Servos Invade Packaging Arena

Lower cost, improved performance result in more design wins

Randy Frank – Design News

Not long ago the cost of servos was prohibitive in many packaging applications. Today, with the need for higher accuracy, improved speed regulation, and flexibility for periodic profile changes, these motion control technologies can frequently be found in packaging systems.

“What’s happened is that the cost of the electronics has come down so much that even open loop steppers are being replaced with closed loop servos,” notes Lee Stephens, systems engineer for Danaher Motion. Equally important, implementing servo control is easier than just a few years ago. This can be quite important in the packaging industry.

“The more customers want to automate, the more it is driving them towards servos,” says John Mazurkiewicz, application engineer for Baldor Electric Co. Increased accuracy and speed resulting in more output per hour are among the more compelling reasons to spend the money. Improved quality with lower rejects can complete the justification for making the move to servos. Today, the initial cost impact is less than it was just 5 years ago, but the productivity improvements from automation are much greater.

However, at least one company has changed from using servos back to stepper motors based on the servo being overkill for the application. In this case, the application did not require the torque or the speed of the servo and in a highly competitive market, the stepper provided a cost advantage. Also, with improvements in stepper motors that provide even better accuracy, the use of steppers may be the right decision. Size 34 and size 23 steppers appear to be the most common for users interested in making this switch according to Ryan Lin, director of sales and marketing at Lin Engineering.

According to Steve Lipps, Product Line Manager—Horizontal Wrappers, Bosch Doboy, servo technology has resulted in shorter development time because fewer mechanical links are required between modules and fewer mechanical parts allow the design to be split among more designers. The result is lower cost mechanics. Among the changes that have occurred is the design of these machines from the ground up for servo control to minimize costs and increase performance.

Here are five applications of motion control technology in the packaging industry.

Bosch Doboy Linium 301

Bosch Doboy designd robotic packaging, cartoning, horizontal flow wrappers, and bag closing and baggers equipment. The company has made an extensive transition from mechanical systems to servos. Its Linium 301 horizontal flow wrapper provides one such example, with servos driving the infeed, finwheels, and cutting head. “A mechanical system would have a torque limiter that would kick out if the rotating sealing jaw hit a product to be packaged,” notes Steve Lipps, “It would stop the machine and require resetting.” In the design when the servo drive system senses a positioning error caused by hitting a product, the PC controller reverses the direction of the drive. This allows the misplaced product to pass through, and then starts again, all without stopping the flow of incoming products.

Triangle Packaging Machinery Advantage

Triangle’s packaging equipment includes cartoning machines, filling machines, form, fill and, seal machines, and packaging support with specialty equipment. Triangle’s Advantage continuous motion vertical form-fill-seal (VFFS) machine uses servo controls provided by Allen-Bradley ControlLogix or Selectech iPC. However, they have direct digital dual stepper motor belt drives. “We originated with stepper motors for our back machines and we have progressed into servo motors to draw the film and to drive the jaws,” says Ted Torrens, vice president of sales and marketing for Triangle. Customer requirements and impetus from the supplier of the motor controls has been one of the driving factors for Triangle. Torrens also attributes greatly improved diagnostics and reliability to today’s servo driven systems. “All of our cartoners are being converted over to servo motor, which offers more torque,” notes Torrens.

Supreme Plastics Reseal 460X Zipper Applicator

Supreme Plastics’ zipper applicator for continuous motion form-fill-seal machinery boasts faster operation and increased precision from servo control. The units have independently servo-controlled, zipper-feed channels for high-speed application to moving film and quad-axis servo control. The dual-forcer motor attaches zippers to a continuous plastic web at 120 pouches per min. Baldor NextMove BX motion controller and four FlexDrive servo drives control the machine’s four axes of motion. The control comes from two rotary servomotors and two forcers for the linear stage. According to Baldor’s John Mazurkiewicz, his company is seeing greater use of servos for packaging applications. Programmable positioners with easier means of programming make the decision to go servo easier for users.

FKI Logistex Robotic Arm and Gantry System

FKI Logistex provides palletizing and depalletizing systems that can include articulated robotic arms, gantry robots, and unscramblers for packaging. The company uses multiple-axis, servo-driven systems to handle a wide variety of products. Robotic palletizers and depalletizers use 4, 5, or 6-axis jointed arm robots to provide the required accuracy and flexibility.

Lantech SW-3000 Shrink Wrap

Lantech has a different approach to motion control. Its packaging products include semiautomatic and automatic stretch wrapping, automatic case handling, automatic palletizing, shrink packaging, and pallet-load conveying systems. A system such as its continuous motion SW-3000 shrink wrapper handles up to 65 packages/ min with production speeds up to 65 ft/min. The unit uses a variable frequency drive to provide electronically controlled film collapse and product spacing. A tension controlled trim winder for the side seal only pulls on the trim when it senses slack. The system does not use a clutch to compensate for the changing diameter of the trim spool as it increases from empty to full.

Choosing A Servo or Stepper Motor for Packaging Machines

Systems Engineer Lee Stephens, whose company, Danaher Motion, offers both servos and steppers, has these tips for picking the appropriate motor:
All things being equal, it is better to go with a stepper because the technology is easier to deal with.
In those cases where the positioning has to be repeatable and accuracy is a secondary concern, the stepper avoids the dithering of the servo.
Both servo and steppers could possibly coexist in some applications. Packaging that uses large film rolls could be handled with servos to avoid the changes in inertia problems that would confront the stepper. Stevens notes that he would readily recommend an open loop stepper for the roller cutter due to the single movement, constant velocity, and limited speed.

For a head-to-head comparison, Danaher’s P7000 microstepping drives and S200 brushless servo drives have similar current handing capabilities and about the same physical size. The P7000 can be configured as a closed loop stepper. But a motor with an encoder on the P-7000 approaches the price of the S-200, notes Stephens. The S-200 has higher acceleration, consistent speed torque curves, and no resonance characteristics compared to the stepper, so it becomes an obvious choice.

As long as it is cheaper in open loop and repeatable simple motion is required, “a stepper could be the best choice you could make,” claims Stephens. In dynamic applications where the inertial load is unpredictable or could change, the servo is a better choice.—RF

Maximize Your Torque

With the ability to “Maximize Torque at Desired Speed,” Lin Engineering has earned the reputation of being the technical leader in step motor design. Within the constraints of power input and motor size, Lin Engineering can design a motor to maximize torque at the desired operating speed. As shown in the graph below, Lin Engineering is able to provide valued customers with the maximum torque at both high and low operating speeds.

Not only is Lin Engineering able maximize torque at any operating speed, its motors also perform at maximum torque efficiency throughout the operating speed range.

Another benefit in choosing Lin Engineering over other step motor manufacturers is its ability to provide the right motor for the application the first time. Lin Engineering will eliminate the guesswork in motor selection. With Lin Engineering there is no need to buy multiple motors to find the correct one. Getting the right motor from Lin Engineering the first time allows customers to get their products out to the market faster and at a lower cost.

In addition to getting the right motor the first time, Lin Engineering is also able to provide shorter lead times. Lin Engineering can offer delivery of most customizations within three to five days due to the fact that its U.S. facility has on-site technical and design engineers as well as an assembly line dedicated to the design and manufacturing of prototypes and samples.

Lin Engineering also offers extensive customizations. No matter how simple or complex the request may be, Lin Engineering offers many mechanical and dimensional modifications to suit application needs at no additional cost. Just a few examples of shaft modifications that Lin Engineering offers at no additional cost are: double shaft, shaft length, single or double flats, standard or woodruff keyways, shaft diameter, hollow shaft, and through-hole shaft (threaded and non-threaded).

Kaydon® Bearings-An Industry Standard Since 1941

Since 1941, Kaydon Bearings Division has manufactured large and small bearings in standard and custom configurations for a broad range of applications and industries. With well over six decades of bearings experience, Kaydon has the expertise, proven designs and advanced manufacturing techniques to help solve your most challenging motion control problems.

As the world’s largest manufacturer of thin-section bearings, Kaydon sets the industry standard with Reali-Slim® thin-section bearings, which offer light weight, simplified design, long life, and reduced manufacturing costs. Reali-Slim bearings are ideal for aerospace, aviation, robotics, machine tools, semiconductor manufacturing, and medical equipment…anywhere a lighter, thinner bearing is needed. These bearings are available in different radial sections up to 40-inch diameters from stock, and larger on a made-to-order basis.

Turntable bearings are another Kaydon specialty. Applications for these dependable performers include swing bearings (slewing rings) for cranes, excavators, aerial work platforms, gun turrets, radar pedestals, forestry equipment, mining equipment, surveillance equipment, scanner equipment, and material handling equipment. RK Series turntable bearings are pre-engineered for light- to medium-duty applications. For greater load handling capability, Kaydon offers MT Series heavy-duty turntable bearings.

New-generation Reali-Slim TT Series miniature bearings are ideal for smaller turntable designs. They provide design flexibility, fast installation and change-out, greater accuracy, and the ability to withstand harsh operating environments.

Our custom miniature bearings deliver big advantages in dependability and long life for demanding applications-medical, dental, commercial aerospace and aviation, lab instrumentation, semiconductor manufacturing, and more.

Kaydon’s broad product line offering can also incorporate many special features, such as integral gearing or sprockets, through-drilled or tapped mounting holes and contact seals. These simplify design, reduce manufacturing costs and ensure long life.

Among Kaydon’s quality management and process compliance systems are AS9100. ISO9001: 2000, and Nadcap accreditation. Continuous improvement processes include JIT Lean and Six Sigma initiatives. Kaydon Bearings Division also provides a broad array of design and engineering services, including application support; custom, turnkey bearing solutions; and free, proprietary engineering and design tools.

AutomationDirect Steadily Expands Product Line

AutomationDirect, originally founded as PLCDirect in 1994, has grown quickly from a tiny PLC company to a well-recognized name in the industrial automation market. As the first industrial controls company to successfully use a direct sales model to market their PLC products, AutomationDirect provides customers with an online store or toll-free number for quick order and delivery, while also providing award-winning sales and technical support. Most prices are well below the industry average and a 30-day money-back guarantee is offered on nearly all items.

The breadth of AutomationDirect’s current product line is highly indicative of the company’s growth; total part listings have soared from roughly 200 to 5500 in 11 years. The motion control offering is expanding to include both steppers and servos. Newcomers to the family of power products this year are improved DC switching power supplies and a wide array of Edison fuses. The 2005 free catalog and online store feature the name brand and private label products available, such as PLCs, AC drives/motors, sensors, pushbuttons, enclosures, circuit protection and more. The 1750-page volume is filled with product descriptions, colorful photos, technical specifications, and a comprehensive price list.

AutomationDirect’s ability to sell high-technology automation products for very low prices relies on strategies employed to reach customers and the efficiencies inherent in the plant operation. The headquarters facility in Cumming, GA (30 miles north of Atlanta) is the sole location in the United States and is designed throughout for maximum performance. The company is able to take orders for in-stock items as late as 5 p.m. ET and ship them for next-day delivery.

In addition to quality products and low prices, the company’s customer support team has been rated top-notch by customers. AutomationDirect tech support was voted by readers of Control Design magazine as #1 in service and support in PLC programming software (2001-2003) and hardware (2002-2004). And, their own customer surveys consistently rank the company’s service as better than other suppliers.