The blow film extrusion is a very sensitive process Many faults can occur that have direct effects on the product, the film. A sensitive measurement and control system, on which extreme demands are posed, are used to reach uniform widths and thicknesses. With the aid of the preassembled energy supply systems, it safely accomplishes its tasks and provides the required quality – at the same time with high cost advantages.
"When an automatic blow film extrusion plant starts up anywhere in the world, it is highly probable that it is equipped with the width and thickness measuring devices of our company," tells General Manager Peter Bünter, who manages the purchase and production departments of the Kündig Control Systems, a division of the HCH. KÜNDIG & CIE. AG. The family concern based at Rüti near Zurich has been developing new solutions for the measuring of films all the time for over 30 years.
Energy supply systems from igus® have been in use in the measuring systems of the Swiss supplier for at least 15 years. "Originally we assembled every chain, from individual link to cable, ourselves, but now we've been using preassembled e-chains® for the last six years," reports Peter Bünter. They are marketed by igus® under the name "readychain®".
Film products have advanced strongly in recent years. New materials and compositions came to the market; they should all be monitored during the production. The devices from Kündig Control Systems, which display measured data immediately, form the basis for ensuring the fault-free production of the blown films. This not only enhances the film quality, but also reduces wastage. In the process large quantities of valuable raw materials can be saved. Around 40 highly qualified experts, engineers and technicians work for the company. They build and develop the high-value measuring systems in a hall area of 2,500 m². "98% of our products are exported abroad. We have much more than 4,000 measuring systems in use worldwide," explains Peter Bünter. A wide range of multi-sided width and thickness measuring systems is available to the users. Additional equipment displays the measured data or prepares them for further evaluations like corrections in the production process.
"The more the raw material prices increase, the stronger our representation is in the market," explains Peter Bünter.
Compact measurement and control system with preassembled energy supply systems.
Whether packaging films for medicines or the food industry, whether insulation material for agricultural or building purposes, trash sacks for household or office, transparent folders: the range for films is immense. "Our measurement and control system is a pure niche product. There exist only a few suppliers worldwide who are specialized in this subject," says Peter Bünter.
The requirements in the industry have considerably changed in the course of the years. "Whereas we previously required a lot of space due to the use of hanging cables, we build much more compact facilities today. The preassembled energy supply system mounted on the side is embedded in an aluminum rotating assembly and rotates very slowly around the film. The e-chain® thereby reaches the turning point at 180°," explains the general manager. The primary objective is the precise measurement. That's why the system moves extremely slowly. It is adjusted to the process that requires ease, or else failures and/or production errors can occur.
The requirements on the measuring system and energy supply system are extremely high in the blow film extrusion. The entire process cannot simply be halted or stopped. As a rule, the equipment is in operation round the clock, 360 days a year. In addition there is heat and oily and dirty air. The energy supply system is only used for measuring the thickness. Measurements in the µ range are carried out with this capacity system, reports Peter Bünter.
Measurement and control system with preassembled energy supply systems. Despite the slow speed, the cables are stressed by the constantly varying train movements.
The Kündig measurement and control systems have adapted to the increasing sizes of the blown film lines. "At present we offer six different models, but require only two preassembled energy supply systems, each designed for the longest way," explains the general manager. Both chains have a maximum length of 5.25 m in the version turned by 90°, mounted on the side, or 3.8 m in the horizontal version.
There is sufficient space in the rotating assembly. The surplus segments do not disturb in the smaller options, they simply travel farther backwards. "Due to the restriction to two systems we could further reduce the costs. In addition we have lower handling and logistics costs," itemizes Peter Bünter. As only two orders have to be given in addition, the potential for errors decreases.
But more costs can be saved. Previously the radial limit cam had to be beveled for each individual chain link in order to be able to travel the defined reverse bend. Even though this resulted in a harmonious movement, the elaborate finishing could not be retained in the course of economic efficiency. Today every tenth chain link is turned by 180° and a small part is beveled, before it is once again reconnected to the standard chain. "Even though the reverse travel is not harmoniously round any longer, the complete solution works, is economical and efficient," summarizes Andreas Voelkel, CEO of igus® Schweiz GmbH. "Here we took up an idea from Kündig and jointly implemented it. “
The chain has a maximum length of 5.25 m for rotational movement, and a maximum length of 3.8 m for horizontal applications.
The preassembled energy supply systems are supplied in the "readychain®" standard system as a customized solution. These are simply assembled e-chain systems® with inserted cables, all plug connections, labeled and with defined projecting lengths according to customers' specifications. "We don't carry out an entry control, but trust the igus® protocol attached to each product," comments Peter Bünter.
"In case of repairs for our older measurement technology for the blow film extrusion, we incidentally assemble the energy supply systems ourselves; the oldest plant runs without problems since 1993. Compared to the present, this does not pay off at all. Due to the preassembly, we save sums of three digits per system. Everything speaks for the part to be bought!"
The energy supply systems of E2/mini system are used. The chain can be easily opened. The cables are inserted and not drawn in. In this way they can not only be assembled at a low price, but also quickly replaced when they are damaged. A data and a control cable from the "chainflex®" range (cables specially meant for the use in e-chains®) top off the overall solution. Despite the slow movement, the cables are stressed due to the continuous length alterations resulting from the s-shaped motion and the resulting permanently changing push-pull forces. "Initially we equipped the energy supply systems with cables from another manufacturer, but always had the problem of corkscrewing and the resulting system failures," recollects Peter Bünter. "We don't have any more problems since we started using the chain-suitable igus® cables."
The laid "chainflex®" cables specially intended for e-chains® are easy to identify.
"We are so satisfied with the collaboration that we use other products as well from igus®," says Peter Bünter. A measuring device that can carry out combined width and thickness measurements, has been developed for sometime now. For the linear executed travels, Kündig decided on the linear technology from igus®. This product is for instance intended to counter radioactive measurement devices. The device will be presented at the "K" fair in Dusseldorf this year.
On the one hand the advantage of Kündig's measurement and control system is its high quality. On the other hand every system can be customized to the respective extrusion line. "With our low vertical range of manufacture, we have always strongly counted on reliable suppliers. With the help of preassembled energy supply systems we are able to hold our position against international competition. As our measurement and control systems are used worldwide, we initially had to be 100% sure that they also operate reliably. But the positive experiences of recent years confirm our decision to use them for technical and economic reasons," Peter Bünter takes stock in conclusion.
Peter Bünter (left), Andreas Voelkel (right) with preassembled energy supply systems, which are in stock ready to be installed, before the test run can start.