OF CUSTOMERS = 16.9 MINUTES

FLOW RATE OF THE PROCESS = 15 CARS PER HOUR

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