Upload
hilary-dean
View
261
Download
3
Embed Size (px)
Citation preview
◦ Capacity planning
◦ Layout of facilities
◦ Equipment
◦ Design of work systems
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
ProcessSelection
CapacityPlanning
Forecasting
WorkDesign
Product & service Design
Technological
Change
Layout
Facilities and
Equipment
Capacity is significantly impacted by process selection and facility layout.
Variety◦ How much
Flexibility◦ What degree
Volume◦ Expected output
Batch
Repetitive
Continuous
Job Shop
Project
Project: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: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:Batch: Produces many different products in groups (batches)◦ Low or Moderate volume◦ Examples: Bakeries, movie theaters, classrooms
Repetitive: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: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
Job Shop Batch Repetitive Continuous Projects
Cost estimation
Difficult Somewhat routine Routine Routine Simple to complex
Cost per unit High Moderate Low Low Very high
Equipment used
General purpose
General purpose Special purpose
Special purpose
Varied
Fixed costs Low Moderate High Very high Very high
Variable costs
High Moderate Low Very low High
Labor skills High Moderate Low Low to high Low to high
Marketing Promote capacities
Promote capacities; Semi-standard goods/ services
Promote standardized goods/ services
Promote standardized goods/ services
Promote capacities
Scheduling Complex Moderately complex
Routine Routine Complex, subject to change
Work-in-process inventory
High High Low 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
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)
FMSFMS 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 Classification of production systems and types of layoutssystems and types of layouts
The arrangement of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system.
Inefficient operations
For Example:High CostBottlenecks
Changes in the designof products or services
The introduction of newproducts or services
Accidents
Safety hazards
Changes inenvironmentalor other legalrequirements
Changes in volume ofoutput or mix of
products
Changes in methodsor equipment
Morale problems
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 layout: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.
Raw materialsor customer
Finished item
Station 2
Station 2
Station 3
Station 3
Station 4
Station 4
Materials and/or labor
Materials and/or labor
Materials and/or labor
Materials and/or labor
Used for Repetitive or Continuous Processing
Example: automobile assembly lines, cafeteria serving line
Station 1
Station 1
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
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 - work travels to dedicated process centers
Milling
Assembly& Test Grinding
Drilling Plating
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
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 Layout: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
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 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 characteristicsDesign characteristics: size, shape and function.Manufacturing or processing characteristics: type
and sequence of operations required.
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
Line Balancing is the process of assigning tasks to workstations in such a way that the workstations have approximately equal time requirements.
With 5 workstations, CT =
0.5 min.1.0 min.0.7 min.0.1 min. 0.2 min.
1.0 minute.
Cycle time of a system = longest processing time in a workstation.
With 1 workstation, CT =
0.5 min.1.0 min.0.7 min.0.1 min. 0.2 min.
2.5 minutes.
0.5 min.1.0 min.0.7 min.0.1 min. 0.2 min.
Workstation 1 Workstation 2 Workstation 3
With 3 workstations, can CT = 1.0 minute?
Cycle time of workstation = total processing time in of tasks.
Output capacity = OTCT
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
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
D = Desired output rate
CT = cycle time =OTD
Nmin = CT
t
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
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.
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.
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