Technical profile: flour packaging breakthrough

by Teresa Acklin
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   The new Futura packaging system developed by Buhler is designed to meet the growing demand for equipment that can handle more bags of different weights, provide greater weighing accuracy and allow for more flexibility in changing product lines and bag weights. Other improvements include dust reduction, improved bag handling and easier cleaning.

   In addition to the innovation in weighing technology, the system features new developments in the design of the carousel, bag placing, bag closing and palletizing. The filling system is designed to reduce excess air and vibration problems.

   The Futura system can handle bag sizes of 25, 32 and 50 kilograms at rates of 1,200, 960 and 720 bags per hour. But the most important development is a completely new approach to weighing. This approach uses the technique of differential weighing instead of the traditional method of net weighing. Bags are filled from two master scales while a third tops up to the correct weight. Material is discharged from the storage hoppers via

Up to 20 bags/min.£25kg
Up to 16-17 bags/min.32kg
Up to 12-13 bags/min.50kg

   Rotoflow vibro-dischargers, which are designed to handle free flowing and sluggish bulk materials. Material is fed to three differential bagging scales by screw conveyor with gravity diverters to the spouting system.

   The screw feeders may feature a withdrawal mechanism designed for time saving and quick cleaning. Use of screw conveyors helps to compact the material and to reduce air problems and the amount of dust. Routing boxes change the flow from one scale to another.

   The material is then weighed by the two master scales in the weighing container, which is controlled by three load cells. Each weighing container can hold enough for two to three bags. Discharge into the bags is controlled by a screw feeder with a motor-powered closing slide.

   The bag carousel has been reduced in size. There are six spouts, which are smaller than traditional spouts — another design factor that helps to reduce dust problems. The compacting unit is integrated into the main support of the carousel, which is now supported from the floor. This helps to reduce vibration effects.

   The bag magazine stores a large number of bags that are picked up at the bottom by the bag placer to hang vertically. Bag placing and loading takes place in four cycles. The process has been improved by the incorporation of an electronic system that aligns the bag top to dispense with the need for trimming. Paper bags are sealed with glue, which means there are no problems with string and they are easier to open. Plastic sacks, however, still have to be folded and sewn.

   The flexibility of the machine in dealing with a range of different sack sizes meant a complete new design was needed for the palleting system to handle different configurations. These are handled automatically according to the size of the sacks.

   The bags are first pressed into a uniform shape before being laid on the pallet, which has been covered with polythene sheeting before being moved from the magazine to the lifting table.

   A pallet takes one and one-half minutes to load, and each magazine holds up to 45 pallets, sufficient for one hour's bagging capacity.

   The pallets are stacked five layers high. High levels of accuracy in stacking the empty bags and the filled pallets are essential for the handling system to work efficiently.

   One of the first commercial Futura units has been installed by Allied Mills Ltd. at Chancelot Mill in Edinburgh, Scotland, where Allied has worked with Buhler to streamline the operation and coordination of the machines. The unit has been designed to provide the high level of flexibility and accuracy required for the wide range of flour and pack sizes produced for customers.

   Chancelot Mill, currently one of the most advanced of Allied's production units, is the largest milling unit in the U.K. in terms of single capacity and is one of the most highly automated in the world. Production can be varied at each stage of the flour manufacturing process, which provides for a possible 20 stages of rolling, sifting and reduction to allow for the output of the 100-plus different product lines required by customers. A small, highly trained team packs and stores the flour in ratio to customers' requirements. A Buhler Type MWTW bag-closing machine allows a dust-tight seal at high speed, which has reduced the amount of airborne flour and helped to maintain a cleaner working environment.

   The new Buhler palletizer Type MWPY presents an improved pallet configuration that has not only allowed high flour stocks and, therefore, increased capacity, but also has improved safety within the bagged flour storage area as well as the visual character of the warehouse.

   Keith Sutherland, managing director of Chancelot Mill, says, “We are pleased with the packing power and flexibility of our new packing line. Considerable development time has been invested by Buhler to fine tune their new machine designs, and this has helped us rationalize our packing/warehousing operation to the financial benefit of our business.

   “The installation of the Futura system also disciplined us to review the organization of our warehousing operation and planned maintenance schedules,” Mr. Sutherland continues. ”Six months down the line, we are in much better shape to cope with the changing pack size requirements of our customers.”

   Contributed by suppliers, technical profiles feature new technology, products, specific applications or proprietary concepts. This material was provided by Buhler A.G., Uzwil, Switzerland.