Question 1: The Tesla Model S, one of the most sought-after luxury cars, is produced in Tesla’s Freemont factory in California. The production process can be broken up into the following sub processes. Stamping: In the stamping process, coils of aluminum are unwound, cut into level pieces of sheet metal, and then inserted into stamping presses that shape the metal according to the geometry of the Model S. The presses can shape a sheet of metal in roughly 6 seconds. Subassembly: The various pieces of metal are put together using a combination of joining techniques, including welding and adhesion. This creates the body of the vehicle. Paint: The body of the vehicle is then moved to the paint shop. After painting is completed, the body moves through a 350 degree oven to cure the paint, followed by a sanding operation that ensures a clean surface. General assembly: After painting, the vehicle body is moved to the final assembly area. Here, assembly workers and assembly robots insert the various subassemblies, such as the wiring, the dash board, the power train and the motor, the battery pack, and the seats. Quality testing: Before being shipped to the customer, the now-assembled car is tested for its quality. It is driven on a rolling road, a test station that is basically a treadmill for cars that mimics driving on real streets. Overall, the process is equipped with 160 robots and 3000 employees. The process produces some 500 vehicles each week. It takes a car 4 days to move from the beginning of the process to the end. Answer the questions below. Part 1. What is the cycle time of the process (assume two shifts of eight hours each and five days a week of operation)? Part 2. What is the flow time? Part 3. How many cars are in the WIP (work in progress) inventory? 1 Question 2: Shangri-La Travels Shangri-La Travels offers the following guided services to tourists looking to vacation in the Himalayas. Service Description Time Resources Available A. Jungle Safari Observe wild animals from the safety of a jeep or elephant. 3 days. 8 guides B. Trekking Trek to an “easy to get to” mountain 5 days 10 guides C. White Water Rafting Paddle down the Himalayan rapids. 2 days 5 guides D. Guided Tours Guided tour across the historic sites of Nepal, Bhutan and Tibet 15 days 10 guides The company offers the following four packages to their customers: 1. Basic: Includes only Jungle Safari (Service A) 2. Basic Plus: Includes Jungle Safari and Trekking (Services A and B). 3. Deluxe: Jungle Safari, Trekking and White Water Rafting (Services A, B and C). 4. Super Deluxe: All four services (A, B, C, and D) Customers of Shangri-La Travels arrive at a constant rate (you can ignore any effects of variability) of 40 customers per month. Of these customers, 18 buy Basic, 4 buy Basic Plus, 8 buy Deluxe and 10 buy Super Deluxe. The mix does not change over the course of the month. Assume that there are 30 days in a month. Also assume that each tourist is assigned to one guide for each individual service, and each guide can only assist one tourist during the course of the service (this may not be an unreasonable assumption if the tourist who treks has to be carried by the guide). All guides are specialized in the service they offer, i.e., it is not possible to move guides from one service to another. A customer who buys an expanded package takes advantage of all services in the package; for example, a customer who buys package#4 (Super Deluxe) participates in all 4 services in the package. 2 Part 1. Calculate the following. Service A Service B Service C Service D Number of customers per month using this service Utilization of guides for each service Part 2. The company is concerned about the relatively low labor utilization of guides, and has decided to reduce the number of guides. Compute the minimum number of guides needed for each service to meet the current demand. Service A Service B Service C Service D Minimum number of guides needed 3 Question 3: An emergency room (ER) is currently organized so that all patients register through an initial check-in process. At his or her turn, each patient is seen by a doctor and then exits the process, either with a prescription or with admission to the hospital. Currently, 55 patients per hour arrive to the ER on the average, 10% of whom are admitted to the hospital. On average, 7 people are waiting to be registered (in Wait Area 1) and 34 are registered and waiting to see a doctor (in Wait Area 2). The registration process takes, on average, 2 minutes per patient. Among patients who receive prescriptions, average time spent with a doctor is 5 minutes. Among those admitted to the hospital, average time is 30 minutes. 10% Admit Wait Area 1 Registration Doctor Wait Area 2 90% Prescription a. On average, how long does an “admit patient” (or, a patient who is admitted to hospital upon exiting ER) spend in the ER? Note a patient enters the ER at Wait Area 1 and exits it after seeing the doctor. b. At least how many doctors are needed to handle the flow of 55 patients per hour? Question 5 Short Answer/calculation: Part 1: Consider a 4-station production line shown below: Number of Machines Activity Time (hours per unit) Station capacity (units/hour) 1 (Head Stamping) 1 2 0.50 2 (Tail Stamping) 2 5 0.40 3 (Rimming) 6 10 0.60 4 (Deburring) 2 3 0.67 Station Note: When there are multiple machines at a stage, the job has to visit only one machine at that stage. For example, a job at Stage 2 has to visit one of two machines and requires 5 hrs. 4 Jobs are loaded on to pallets (or trays) before entering the production process. A job stays on the same pallet through all four steps in the process. Once a job comes out from the last station, the pallet can be cycled back to the first station; this step requires 2.5 hours. How many minimum pallets are required to run the process at the rate of the bottleneck step? Show your work. Part 2 . In the process shown in the figure below, batches of product go through two machines: grinding and packing. Each machine can only be set up when it is not working on a batch. Grinding Packing Setup Time = 20 minutes Setup Time = 30 minutes Run Time = 2 min per unit Run Time = 1 min per unit Which machine is the bottleneck when batch size is 15? 5 Part 3: Sorlini Pasta sells pasta throughout Italy. Which of the following is the strongest evidence that Sorlini Pasta is suffering from the bullwhip effect? Circle the single best choice. a. They hold a considerable amount of inventory, enough to satisfy their average demand for 2 weeks. b. Just before a snow storm in the northern part of the country, sales of pasta increased considerably. c. Sorlini sells both fresh and dry pasta products through different types of retailers. d. The volatility of orders Sorlini receives from its distributors is greater than the volatility of pasta demand at retailers. e. Pasta consumption per capita in southern Italy is higher than in northern Italy. 6
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