October 22, 2007

Operations Management Lesson 8 Exercise

Create a new entry in your Blog using the subject ‘Operations Management Lesson 8 Exercise’.
Process map a process (or use one you have already compiled earlier) and assess each process step to decide whether or not each step adds value from a Lean thinking perspective. Pay particular attention to delays and to quality checking points. Assess the throughput efficiency of the process. Is a demand-pull or Kanban system used to control flow?

For this blog, I’ve chosen a little bit funny process: the cooking and table serving of pizza in a restaurant.

Last night I went to dinner with friends, in a famous “Pizzeria” in Rome. It’s a very big restaurant with about 200 seats and a high turnover of clients.

I was attracted by the way in which they prepared the pizza and how they bring it to the table.

In my opinion, it was a clear example of a “pull approach” system.

Referring to the previous lesson, the method used to carry out the orders is first in first out (FIFO).

Let’s explain how the process works.

blog lesson8 img1


In the Kitchen of the restaurant, behind the counter there are two pizza chefs:

  • pizza chef 1 is dedicated to stretch the dough pizza
  • pizza chef 2 is dedicated to cover the dough pizza with various toppings (Tomato, mozzarella cheese, sausage,..).

Pizza chef 1 takes about 20 seconds for each dough pizza, while pizza chef 2 is a little bit slower and takes about 30 second for each; as they work batches of 8 pizzas at a time, the first chef takes 120 seconds to complete is job while the second one, 240 seconds plus 30 seconds more to put the pizzas in the oven. The cooking time is about 180 seconds. Pizza chef 1 is also in charge for removing pizza from the oven, and placing it on plates, which are then taken and delivered by waiters at tables.

For this map process is used the lean approach, in fact the pizza chef 1 prepares the pizza dough and place them on his right, in an area close to his colleague, then, when the pizza chef 2 picks them and leaves the area empty he gives to the Chef1 the order to produce eight more dough (the area between the two pizza chefs is similar to the colored square, kanban cases).

Let’s analyse the transition between the step 4 and 5, also in this case they use a method similar to kanban.

Close to the oven there is a queue of 8 plates: the pizzas are put on the plates, then they are taken by waiters and delivered to the restaurant's customers; pizza chef 2 do not put more pizzas in the oven until the dishes are taken by waiters, since if for any reason the waiter could not deliver the pizzas in 4 minutes, the pizza left in the oven would be burned. In this case the signal to produce more pizza is the empty dishes.

Let’s analyse now the stock of the ingredients that are put on top of pizzas. In this case they use the two-bin system (which is similar to the Kanban method), in the warehouse there are two shelves, on which are stored the ingredients, (each shelf includes three days of supply). The ingredients are always taken from a single shelf (shelf1), when an ingredient on a shelf1 ends this is the signal that the ingredient must be re-ordered, during the reorder period the ingredient will be moved from shelf 2 on shelf 1.

It is important to say that the implementation of this system has been decided by the pizza chef, based on his past working experience. This enabled him to increase the number of pizzas produced, going to meet the growing demand for pizza.

Zoe Radnor (2007); «Operation Management »;Warwick Business school

N. Slack, S. Chsmbers, R. Johnston, A. Betts; «Operation and Process Management »; Prentice Hall

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