By Rich Merritt, Senior Technical Editor
THE PERFECT MACHINE requires no maintenance, no repairs, and no aftermarket service of any kind. Once it goes out the door, you forget about it. Because that’s not possible with any machine more complex than a bench vise, the next best thing is a machine that requires the absolute minimum of changeover effort, maintenance, repairs and service. How do you build such a machine? We asked machine builders and automation suppliers what they do towards that goal, and got some interesting answers. Basically, they say to keep it simple, monitor it, and fix it before it breaks.
Kiss Your Troubles Away
Mechanical devices cause most of the problems in most machines. Traditional motors, gearboxes, line shafts, belts and chains require endless adjustments and maintenance, and are prone to failure after prolonged use. Parts changeovers often are tedious and time consuming for your customers. The better solution would be to look for a way to keep it simple, stupid (KISS).
R. A. Jones & Co. in Covington, Ky., has made packaging machines for 100 years, and they’ve kept up with technology all the way. “Manufacturers that use carton machines are in an extremely competitive mode,” says Darren Elliott, chief engineer at R.A. Jones. “They need to run products faster and more efficiently.” In 2000, R.A. Jones began implementing what is known in the industry as Generation 3 (Gen3) machines, using Rockwell Automation’s Kinetix motion control system, servo drives, a digital SERCOS network, and MP-Series motors and actuators.
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FIGURE 1: DRIVE, HE SAID |
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R.A. Jones has been building cartoner packaging machines for 100 years. In its new cartoner machines, the company changed over to servo drives to reduce the number of mechanical components and increase reliability.
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Its new Criterion 2000 cartoner machines
(See Figure 1) now rely less on mechanical components and more on digital, all-servo-driven technologies. By using servos, R.A. Jones reduced its engineering costs and built a flexible, high-reliability cartoner that compresses installation time and reduces maintenance by eliminating belts, drive chains, line shafts, pulleys, sprockets and torque tubes.
Tom Matyas, product manager for drives, motors and motion at
AutomationDirect, says lineshafts work well, but require too much service. “Due to their mechanical nature they rely a great deal on correct machine setup, such as synchronization and mechanical connections, plus proper maintenance,” he says. “This usually means longer setup between cycles on machines that run several different products. Improper setup and/or mechanical wear at a single station may have a ripple effect on any station connected, thereby affecting the efficiency and performance of the entire system.”
Servos, direct-drive technology, linear drives and variable-speed motors all seem to be K-I-S-S solutions for machine builders.
“Converting rotary motion into linear motion requires, at minimum, a rotary motor, gearbox, two pulleys, a belt, couplings, a ballscrew and zero-backlash nut, and linear bearings and races,” explains Matyas.
“A linear motor makes the same movement as the rotary solution without the additional mechanical components, thereby greatly reducing the chance of system failure.” Obviously, the more moving parts, the more wear and higher the maintenance.
“The move to servos and integrated control technology has the potential to replace up to 60% of the mechanical parts in a machine,” explains Mike Wagner, business development team leader, Global OEM Team,
Rockwell Automation.
“The benefits of this reduction include lower costs, increased reliability and maintainability, as well as improving machine performance by up to 75%. For example, in the past it took several hours to change over a machine to run a new part, and the machine could only run a few product variations. Today, servo-driven machines complete changeovers in less than two hours, and now you can run hundreds of product variations on a single machine.”
Servos make a key difference. “I use servos as much as possible,” says Archie Jacobs, engineer at Manufacturing Automation LLC, a system integrator in Orangeburg, S.C. “I mostly use them for flexibility and feedback, such as for current load. It also eliminates contactor replacement due to arcing when full voltage starting. The acceleration and deceleration reduces mechanical system shock at startup extending the life of mechanical components.”
Tom England, marketing manager of the direct-drive motors business unit at
Danaher Motion, says direct-drive technology also simplifies operations. “Machine control using direct-drive technology provides significant improvements in machine uptime due to the elimination of the mechanical transmissions, gearboxes, and timing belts,” he says. “Machine simplification also is greatly enhanced by the elimination of all the components needed, such as brackets, mounting parts, and tensioning components. Most high-speed pick-and-place machines employ direct-drive technology today due to the speed performance and reliability improvements.”
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