In Motion
Package printers can get the most out of brakes, clutches and motors with adjustment savvy, package deals and new technology. Industry experts offer a comprehensive cross-section of motion controls currently at work for converters.
By Susan Friedman
Edd Brooks, project manager and senior technical specialist at Horton Industrial Products, a subsidiary of Horton, Inc. in Minneapolis, MN, says pneumatic, single-position tooth clutches that allow engagement in one place are helping achieve precise ink color changes in tight register print jobs.
Brooks also reports air-controlled brakes are providing strong cost and operation benefits, while electrically-controlled components' high technology aura is garnering attention.
AC motors are proving more cost-effective, while DC motors are showing higher maintenance needs in harsh environments, asserts Jon Radde, area manager for motors related to consumer products at Chicago-based Reliance Electric. DC motors are available with special cooling capabilities that can reverse airflow direction to protect against contaminants, he adds.
Bob Burke, vice president of sales at Pacific Scientific, Rockford, IL, states that intelligent AC or DC servo motors, integrated with menu-driven, computerized press controls, are starting to replace traditional line shafts with electronic adjustment of registration or positioning between press sections. Synchronous, brushless servo motors placed between two rolls or between nip rolls provide the speed consistency of a line shaft with an increase in flexibility, he says.
Airing opinions
According to motion control brand managers, bottom line enhancements can be realized with both brake/clutch systems and motors and drives.
Radde comments, "If you are putting in an entirely different machine, electronic [motor systems] is the way to go. You can eliminate maintenance on mechanical components that wear and degrade as the machine ages."
Tom Becknell, sales manager at Mach III Clutch in Ludlow, KY, counters, "Converters respond well to pneumatic clutches and brakes because they like the price...but sensitivity has always been a problem." Becknell recomends components that provide smooth, continuous slip to avoid web breakage, especially when diecutting thin laminates.
Brooks comments that pneumatic brakes operate cooler to allow a smaller unit to do the same job as a larger electric unit. He says pneumatic brakes may last up to 6 times longer than electric brakes, which he says are typically more expensive to repair or not repairable at all, because electrical maintenance costs can approach the original price of the component.
When it comes to a more general assessment of brake/clutch and motor/drive systems for tension control or incremental motion, Matt Oliver, national sales manager for Montalvo, Portland, ME, emphasizes the simplicity of brakes, maintenance-wise, compared to the complexity of motors and drives. He acknowledges that there used to be a great cost disparity between the two systems, "but motors and drives are coming down all the time."
John Malinowski, drives specialist at Baldor Electric, Fort Smith, AR, explains increased throughput capability is motivating interest in servo motors and controls. These offer precise control of both velocity and position (with the use of a motion controller) via feedback from an encoder or resolver.
Burke adds this precision comes with a level of complexity that converters may not be prepared to maintain. Common user questions he cites include, "If there's a failure, how do I find it?" and "How long will the system be down?" Sophisticated diagnostics are available to help, he says.
As good as new
New motion control equipment isn't the only way for converters to accommodate shorter runs at varying tensions and faster press speeds—certain operating levels and adjustments can help existing equipment tow the line as well.
Ron Pelletier, product manager/ engineer at P/A Industries, Bloomfield, CT, recommends pneumatic brakes be sized, when possible, to require 40 psi to 60 psi when operating at full roll condition. Pelletier explains most brakes take 2 psi to 5 psi to engage, while some require up to 10 psi. A brake operating at 15 psi to 20 psi at full roll has a working window of 10 psi to 15 psi after the engagement pressure is subtracted. A 1 psi or 2 psi change to the brake under these conditions will yield a 10 percent to 20 percent tension change. Smoother operation is possible at 40 psi to 60 psi, where the same pressure adjustment results in only a 1.6 percent to 5 percent tension change.
For multi-caliper brakes popular for accommodating different tensions, Pelletier recommends that converters operating in the 15 psi to 20 psi range deactivate enough calipers so the brake will require 40 psi to 60 psi at full roll condition, providing similar tension results.
Pelletier advises that a brake with forced air cooling may be required for faster line speeds. A standard air-cooled brake that is squealing can be kept cooler via a fan or regulated shop air blown across the brake at 3 psi to 5psi. He also recommends seeking out good repeatability characteristics. P/A's Soft-Aire brakes can provide the same torque reading for 20 brakes at the same time using the same air pressure.
Reliance's Radde states motor suppliers can help converters handle increased press speeds by modifying equipment, supplying graphic interfaces and integrating into a press's overall computer controls. He recommends a fully enclosed motor to prevent premature failure, with thermal or explosion protection as needs dictate. Other key motor considerations he cites include sufficient cooling capability, meeting desired torque requirements and inverter duty ratings. "We are finding that motors must be rated for extreme voltage spikes of 1600 peak voltages and withstand .1 microsecond rise times," he says.
To select a suitably sized motor, Baldor's Malinowski mandates matching inertia with the required load. A motor that is too large will require too much power, he says. To simplify the process, sizing software can determine appropriate motor dimensions based on loads and other application parameters, he adds.
Wrap it up
Based on input from key sources, new motion control product offerings are somewhat eclipsed by the industry's packaged, total solutions approach.
Montalvo's Oliver says the company maintains an extensive research and development program to design packages for specific applications, rather than have customers adapt on their own. "We tailor each package so that it's virtually plug and play," he relates, by including mounting hardware with components, and working to use existing components "within the envelope" of the press to meet physical constraints. One Montalvo package includes safety chucks designed to replace the bearing in a single disc brake to allow running of lighter materials.
Mach III's Becknell emphasizes a complete package that includes tension controls. "We offer a full line so that the buck stops here, and the brake guy isn't blaming the controller guy for system problems," he says.
New motion control offerings are still coming 'round the bend at a steady pace. These products share a common thread of ease—whether in operation or in maintenance.
For brakes and clutches, suppliers continue to hone in on finer-tuned design iterations. Mach III's friction brake designs feature linear bearings to facilitate smooth operation down to the core, while Montalvo offers an anti-squeal material that can solve brake operating problems without necessitating machine parameter changes. Horton has introduced tension control brakes and clutches for winding/unwinding with tunable, precise torque-to-air pressure settings.
In motors, suppliers toil to maximize user-friendliness. Reliance's RPM AC motor offers the same footprint as a DC motor, enabling a direct replacement in line modifications.
In general, servo systems are becoming more mainstream through simpler keypad configurations and automatic tuning capability, reports Baldor's Malinowski. Baldor drive specialist R.J. DiMaggio adds that MINT, Baldor's motion intelligence programming language, can make set-up, programming and maintenance more painless with its plain English, single-word command structure. Servo controllers may also be interfaced with press computer controls.
