Robotics move palletizing into high gear

When it comes to in-line palletizing and depalletizing, many smaller packagers steer clear of automating, because it can be expensive, especially the more complex robotic equipment that requires on-staff specialists. But that's precisely the niche market Automated Motion, Inc. (AMI) (www.automated-motion.com), Edgewood, MD, is successfully developing, with its GP Series gantry-style robot. Incorporating a motion-and-logic control package, the system is affordable yet designed to help smaller packaging operations automate the pallet-building process. Or it can assist larger users that may run several stockkeeping units at slower rates or want to reduce robot training costs.

The servo gantry palletizers utilize a combination of Bosch Rexroth's (http://www.boschrexroth-us.com/) PPC-R motion control, a programmable logic control package and VisualMotion 10 software to simplify and facilitate pallet-building control and programming. As a result, the systems require less training by operators and maintenance staff to run, maintain and troubleshoot effectively. And it puts automated palletizing within reach for many of AMI's customers who want to replace hand palletizing.

United Biscuits' shortbread cookies are handled very carefully, transported from one packaging machine to another on Rexroth chain conveyors. Read about it at www.packagingdigest.com/
info/united.

AMI designs and builds robot systems in both a gantry style and with six-axis, articulated-arm manipulation. The versatile GP Series can be operated by manufacturers without the need for specialized robotic programmers. Explains sales manager Jeff Ayotte, "The advantage of using gantries is that they require a lower level of operator training than what's needed to run a full six-axis robot."

Incorporating the PPC-R controller (the R stands for rack-mounted), AMI's gantry palletizers efficiently palletize, depalletize and handle cases, cans, bags, boxes or other packages with a minimum of setup time. The gantry's five axes of motion include left and right motion, forward and backward motion, up and down motion, 360-deg rotation and 90-deg tilt capability.

"Typically, a gantry can handle heavier payloads than an articulated arm," Ayotte explains. "Both styles can usually perform twelve picks a minute, if not more. Running a larger number of stockkeeping units at slower volumes—say one to two cases per minute—the advantage of a gantry is that it can cover more pallet positions with one system. It's not a matter of one technology being superior; it's a matter of the requirements of the application. With robotics, you can palletize as many as the reach allows. A gantry can be designed to span a much larger area, and thus cover more [production] lines and pallet stations than can an articulated arm. The limit really depends on what the customer wants."

Ayotte goes on to say that the standard model of GP Series robotic palletizer gantries may represent only two-thirds of the cost of other robots, mainly because of the simple operation. "With drop-down recipe menus, a touchscreen operator interface and error diagnostic screens, the front-end control really makes it easier for the operator to learn. "Larger companies also like the Bosch Rexroth PPC controller, he says, because it provides open communication, allowing information-sharing using industry-standard protocols. "This saves time and improves performance across the entire line," adds Ayotte.

The PPC-R's teach function employs icon-based programming with standard ladder logic, which makes it easy to use in end-of-line applications, according to AMI. Its middle-of-the-road approach bridges the gap between operations that want to replace hand palletizing but can't or don't need to make the full leap to articulated-arm robotics. Says Ayotte, "It can also serve larger operations that want a cost-effective, work-horse machine for palletizing as many as twelve different products in one system."

At the heart of the control package is the PPC-R, a compact controller from Bosch Rexroth's Electric Drives and Controls technology group. Its platform works as a PLC and as a motion controller, depending on the application and software. It can solve complex automation tasks by grouping multiple PPC controls and masters and can manage up to two cascading masters and a maximum of 40 slave axes in a SERCOS ring. According to Bosch Rexroth sales engineer Peter Caldwell, who helped Ayotte design the control system for AMI, users may connect up to 32 PPCs to each other using a cross-communication interface, which allows the assignment of the master positions to the slave axes in various SERCOS rings. "AMI hasn't used this feature yet, but the idea is that one of its palletizers can be married to someone else's cartoner that uses a PPC, and the two machines can share position data to synchronize the positions," says Caldwell. The number of synchronized drives is almost unlimited, and it becomes possible to separate the machines into independent sections.

"We selected the PPC-R because it represents the latest generation of technology for combining motion control and PLC logic into one package," notes Ayotte. "An operator can run the entire machine with one package of software, and we don't need a separate PLC and motion controller."

Complementing the PPC is Bosch Rexroth's EcoDrive Cs, an extremely compact servo drive in the low power range from 100 to 750 W. The compact drive works on single-phase and three-phase supply systems with input voltages up to 230 V. Among the most compact servo drives available, most units are just 55 mm wide, 182 mm high and 170 mm deep. The EcoDrive Cs provides industry-standard interfaces, including SERCOS, DeviceNet, CANopen or PROFIBUS-DP. It is suitable for use in systems with interconnected, multi-axis configurations, or as intelligent single-axis drives on a standardized fieldbus.

Bosch Rexroth says the EcoDrive Cs firmware embodies process-oriented technologies, including electronic gearing, cam tables and fast registration inputs, making it a suitable choice for package-handling systems. User programming is simplified with intuitive, Windows-based commissioning software called DriveTop. The 16 Mbit/sec SERCOS interface also can be used with Bosch Rexroth's motion control solutions like the PPC-R, as well as third-party control systems.

Caldwell says the control system gives the gantry predefined kinematic functions. "PPC is our multi-axis control package. The software has specific features tailored to the packaging industry," he explains. "The time savings in programming, aided by icons and flowcharts can be a real advantage. The robotic kinematics are a popular feature and the main reason for our success with AMI. VisualMotion allows users to create complicated robotic motions easily. The user defines the XYZ axes and the kinematic they want. The rest is programmed using real-world coordinates."

The operator interface for the robotic series uses the Bosch Rexroth VCP25 operator terminal, which offers customized palletizing recipes in drop-down menu formats. This allows the user to easily change products from shift to shift, week to week, or as often as desired. Its error diagnostics indicate when a problem may be occurring, such as an obscured pallet or jammed product, and the control can manage up to 30 pallet patterns.

AMI also chose MSM permanent magnet motors from Bosch Rexroth for their reliability and maintenance-free operation, even in adverse conditions.

AMI began working with Bosch Rexroth on the palletizer project about a year ago. The models range from the GP1 to the GP12—the numbers designating the amount of different stations within the gantry. Supplied with three, four or five axes and many optional accessories, the robotic systems occupy a footprint with working envelopes up to 20 x 80 ft. The standard GP1 features include a three-axis servo system, belt-driven actuators with 1-mm/m accuracy, load capacities up to 70 lb, a 90-deg rotating head and simplified pattern creation from the operator interface.

The single-position GP1 is used to build or depalletize loads while the GP2 is for applications that need a second pallet build or a slipsheet stack. They can orient cases on a pallet and the five-axis model can flip cases on their sides while keeping labels facing out. So far, AMI has sold more than 30 GP Series units to many end users, including medical, automotive, industrial container and glassware manufacturers and canmakers.

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