Facility Design-Week 4 Material Flow Analysis By Anastasia L. Maukar

Flow Analysis Factors that Affect the Flow Pattern Flow Analysis Information Flow Patterns a. Flow within Workstations b. Flow within Departments c. Flow between Departments Flow Planning Measuring Flow Types of Layout a. Fixed Location b. Product c. Group Technology d. Process e. Hybrid Flow Dominance Measure

Factors that Affect the Flow Pattern Number of parts in each product Number of operations on each part Sequence of operations in each part Number of subassemblies Number of units to be produced Product versus process type layout Desired flexibility Locations of service areas The building . . . .

Flow Analysis Information Assembly Chart Operation Process Chart (OPC) Multi-Product Process Chart (MPPC) String Diagram Process Chart Flow Process Chart Flow Diagram From-to Chart/Travel Chart Triangular Flow Diagram Activity Relationship Chart (ARC) dan Activity Relationship Diagram (ARD) Procedure Chart Critical Path Network

Assembly Chart It is an analog model of the assembly process. Circles with a single link denote basic components, circles with several links denote assembly operations/subassemblies, and squares represent inspection operations. The easiest method to constructing an assembly chart is to begin with the original product and to trace the product disassembly back to its basic components.

Operations Process Chart By superimposing the route sheets and the assembly chart, a chart results that gives an overview of the flow within the facility. This chart is operations process chart.

Multi-Product Process Chart This chart is a flow process chart containing several products.

String Diagram

Flow Process Chart This chart uses circles for operations, arrows for transports, squares for inspections, triangles for storage, and the letter D for delays. Vertical lines connect these symbols in the sequence they are performed.

Other Flow Process Chart

Flow Diagram It depicts the probable movement of materials in the floor plant. The movement is represented by a line in the plant drawing.

From-To Chart This chart is a matrix that contains numbers representing a measure (units, unit loads, etc.) of the material flow between machines, departments, buildings, etc.

Triangular Flow Diagram

Flow Patterns: Flow within Workstations Motion studies and ergonomics considerations are important in establishing the flow within workstations. Flow within workstations should be: Simultaneous: coordinated use of hands, arms and feet. Symmetrical: coordination of movements about the center of the body. Natural: movements are continuous, curved, and make use of momentum. Rhythmical and Habitual: flow allows a methodological and automatic sequence of activities. It should reduce mental, eye and muscle fatigue, and strain.

Flow Patterns: Flow within Departments The flow pattern within departments depends on the type of department. In a product and/or product family department, the flow follows the product flow. 1 machine/operator 2 machines/operator More than 2 machines /operator 1 machine/operator

Flow Pat.: Flow within Departments (cont.) In a process department, little flow should occur between workstations within departments. Flow occurs between workstations and aisles. Uncommon Aisle Aisle One way Aisle Aisle One way Dependent on interactions among workstations available space size of materials

Flow Pat.: Flow between Departments Flow between departments is a criterion often used to evaluate flow within a facility. Flow typically is a combination of the basic horizontal flow patterns shown below. An important consideration in combining the flow patterns is the location of the entrance (receiving department) and exit (shipping department). Similar to straight. It is not as long. Simplest. Separate receiving/shipping crews L flow Straight Very popular. Combine receiving /shipping. Simple to administer Circular flow U flow Terminate flow. Near point of origin Serpentine When line is too long S flow

Flow within a facility considering the locations of entrance and exit At the same location On adjacent sides

On the same side but at opposite ends Flow within a facility considering the locations of entrance and exit (cont.) On the same side but at opposite ends On opposite sides

Vertical Flow Pattern Flow between buildings exists and the connection between buildings is elevated Ground level ingress (entry) and egress (exit) occur on the same side of the building Ground level ingress (entry) and egress (exit) are required Some bucket and belt conveyors and escalators result in inclined flow Travel between floors occurs on the same side of the building Backtracking occurs due to the return to the top floor

Flow Planning Uninterrupted flow paths Interrupted flow paths Planning effective flow involves combining the above patterns with adequate isles to obtain progressive movements from origin to destination. An effective flow can be achieved by maximizing directed flow paths, reducing flow, and minimizing the costs of flow. A directed flow path is an uninterrupted flow path progressing directly from origin to destination: the Figure below illustrates the congestion and undesirable intersections that may occur when flow paths are interrupted. Uninterrupted flow paths Interrupted flow paths

Flow Planning (cont.) The reduction of flow can be achieved by work simplification including: 1. Eliminating flow by planning for the delivery of materials, information, or people directly to the point of ultimate use and eliminate intermediate steps. 2. Minimizing multiple flows by planning for the flow between two consecutive points of use to take place in as few movements as possible. 3. Combining flows and operations whenever possible by planning for the movement of materials, information, or people to be combined with a processing step. Minimizing the cost of flow can be achieved as follows: 1. Reduction of manual handling by minimizing walking, manual travel distances, and motions. 2. Elimination of manual handling by mechanizing or automating flow.

Measuring Flow 1. Flow among departments is one of the most important factors in the arrangement of departments within a facility. 2. Flows may be specified in a quantitative manner or a qualitative manner. Quantitative measures may include pieces per hour, moves per day, pounds per week. Qualitative measures may range from an absolute necessity that two departments show be close to each other to a preference that two departments not being close to each other. 3. In facilities having large volumes of materials, information, a number of people moving between departments, a quantitative measure of flow will typically be the basis for the arrangement of departments. On the contrary, in facilities having very little actual movement of materials, information, and people flowing between departments, but having significant communication and organizational interrelation, a qualitative measure of flow will typically serve as the basis for the arrangement of departments. 4. Most often, a facility will have a need for both quantitative and qualitative measures of flow and both measures should be used. 5. Quantitative flow measure: From-to Chart Qualitative flow measure: Relationship (REL) Chart

Quantitative Flow Measurement A From-to Chart is constructed as follows: 1. List all departments down the row and across the column following the overall flow pattern. 2. Establish a measure of flow for the facility that accurately indicates equivalent flow volumes. If the items moved are equivalent with respect to ease of movement, the number of trips may be recorded in the from-to chart. If the items moved vary in size, weight, value, risk of damage, shape, and so on, then equivalent items may be established so that the quantities recorded in the from-to chart represent the proper relationships among the volumes of movement. 3. Based on the flow paths for the items to be moved and the established measure of flow, record the flow volumes in the from-to chart.

Example 1 From-to Chart Stores Milling Turning Press Plate Assembly Warehouse – 12 6 9 1 4 – – – – – 7 2 – – 3 – – 4 – – – – – – 3 1 1 – 3 1 – – 4 3 1 – – – – – 7 – – – – – – – Stores Turning Milling Press Plate Assembly Warehouse – 6 12 9 1 4 – – – 3 – 4 – – – – – – 7 2 – – – – – 3 1 1 – 1 3 – – 4 3 1 – – – – – 7 – – – – – – – Revised Flow Pattern Original Flow Pattern

Flow Patterns Straight-line flow U-shaped flow S-shaped flow Press Store Turning Milling Press Plate Assembly Warehouse Stores Turning Milling Warehouse Assembly Plate Straight-line flow U-shaped flow Stores Press Plate Assembly Turning Milling Warehouse Stores Milling Warehouse Turning Press Plate Assembly S-shaped flow W-shaped flow

Flow Patterns (cont.) Straight-line flow U-shaped flow S-shaped flow Press Store Turning Milling Press Plate Assembly Warehouse Stores Turning Milling Warehouse Assembly Plate Straight-line flow U-shaped flow Stores Press Plate Assembly Turning Milling Warehouse Stores Milling Warehouse Turning Press Plate Assembly S-shaped flow W-shaped flow

Group Technology Layout Types of Layout Volume High Medium Low Product Planning Department Product Layout Product Family Planning Department Fixed Location Layout Process Layout Group Technology Layout Fixed Materials Location Planning Department Process Planning Department Low Medium High Variety

Fixed Product Layout Lathe Press Grind Warehouse Storage Weld Paint Assembly

Fixed Product Layout

Fixed Product Layout (cont.) Advantages 1. Material movement is reduced. 2. Promotes job enlargement by allowing individuals or teams to perform the “whole job”. 3. Continuity of operations and responsibility results from team. 4. Highly flexible; can accommodate changes in product design, product mix, and product volume. 5. Independence of production centers allowing scheduling to achieve minimum total production time. Limitations 1. Increased movement of personnel and equipment. 2. Equipment duplication may occur. 3. Higher skill requirements for personnel. 4. General supervision required. 5. Cumbersome and costly positioning of material and machinery. 6. Low equipment utilization.

Product Layout Storage Lathe Drill Grind Drill Assembly Warehouse Press Bend Drill Mill Drill Lathe Lathe Drill

Product Layout

Product Layout (cont.) Advantages 1. Since the layout corresponds to the sequence of operations, smooth and logical flow lines result. 2. Since the work from one process is fed directly into the next, small in-process inventories result. 3. Total production time per unit is short. 4. Since the machines are located so as to minimize distances between consecutive operations, material handling is reduced. 5. Little skill is usually required by operators at the production line; hence, training is simple, short, and inexpensive. 6. Simple production planning control systems are possible. 7. Less space is occupied by work in transit and for temporary storage.

Product Layout (cont.) Limitations 1. A breakdown of one machine may lead to a complete stoppage of the line that follows that machine. 2. Since the layout is determined by the product, a change in product design may require major alternations in the layout. 3. The “pace” of production is determined by the slowest machine. 4. Supervision is general, rather than specialized. 5. Comparatively high investment is required, as identical machines (a few not fully utilized) are sometimes distributed along the line.

Process Layout Storage Lathe Lathe Drill Weld Weld Warehouse Lathe Paint Paint Mill Mill Grind Assembly Mill Mill Grind Assembly

Process Layout

Process Layout (cont.) Advantages Limitations 1. Better utilization of machines can result; consequently, fewer machines are required. 2. A high degree of flexibility exists relative to equipment or man power allocation for specific tasks. 3. Comparatively low investment in machines is required. 4. The diversity of tasks offers a more interesting and satisfying occupation for the operator. 5. Specialized supervision is possible. Limitations 1. Since longer flow lines usually exist, material handling is more expensive. 2. Production planning and control systems are more involved. 3. Total production time is usually longer. 4. Comparatively large amounts of in-process inventory result. 5. Space and capital are tied up by work in process. 6. Because of the diversity of the jobs in specialized departments, higher grades of skill are required.

Group Layout Storage Lathe Drill Grind Assembly Warehouse Mill Weld Paint Press Lathe Drill Press Assembly Grind Drill Assembly Drill Grind

Group Layout (cont.) Advantages Limitations 1. Increased machine utilization. 2. Team attitude and job enlargement tend to occur. 3. Compromise between product layout and process layout, with associated advantages. 4. Supports the use of general purpose equipment. 5. Shorter travel distances and smoother flow lines than for process layout. Limitations 1. General supervision required. 2. Higher skill levels required of employees than for product layout. 3. Compromise between product layout and process layout, with associated limitations. 4. Depends on balanced material flow through the cell; otherwise, buffers and work-in-process storage are required. 5. Lower machine utilization than for process layout.

Hybrid Layout Combination of the layouts discussed. A sample hybrid layout that has characteristics of group, process and product layout is shown in the following figure. A combination of group layout in manufacturing cells, product layout in assembly area, and process layout in the general machining and finishing section is used. TM DM BM

Flow Dominance Measure Notations: M: number of activities. Nij: number of different types of items moved between activities i and j. fijk: flow volume between i and j for item k (in moves/time period). hijk: equivalence factor for moving item k with respect to other items moved between i and j (dimensionless). wij: equivalent flow volume specified in from-to chart (in moves/time period),

Flow Dominance Measure (cont.) Flow dominance measure = f = where f is the coefficient of variation. fL and fU are lower and upper bounds on f, respectively (fL  f  fU). The upper bound fU is only guaranteed to work when each process plan includes all activities. In this case, 0  f  1.

Flow Dominance Measure (cont.) Three cases : 1. f  0  a few dominant flows exist.  product layout.  can use operations process chart as starting point for developing layout and material handling system design.  quantitative measures principal source of activity relationship. 2. f  1  many nearly equal flows exist.  any layout equally good with respect to flows .  qualitative measures principal source of activity relationship. 3. 0 << f << 1  no dominant flows exist.  difficult to develop layout.  process or product family layout .  both quantitative and qualitative measures important source of activity relationship.

Equivalent Flow Volume From-To Chart Example 1 Given three machines (activities) labeled 1, 2 & 3, Product A B C Process Plan 1 - 2 - 3 2 - 1 3 - 1 - 2 Quantities/Shift 10 5 15 Assume Product B is twice as “difficult” to move as A or C  hijB = 2 and hijA = hijC = 1 To 1 2  5 10 1  15 15 2 110 1  15 25 3 1  10 10 From 1 2 3 Equivalent Flow Volume From-To Chart  w12 = 25, w21 = 10, etc

Example 1 (cont.) M = 3 and  no dominant flows exist (likely, since 3 different process plans)

Qualitative Measures Closeness values (A, E, I, O, U, X) used to indicate physical proximity requirements between activities. Relationship Chart can only show symmetric relationships, as compared to From-to Chart (wij  wji possible). Relationship Chart is starting point for developing layout when 0 << f  1. If f  1, then don’t need to consider flow (only qualitative relationship) If f <<1, then one can convert equivalent flow volumes to closeness values so that material flow relationships can be considered along with qualitative relationship. If f  0, then can still convert to relationship chart if significant qualitative relationship exists, otherwise, just use operations process chart.

Conversion Method Machine 1 Machine 2 A Machine 3 I E To convert equivalent flow volumes to closeness values for the example problem, use wij + wji to make them symmetric. Conversion relations : 20 < wij + wji  A w12 + w21 = 25 + 15  A 12 < wij + wji  20  E w13 + w31 = 0 + 15  E 5 < wij + wji  12  I w23 + w32 = 10 + 0  I 0 < wij + wji  5  O wij + wji = 0  U A I E Machine 1 Machine 2 Machine 3