- Количество слайдов: 49
Process Selection and Facility Layout
Introduction • Process selection – Deciding on the way production of goods or services will be organized • Major implications – Capacity planning – Layout of facilities – Equipment – Design of work systems
Process Selection and System Design Outputs Inputs Forecasting Capacity Planning Product and Service Design Technological Change Facilities and Equipment Layout Process Selection Work Design
Process Strategy Key aspects of process strategy – Capital intensive – equipment/labor – Process flexibility – Adjust to changes – Design – Volume – Technology
Process Selection • Variety – How much Batch • Flexibility – What degree • Volume – Expected output Job Shop Repetitive Continuous
Process types and volume • Job shop – Small scale, wide variety of goods • Batch – Moderate volume, flexible • Repetitive or assembly line – High volumes of standardized goods or services • Continuous – Very high volumes of non-discrete goods • Projects – Nonroutine work, uniqe set ob objectives, limited timeframe and resources
Product – Process Matrix The diagonal of the matrix represents the ideal choice of processing system for a given sets of circumstances.
Functions/activities affected by process choice Job variety, process flexibility, unit cost Volume Limited (not ongoing)
Product and service life cycles • Alongside the life cycle the sales and with it the producion volume can change. • So managers must be aware of the change in the optimal processing system. (the necessity of change is highly dependent on the particular good or service)
Product/Service Profilig • Linking key product or service requirements to process capavilities. • Design the process with taking into consideration the following: – Range of products/services – Expected order size – Pricing – Expected frequency of changes in schedules etc. – Order-winning requirements –…
Sustainable production Non-polluting Conserving natural resources & energy Economically efficient Safe and healthful for workers, communities and consumers • Socially and creaqtively rewarding for workers • •
Automation of production and services • Automation: Machinery that has sensing and control devices that enables it to operate – Fixed automation – Programmable automation
Advantages of automation • Low variability in performance and quality • Machines do not – get bored or distracted – go out on strike or ask for higher wages – lower variable costs
Disadvantages • • • Higher initial (investment) cost and Higher fixed costs Lower felxibility Higher skills needed Lower morale of human workforce Need for standardisation – Products – Processes – Equipment and materials etc.
Automation • Computer-aided design and manufacturing systems (CAD/CAM) • Numerically controlled (NC) machines • Computerized numerical control (CNC) • Direct numerical control (DNC) • Robot: mechanical arm + power supply + controller • Manufacturing cell • Flexible manufacturing systems (FMS) • Computer-integrated manufacturing (CIM)
Facilities Layout • Layout: the configuration of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system
Importance of Layout Decisions • Requires substantial investments of money and effort • Involves long-term commitments • Has significant impact on cost and efficiency of short-term operations
The Need for Layout Decisions • Inefficient operations • High (variable) Cost • Bottlenecks • Changes in the design of products or services • The introduction of new products or services • Safety • Changes in environmental or other legal requirements • Changes in volume of output or mix of products • Changes in methods and equipment • Morale problems
Objectives of facility layout Main: smooth flow of work, material and information Supporting objectives:
Basic Layout Types • Product layouts • Process layouts • Fixed-Position layout Hybrid types: • Combination layouts
Basic Layout Types • Product layout – Layout that uses standardized processing operations to achieve smooth, rapid, high-volume flow • Process layout – Layout that can handle varied processing requirements • Fixed Position layout – Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed
Product Layout Used for Repetitive or Continuous Processing
Advantages of Product Layout • • High rate of output Low unit cost Labor specialization Low material handling cost High utilization of labor and equipment Established routing and scheduling Routing accounting and purchasing
Disadvantages of Product Layout • Creates dull, repetitive jobs • Poorly skilled workers may not maintain equipment or quality of output • Fairly inflexible to changes in volume • Highly susceptible to shutdowns • Needs preventive maintenance • Individual incentive plans are impractical
A U-Shaped Production Line
Advantages/disadvantages of U-shaped lines • Shorter distances for workers & machines • Permits communication thus facilitates teamwork • More flexible work assignments • Optimal is the facility has the same entry and exit point • If lines are highly automated, there is no need for communication and travel • If entry points are on the opposite side as exit points • Noise and contamination factors are increased in the U-shape
Process Layout (functional) Dept. A Dept. C Dept. E Dept. B Dept. D Dept. F Used for Intermittent processing Job Shop or Batch
Product Layout (sequential) Work Station 1 Work Station 2 Work Station 3 Used for Repetitive Processing Repetitive or Continuous
Advantages of Process Layouts • Can handle a variety of processing requirements • Not particularly vulnerable to equipment failures • Equipment used is less costly • Possible to use individual incentive plans
Disadvantages of Process Layouts In-process inventory costs can be high Challenging routing and scheduling Equipment utilization rates are low Material handling slow and inefficient Complexities often reduce span of supervision Special attention for each product or customer • Accounting and purchasing are more involved • • •
Fixed-position layouts • The product or project remains stationary and workers, materials, and equipment are moved as needed. • If weight, size, bulk, or some other factor makes it undesirable or extremely difficult to move the product. • E. g. firefighting, road-building, home-building, drilling for oil etc.
Cellular Layouts • Cellular Production – Layout in which machines are grouped into a cell that can process items that have similar processing requirements • Group Technology – – The grouping into part families of items with similar design or manufacturing characteristics Makes cellular production much more effective
Cellular layout Traditional process layout
Functional vs. Cellular Layouts Dimension Functional Cellular Number of moves between departments many few Travel distances longer shorter Travel paths variable fixed Job waiting times greater shorter Throughput time higher lower Amount of work in process higher lower Supervision difficulty higher lower Scheduling complexity higher lower Equipment utilization lower higher
Other Solutions & Service Layouts • Use of flexible manufacturing systems Service layouts • Warehouse and storage layouts – Minimizing movement & picking time and cost • Retail layouts – Presence & influence of customers • Office layouts: – Information is computerized, image of openness
Design Product Layouts: Line Balancing is the process of assigning tasks to workstations in such a way that the workstations have approximately equal time requirements. This way the idle time will be minimized, utilization will be maximized Specialzation: dividing work into elematal tasks that can be performed quickly and routinely
Cycle Time Cycle time is the maximum time allowed at each workstation to complete its set of tasks on a unit. tmax < Cycle time < ∑t
Determine the Minimum Number of Workstations Required
Precedence Diagram A diagram that shows elemental tasks and their precedence requirements. 0. 1 min. 1. 0 min. a b c 0. 7 min. A Simple Precedence Diagram d 0. 5 min. e 0. 2 min.
Example 1: Assembly Line Balancing Assume that the desired output is 480 units per day. The facility is workint 8 hours a day. The elemental tasks and their connections are shown in the previous slide. • Calculate the cycle time. • Calculate the minimum number of workstations. • Arrange the tasks into these workstations in the order of the greatest number of following tasks.
Example 1 Solution Time Workstation Remaining Revised Time Remaining Eligible Assign Task 1. 0 0. 9 0. 2 a, c ** none*** a c - 0. 9 0. 2 2 1. 0 b b 0. 0 3 1. 0 0. 5 0. 3 d e - 0. 5 0. 3 1 Station Idle Time 0. 2 * Tasks that have no predecessors. ** b is not eligible, because it needs more time than the remaining. *** Every available task needs more time than 0. 2. 0. 0 0. 3 Total: 0. 5
Calculate Percent Idle Time and efficiency Efficiency = 1 – Percent idle time
Line balancing procedure
Line Balancing Heuristics • Assign tasks in order of most following tasks. – Count the number of tasks that follow • Assign tasks in order of task time. • Assign tasks in order of greatest positional weight. – Positional weight is the sum of each task’s time and the times of all following tasks.
Example 2 Working day is 8 hours and the desired output rate is 400 units per day. Draw the precedence diagram. Compute the cycle time & the minimum number of workstations required. Assign tasks to workstations according to the greatest number of following tasks. Tiebreaker: longest processing time goes first. Calculate Percent idle time & efficiency.
Other approaches • Paralell workstations • Cross-train workers (dynamic line balancing) • Mixed model line (more product on the same line)
Parallel Workstations 1 min. 30/hr. 2 min. 30/hr. 1 min. 30/hr. Bottleneck 30/hr. 1 min. 60/hr. 1 min. 30/hr. 1 min. 30/hr. 1 min. Parallel Workstations 30/hr. 60/hr.
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