Packaging for experts

French company Euro Cri, based in Coulommiers, has been developing and building packaging machinery for more than 20 years - from stand-alone modules through to complete packaging lines. They also upgrade packaging machinery. The emphasis is on packaging machines for end products and development has traditionally focused on the productivity of each individual machine.

Foodstuffs must be packaged precisely, safely and, above all, carefully. That final factor alone presents a particular challenge for packaging line manufacturers, whose machines need to meet increased standards when packaging delicate foodstuffs. For example, when positioning or spacing products, it is particularly important to avoid them being flattened or becoming damaged during the actual packaging process. What’s more, packaging machines for the food industry should also be able to guarantee higher-frequency packaging.

The Dynamic Stocker accumulator made by Euro Cri converts an irregular product flow at the output of a production machine into a regular flow, as found when packaging biscuits, surimi or chocolate for example, and that’s before the products reach the packaging machine - a horizontal flow packer. The accumulator gathers the unpackaged products as they arrive and creates a ‘buffer store’, which can be regulated according to the change in the material flow.

The accumulator, which was integrated into an existing packaging line, was developed and built by Euro Cri in close cooperation with Strasbourg-based Pilz France Electronic, the French subsidiary of Pilz GmbH & Co KG.

The greatest challenge was to arrange the packaging process so that it was synchronous with the rhythm of the existing horizontal flow packer. The flow packer forwards incoming products in an irregular sequence. No pressure may be applied, nor may any friction be created, so it is important that the products have only the slightest contact and are forwarded immediately - whether individually or in groups.

The development and design therefore demanded an automation solution that was not only capable of controlling complex movements but could also handle various transport speeds simultaneously. The focus was on the movement of six axes: the incoming, connecting and outgoing conveyors, the separators, the axes for synchronisation and the flow packer. It had to be possible to coordinate the axis movements with 100% accuracy, so that the various speeds at different points of the conveyor could be synchronised precisely and safely regulated.

Euro Cri opted for a Pilz motion control solution (PMC), which enables precise synchronisation of the respective motion processes.

Pilz France supported Euro Cri from the planning and development stage right through to implementation and commissioning on site at the customer’s premises. The Dynamic Stocker has been developed to meet the customer’s specific requirements and the engineering process was focused on performance optimisation and the reduction of implementation costs.

The central element of the motion control solution is the PMCprimo 16+ controller that performs the complex motion and control functions.

Used in conjunction with the PMCtendo DD servo amplifiers and the PMCtendo AC servo motors, it produced a drive solution that could react flexibly to different format specifications and could be used to easily implement high cycle counts. The PMCtendo AC motors provide particularly good controllability, in that the absolute position of the motors can be read not just during operation but also after the machine is shut down or after a power failure. The open hardware and software architecture enabled staff to get to grips with the system quickly and easily. In addition to simplifying positioning tasks and storing motion tasks, the PMCtendo DD also provides the power supply and motor drive on the Dynamic Stocker. Communication between the control system and servo amplifiers is via CANopen.

The packaging process can be monitored and regulated using PMIvisu operator terminals. The motion curves relevant for the cycle are calculated in the simplest way possible: the operator simply enters the set data on the operator terminal - the packaging length and the position of the section to be embossed, etc - and the system automatically calculates the motion profile for run time. Any adjustments for new products are made via the operator terminal, whereby the material flow control system reliably fulfils all requirements regarding the different product types. The display can be used not only to select recipes but also to view precise, clear error messages. The cause of any error always appears first; at the touch of a button the operator then receives specific instructions on how to rectify the error.

Safety-related functions such as emergency stop, emergency off or safety gate monitoring on the Dynamic Stocker are monitored via the PNOZsigma compact safety relay, while PSENmag non-contact magnetic safety switches are used for safety-gate monitoring. These meet the very highest hygiene requirements and provide simple protection against defeat in accordance with VDE 0660. The PSENmag safety switch was incorporated into the overall solution to ensure that the packaging process is not interrupted unnecessarily, as it excludes the possibility of the switch being operated unintentionally.

“With Pilz we have gained a competent partner in the automation industry. We will continue to work with them in the future to develop leading-edge packaging systems for our customers,” said Mathieu Carie, Head of Automation at Euro Cri.