Assembly Lines. Input: Raw Materials Output: Finished Product Set of Sequential Workstations Connected by A Continuous Materials Handling System

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1 Lines

2 Lines Input: Raw Materials Output: Finished Product Set of Sequential Workstations Connected by A Continuous Materials Handling System

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4 Lines in Produduction Systems With respect to Production Flow Continuous Production Flow Discrete Production Flow Transfer Line Line

5 Operations Feeding Handling Insertion Control

6 Some Definitions Minimum rational work element: An assembly task that can not be subdivided any further without loss of practicality. Precedence diagram: A network where each node represents a work element, and arrows indicate a precedence relationship. Example

7 Some Definitions (Cont d.) Cycle time: The maximum time available to complete one assembled unit at any assembly station. The cycle time (CT) (time/pc) is computed based on the demand rate (D,pc/time), and available time (AT, time). CT=AT/D

8 Line Types Single Model Lines Multi Model Line Mixed Model Line

9 Work Transfer in Lines Non-Mechanic Lines: worker performs handling activities. Mechanic Lines: A material handling system exists. Two situations Units can be taken from conveyor Units can not be taken from conveyor Continuous Lİne Paced Line

10 Different Types of Workstations in Continuous Lines

11 Layouts for Lines Straight Line

12 U-Type Line

13 Parallel Line

14 Line Balancing

15 Line Balancing Constraints Fundamental Constraints Cycle time constraint Precedence constraint Additional Constraints Technological Constraint Layout constraint Constraints about operator skills

16 Team Oriented Lines Manufacturing cells teams Multi-manned workstations, where workers groups simultaneously perform different assembly works on the same product and workstation Attempts to minimize disadvantages of conventional assembly lines.

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18 Mixed model team oriented assembly lines shorter lead time product quality less material handling less space requirement

19 Proposed Methodology 5 Basic Steps of the Methodology HORIZONTAL BALANCING VERTICAL BALANCING CREATING PHYSICAL STATIONS (FORMING TEAMS) SIMULATION BASED WORKER TRANSFER SYSTEM MODEL SEQUENCING

20 Bedworth, D.D., & Bailey, J. (1987). Integrated Production Control Systems, Analysis, Design. John Wiley & Sons, Horizontal balancing An efficiency improvement process that assign the tasks to operators such that each task family takes the time as close as the required cycle time (or takt time) Worker minimization Regional Approach by Bedworth and Bailey (1987)

21 Vertical Balancing Vertical balancing-merengo et al. (1999) Workload smoothing among workers Provides task transfers from workers who have more workload than the average, to the workers who have less. Merengo, C., Nava, F. & Pozzetti, A. (1999). Balancing, & sequencing manual mixed-model assembly lines. International Journal of Production

22 Creating Physical Stations (Forming Teams) Worker grouping via performing parallel tasks Multi-manned stations Team forming approach; project scheduling under limited resources (Elsayed and Boucher 1985). A modified version of the algorithm is employed for a different field Elsayed, E.A., &Boucher, T.O. (1985). Analysis and control of production systems. Prentice Hall,

23 Industrial Application Mixed model tractor assembly line. Consists of ten segments The hydraulic cover-hydraulic test segment

24 Kiln-Drying Radiator Cooling The Beginning of II. Line Front Linkage Tractor Taking Down Unit Spool Valve The Beginning of Conveyor Indicator Subassembly Indicator Load Platform Load Platform Subassembly Fuel Tank Subassembly Fuel Tank Mudguard Depot Supply Hood Hood Subassembly Bracket The End of Conveyor Wheel Tractor Taking Down Unit The End of II. Line The Beginning of I. Line Washing Step Hydraulic Pipe Battery Plate Bumper Support Motor Brake Pedal Rear Axle Housing The End of I. Line Step Subassembly Battery Plate Subassembly Bumper Support Subassembly ASSEMBLY LINE SEGMENTS 1: Rear Axle Housing, Central Housing, Rear Axle Housing, Cronkwheel 2: Hydraulic Cover, Hydraulic Test 3: Transmission, Transmission Subassembly 4: Brake Pedal, Brake Pedal Subassembly, Motor, Motor Subassembly, Bumper Support, Bumper Support Subassembly 5: Battery Plate, Battery Plate Subassembly, Hydraulic Pipe, Step, Step Subassembly 6: Washing, Priming, Painting, Kiln-Drying, Cooling, Radiator, Spool Valve 7: Indicator, Indicator Subassembly, Indicator, Indicator Subassembly, Load Platform, Load Platform Subassembly, Fuel Tank, Fuel Tank Subassembly 8: Mudguard 9: Depot Supply, Hood, Hood Subassembly, Bracket 10: Wheel Motor Subassembly Brake Pedal Subassembly Transmission Subassembly Transmission Hydraulic Test Hydraulic Cover Central Housing Cronkwheel Rear Axle Housing TRACTOR ASSEMBLY LINE I. Line Lenght : m II. Line Lenght : 62.5 m Active Line Lenght : m II. Line Conveyor Lenght : 56 m Overall Line Lenght : m Tractor assembly line layout

25 Tractor model classes Model code Sequence number Required cycle time (seconds) T T T T T T Horizontal and vertical balancing results

26 In the step of physical station creating; Maximum allowable team size: 7 Cycle time exceeding tolerance: %15 Number of workers within teams Number of operators Physical station Σ

27 Comparison.. PM PCALBP Number of workers Number of physical stations 6 12 Sizes of physical stations Each one is 1 Space utilization factor Avarage lead time (minutes) Non-value added time rate (%) Average physical station utilization rate (%) Abbreviations: PM: Proposed methodology PCALBP: Previously applied conventional assembly line balancing procedure

28 Model Sequencing Aim to minimize probability of blocking and starvation events (for unpaced lines) to keep constant parts usage Models with longer station times should not enter the line consequently

29 Demand value based mixed model sequencing simple approach needing only the demand data of models (Merengo et al. 1999). DD ( j, p ) p j : amount of j-type model to be assembled D : total daily demand D j : daily demand of model j DD(j, p j ) : priority of model j depending on p j j = p sequence is generated by sorting these values in ascending order j 1 2 D D j Merengo, C., Nava, F. & Pozzetti, A. (1999). Balancing, & sequencing manual mixed-

30 Example Model Types: 1, 2, 3. Daily demads of the model types are 5, 3 and 2, respectively. ( j ) DD, values are: p j j DD ( j,1) DD ( j,2) DD ( j,3) DD ( j,4) DD ( j,5) Ascending order of DD (j, p j ) valus results in the sequence of