Adjust Quality in Real Time
技术分类:过程与先进控制 作者:Mark T. Hoske 发表时间:2005-12-05
be taken," Sevin explains, rather than individual (and generally unrepeatable) work piece measurement values.

For machine tools, closed-loop control can be achieved with "high quality, repeatable, electronic based, gaging equipment coupled with accurate machine tools featuring relatively current (early 1990s or later) CNC controls," Sevin says. Open-loop, he continues, "may stop the customer from receiving a bad part, but does little to help reign-in costs associated with the production of scra

p and rework materials. A closed-loop system, on the other hand, can not only keep bad product to a minimum, it can even generate additional savings through unexpected benefits, such as increased tool life (and decreased tooling budgets), greater machine utilization (through increased uptime and lower cycle times), and gains in worker productivity due to the elimination of manual tasks." Closing the loop could cost as little as $6,000, Sevin adds.

R. Andrew (Andy) Bedingfield, part owner of Soltus, a system integrator firm, sees many opportunities for improvements with closed-loop control, improved quality, material savings, waste reduction, and tighter coordination with enterprise systems, since closing the loop requires precise information flow. Vision systems, as they've fallen in price and increased ease of use, are widely used for closing the loop, especially among automotive manufacturers and leading suppliers.

Closed-loop control will aid the trend from continuous production lines to more cellular, customized manufacturing. The smaller the lot, Bedingfield explains, the more the bottom line depends on rapid set-up and production of on-spec product. He recommends tying in the control system earlier in the process, and slowing down line speed at beginning of a changeover to ensure a process is meeting specifications before ramping up speed. Quality measurements and closed-loop controls can drive that, Bedingfield says.

A closed-loop example of this approach includes com