The benefits of all-electric operation in performance, maintenance, and energy efficiency
are a major advance in palletizing technology.
Palletizers and pneumatic devices
Palletizers have traditionally used various pneumatic devices for machine functions such as case manipulation, layer clamping, pallet handling, and many other uses. The use of pneumatics has been considered an acceptable way of reducing the overall cost of a palletizer, and alternatives were often not practical. However, pneumatics continue to pose a number of challenges. Pneumatic devices require many position feedback sensors, have safety issues related to retained energy, and present a challenge in achieving consistent movement control. Overall, pneumatic devices require a high level of maintenance and performance is often marginal. In addition, devices driven by compressed air are notorious for energy inefficiencies.
Hybrid servo drive technology
Recent advances in motor drive control have provided the opportunity to eliminate pneumatics in favor of an all-electric palletizing solution. Electric devices used in place of pneumatics provide lower operational costs, simpler maintenance, and significant performance gains. Each electric movement has repeatable move profiles and variable positioning with exact control feedback. Closed loop positioning accuracies allows each component to operate more effectively and at higher speeds.
Palletizer device movements are achieved with EuroDrive gear motors equipped with 1024 count encoder feedback. Device movements to know positions provide significant advantages in performance, collision avoidance, safety, and speed regulation. Hybrid servo technology accomplishes the task.
B&R servo drives operating in VFD mode provide extremely accurate and refined motion of all primary components in closed loop positioning mode. Simultaneous motions of the palletizer are always monitored by the PLC to prevent collisions and optimize positioning accuracy for smooth damage-free product handling.*
Drives and PLC control
The machine control code operating on an Allen Bradley PLC provides all motion control. All move instructions with related code is communicated to each drive via high speed communications. Hybrid servo drives are electronic slaves to the PLC performing directed movement tasks and communicating status to the PLC. As such, qualified plant level personnel can monitor and adjust all performance parameters of the positioning system without any special training or knowledge related to B&R drives. Should an operational change be needed in the future, all VFD parameters are accessible and executable from controlled access HMI screens.
The replacement of a defective drive is completed in less than five minutes, with only two spare drives required. Following replacement, all drive parameters automatically download from the PLC to the replaced drive. Drive programming and drive set-up are not required at the plant level.S
B&R drives provide superior safety performance capabilities, exceeding typical "safe off" capability. The drives allow a single power feed to the common power supply feeding the DC bus to be disconnected by a safety rated contactor. This assures there is no power present downstream of the drives during an e-stop or controlled entrance condition. In addition, all residual DC bus power is also rapidly dissipated into a resistor and confirmed by the PLC whenever a fault or controlled entrance event occurs. The control side of the drives is 24 volt for rapid re-start when the machine resumes automatic operations.
The common DC bus backplane used by the B&R drives allows regenerative power to be used by any drive in the system. Regenerative energy captured as a byproduct of hoist lowering provides increased energy efficiency. Another advantage of the common DC backplane is the significantly smaller size of the drives, reducing panel size and wiring.
The plug & play feature of the new motor drive technology reduces the time required for machine assembly and start-up. The overall cost of all-electric palletizers is only marginal higher than models using pneumatics. End users adopting all-electric designs receive a value proposition with significant return on the marginal initial cost difference between all-electric and electric-pneumatic palletizers. The return is many times over the initial investment due to savings in energy and maintenance costs, setting aside the advantages of superior performance.
B&R hybrid servo drives operating as VFD's offer higher performance characteristics relative to typical VFD's. Positioning accuracy, load handling capabilities, regenerative capacity, and refined speed control constitute significant advancements in machine control. All-electric palletizer design provides superior performance, lower maintenance, and energy savings. Available in medium and higher speed configurations.
*Allen Bradley VFD drives are available as an option