Tech Directions - October 2007 - (Page 18)

Table 1—Sequenced List of Identified Processes Seat 1. Plane stock to thickness 2. Lay out seat circumference 3. Saw rough circumference 4. Smooth seat edge 5. Round seat edge 6. Sand smooth 7. Stain 8. Apply finish 9. Dry 10. Store Legs (4 required) 1. Mark lengths of legs 2. Cut out legs 3. Form tapers 4. Drill two holes 5. Sand smooth 6. Stain 7. Apply finish 8. Dry 9. Store Supports (4 required) 1. Mark lengths of support 2. Cut out supports 3. Sand smooth 4. Stain 5. Apply finish 6. Dry 7. Store cessful completion of this step often requires a good knowledge of manufacturing processes and lab processing equipment, so students unfamiliar with lab processes and machines should consult their instructor. Students then sequence listed tasks in the order in which they will be performed. Again, successful completion of this step will require a good knowledge of manufacturing and lab processing equipment, and consultation with the instructor may be necessary. The numbers associated with the list (sometimes called task numbers) indicate the process sequence. Sometimes a part can have a flexible sequence of operations. For example, in Table 1, which shows a sequenced list for stool construction, operations 2 (cut stock to length) and 4 (drill two holes) could be reversed for the legs. When such a situation arises, the process planner should employ the sequence that will yield greater benefit to the person, company, or customer involved. ● Assign time data, equipment, and tooling to the sequenced processes. To complete the planning, the scope of this discussion. Consequently, the assigned time for each process in the lab can be an estimate. Inform students that while this works in an educational setting, in industrial applications, published standard time data, time study results, and experts’ opinions all come into play. Note that the estimated time should include time taken to retrieve tools, set up equipment, and perform other necessary unspeci- arrives in the plant until it joins the other parts” (p. 146). A process chart usually includes standard operation symbols and other elements for use by the process planner. Table 3 shows what a more comprehensive and detailed process plan for the seat would look like when performed with a process chart. Operations like basic inspection and setup of needed machines are sequentially included to show when each process takes place. The process chart also identifies beginning and ending operations, key personnel involved in fabricating the part, the date the chart was completed, and total number of each type of process used. In advanced manufacturing, the process chart can be automated, which helps to simplify the task of putting it together and updating it when future orders for parts with similar features are received (Rehg & Kraebber, 2005). In Table 4, an operations (or assembly) chart shows the assembly Table 2—Process Plan for Seat Task Time Machine Tooling Goggles Ruler/dividers Eye goggles Skew Skew Sandpaper Brush Spray can NA 1. Plane stock to thickness 5 Planer 2. Layout seat circumference 7 NA 3. Saw rough circumference 12 Band saw 4. Smooth seat edges 20 Wood lathe 5. Round seat edge 10 Wood lathe 6. Sand smooth 5 Wood lathe 7. Stain 5 NA 8. Finish 5 NA 9. Dry 15 Blower 10. Store 60 Total time 144 minutes fied tasks. Students should calculate total time for each part. students must assign the machines and tooling needed to process each part, as well as the time in minutes that it takes to complete each task. See Table 2 for an illustration. Completed process plans for the legs and supports are not included here, but they can be good classroom or lab exercises for students. Determining exactly how much time a process takes to complete (also called standard time) is beyond The Process Chart Discussion so far has centered on basic process planning. For detailed process planning, however, the process chart is very useful for documenting all details needeed for safe and efficient fabrication. According to Meyers and Stephens (2005), “The process chart is used for just one part, recording everything that happens to that part from the time it of the stool’s various parts. This chart helps manufacturing personnel, such as assemblers, visualize the proper sequence of operations. In advanced manufacturing (which is beyond the scope of this article), the chart would include processing time elements for each step and the total number of minutes required to assemble the entire product. Factors Influencing Process Selection Process selection is influenced by 18 techdirections ◆ OCTOBER 2007

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Tech Directions - October 2007 Technically Speaking Contents Direct from Washington The News Report Technology Today Technology’s Past Mastering Computers Rock Your Classroom!—Use Subwoofers to Teach Electricity and Science Sure, They Can Build It, But. . . . Manufacturing Students Need Process Planning Skills Teach Graphic Design Basics with PowerPoint Free Teacher Resources Product Central More than Fun

Tech Directions - October 2007

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