NL8902778A - METHOD FOR MANUFACTURING TUBES AND PROFILES FROM THERMOPLASTIC PLASTIC MASSES - Google Patents

Description

Method for manufacturing pipes and profiles from thermoplastic plastic materials.

The invention relates to a method for manufacturing pipes and profiles from thermoplastic plastic materials, wherein these materials are extruded through an extrusion gap, in whose environment the temperature is controlled, and then through a calibration mold in the area of a cooling zone for calibration. be moved there.

In previously known similar processes, the wall thickness of the extruded tube or the extruded profile is controlled by changing the temperature in the region of the extrusion gap. The extruded profile or tube is then applied in a calibration form against its cooled inner surfaces by an underpressure generated in the area of the inner walls or, for hollow profiles, by an overpressure generated in the interior of the profile, and thus the external shape of the profile is calibrated. .

The object of the invention is now to propose a method of the type indicated in the preamble, in which the predetermined wall thickness of an extruded profile can be manufactured more accurately than hitherto.

According to the invention, this is achieved in that the change in the wall thickness of the pipe or the profile, which adjusts in accordance with a temperature change in the region of the calibration mold, and the temperature is controlled in dependence on the measured cohesion and the predetermined desired wall thickness, wherein the temperature in the region of the calibration mold in the cooling zone is regulated sector-wise separated from each other in the circumferential direction of these extending ranges, respectively sectors.

The cooling of the calibrating mold, which differs in circumferential areas, results in a differently rapid stiffening of the extruded profile, with a greater wall thickness being created at a constant production speed of the extruded profile or tube in those areas in which less cooling takes place. This is due to the fact that in these areas even more plastic material can adhere to the already further stiffened and thus tougher layer, which is in direct contact with the cooled wall of the calibration mold. By this course of the method it is possible to produce profiles, in particular hollow profiles, with a wall thickness corresponding substantially to the desired value.

For example, experiments have shown that a change in the temperature of the wall of the calibration mold in individual parts or sectors of this by about 40 ° C allows a change in the wall thickness by about 10%. In addition, a wall temperature of the calibration mold can be maintained, for example, between 10 * and 50 ° C, with the latter values still showing a sufficient cooling effect.

A further advantage of the method according to the invention also lies in the fact that in the tool or in the region of the extrusion gap, there is usually no possibility of a forced cooling and the area of the extrusion gap formed precisely by this region of the extrusion gap extruded profile can form a thickened place. Also in this case, by correspondingly influencing the temperature of the wall of the calibration mold in this region, the wall thickness can be influenced accordingly and thus corrected.

In the known methods, the calibration mold is cooled in its entirety, which usually takes place via a central water supply, at which no tempering is used. This creates yet another drawback, namely that the temperature fluctuations of the cooling water cause fluctuations in the wall thickness. These problems can also be easily avoided by the method according to the invention, according to which the temperature of the wall of the calibration mold is regulated in stages.

According to a further feature of the invention, provision can be made for the change in the wall thickness of the pipe or the profile, which is dependent on a temperature change in the region of the extrusion gap, and the temperature in the region of the extrusion gap, measured measured consistency and the predetermined desired wall thickness is additionally controlled in the circumferential control of the cooling in the area of the calibration mold in separate circumferential ranges of the extrusion gap.

This measure also allows an influence in the sense of a locally limited change in the wall thickness of the extruded profile or of the tube. The change in the temperature in the individual trajectories of the extrusion gap results in a change in the sliding conditions in the individual sectors and thus also in a change in the mass flow, i.e. its distribution and thus also in a change in the outgoing volume per unit of time, that is to say its distribution over the circumference of the profile, which is decisive for the wall thickness.

Experiments have shown that also in the heating of the individual parts of the extrusion gap a variation range of about 40 ° is available, the temperature in the area of the extrusion gap with most thermoplastic masses in the range between about 90 ° C to 230 ° C and this variation range allows for a change of the wall thickness of approximately 10% with a uniform cooling over the circumference of the calibration mold. Therefore, in combination with the variation of the temperature of the cooled circumferential mold, a very far-reaching possibility arises to influence the wall thickness in individual circumferential parts or sectors of the extruded profile or the extruded tube.

Furthermore, it can also be ensured that the production speed of the extruded tube or the profile is controlled depending on the distribution of the wall thicknesses in the area of the calibration mold. The average wall thickness distribution can be measured by measuring in the area of the calibration mold.

By changing the production speed, a change in the average wall thickness or the wall thickness distribution can be achieved in a very simple manner, without the control range of the temperature in the individual temperatures available for compensating for wall thickness fluctuations along the circumference of the profile. parts or sectors is limited.

These process steps can also be combined with each other. Thus, through a combination of the separate temperature control in the individual circumferential parts of the calibration mold with the control of the production speed, the advantage arises that a very far-reaching centering is easily attainable even if the fluctuations of the wall thickness of the extruded profile are caused by fluctuations. be determined in the operating state of the calibrator, such as pressure and temperature, etc.

By combining all three of the above options, relatively large deviations from the desired wall thickness can be compensated. Thus, the wall thickness increases with an increase in the temperature in the extrusion gap, whereas an increase in the temperature in the calibration mold leads to a decrease in the wall thickness. If a place of greater thickness now occurs in the extruded profile and the temperature in the extrusion gap can no longer be lowered further, a corresponding centering can be achieved by increasing the temperature in the corresponding region of the calibration mold.

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It is particularly advantageous if the wall thickness measurement of the pipe or profile takes place in the area of the calibration mold, preferably in separate sectors, around the circumference of the pipe or profile.

As a result, the wall thickness can be measured with the extensively extruded extruded profile or of the tube and a very far-reaching maintenance of the predetermined wall thickness can be achieved, whereby both by changing the temperature distribution in the calibration form and in the area of the extrusion gap on the wall thickness. influence can be exerted on the extruded profile or the tube. This creates a very wide control area.

Moreover, this also considerably reduces the dead time which occurs due to the production speed and the distance of the exit from the extrusion gap to the measuring site. In this way, the wall thickness is still measured in that area in which a further formation takes place, whereby reactions to variations in the wall thickness can be reacted very quickly and, therefore, even at high requirements for the constancy of the wall thickness over the circumference of the extruded profile. whether there is only little rejection of the pipe.

A particularly high degree of accuracy of the maintenance of predetermined wall thicknesses can be achieved if the measurement of the wall thicknesses in the individual sectors of the circumference of the profile or of the pipe in the circumferential direction takes place oscillatingly or by optical measurement of the cross-section and individual values an average value for the corresponding sector is calculated.

By circumferentially oscillating measurement of the wall thickness, it is not only measured along a line in every sector or every path, but practically the wall thickness distribution over the entire sector and, consequently, over the entire circumference.

With an optical measurement of the cross-section, the knowledge of the wall thickness distribution can be carried out quickly and accurately without contact.

Furthermore, provision can be made for the wall thickness in the area of the extrusion gap and of the calibration mold to be in separate circumferential parts or. sectors of the circumference of the pipe or profile are measured separately and, from these data, the temperature in the individual sectors of the extrusion gap and the calibration shape are controlled on the basis of these values, the parts resp. sectors of the calibration mold are preferably aligned with those of the extruder slit.

Due to this measure, any deviations from the desired wall thickness can be corrected quickly and reliably.

Furthermore, it can be ensured that the regulation of the temperature of the individual parts resp. sectors of the calibration form by controlling the area of a heat carrier resp. cooling medium takes place.

Thus, the temperature of the individual parts of the calibration mold can be controlled with very little effort.

A further object of the invention is to propose an apparatus for applying the method according to the invention.

Starting from a device, which has a calibration form, after the extrusion body formed after an extrusion slit formed by an outflow body or by a mandrel body, the outflow opening of which is preferably divided into a number of sectors with heating devices separately controllable in terms of their heating capacity, the inner walls of which determining the extruded pipe or of the extruded profile and being temperable by means of a tempering device and including a wall thickness measuring device, it is therefore proposed that the inner wall of the calibration mold be in circumferentially adjacent parts resp. sectors which are thermally decoupled from each other, the tempering devices being controllable independently of the individual sectors or sections.

These measures make it possible in a simple manner to cool the individual circumferential parts differently.

From a constructional point of view, a particularly simple solution arises when the individual parts resp. Tempering devices allocated to sectors have chambers through which a tempering medium flows, which chambers have a wall common to the inner wall of the calibration mold, the flow of the tempering medium through each chamber being controllable by means of separately controllable control valves.

In this way, it is possible to suffice in the device with the aid of an essentially constant temperature cooling medium, for instance water. Nor is it necessary to ensure a special constancy of the temperature of the cooling medium, but temperature fluctuations occurring with a central water supply can be readily accepted.

According to a further feature of the invention, provision can be made for the wall thickness measuring device to be arranged in the region of the calibration mold and in the individual parts or. sectors of the inner wall of the calibration mold are provided with temperature sensors, which, like the wall thickness measuring devices and the control valves, are connected to a control circuit comprising a processor.

These measures allow a rapid correction of incipient deviations of the wall thickness from the predetermined set value, since the knowledge of the deviation takes place practically in situ and therefore only very small dead times occur during the control. This is in fact only determined by the thermal inertia of the calibration mold, which can, however, be kept relatively small.

Furthermore, it is also possible, in spite of the thermal decoupling of the individual sectors or circumferential parts of the calibration mold - the sectors can be separated by air gaps and closed only in the region of the inner wall of the calibration mold or completely separated by thermal insulation. given influence of the edge zones, since a temperature change in a peripheral part also influences the edge zone of the neighboring parts. This influence can be discounted by means of the processor.

Furthermore, in a device for manufacturing plastic pipes, it can be provided that the wall thickness measuring device is formed by a number of sensors placed in a ring, the ring being pivotable (oscillating) by an angle value corresponding to a sector of the inner wall of the calibration mold. .

By these measures it is possible to know the wall thickness practically over the entire contour and to control incipient deviations in the wall thickness by correspondingly changing the temperature of the corresponding sector of the calibration mold and / or of the extrusion gap.

Furthermore, it can also be ensured that the extrusion gap is likewise in its circumferential direction mutually adjacent parts resp. sectors which are thermally decoupled from one another and to which separately controllable heating devices are allocated and the extrusion gap and the calibration form are thermally decoupled from each other, respectively. by means of an air gap or a thermal insulation arranged between them, preferably the controllable parts or parts which can be separated in their temperature. sectors of the calibration form and of the extrusion gap are aligned with each other.

This makes it possible to independently control the temperature of the individual circumferential parts of both the extrusion gap and of the calibration mold, which allows an influence on the wall thickness of the extruded profile or the extruded tube within wide limits.

In this connection it is advantageous if in the individual parts resp. sectors of the extrusion gap thermo probes are provided, which are connected to the control circuit and which are connected to the individual parts resp. sectors of the calibration form which are individually and independently controllable by means of actuators actuated by the control circuit.

This makes it possible to use closed loops for controlling the temperature of the individual peripheral parts of the extrusion gap and of the calibration mold. In addition, the processor also allows consideration of the influence of the temperature variation of an adjacent portion on the edge regions of the adjacent portions of the calibration mold and of the extrusion gap.

Furthermore, these measures create the advantage that options are available between different business situations. Thus, the control of the correction of the wall thickness of the extruded profile can only be effected by influencing the individual circumferential parts of the calibration mold, or, however, an additional influencing of the temperature distribution via individual circumferential parts or sectors of the extrusion gap can be applied. In this way it is still possible to correct thicker places in the extruded profile when the temperature in the extrusion gap can no longer be lowered. In this case, in the corresponding portion of the calibration mold corresponding to the respective peripheral portion of the extrusion slit, the temperature of which can no longer be raised, the temperature must be increased. Likewise, at thin locations, upon reaching the maximum temperature in the extrusion gap, the temperature in the corresponding region of the calibration mold can be lowered, thereby correcting the thin location.

Variations in thickness occurring over the entire circumference of the extruded profile can be compensated for by corresponding changes in the production speed.

The invention will now be explained in more detail with reference to the drawing. Show:

Fig. 1 schematically a device according to the invention,

Fig. 2 and 3 schematic spatial illustrations of two embodiments of a device according to the invention,

Fig. ή and 5 a longitudinal and cross section through the extrusion gap of a device according to the invention,

Fig. 6 to 8 operating diagrams of the method according to the invention, and

Fig. 9 and 10 cross sections through the calibrator.

The device according to the invention according to Fig. 1 comprises an extrusion tool 30, the extrusion slit 3 of which in several peripheral parts resp. sectors 4, which are separately controllable in terms of temperature.

Separated from this extrusion tool by an air gap 16 serving for the thermal decoupling, a calibration mold 1 is provided, on the inner wall of which the extruded profile or the extruded tube is cooled and fixed in this form and also in circumferential parts resp. sectors 2 is subdivided, which in terms of their temperature can be controlled substantially independently of each other.

At the end of the calibration mold 1, a wall thickness measuring device 5 is placed, which measures the wall thickness of the extruded profile or the extruded tube by means of ultrasound. However, provision may also be made to use resistance measuring devices both in the area of the extrusion tool 30 and in the area of the calibration mold 1, the signals of which are processed in the control circuit 12.

A further conveyor 41 for the already cooled profile or the cooled tube is provided, which is essentially formed by the conveyor belts 42 encircling substantially synchronously running conveyor belts 42, which engage on its outer surface distributed over the circumference of the extruded tube and connect it via remove friction grip. The drives of the conveyor belts 42 are controlled via the control unit 43, which in turn receives the control signals from the control circuit 12.

The control circuit 12 receives signals from the wall thickness measuring device 5 and from the temperature sensors 17 and, apart from the control unit 43 of the conveying device 41, controls the heating devices 60 arranged in the sectors 4 of the extrusion tool 30, which, as shown in FIGS. 4 and 5 it appears, if heating rods are designed. Furthermore, the control circuit 12 also controls a tempering device 8, which, as can be seen from Fig. 2, controls the flow of a tempering medium through chambers arranged in the sectors 2 of the calibration mold 1 by means of control valves 10. Further temperature sensors 11 are provided in the sectors 2 of the calibration form 1, which also supply signals to the control circuit 12.

In the embodiment of the device according to the invention according to Fig. 2, which is intended for the manufacture of pipes, the wall thickness measuring device is formed by a number of sensors 14, not shown further, for example ultrasonic measuring heads, which are arranged in a ring 13 are included. This ring is pivotable in the direction of the double arrow 15 over a circumferential angle over which a sector always extends, so that the measurement of the wall thickness can take place over the entire circumference. These measured values are averaged in the control circuit via the associated sector 2.

The embodiment according to Fig. 3, which is intended for the production of non-round profiles, differs from that according to Fig. 2 only in that both the extrusion tool 30 and the calibration mold 1 are connected in circumferential parts 4 and 4 respectively. 2 is subdivided, which, like the sectors 4 and the sectors 2 according to Fig. 2, are thermally decoupled from each other, the decoupling being made by corresponding cuts, into which insulating material can be inserted under certain circumstances.

It can furthermore be noted in FIGS. 2 and 3 that the air gap 16 for the thermal decoupling of the extrusion tool 30 of the calibration mold 1 is exaggeratedly large for reasons of better clarity.

Fig. 4 shows on an enlarged scale a section through the outer jacket of the extrusion tool 30, which are subdivided into sectors 4 by associated cuts, which are largely thermally uncoupled from the cuts and which are heatable by two heating elements 6 each. The heating power can be individually and independently regulated for each segment 4, the heating power being controlled by the control circuit 12 taking place.

Furthermore, in each of the sectors 4 of the extrusion tool 30, a temperature sensor 17 is provided, which is connected to the control circuit 12.

As can be seen from Fig. 5, the heating elements 6 run substantially in the longitudinal direction of the extrusion tool, the temperature sensors 17 being built radially.

Fig. 9 shows a cross-section through the calibration mold 1 according to FIG. 3. Also in this calibration mold 1, the individual parts 2 which are adjacent to each other in the circumferential direction are thermally uncoupled from each other by corresponding cuts. In addition, in the regions of the walls 7 of the mold that come into direct contact with the extruded profile, chambers 9 are passed through a tempering medium, so that the temperature of the walls 7 in contact with the extruded profile can be controlled accordingly.

In the walls 7 that come into contact with the extruded profile, temperature sensors 11 are provided, which are connected to the control circuit 12. The temperature of the chambers 9 »which can flow through the tempering medium separately and independently of each other is controlled by the control circuit 12 via the tempering device 8.

Fig. 10 shows a cross section through a calibration mold according to FIG. 2 intended for the manufacture of pipes. This calibration form also has circumferentially adjacent chambers 9, which are flowed through a tempering medium and which are independently controllable in terms of their temperature. For this purpose, the flow through the individual chambers 9 is controlled by means of control valves 10. The number and the arrangement of the chambers, which at the same time form the sectors 2 of the calibration mold 1, has been chosen such that, relative to the sectors of the extrusion tool, respectively. its extrusion slit 13 are aligned.

In the wall or in contact with the extruded tube. walls 7, a temperature sensor 11 is arranged in each of the sectors 2, all of which are connected to the control circuit.

The operating modes possible with the device according to the invention are shown in the flow charts according to FIGS. 6 to 8.

Fig. 6 shows a flow chart for the thermal centering using the control of the temperature in the extrusion slit.

The results Si of the measurement of the wall thicknesses in the individual circumferential sections Ui of the extruded profile are averaged for the calculation of the average wall thickness S (3th of the entire profile and for the determination of the difference of the measured minimum value Smin and maximum values Smax In this case, particularly for pipes, the values Si may refer to a sector of average values.

If the value Smin is not within a certain tolerance range around a predetermined value S limit, the discharge speed is changed accordingly and the run through of the scheme is restarted from the beginning.

If the value Smin is within the tolerance range and therefore the discharge speed remains constant, the location resp. the portion of the circumference Uk, where the value Smin occurs, is located and the necessary temperature increase T for increasing the wall thickness to the predetermined desired value S desired for the corresponding circumferential portion 4 (circumferential portion Uk) of the extruder slit 3 is calculated.

It is then checked whether a predetermined maximum temperature T limit should be exceeded. This value T limit depends on the material to be processed and is approximately 230 ° C for the materials usually used.

Should such an overshoot be necessary for centering, an alarm is triggered to trigger pre-centering manually.

If the temperature required for centering is below this value, the calculated temperature increase T is carried out in the corresponding circumferential section 4 of the extruding gap.

Subsequently, the wall thicknesses are again measured and checked whether the actually measured difference Smax - Smin of the wall thickness is below a predetermined difference value. If this is the case, the control phase has ended, if not, the entire control loop is run through again.

This adjustment mechanism brings both the average wall thickness closer to the desired value and the local wall thickness distribution is compensated.

Fig. 7 shows a flow chart for the thermal centering of the wall thickness using the calibration mold together with the drain control.

According to this scheme, the discharge rate is controlled in the same manner as according to the flow chart of Fig. 6.

After setting the discharge speed, that circumferential part or sector Uk is determined, in which the maximum wall thickness Smax occurs and the temperature increase T necessary for achieving the desired wall thickness in this region is calculated in that given chamber 9 of the calibration form 1, which temperature of the peripheral portion or sector 2 forming this portion of the extruded profile.

In a subsequent step it is checked whether the temperature in this peripheral part or that sector 2 of the calibration mold 1 should be increased to a value above T limit (e.g. 50 ° C) for this purpose. In this case, an alarm is given which can initiate pre-centering of the device manually.

If this is not the case, the temperature increase T is now carried out in said chamber 9 of the calibration mold 1, which determines the temperature of the circumferential section Uk.

Subsequently, in accordance with Fig. 6, the difference between the maximum and minimum wall thickness over the circumference of the extruded profile is again determined and checked whether it is below a predetermined limit value. If this is the case, the control process is ended, if not, the described loop is run through again.

Fig. 8 shows a flow chart for thermal centering of the wall thickness of any extruded profile using the calibration mold and the extruding tool along with the discharge rate control.

The flow chart consists of two parts, the first of which essentially corresponds to the flow of fig. 6 and the second of which essentially corresponds to that of fig.

The discharge speed is set in the same way as in fig. 6 and 7 ·

The first part of the control corresponds to the run-through according to fig. 6, with the difference that no alarm is given if the temperature increase T in the extruder nozzle is necessary, which would exceed the predetermined limit value T limit (eg 220 ° C). , but first of all this temperature limit value is set in this circumferential part 4 of the extruding slit 3. Then in the second part further control takes place with the aid of the temperature setting in the calibration form as in Fig. 7.

To this end, the wall thicknesses are again measured, Smidden, Smax, Smin, and Smax - Smin, and it is checked whether the minimum wall thickness Smin is outside the tolerance range. If this is the case, branching is carried out at the very beginning of the first section and Smin is corrected by the discharge control. If not, the maximum wall thickness is subsequently located, as in Fig. 7 ». Subsequently, the temperature increase T2 necessary for reducing the difference between the maximum and the minimum values Smax, Smin of the wall thickness T2 is calculated in the circumferential part 2 of the calibration form 1, in which the maximum wall thickness occurs.

In a subsequent step, it is checked whether the temperature in this peripheral part 2 should be raised above T limit 2 (e.g. 50 ° C). In this case, an alarm is triggered, which initiates pre-centering by hand. If this is not the case, the temperature in the chamber 9 of this peripheral section 2 is increased accordingly. Subsequently, as in Fig. 7, it is again checked whether the current difference between the maximum and the minimum wall thickness is below a predetermined limit value or not.

In the first case, the control is completed, in the second, the bottom loop for the discharge control and the thermal centering is run again from the first wall thickness measurement using the calibration nozzle.

Claims (13)

1. A method for manufacturing pipes and profiles from thermoplastic plastics masses, these masses being squeezed out through an extruder, in whose region the temperature is controlled, and then passed through a calibration mold in the region of a cooling zone for calibration, with characterized in that the change in the wall thickness of the pipe or the profile, which adjusts depending on a temperature change in the area of the calibration mold, and the temperature is controlled in dependence on the measured relationship and the predetermined desired wall thickness, the temperature in the area of the calibration mold in the cooling zone partially separated from one another in portions or circumferentially extending therefrom sectors is regulated. Method according to claim 1, characterized in that the change in the wall thickness of the pipe or the profile, depending on a temperature change in the area of the extrusion gap, is also measured and the temperature in the area of the extrusion gap is measured depending on the measured and the predetermined desired wall thickness in addition to the partial control of the cooling in the area of the calibration mold in separate circumferential sections of the extrusion slit is controlled. Method according to claim 1 or 2, characterized in that the discharge speed of the extruded tube or the extruded profile is controlled in the area of the calibration mold depending on the wall thickness distribution. The method according to any one of claims 1 to 3, characterized in that the wall thickness measurement of the pipe or profile takes place in the region of the calibration form, preferably in separate sectors over the circumference of the pipe or profile. Method according to claim H, characterized in that the measurement of the wall thickness in the individual sectors over the circumference of the profile or of the pipe in the circumferential direction oscillates or by optical measurement of the cross-section and an average value from the individual values is calculated for the corresponding sector. Method according to any one of claims 1 to 5, characterized in that the wall thickness in the area of the extrusion gap and of the calibration mold is measured separately in separate sectors over the circumference of the pipe or profile and from these data the temperature in the individual sectors of the extrusion slit of the calibration mold is controlled according to these values, the parts resp. sectors of the calibration form preferably align with those of the extrusion slit. Method according to any one of claims 1 to 6, characterized in that the temperature control of the individual parts or. sectors of the calibration form by controlling the flow rate of a heat transfer medium or medium having an essentially constant feed temperature. cooling medium takes place. Apparatus for applying the method according to any one of claims 1 to 7, comprising an extrusion slit formed on a nozzle or mandrel body, the nozzle of which, preferably in a number of sectors, has separately controllable heating devices in terms of their heating capacity subdivided, downstream calibration form, the inner walls of which determine the outer shape of the extruded tube or the extruded profile and can be tempered by means of a tempering device, and contain a measuring device for the wall thickness, characterized in that the inner wall of the calibration mold (1) in circumferentially adjacent parts (2) resp. is divided into sectors which are thermally decoupled from each other, with tempering devices which can be controlled independently of each other being added to the individual sectors or parts (2). Device according to claim 8, characterized in that the individual parts resp. sectors (2) containing tempering devices, chambers (9) flowed through a tempering medium, which have a wall common to the inner wall of the calibration mold (1), the flow of the tempering medium through each chamber (9) by means of separately controllable control valves (10) can be controlled. Device according to claim 8 or 9, characterized in that the wall thickness measuring device (5) is arranged in the region of the calibration mold (1) and in the individual parts or. sectors of the inner wall of the calibration mold (1) are provided with temperature sensors (11), which are also connected, such as the wall thickness measuring device (5) and the control valves (10), to a control circuit (12) containing a processor. Device according to claim 10, for the manufacture of pipes, characterized in that the wall thickness measuring device (5) is formed by a number of sensors (14) arranged in a ring (13), the ring being over one with a sector of the inner wall of the calibration mold (7) corresponding perimeter angle, can be oscillated in an oscillating manner. Device according to any one of claims 8 to 11, characterized in that the extruding slit (3) is also divided into parts or. sectors (4) which are adjacent in their circumferential direction are subdivided, which are thermally decoupled from each other and to which separately controllable heating devices (6) are added and that the extruding gap (3) and the calibration mold (1) are thermally decoupled from one another, for example by means of an air gap (16) or by a thermal insulation inserted between the two. Device according to any one of claims 8 to 12, characterized in that the extruding slit (3) is also divided into parts or. sectors (4) which are adjacent in their circumferential direction are subdivided, which are thermally decoupled from each other and to which separately controllable heating devices (6) are added, wherein the temperature-controllable parts or parts, respectively. sectors of the calibration mold (1) and of the extruder slit (3) are aligned with each other. Device according to any one of claims 8 to 13, characterized in that in the separate parts resp. sectors (4) of the extruding slit (3) are fitted with thermo sensors (17), which are connected to the control circuit (12) and which are connected to the individual parts or sectors (4) of the calibration form (1) have been added, which can be individually and independently controlled by means of adjusting devices (8) actuated by the control circuit.