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www.us-tech.com
Moving from Quality Assurance to Quality Control Continued from page 54
each process action is recorded for each production item. We often will want to restrict
the number of test and repair loops a product may take. This requirement is common in automotive and mili- tary manufacturing where the num- ber of solder reworks allowed is fixed. We might also want to ensure that products are not locked in an endless cycle of test failure and ineffective repair without some alert being raised, ensuring this cycle is broken.
Skills verification At each of the operations, work-
ers with the skill level defined in the plan will be required. This must be managed by automated confirmation that the operator at each station is approved for the product task and associated operation. When product is routed to an operations point, the associated skills required for that product must be verified. By ensuring the plan contains
the skills level and an operator skills table is maintained identifying each operator who then must log onto each operation with a unique ID and pass- word, we can positively ensure that the skills required to process the product are available at that opera- tions point. A simple interlock will prevent work progressing through an operations point that does not have the required skills.
True “Quality Control” Manufacturing Execution sys-
tems like the one from Mentor’s Valor Division now offer the “Con - trol” we need to move from Quality
Assurance to Quality Control. For sure we will need to continue with traditional assurance steps like 100 percent inspection and extensive test regimens as these are our measure of the effectiveness of our Quality Control. But MES systems open up the
exciting prospect of reducing our costly quality assurance steps as we eliminate defects caused by poor con- trol of the manufacturing processes. By combining a reduction in QA steps with the MES solution’s ability to capture and report on all key man- ufacturing variables, we receive the data we need to intelligently scale our “assurance” steps where we are not able to resolve issues with “Control” alone. MES solutions containing
Valor’s Quality Management module can also provide continuous monitor- ing in real time that can alert the manufacturing team when out-of- control limit defect levels are exceed- ed, such as a test yield that falls below target, a DPMO (Defects Per Million Opportunity — as defined by IPC), or a repeat of defects on the same product or component. Within the Valor solution, the
trigger level for repeat defects, known in the quality world as “sys- temic defect”, can be set to alarm on these systemic defects. Or, more sophisticatedly, having programma- ble incident rates such as the same defect 3 times in 10 for example.
Making Alarms Effective Connectivity to the shop floor
also opens up the possibility of mak- ing quality alarms effective in con-
trolling our shop floor. This is in con- trast to the simple level of assurance an SPC (Statistical Process Control) chart can offer; as each chart is maintained at a single process con- trol point and any corrective actions recorded at that point. The connectivity offered by MES solutions to all process points can be used in two advanced ways. First, the knowledge of
out-of-tolerance conditions and the associated corrective action can be captured and analyzed to prevent future occurrences; analysis of the data from manufacturing can also be used to optimize future manufacturing projects. Secondly, the alarm can
be delivered to the engineer- ing and operations team in real time, hence the process corrective action can be com- pleted at the original source of the defect before there is the opportunity to repeat that defect.
The Valor MSS Quality Management module provides clear repair instruc- tions when failures are detected, and logs all failure drag for tracking and monitoring.
The Valor Quality Management
solution allows the alarms once trig- gered to be delivered to shop floor quality clients for corrective action at that operation, bringing to reality the adage “it is better to avoid a defect than just count them”. Does this mean the demise of
Quality Assurance? Of course not! At least, not until we remove the most influential variable in our manufac- turing process — the “Human”. Even then, we will want to have some form of inspection and test to minimize the risk of product failure, or safety,
defects. The route is clear: reducing our non-productive activity by replac- ing Quality Assurance with MES delivered Quality Control. This is designed to prevent defects and take corrective actions directly at the shop floor operations. This, then, enables “Lean Manufacturing” —reducing our total cost of manufacturing, reducing scrap and wasted effort. Contact: Mentor Graphics
Corp., 8005 SW Boeckman Rd., Wilsonville, OR 97070-7777 % 503-685-7000 fax: 503-685-7704 Web:
www.mentor.com r
April, 2012
or poor customer perception. But we can take giant strides
towards minimizing the need for cost- ly added operations that assure us that we have not injected random
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