DE4013611A1 - Process to eliminate thickness errors in wound plastics foil - Google Patents

Abstract

A process for producing plastic foil and winding it onto a coil comprising measurement of foil thickness across it's breadth such that positive or negative thickness error signals are fedback to adjust the foil thickness produced. This foil is then wound onto the coil to produce a coil with the required cylindrical profile. The error signals are fedback via a computer which then controls the produced foil thickness such that the foil is thickened or thinned between the thicker and thinner areas in proportion to the correction signal from the computer. The foil is then wound onto the coil until it achieves the desired cylindrical shape. This process is then repeated until the complete coil has been wound precisely to the required cylindrical shape.

Description

The invention relates to a method for producing a Plastic film and for winding the plastic film to a coil, the plastic film being produced over their width a thickness error profile with systematic Dic kenplus errors and systematic minus thickness errors points, and wherein the thickness error profile when winding affects the plastic film to the coil and at least at the end of the winding process a coil with sufficient ge exact cylinder contour is generated. The expressions systema table thickness plus errors or systematic thickness minus errors denote those thickness errors which are systembe things, for example based on tool tolerances. They are inevitable and easily appear in the cross sectional profile of the plastic film produced, namely in the stationary, retracted state of the corresponding Plant for the production of the plastic film always on same place. No special measures will be implemented light, these systematic thickness errors add up when winding up to the coil z. B. to positive or ne negative barrel tires.

In the process known from practice (PatG § 3 (1)), An addition is attempted from which the invention is based to avoid the thickness error in that the thickness mistake Profile across the width of the plastic film, as it were is moved so that when winding instead of the Dic error addition occurs an error distribution, namely such that the coil of disruptive effects from Winding up clearly added thickness errors result, is practically free. The thickness errors are rather from Layer to layer at another location in the coil. To this  to achieve, is in the manufacture of so-called Blown films, which are initially a thermoplastic Hose created, this inflated to the tubular film and the tubular film is laid flat, either the blow head with the hose extrusion tool in a mostly periodically rotating motion offset and / or it becomes the so-called flat laying device accordingly periodically moved. It is expensive and often not fully in terms of the effect achieved satisfactory because the coil annoying bumps when also no pronounced barrel tires, can show. To the To achieve the described error distribution, it is with Working with wide-slit nozzles, the measure of Dic to reduce errors, i.e. the thickness error profile to level, as it were, initially in accordance with the measured thickness error profile by adjusting the gap width of the slot die. Also the superposition and Distribution of wanted singular thickness errors is in known in this context. Although this can be done known measures to narrow the thickness tolerances, it however, there remains an annoying thickness error profile with disturbing render error addition in the coil.

With much higher accuracy in relation to the A cylinder contour reached at the end works at who no longer distributes errors (DE 40 00 530.5, PatG § 3 (2)). Here can move on everyone Components and units described in the above serve known measures of error distribution, to be dispensed with, in terms of machine technology means a significant simplification. This method is characterized in that the thickness error profile  of the plastic film produced with its systematic Thickness plus errors and / or minus thickness errors before opening wrap the plastic film to the coil is measured that a number of n layers of those with the systematic thicknesses plus errors and / or minus thickness errors produced Plastic film is wound into the coil, where n = 1 or 1, and after that a number of layers of Plastic film with inverse thickness error profile on the Coil is wound - and so on, alternately with layers of plastic film with thickness error profile and other layers with inverse thickness error profile, until on End the coil with a sufficiently precise cylinder contour is wrapped. This process leads to a coil very precise cylinder contour, in which the individual layers of the plastic film very firm and practical void-free and therefore without air pockets on each other lie. This is particularly the case with thin plastic films significant.

The invention is based on the problem, the beginning to perform the described method so that when winding the plastic film by supporting film layers in the Coil on thickness areas of particularly influenced thickness Plastic film the coil with a very precise cylinder contour arises.

A solution to this task works with positive legs flow of the thickness in the plastic film. This solution is characterized in that the thickness error profile is measured and the error areas with thickness plus errors determined that thereafter in the areas between the error areas with thickness plus errors the thickness of the Plastic film at least in one area as required  the thickness plus error is increased, and that this art as long as material film with increased thickness is wound up until the coil forms one has a sufficiently cylindrical contour - and so on with iteration of the described process steps, until at the end the coil with a sufficiently precise cylinder contour is generated.

Another solution to this task works with negative ones Influencing the thickness in the plastic film. This Lö solution is characterized in that the thickness error pro fil is measured and the error areas with minus thickness errors are determined that thereafter in the areas between between the error areas with minus thickness errors the thickness at least in one area according to the thickness minus error is reduced, and that this plastic film with a reduced thickness in some areas until the coil that forms is sufficiently cylin has a drilled contour - and so on with iteration of the process steps described until the coil ends is generated with a sufficiently precise cylinder contour.

Another solution to the object of the invention combined the two procedures described above. they is characterized in that the process alternates according to claim 1 or the method according to patent saying 2 is carried out.

Within the scope of the invention, the thickness error profile of the Plastic film immediately as well as before winding up Coil can be measured. In the context of the invention, this can Thickness error profile of the plastic film but also indirectly  due to the deviation of the contour of the coil being formed be measured from the given cylinder contour, whereby the thickness of the plastic according to this deviation lie in the areas between the error areas with Dic kenplus errors or minus thickness errors increased or is reduced. It is within the scope of the invention Measurement of the thickness error profile on the plastic film and to combine the contour measurement, taking both measurements be fed to a computer and according to one desired optimization can be weighted.

Experience has shown that the thickness error profile of an art fabric film several thickness plus defects and also several thicknesses minus error on. So far, the areas between Defect areas with thickness plus errors or thickness minus errors spoken. The method according to the invention can can be realized analogously, if exceptionally an art fabric film only a systematic thickness over its width plus error or only a systematic minus thickness error having.

The thickness measurements can be within the scope of the invention can be done in different ways. With immediate Thickness measurement on the plastic film can be transmitted tion measuring devices are worked. With indirect Measurement of the thickness profile of the plastic film by contour Measurement on the coil can be carried out using a laser beam len are performed using a laser beam scan can be practiced. You can also use me here mechanical scanning of the contour of the coil being formed work. In any case, the thickness profile of the plastic foil with the tools of modern measurement technology  instinctively without difficulty. How be The determined thickness error profile is already mentioned immediately and / or the determined contour to a computer abandoned who is programmed to describe the bene positive or negative influence on the plastic lie in the latitude between the error areas leads. The calculator can easily take into account that the length of the individual layers when winding a Coils increases from layer to layer. For optimal results one comes when the thickness error profile is measured very precisely sen and accordingly also the gap width of the plant stuff is adjusted. There are various measures for this known (see. DE 34 27 912, DE 34 27 915, DE 35 30 383).

If you work according to the teachings of the invention, it is so no longer required at the beginning of the Technique described an error distribution to make. In particular, with a fixed tool, from which the plastic film indirectly or directly steps to be worked. Specifically, this means that one No rotation of the blow head during the production of blown film more is needed. In the version for the manufacturer blown film, with a film tube first testifies and this laid flat in a flat laying device the invention teaches that the film tube in a fixed lay flat lay flat and then immediately, if necessary after cutting the folded edges, fed to the coil and wound up there. In the out management form for the production of so-called flat foils With the aid of a slot die, the invention teaches that the flat film immediately, without any measure error distribution to which the coil is fed.

Claims (8)

1. A method for producing a plastic film and for winding the plastic film into a coil, the plastic film produced having a thickness error profile with systematic thickness plus errors and systematic thickness minus errors over its width, and wherein the thickness error profile influences the winding of the plastic film into the coil and at least at the end of Winding process a coil is generated with a sufficiently precise cylinder contour, characterized in that the thickness error profile is measured and the range of errors with thickness plus errors are determined, that the thickness of the plastic film is then at least in a subarea according to the in the areas between the error areas with thicknesses plus errors Thickness plus error is increased, and that this plastic film is wound up with increased thickness in some areas until the coil that forms has a sufficiently cylindrical contour, and so on with iteration of the described process steps until at the end the coil is generated with a sufficiently precise cylinder contour. 2. Process for producing a plastic film as well for winding the plastic film into a coil, whereby the plastic film produced a Dic across its width Core error profile with systematic plus thickness errors and systematic thickness minus errors, and wherein the Thickness error profile when winding up the plastic film for Coil influenced and at least at the end of the winding process creates a coil with a sufficiently precise cylinder contour is characterized in that  the thickness error profile is measured and the error correction che with minus thickness errors are determined that after that in the areas between the defect areas with thicknesses minus the thickness at least in a partial area Provided the minus thickness error is reduced, and that this plastic film with reduced thickness in some areas until the coil that forms is one has a sufficiently cylindrical contour, and so on with iteration of the described process steps, until at the end the coil with a sufficiently precise cylinder contour is generated. 3. The method according to claims 1 and 2, characterized records that alternately the method of claim 1 or the method according to claim 2 is carried out. 4. The method according to any one of claims 1 to 3, characterized characterized that the thickness error profile of the plastic foil immediately as well as before winding into the coil will. 5. The method according to any one of claims 1 to 3, characterized characterized that the thickness error profile of the plastic indirectly through the deviation of the contour of the film forming coils measured from the specified cylinder contour sen and the thickness of the Plastic film in the areas between the trouble shooting enlarge with thickness plus profile or thickness minus profile ßers or shrinks. 6. The method according to any one of claims 1 to 5, characterized characterized in that with a fixed tool from which the plastic film or a preliminary product emerges is tested.   7. The method according to any one of claims 1 to 6 in the Aus management form for the production of so-called blow molders lien, whereby first a film tube is produced and this is laid flat in a flat laying device, thereby characterized in that the film tube in a firm flat laying device and then immediately telbar is fed to the coil. 8. The method according to any one of claims 1 to 5 in the Aus management form for the production of so-called flat foils lien with the help of a slot die, characterized records that the flat film is fed directly to the coil becomes.