Can you follow instructions?: Inspection Efficiency
Do you process existing jobs the same way every time? If not, you may be throwing money away every time those jobs are run by having to reinvent the process over and over.
Do you process existing jobs the same way every time?
If not, you may be throwing money away every time those jobs are run by having to reinvent the process over and over. If a few weeks or months go by in between runs of the same part, you may forget some nuance, whether it’s a specific cutter, a dedicated fixture or a unique method for locating the part.
For new jobs, do you plan how to process them? When quoting jobs, is the process engineer involved? If you don’t have a process engineer, whoever quotes a job should be involved during initial part setup and production. It’s also important to meet with the person who does quoting and agree on the processes used to machine and inspect each part. I call them “work instructions for the machining process” and “quality plans for the frequency of inspection and the characteristics that need to be inspected.”
The work instructions should include:
■ The bill of operations, or routing;
■ The bill of materials;
■ Images of the setup(s), special tools and fixturing arrangements;
■ Tooling and fixturing documentation; and
■ Anything that helps set up and run the job efficiently and with high repeatability.
Routing is basically an overview of the process. This includes the processing sequence, the machine(s) to use and any outside processes. You can also include setup time and cycle time. The operators then sign off on the steps completed.
The bill of materials tells what materials are needed, including size and grade. This helps ensure consistent materials and eliminates surprises in characteristics such as hardness and machinability. If a different material size is being allotted, perhaps because of availability, this should be indicated.
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RELIABILITY. PRICE. REPUTATION. Haas UMC-750SS Super Speed, 5-Axis Universal Machining Center = TOTAL CUSTOMER VALUE. WE KNOW what it’s like. That’s why we’re driven to make sure that every Haas We’re MACHINISTS, too. CNC machine is trustworthy, affordable, and always We CUT METAL every day. backed by the industry’s best after-sale service. Haas Automation Inc. | 800-331-6746 | www.HaasCNC.com Proud sponsor of the Stewart-Haas #41 car
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Haas UMC-750SS Super Speed, 5-Axis Universal Machining Center = TOTAL CUSTOMER VALUE. WE KNOW what it’s like. That’s why we’re driven to make sure that every Haas We’re MACHINISTS, too. CNC machine is trustworthy, affordable, and always We CUT METAL every day. backed by the industry’s best after-sale service. Proud sponsor of the Stewart-Haas #41 car.
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January 2015
It’s helpful to include setup photos or drawings in the work instructions. If a job requires special tools, include drawings or images of them in the work instructions, along with part numbers and manufacturer information. An image of an operator locating the part in the fixture is also beneficial.
Tablet computers are relatively inexpensive, so consider having one at every machine to store and access tooling and fixturing data. While a picture is worth a thousand words, a video with narration can be priceless to a machinist when it shows, step-by-step, how a raw part is loaded, located and clamped. In addition, the video can show the what, where and when of part inspection, as well as the inspection equipment needed.
The work instructions can also include part programs and a tooling list. Give it some thought and I’m certain you’ll come up with additional instruction items.
When it comes to part verification, the quality plan indicates the frequency of inspection and the characteristics to be inspected. After inspecting the first piece 100 percent, maybe you only need to inspect one in five or one in 10 pieces. Maybe there are only certain dimensions that need to be inspected 100 percent. The plan should also tell the method or device to use for inspecting a characteristic. For example, is a standard OD micrometer or caliper sufficient, or should you use a special gage? The sample size for that characteristic should also be stated.
Once you find what you need or want in your work instructions and quality plan, apply them to older jobs as they repeat. You might be surprised at how much time—and money—you’ll save. CTE
About the Author
Manufacturing engineer/project manager and a regular CTE contributor. Email: mderen1@wi.rr.com
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