AIA: Leadscrew Motion Improves Case Packer
"So much of our business is driven by speed," says Peter Ratcliffe, president of custom modular linear motion system manufacturer RPT Motion (Quebec). "Our customers have always looked to us for ways to speed automation, but in light of the recent globalization, we have observed an intense pressure to provide solutions that reduce downtime, and thus, increase overall productivity."
As if this wasn't enough, a key segment of RPT's business involves updating existing subsystems on machinery to increase production rates and reliability-a line of work in which size plays a critical role. Specifically, customers want an increase in speed without having to change an existing machine's basic dimensions, for the obvious reason that this kind of redesign and rework costs money.
Recently, RPT Motion teamed up with Kerk Motion Products Inc. (Hollis, NH) to help a customer add a second case packer to an existing manufacturing line. Although, the problem was a simple one in conception, the solution required more than just dropping in a new case packer. This was because the existing system used a pneumatic, two-position lane changer that couldn't accommodate an additional two positions or the higher speeds the customer required. Specifically, the use of four lanes required a system stroke length of more than 40 inches, with the lane changer indexing every 10 seconds or less to maximize the time available for product flow.
Together, RPT and Kerk installed a VHD series leadscrew and nut in an RPT modular slide, creating a smooth-running, high-speed, servo-powered system, with anti-backlash performance. To meet the customer's speed requirements, RPT chose a model with a 0.75-inch screw diameter and 2.4 inches of travel per revolution. According to Ratcliffe, the compact size of the VHD leadscrew and nut were instrumental in making the new system a success. He says the system's anti-backlash properties and the fact that it is self-lubricating have allowed the system to continue functioning at peak efficiency long after other systems might have given out.
"The physical size of the Kerk VHD lead-screw and nut package was...much smaller than available ballscrews of similar leads," Ratcliffe says. "The lane changer functioned without failure or even noticeable backlash for three years, which is typically unheard of in most linear motion applications.... Any wear that does eventually occur in the screw or nut is compensated by the Kerk mechanism, which adjusts automatically to maintain a zero backlash over a very long service life."
Since this first application, RPT has incorporated Kerk leadscrews in a number of other applications, including an ink-jet printer movement system and a gantry robot packaging system. "The Kerk VHD system has become the first choice of RPT Motion when addressing linear motion systems," Ratcliffe says.
For more on leadscrews and motion control, call 603-465-7227, visit www.kerkmotion.com or eInquiry 5.