DD200078A1 - DEVICE FOR CONTROLLING EXTRUSION SYSTEMS - Google Patents

Abstract

The invention relates to a device for controlling extrusion lines for blown film production. The object of the invention is to ensure the production of blown films of a certain width and depth as well as the required mechanical and optical quality with varying raw material properties, resulting in the object of a device for stable automatic control of extrusion lines for blown film production The apparatus includes a coordinator that secures the flow of information to the other elements and the information processing in them according to a chosen control program (startup, normal operation, change of product range). In normal operation, on the one hand, a controller network for film width and thickness is effective, on the other hand, an adaptation system for a raw material code is activated. The latter system includes a measured value acquisition unit, in particular for determining a global quality characteristic for essential mechanical and optical properties of the film. In the adaptation system, this quality characteristic is checked for remaining in a tolerance band, if the raw material index is corrected when the strip is damaged, extruder optimum values (temperature profile, screw speed, cooling air flow rate) are determined by an optimum value search system and transmitted via an output unit to the corresponding control module. The device according to the invention can be used to control all conventional extrusion lines for blown film production, to systems with outside air cooling and to systems with combined outside / inside air cooling.

Description

Device for controlling extrusion plants

Field of application of the invention

The invention relates to a device for controlling extrusion lines for blown film production with outdoor or combined outdoor / indoor air cooling.

Characteristic of the known technical solutions

Known are control devices for extrusion lines for the production of blown film, the automatic sub-processes such as controlling the width and thickness of the blown film, controlling the temperature profile of the extruder, controlling the melt quality over viscosity-dependent parameters, controlling the screw speed in the extruder and controlling the height of the Calibration basket, its degree of filling and the Abzugsgeachveneitigkeit the successor device as well as the self-starting and reversing from one operating point to. Others (Author collective: Computer-controlled '·' · Extrusion? VDI-Verlag, Dusseldorf 1976 5 Recker ,, H .. ua: Λ Measurement-control-rules in plastics processing, Plastverarbeiter 28 (1977), Se 1-8, 81 ~ 86, 137 - H2; DE-AS-2721609 dated 09.11.1978; author collective: Extrusionsblasformen «, VDI-Verlag, Dusseldorf 1979). Thus, a quality production of blown film is possible, provided that the raw material properties and the consequent heating and cooling conditions are not met

to change. With greater fluctuations in the properties of the raw materials, the regulation of the melt quality does not lead to the required film quality.

It is known that with the conventional control devices for extrusion lines for blown film production important quality properties of the film are not continuously measured directly or indirectly. As such quality features of the film a number of mechanical and optical properties such as tensile strength longitudinal and transverse, elongation at break and crosswise, block behavior, sliding behavior and turbidity are considered »For the majority of these sizes are missing corresponding, continuously operating measuring devices.

Control devices for extrusion lines for blown film production in compliance with the film quality both in terms of geometric dimensions and mechanical and optical properties under variable raw material properties without additional manual intervention have not been shown.

Object of the invention

The invention is based on the aim to ensure the production of blown films of certain width and thickness and required mechanical and optical quality with variable raw material properties ».

.Development of the essence of the invention

Technical problem, which is solved by the invention

The invention is based on the object of representing a device for stable automatic control of extrusion systems for blown film production with external or combined external / internal air cooling, which, with variable raw material quality, requires a required, geometric, mecha ·

niche and optical parameters comprehensive film quality with reasonable accuracy guaranteed.

Features of the invention *

 According to the invention, the device for controlling extrusion lines for blown film production contains the following elements: input unit, coordinator, measured value detection unit, feed value processing unit, comparator, register, controller network, optical data search system with data memory, output units, switching units and control modules,

According to the inventive concept, the structure of the elements mentioned below is realized in the device.

An input unit for selecting and starting a control program, in particular for startup, normal operation or assortment conversion, and another input unit for initial information, such as raw material quality, system identifier, film type and arithmetic constant, are connected to the coordinator, which controls the information flow and information processing within the apparatus hedged in a certain order according to the chosen operating regime.

When selecting the start control program, the coordinator is once coupled via the register and, on the other hand, directly to the optimum value search system, which interacts with the data memory. The register is displayed with a raw cutoff number in the embodiment to follow. The optimum value search system determines from the initial information both the optimum values for the temperature profile of the extruder including the mold, the extruder screw speed and the total cooling air throughput of the extrusion system as well as the initial setting values for the drawing speed and the height and

the diameter of the calibration basket in Außen / Innenluftkühlaystemen .. To the Optiinalwertsuchsystom an output unit for the determined optimal and initial values are coupled and thereon, parallel to each other, puncture chains of switching unit and actuator assembly over which the above-mentioned values are acting,

When selecting the control program normal operation of the coordinator is once with the controller composite for film width and thickness especially for setpoint adjustment, on the other with an adaptation system for the raw material index, consisting of · the puncture chain data acquisition unit, Meßwertverarbeitungseinheit j comparator, register, optimum value search system with data storage, output unit, switching unit and actuator assembly, coupled. By the adaptation system, a global quality characteristic, for essential mechanical and optical properties of the film under consideration of the dynamics of the extrusion process is determined, checked for remaining in an adjustable tolerance band and exceeding or falling below this tolerance band, the raw material index in the register by one unit in terms of Elimination of deviation changed. Then new optimal values for the temperature profile, the screw speed and the said cooling air flow rate of the extrusion system are determined and output. The comparator is coupled to the governor assembly which locks the adaptation system to prevent instability when the pole width or thickness deviates from its nominal value by a specified amount.

When selecting the control program assortment redistribution, the coordinator is once with the control group · for film width and thickness, in particular for setpoint adjustment, on the other hand, after disabling the adaptation system for the raw material code, with the punctuation chain from optimum value search system including data memory, output unit,

Switching unit and control module coupled. By means of said functional chain, the optimum values for the temperature profile, the screw speed and the total cooling air throughput of the extrusion installation are determined and output from the newly entered initial information.

The measured value acquisition unit contains in particular

- a height measuring device for the frost line or

a temperature measuring device for the film surface temperature after completion of the freezing process or a size dependent thereon or

a measuring device for the bubble shape with processing of the measured values into a form factor

for recording the global quality characteristic for essential mechanical and optical properties of the film.

embodiment

The invention will be explained in more detail with reference to an embodiment according to attached sketch. The sketch contains the following positions:

1t 2, 3 - Input unit 4 - Coordinator 5 - Data acquisition unit 6 - Measurement processing unit 7 - Comparator 8th - Register 9 - Controller network • 10 - Optimal value search system 11 ' - "Datastore" · 12, 13 - Output unit 14, 15 - Switching unit 16, 17, 18 - Control module

The object is an extrusion line for the production of blown film based on the principle of outside air cooling. The to

/ - do » % gp 6 *« ^ ^ a?

Control of this system serving device according to the invention between the levels of the input units 1, 2, 3 and switching unit s 14, 15 can be realized by a process computer or a microcomputer. The computer used will be loaded with all the necessary procedures, calculation equations and data for realizing the puncture of coordinator 4, measured value processing unit 6, comparator 7, register 8, controller network 9 _S optimum value search system 10 and output units 12 and 13. The measured variables are polled cyclically in the measured value acquisition unit 5 and pass through A / D converters. unless they are already in a suitably coded form.

The function of the device requires that in addition to film width and thickness in particular a global quality parameter Q for essential mechanical and optical properties of the film and a raw material quality, determinable by technological studies class number are processed to control commands. In particular, the height of the freezing zone, the film surface temperature after completion of the freezing process or a size dependent thereon, or a shape factor characterizing the shape of the bubbles, have proven to be a global characteristic of the tensile strength, the elongation at break, the blocking behavior, the sliding behavior and the haze of the film. On the other hand, Q must be continuously measurable and, on the other hand, calculable from process data by means of a model equation obtained by process analysis for a specific plant. The required film quality is outlined by a region determined from the permissible value range of the film features, for the upper limit Qq _{0 of which} a further model equation of the process must exist. With proven dependence of the parameter Q on the extruder screw speed, the equation

Q ~ Q _Go = 0 U)

the objective function for optimizing this screw speed and thus the output power. In addition, the setting values of the optimum temperature profile have to be compared with the

Temperature zones of the extruder including mold and the optimal cooling air flow from process data can be calculated by IJodellgleichungen.

After setting the control program start via the input unit 1, the initial information (class number of the raw material, index of the system, index of the film type to be produced, target width and target thickness of the film and a calculation constant c for the equation (^ X-)) on the input unit 2 provided. At program start the machine bunker are opened in a fixed time sequence, the auxiliary energy for heating or cooling of the temperature zones of the extruder including mold, the operation of the extruder screw, the Kühlluftgeblaees and the trigger device including rewinder switched (actuator assembly 18). After loading the register 8 with the class number of the raw material, the optimum value search system 10 in conjunction with the data memory 11 from the present initial information determines the Einstellverwert the optimal temperature profile over the temperature zones of the extruder including forming tools Then, the calculation of the optimal set value of the extruder screw speed on the basis of the objective function ( The setting is then read by the output unit 13 via the changeover units H and 15 controlled by the coordinator 4 to the required position as pulses to the control modules 16 and 17 .ausgegeben. The description is an embodiment variant. is used as the basis for which the pulse duration expresses the change from the actual value of the setting values (incremental output). This requires a feedback of the actual values in the device. After exiting the melt from the tool-ring gap, the mass is manually drawn into the flax-laying and squeezing device with simultaneous cooling, and the film tube is thereby inflated. In addition, the deduction rate is increased. The inflation of the

Polienschlauches and increasing the withdrawal speed is carried out by the input unit 3 by adjusting pulses of any duration, for the duration of the intervention, the switching unit 14 is controlled in the required position. The starting process is completed when the film width and thickness are adjusted to their target value and the film web is inserted in the rewinder »

After setting the control program normal operation with the input unit 1 and program start is on the elements Meßwerterfassungseinheit 5, measured value processing unit 6, controller assembly 9 »output unit 12, ümschalteinheit I4 and actuator assembly 16 (working on the principle of sampling) composite control of film width and thickness made effective in the In order to suppress high-frequency stochastic disturbances, a digital filtering takes place in the measured-value processing unit β. In the case of width control, the control action is known to be made by changes in the quantity of supporting air; the withdrawal speed. Disturbing influences of the coupled control loops are reduced by the thickness control loop is locked within the unit 9 when the width deviation from the target value has exceeded a predetermined amount. For the invention, it is essential that the device has the global quality parameter Q of the film at its disposal (determination via measured value acquisition unit 5 and measured value processing unit 6). _E The measurement result is kept in the comparator 7 in a tolerance band. / >, ...

Q _Go -c <Q ^ Q _{00 +} c <**)

where c is a domain value following the class width of the raw material in the physical unit of Q. If this condition is violated, the raw material class number in Register 8 will be one unit in the sense

31603 7

an elimination of the deviation changed. In a defined sequence, new optimizers for the temperature profile, the screw speed (target function (# -)) and the cooling air inlet of the extrusion plant are determined. The dynamics of the extrusion process - in particular the time behavior between Q and the temperature profile - is taken into account by measuring Q in a time-quantized manner as a moving averaged value determined over a defined period of time using the measuring cycle and a weighting factor. Depending on the dynamics of the extrusion process, the cooling air flow is also changed. For the incremental output of all set values by the output units 12 and 13 to the actuator assemblies 16, the coordinator 4 has controlled the switching units 14 and 15 to the required position. The described adaptation system for the class number of the raw material is locked for reasons of stability for the period in which the width or thickness of the foil deviate from its nominal value by a fixed amount.

After setting the control program Assortment changeover via input unit 1, entering the changed initial information (unit 2) and program start, the adaptation system for the raw off-class number is disabled. In parallel with the composite control of film width and thickness, the optimal values for the temperature profile, the screw speed (target function (.) *)) And the cooling air flow of the extrusion system are determined by the optimal value search system 10 and incrementally fed to the control module by the output unit 13 in a defined sequence 17 spent. The ISn 'switching units 14 and 15 remain in the assumed in normal operation .Stellung. The change in the cooling air flow is dependent on the dynamics of the extrusion process. After the process has settled, the assortment redistribution is completed,

After setting the control program Shut down via the

Input θ inhe ΐ and program start are closed in a fixed time sequence of the machine bunker and the auxiliary power for heating or cooling of the temperature zones of the extruder including mold, the operation of the extruder screw, the cooling air blower and the trigger device including rewinder shut down (actuator assembly 18). Furthermore, compound control and adaptation system are locked.

After setting the manual program control program via the input unit 1 and program start, the composite control and the sampling system are disabled. ' The actuator assemblies 16 and 17 can then be operated directly by means of the input unit 3 by adjusting pulses of any duration, including the switching units 14 and 15 are controlled in the required position «

Claims (2)

invention claim 1. Apparatus for controlling Sxtrusionsanlagen for blown film production with outdoor or combined outdoor / indoor air cooling, characterized in that the input unit (1) for selecting and start a control program especially for startup, the hormonal operation or the range conversion and the input unit ( 2) are connected to the coordinator (4) for initial information such as raw material quality, equipment identifier, type of film and calculation constants, which ensures the information flow and the information processing within the apparatus in a specific sequence according to the operating regime selected and the - is coupled once during start-up via the register (8) to be loaded with a raw material index, and secondly directly to the optional value-finding system (10) which interacts with the data memory (11), which both optimizes the optimum temperature profile of the extruder including the mold , the extruder neck speed and the total cooling air flow rate of the extrusion line as well as the initial set values for the take-off speed and the height and diameter of the calibration basket in outdoor / Innenluftkühlsyateinen from the initial information and determined by the output unit (13) via the switching units (H) and (15) • is in communication with the control modules (16) and (17), whereby the fourth said are suitably active in a suitable form, the optimum values in a Steigungsgrippe (17), 'the initial values in a wertere Stell.-.- · assembly (16) . - In normal operation, once with the controller network (9) for film width and thickness in particular for setpoint adjustment, on the other hand with a from Meßwerterfassungseinheit (5), measured value processing unit (6), comparison <* η _< _ _> MS »% SP β * 0 \ 0 ν &> W rather (7), register (8), optimum value search system (10) with data memory (11), output unit (13), switching unit (15) and actuator assembly (17) is coupled to the Rohst offkennzahl existing adaptation system, whereby a global quality parameter for essential mechanical and optical properties of the film is determined taking into account the dynamics of the extrusion process, checked for remaining within an adjustable tolerance band and if the tolerance exceeds or falls below the tolerance band the register content is changed by one unit in order to eliminate the deviation and new optimum values for the temperature of il, the Sehneckendrehzahl and d.en total cooling air flow rate of Sxtrusionsanlage determined and output, and a connection between the controller assembly (9) and the comparator (7), which locks the adaptation system at specified setpoint deviations of film width and thickness to avoid instability . - When AssetsUmstellung once with the controller network (9) in particular for setpoint adjustment, on the other, after locking the adaptation system with the optimum value search system (10) including data memory (11), output unit (13), switching unit (15) and actuator assembly (17) is coupled , which in turn determines and outputs the optimum values for the temperature profile, the screw speed and the total cooling air throughput of the extrusion plant from the newly entered initial information ». · 2 »Device- according to item 1, characterized in that the measured value detection unit (5) in particular - a height measuring device for the frost line or a Temperaturraeßvorrichtung for the film surface temperature after completion of the freezing process or a dependent size or - A measuring device for the bubble shape with processing of the measured values to a form factor contains for detecting dec global quality parameter for significant mechanical and optical film properties. For this a page drawings