We have recently installed a system for collecting and feeding rusks into the packaging sector, in an important company in Northern Italy. It is the only one of its kind in the world
The product is laid out on the oven’s toasting mesh in forty compact, carefully aligned rows by means of a slice spreader, also designed and constructed by PreMec, into which loaves of bread are fed from a slicing machine. Production runs at 2400 slices/min, which corresponds to an end product of approximately 1100 kg/h. The format adopted for the packs is twin-slice, and these are stacked in groups of two single products or pairs, in flow-packs. Pack formats with stacks of 3 or 4 single products or pairs can also be produced. Unlike the conventional automatic systems that have been used up until now for this purpose, when the slices are fed out of the oven, they are not subjected to a series of transfers and handling processes in order to align them, place them on their sides and load them into stacks for the packaging machine. Instead, this system picks the slices up only once and takes them directly to the flow-pack packaging machines.
The system consists of a slice spreader upstream from the toasting ovens. This ensures that the slices are laid out perfectly on the toasting mesh. A vision system then commands the bridges that handle the slices (so that each bridge tracks and picks up the correct group) and four robotic bridges linked to four flow-pack packaging machines, plus a reserve unit.
The vision station also runs a quality control function automatically, which checks the shape, surface, colour and presence of holes in the individual slices and indicates to the pickup bridge which ones need to be rejected. These are then left to continue and collected in a container at the end of the oven mesh. The statistics that are obtained regarding deviations from preset quality criteria also give useful indications for correcting process parameters.
The bridges pick up groups of forty slices with a three axis-control head fitted with twenty pairs of suction cups mounted on independent pneumatic cylinders. When the signal arrives from the vision system, the head lowers and picks up twenty pairs of slices which are then lifted and carried to an automatic retraction table located above the packaging machine chain, where the stacks are formed.
At the end of this operation the stacks are released into the chain which then feeds them into the corresponding packaging machine individually or in pairs. The four production bridges produce 600 slices/min. with packaging machines producing 300 packs/min. for single stack formats. The production rate for these bridges is 15 cycles/min.
The number of channels on the edge.mec. Loader depends on the set up of the system and the number of packaging machines needed to satisfy the requested production load. The loader speed depends on the size of the product and the length of the dose, and can reach up to 25 cycles per minute. This number multiplied by the channels indicates the number of doses per minute released towards the packaging machine.
The bridge is operated by five controlled axes that move the head up and down, and forward and back, recover any slippage in the flow and chain step, open the discharge table and drive the chain. This new patented technology offers multiple benefits. First and foremost, it minimises the breakages and crumbs caused by multiple handling operations and slice pressing and scuffing that happens with conventional systems. Hygiene is another key factor, as the path the slices follow from the mesh to the packaging machines takes place in an operator and pollution-free environment.
The space taken up is also significantly reduced and plays an important role in a comparative assessment. The total absence of personnel in the bridge zone has a major impact on management costs, too. Consider for a moment, that a conventional line with the same production features (surveillance, adjusting products that are out of place in the channels, eliminating broken pieces and regulating dose formers etc.) requires an average of five people per work shift without counting those involved in quality control operations that have to be performed manually. To finish, the data collected by the management system throughout the eight months of full speed operation demonstrate complete mechanical and electrical/electronic reliability with a superior yield of 99%, considering that any product groups that are not picked up by a bridge because the corresponding packaging machine has been stopped, are picked up by the last bridge and packaged in the reserve machine. The system can be used to handle not only rusks, but also particularly fragile products, like filled biscuits, rice cakes or shortbread, in stacked formats, as long as they are laid out in ordered rows. Lastly, the level of investment is compatible with that of traditional systems. This factor, combined with its low running costs and other benefits that have already been emphasized make the bridge a particularly beneficial production tool.
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