The Orange Cake Problem

1. The Orange Cake Problem Answer Guide MGT3303 – Operations Management

2. Questions • Assuming you work alone and follow the instructions above, how long will it take you to bake the cake? Is there any obvious way to shorten the preparation time? • Assume that two people are available, how fast can the cake now be prepared? • Categorise activity as follows: process, cook, cool. How much time is spent on each category? • What type of technology could be used to shorten the preparation time? Distinguish these improvements which do not impact quality of the cake from those that do. • If you were commercialise this cake at a large scale, how would you design the facilities and work to achieve maximum efficiency and volume? MGT3303 – Operations Management

3. Question 1 Assuming you work alone and follow the instructions above, how long will it take you to bake the cake? Is there any obvious way to shorten the preparation time? MGT3303 – Operations Management

4. Question 1 • The problem is to apply the recipe instructions on a timeline • This does not mean adding all the elementary times!! • You have to take advantage of idle times: • When the cake is baking, start preparing the curd • When the orange slices are being poached, start preparing the mix • But you have to respect sequential dependencies • You cannot pour the mix before the orange slices are positioned… MGT3303 – Operations Management

5. Solution • You should find 153 minutes • minor variations (1 to 3 mn) are not much to worry about • Major variations (+ 5mn) should be analysed MGT3303 – Operations Management

6. The First 63 Minutes • Getting the cake ready to bake MGT3303 – Operations Management

7. The Middle 45 Minutes • Cake is Baking • Start preparing the curd MGT3303 – Operations Management

8. The Last 45 Minutes MGT3303 – Operations Management

9. Question 2 Assume that two people are available, how fast can the cake now be prepared? MGT3303 – Operations Management

10. Horizontal Division of Labour • By dividing “similar” tasks (whisk/strain/mix) between several persons, it is possible to compress processing times • Overall time gets down to 147 minutes – only a 6 minutes gain in time! MGT3303 – Operations Management

11. Question 3 Categorise activity as follows: process, cook, cool. How much time is spent on each category? MGT3303 – Operations Management

12. Time Distribution • Why this question? • To better understand where time is spent • To identify where time reduction efforts should be focused MGT3303 – Operations Management

13. Question 4 What type of technology could be used to shorten the preparation time? Distinguish these improvements which do not impact quality of the cake from those that do. MGT3303 – Operations Management

14. Time Improvements • Three categories: • Technology input • Use tools and devices which increase output • Cooling Time • Question whether or not they are necessary? • Human Specialisation • When you prepare the cake several times, tasks which are originally difficult (e.g. slicing the cake in 3) become easy • Concept of a learning curve MGT3303 – Operations Management

15. Technology Input • Oven • A fan oven cooks slower but more evenly • With a conventional oven, cooking time could be brought down to 35 mn • This may have a negative impact on quality? • Puree Preparation • The hand mortar process is tedious • A hand blender does the job better and quicker ( 1 mn instead of 10) MGT3303 – Operations Management

16. Cooling Times • Poached Orange Slices • It is difficult to manipulate the slices when they are hot • But it is feasible with a skilled used of a spatula! • The puree can be blended hot • So, cooling time can be brought down to 2 mn MGT3303 – Operations Management

17. Cooling Times • Cake • It is difficult to cut the cake when it is straight hot out of the oven • Again, experiencing with knifes and how to hold the cake means it is possible to slice the cake when it is still warm. • Reduce the cooling time from 20 mn to 10 mn MGT3303 – Operations Management

18. Cooling Times • Curd • A bit too “runny” when hot, and tends to spread out too fast at the sandwiching time • Cooling time can be reduced to 10 mn, but not much more! MGT3303 – Operations Management

19. Learning Curves • Once the operator is skilled, elementary times are reduced • Note: this works well only when tasks are repeated a large number of time (division) • Slicing the oranges: 2mn • Mix for poaching: 1 mn • Whisk eggs+sugar: 3 mn • Mix dry mix + puree: 2 mn • Grate: 3 mn • Straining poached oranges: skipped altogether as by selecting the right slices and letting the drip a bit save adding liquid later on • Cut the cake in 3: 2 mn • Brush: 3 mn • Sandwich: 3 mn • Top: 1 mn MGT3303 – Operations Management

20. New Process Times • The cake can now be prepared in 86 mn • Better use of parallel processing! MGT3303 – Operations Management

21. Question 5 If you were commercialise this cake at a large scale, how would you design the facilities and work to achieve maximum efficiency and volume? MGT3303 – Operations Management

22. Suggested Layout MGT3303 – Operations Management

23. Why this layout? • Use existing “process centres” between cooking and cooling operations • Note that each of these process centres demand about 10 minutes of work • The curd preparation station takes 10 minutes with 1 worker (per cake) • The finishing station also demands 10 mn / cake • The mix preparation demands 11 mn at two people – shift the tin preparation, layout slices to the poached orange station • Make sense: do not carry the slices • The poached orange station is under-loaded MGT3303 – Operations Management

24. Output? • With this staffing level: • Output is one cake every 10 minutes, or 6 cakes per hour, or 48 cakes a day for an 8 hour working day • For a belt speed of 1 m/mn for the oven conveyor: • Cooking time is 35 mn – so length is 3.5 m • A cake is loaded/emptied every 10 mn • Plenty of space! (only 3.5 cakes in the oven) • 48 cakes per day is not much! • We are a very, very long way from mass production • How could you improve this output? MGT3303 – Operations Management

25. Increasing Output • By applying further the principle of horizontal division of labour: • More operators for more elementary tasks • See assembly line design • Automation • More technology inputs • Special tools, cooking and cooling technology MGT3303 – Operations Management