For equipment upgrade, retrofit rather than replace

  • 28-Jul-2010 12:55 EDT
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For an engine machining line retrofit project, legacy PLCs were replaced with Schneider Electric Modicon Premium PLCs such as the one shown.

Automation technology and programming methods, especially motion and human-machine interfaces (MMI/HMI), have progressed dramatically during the past decade. In fact, advances are so that large manufacturing facilities operating with dated control platforms are undertaking massive projects to take advantage of this untapped potential to improve machine performance and profitability. These projects typically involve the execution of a mechanical retrofit in parallel with updates to existing control systems. The goal of these projects is to boost production, keep up with the latest technology, and improve maintainability.

One example comes from the facility of a major U.S. automaker that sought to implement a mechanical retrofit and a new controls package on its engine block machining line. Based on a turnkey migration project proposed by Schneider Electric, tasks involved a broad range of control applications in a traditional transfer line with rough-in and finished machining lines, assembly functions, and some fairly complex materials handling. Despite the time-consuming tasks at hand, the business case for updating the line was simple: Retooling a line that had been in use for a decade was clearly a better option than installing a completely new line, offering faster time to market and a less capital-intensive approach to meeting demands for today’s more efficient, higher-performance engines.

As with any substantial project, there was good news and bad news. The good news was that metal cutting could be controlled to tighter tolerances and application software would make the machinery more reliable. The bad news was that every line of code would potentially need to be reviewed. To minimize the learning curve for plant personnel, the new HMI screens needed to have a look and feel similar to those that line operators were familiar with.

Using a configuration and revision management system, Schneider Electric worked closely with the automaker, which was scheduling the mechanical retrofits with its equipment manufacturers. This allowed mechanical retrofit activity to align closely with the controls upgrade activity. The process required a concentrated effort by an experienced, interdisciplinary team using sophisticated software-conversion utilities and a step-by-step methodology. The migration consisted of 110 programmable logic controllers (PLCs), approximately 175 Schneider Electric single-axis motion cards, plus HMI hardware and software.

Tasks included:

• Conversion of different motion cards from early-generation PLCs to newer PLCs, requiring validation of the sequencing logic and motion software

• Translation of HMI applications from third-party models to updated hardware while maintaining nearly an identical look and feel for operators

• Validation of the HMI applications against the upgraded applications

• Coordination with the customer, including the software development environment

• Review of electrical drawings and retrofit instructions, and management of project execution

• Changes to electrical drawings, implementation of changes to machine controls, and delivery of revised electrical drawings to the customer

• Changing out of electrical components in control panels.

Efficiency improvements were achieved through advanced control software capabilities that were not available in the legacy equipment. Cycle times were improved by performing in parallel what used to be sequential, end-to-end operations. The automaker’s investment was partly justified by the expectation that the motion modules would more tightly control each machining axis. Servo tuning, coupled with more robust machine application software, delivered the desired performance, along with increased reliability.

Shaving seconds off cycle times in a high-volume, high-value product manufacturing process increases revenue for a company. Identifying these time savers requires not only controls expertise but also an intimate understanding of the machining process as well as reliable data acquisition.

The design team took advantage of the increased capabilities of Schneider Electric’s new motion controller and was able to incorporate design changes while still retaining the original application motion profiles. Unavailable in the previous-generation product, these motion controller performance improvements included the addition of contacts to the high-pressure coolant (HPC) solenoid logic to start coolant at station cycle start, saving 1.5 to 2 s/cycle for stations with HPC tooling.

Machine stoppage recovery procedures were streamlined by standardizing the emergency-return logic for single, dual, and coupled dual-axis configurations. Individual machine cycle times were reviewed and requalified. Motion profiles were compared for equivalent opposing stations, and where differences were found they were altered to the higher of the two feed rates—in one case saving 1.3 s/cycle.

A generation and a half removed from the outdated counterparts they replaced, the new PLCs were faster and more powerful than their predecessors. As a result, the new Schneider Electric programming software was used and ran on the latest PC operating system.

Disciplined project management, aided by properly applied software tools, proved key to the project’s overall success. This mechanical retrofit is just one example of how retrofitting affords aging facilities the opportunity to keep their processes operating at peak efficiency without the need for major investments in new equipment, programming, and staff retraining.

Tom O’Hara, Manager, Engineering Services, Schneider Electric North American Operating Division, wrote this article for Automotive Engineering.

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