Solved: A logistics stone problem - for students and every true logistican

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This is the model solution to the task for the students. 

Before you read the solution try to solve the problem by yourself. And here you get the very good solution in German written by Marius Müller.

The task is described here and Factory Base Tour I: The idea of stones to tracks and Factory Base Tour II: More a about the factory and layouts and a brief powerpoint presentation with layouts.

Try to solve it, then read the spoiler. For everyone who wants to take a quick look. The complete Prsentation . Problem - Solution - Correct calculation

Spoiler BEGIN:

  1. Analysis of the current situation
    1. Create a overall layout with all required subsystems.
      The layouts of relevant subsystems were given to the students. 
      the layout for the logistics stone problem (Blueprint)

    2. Determine the interfaces of the subsystems and their tasks.
      output materials equal input materials
      1. furnace street output: produced iron plates, produced steel, produced stone bricks and stones from local warehouse
      2. central warehouse: storing materials until requested and internal transport
      3. research area: consumes iron plates, steel and stones 
        three subsystems for the logistics stone problem

    3. Calculate the necessary storage space and the material flow for a reference number of sience packages. It is imperative to set a reference value in order to be able to compare results:
      1000 black and 1000 pink 
      1. Use the production tree and calculate the bill of materials. 
        Factoriolab is an easy to use tool for this calculation (always round up) but you have to keep in mind, that we only have stone related products for tracks and walls in focus.
        1. stones: 21,667 total
          here 15,000
        2. steel plates: 8,834 total
          here 5,000
        3. iron plates: 59,500 total
          here 27,500 - 5 x 5000 (for the steel) = 2,500 
        4. orvarall items 90,001 --> here 22,500
      2. necessary storage place (always round up)
        1. calculate the number of places
          1. stones - stacksize 50:  300 storage places
          2. steel plates - stacksize 100: 50 storage places 
          3. iron plates - stacksize 100:  25 storage places
        2. calculate the number of steel chests (48 places). For small numbers we waste space, because we use single-variety storage.
          1. stones: 11 chests
          2. steel plates 2 chetes
          3. sssssironplates 1 chest
      3. measure the transport distances (1 tile = 1m²)
        1. funrace2warehouse: 65 m
        2. movements internal warehouse: 139m + 33m = 172 m
          regardless of where a material is stored
        3. warehouse2research: 58m
          or 36m, this depends on the position of the interface cut
        4. total distance 295m
      4. required transport performance:  6,637,500 items x m
        calculation of the required transport performance

    4. Get the inventory and calculate the used storage space:
      1. stones: 63,849 = 1,277 storage places = 27 steel chests = 4 flow storage channels
      2. steel plates: 163,924 = 1,640 storage places = 35 steel chests = 5 flow storage channels
      3. iron plates: 325,601 = 3,257 storage places = 68 steel chests = 9 flow storage channels
      4. rails: 0

  2. Calculate the consequences of the new situiation.
    plan ofthe new situation
    1000 black and 1000 pink
    1. Use the same calculations as before.
      1. stone bricks: 5.000 need 59 storage places in 2 steel chestes
      2. rails: 10,000 need 100 storage places in 3 steel chests
      3. total items = 15,000
    2. use all stones in the central warehouse and produce rails
      1. with 63,849 stones we can produce 127,698 rails.
      2. the rails need 
        1. stones or rails ist the same
          1,277 storage places = 27 steel chests = 4 flow storage channels
        2. 63,849 steel plates = 639 storage places = 14 steel chest = 2 flow storage channels
        3. 31,926 iron plates =  320 storage places = 7 steel chests = 1 flow storage channel 
    3. all distance are the same
    4. required transport performance: 
      4,425,000 items x m
       
  3. The new situation ist better than the old one 
    1. less space in the warehose
    2. the requirements for the transporsystem are reduced.

      How should the transition to the new situation be designed?

    3. Determine where the temporarily used production machines should be.
      => a good place is at the goods exit of the central warehouse. An easy setup uses a cargo wagon. Place inserters to get the material from the belt. One machine produces iron sticks and two produce tracks. 
      setup of the temporary machines for rail production
      left: by request of the students
      middle: improved version
      right: symmetric and balanced

    4. calculation of the time required and the resources for the production of the rails
      1. time that is needed to manufacture the components for production = 24,333s = 405 minutes (that has to be done beforehand, 100% of the components will be reused)
      2. placing the components using the blueprint ~ approx 5 minutes (depends on players inventory, without bluprint needs more time)
      3. time pick material until begin of produktion (blue belts) =
        130m /  5.625m/s = 23s ~ 0.5 minutes
      4. production time =
        6 full turns of stack filter inserters ~ 0,22s
        + rail production (+ 200%) ~ 0,25 s 
        =>  0,5 s
      5. time from rail production to storing the rails
        1. use 4 channels at the expansion ares of the central warehouse
          186m   /  5.625m/s = 33.1 s ~ 0.5 minutes
        2. a better concept is:
          reuse the 4 channels (with iron plates) close to the rail production
          186m   /  5.625m/s = 52.6 s ~ 1 minute
      6. time that is needed to remove all the stones =
        63,849 stones with 2 filter inserters need 10,642 full turns each 0.433s =
        4,607s = 77 minutes

      8. time for breakdown after end of production ~ 2 minutes
      9. total time ~ 3 + 0.5 + 1 + 77 + 2 = 85.5 minutes
        transition to the new situation

  4. Summarize the results
    1. in the central warehouse we need 21 less steel chests
      this are 3 flow storage channels in this technique
    2. the required transport performance is reduced by 33%
    3. this requires 1:26 h and some manual work (begin-end)

  5. Recommendation for the management of the factory:

    the production of rails should be reengineered

  6. Realisation
      Start in game time: 272:30 h
      End in game time:  274:23 h
      Required time 1:53 h
      Difference to planning: 27,5 min

  7. Explanation
    there are some obvious differences of the planning versus the realisation. But alle of then can´t explain this big dirrerence. 
    1. The automatic supply for stones was not deactivated. The consequence of this was that approx. 4% more rails were produced.
    2. As a result, the storage route was then overloaded. The resulting backlog then hindered the production of the rails.
    3. After I manually stopped the replenishment with stones, it took a while for the backlog to clear.
    4. The realisation of a flowstorage system has the right funktionality but the internal use of insterters is not the best solution.
    5. In the meantime it was not just outsourced quickly. I had to replace slow inserters during the process to get the performance.
    6. The breakdown required 5 min (measured)
Spoiler END

That´s the question:
What is wrong in the calculations?
Your ideas and suggestions are very welcome.

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