The Orange Cake Problem

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The Orange Cake Problem. Answer Guide. 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? - PowerPoint PPT Presentation

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  • The Orange Cake Problem

    Answer Guide

  • QuestionsAssuming 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?

  • Question 1Assuming 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?

  • Question 1The problem is to apply the recipe instructions on a timelineThis does not mean adding all the elementary times!!You have to take advantage of idle times:When the cake is baking, start preparing the curdWhen the orange slices are being poached, start preparing the mixBut you have to respect sequential dependenciesYou cannot pour the mix before the orange slices are positioned

  • SolutionYou should find 153 minutesminor variations (1 to 3 mn) are not much to worry aboutMajor variations (+ 5mn) should be analysed

    Warm UpOven

    1 mn

    SliceOranges

    Mix

    Cook Orange Slices

    Leave to Cool

    TinPrep.

    ArrangeSlices

    Strain

    Puree

    DryMix

    Whisk

    Mix

    Mix

    Pour

    Bake

    Bake

    45 mn

    R

    Leave to Cool

    T

    Mix

    S

    Grate

    Mix

    P

    Leave to Cool

    Bake

    30 mn

    19 mn

    Cut in 3

    Brush

    Sandwich

    Top

    153 mn

    63 mn

    45 mn

  • The First 63 MinutesGetting the cake ready to bake

    Warm UpOven

    1 mn

    SliceOranges

    Mix

    Cook Orange Slices

    Leave to Cool

    TinPrep.

    ArrangeSlices

    Strain

    Puree

    DryMix

    Whisk

    Mix

    Mix

    Pour

    63 mn

  • The Middle 45 MinutesCake is BakingStart preparing the curd

    Bake

    Bake

    45 mn

    Mix

    S

    Grate

    Mix

    P

    19 mn

  • The Last 45 Minutes

    R

    Leave to Cool

    T

    Leave to Cool

    Bake

    Cut in 3

    Brush

    Sandwich

    Top

    45 mn

  • Question 2Assume that two people are available, how fast can the cake now be prepared?

  • Horizontal Division of LabourBy dividing similar tasks (whisk/strain/mix) between several persons, it is possible to compress processing timesOverall time gets down to 147 minutes only a 6 minutes gain in time!

    SliceOranges

    Mix

    Cook Orange Slices

    Leave to Cool

    TinPrep.

    ArrangeSlices

    Strain

    Puree

    DryMix

    Whisk

    Mix

    Mix

    Pour

    Bake

    Bake

    45 mn

    Warm UpOven

    R

    Leave to Cool

    T

    Cut in 3

    Brush

    Sandwich

    Top

    Mix

    S

    Grate

    Mix

    P

    Leave to Cool

    Bake

    1 mn

    30 mn

    23 mn

    147 mn

    57 mn

    45 mn

  • Question 3Categorise activity as follows: process, cook, cool. How much time is spent on each category?

  • Time DistributionWhy this question?To better understand where time is spentTo identify where time reduction efforts should be focused

  • Question 4What 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.

  • Time ImprovementsThree categories:Technology inputUse tools and devices which increase outputCooling TimeQuestion whether or not they are necessary?Human SpecialisationWhen you prepare the cake several times, tasks which are originally difficult (e.g. slicing the cake in 3) become easyConcept of a learning curve

  • Technology InputOvenA fan oven cooks slower but more evenlyWith a conventional oven, cooking time could be brought down to 35 mnThis may have a negative impact on quality?Puree PreparationThe hand mortar process is tediousA hand blender does the job better and quicker ( 1 mn instead of 10)

  • Cooling TimesPoached Orange SlicesIt is difficult to manipulate the slices when they are hotBut it is feasible with a skilled used of a spatula!The puree can be blended hotSo, cooling time can be brought down to 2 mn

  • Cooling TimesCakeIt is difficult to cut the cake when it is straight hot out of the ovenAgain, 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

  • Cooling TimesCurdA bit too runny when hot, and tends to spread out too fast at the sandwiching timeCooling time can be reduced to 10 mn, but not much more!

  • Learning CurvesOnce the operator is skilled, elementary times are reducedNote: this works well only when tasks are repeated a large number of time (division)Slicing the oranges: 2mnMix for poaching: 1 mnWhisk eggs+sugar: 3 mnMix dry mix + puree: 2 mnGrate: 3 mnStraining poached oranges: skipped altogether as by selecting the right slices and letting the drip a bit save adding liquid later onCut the cake in 3: 2 mnBrush: 3 mnSandwich: 3 mnTop: 1 mn

  • New Process TimesThe cake can now be prepared in 86 mnBetter use of parallel processing!

    S.O

    M

    Cook Orange Slices

    C

    TinPrep.

    ArrangeSlices

    P

    DryMix

    Whisk

    Mix

    Mix

    Pour

    Bake

    35 mn

    Warm UpOven

    R

    Leave to Cool

    T

    Cut in 3

    Brush

    Sandwich

    T

    Mix

    S

    Grate

    Mix

    P

    Leave to Cool

    Bake

    86 mn

    1 mn

  • Question 5If you were commercialise this cake at a large scale, how would you design the facilities and work to achieve maximum efficiency and volume?

  • Suggested Layout

    Poached Orange Station

    SlicingandMixing

    TinPrep

    Cook

    Mix Preparation(Dry+Puree+Pour)

    Oven Conveyor Belt

    Cooling Conveyor Belt

    FinishingStation

    Cutting& Sandwiching

    Cook

    Prep.

    Curd Preparation Station

    Cool

    ToPackaging

  • Why this layout?Use existing process centres between cooking and cooling operationsNote that each of these process centres demand about 10 minutes of workThe curd preparation station takes 10 minutes with 1 worker (per cake)The finishing station also demands 10 mn / cakeThe mix preparation demands 11 mn at two people shift the tin preparation, layout slices to the poached orange stationMake sense: do not carry the slicesThe poached orange station is under-loaded

  • 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 dayFor a belt speed of 1 m/mn for the oven conveyor:Cooking time is 35 mn so length is 3.5 mA 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 productionHow could you improve this output?

  • Increasing OutputBy applying further the principle of horizontal division of labour:More operators for more elementary tasksSee assembly line design AutomationMore technology inputsSpecial tools, cooking and cooling technology