Chapter 5

1. Chapter 5 Flow Analysis Techniques

2. Objectives • After reading the chapter and reviewing the materials presented the students will be able to: • Understand the importance of material flow and flow analysis. • Be able to identify various flow analysis tools.

3. Introduction • Flow analysis considers the path that every part takes through the plant and tries to minimize: 1. distance travelled (measured in feet) 2. backtracking 3. cross traffic and 4. cost of production. • Flow analysis will assist the manufacturing facilities designer in the selection of the most effective arrangement of machines, facilities, workstations and departments. • When designing the flow pattern, keep in mind that the employee walking time is a nonproductive time.

4. Fabrication of Individual Parts • To establish the best arrangement of equipment, facilities designers use four techniques: • 1. String Diagram: In a string diagram, circles represent the equipment and the lines between circles indicate flow (fig 5-3, page 140). If the flow is backwards, the flow line is drawn under the circles. If there are many lines between two circles, the circles must be kept close to each other. • 2. Multicolumn Process Chart: shows the flow of each part right next to but separate from each other (fig 5-5, page 142). • 3. From-To Chart: Designers can develop an efficiency that considers the importance of the parts (fig 5-9, page 145). Up until now, we have considered each part as equal in importance. Minimizing the total cost of production is the ultimate goal of flow analysis. • 4. Process Chart: The process chart is used for just one part (fig 5-12, page 148). Symbols are used to describe what happens (page 146). Process charting lends itself to standard forms.

5. Step-by-Step Description for the Process Chart • The step-by-step procedure accompanies fig 5-12, page 148: • 1. Present Method or Proposed Method: A good practice is to record the present method so that the proposed improved method can be compared. • 2. Date_Page_of_: Always date your work. Page numbers are important on big jobs. • 3. Part Description: Everything else would be useless if you did not record the part number. The part description also includes the name and specification of the part. • 4. Operation Description: Limits of the study. • 5. Summary: For the proposed solution. Cost reduction information. • 6. Analysis: Why, what, where, when, how, and who – if you do not have a good reason for a step, you can eliminate it and save 100% of the cost. Combine steps to spread the cost. Improve flow to save on travel. • 7. Flow Diagram Attached (Important): Process charting is used in conjunction with flow diagramming. • 8. Details of Process: One chart can be used for 42 steps (front and back). Each step is independent and stands alone. • 9. Method: How the material was transported – fork truck, by hand – how material is stored can also be placed here. • 10. Symbols: The analyst should shade the proper symbol to indicate what this step is. • 11. Distance in feet: Used with transportation symbol. Sum of this column is distance travelled. • 12. Quantity: Operation – how many pieces per hour were produced. Transportation – how many pieces were moved at a time, etc. • 13. Time in hours per unit: This step is for labor cost. Cost of storage and delay will be counted in inventory carrying cost. This column is for operations, transportation, and inspection. • 14. Cost per Unit: Hours per unit multiplied by the labor rate per hour equals cost per unit. The cost per unit is the backbone of the processing chart. • 15. Time/Cost Calculations: This space is to record the formulas developed to determine costs.

6. Flow Diagrams • Flow diagrams show the path traveled by each part from receiving to stores to fabrication of each part to subassembly to final assembly to pack out to warehousing to shipping. • These paths are drawn on a layout of the plant (fig 5-13, 5-14 pages 152, 153). • The flow diagram will point out problems with such factors as cross traffic, backtracking, and distance travelled. • Cross Traffic: is where flow lines cross. Cross traffic is undesirable because of congestion and safety considerations. • Backtracking: Backtracking costs 3 times as much as flowing correctly. • Distance Traveled: The less distance traveled the better. The sequence of steps should be changed to meet the layout if possible because that requires only a paperwork change. Moving equipment may be necessary.

7. Step by Step Procedure for Developing a Flow Diagram • 1. The flow diagram starts with an existing or proposed scaled layout. • 2. From the route sheet, each step in the fabrication of each part is plotted and connected with a line, and color codes or other methods of distinguishing between parts are used. • 3. At the assembly line, all flow lines join together and travel to pack out, warehouse, and shipping. A well thought out flow diagram will be the best technique for developing a plant layout. • Using several plastic overlays will simplify the analysis • The industrial engineer can always find ways to improve the flow of material.

8. The Operations Chart • The operations chart (fig 5-15, 5-16, page 156) has a circle for each operation required to fabricate each part, to assemble each part to the final assembly, and to pack out the finished product. • On one piece of paper, every product operation, every job, and every part are included. • Operations charts show the introduction of raw materials at the top of the page. • A vertical line connects circles (steps in the fabrication of the raw material into finished products). • The operations chart is different for every product, so a standard form is not practical.

9. Step by Step Procedure for Preparing an Operations Chart • 1. Identify the parts that are going to be manufactured and those that are going to be purchased complete. • 2. Determine the operations required to fabricate each part and the sequence of these operations. • 3. Determine the sequence of assembly for both buyout and fabricated parts. • 4. Find the base part. This is the first part that starts the assembly process. Put that part name on a horizontal line in the upper right of the chart. On a vertical line extending down from the right side of the horizontal line, place a circle for each operation. Beginning with the first operation, list all operations down to the last operation. • 5. Place the second part to the left of the first part and the third part to the left of the second part and so on. All the fabrication steps are listed below the parts with a circle representing each operation. • 6. Draw a horizontal line from the bottom of the last operation of the second part to the first part just below its final fabrication operation and just above the first assembly operation (fig 5-17, page 158). Repeat for parts three, four and so on. • 7. Introduce all buyout parts on horizontal lines above assembly operation circles where they are placed on the assembly. • 8. Put time standards, operation numbers, and operation descriptions next to and in the circle as explained earlier (fig 5-15, page 156). • 9. Sum the total hours per unit and place these total hours at the bottom right under the last assembly or pack out operation.

10. Flow Process Chart • The flow process chart combines the operations chart with the process chart. • The operations chart uses only one symbol – the circle or operations symbol. • The flow process chart uses all 5 process chart symbols (fig 5-18, page 158). • The flow process chart is the most complete of all techniques.

11. Step by Step Procedure for Preparing a Flow Process Chart • 1. Start with the operations chart. • 2. Complete the process chart for each part. • 3. Combine the operations chart and the process chart, working in all the buyouts.

12. Computer Aided Flow Design and Analysis • Computers and software packages can aid in the design and analysis of material flow in the manufacturing facility. • FactoryFLOW is a powerful layout analysis tool capable of integrating the actual facilities drawings with the material flow paths and the production and material handling data. • Facility planners have to obtain the input data such as time standards, route sheets, and process and equipment requirements. • Factory CAD can be used to prepare a sketch of the facilities showing existing or proposed location of various activity centers. • Critical paths, bottlenecks, and flow efficiency can be readily determined. • Optimal dock, storage, and equipment locations can be quickly and easily determined (fig 5-20, 5-21, page 163).

13. Summary • Flow analysis considers the path that every part takes through the plant and tries to minimize: 1. distance travelled (measured in feet) 2. backtracking 3. cross traffic and 4. cost of production. • To establish the best arrangement of equipment, facilities designers use four techniques: 1. String Diagram 2. Multicolumn Process Chart 3. From-To Chart and 4. Process Chart. • String Diagram: In a string diagram, circles represent the equipment and the lines between circles indicate flow. • Multicolumn Process Chart: shows the flow of each part right next to but separate from each other. • From-To Chart: Designers can develop an efficiency that considers the importance of the parts. • Process charting lends itself to standard forms. • Flow diagrams show the path traveled by each part from receiving to stores to fabrication of each part to subassembly to final assembly to pack out to warehousing to shipping. • The flow process chart combines the operations chart with the process chart. • Computers and software packages can aid in the design and analysis of material flow in the manufacturing facility. • FactoryFLOW is a powerful layout analysis tool capable of integrating the actual facilities drawings with the material flow paths and the production and material handling data. • Factory CAD can be used to prepare a sketch of the facilities showing existing or proposed location of various activity centers.

14. Home Work • What does flow analysis try to do? • What do flow diagrams do? • What is Factory FLOW?