Process Selection and Facility Layout Process types

Process Selection and Facility Layout

Process types, process selection and automation

Process Selection q The ways organizations choose to produce or provide their goods and services. q It involves choice of technology, type of processing, and so on. q It influences ◦ Capacity planning ◦ Layout of facilities ◦ Equipment ◦ Design of work systems

Process Selection and System Design Forecasting Capacity Planning Product & service Design Technological Change Facilities and Equipment Layout Process Selection Work Design Capacity is significantly impacted by process selection and facility layout.

Factors which influence process selection Batch Variety ◦ How much Flexibility Project Job Shop Repetitive ◦ What degree Volume ◦ Expected output Continuous

Process Types Project: A non-repetitive set of activities directed toward a unique goal within a limited time frame ◦ Unique ◦ Examples: Building a bridge, consulting Job shop: provides unit or lot production or service with changeable specifications, according to customer needs ◦ Small scale ◦ Examples: Machine shop, dentist’s office Batch: Produces many different products in groups (batches) ◦ Low or Moderate volume ◦ Examples: Bakeries, movie theaters, classrooms

Process Types (Cont. ) Repetitive: provides one or a few highly standardized products or services ◦ High volumes of standardized goods or services ◦ Examples: automobiles, computers, cafeteria, car wash Continuous: produces highly uniform products or continuous services, often performed by machines ◦ Very high volumes of non-discrete goods ◦ Examples: refineries, chemical plant, flour, sugar, electricity supplying and the internet

Process Choice Affects Activities /Functions Job Shop Batch Repetitive Continuous Projects Cost estimation Difficult Somewhat routine Routine Simple to complex Cost per unit High Moderate Low Very high Equipment used General purpose Special purpose Varied Fixed costs Low Moderate High Very high Variable costs High Moderate Low Very low High Labor skills High Moderate Low to high Marketing Promote capacities; Semistandard goods/ services Promote standardized goods/ services Promote capacities Scheduling Complex Moderately complex Routine Complex, subject to change Work-inprocess inventory High Low Varied

Automation Automation: Machinery that has sensing and control devices that enables it to operate automatically Standardized goods and services Examples: ◦ Goods: Automobile factories, semiconductors ◦ Services: Package sorting, e-mail, on-line banking

Automation Types Fixed automation ◦ Specialized equipment for a fixed sequence of operations Programmable automation ◦ Computer-aided design and manufacturing systems (CAD/CAM) ◦ Numerically controlled (NC) machines: Machines that perform operations by following mathematical processing instructions. ◦ Robot: A machine consisting of a mechanical arm, a power supply and a controller Flexible automation ◦ Manufacturing cell ◦ Flexible manufacturing systems ◦ Computer-integrated manufacturing (CIM)

Flexible Manufacturing Systems FMS are more fully automated versions of cellular manufacturing: A computer controls the transfer of parts from machine to machine as well as the start of work at each machine Produce a variety of similar products

Classification of production systems and types of layouts

Facilities Layout The arrangement of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system.

The Need for Layout Decisions Inefficient operations For Example: High Cost Bottlenecks Changes in the design of products or services Accidents The introduction of new products or services Safety hazards

The Need for Layout Design (Cont. ) Changes in environmental or other legal requirements Changes in volume of output or mix of products Morale problems Changes in methods or equipment

Basic Layout Types Product Layouts most helpful to repetitive processing Process Layouts used for irregular processing Fixed-position layouts used when projects require layouts Hybrid layouts combinations of these above types • Cellular manufacturing • Group technology • Flexible Manufacturing Systems

Product Layouts Product layout: Layout that uses standardized processing operations to achieve smooth, fast, high-volume flow Made possible by highly standardized goods or services that allow highly standardized, repetitive processing The work is divided into a series of standardized tasks, permitting specialization of equipment and division of labor The large volumes handled by these systems usually make it economical to invest substantial sums of money in equipment and in job design.

Production/Assembly Line Raw materials or customer Materials and/or labor Station 1 Materials and/or labor Station 2 Materials and/or labor Station 3 Station 4 Finished item Materials and/or labor Used for Repetitive or Continuous Processing Example: automobile assembly lines, cafeteria serving line

U-Shaped Production Line In 1 2 3 4 5 Workers 6 Out 10 9 8 7

Advantages of Product Layouts High rate of output Low unit cost Labor specialization Low material handling cost High utilization of labor and equipment Established routing and scheduling Routine accounting, purchasing and inventory control

Disadvantages of Product Layouts Creates boring, repetitive jobs Poorly skilled workers may not maintain equipment or quality of output Fairly inflexible to changes in volume Highly inclined to shutdowns Needs preventive maintenance Individual incentive plans are impractical

Process Layouts Process layouts: Layouts that can handle various processing requirements The layouts feature departments or other functional groupings in which similar kinds of activities are performed Examples: Machine shops usually have separate departments for milling, grinding, drilling, and so on Different products may present quite different processing requirements and sequences of operations

Process Layout Milling Assembly & Test Drilling Grinding Plating Process Layout - work travels to dedicated process centers

Comparison of Process and Product Layout

Advantages of Process Layouts Can handle a variety of processing requirements Not particularly at risk 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, inventory control and purchasing are more involved

Fixed-Position Layouts Fixed-Position Layout: Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed Examples: ◦ Large construction projects (buildings, power plants, dams) ◦ Shipbuilding, production of large aircraft ◦ Rockets used to launch space missions

Combination Layouts The three basic layout types may be altered to satisfy the needs of a particular situation Examples: ◦ Supermarket layouts: primarily process layout, have fixed-path material-handling devices as well (rollertype conveyors and belt-type conveyors) ◦ Hospitals: process layout, fixed-position layout as well (patient care) ◦ Off-line reworking (customized processing) of faulty parts in a product layout

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 üDesign characteristics: size, shape and function. üManufacturing or processing characteristics: type and sequence of operations required.

Line Balancing

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. Tasks are grouped into manageable bundles and assigned to workstations with one or two operators Goal is to minimize idle time along the line, which leads to high utilization of labor and equipment Perfect balance is often impossible to achieve

Cycle Time Cycle time is the maximum time allowed at each workstation to complete its set of tasks on a unit.

Example 1: Cycle Times 0. 1 min. 0. 7 min. 1. 0 min. With 5 workstations, CT = 0. 5 min. 1. 0 minute. Cycle time of a system = longest processing time in a workstation. 0. 2 min.

Example 1: Cycle Times 0. 1 min. 0. 7 min. 1. 0 min. 0. 5 min. 0. 2 min. With 1 workstation, CT = 2. 5 minutes. Cycle time of workstation = total processing time in of tasks. With 3 workstations, can CT = 1. 0 minute? 0. 1 min. 0. 7 min. Workstation 1 1. 0 min. Workstation 2 0. 5 min. 0. 2 min. Workstation 3

Output Capacity OT Output capacity = CT OT = operating time per day CT = cycle time Example: 8 hours per day OT = 8 x 60 = 480 minutes per day Cycle Time = CT = 1. 0 min Output = OT/CT = 480/1. 0 = 480 units per day Cycle Time = CT = 2. 5 min Output = OT/CT = 480/2. 5 = 192 units per day

Cycle Time Determined by Desired Output OT CT = cycle time = D D = Desired output rate Example: 8 hours per day OT = 8 x 60 = 480 minutes per day D = 480 units per day CT = OT/D = 480/480 = 1. 0 Minute

Theoretical Minimum Number of Stations Required Nmin = åt CT å t = sum of task times Nmin = theoretical Minimum Number of Workstations Required Example: 8 hours per day, desired output rate is 480 units per day CT = OT/D = 480/480 = 1. 0 Minute Nmin = ∑t /CT = 2. 5/1. 0 = 2. 5 stations ≈ 3 stations

Designing Process Layouts

Designing Process Layout The main issue in design of process layouts concerns the relative positioning of the departments involved. Departments must be assigned to locations. The problem is to develop a reasonably good layout; some combinations will be more desirable than others.

Considerations Some departments may benefit from adjacent locations • Sharing expensive tools or equipments. Some departments should be separated • A lab with delicate equipment should not be located near a department that has equipment with strong vibrations. • Sand blasting department and painting department. • Flammable materials near a furnace.

Measures of Effectiveness One advantage of process layouts: satisfy a variety of processing requirements Customers or materials in these systems require different operations and different sequences of operations One of the major objectives in process layout is to minimize transportation cost, distance, or time This is usually accomplished by locating departments with relatively high interdepartmental work flow as close together as possible