Technology for monitoring an extruder or respectively an injection moulding machine

Abstract

A measurement system for monitoring an extruder or an injection moulding machine in operation, with a measurement device that generates a radar wave signal and emits it in the extruder or in the injection moulding machine, and detects a response signal corresponding to the emitted radar wave signal; and an evaluation device, that determines a run time t, phase shift and/or intensity change I of the radar wave signal on the basis of the detected response signal, and determines at least one operating parameter of the extruder or of the injection moulding machine on the basis of the determined run time t, phase shift and/or intensity change I of the radar wave signal, wherein the operating parameter points to a wear state of the extruder) or of the injection moulding machine. Further, a corresponding method and an extruder and an injection moulding machine with such a measurement system.

Claims

1. A method for monitoring an extruder which is in operation or an injection moulding machine which is in operation, wherein the method comprises the following steps: emitting a radar wave signal in the extruder or in the injection moulding machine; detecting a response signal corresponding to the emitted radar wave signal; determining a run time Dt, phase shift Df and/or intensity change DI of the radar wave signal on the basis of the detected response signal; and determining at least one operating parameter on the basis of the determined run time Dt, phase shift Df and/or intensity change DI of the radar wave signal, wherein the operating parameter points to a wear state of the extruder or of the injection moulding machine, a melting state and/or a material composition of a material which is received in the extruder or in the injection moulding machine and which is to be processed.

2. The method according to claim 1, wherein the radar wave signal in the extruder or in the injection moulding machine is emitted at several positions arranged spaced apart from one another in axial direction and/or radial direction, and wherein for each position the response signal is detected and an operating parameter is determined on the basis of the response signal.

3. The method according to claim 1, wherein as response signal a reflection component or a transmission component of the irradiated radar wave signal is detected.

4. The method according to claim 1, wherein the radar wave signal is emitted at a predetermined angle to an extrusion direction.

5. The method according to claim 1, wherein the radar wave signal is a continuous or pulsed radar signal.

6. The method according to claim 1, wherein the emitted radar wave signal has at least a frequency in the range between 30 GHZ and 300 GHZ.

7. The method according to claim 1, wherein as operating parameter the refraction index n of the material which is to be processed is determined form the determined run time Dt, phase shift Df and/or intensity change DI.

8. The method according to claim 7, wherein from the determined refraction index n by means of at least one refraction index model the material composition and/or the phase state of the material which is to be processed is determined.

9. The method according to claim 1, wherein as operating parameter a distance datum D is determined from the determined run time Dt, phase shift Df and/or intensity change DI.

10. The method according to claim 9, wherein from the distance information D by means of a model describing the extruder or the injection moulding machine, the wear state of the extruder or of the injection moulding machine is determined.

11. A measurement system, which is designed for monitoring an extruder or an injection moulding machine in operation, comprising: a measurement device, which is designed to generate a radar wave signal and to emit it in the extruder or in the injection moulding machine, and to detect a response signal corresponding to the emitted radar wave signal; and an evaluation device, which is designed to determine a run time Dt, phase shift Df and/or intensity change DI of the radar wave signal on the basis of the detected response signal, and to determine at least one operating parameter of the extruder or of the injection moulding machine on the basis of the determined run time Dt, phase shift Df and/or intensity change DI of the radar wave signal, wherein the operating parameter points to a wear state of the extruder or of the injection moulding machine, to a melting state and/or to a material composition of a material which is received in the extruder or in the injection moulding machine and which is to be processed.

12. The measurement system according to claim 11, wherein the measurement device comprises at least one transmitter for generating the at least one radar wave signal at the at least one measurement position, and at least one receiver for detecting a response signal corresponding to the radar wave signal.

13. The measurement system according to claim 11, wherein the measurement device is designed to emit and detect radar waves in the range between 30 GHZ to 300 GHZ.

14. The measurement system according to claim 11, wherein the evaluation device is designed to determine a refraction index of the material which is received in the extruder or in the injection moulding machine and which is to be processed, on the basis of the detected run time Dt, phase shift Df and/or intensity change DI, and to determine the phase state and/or the material composition of the material by means of a predetermined refraction index model.

15. The measurement system according to claim 11, wherein the evaluation device is designed to determine distances between components of the extruder or of the injection moulding machine on the basis of the detected run time Dt, phase shift Df and/or intensity change DI, and to determine the wear state of the extruder or of the injection moulding machine by means of a predetermined model.

16. The measurement system according to claim 11, further comprising a memory device, which is designed to store at least one refraction index model and/or a model describing the extruder or the injection moulding machine, or parameters.

17. An extruder, comprising the measurement system according to claim 11.

18. An injection moulding machine, comprising the measurement system claim 11.

Description

[0032] Further details and advantages of the invention will emerge with the aid of the following drawings, which represent implementations of the present invention. There are shown:

[0033] FIG. 1 a block diagram, which illustrates diagrammatically a measurement system for monitoring the operating state of an extruder or of an injection moulding machine according to the present invention;

[0034] FIG. 2 a screw extruder, at which the measurement system shown in FIG. 1 is implemented by way of example;

[0035] FIG. 3 a flow diagram, which illustrates a method for monitoring the operating state of an extruder or of an injection moulding machine;

[0036] FIG. 4a-4c an implementation of the method according to FIG. 3; and

[0037] FIG. 5 a further implementation of the method according to FIG. 3.

[0038] In connection with FIG. 1 a measurement system 100 for monitoring the operation of an extruder or of an injection moulding machine according to the present invention is described further.

[0039] The measurement system 100 comprises a measurement device 120 and an evaluation device 140. When the measurement device 120 and evaluation device 140 are configured as separate units, the measurement system 100 can have in addition a (wired or wireless) interface 130, via which the devices 120, 140 communicate with one another. For example, the measurement device 120 can be arranged directly in an extruder or in an injection moulding machine, whereas the evaluation device is implemented in a computer arranged externally to the extruder or to the injection moulding machine. In FIG. 1 the communication interface is indicated by a dashed line. The transfer of measurement data from the measurement device 120 to the evaluation device 140 is indicated by an arrow.

[0040] The measurement device 120 shown in FIG. 1 comprises at least one transmitter Tx 122 and at least one associated receiver Rx 124. In FIG. 1 by way of example respectively one transmitter 122 and receiver 124 are illustrated. It shall be understood that the measurement device 120 can also have two or more transmitters 122 and associated receivers 124. In addition, the separately configured transmitter 122 and receiver 124 in FIG. 1 can also be configured in the form of transceivers. The at least one transmitter and receiver 122, 124 can be arranged at or in an extruder or injection moulding machine which is to be monitored, as is explained more closely further below in connection with FIG. 2. In addition, the measurement device 120 comprises a signal processing 126.

[0041] The at least one transmitter 122 of the measurement device 120 is designed to generate pulsed or continuous radar wave signals and to emit these to the material which is to be extruded (see also FIG. 2). The generated radar wave signals of each transmitter 122 can have at least a frequency in the range between 30 GHz to 300 GHz. The at least one receiver 124 is designed for the detection of the response signal generated through the material to be extruded and/or extrusion components or injection moulding components. The response signal can be the transmitted radar wave signal component (in transmission measurement) or the reflected radar wave signal component (in reflection measurement).

[0042] The signal processing unit 126 can be designed to determine from the detected response signals signal parameters such as run time t, intensity change I and/or phase shift of the radar wave signal. This takes place through comparison of the response signal with the emitted radar wave signal. The signal parameters determined by the signal processing unit can then be transferred (in the form of digital data) to the evaluation device 140. Alternatively hereto, the functionalities of the signal processing unit can be implemented in the calculating unit 142 of the evaluation device 140. In other words, according to an implementation deviating from FIG. 1, the signal processing unit 126 can also be part of the calculating unit 142 to the evaluation device 140.

[0043] The calculating unit 142 comprises at least one processor or integrated switching circuit. The calculating unit 142 is designed to determine at least one operating parameter on the basis of the determined signal run time t, intensity change I and/or phase shift . As is described in further detail in connection with FIGS. 3 to 5, from these operating parameters a conclusion can be drawn concerning the material composition and/or phase state (melting state) of the material (plastic material) received in the extruder.

[0044] The data memory 144 can be designed to store, briefly and/or in the long-term, the signal parameters determined in real time and the operating parameters determined therefrom. In the data memory 144 in addition models concerning the extruder or the injection moulding machine and/or refraction index models for the materials or respectively material mixtures which are to be extruded can be stored. Such refraction index models are described in greater detail further below in connection with FIGS. 4b and 4c.

[0045] Optionally, the measurement system 100 can further comprise an output device, which is designed to emit, visually and/or acoustically, the results of the calculating unit 142. The output device is not illustrated in FIG. 1. According to a variant, the results of the calculating unit 142 can be displayed on a screen of a computer, smartphone or other electronic device.

[0046] In connection with FIG. 2, an implementation of the measurement system 100 described above in an extruder 10 is described by way of example. The extruder 10 is designed as a single-screw extruder. It shall be understood that the measurement system described here does not depend on the practical configuration of the extruder 10 or of an injection moulding machine, but rather is able to be implemented in any type of extruder (single-screw extruder, double-screw extruder or multi-screw extruder) or injection moulding machine.

[0047] The extruder 10 comprises an extruder housing 12, a nozzle (die) or tool, arranged at the front axial end of the housing 12, at least one extruder screw 16, and a filling device 18. The housing 12 defines a rotationally symmetrical extruder channel 20 with rotation axis 22. In the extruder channel 20 the extruder screw 16 is arranged, which is rotatable about the rotation axis 22. The extruder screw 16 can, for example, be displaceable axially forward and back with respect to the face-side nozzle 14. The rotational movement and translational movement of the screw 16 takes place by a drive device which is arranged on the rear side of the extruder lying opposite the nozzle 14, and which is coupled to the screw 16 (not illustrated in FIG. 2).

[0048] The filling device 18 is coupled to the extruder channel 20. It serves to feed the material or material mixture which is to be extruded (generally plastic material) in the form of pellets or granulate to the extruder channel 20. As can be clearly seen in FIG. 2, the plastic material which is to be extruded is fed to the extruder channel 20 at its end facing away from the nozzle. This extruder region is also named the feed zone. Through the rotation of the screw 16 about the rotation axis 22, the plastic material, which is still initially present in the solid state in the feed zone, is moved in the direction of the nozzle. By heating the plastic material by means of heating elements 24 arranged on the extruder 10 and by friction of the moving plastic material against the screw or respectively against the inner wall of the extruder, the plastic material which is moved in the direction of the nozzle 14 is melted and compacted successively (compression zone or respectively melting zone of the extruder 10) until the plastic material is present in the region of the nozzle 14 (ejection zone of the extruder 14) in the desired plasticized state.

[0049] The measurement system 100 implemented in the extruder 10 comprises a measurement device 120 with a plurality of transceivers (transmitters and receivers 122, 124) which are arranged spaced apart from one another in axial direction of the extruder 10. By the use of several transceivers at different axial positions, the operating state can be monitored in each operating zone of the extruder. The evaluation device 140 of the measurement system 100 is configured separately from the measurement device 120 and is not illustrated further in FIG. 2.

[0050] Each transceiver 122, 124 arranged along the axial direction is in direct electromagnetic coupling with the extruder channel 20 of the extruder 10. A direct electromagnetic coupling is achieved for example by each transceiver 122, 124 being accommodated in the extruder channel 20 or in the extruder housing 12 (e.g. in recesses provided specifically for this on the inner wall of the extruder housing 12). Through the described coupling between transceiver 122, 124 and extruder channel 20 it is achieved that the radar wave signal generated by the transceiver 122, 124 is emitted in a loss-free manner (therefore without shielding) into the extruder channel 20. In FIG. 2 the emission of the radar wave signal into the extruder channel 20 is indicated diagrammatically. Equally, the response signal generated through the ray-penetrated plastic material and/or through reflection on extruder components (e.g. on the extruder screw or on the inner wall of the housing) can be detected by the transceivers 122, 124 without appreciable shielding or influencing by the extruder housing 12. The implementation of the measurement arrangement 100 shown in FIG. 2 measures as response signal the reflected radar wave signal (echo signal) incoming at each transceiver 122, 124. As in the implementation shown in FIG. 2 transceivers are arranged in the ejection zone, compression zone or respectively melting zone and feed zone, each extruder zone can be monitored separately by the described measurement system 100.

[0051] Alternatively to the implementation shown in FIG. 2, the measurement device 120 can also have spatially separate transmitters 122 and receivers 124 arranged lying opposite each other, in order to detect the transmitted radar wave signal as response signal.

[0052] The measurement method for monitoring the operating state of an extruder or injection moulding machine is described further by means of FIG. 3. The method is implemented by the measurement system 100 described in FIGS. 1 and 2.

[0053] In a first step S100 a radar wave signal is generated by means of at least one transmitter 122 and is emitted in an extruder (for example extruder 10) or respectively in an injection moulding machine. The radar wave signal has a predetermined frequency or frequencies. When several transmitters 122 are arranged in the extruder 10 (cf. FIG. 2), then each transmitter 122 emits a corresponding radar wave signal into the extruder channel 20.

[0054] The radar wave emitted by each transmitter 122 propagates through the plastic material which is received in the extruder channel 20 and is to be processed, and interacts with the wave-penetrated plastic material and the extrusion components situated in the propagation direction. For example, each radar wave signal propagating in the extruder channel 20 is reflected on the inner walls of the extruder housing 12 or on the screw surface. In a second step S200, the reflected radar wave signal is detected as a response signal by corresponding receivers 124.

[0055] In a subsequent third step S300, a signal run time t, intensity change I and/or phase shift of the radar wave signal is determined by means of the signal processing unit 126 or calculating unit 142 on the basis of each detected response signal. This takes place through comparison of each emitted radar wave signal (primary signal) with the response signal corresponding thereto, as described further above.

[0056] In a further step S400, at least one operating parameter for the extruder or injection moulding machine is determined by means of the calculating unit 142 on the basis of the determined run time t, phase shift and/or intensity change I of each emitted radar wave signal.

[0057] In connection with FIGS. 4a-4c, an implementation of step S400 is described further. FIG. 4a shows here a flow diagram which shows the determining of the refraction index n of a plastic material, received in the extruder or injection moulding machine and penetrated by radio waves, as operating parameter. It was found namely that the refraction index n of a plurality of plastic materials which can come into use in extrusion and injection moulding methods, changes sufficiently clearly during melting, so that this change becomes measurable with radar waves. It has further been found that the change of the refraction index n of plastic materials caused by a phase change (e.g. on the transition from the solid into the liquid state) is higher by at least one order of magnitude than a change of the refraction index n caused by temperature fluctuations or temperature changes in the material. Therefore, temperature influences on the refraction index can be disregarded. A typical refraction index development during the melting of plastic can be seen in FIG. 4b. The refraction index changes from a refraction index value n3 in the liquid (melted) state to a higher refraction index n4 in the solid (solidified) state. In the melting process, the refraction index lies between the two extreme values n3 and n4 and depends on the respective mixture ratio of solid and liquid phase. When the development of the refraction index n is known at the solid/liquid phase transition, then by measuring the refraction index n, a conclusion can be drawn easily concerning the mixing ratio of melt to solid material.

[0058] In addition, it has been found that the refraction index n of a plastic mixture of several components depends on the concentration of the respective components. FIG. 4c shows diagrammatically the development of the refraction index n of a melted plastic mixture of a component 1 and component 2. When the melt consists of two components which differ from one another measurably in their refraction index n1 and n2, then a conclusion can also be drawn concerning the mixture ratio of the two components 1 and 2 from the development of the refraction index n. This applies to a plurality of common plastic mixtures. This applies in particular to a plurality of foamed or degassed plastics, wherein the refraction index depends on the concentration of the included foaming agent or respectively on the degasification state of the plastic which is to be extruded. Therefore, for example, in the ejection zone of the extruder the material composition of the melt, such as for example the degasification state of the melt, the concentration of foaming agents in the melt or the concentration of other additives, fillers and/or reinforcing materials to be added to the melt, can be determined. As fillers, for example mineral fillers such as for example chalk, or functional fillers, such as for example metal particles, for changing the electrical and/or magnetic characteristics of the material, can come into use. As reinforcing materials, glass fibres, carbon fibres, natural fibres or other fibres can come into use for reinforcing the mechanical characteristics of the material. As additives, for example antioxidants, nucleating agents, dyes or other substances can come into use.

[0059] Back to FIG. 4a. The determining of the refraction index n as operating parameter takes place on the basis of the determined run time t, phase shift and/or intensity change I of the radar wave signal. For example, the refraction index n can be easily extracted from the determined signal run time t, as the signal run time t is indirectly proportional to the signal propagation speed Cm and the path s covered in the extruder channel 20 according to the equation t=s/Cm. As the signal propagation speed Cm in addition depends on the refraction index n of the ray-penetrated plastic material according to the equation Cm=Cv/n, wherein Cv is the refraction index of vacuum, the relationship t=n*s/Cv directly follows. As the refraction index Cv is known, with a known s, the refraction index n can be easily determined.

[0060] In order to determine from the determined refraction index n the material composition or the melting state of a plastic material which is to be processed, a corresponding refraction index model is provided (step 500a). A refraction index model describes the development of the refraction index n of a plastic material mixture as a function of its mixture ratio of melt to solid material (cf. FIG. 4b) and/or as a function of its material composition (cf. FIG. 4c). Such refraction index models can be determined for the respective plastic material mixtures through preliminary tests and stored in the data memory 144. Then, when carrying out the method according to the invention, they merely need to be retrieved through the calculating unit 142, whereby the real time monitoring only becomes possible. Additionally or alternatively hereto, a real time determining of refraction index models is also conceivable. Real time determining means the determining of a refraction index model during an extrusion process. For example, by means of the radar wave measurement technology described here, the refraction index n4 of the solid material present in the feed region of the extruder and the refraction index n3 of the completely melted material present in the ejection region of the extruder can be determined. From the two measured limit values n3 and n4 for the liquid and solid state of the material which is to be extruded, a conclusion can then be drawn concerning any desired mixture of solid and liquid phase in the extruder.

[0061] In the subsequent step S600a, the material composition and/or the melting state of the material which is to be extruded is determined on the basis of the determined refraction index n and the refraction index model. If, for example, the composition of the plastic material is (approximately) known, then the refraction index n depends only on the ratio of melt to solid material of the plastic material which is to be extruded. By means of a refraction index model, as illustrated in FIG. 4c, then with a determined refraction index n the melting state of the plastic material which is to be extruded can be determined. If, on the other hand, the melting state is known, e.g. through evaluation of temperature data which were measured by temperature sensors arranged at the extruder or respectively at the injection moulding machine, the material composition of the plastic material which is to be extruded can be determined by means of a refraction index model, as illustrated in FIG. 4b.

[0062] In connection with FIG. 5, a further implementation of an operating parameter (method step S400 in FIG. 3) is described. In this implementation, the wear state of the extruder 10 or respectively of the injection moulding machine is determined.

[0063] According to a first step S400b, by means of the calculating unit 142 on the basis of the determined run time t, phase shift and/or intensity change I of the radar wave signal, at least one distance information datum between components of the extruder or respectively injection moulding machine is determined. For example, in the extruder 10 shown in FIG. 2, the distance D between the extruder screw 16 and the housing 14 can be determined. This distance can be easily determined from the determined signal run time t of the radar wave signal, because this is proportional to the path s of the radar wave signal which is covered according to the relationship t=n*s/Cv. If the refraction index n of the plastic material which is to be extruded is n, then the covered path s can be determined directly from the measured signal run time t. In the implementation of the measurement device 100 illustrated in FIG. 2, in which the radar wave signal reflected by the screw 16 can be measured as response signal, the distance between screw 16 and extruder housing is precisely half the measured signal path, therefore 0.5*s=D.

[0064] From the determined distance D (distance changes), in a further step S500b the wear of the screw 16 can be estimated.

[0065] The determining of the wear described in connection with FIG. 5 can in particular also be carried out with an emptied extruder or outside the operation of the extruder.

[0066] The technology described here enables, in a flexible and simple manner, the determining of the material composition and of the melting state of a material which is to be extruded. In particular, the method can also be used for determining the wear of extruder components. As the electromagnetic radar waves do not depend on the temperature conditions in the extruder or in the injection moulding machine, the present invention concerns a monitoring technology which is decoupled from temperature influences. In addition, the technology can be used in any desired extruder or injection moulding machine. The use of the technology in the injection tool of an injection moulding machine, in order for example to monitor the cooling phase of the produced shaped parts is also conceivable.