FDBusiness.com

Crailsheim. The Kepak Group from Ireland now benefits from a new assembly and packaging line for hamburgers in which every individual unit responds flexibly to the product flow in the upstream and downstream sections of the line. Compared to a conventional
rigid system, this concept makes a huge difference to the average output performance. Temporary delays in one section of the line are automatically compensated without the need to use buffering systems. Instead of assembling and packaging the stipulated 80 meals per minute, on average the new line achieves an impressive 84 cycles.

In the past, six employees were busy every shift placing burgers in the buns and inserting them together with a sachet of sauce and a slice of prepacked cheese each into the blister packs of the running Multivac thermoforming machine.

These processes were automated from the turnkey supplier IPS International Packaging System. The product brief stipulated 80 products per minute. To achieve this output, it is not enough for the individual line components to be working at the specified speed. The whole concept hinges on perfect inter-coordination of the different processes.

There were two particular hurdles to be overcome. The manufacturing of the thermoformed blisters in the Multivac is done using an intermittent operating mode, while in the rest of the line product transport is continuous. Both motion principals had to be synchronised.

The provision of the three ingredients meat, cheese and sauce in loose form presents a further challenge. The customary standard procedure used for separation entails a high degree of mechanical component. The inevitable fluctuations in product flow which result from this type of machine-based solution tend to suppress overall output, making the stipulated 80 meals per minute impossible to achieve.

The main components of the solution: the TLM technology from Schubert and, to ensure a continuously high loose product separation output, feeding systems from Intellifeed (USA). Intellifeed precisely regulates product spacing using step motors in the roller transport system.

The line is supplied by three single-track feed systems: One for the frozen burgers in the first section of the line, and one each for the sauce sachets and cheese slices. The ingredients are tipped manually into the hopper, after which separation takes place: The path leading to the transfer point into the line is divided into sections, each with its own addressable drive unit. There are 30 stepper motors in operation at Kepak. The distance between the products is gradually stabilized. How the individual belt speeds have to be regulated is signalled by the optical sensor system (photocells).

This procedure guarantees separation on a continuously high output level without the need for buffering. The speed is important in two ways: Firstly to provide a high output, and secondly to ensure that the burgers are processed quickly enough to prevent thawing. The cheese slices are also easier to process when cold. An increase in temperature can cause the slices to begin sticking to each other. Incident light scanners integrated upstream from the transfer point to the assembly and packaging line provide the necessary quality assurance. These scanners are able to precisely identify buns, burgers, sauce sachets and cheese slices.

The first line section comprises two TLM machine sections with four TLM-F4 robot units. The buns enter the line on a wide product conveyor after being cut open by an upstream bun saw. The four-axis robots each take responsibility for a different task in sequence: One lifts the lid of the bun and places it alongside its base on the conveyor, the next picks up the burgers and places them on the bases, the lid is then replaced on the base and the assembled hamburger is transferred to the formation conveyor.

The assembled hamburgers then pass by the line section in which the blister packs are thermoformed. The next two machine sections are placed above the film web. Robots first insert the sauce sachets and then the cheese slices and finally position the hamburgers into the film cavities. The thermoforming machine closes the packs with the upper film, punches them out of the web and places them ready for the downstream processes.

All the units involved in the process, from the bun saw through to the thermoforming machine, are linked to the TLM line by means of signal exchange and a speed target value. Data exchange is organized on the level of the VMS control system supplied by Schubert.

The units react through the VMS control system to any product flow disruptions taking place in other parts of the line. If, for instance, the supply of burgers stops due to rejection of several products by the vision system, then the VMS control system slows down the dependent processes briefly until the quality target values are restored. The overall sequence is maintained and no rejects are produced. Compared to a conventional rigid system without regulation capability, the inability to react would result first in quality problems (hamburgers with no burger) and finally in a machine stop.

This optimized process management concept has permitted the thermoforming machine cycle to be increased to 88 products per minute. A change of format between the five different types processed takes in no more than five minutes: Three minutes to exchange the five tools at the TLM F4 robot arms and select the program at the TLM display, and depending on the packaging, another two minutes to change the film in the thermosetting machine. The overall line is configured in a wash down design, permitting high water pressure cleaning using detergents.

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