Shorter Changeover Times, Fewer Rejects, Less Downtimes

Mechanical lifting curves have proven themselves in the implementation of lifting processes for decades and will continue to be found in many filling and closing machines in the lower and medium performance segment,”Franz-Josef Patzelt, one of the managing directors of Franz Tölke GmbH, is convinced. "With their electronic counterparts, however, the filling process can be adapted to individual product requirements much more easily and a product change can be carried out faster, as more and more users demand," continued Tölke. So far, the metering in simple rotary filling machines has generally been realized by means of pistons, the stroke movement of the piston being carried out via a mechanical stroke curve.

Competing dosing processes

The advantage of piston filling is that the filling quantity already delivered is always known during the filling process. This is used, for example, for media that tend to foam to raise the filling needle over the stroke curve synchronously with the filling level so that it does not immerse in the medium. Despite this compelling advantage, there are some disadvantages to piston technology. The piston is difficult to clean due to the necessary piston seal and is only partially CIP / SIP capable. In addition, the mechanical impact of the piston changes some products. It is also disadvantageous that large filling volumes require large pistons and that a change in the metered quantity can therefore only be implemented to a limited extent without an expensive conversion of the machine.

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As an alternative to piston metering, the filling quantity is therefore determined by measuring the flow of the pumped volume flow. The advantage of this process is that the filling quantity can be easily changed when changing the product. On top of that, only minimal mechanical forces act on the medium and there are no mechanical parts that require maintenance. CIP / SIP cleaning is possible without any problems.

Decoupling the movements

"In a rotary machine with a filling quantity metering based on a flow measurement, however, the filling speed is then decoupled from the stroke-curve-controlled movement of the filling needle", Franz-Josef Patzelt points out. This means that if the machine runs slower or faster than the nominal speed, the containers are filled earlier or later. "Depending on the speed, the machine then needs, for example, 270 ° or only 30 ° to turn the rotary table," the Tölke managing director concretizes the problem. "As a result, the filling needle is immersed in the product during the filling process, or the drop to the filling gel is too high, and there is a risk that the system will become contaminated with dripping product residues or air bubbles will be trapped in the product."

Linear motor

Linear motor with alternative cable outlet

For example, bottlers who tend to foam products often had to use linear machines in the past. In these systems, the filling needles can be coupled mechanically and raised comparatively simply using an electric motor at the same time as the filling level rises. Due to their design, linear filling machines are only suitable for small to medium filling capacities of several thousand bottles per hour. On the other hand, only rotary machines are suitable for hourly filling capacities of over 10,000 bottles. Here, however, each needle must be lifted individually at the right time to avoid immersion at different machine speeds or to keep the drop height to a minimum. A precise positioning of the axes is essential.Tölke has now succeeded in doing this by using powerful linear motors from Linmot.

Flexible rotary machine with linear motors

The users of a rotary machine with an electrically driven filling needle benefit from a whole range of other advantages. Product changes that only require a change in the stroke movement of the filling needles can be carried out at the push of a button. This eliminates the time-consuming and costly conversion of the mechanical lifting curves. A wide variety of travel profiles can also be implemented and, for example, bottles of different shapes can be filled without having to adjust the entire system structure.

Thanks to the precise position measuring system of the linear motors, the filling needle can also be moved with an accuracy of 0.1 mm above the filling level. The acceleration values ​​when lowering and raising the filling needle can also be individually adjusted as required to reduce the mechanical stress and to optimize the handling of the filling medium. "Even a highly dynamic raising of the needles is possible when using linear motors, because unlike mechanical stroke curves, no destructive forces act on the bearing shafts," explains Markus Kröger, responsible project manager at Tölke.

Tölke used the mechanical decoupling of the stroke movement of the filling needles from the movement of the carousel or rotary plate associated with the introduction of the Linmot motors to consistently drive the modularization of the machine. Each filling module now forms an autonomous unit consisting of a flow meter, linear motor, servo controller and filling valve. If a filling station is damaged, it can now be replaced in a short time, so that the machine can resume work much faster after a collision, for example.

Reduced downtime

The decoupling also made it possible to complete the filling process for all containers in the system before a planned machine stop and to put the machine in a safe state. In addition, the technology allows the machine control to be designed so that if individual filling stations fail, the filling heads concerned move to a safe position and exit the active filling process. This reduces machine downtimes to a minimum.

However, the use of linear motors offers further advantages that support Industry 4.0 concepts: Information provided by the servo drive, such as the current motor temperature or the course of the acceleration, can be used to monitor the filling process, for example, mechanical problems (condition monitoring) or collisions recognized early. The machines recently equipped by Tölke with the new technology include a blocked filling and closing machine with 36 filling stations and 16 closing stations, with the stroke movement of the filling needle being mapped with Linmot linear motors.

Stainless steel motors in IP69K

These direct drives are made entirely of stainless steel and have protection class IP69K. Seals have been deliberately avoided in the engine design. All connections are welded. The motors are also fully potted to prevent condensation from forming. Thanks to these properties and the closed, easy-to-clean stainless steel surface, the Inox motors are ideally suited for use in machines and systems for processing food, cosmetics or pharmaceutical products.

For those responsible at Tölke, that was not the only reason why they decided to use the stainless steel motors from the Swiss company. The small space requirement of the motors was a decisive factor, as there was limited space on the rotary table. "The linear motor as an integrated unit is easier for our designers to use than a serovomotor-ball screw combination and takes up little space," summarizes Markus Kröger. (br)

Hannover Messe 2017: Hall 16, Stand E16