4.types of manufacturing system and layouts


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4.types of manufacturing system and layouts

  1. 1. Mass production Batch production Job shop Project
  2. 2. Mass production Mass production is wrongly equated with heavy production meant for teeming millions. However mass production is a concept. It believes in break up of task into its simplest possible elements. These elements are then grouped as per production norms. Concept of assembly line is used for mass production. On assembly line, the material moves continuously at a uniform speed. It reaches the various work stations, where a portion of work is done.
  3. 3. Mass production: suitability  Mass production refers to a large quantity of production with standardized products having less variety. Ideally, it should be a single standard product manufactured on a continuous basis over a period of time.
  4. 4. Merits There is a smooth flow of material There are small WIP Production time as a whole is short Closely spaced WS’s reduce material handling No expertise necessary to operate the system. Less training cost PPC is simple Less storage space is required
  5. 5. Demerits One machine failure results in a stoppage of whole line following it. Maintenance is challenging Assembly lines are not flexible Great changes in layout are necessary when product line changed Production speed is determined by slowest machine. It requires general rather than specific supervision More capital required because of duplication of machines
  6. 6. Line balancing method: Kilbridge and wester method (i) Draw the precedence diagram of work elements. Draw columns taking the starting elements first and then the succeeding events. (ii) Select CT which is feasible (iii) Assign work elements to WS. Sum of elemental times should not exceed CT while doing so. Proceed from col.i to col. ii and so on. Break intra column tie by using the norm of minimum number of predecessors. (iv) Deduct assigned work elements from the total number of elements. Repeat step 3.
  7. 7. (v) If WS time is more than CT, identify the work element due to which this happens and carry forward to next WS. (vi) Repeat steps 3 to 5 till all elements are fully assigned. Now we want to balance line with CT=8
  8. 8. 2 3 ❷ ❸ 4 4 ❶ ❻ 2 5 ❹ ❺
  9. 9. WORK ELEMENT NO. OF PREDECESSORS TIME 1 0 4 2 1 2 3 2 3 4 1 2 5 2 5 6 5 4
  10. 10. Station Element T Station sum Idle time I 1 4 4 2 2 2 2 II 4 2 2 5 5 5 1 III 3 3 3 6 5 5 0
  11. 11. Line efficiency= total station time CT x No. of WS’s = 21 8 x 3 = 87.5% Balance delay= idle time of all stations x 100 available working time of all stations = 3/21 x 100= 14.29%
  12. 12. Problems and prospects of mass production Variable work element times Break down at WS’s Multi product lines Machining centres Industrial robots
  13. 13. Batch production  Batch production is resorted to when a variety of products are to be made and the volumes are not large enough to demand a separate line for each product. In this method, general machines are used to turn to different products. Here the rate of production exceeds rate of demand. Hence many products are produced
  14. 14. Merits Fewer machines are necessary Specialized supervision is possible Not so capital intensive Low investment in machines Job satisfaction for the operatives
  15. 15. Demerits Material handling is costlier since the flow is longer and irregular PPC is elaborate Production time is longer generally WIP ties up large capital and space. Skills of a higher order are necessary considering the variety.
  16. 16. Economic lot size  There are two types of cost involved (i) Carrying cost: The cost which we need to bear in case we have purchased raw material in big lots. E.g. insurance, storage, godown rent, interest on money invested (ii) Buying cost: The cost which we need to incur whenever we place an order. E.g. transportation cost, and we also do not get the benefit of bulk discount
  17. 17. now economic lot size is that size where our cost is minimum with a specific combination of two. We calculate the specified qty using formula and that combination proves the cheapest out of all combination. Hence our cost is reduced.
  18. 18. Set up cost  Batch production involves a set up cost, each time a batch is produced. Set up cost is roughly equivalent to the ordering cost per order. It consists of engineering cost of setting up the production lines or machines.