Process Selection and Facility Layout

Process types, process selection and automation

Process Selection The ways organizations choose to produce or provide their goods and services. It involves choice of technology, type of processing, and so on. It influences Process selection refers to …. It has major implication For capacity planning, …. The decision of process selection is made when new products or services are being planned. Process selection also occurs due to technological changes, as well as competitive pressure. Capacity planning Layout of facilities Equipment Design of work systems

Process Selection and System Design Forecasting Facilities and Equipment Capacity Planning Picture of system design. (pointer) Capacity planning and process selection are based on …., Based on capacity planning and process selection, manager can choose what kind of facilities to build, what equipments to buy, how to design layout, and how to do work design. Layout Product & service Design Process Selection Work Design Technological Change Capacity is significantly impacted by process selection and facility layout.

Factors which influence process selection Variety How much Flexibility What degree Volume Expected output Batch Repetitive Continuous Job Shop Project To select an appropriate process, three primary questions should be answered. How much variety in products or services will the system need to handle? What degree of equipment flexibility will be needed? What is the expected volume of output?

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 A job shop operates on a small scale. It is needed when a low volume of high-variety goods or services will be needed. Processing is intermittent. Batch: moderate Repetitive processing is used to produce high volumes of standardized goods or services.

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 Variable costs Very low Labor skills Low to high Marketing Promote capacities Promote capacities; Semi-standard goods/ services Promote standardized goods/ services Scheduling Complex Moderately complex Complex, subject to change Work-in-process inventory

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 A key question in process design is whether to automation. Automation requires standardized goods and services.

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) Fixed automation uses specialized equipment for a fixed sequence of operations. Low cost and high volume are its primary advantages; minimal variety and the high cost of making major changes are its primary limitations. Programmable automation is at the opposite end. It involves the use of high-cost, general-purpose equipment controlled by computers. This type of automation can produce a wide variety of low-volume products in small batches. Flexible automation evolved from programmable automation. A key difference between the two is that flexible automation requires significantly less changeover time.

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 The introduction of new products or services Accidents Safety hazards Most common reasons for layout design include

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

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 Finished item Station 2 3 4 Materials and/or labor Used for Repetitive or Continuous Processing Example: automobile assembly lines, cafeteria serving line 1 In manufacturing environments

U-Shaped Production Line 1 2 3 4 5 6 7 8 9 10 In Out Workers Advantages: … is more compact; its length is half the length of a straight line. Communication among workers is increased because workers are clustered. Compared to a straight line, flexibility in work assignments is increased because workers can handle more stations. Materials entering point is the same as finished product leaving point, minimize material handling

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 1. There is a high rate of output. 2. Units costs are low due to high volume; the high cost of specialized equipment is spread over many units. 3. Labor specialization reduces training costs and time and results in a wide span of supervision. 4. Material-handling costs are low per unit, and material handling is simplified because units follow the same sequence of operations. 5. There is a high utilization of labor and equipment. 6. Routing and scheduling are encompassed in the initial design of the system and do not require much attention once the system is in operation. 7. Accounting, purchasing, and inventory control are fairly routine.

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 1. The intensive division of labor usually creates dull, repetitive jobs, which do not provide much opportunity for advancement and may lead to morale problems. 2. Poorly skilled workers may exhibit little interest in maintaining equipment or in quality of output. 3. The system is fairly inflexible in response to either changes in the volume of output or changes in product or process design. 4. The system is highly susceptible to shutdowns caused by equipment breakdowns or excessive absenteeism. 5. Preventive maintenance, the capacity for quick repairs, and spare parts inventories are necessary expenses. 6. Incentive plans tied to individual output are impractical since they would tend to cause variations among outputs of individual workers that would adversely affect high utilization of labor and equipment.

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

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 Systems can handle a variety of processing requirements. The system is not particularly vulnerable to equipment failure. 3. General-purpose equipment is often less costly than the specialized equipment used in product layouts and is easier and less costly to maintain. 4. It is possible to use individual incentive systems.

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 1. In-process inventory costs can be high if batch processing is used in manufacturing systems. 2. Routing and scheduling pose continual challenges. 3. Equipment utilization rates are low. 4. Material handling is slow and inefficient and more costly per unit than under product layouts. 5. Job complexities often reduce the span of supervision and result in higher supervisory costs than product layouts do. 6. Special attention for each product or customer (routing, scheduling, machine setups, and so on) and low volumes result in higher unit costs than with product layouts. 7. Accounting, inventory control, and purchasing are much more involved than under product layouts.

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 In fixed-position layouts, the item being worked on remains stationary, and workers, materials, and equipment are moved about as needed. This is in marked contrast to product and process layouts. Almost always, the nature of the product dictates this kind of arrangement: weight, size, bulk, or some other factor makes it undesirable or extremely difficult to attempt to move the product.

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 (roller- type 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 Design characteristics: size, shape and function. Manufacturing or processing characteristics: type and sequence of operations required. Some manufacturing are attempting to move away from process layouts in an effort to capture some benefits of product layouts. Ideally, a system would be flexible and be efficient with low unit production cost. Cellular manufacturing, group technology, and flexible manufacturing systems represent efforts to move toward this idea. 1. There are numerous benefits of cellular manufacturing. These relate to the grouping of equipment. They include faster throughput time, less material handling, less work-in-process inventory, and reduced setup time. 2. For cellular manufacturing to be effective, there must be groups of items that have similar processing characteristics. Moreover, these items must be identified. The grouping process is known as group technology and involves identifying items that have similarities in either design characteristics or manufacturing characteristics and grouping them into part families.

Line Balancing

Design Product Layouts: Line Balancing 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. The primary determinant is what the line’s cycle time will be. Cycle time also establishes the output rate of a line. For instance, if the cycle time is two minutes, units will come off the end of the line at the rate of one every two minutes.

Example 1: Cycle Times With 5 workstations, CT = 1.0 minute. Cycle time of a system = longest processing time in a workstation.

Example 1: Cycle Times 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? 0.5 min. 1.0 min. 0.7 min. 0.1 min. 0.2 min. Workstation 1 Workstation 2 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 D CT = cycle time = 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 = 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