Ice cube bags: Toppits on the outside, ice cold on the inside
Tear off, fill with water, turn the bag over - tight. After a few hours of being subjected to temperatures below freezing, you will hear the chinking sound when the finished ice falls into your glass. Ice cube bags are the modern alternative to the conventional plastic moulds. In the course of product improvements, the Melitta subsidiary Cofresco Frischhalteprodukte GmbH & Co. KG has cooperated with Falk Steuerungssysteme GmbH in the complete modernisation of the production machines which exist at its Minden location as the new bag design resulted in significant changes having to be made to the process.
Two processes are decisive when manufacturing ice cube bags: welding and perforating. Both of these production steps are clocked – i.e. discontinuous. Contrary to this, the unwinding of the raw foil and the later winding up of the finished ice cube bags run continuously. The transition is solved by means of an intermediate buffer which also ensures that the machine can continue to produce without stopping when the machine is subjected to a roll change.
The printed foil is fed to the first buffer in two layers via the unwinder. The downstream taking-in cylinder provides the required force. The winder itself runs without an own drive and merely provides a defined resistance which is required for the required web tension. The second buffer is supplied from the first buffer before the foil finally reaches the welding device. Both of the foil webs are sealed together, herby creating the pattern for the ice cubes which are produced later. Cofresco makes it as easy as possible for the customers. In the next step, the bags are perforated so that they can be torn off the handy roll. The machine achieves 50 cycles per minute. As this is a seasonal product for the warmest time of the year, it is able to work around the clock if necessary.
As far as Friedrich Niedernolte, the Head of the electrical maintenance department at Cofresco is concerned, both availability in multi-shift operation and the high production speed were decisive parameters when it came to retrofitting the existing plants. The aim of the retrofitting was not only to adapt the processes to the new design of the ice cube bags, but also to increase the usability. The Master Electrician emphasized that “Our employees have to be able to operate the machine fast, safely and intuitively“. As the Head of the electrical repairs department, he also pays special attention to maintenance friendliness and the possibilities of making changes when changing products, aside from the ongoing production operation.
Article from mpa magazine
document download (pdf, german)