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| UNIT F. PROCESS ORGANIZATION AND PRODUCTION PLANNING |
| COMPETENCY: 011.00: Assess and apply problem solving methods to the solution of technological problems. |
| OBJECTIVE: 011.02 : Plan the sequence of operations needed to fabricate and assemble a product. |
After completing the Bill of Materials, the next step is to list the sequence of operations needed to fabricate each part. To do this, you must understand processes that can be performed on available tools and machines. So, in preparation review designs and analyze the cutting, forming and combining operations that will be needed. Decide which tools or machines would be best for each operation. Discuss possible operations and equipment with your teacher and classmates. Once you understand the "problem environment" you are ready to identify and sequence operations.
| Writing Operations |
An operation step must identify the process, size, part and tool. The process can usually be stated as one material processing term (i.e., crosscut, rip, turn, bore, mill, etc.). Yes, you need to know your terminology-- the language of material processing. The terms of material processing relate tools to materials to operations. So, one word can mean a lot! For example, the term "crosscut" describes an operation for cutting wood to length using either a hand saw or table saw.
The part name and size give workers the information needed to layout and process material. The size specification is written as a measurement specified in the Bill of Materials or working drawing. The tool identified for the operation is chosen because is the best to perform the operation accurately and safely.
When these components are put together you have an operation step. To illustrate, an operation may be constructed as follows:
This operation step is stated efficiently while providing the necessary information.
Sometime forms are used to construct an operation chart. When using a form, the rules of writing remain the same. Look at the computer form below.
In this example, input screens are provided for each part. Material process techniques and tools or work stations are specified.
An important part of writing operations is to sequence them in proper order. Sometimes the sequence is just common sense-- you're not going to apply finish before the part is cut. Sometimes the proper sequence ensures accuracy-- rip before crosscutting when squaring a board. Sometimes the sequence of operations can go either way. If this is the case, consistency across parts is important. For example, if one part is drilled then filed to shape, use the same sequence for another part that requires the same operations. Consistent sequencing will make material flow planning easier and will lead to a more efficient system.
Generally, material processing usually goes like this:
1. Rough cut stock material
2. Cut or form material to size
3. Make special cuts and bores
4. Prepare for assembly-- sand, file, etc.
5. Assemble parts that are permanently assembled (adhesion/cohesion)
6. Apply finish
7. Assemble parts that are mechanically fastened (hinges, screws, bolts)
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Print a |
| Operation Process |
The operations listed is Step 2 show the sequence to produce each part. The operation process chart is constructed to group equal process and show the sequence of operations for the system. Grouping equal operations has several advantages:
1. Grouping reduces the total operations and workstations needed to produce the product. If a product has three parts requiring 8, 11 and 9 operations, the system would require a minimum of 28 workstations and employees. By combining equal operations, several parts can be processed at the same workstation reducing the number of steps, workstations and employees. Grouping saves time and money.
2. Grouping increases quality by reducing the chance for error. When there are fewer steps, there is less chance for error. Also, combining equal operations across parts insures good fits when assembled. For instance, if two parts are designed to be assembled across their width and one part is 1/64" under and the other 1/64" over, there will be a 1/16" mismatch when assembled. By cutting the parts at the same workstation with the same setup they will match to close tolerance when assembled.
Below is an example of an operation process chart. The operation process (P1, P2, P3 and P4) show operations to be performed in proper sequence. The parts, referenced by the part code at the top of the column, to be processed follow the operation sequence stated in the left column. The workstation is listed in the right column. So, in this example, the first process (P1) is rough cut parts 001 and 002 to 48" at the radial arm saw.
As you can see, this chart provides the essential information for fabrication: process, dimension, part and tool. Equal processes are combined and the total number of operations are less than making each part separately. If you are writing your operations rather than using a chart, follow the suggestions in Step 2 and simply add the other part to be processed at a workstation.
The steps that follow are based on the planning done to this point so it is important to analyze and evaluate the operation process chart. Are processes grouped and sequenced as efficient as possible? Looking ahead, material flow, line balance, plant layout and system economics are improved by making good decision at this point.
What to look for:
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Print a |
| Standard (ASME) symbols to represent typical activities; record sequence of flow for worker, material or machines (one at a time) | |
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Steps in a process of modifying a material, part or product |
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For quality (test) or quantity (count); doesn't change shape or move product |
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Movement of workers, material or equipment from one operation to another; not if movement is part of an operation |
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Temporary delay: work waiting between operations |
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Controlled, authorization needed to put/retrieve part into storage |
To develop an operation list, you need to:
To optimize the fabrication process, you need to:
When your operation lists are complete, you know:
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