Clever design drives packaging throughput

Visy Automation has developed a new-generation box ‘lidder’ machine founded on innovative drive technology from SEW-Eurodrive, delivering a powerful combination of speed, accuracy and throughput.

The SEW-Eurodrive Movidrive B’s integrated ‘modulo function’ positioning control is vital to the operation of the VL18 lidder machine.

Automated packaging machines lie at the heart of many modern industrial manufacturing processes. Originally developed to ease the burden on labour-intensive applications, automated packaging machines have evolved to incorporate sophisticated control technologies and other complementary systems. Today, much is expected of automated packaging machines - there is an increasing demand for such machines to deliver increased product quality, while at the same time optimising throughput and reducing operating costs.

The challenge for modern packaging solutions providers is to develop customised machines that improve efficiency and the manufacturer’s bottom line.

When Visy Automation embarked on the development of its second-generation inline VL18 lidder machine for Australia’s largest meat processor, Bindaree Beef, the company called on SEW-Eurodrive to provide an innovative motor and drive solution. All of the new lidder’s motion processes rely on SEW-Eurodrive electronic drive control technology and servo-geared motors. The result is a fast and efficient inline lidder machine, adaptable to nearly any box that comes off Bindaree Beef’s production line.

Visy Automation’s new VL18 lidder machine.

Paddle power

Visy Automation’s VL18 lidder machine features a clever dual-purpose conveyor design coupled with precision automation and a rapid-fire ‘head compression’ lidding system. Together, they ensure lids are glued onto unlidded boxes at rates of up to 25 per minute.

Visy Automation’s new VL18 lidder machine is able to glue lids onto unlidded boxes at rates of up to 25 per minute.

In operation, unlidded boxes are transferred into the head compression area for lidding via two side-by-side dual-chain conveyors. Each chain conveyor is equipped with two sets of ‘paddles’ positioned at opposite ends of the chain-set. One of the paddles from the first chain-set is used to push the incoming box into position and hold it in place from the incoming side. Once in position, a paddle from the second chain-set acts as a ‘torque-control’ paddle, holding the positioned box in place from the opposite side.

Each dual-chain conveyor is equipped with two sets of ‘paddles’ and driven by an SEW-Eurodrive geared servomotor.

The head compression system then delivers and glues the lid to the box in less than one second. Once the lid has been attached, the ‘torque control’ paddle releases the box by rotating under the conveyor. The first paddle then over-travels, effectively pushing the lidded box off onto the outlet conveyor. This first paddle then takes on the role of the ‘torque control’ paddle for the next box.

Unlidded boxes are transferred into the head compression area for lidding via two side-by-side dual-chain conveyors.

According to Peter Somogyi, Visy Automation Project Manager, the dual functionality of the paddle system is a real feature of the packaging machine. “The fact that each paddle does not have to go back to the start position after each box is lidded is a real time saver,” he says. “By minimising the number and length of machine movements, we have been able to develop an extremely fast lidder machine with the ability to deliver high throughput rates. This was made possible thanks to the clever application of SEW-Eurodrive’s drive electronics.”

Peter Somogyi, Visy Automation Project  Manager (left), discusses the VL18 lidder machine with SEW-Eurodrive Applications Engineer Spiro Limberakis.

The VL18 lidder machine is equipped with four SEW-Eurodrive geared servomotors, one on each of the chain conveyors, one on the head compression system, and one for the lid-transfer system which is responsible for feeding box lids to the head compression system. Similarly, each of the lidder machine’s four servomotors is combined with its own dedicated SEW-Eurodrive Movidrive B application inverter - all of these drives are linked to a single programmable logic controller via an EtherCat fieldbus.

According to Spiro Limberakis, SEW-Eurodrive Applications Engineer, the Movidrive B’s integrated ‘modulo function’ positioning control is vital to the operation of the VL18 lidder machine. “The real ‘smarts’ are in the two chain conveyor drives,” he says. “The modulo function control with encoder feedback is ideal for accurately controlling position in rotating applications such as this one. In this case, the drive can direct the chain conveyor to any one of eight paddle positions.”

Here, each motor is equipped with a 24-bit absolute encoder, which by itself is not adequate in such an application - after approximately two hours of operation the encoder will ‘overflow’, effectively forcing the drive and the chain to go out of position. Importantly, the Movidrive B inverter converts the existing 24-bit encoder into a 64-bit encoder by counting and storing the overflows in the inverter, eliminating the overflow issue of the encoder. The Movidrive B converts the motor encoder position into a modulo position on the chain. This means the conveyor/paddle position is known at all times. The drive is effectively programmed to go to a chain/paddle position rather than a motor position.

“Without the 64-bit enhanced absolute encoder and modulo functionality it would be impossible to determine where the chain is after several revolutions,” says Limberakis. “Even after multiple revolutions, the paddles can be taken back to the start position automatically - there is no need for the drive to return to a reference or zero point with this system, even after a power down.”

Anti-crash programming

Importantly, the drives have been programmed to use the ‘shortest path’ method of positioning. Here, the Movidrive B is ‘smart’ enough to accept a chain/paddle destination from the PLC and then determine which paddle should be moved in which direction (clockwise or anticlockwise) to ensure a paddle is in position in the shortest possible time.

“While this saves time between paddle movements and allows production rates to be optimised, it also presents challenges,” says Somogyi. “There is potential for the two sets of paddles to occupy the same space, so there needs to be high degree of flexibility within the drives to ensure that paddles from different chains don’t collide.” With this in mind, SEW-Eurodrive implemented unique control architecture and developed anti-collision software.

“While the paddle position of both chain conveyors is controlled by the PLC via the Movidrive Bs, the drives themselves are in continuous communication with each other in the background via a dedicated system bus,” says Limberakis. “The drives essentially monitor each other’s position in the ‘modulo world’. If the individual paddles get within a certain proximity of each other, the drives will ‘fault out’, avoiding a crash. They then go into recovery mode and travel to a known paddle position before the lidding process is recommenced.”

Visy Automation has also built reliability into the control system. “We’ve set up a ‘handshaking’ process between all of the drives and the PLC,” says Somogyi. “Each time a message is exchanged between the PLC and any of the drives, an additional confirmation message is sent before any action is taken. This only takes a matter of milliseconds, but adds an extra degree of reliability to the process.”

A collaborative affair

Traditionally, lidding machines have employed pneumatic systems for attaching the box lids, but these often suffer from speed, reliability and maintenance limitations. By teaming up with SEW-Eurodrive, Visy Automation was able to make significant improvements on the legacy design and effectively rewrote the book on lidding technology.

According to Somogyi, this collaborative approach yielded the innovative paddle design and operation concept of the new VL18 lidder machine. “We worked together to establish the best way to facilitate the movement requirements we had in mind,” he says. “We are able to take our engineering challenges to SEW and come up with an inventive solution. In this case, the modulo function was the key to the project. Without SEW, we wouldn’t have been aware of this capability.”

With the new VL18 lidder machine online at Bindaree Beef, Visy Automation is continuing to look for ways to optimise its design. “We’re already thinking of the next evolution of this machine,” says Somogyi. “There might be merit in integrating the gluing system with the drives. In fact, there’s even potential to go with a completely integrated control system by using SEW-Eurodrive’s PLC/motion controllers, Movi-PLC. Either way, we know we can count on SEW-Eurodrive’s support.”