Packs of food with card sleeves are much in demand by major retailers, but applying those sleeves has, until now, been an inconvenient and labour-intensive manual process. To address this situation, Keymac Packaging Systems – a UK-based company whose staff has extensive experience and expertise in packaging – decided that the time was right to develop a versatile and affordable automatic pack sleever.
In principle, the operation of the machine is simple. A feed conveyor carries a tray pack into the machine, while a card sleeve, still flat at this stage, is dispensed from a hopper. The sleeve is formed and the tray is pushed into it. The sleeved pack is then transported out of the machine. In practice, however, the requirements are a little more challenging.
To satisfy the demands of users in the food industry, the machine must be able to handle oval, round and rectangular packs in a variety of sizes, and it must be capable of accepting the packs either continuously or presented at random intervals. It must also be compatible with full sleeves, band sleeves and narrow watchstrap sleeves. Finally, it must have a high enough throughput capacity to match the output of a typical food production line.
Meeting these requirements meant that the machine would need a sophisticated motion control system. This challenge was met when Keymac evaluated the new Trajexia motion control products from Omron.
A modular system, Trajexia supports up to 16 servo axes with independent position, speed or torque control for each axis. In addition, inverter drives and remote I/O can also be added. Its powerful software is designed to make programming intuitive and straightforward, and it features an advanced 32-bit digital signal processor (DSP) allowing it to handle demanding motion control tasks, including electronic camming.
“The Trajexia controller gave us exactly what we needed technically,” said Mike Bradley, Keymac’s managing director, “In addition, we were very happy with the idea of using equipment from Omron as we have always had good experiences with the company and its products.”
In the new Keymac Autosleeve K101 machine, the Trajexia motion controller is configured to control three servo axes. Two of these are needed to position the trays, as their varying size and shapes mean that they must be driven from both sides. The third servo axis controls the loading of the flight lug which performs the critical operation of pushing the pack into the formed sleeve.
To allow the machine to operate dependably while achieving the necessary high throughput rate, the motion controller provides exact synchronisation between the axes. In addition, to ensure that the packs are consistently and accurately positioned within the sleeves, the controller implements a complex electronic cam profile for the flight lug drive.
In addition to their sophisticated motion control features, Trajexia controllers also offer 16 digital inputs and eight digital outputs, all of which are assignable by the user. By making use of these to provide the logical control functions needed by the Autosleeve machine, the Keymac engineers were able to eliminate the need for a separate PLC, thus achieving a cost saving. Other Omron products used in the machine include variable speed drives for the conveyors and a colour touch-screen terminal.
The terminal provides end users of the machines with a wide range of benefits, including instant visual confirmation of all key operating aspects, access to production counts and, in the event of a machine stoppage, detailed information about the cause. In addition, by simply touching the screen, the operator can adjust the machine’s running speed, fine tune the positioning of packs within the sleeves and set the operating parameters of the motion control system to suit different types and size of packs and sleeves.
The servo drives, inverters and motion controller are all linked by a Mechatrolink II network. Optimised for use in systems which incorporate motion control, this provides dependable high-speed communication while greatly reducing the amount of cabling needed on the machine. Furthermore, a wealth of axis information is available to the user via the Mechatrolink II network.
In addition to Mechatrolink II networking, the Trajexia motion controller also offers Ethernet support, which Keymac plans to use on future machines as the basis for offering remote diagnostic functions.
The first of the Keymac Autosleeve K101 machines are now in service and are consistently achieving throughput rates of 60 packs per minute, even with the largest packs. This compares favourably with typical manual sleeving rates of around 40 packs per minute with two or even three operators working simultaneously.
Further benefits of the machine are that it takes only five minutes for changeovers between different types of pack, that it does not require the sleeves to be pre-broken along the score lines, and that, when running, it requires almost no operator attention. All that is needed is for the high capacity sleeve magazine to be refilled from time to time.
“Our new machine is generating a lot of interest in the food industry, where potential users are quick to understand the cost savings it can offer,” said Bradley, “so we are confident that we wll be building many more of them.
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