When it comes to palletizing or depalletizing in a packaging line, many smaller companies have stayed away from automated systems because of high costs associated with complex robotic equipment and on-staff specialists.
As an alternative, Automated Motion, Inc (AMI) has successfully developed a reliable and easy-to-operate gantry style robot that uses a combined motion-and-logic control package to help make automated pallet-building an affordable option for smaller companies, or even large users running many SKUs at slower rates.
AMI''s GP Series of servo gantry palletizers utilize a combination of PPC control and VisualMotion software from Bosch Rexroth to simplify the machine control package and make programming easier. As a result, operators and maintenance staff require less training to run, maintain, and troubleshoot the equipment effectively. This puts automated palletizing within reach for any company that wants to replace hand-palletizing but cannot afford a more complex robot, or for companies that want to reduce their training costs for using robots.
Functional and Affordable
AMI has experience designing and building machines with both gantry style and 6-axis articulated arm robots. The GP Series was designed to satisfy a niche of manufacturers that want versatile robotic palletizing without the need for specialized robotic programmers on staff.
"The advantage with using gantries is that they require a lower level of operational training than what is needed to run a full 6-axis robot," says AMI sales manager Jeff Ayotte.
Using Bosch Rexroth components, AMI''s GP Series servo gantries efficiently palletize, depalletize, and handle cases, cans, bags, boxes, or other packages with minimum setup time. The gantry''s 5 axes of motion include left and right, forward and backward, and up and down motion, 360 deg rotation, and 90 deg tilt capability.
"Typically, a gantry can handle heavier payloads than an articulated arm," says Ayotte. "Both styles can usually perform 12 picks per minute, if not more. For a larger number of SKUs which run at slower volumes (1 to 2 cases per minute), a gantry''s advantage is that it can cover more pallet positions with one system," he says. "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, thus covering more lines and pallet stations than an articulated arm. The limit really depends on the customer," says Ayotte.
Since the GP Series of gantries do not require specialized training to operate, a standard model may represent only two-thirds the cost of other robots. "This means that smaller shops can now consider cost-effective automation," he explains. "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 because it provides open communication, allowing information sharing using industry standard protocols. This saves time and improves performance across the entire line," he adds.
The teach function on the Bosch Rexroth PPC uses icon-based programming with standard ladder logic, which makes it easy to use in any end-of-line application.
"It is especially suited to 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, workhorse machine for palletizing as many as 12 different products in one system."
AMI''s GP palletizer models range from the GP1-GP12, with the 1 and 12 representing the number of different stations within the gantry. Supplied with three, four, or five axes, the series has a small footprint with working envelopes up to 20 x 80 ft, and many optional accessories.
Standard GP1 features include a 3-axis servo system, belt-driven actuators with 1 mm-per-meter accuracy, load capacities to 70 lb, a 90-deg rotating head, and simplified pattern creation from the operator interface. Options include up to 12 pallet stations, full pallet discharge conveyors, light curtain access/egress, 360-deg servo rotating head, a multiple case or layer pick gripper, and load capacity to 1,500 lb.
The GP1 gantry, for example, is a single position gantry typically used as a pallet build or depalletizing station. Applications requiring a second pallet build, or slip-sheet stack, are ideal for the GP2. The GP Series gantries can handle up to 12 different stations, orient cases on a pallet, and with a 5-axis model, flip product on its side while keeping labels facing out. A second pallet position can be used for slip-sheets or top caps, to name a few options that can be incorporated into the layout. The GP Heavy Duty model can cover a large working envelope and can handle 1,500 lb. The GP Series palletizers can also be configured to accumulate and palletize an entire layer with vacuum cups or a Unigripper™.
Getting It Under Control
Spearheading the control package is the Bosch Rexroth PPC-R, a powerful controller in a small size from the company''s Electric Drives and Controls technology group. Its platform works as a PLC and as a motion controller, depending on the application and software. Complex automation tasks can be solved by grouping multiple PPC controls and masters. The PPC manages up to two cascading masters and a maximum of 40 slave axes in a SERCOS ring. Up to 32 PPCs can be connected to each other using the cross-communication interface, which allows the assignment of the master positions to the slave axes in various SERCOS rings. The number of synchronized drives is almost unlimited and separating the machines into independent sections becomes possible.
Bosch Rexroth sales engineer Peter Caldwell helped Ayotte design the control system. "We selected the PPC because it represents the latest generation of technology for combining motion control and PLC logic in one package," said 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 100-750 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, and is suited for use in systems with interconnected, multiaxis configurations, or as intelligent single-axis drives on a standardized fieldbus. The EcoDrive Cs firmware embodies proven, process-oriented technologies, including electronic gearing, cam tables, and fast registration inputs, making it an appropriate choice for handling systems. User programming is simplified with intuitive, Windows-based commissioning software called DriveTop. The 16 Mbit/sec SERCOS interface also allows trouble-free use with Bosch Rexroth''s motion control solutions, like the PPC-R, as well as third party control systems.
According to Caldwell, the control system gives the gantry predefined kinematic functions. "The control system has already translated the real-world applications into axes of linear motion, so all the user must do is enable the functions," said Caldwell. "The time savings in programming, aided by icons and flow charts, is a definite advantage compared to other text-based products which require a greater level of operator training."
For its operator interface, the GP Series uses the Bosch Rexroth VCP25 Operator Terminal, which provides customized palletizing recipes in dropdown menus. This allows the operator to change products easily from shift to shift, week to week, or as often as required. The control system also includes error diagnostics that tell the operator when there is a problem, such as an obscured pallet or jammed product. The standard control system can manage up to 30 pallet patterns.
Bosch Rexroth MSM permanent magnet motors complete the cost-effective automation system. The motors are characterized by high operational reliability and maintenance-free operation, even under adverse conditions. These benefits are attributable the motor''s brushless design and grease-lubricated bearings, as well as its completely closed motor design with IP-65 protection.