Cellular Manufacturing Group Technology - ADDVALUE - Nilesh Arora

1. “Cellular Manufacturing” by Best Performing Consulting Organization AddingValueInTotality!!

2. ORIGINS • FLANDERS’ PRODUCT ORIENTED DEPARTMENTS FOR STANDARIZED PRODUCTS WITH MINIMAL TRANSPORTATION (1925) • SOKOLOVSKI/MITROFANOV: PARTS WITH SIMILAR FEATURES MANUFACTURED TOGETHER

3. BASIC PRINCIPLE • SIMILAR “THINGS” SHOULD BE DONE SIMILARLY • “THINGS “ • PRODUCT DESIGN • PROCESS PLANNING • FABRICATION &ASSEMBLY • PRODUCTION CONTROL • ADMINISTRATIVE FUNCTIONS

4. TENETS OF GROUP TECHNOLOGY • DIVIDE THE MANUFACTURING FACILITY INTO SMALL GROUPS OR CELLS OF MACHINES (1-5) • THIS IS CALLED CELLULAR MANUFACTURING

5. SYMPTOMS FOR RE-LAYOUT • Symptoms that allow us to detect the need for a re-layout: • Congestion and bad utilization of space. • Excessive stock in process at the facility. • Long distances in the work flow process. • Simultaneous bottle necks and workstations with idle time. • Qualified workers carrying out too many simple operations. • Labor anxiety and discomfort. Accidents at the facility. • Difficulty in controlling operations and personnel.

6. What is Group Technology (GT)? • GT is a theory of management based on the principle that similar things should be done similarly • GT is the realization that many problems are similar, and that by grouping similar problems, a single solution can be found to a set of problems thus saving time and effort • GT is a manufacturing philosophy in which similar parts are identified and grouped together to take advantage of their similarities in design and production

7. Implementing GT Where to implement GT? • „Plants using traditional batch production and „process type layout • „ If the parts can be grouped into part families „How to implement GT? • „Identify part families • „Rearrange production machines into machine cells

8. Types of Layout • In most of today’s factories it is possible to divide all the made components into families and all the machines into groups, in such a way that all the parts in each family can be completely processed in one group only. • The three main types of layout are: • Line (product) Layout • Functional Layout • Group Layout

9. Line (product) Layout • It involves the arrangements of machines in one line, depending on the sequence of operations. In product layout, if there is a more than one line of production, there are as many lines of machines. • Line Layout is used at present in simple process industries, in continuous assembly, and for mass production of components required in very large quantities.

10. Functional Layout • In Functional Layout, all machines of the same type are laid out together in the same section under the same foreman. Each foreman and his team of workers specialize in one process and work independently. This type of layout is based on process specialization.

11. Group Layout • In Group Layout, each foreman and his team specialize in the production of one list of parts and co-operate in the completion of common task. This type of layouts based on component specialization.

12. The Difference between group and functional layout:

13. Evaluation criteria of Cell Design Evaluations of cell system design are incomplete unless they relate to the Cell Design. A few typical performance variables related to system operation are: • Equipment utilization (high) • Work-in-process inventory (low) • Queue lengths at each workstation (short) • Job throughput time (short) • Job lateness (low)

14. Cell Formation Approach Machine - Component Group Analysis: Machine - Component Group Analysis is based on production flow analysis

15. Machine - Component Group Analysis Production flow analysis involves four stages: Stage 1:Machine classification. Machines are classified on the basis of operations that can be performed on them. A machine type number is assigned to machines capable of performing similar operations.

16. Machine - Component Group Analysis Production flow analysis involves four stages: Stage 2: Checking parts list and production route information. For each part, information on the operations to be undertaken and the machines required to perform each of these operations is checked thoroughly.

17. Machine - Component Group Analysis Production flow analysis involves four stages: Stage 3:Factory flow analysis. This involves a micro-level examination of flow of components through machines. This, in turn, allows the problem to be decomposed into a number of machine-component groups.

18. Machine - Component Group Analysis Production flow analysis involves four stages: Stage 4: Machine-component group analysis. An intuitive manual method is suggested to manipulate the matrix to form cells. However, as the problem size becomes large, the manual approach does not work. Therefore, there is a need to develop analytical approaches to handle large problems systematically.

19. Machine - Component Group Analysis Example: Consider a problem of 4 machines and 6 parts. Try to group them. Components

20. Machine - Component Group Analysis Solution Components

21. T T T CG CG T T T M M M T T T T SG SG M D D D M M D D D SG CG CG D M M SG D D D Cellular Layout Process (Functional) Layout Group (Cellular) Layout A cluster or cell Similar resources placed together Resources to produce similar products placed together

22. Group Technology (CELL) Layouts • One of the most popular hybrid layouts uses Group Technology (GT) and a cellular layout • GT has the advantage of bringing theefficiencies of a product layout to a process layout environment

23. Process Flows before the Use of GT Cells

24. Process Flows after the Use of GT Cells

25. Designing Product Layouts • Designing product layouts requires consideration of: • Sequence of tasks to be performed by each workstation • Logical order • Speed considerations – line balancing

26. Designing Product Layouts – con’t Step 1: Identify tasks & immediate predecessors Step 2: Determine TAKT TIME Step 3: Determine cycle time Step 4: Compute the Theoretical Minimum number of Stations Step 5: Assign tasks to workstations (balance the line) Step 6: Compute efficiency, idle time & balance delay

27. Step 1: Identify Tasks & Immediate Predecessors

28. Layout Calculations • Step 2:Determine TAKT TIME • Vicki needs to produce 60 pizzas per hour • TAKT TIME= 60 sec/unit • Step 3:Determine cycle time • The amount of time each workstation is allowed to complete its tasks • Limited by the bottleneck task (the longest task in a process):

29. Layout Calculations • Step 4:Compute the theoretical minimum number of stations • TM = number of stations needed to achieve 100% efficiency (every second is used) • Always round up (no partial workstations) • Serves as a lower bound for our analysis

30. Layout Calculations • Step 5:Assign tasks to workstations • Start at the first station & choose the longest eligible task following precedence relationships • Continue adding the longest eligible task that fits without going over the desired cycle time • When no additional tasks can be added within the desired cycle time, begin assigning tasks to the next workstation until finished

31. Last Layout Calculation • Step 6:Compute efficiency and balance delay • Efficiency (%) is the ratio of total productive time divided by total time • Balance delay (%) is the amount by which the line falls short of 100%

32. Other Product Layout Considerations • Shape of the line (S, U, O, L): • Share resources, enhance communication & visibility, impact location of loading & unloading • Paced versus Un-paced lines • Paced lines use an automatically enforced cycle time • Number of Product Models produced • Single • Mixed-model lines

33. LINE BALANCING

34. The Line Balancing Problem • The problem is to arrange the individual processing and assembly tasks at the workstations so that the total time required at each workstation is approximately the same. • Nearly impossible to reach perfect balance

35. Things to consider • Sequence of tasks is restricted, there is a required order • Called precedence constraints • There is a production rate needed, i.e. how many products needed per time period • Design the line to meet demand and within constraints

36. Terminology and Definitions • Minimum Work Element • Total Work Content • Workstation Process time • Cycle Time • Precedence Constraints • Balance Delay

37. Minimum Work Element • Dividing the job into tasks of a rational and smallest size • Example: Drill a hole, can’t be divided • Symbol – Time for element j: • is a constant

38. Total Work Content • Aggregate of work elements

39. Workstation Process time • The amount of time for an individual workstation, after individual tasks have been combined into stations • Sum of task times = sum of workstation times

40. Cycle time • Time between parts coming off the line • Ideally, the production rate, but may need to be adjusted for efficiency and down time • Established by the bottleneck station, that is station with largest time

41. Precedence Constraints • Generally given, determined by the required order of operations • Draw in a network style for understanding • Cannot violate these, an element must be complete before the next one is started

42. Balance Delay • Measure of line inefficiency due to imbalances in station times

43. Line Balancing Example EXAMPLE Green Grass’s plant manager just received marketing’s latest forecasts of fertilizer spreader sales for the next year. She wants its production line to be designed to make 2,400 spreaders per week. The plant will operate 40 hours per week. • What should be the line’s cycle time or throughput rate per hour be? • Throughput rate/hr = 2400 / 40 = 60 spreaders/hr • Cycle Time = 1/Throughput rate= 1/60 = 1 minute = 60 seconds

44. Line balancing Example Assume that in order to produce the new fertilizer spreader on the assembly line requires doing the following steps in the order specified: • What is the total number of stations or machines required? TM (total machines) = total production time / cycle time = 244/60 = 4.067 or 5

45. A 40 30 50 40 6 25 15 20 18 B C D E F H G I Draw a Precedence Diagram SOLUTION The figure shows the complete diagram. We begin with work element A, which has no immediate predecessors. Next, we add elements B and C, for which element A is the only immediate predecessor. After entering time standards and arrows showing precedence, we add elements D and E, and so on. The diagram simplifies interpretation. Work element F, for example, can be done anywhere on the line after element C is completed. However, element I must await completion of elements F and G. Precedence Diagram for Assembling the Big Broadcaster

46. Allocating work or activities to stations or machines • The goal is to cluster the work elements into workstations so that • The number of workstations required is minimized • The precedence and cycle-time requirements are not violated • The work content for each station is equal (or nearly so, but less than) the cycle time for the line

47. A 40 30 50 40 6 25 15 20 18 B C D E F H G I Finding a Solution • The minimum number of workstations is 5 and the cycle time is 60 seconds, so Figure 5 represents an optimal solution to the problem Firtilizer Precedence Diagram Solution

48. Efficiency = (100) = t nc 244 5(60) = 81.3% Calculating Line Efficiency c. Now calculate the efficiency measures of a five-station solution: Balance delay (%) = 100 – Efficiency = 100% - 81.3% = 18.7% Idle time = nc – t = 5(60) – 244 = 56 seconds

49. 1 r c = A Line Process • The desired output rate is matched to the staffing or production plan • Line Cycle Time is the maximum time allowed for work at each station is where c = cycle time in hours r = desired output rate

50. t c TM = A Line Process • The theoretical minimum number of stations is where t = total time required to assemble each unit