Afripack is a progressive packaging company that supplies high-quality packaging products to the southern African and related markets. The product range includes paper sacks, shrink and stretch sleeves, extrusion coating, pouches and a variety of other flexible packaging products.
The initial design of its laminating machine, which produces poly-coated paper and foil laminates for the packaging industry, was sufficient to meet the company’s original requirements. However, as the demand for product expanded through other industry sectors, the machine’s apparent shortcomings came to light in terms of the low running speed and limitations in the tension control system.
Laminating system upgrade
Afripack Mobeni decided to design and build a replacement machine in-house and Hybrid Automation was tasked with upgrading and developing the reel-to-reel tension control for the new Triplex laminating machine. The project comprised a main unwind, auxiliary unwind, two treating stations, two dryer stations (ovens), three nip points, extruder die, chill drum and a rewind system.
Hybrid Automation installed a Siemens S7-300 PLC, three CU320, seven motor modules, two dual-channel Siwarex weighing modules, seven distributed I/O stations connected to the S7-300 PLC, as well as seven AC motors and drives and five DC motors and drives.
Through the advanced technology of axis control on the Siemens S120 range of drives, Hybrid Automation achieved a machine speed of 350 m/minute with optimum tension control and automatic splicing at line speed at the unwind and rewind points.
Coating system upgrade
Next, the old coating machine was retired in July 2012 opening the way for all the old stations, including electrical panels and field wiring, to be removed. Hybrid Automation, as the Siemens system integrator, worked closely with Afripack engineers to develop the new control system from the ground up. During the commissioning phase there were many challenges, especially with respect to achieving the best tension control throughout the machine from the unwind to the rewind. This was a steep learning curve for Hybrid Automation as it was the company’s first project of this capacity in the reel-to-reel industry.
Feedback to the drives was not traditional PID control but a dynamic implementation that required a combination of diameter calculation and dancer feedback, all relative to the line speed. This required intensive tuning to achieve consistent tensions.
Another challenge was the web tension control, which required expert assistance from control technology specialist, Brian Caulder. Hybrid Automation introduced three nip points with load cell feedback to maintain web tension on the machine. Two of the biggest system challenges were controlling tension of the 7 micron foil and the automatic splicing at line speeds of the machine on the unwind and rewind sections.
Together with the persistent efforts of the Hybrid Automation team and Afripack engineering and operational staff, the project was a resounding success – an achievement that is indicative of local technical ability.
| Tel: | +27 31 573 2795 |
| Email: | [email protected] |
| www: | www.hybridautomation.co.za |
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