Distributed NORD drives
Replace servos in palletizers
After extensive consultation with NORD DRIVESYSTEMS, Sacha Bakker, Managing Director and co-owner of the Dutch engineering company SYMACH Palletizers, made a fundamental decision. In the future, SYMACH palletizing machines will benefit from distributed drive technology.
NORD drive units, comprising geared motors and distributed frequency inverters , provide the required dynamic performance with fresh design possibilities for machine developers that result in improved reliability and a variety of cost savings. This sophisticated engineering project will be implemented on a long-term basis. The first series of palletizers with integrated motor control is now in successful use throughout the world.
In contrast with other available systems, SYMACH palletizing machines place products on the pallet individually, using a specially designed manipulator head that allows both precise and gentle handling. The 3 to 4 meter high machines are loaded via a conveyor belt with each sack, carton, or crate individually picked up by the manipulator. For example, sacks slide against a fixed stop and are aligned by a centering unit, so that the manipulator can lower them precisely at the programmed position. This enables accurate and overlapping stacking of the sacks with optimum stability. Various stacking patterns and speeds can be programmed. Depending on the palletizer model and the material, the maximum stacking speed varies between 15 and 36 sacks per minute. The pallets are mounted on a pallet table, which is lowered during the stacking process until the defined pallet height is reached. The loaded pallet is then transported to a pallet wrapping machine via a roller conveyor also produced by SYMACH and is then wrapped with stretch film for further transportation.
Change-over from central to distributed drive technology
Palletizing machines have a key function in production and distribution processes. They must operate smoothly in order to avoid slow-downs in the product flow. They must also be easily adaptable for various goods and applications. In the past, SYMACH always used centralized drive control units, which required switching cabinets to be mounted on the top of the machine. This took up a lot of space and resulted in additional costs. “The height of a palletizing machine requires the installation of steps in order to carry out maintenance work”, explains Bakker. “The switching cabinets for the servo controls obstructed access. By converting to compact NORD drive units, it was easy for us to eliminate this problem.” In the new palletizers, geared motors with SK 200E series frequency inverters mounted directly on the motor perform the complex movement sequences of the manipulator and the centering unit. Following the recommendation of NORD, it was decided to use dynamic asynchronous induction motor technology instead of servo technology. The advantages of this solution not only include lower procurement costs, but also greater selection possibilities for machine designers, as asynchronous induction motors are widely available, maintenance-friendly, and can be easily combined with various types of gear units . In addition, the shaft and flange mounted versions are easy to replace. In total, these advantages mean that “asynchronous palletizers” incur lower overall operating costs than palletizers equipped with servo motors.
Distributed frequency inverters deliver precision and dynamics
Distributed automation applications place great demands on drive systems. Comprising several performance-graded models and various functional upgrade options, NORD’s SK 200E frequency inverter series enables users to select tailor-made solutions for each specific requirement. Models of sizes 1 to 4 cover performances between 0.25 and 22 kW. The modular series enables the economic implementation of distributed applications ranging from simple start-stop control functions to complex positioning tasks. Upgrade options include external brake resistors and a separate 24 V power supply for stand-alone control voltage regulation. In addition to fieldbus interfaces for CANopen, DeviceNet, and Profibus there are also gateways for integration into PROFINET and EtherCAT networks. Interfaces for further industrial Ethernet standards are currently being developed. The fieldbus communication interfaces are available as external bus technology units with or without additional I/Os, which can be mounted directly on the inverter or separately on the machine frame or nearby equipment.
SYMACH palletizing machines use the POSICON function, a standard feature of all SK 200E frequency inverters, which enables highly dynamic positioning functions with a maximum precision of approximately 1/100 of a rotation of the motor. The new and very compact NORD MG encoder system is used to detect position and orientation. The distributed inverter enables considerable simplification of installation and wiring. The drive manufacturer supplies the ready-wired motor, brake resistor, and motor holding brake. SYMACH uses machine-integrated SK 215E inverters with the additional “Safe Stop” function, which ensures the necessary personnel safety. Further features of the versatile SK 215E units are used in the palletizing machines: sensors and actuators are simply connected to the inverter I/Os with information sent to and from the control unit via CANopen communication. This also reduces the number of cables which need to be wired.
The implementation of the new drive concept was carried out step by step. “NORD played an important role as our supplier and consultant”, says Bakker. “A supplier who supports you and thinks along the same lines provides a great opportunity. This was precisely the case with NORD. Not the quality of the products alone was decisive for us, but also the good relationships which we have built over the past years with NORD as our global partner.”
SYMACH delivers its palletising machines throughout the world, so Managing Director Bakker is pleased that with NORD he has a supplier that is also globally active. "Our market has potential for growth", speculates Bakker. "We will come into play once the necessary developments, for example in the agricultural sector in countries such as China, Brazil and India have advanced sufficiently, and the demand for palletisers becomes apparent."