CHAPTER 6 PROCESS SELECTION AND FACILITY LAYOUT Teaching Notes Facility Layout involves physical placement of departments and/or arrangement of equipment within a plant or a service facility. A good layout will possibly lead to smooth flow of material, reduction of inventories, and effective utilization of space. spac e. The material in this chapter can be divided into four areas: 1.
1.
Process types, process selection and automation.
2.
2.
Classification of production systems and (corresponding) (corresponding) types of layouts.
3.
3.
Line balancing.
4.
4.
Designing process layouts.
This chapter provides a good lead-in for the following chapter on design of work systems because it introduces some of the problems that can be associated with work systems. It also describes group technology, cellular manufacturing, and flexible manufactur ing systems.
Answers to Discussion and Review Questions 1.
Process selection selectio n refers to the ways organizations organiza tions choose to produce or provide their goods and services. It involves choice of technology, type of processing, and so on. These choices have important implications implications for capacity planning, layout of facilities, equipment choices, and the design of work systems.
2.
There are five basic process types: a. Job-shop: Job-shop is used when a low volume and a large variety of goods or or services are needed. Job-shop involves intermittent processing, high flexibility, skilled workers, r elatively elatively large work-in-process inventories inventories and general-purpose machinery. An example is a tool and a nd die shop that is able to produce a wide variety of tools. b. Batch: Batch processing is is used when a moderate volume of goods and services servic es is demanded. It is designed to handle a moderate variety in products. The processing is intermittent. The flexibility of the process to produce a variety of goods, the skill of the workers, amount of work-in-process work-in-process inventories are all a ll less than job shop. A typical example of batch processing is paint manufacturing. c. Repetitive: This type of a process involves higher volumes of more standardized goods or services. The flexibility of the process to produce a variety of goods, the skill of the workers, amount of work-in-process inventories are all less than batch process. Typical examples for this type of process include appliances and automobiles. d. Continuous: Continuous : This type of a process involves very high volume of of highly standardized standar dized goods or services. These systems have no flexibility in output or equipment. Workers are generally low skilled and there is no work-in-process inventory. The machines are dedicated to perform specified tasks. Typical examples include petroleum p etroleum products, steel and sugar manufacturing. manufacturing. e. Project: Projects Projects are designed to be used with with non-routine, non-routine, unusual tasks or or activities. These These activities are generally not repeated. Equipment flexibility, level of worker skills and workin-process inventory can range from very low to very high. Examples include construction of a dam or a bridge, conversion of the production system from job-shop to group technology, installing and implementing a new inventory and bar coding system.
3.
Advantages: Highly uniform output, boredom and fatigue are not factors, machines machines don¶t go out on strike, etc.
4.
Numerically controlled (N/C) machines are programmed to follow a set of processing instructions instructions based on mathematical relationships. Robots have movable arms that enable them to handle a wide variety of tasks such as welding, welding, assembly a ssembly,, loading and unloading machines, painting pa inting,, and testing. Flexible manufacturing systems systems (FMS) are groups of machines that have a supervisory supervisory computer, automatic material handling, and automatic processing. Systems usually range from 3 machines to a dozen. They are designed to handle a variety of processing requirements (similar to intermittent systems) with some of the benefits of automation. Computer-integrated Computer-integrated manufacturing (CIM) is a system for linking manufacturing activities through an integrated computer. These T hese include engineering design, flexible manufacturing systems, and production planning and control.
5.
(See question #4 above for description.)
6.
Process selection decisions often include aspects that require highly technical knowledge. knowledge. Many managers do not possess such expertise. However, if those dec isions are delegated to engineers or others who do have the expertise, there is the danger that managerial issues will suffer. The solution is for managers to increase their knowledge of technological advances. In the meantime, managers must be prepared to ask questions and impress upon technical experts their goals and objectives.
7.
Managers sometimes view flexible systems as a hedge; hence, they opt for such systems without having complete understanding of future needs, reasoning that their lack of knowledge is offset by the flexible nature of the system. However, such systems are more expensive to install and maintain. Moreover, the flexibility provided by such systems may not be needed, or it may be of the wrong type. In many cases, a dedicated, dedicated, or focused system, would be a better choice.
8.
The trade-offs between product layout and process layout include the following: a. Process layout has more equipment flexibility. flexibil ity. b. Process layout generally has higher higher skilled skilled workers. workers. c. Product layout involves higher volume manufacturing. manufactu ring. d. Process layout layout benefits from high flexibility flexibility to be able to produce a variety variety of products, products, while product layout benefits from large volume manufacturing at low cost. e. The major goal goal of process layout is to minimize the transportation transport ation and material materia l handling costs while the primary objective of the product layout is to minimize idle time and maximize efficiency of the process. f.
The utilization utilizatio n of process layout generally general ly results in higher levels of work-in-process work-in-pr ocess inventory than the product layout.
g. For a product layout, the flow of work is is straight, while for process layout, the flow of work is mixed depending on the product produced. h. There is more dependency between workstations workstati ons for product layout layout than for a process layout.
9.
i.
The preventive preventive maintenance maintenance and machine machine reliability reliability are more important important in a product product layout than process layout because equipment breakdown may involve shutting down a work station which may in turn result in shutting down downstream work stations.
j.
Routing and scheduling schedulin g is much less complicated complica ted for processes with product layout than processes with process layout.
The most common reasons for redesign of layouts include: include: a. Inefficient Inefficient operations.
3.
Advantages: Highly uniform output, boredom and fatigue are not factors, machines machines don¶t go out on strike, etc.
4.
Numerically controlled (N/C) machines are programmed to follow a set of processing instructions instructions based on mathematical relationships. Robots have movable arms that enable them to handle a wide variety of tasks such as welding, welding, assembly a ssembly,, loading and unloading machines, painting pa inting,, and testing. Flexible manufacturing systems systems (FMS) are groups of machines that have a supervisory supervisory computer, automatic material handling, and automatic processing. Systems usually range from 3 machines to a dozen. They are designed to handle a variety of processing requirements (similar to intermittent systems) with some of the benefits of automation. Computer-integrated Computer-integrated manufacturing (CIM) is a system for linking manufacturing activities through an integrated computer. These T hese include engineering design, flexible manufacturing systems, and production planning and control.
5.
(See question #4 above for description.)
6.
Process selection decisions often include aspects that require highly technical knowledge. knowledge. Many managers do not possess such expertise. However, if those dec isions are delegated to engineers or others who do have the expertise, there is the danger that managerial issues will suffer. The solution is for managers to increase their knowledge of technological advances. In the meantime, managers must be prepared to ask questions and impress upon technical experts their goals and objectives.
7.
Managers sometimes view flexible systems as a hedge; hence, they opt for such systems without having complete understanding of future needs, reasoning that their lack of knowledge is offset by the flexible nature of the system. However, such systems are more expensive to install and maintain. Moreover, the flexibility provided by such systems may not be needed, or it may be of the wrong type. In many cases, a dedicated, dedicated, or focused system, would be a better choice.
8.
The trade-offs between product layout and process layout include the following: a. Process layout has more equipment flexibility. flexibil ity. b. Process layout generally has higher higher skilled skilled workers. workers. c. Product layout involves higher volume manufacturing. manufactu ring. d. Process layout layout benefits from high flexibility flexibility to be able to produce a variety variety of products, products, while product layout benefits from large volume manufacturing at low cost. e. The major goal goal of process layout is to minimize the transportation transport ation and material materia l handling costs while the primary objective of the product layout is to minimize idle time and maximize efficiency of the process. f.
The utilization utilizatio n of process layout generally general ly results in higher levels of work-in-process work-in-pr ocess inventory than the product layout.
g. For a product layout, the flow of work is is straight, while for process layout, the flow of work is mixed depending on the product produced. h. There is more dependency between workstations workstati ons for product layout layout than for a process layout.
9.
i.
The preventive preventive maintenance maintenance and machine machine reliability reliability are more important important in a product product layout than process layout because equipment breakdown may involve shutting down a work station which may in turn result in shutting down downstream work stations.
j.
Routing and scheduling schedulin g is much less complicated complica ted for processes with product layout than processes with process layout.
The most common reasons for redesign of layouts include: include: a. Inefficient Inefficient operations.
b. Accidents Accidents or safety hazards. c. Changes in the design of products or services. d. Introduction of of new products or services. e. Changes in the volume of output or mix of outputs. f.
Changes in methods or equipment.
g. Changes in environmental environmental or other other legal legal requirements. h. Morale problems 10.
Product layouts are generally characterized by specialized labor and equipment designed for continuous continuous processing. The layout is often arranged on the basis of processing sequence. Process layouts are more general in nature, in terms of labor, processing equipment and material handling equipment. Process layouts often feature machine groups or departments. Items processed in process layouts tend to follow differing paths through the system. Fixed position layouts are used to facilitate processing of a single (usually large) job, such as construction of a large building or a hydro-electric power plant. Labor, equipment and materials are typically brought to the job site (i.e., to the ³product´) rather than the other way around. ar ound. Fixed position layouts are commonly found in farming, road building, building, home remodeling r emodeling and mining.
11.
The main advantages advanta ges of product layouts include: a. A potentially potentiall y high rate of output. b. Low unit costs. c. Low training tra ining costs and wide span of supervision due to specialization. specia lization. d. Low unit cost for material handling. e. High utilization utilizati on of labor and equipment. f.
Routing and scheduling scheduli ng are built into the design.
g. Accounting, Accounting, purchasing and inventory inventory control control are fairly routine. routine. The main disadvantages of product layouts include: a. Specialization Specializa tion can mean dull, dull, repetitive jobs with with little opportunity opportunit y for personal satisfaction or creativity. b. Workers may have little interest in maintaining equipment or in the quality of output. c. The system is not particularly part icularly adaptable to changes in process design or changes in the volume of output. d. The system is highly susceptible to shutdowns caused by equipment failure or excessive absenteeism. e. Preventive maintenance maintenance costs and the capacity for for quick repairs are necessary necessary to ensure high utilization. f. 12.
Incentive plans tied to individual output are impractical. impract ical.
The main advantages of process layouts are: a. They can handle a variety variety of processing requirements. b. The system is less vulnera vulnerable ble to equipment failures than product layouts. c. The general purpose equipment used is often less costly than the specialized specia lized equipment used in product layouts. It is also usually easier and less costly to maintain and repair. d. Individual Individual incentive incentive systems are possible. possible. The main disadvantages of process layouts are: ar e: a. In-process In-process inventory costs can be high (manufacturing). b. Routing and scheduling schedulin g must must be done for each new job.
c. Equipment utilization rates are usually low. d. Material handling is slower, less efficient, and more costly per unit than with a product layout. e. There is often a lower span of supervision compared to a product layout. f.
Unit costs tend to be higher than comparable output produced with a product layout.
g. Accounting, inventory control and purchasing are generally more involved than with a product layout. 13.
The main goal of line balancing is to achieve a set of task groupings at work stations in the line that have equal time requirements in order to get a high utilization of labor and equipment. Unbalanced lines have bottlenecks at some work stations and idle time at others. The resulting output is lower than it would be if the line were balanced.
14.
Routing and scheduling are continual problems in a process layout because a variety of jobs pass through the system, and they tend to differ in terms of routing and schedule requirements. In contrast, product layouts typically handle items with little or no variety²all have the same or similar routing and scheduling requirements.
15.
With a product layout, equipment breakdown has serious implications because the separate pieces of equipment are closely tied together. If one piece of equipment fails, the line will quickly come to a halt. Consequently, preventive maintenance to reduce the failure rate is advisable. In contrast, a process layout often contains duplicative equipment so that if one particular piece of equipment fails, the work can usually be shifted to another piece of equipment. Consequently, there is less need for preventive maintenance, and less need for repair of equipment when it does break down. Moreover, process layouts utilize more skilled workers who tend to take better care of the equipment than their lower skilled counterparts in a product layout system.
16.
Job sequence usually determines the arrangement of equipment in a product layout. In a process layout, job sequences vary, so there is much less influence on equipment arrangement. Because of differences in job requirements, sequencing is a continual task in a process layout.
17.
The subway system is essentially a fixed-path arrangement²a product layout. Its advantages are often low operating cost, more efficient handling, and low cost per unit moved. On the other hand, a bus system is more flexible in terms of varying routes. This can be desirable if there are shifts in which potential riders are coming from and going to. For example, a new bus route could easily be established to service a new shopping area, a new apartment complex, or a large industrial facility. Other considerations are initial cost (high for subway and relatively low for bus), severity of difficulties that would arise from a breakdown (high for subway, low for bus), the possibility of alternative uses (none for subway, private groups, etc., for bus during off times), and possible disruptions caused by weather (higher risk for bus than subway²e.g., snowstorms stall highway traffic).
18.
Fixed-path material handling equipment in supermarkets includes the belts at the checkouts which move items up to the cashier, the roller conveyors which transport boxes of groceries outside to pickup areas, conveyors in the meat department to move carcasses from storage to cutting tables, roller conveyors to off-load goods from trucks and move them to storage. Variable-path material handling equipment includes grocery carts, ³trucks´ and ³jeeps´ used to transport baked goods from storage to display shelves, and movable racks to transport baked goods from ovens or from deliveries to the bakery counter.
19.
Heuristic approaches are rules designed to guide decision-makers to satisfactory decisions by reducing the number of alternatives that must be considered. They do not necessarily yield optimal solutions. They are usually employed when there is a problem involving an exceedingly large number of potential solutions and an optimizing algorithm is not available.
20.
Nonmanufacturing environments do not usually lend themselves to product layouts because they tend to involve more processing variety than many manufacturing environments.
21.
The original car was probably one of a large number of similar cars produced on an assembly line, which was set up to speed the flow of work. That is, inventories of parts were on hand, specialized machinery, workers and material handling equipment were arranged specifically for the job. As a result of this continuous processing, the unit cost of the car was relatively low. In contrast, constructing a car from ³scratch´ is essentially a cross between intermittent processing and a project, with none of the economies of continuous processing. A list of the parts must be assembled. Some might be available locally, but others would have to be shipped individually from suppliers. The parts would have to be held until all were on hand. Workers would not be highly familiar with this particular car, even though they were experienced in this sort of work. Consequently, the work would progress at a fairly slow rate, and probably with a certain amount of back-tracking. Obviously, construction of a replacement would be considerably more costly than initial, c ontinuous production.
22.
Layout can lead to high productivity if it contributes to a smooth flow of work with high utilization of labor and equipment. This requires careful consideration of future work requirements to determine what will be needed and a certain amount of effort to obtain an optimal (or satisfactory) layout. A poor layout will hinder productivity with bottlenecks, lower utilization of labor and equipment than is necessary, and require more handling or movement between work stations than is necessary (particularly in process layouts).
23.
In cellular manufacturing, machines are grouped into cells. The basis for grouping can be operations needed to process a group of similar items or part families. Advantages of such systems include relatively short throughput time, r educed material handling, less work-in-process inventory, and reduced setup time.
24.
Group technology involves items that have similar design or processing requirements and grouping them into part families for cellular manufacturing. It also includes a coding system for items.
25.
Although we treated the task completion times as fixed in balancing assembly lines, it is more realistic to assume variable task times whenever humans are involved. The lower the level of automation, the higher the variability of tasks. If the assembly line consists of tasks with variable completion times, it will be more difficult to balance the line. In order to deal with variability of task times, we can require a minimum amount of slack to be available at each workstation. As the variability of task times increase we can increase the minimum slack available at each workstation. In addition, workstation slack time can also be used for slower or less experienced workers who take longer than normal to c omplete a task.
Taking Stock 1.
The three major trade-offs in process selection are: a.
Flexibility vs. efficiency in facilities layout. Product layout is designed to pr ovide efficient operations, while process layout is designed to provide a variety of products, thus offering a flexible system.
b.
Level of automation (high vs. low) High level of automaton has the potential advantage of providing faster production or service, the ability to quickly switch from product to product resulting in higher flexibility. On the other hand, high level of automation involves higher cost and the potential risk that it may involve costly implementation problems.
c.
The expected volume of output can either be high or low. If it is high, we can take advantage of the economies of scale and reduce costs and improve efficiency. However, if we make a commitment to high volume production and the demand is consistently low, we may be faced with the potential problem of low efficiency and low utilization of the machines and idle resources. On the other hand, if the expected volume is low, then we probably have decided
to compete as a job-shop, emphasizing flexibility. If there is a capacity-demand mismatch, we will either have too few resources allocated for production or we will have a capacity constraint on resources. 2.
If we rebalance the assembly line too frequently, then the cost of making the adjustments becomes too costly. On the other hand, if we do not rebalance it as frequently as necessary, then the assembly line will experience too much inefficiency resulting in a less efficient line.
3.
In process selection, we must make sure that manufacturing group(s), maintenance, engineering, technical support, marketing, process design specialists, quality, finance (especially if we need capital to support the facility layout, new equipment or new machinery) are involved. Of course we also need to make sure that there is a representative from top management to ensure that we stay consistent with the overall goals and objectives of the firm.
4.
In layout design, we must make sure that manufacturing group(s), maintenance, engineering, technical support, process design specialists, quality, finance (especially if we need capital to support the facility layout, new equipment or new machinery) are involved.
5.
Technology has tremendous impact on process selection due to c hanges in computer related technology. The level of automation continues to change in companies affecting the layout decisions. For example, the newer machinery are smaller, therefore the size of the machinery affects the work area size and ultimately the layout of the facility.
Critical Thinking Exercises 1.
2.
Factors that must exist in order to make automation feasible are: a.
The level of demand: The demand must be forecasted. Generally, we need high volume of output to justify the high cost associated with automation.
b.
The degree of variability required in the manufacturing or the service system: The higher the degree of variability required, the less the chance of success for automation.
c.
Strategic fit with the overall goals and objectives of the company: If the type of automation does not lend itself to flexible manufacturing, but the objectives and goals of the company involve low volume large variety of products, we could have significant capacity-demand mismatch problems due to this misalignment.
Factories²type of machines, skill level of the employees, level of automation, inventories, safety. Supermarkets²maximizing sales potential, minimizing inventory investment, level of automation, type of automation, number of cashier lines, proximity and location of various departments within the supermarket. Department store²maximizing sales potential, minimizing inventory investment, level of automation, type of automation, proximity²distance and location of various departments within the department store, capacity and convenience of the p arking lot.
Memo Writing Exercises (included on the DVD) 5.
1. In most cases it is not feasible to perfectly balance a production line. First, there are technological constraints dealing with precedence and incompatibility issues. In other words, certain tasks have to be performed before others (precedence) and two tasks may not be performed at the same station due to their incompatibility (space and nature of operation considerations). Secondly, there are output constraints. Since most task times vary, output constraint determines whether an otherwise eligible task will fit at a workstation because sum of the task times assigned to a station cannot exceed the cycle time. As a result of both technological
and output constraints, it is extremely difficult to achieve a perfectly balanced production line. The larger the number of tasks, the more difficult it is to achieve perfect balance. 6.
2. Producing two products on the same assembly line allows the company to utilize the same workstations to produce the common parts. This results in synergy on the line. If one of the products is new, the company can shorten the period of time from design to actual production, and reduce the cost of manufacturing in the long run.
7.
3. Fixed automation is utilized in a continuous flow/mass production environment. It enables the firm to manufacture a single or a few products at high volume and low cost. However, it is not flexible enough to produce a variety of parts and it is very costly to make changes to the process. Flexible automation is utilized in a job shop (intermittent) environment, where a wide variety of products can be produced without significant changeover (setup) time/cost. Flexible machinery is not designed for high volume (mass) production.
Solutions 1.
OT = 450 minutes a. Minimum cycle time = length of longest task, which is 2.4 minutes. Maximum cycle time = 7 task times = 18 minutes. b. Range of output:
c.
d. e. Potential output:
(1)
(2) 2.
Desired output = 33.33 units per hour Operating time = 60 minutes per hour
Solutions (continued)
a. Task
Number of following tasks
Positional Weight
A
7
6
B
6
4.6
C
2
1.6
D
2
2.2
E
2
2.3
F
1
1.0
G
1
1.5
H
0
0.5
Assembly Line Balancing Table (CT = 1.8)
Task
Task Time
I
A
1.4
0.4
±
II
B
0.5
1.3
C, D, E
E
0.8
0.5
±
D
0.7
1.1
C
C
0.6
0.5
F
F
0.5
0
±
G
1.0
0.8
H
H
0.5
0.3
±
III
IV
b.
Time Remaining
Feasible tasks Remaining
Work Station
Assembly Line Balancing Table (CT = 1.8)
Task
Task Time
I
A
1.4
0.4
±
II
B
0.5
1.3
C, D, E
E
0.8
0.5
±
D
0.7
1.1
C
C
0.6
0.5
F
F
0.5
0
±
G
1.0
0.8
H
H
0.5
0.3
±
III
IV
Solutions (continued)
c. 3.
Time Remaining
Feasible tasks Remaining
Work Station
Desired output = 4 Operating time = 56 minutes
Task # of Following tasks
Positional Weight
A
4
23
B
3
20
C
2
18
D
3
25
E
2
18
F
4
29
G
3
24
H
1
14
I
0
5
Solutions (continued)
a. First rule: most followers. Second rule: largest positional weight. Assembly Line Balancing Table (CT = 14)
Task
Task Time
I
F
5
9
A,D,G
A
3
6
B,G
G
6
±
±
D
7
7
B, E
B
2
5
C
C
4
1
±
E
4
10
H
H
9
1
±
I
5
9
±
II
III
IV
Time Remaining
Feasible tasks Remaining
Work Station
b. First rule: Largest positional weight.
Assembly Line Balancing Table (CT = 14)
Task
Task Time
I
F
5
9
A,D,G
D
7
2
±
G
6
8
A, E
A
3
5
B,E
B
2
3
±
C
4
10
E
E
4
6
±
H
9
5
I
I
5
±
II
III
IV
Time Remaining
Feasible tasks Remaining
Work Station
c. Solutions (continued)
4.
a, b a. l.
2. Minimum Ct = 1.3 minutes Task
Following tasks
a
4
b
3
c
3
d
2
e
3
f
2
g
1
h
0
Work Station
Eligible
Assign
Time Remaining
I
a
A
1.1
b,c,e, (tie)
B
0.7
C
0.4
E
0.3
0.3 0.0
II
d
D
0.0
III
f,g
F
0.5
Idle Time
IV
h
G
0.2
0.2
H
0.1
0.1 0.6
3.
4.
Solutions (continued)
b. 1. 2. Assign a, b, c, d, and e to station 1: 2.3 minutes [no idle time] Assign f, g, and h to station 2: 2.3 minutes
3.
4. 5.
a.
b. The minimum cycle time = maximum task time =1.2 minutes The maximum cycle time = .2 +.4 +.2 +.4 +1.2 +1.2 + 1.0 = 4.6 minutes
c.
d. Task
Number of following tasks
A
4
B
3
C
2
D
2
E
1
F
1
G
0
Solutions (continued)
Assembly Line Balancing Table (CT = 2 minutes)
Work Station
Task
Task Time
Time Remaining
Feasible tasks Remaining
I
A
0.2
1.8
B,D
B
0.4
1.4
C, D
D
0.4
1.0
C
C
0.2
0.8
±
II
E
1.2
0.8
±
III
F
1.2
0.8
±
IV
G
1.0
1.0
±
e.
6.
a.
(1,2)
Positional weights in parentheses
Solutions (continued)
6.
b. Using both the greatest positional weight and the greatest number of following tasks rules result in the following balance.
Assembly Line Balancing Table (CT = 1.5 minutes)
Work Station
Task
Task Time
Time Remaining
Feasible tasks Remaining
I
A
0.1
1.4
B
B
0.2
1.2
C
C
0.9
0.3
E
E
0.1
0.2
±
D
0.6
0.9
F
F
0.2
0.7
G
G
0.4
0.3
H
H
0.1
0.2
I
I
0.2
±
±
J
0.7
0.8
K
K
0.3
0.5
L
L
0.2
0.3
±
II
III
Total idle time = 0.2 + 0 + 0.3 = 0.5 c. For positional weights and greatest number of following tasks
7.
a.
Solutions (continued)
b.
.84 minutes = 50.4 seconds (maximum cycle time)
Minimum cycle time = maximum task time = 45 seconds (results in 560 units of production)
c. d. Task
Number of followers
*PW
A
6
106
B
5
61
C
4
50
D
4
106
E
3
56
F
2
30
G
2
31
H
2
29
I
1
19
J
0
10
*Positional weight CT = 50 seconds
Work Station
Task
Task Time
Time Remaining
Feasible tasks Remaining
I
A
45
5
±
III
D
50
±
±
III
B
11
39
C, E
E
26
13
C, F
C
9
4
±
G
12
38
H, F
F
11
27
H
H
10
17
I
I
9
8
±
IV
V
J
10
40
±
Solutions (continued)
e.
8.
b. Station
Tasks
Time
Idle/Time
1
a,b
1.9
.1
2
c,d
1.9
.1
3
e,f,i
2.0
0
4
g,h,j
1.5
.5
5
k,m
1.2
.8 1.5
c.
Positional Weight
Tasks a
8.5 b
4.6
c
4.4
d
4.2
e
3.2
f
3.5
g
1.9
h
1.5
i
2.5
j
2.0
k
1.2
m
.3
Solutions (continued)
Work Station
Task
I
a
Task Time
Time Remaining
.5
Feasible tasks Remaining b, c, d
1.5
II
b
1.4
c
1.2
.1
± d, e .8
III
d
.7
.1
f
1.0
1.0
e, i
e
.5
.5
i, g
i
.5
± 0
IV
j
.8
g
.4
1.2
g h .8
h
.3
k
.9
.5
± m 1.1
m
.3
Total idle time = .1 + .1 + 0 + .5 + .8 = 1.5 minutes
d. Balance delay: part b and c 1.5/10 = 15%
.8
±
1
4
3
2
5
6
1
5
4
3
8
7
6
2
9.
11.
Solutions (continued)
12.
3
1
4
8
5
1
4
8
Or
5
1
4
6
Or
5
2
7
6
3
2
7
6
3
2
7
8
5
1
7
8
3
1
7
8
3
1
4
6
5
2
7
8
Or
Or
3
2
4
6
5
2
4
6
3
1
7
6
5
1
7
6
3
2
4
8
Or 5
13.
8.
2
4
8
3
1
8
9
7
4
5
2
6
14.
First rank or arrange the number of trips from high to low.
9.
Department
Number of trips
10.
2-4
90
11.
1-4
80
12.
3-4
55
13.
2-3
40
14. From this we can see that departments 2 and 4 have the greatest interdepartmental work flow, so they should be close, perhaps locations C and B. Next, we can see that the work flows for 1 and 4, and 3 and 4 are high. Therefore department 4 has to be located at a central location (location B), while department 2 is in location C, department 1 is in location A, and department 3 is in location D. Distance * Number of trips matrix Department
1
2
3
4
1
±
(10 x 80) = 800
(20x 70) = 1400
(80 x 40) = 3200
2
±
±
(40 x 60) = 2400
(90 x 40) = 3600
3
±
±
±
(55 x 50) = 2750
4
±
±
±
±
Total cost = $14,150
Solutions (continued)
15.
No. of trips (two way)
Order of Assignment
1±2
10
1±3
5
1±4
90
11
1±5
370
1
1±6
135
6
1±7
125
7
1±8
0
2±3
360
2
2±4
120
8 (tie)
2±5
40
2±6
115
2±7
45
2±8
120
8 (tie)
3±4
350
3
3±5
110
10
3±6
40
3±7
20
3±8
200
No. of trips (two way)
A reasonable (intuitive) set of assignments is:
9
A #1
B #5
C #7
D #4
E #3
F #6
G #2
H #8
This set of assignments has a total cost of $143,650 per day.
4
Order of Assignment
4±5
190
5 (tie)
4±6
70
12
4±7
50
4±8
190
5±6
10
5±7
40
5±8
10
6±7
50
6±8
20
7±8
20
5 (tie)
Slight variations would also be reasonable, as long as departments 2, 4 and 8 are close to 3, 4 is close to 5, and 5 is close to 1.
Solutions (continued) 16. No. of trips (two way) 1±2
0
1±3
40
1±4
110
3±A, 5±B, 1±C, 4±D, 6±E, 2±F.
1±5
80
An equivalent solution is the reverse order:
1±6
50
2±F, 6±B, 4±C, 1±D, 5±E, 3±F.
2±3
0
2±4
50
2±5
40
2±6
120
3±4
10
3±5
250
3±6
10
4±5
40
4±6
90
5±6
20
A reasonable (intuitive) assignment is:
(Ignore Reception since all locations are the same distance from it.)
15. 16.
17. Two-way trips can not be used here because of the one-way route restriction. Consequently, students are forced to develop a heuristic that will yield reasonable assignments. One possible heuristic is the following: 17. Beginning with Department 1, identify the department which receives the greatest number of trips from that department (e.g., 40 to Department 2). Assign that department to the next location counter-clockwise. 18. For that department (e.g., 2) identify the department which receives the greatest number of trips (e.g., 5) and assign it to the next position. 19. Continue in this manner until all departments have been assigned. 20. The resulting set of assignments for this problem is: A±1, 2±B, 5±C, 4±D, 9±E, 8±F, 6±G, 10±H, 7±I, 3±J. 21. Students may raise the question about return trips to the original departments after delivery, which would seem to make all locations comparable. Three possible explanations are: 22. 1. Return trips cost less because they are unloaded. 23. 2. Unloaded trips may be permitted to move clockwise. 24. 3. Material handlers (?) pick up new load at each new department and move it to the next department. (The last explanation seems to appeal most to students.)
Solutions (continued)
Task
I
D
50
0.4
±
II
A
45
5.4
±
III
E
26
24
B ,F
B
11
13
C, F
F
11
2.4
±
C
9
41
G, H
G
12
29
H
H
10
19
I
I
9
10
J
J
10
0.4
IV
Task Time
Time Remaining
Feasible tasks Remaining
Work Station
Reading: Designing Supermarkets This reading provides the student with an example of how a supermarket is laid out and why the arrangement is done in a particular or specific way. It is a nice change of pace from the typical manufacturing layout article.
Operations Tour: Morton Salt 1.
Steps in salt production for Morton are: a. Inject water into salt caverns below the surface and let the salt deposits dissolve in the water. b. Pump the resulting brine to the surface. c. Boil the brine, let the liquid evaporate leaving salt crystals and residual moisture. d. Dry the salt to remove the residual moisture. e. Store the salt in silos. f.
Move the salt to dedicated production areas.
g. Produce the cans by forming a cylinder (two sheets of chip board are glued together) . h. Roll the cylinder into a continuous tube. i.
Cut the tubes into can-size pieces.
j.
Assemble and glue the separate pieces constituting the can.
k. Fill the cans with salt. l.
Load the filled cans onto pallets and store them in inventory.
2.
Quality is checked during different stages of the production process. a. Check salt for purity using chemical analysis. b. Assure appropriate crystal size by forcing the salt through a scraping screen. c. Remove the small pieces of metal by magnets at different stages of the process. d. Check the weight of the filled cans, attach the label sticker. e. Check to make sure that metal pour spouts are correctly attached.
3.
The company may not have updated its equipment because of the high cost of investment in new machinery.
4.
Salt production would be a low variety, high volume operation which would place it as a repetitive production or continuous flow in the product-process matrix.
5.
(3,800,000 cans per year) x (26 ounces of salt per can) = 98,800,000 ounces per year. (98,800,000 ounces per year) / (16 ounces per pound) = 6,175,000 pounds per year. (6,175,000 pounds per year) / (2000 pounds per ton) = 3,087.5 tons of salt per year.
6.
Suggested improvements include the following: a. Application of Statistical Process Control (SPC) to reduce the cost of quality. b. Develop a plan to overhaul the existing equipment and to purchase new equipment as a joint effort among finance, purchasing and manufacturing areas. c. Synchronize production, distribution and capacity planning to make sure that there is sufficient capacity in the silos to handle the incoming salt from brine production.
Reading: Tour De Force 1.
The Viper/Prowler assembly plant is much smaller than typical automobile assembly plants. The plant covers 392,000 square feet of space as opposed to other typical auto assembly plants that cover from 2 million square feet to 5 million square feet of space. The production capacity of the Viper plant is much less than a typical automobile assembly line. The Viper plant¶s daily production capacity is 13 Vipers and 20 Prowlers compared to large automobile assembly plants that can manufacture 1000 vehicles per day. While most large automobile plants require 2000 or more workers, the Viper plant employs only 260 employees. The Viper plant employs skilled ³craftsman´ workers. Typical auto assembly plants use workers to do repetitive work with little skill required. There are no robots or automation in the Viper plant while most auto assembly plants have high levels of automation. The Viper plant uses early 20 th century manual assembly techniques on two manual, parallel, relatively short (12 work stations and 720 feet long) assembly lines with generous idle time built in. Typical assembly lines usually involve the use of robots, large number of workstations and very little idle time.
2.
The reasons for not having robots or other high level automation include the following: Chrysler Corporation wants to portray a high quality image of two handcrafted automobile models that is generally more expensive and appealing to high-income individuals. The personal attention to the customers is part of the marketing package associated with both products. The company also wants to draw attention to this facility and the two car models (Viper and Prowler) manufactured at this facility because it is an unusual and attractive automobile manufacturing facility. Chrysler Corporation is hoping that not only will it draw attention to the two hand-crafted automobile models produced within the facility but also possibly improve the general goodwill associated with the company.
Reading: My Compliments to the Chef ± er, Buyer 1.
³Hours vs. Ours´ refers to pre-made food companies advertising of their products. This advertisement slogan simply suggests that if you decide to cook it yourself, it will take ³hours´ to prepare the meal. However, if you use ³our´ product, it will be ready to be served very quickly.
2.
The main advantages of outsourcing for restaurants is reduction of food preparation cost, kitchen costs, and in most cases total cost of the dish served. Since the total cost of the dish is less, the restaurant can offer a lower price. In addition to reduction of cost, r estaurants will be able to prepare the outsourced meal much quicker and consistently than if they were preparing it from scratch.
3.
The disadvantages of restaurant outsourcing include possible reduction in quality and implicit ³from scratch´ food preparation expectations of the customers. In other words, if the customers find out that the meal they just ate was a frozen pre-made package, they may be disappointed.
4.
Even though there may be an implied expectation of ³from scratch´ meal preparation in certain types of restaurants, as long as there is no explicit statement of fr esh meal preparation, the restaurant outsourcing is not unethical. What counts is what the meal looks like and what it tastes like given the type of restaurant.
5.
In effect, outsourcing increases capacity by freeing up resources that would otherwise be engaged.
Enrichment Module: Process Design and Facility Layout Problem Job-Shop
layout problem
Donald Rice sold the building that housed the restaurant/lounge he owned and operated for the last 10 years and has recently purchased a larger building in a new location. Mr. Rice hopes to operate a new restaurant and expand his growing business. The building has four equal size r ooms. Donald¶s restaurant consists of four major departments (areas of his operation): 1.
Dining area
2.
Lounge/Bar
3.
Kitchen
4.
Storage/Refrigeration/Loading area
Donald envisioned using the four rooms to occupy four areas of his operation. The distance matrix among the four rooms is as follows (all distance values are given in feet):
Distance Matrix
Room
1
2
3
4
1
±
25
45
35
±
60
20
±
10
2 3 4
±
Based on his experience from his previous restaurant, he estimated the following number of trips per hour between departments: Load Matrix
Dining Dining
Lounge
Kitchen
60
80
10
40
20
Lounge Kitchen
Storage
100
Storage a.
Donald is thinking about using the following departmental layout. Room 1
Room 2
Room 3
Room 4
Dining
Kitchen
Lounge
Storage
Determine the (distance x trip) matrix for the above layout. What is the total distance? b.
Determine a layout and the associated trip x distance matrix that will result in a lower total distance (Hint: Locate the departments that have a high traffic close to each other).
Solution of Problem 1
a.
Distance x Load Matrix
To Dining From
Lounge
Dining
Lounge
Kitchen
Storage
±
*2,700
**2,000
***350
2,400
200
±
Kitchen Storage
±
2,000 ±
* (45 x 60) = 2,700 **(25 x 80) = 2,000 ***(35 x 10) = 350 Total distance = 2,700 + 2,000 + 350 + 2,400 + 200 + 2,000 = 9,650 feet b.
The objective is to arrange the departments such that the departments with high interdepartment movements (# of trips) are close to one another.
Since the number of trips between kitchen and storage is the highest and room 3 and room 4 (100) have the closest proximity (shortest distance of 10 feet), we will place kitchen and storage in rooms 3 and 4. However, at this point we have not decided which of the two departments will be placed in room 1 and room 2. We can observe that the next highest number of trips is between dining and kitchen (80). In addition, the shortest distance from rooms 1 and 2 to rooms 3 and 4 is 20 feet (room 2 to room 4). Therefore, kitchen is placed in room 4, storage is placed in room 3, dining is placed in room 2 and the lounge is placed in room 1. The summary of the room assignments are given below: Room 1²Lounge Room 2²Dining Room 3²Storage Room 4²Kitchen Updated (Distance) x (Load) Matrix
To Dining From
Lounge
Dining
Lounge
Kitchen
Storage
±
*1,500
**1,600
***600
1,400
900
±
Kitchen
±
Storage * (45 x 60) = 2,700 **(20 x 80) = 1,600 ***(60 x 10) = 600 Revised total distance = 1,500 + 1,600 + 600 + 1,400 + 900 + 1,000 = 7,000 feet Reduction in total distance = 9,650 ± 7,000 = 2,650 feet.
1,000 ±
1. Process selection involves making choices concerning the way an organization will produce its products or provide services to its customers. It has major implications for capacity planning, layout and work methods. 2. Managers can select from five different types of processes: job shop, batch, repetitive, continuous and projects. Job shops are used to produce a low volume of each of a large variety of products or services. Equipment flexibility must be high to handle the high variety of jobs. Batch processing involves less variety, less need for equipment flexibility, and higher volumes of each type of product. Repetitive processing has even less variety, less need for equipment flexibility, and higher volume. Continuous processing has the lowest variety, the lowest need for equipment flexibility, and the highest volume. Job shops and batch processing are classified as intermittent systems, meaning that output frequently switches from one product or service to another. Repetitive and continuous systems are classified as continuous processing because there is little or no switching from one product to another. Projects are used for non-routine work that is intended to meet a given set of objectives in a limited time frame. Job variety is high, volume is usually low, and equipment flexibility needs can range from low to high. 3. Process selection may lead to automation or computer-aided manufacturing. [You should find it helpful to list the different types of computer-aided manufacturing, along with a brief description and advantages and limitations of each type.] 4. A key issue in process selection is the management of technology. See the discussion under the Operations Strategy section. Another key issue in process selection is flexibility. 5. There are three fundamental types of plant layout, respectively corresponding to the three different types of production operations situations. a.
A product layout implies that a single product or else a single type of product, for example, automobiles, is manufactured on an assembly line, with the production tasks assigned to workstations along the line. b. A process layout involves the movement of batches of goods between departments via forklift truck, moving belt, or some other type of conveyance. c. A fixed-position layout is appropriate for a large end item such as a house or airplane, where all material is assembled to a major structure or product at a specified site. 6. A product layout such as that associated with automobile factories is a good idea when it is justified by the volume. The advantages of product layout are that it involves continuous flow of the work in process, minimum work-in-process inventory, maximum specialization, low material handling costs, efficient utilization of labor and equipment, and systematized routing, purchasing, accounting and inventory control. The disadvantages are dull repetitive jobs, inflexibility and susceptibility to frequent shutdowns.
7. A process layout allocates floor space to work centers so as to sustain a logical flow of semi-finished goods, and minimize transportation and inventory costs. It is more flexible than product layout in the sense that a variety of products can be made without incurring extensive changeover costs. It also makes better use of the specialized skills of employees, so that incentive pay systems can be effective in enhancing productivity. Process layout is appropriate when each type of product or semi-finished goods has low volume, but there are potentially high costs for unused equipment, excess inventory, slow or irregular movement, and a need for extensive production control paperwork. 8. A fixed-position layout is appropriate for large construction projects or for assembly of very large products such as airplanes, which are difficult to move. An example of a fixed position service system is a subway, which is an economical way to move large masses of people.
