The necessity to produce high quality materials, the increase of process speed and productivity as well as the need of flexibility of the plant have led to a very significant technical evolution in the manufacturing process of high precision calenders for plastic materials.
Nowadays the utilization of rolls made of forged steel with induction hardened surface is consolidated. This material has a higher structural stiffness with respect to the traditional cast iron rolls. Consequently, with the same face length, it is possible to foresee a smaller diameter, giving the best production quality, a better control of the rolling bank under lamination and lower energy consumptions. The temperature control of the roll surface is always adjusted by means of thermal oil circulation inside the peripheral drillings. The position of the peripheral drills has been considerably optimized for a most accurate fluid distribution. For very high accuracy temperature needs, OUR PARTNER has available a “patented” design preventing temperature variations along the surface of the rolls.
OUR PARTNER has developed a fully hydraulic “position” gap adjustment control with a very accurate precision granting a position repeatability +/- 2μm and a bearing block position accuracy +/- 5μm. All this achieved with an emergency opening speed of 10 mm/sec and an operative adjustment speed of 1 mm/sec.
The calender frames must support big stresses caused by the material under process between the rolls and they are subject to deformation when under load. The frame deformation related to the value of the separating forces between the rolls can cause errors in the product thickness. OUR PARTNER utilize FEM (finite element method) analysis for calender side frame engineering. The frames are manufactured using a material having a high elasticity modulus. The steel sheet fabricated construction system with proper stiffening ribs adopted, together with the heat treatment foreseen grants the maximum rigidity together with the absence of distortions and vibrations. This constructive solution adopted by OUR PARTNER allows the side frames to act only as supporting elements without interfering to the adjustment devices: as a matter of fact, all mechanical components are simply fixed to the frames. Beside the possibility of easy adjustment and optimization of all mechanical components in the effective process conditions, a very easy maintenance handling is also achieved.
Since for marketing needs, it is necessary to process quite different products, it becomes mandatory to provide the calender with finishing rolls having different surfaces suitable for various products, for example polished rolls or matt rolls. A quick change system of the finishing rolls is available to be applied to all type of plastics calenders both L and inverted L type.
The stripper and stretching unit is composed of many rolls of small diameter with high thermal exchange efficiency, all heated and driven, located at short distances from each others and from the exit roll of the calender.
With this system the product conditions, such as temperature variations and stretching consistency between calender and wind-up stand are accurately controlled: this gives outstanding advantages as far as sheet flatness and very limited transversal shrinking are concerned. Furthermore a productivity improvement can be achieved with lower energy consumption. In order to grant a very efficient and high heat exchange, the stripper and stretching rolls are manufactured with peripheral drillings. The stripper and stretching unit, designed and manufactured by OUR PARTNER, in addition to the above mentioned advantages, gives many valuable advantages at the installation, operation and maintenance of the line. In fact, with respect to the traditional configuration near the calender in fixed position, the unit is composed of a sliding wagon on which all the driving devices, the sliding and the temperature fluid media connections are fitted. Different solutions (less or more automatized) are available for the quick change of the embossing roll and for cleaning of take-off rolls during production. The embossing unit, normally provided with the stripper and stretching rolls, can be manufactured in a particular foldaway solution. When it is not utilized for the production, this unit is parked in a zone below the working area. (inverted L calender). Different diameters of embossing rolls can be installed and quick change of embossing and rubber can be provided
The embossing unit, normally provided with the stripper and stretching rolls, can be manufactured in a particular foldaway solution. When it is not utilized for the production, this unit is parked in a zone below the working area. (inverted L calender).
Different diameters of embossing rolls can be installed and quick change of embossing and rubber can be provided
The first two take-off rolls of the sheet located immediately after the embossing section are with peripheral drillings and they are installed in such a way to lead the sheet always allowing an adequate wrapping on the embossing roll whichever its diameter is. In fact a rotating movement, combined with a longitudinal movement, allows the best positioning of the two take-off rolls. At the same time a constant and continuous control on the product is granted since these rolls are at a very small distance between them as well as with respect to the following cooling drums
OUR PARTNER cooperates with the major European producers specialized in the manufacture of automatic wind-up units developing several technical alternatives with the purpose to integrate different robotized solutions for the drawing, weighing and packing of the calendered roller. As an alternative or addition to the described wind-up units, cutting plate systems are also available according to the production process.
Since the functionality of the calendering line depends on the level and quality of the electric-electronic equipment, OUR PARTNER , together with the major producers of electric and control equipment, produce hardware and software systems for the management of a modern plastic calendering line where it is possible to reach the highest sophistication and integration as far as the control and supervision level is concerned. The control and supervision system is also integrated with a thickness gauge system manufactured by reliable suppliers.
OUR PARTNER is in a position to manage complete “turn-key” projects supplying engineering and technological know-how services suitable for the required production process.
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