DD231540A1 - METHOD FOR PRODUCING FOILS - Google Patents

Abstract

The invention relates to a process for producing films on Walzenkalandern any number of rolls with microprocessor-controlled Walzenschraenkung and roll spacing. By including the lead of the first stretching roller as a further control of the control technical effort is reduced and increases the material value of the films while saving material.

Description

TITLE OF THE INVENTION

Process for the production of films

FIELD OF THE INVENTION

The invention relates to a method for producing calendered films with low thickness tolerances.

CHARACTERISTICS OF THE KNOWN TECHNICAL SOLUTIONS

It is known to produce films with Walzenkalandern and to avoid the occurring due to the deflection of the rolls thickness tolerances of the films over the web width roll spacing to use cambered vValzen provide a roll restriction (ax crossing) or to arrange a counter bending device (roll bending). The roll spacing, the roll restriction and the counterbending device can be controlled and readjusted via measuring probes arranged on the film web and a downstream microprocessor.

The disadvantage of all these methods is the residual error which can not be eliminated by this readjustment, since the thickness tolerance exceeds the width of a different function

1-ϋ

follows as the roll correction. Oede change in the roll spacing changes the deflection of the rollers and requires a change in the roll restrictor or the Gegenbiegevorrichtung and vice versa, so that the film thickness constantly oscillates to the optimum. Moreover, although a counterbending device is more advantageous than a roll restrictor, it is very expensive and therefore effective only for multi-roll calenders.

It is according to DE-OS 33 00 251 also known in Mehrwalzenkalandern form at least one of the balzen as deflection and roll to arrange on hydrostatic support elements, with certain diameter ratios of the rollers are to be considered with each other.

This known device is limited in its application exclusively to Mehrwalzenkalander.

OBJECT OF THE INVENTION

The object of the invention is to produce films with small thickness tolerances while avoiding the cited disadvantages with little effort in terms of measurement and control and thus to save material and to increase the utility properties of the films for further processing.

DISCLOSURE OF THE INVENTION OF THE INVENTION

The invention has for its object to develop a method for the production of films with small thickness tolerances, which is in Walzenkalandern any number of rolls, so both Zweiwalzenkalandern and bsi Mehrwalzenkalandern, applicable and using the Walzenschränkung (ax crossing) their residual error compensated.

This object is achieved according to the invention as follows:

Prior to commissioning of the roll calender, depending on recipe, original mass, temperature and roll speed, first the roll constraint and then the waist spacing for a target value of the thickness of the film are set at their upper tolerance limit. The first stretching roller is set to the minimum of its overfeed.

During operation of the roll calender, measuring probes on the film web determine the die tolerance over the web width in a known manner via a three-point measurement or a profile measurement and compare the measurement results with a predetermined profile image. Controlled by a microprocessor, in the evaluation of these measurement results, alternatively, the lead of the first stretching roll is increased and / or the roll restriction and / or the roll spacing is changed.

If the measurement results over the web width are the same, that is, the entire film web is too thick or too thin, the film thickness is controlled only on the leading first stretching roller and thus prevents that caused by changes in the roll restriction or the roll spacing additionally uneven film thicknesses over the web width.

If the measurement results on the web width unequal, so either the web center or the edge region is too thick or too thin, a uniform film thickness is first set on the roll restriction or the roll spacing and then controlled via the leading first stretching roller, the final film thickness.

With the method according to the invention, the object of the invention is fully achieved. By using the lead of the first stretching roller as a third control variable, the change in the roll restriction or the roll spacing only with unequal measurement results on the web width

required. This reduces the technical control effort and simplifies the run of the roller calender. The achievable low thickness tolerances of the films lead to a saving of material and represent an increase in utility of the films for further processing.

Embodiment

The invention will be explained in more detail below using an exemplary embodiment.

To produce a film of PVC with a desired nominal thickness of 150 Aim by the roll melting process, ie on a two-roll calender, a roll restriction of 11 mm and a roll spacing of 150 / μm are also set at the roll edge with a center distance of 150 / μm. The first stretching roll has a lead of 130% over the peel-off roll,

When operating the roller calender, the film web with measuring probes is measured according to the three-point method, ie in the center of the cream and at the 8-tooth edges. Via an associated microprocessor these measurement results are compared with a predetermined profile image and triggered derived from this comparison control pulses.

Are the results on. The web width equal and the film thickness over the web width is due to the adjustment of the roll restriction and the roll distance total of the desired nominal thickness of 150 / um _t so only the lead of the first stretching roll is increased so far, as a result of the case incoming stretching process match the measurement results with the desired nominal thickness.

If the measurement results on the web width unequal and the film is thicker or thinner in the middle than in the edge regions, then the microprocessor by appropriate control pulses first a change in the roll restriction or the roll spacing and then, if the measurement results on the web width are the same again , the regulation of the advance of the first stretching roller to the agreement of the measurement results with the desired nominal thickness.

Claims (2)

CLAIM THE INVENTION 1. A process for the production of films on Walzenkalandern any number of rolls with W / alzenschränkung and adjustable roll spacing, which are separated by probes on the film web and a microprocessor and / or jointly controllable and nachregelbar, characterized that before commissioning of the roll calender depending on recipe, original mass, temperature and Walzeng.eschwindigkeit first the roll restriction and then the roll spacing set for a target thickness of the film at the upper tolerance limit and the first stretching roller is set to the minimum of their overfeed and the Operation of the roll calender Measuring probes on the film web via a three-point measurement or a profile measurement in a known manner determine the thickness tolerance over the web width, compared with a predetermined profile image and controllable via a microprocessor alternatively increases the lead of the first stretching roller and / or the roll restriction and / or the roll spacing is changed. 2, Method according to claim 1,
characterized by that with the same measurement results over the web width, the film thickness is controlled only by the leading first stretching roll « Method according to claim 1, characterized by in the case of unequal measurement results over the web width, the film thickness is controlled first via the roll restriction and / or the idle-axis spacing and then via the leading first stretching roll *