Injection moulding device and method for determining a status of an injection moulding device

Abstract

The invention relates to an injection moulding device and a corresponding method for producing moulded parts. The injection moulding device comprises an injection moulding tool, a vibration sensor for measuring the vibrations of the injection moulding tool during the production cycle, a holder that receives the vibration sensor and holds same in a defined position on the injection moulding tool, a control unit for controlling the injection moulding device, and an evaluation unit, wherein the injection moulding tool comprises an ejector side and a nozzle side, wherein the ejector side and the nozzle side can be moved relative to one another between a closed and an open position, wherein the ejector side and the nozzle side are in contact in the closed position and form a chamber, wherein the holder has an elastic element, wherein the elastic element exerts a force on the vibration sensor, and wherein the evaluation unit is designed in such a way that it determines the status of the injection moulding tool on the basis of the measured vibrations and on the basis of the control signals of the control unit.

Description

[0001] INJECTION MOLDING DEVICE AND METHOD FOR DETERMINING A STATE OF THE INJECTION MOLDING DEVICE

[0002] Technical area

[0003] The present invention relates to an injection molding device and a method for determining the condition of the injection molding device.

[0004] State of the art

[0005] Conventional injection molding machines are known from the state of the art, used to produce molded parts, usually made of plastic. In particular, the core element of the injection molding machine, the injection molding tool, requires regular maintenance. A preventive maintenance strategy is usually pursued. This means that maintenance is performed more frequently than necessary to ensure proper function and sufficient quality of all manufactured molded parts. Such a preventive maintenance strategy is therefore particularly time-consuming and cost-intensive.

[0006] Description of the invention

[0007] An object of the invention is therefore to provide an injection molding device together with corresponding methods which enable a particularly technically long-lasting use of the injection molding device with consistently high quality of the molded parts produced.

[0008] The object is achieved by the subject matter of the independent claims. Advantageous developments of the invention are specified in the dependent claims, the description, and the accompanying figures. According to a first aspect of the invention, the object is achieved by an injection molding device for producing molded parts, comprising an injection molding tool, a vibration sensor for measuring the vibrations of the injection molding tool during the production cycle, a holder that accommodates the vibration sensor and holds it in a defined position on the injection molding tool, a control device for controlling the injection molding device, and an evaluation unit, wherein the injection molding tool comprises an ejector side and a nozzle side.The ejector side and the nozzle side are movable relative to each other between a closed and an open position, with the ejector side and the nozzle side touching in the closed position and forming a chamber. The holder has an elastic element, which exerts a force on the vibration sensor. The evaluation unit is designed such that the evaluation unit determines the state of the injection molding tool based on the measured vibrations and the control signals from the control device.

[0009] A key advantage of the injection molding device according to the invention is that, particularly through the targeted positioning of the vibration sensor on the injection mold, the condition of the injection mold can be determined with particular precision. In particular, through the arrangement of the vibration sensor in the holder according to the invention and through the exertion of a force by an elastic element on the vibration sensor in the holder, the vibrations in the injection mold can be detected with particular precision, allowing the condition of the injection mold to be determined with particular accuracy. Furthermore, the ability to determine the condition of the injection mold with particular precision reduces the risk of unplanned downtimes and downtimes.

[0010] The measured vibrations may be the structure-borne sound of the injection molding tool. The evaluation unit can be designed so that the condition of other elements of the injection molding device, such as the injection unit of the injection molding device, in particular the screw, can also be determined.

[0011] The vibration sensor can be designed in such a way that the vibration sensor detects the deflection of the vibration over time.

[0012] The vibration sensor can be a broadband sensor, preferably having a measuring range between 20 kHz and 450 kHz.

[0013] The force exerted by the elastic element on the vibration sensor can be a constant preload force. The vibration sensor can be arranged in the holder between the elastic element and the surface of the injection mold.

[0014] The evaluation unit can be designed in such a way that the evaluation unit adapts the maintenance interval of the injection molding device or the injection molding tool based on the determined condition of the injection molding tool.

[0015] In addition, the evaluation unit can be part of the control device, in particular a software component of the control device.

[0016] The specific condition of the injection molding tool can be the wear condition of the injection molding tool.

[0017] The ejector side and the nozzle side of the injection molding tool can be movable relative to each other such that the ejector side is movable and the nozzle side is immovable.

[0018] According to one embodiment, the elastic element can be a disc spring. A disc spring is a particularly suitable elastic element because it is particularly compact and inexpensive to manufacture.

[0019] However, the use of another elastic element, such as a coil spring and / or a rubber buffer, is also conceivable. According to one embodiment, the holder can have a base plate and a housing. The housing and the base plate can have several through holes that serve to screw the holder to the injection molding tool. Such a screw connection of the holder to the injection molding tool enables particularly good transmission of the vibrations prevailing in the injection molding tool to the vibration sensor mounted in the holder, thus enabling particularly precise measurement of the vibrations prevailing in the injection molding tool and thus a particularly precise determination of the condition of the injection molding tool.

[0020] In the assembled state, the base plate can be arranged between the housing and the injection molding tool.

[0021] Alternatively, the holder can also be mounted to the injection molding tool using magnets and / or other fastening devices.

[0022] In addition, a coupling agent, particularly silicone grease, can be placed between the base plate and the surface of the injection mold. This reduces the damping of vibrations during the transition from the injection mold to the holder or vibration sensor, thus increasing the accuracy of the vibration measurement.

[0023] It would also be conceivable to arrange such a coupling agent between the base plate and the vibration sensor.

[0024] In addition, the damping between the injection mold and the holder or vibration sensor can be reduced, for example, by optimizing the surface finish of the injection mold and the holder. It is conceivable, for example, that these surfaces have a particularly low level of roughness.

[0025] According to one embodiment, the through holes can be arranged asymmetrically to one another. This ensures that the holder is mounted at the intended position of the injection molding tool with the intended orientation. Correct alignment and repeatable mounting of the holder or vibration sensor guarantees particularly precise determination of the condition of the injection molding tool. The measurement results of the vibration sensor depend, among other things, on the mounting position of the holder or vibration sensor, so repeatable positioning of the holder or vibration sensor provides particularly well-evaluated data.

[0026] According to one embodiment, the holder, in particular the base plate, can be made of electrically insulating material. Additionally or alternatively, the holder can be designed such that the vibration sensor is galvanically decoupled from the injection molding tool when mounted. One possibility for implementing such galvanic decoupling, in addition to the described use of electrically insulating material for the holder, is the additional arrangement of an electrically insulating element between the holder or vibration sensor and the injection molding tool. This prevents the sensor from being influenced by possible other electrical circuits in the injection molding device, thereby increasing the quality of the measurement data from the vibration sensor and thus enabling a particularly precise determination of the condition of the injection molding tool.

[0027] According to one embodiment, the injection molding device can further comprise a pressure sensor for measuring the pressure in the chamber, wherein the evaluation unit is particularly designed such that the evaluation unit additionally determines the condition of the injection molding tool based on the measured pressure. By additionally measuring and evaluating the pressure in the chamber formed by the injection molding tool, a particularly precise determination of the condition of the injection molding tool can be achieved.

[0028] According to one embodiment, the injection molding device can have at least one further vibration sensor, wherein the evaluation unit is preferably designed such that the evaluation unit additionally determines the state of the injection molding tool based on the vibrations measured by the further vibration sensor, and wherein the injection molding device preferably has a further holder that accommodates the further vibration sensor and holds it in a defined position on the injection molding tool. The additional use of at least one further vibration sensor enables a particularly precise determination of the state of the injection molding tool, since further measurement data enable a more granular recording of the condition prevailing in the injection molding tool. In addition, the quality of the information contained therein and to be evaluated can be increased by fusion of the sensor data obtained by means of vibration sensors and / or further vibration sensors.

[0029] The additional bracket can be identical in construction to the bracket.

[0030] According to one embodiment, the vibration sensor and / or the additional vibration sensor can be arranged on the ejector side, preferably spaced apart from each other on the ejector side. Arranging the vibration sensor and / or the additional vibration sensor on the ejector side enables the detection of the vibrations that occur during the ejection of the molded part. Consequently, a larger portion of the molded part's manufacturing cycle can be monitored and evaluated by sensors, allowing a particularly precise determination of the condition of the injection molding tool.

[0031] According to one embodiment, the vibration sensor and / or the additional vibration sensor can be a piezoelectric sensor. Using a piezoelectric vibration sensor, a particularly accurate measurement of the vibration can be achieved in a particularly advantageous manner, allowing a particularly precise determination of the condition of the injection molding tool.

[0032] Alternatively or additionally, the vibration sensor and / or the further vibration sensor can be an acceleration sensor, in particular a Micro-Electro-Mechanical System (MEMS) sensor.

[0033] According to one embodiment, the injection molding device can have at least one further sensor, preferably a temperature sensor for measuring the injection mold temperature, wherein the evaluation unit is preferably designed such that the evaluation unit additionally determines the state of the injection mold based on the parameters measured by the further sensor, preferably a temperature sensor. The additional use of at least one further sensor, in particular a temperature sensor for measuring the injection mold temperature, enables a particularly precise determination of the state of the injection mold, since additional measurement data enable a more granular recording of the condition prevailing in the injection mold. In addition, the quality of the information contained therein and to be evaluated can be increased by fusion of the sensor data obtained by means of vibration sensors and / or other sensors.In particular, the measured injection mold temperature can allow conclusions to be drawn about increased friction of the moving parts.

[0034] Alternatively or additionally, the injection molding device may comprise a temperature sensor for measuring the temperature in the chamber of the injection mold.

[0035] Alternatively or additionally, the injection molding device may comprise a temperature sensor for measuring the ambient temperature and / or the temperature of the coolant in the cooling circuit.

[0036] The temperature sensor(s) can be resistance temperature sensors with PT 100 sensors and / or PT 1000 sensors.

[0037] According to a second aspect of the invention, the object is achieved by a method for determining a state of the injection molding tool of an injection molding device according to the invention, the method comprising the following method steps:

[0038] Recording the vibrations of the injection molding tool,

[0039] In particular, recording the pressure curve in the chamber,

[0040] In particular, recording the curves of other sensor signals, preferably the temperature curve of the injection molding tool,

[0041] Detecting the control signals of the control device,

[0042] Evaluation of the detected vibrations, preferably the pressure curve and / or the curves of further sensor signals, particularly preferably the temperature curve of the injection molding tool, as a function of the detected control signals, wherein a spectrogram is generated for each production cycle of a molded part based on the detected vibrations, wherein the state of the injection molding tool is inferred based on the spectrogram and the control signals and preferably the pressure curve and / or the curves of further sensor signals, particularly preferably the temperature curve of the injection molding tool. A significant advantage of the method according to the invention for determining a state of the injection molding tool of an injection molding device according to the invention is that, in particular by detecting the vibrations using a vibration sensor, the state of the injection molding tool can be inferred particularly accurately.In particular, by evaluating the recorded vibrations by generating a spectrogram from the recorded vibrations, the condition of the injection mold can be determined particularly efficiently. Recording the vibrations generates large amounts of data. By converting this data into a spectrogram, the data volume can be significantly reduced. This, in turn, simplifies the subsequent analysis of the spectrogram and makes it more efficient.

[0043] The spectrogram can be generated from the recorded oscillations using a Fourier transform, in particular a short-time Fourier transform (STFT).

[0044] The use of a Fourier transform, in particular a short-time Fourier transform (STFT), allows a particularly fast and therefore efficient generation of a spectrogram.

[0045] The recorded vibrations and / or the recorded pressure curve and / or the recorded additional curves can be further processed by summarizing the large number of recorded data points, particularly 100 data points at a time, by determining their mean or maximum values. This further reduces the amount of data to be processed, making the evaluation of the recorded data more efficient.

[0046] The control signals can be used to determine the process phases of a molded part's manufacturing cycle.

[0047] In addition, machine parameters of the injection molding device, in particular the injection time and / or holding pressure time and / or the holding pressure and / or the time of switching to holding pressure, can be recorded. The recorded machine parameters can be included in the evaluation of the recorded vibrations and / or the recorded pressure curve and / or the recorded curves of other sensor signals in order to draw conclusions about the condition of the injection molding tool. The recorded pressure curves and / or the recorded curves of other sensor signals can be time-dependent curves within the scope of the invention.

[0048] Short character description

[0049] An advantageous embodiment of the invention is explained below with reference to the accompanying figures. They show:

[0050] Figure 1 is a perspective view of a holder with a mounted vibration sensor according to an embodiment of the injection molding device;

[0051] Figure 2 is a sectional view of the bracket with the vibration sensor mounted according to Figure 1;

[0052] Figure 3 shows an injection molding tool with a mounted holder according to Figure 1.

[0053] Figure 3 shows an injection molding tool 1 according to the invention, which is integrated into an injection molding device (not shown). A holder 3 is mounted on the injection molding tool 1, which, in the mounted state, accommodates a vibration sensor 2 and holds it in a defined position. The injection molding tool 1 essentially has two sides that can be moved relative to one another, the ejector side 4 and the nozzle side 5. In the closed position shown, the ejector side 4 and the nozzle side 5 form a chamber. The chamber can preferably be filled with injection molding material by means of a nozzle 10. Preferably, in an open position (not shown), the molded part formed by the chamber can be removed. In particular, the ejector side 4 can be movable and the nozzle side 5 can be stationary for this purpose.The injection molding device also has a control unit (not shown) for controlling the injection molding device and an evaluation unit (not shown). The evaluation unit evaluates the vibrations detected by the vibration sensor 2 based on the control signals of the control unit and thus determines the state of the injection molding tool 1.

[0054] The holder 3 can, as can be seen in Figure 3, be mounted on the ejector side 4 of the injection molding tool 1. Alternatively, the holder 3 can also be mounted on the nozzle side 5 of the injection molding tool 1. It is also conceivable to mount two holders 3 with vibration sensors 2 mounted therein on the ejector side 4 and the nozzle side 5 of the injection molding tool 1. Furthermore, several holders 3 with mounted vibration sensors 2 can be arranged distributed on the ejector side 4 and / or the nozzle side 5 of the injection molding tool 1.

[0055] The detailed structure of the holder 3 with the vibration sensor 2 inserted can be seen in particular in Figures 1 and 2. As can be seen especially in Figure 2, the holder 3 has an elastic element 6. The elastic element shown in Figure 2 is preferably a disc spring 6. The elastic element 6 is arranged such that the elastic element 6 exerts a force on the vibration sensor 2. As shown by way of example in Figure 2, the disc spring 6 can rest on the vibration sensor 2 for this purpose. For this purpose, the disc spring 6 or another elastic element 6 can be inserted together with the vibration sensor 2 into the space spanned by the holder. Preferably, the disc spring 6 or the elastic element 6 generates a constant force on the vibration sensor 2, particularly preferably in the direction of the injection molding tool 1. The holder 3 preferably has a base plate 7 and a housing 8.In addition, the housing 8 and the base plate 7 preferably have through-holes 9 so that the holder 3, as can be seen in Figure 3, can be screwed to the injection molding tool 1 using appropriate screws. For this purpose, the screws are screwed through the through-holes 9 into the injection molding tool 1. The base plate 7 is preferably arranged on the injection molding tool 1, with silicone grease particularly preferably being introduced between the surface of the injection molding tool 1 and the base plate 7 in order to optimize the transmission of vibrations from the injection molding tool 1 into the holder 3 and ultimately to the vibration sensor 2.

[0056] In particular, correct placement and orientation of the holder 3 on the injection molding tool 1 is important. This can be ensured, for example, by an asymmetrical arrangement of the through-holes 9, which, however, is not shown in the figures. Such an asymmetrical arrangement of the through-holes as well as the corresponding threaded holes in the injection molding tool 1 only allows a defined mounting position of the holder 3 on the injection molding tool 1. The housing 8 of the holder 3 can also, as can be seen from Figure 1, have a recess 11 that allows the vibration sensor 2 to be connected by means of a cable in the mounted state.

[0057] The vibration sensor 2 is preferably a piezoelectric sensor. Such a piezoelectric vibration sensor 2 can, as shown in Figures 1 and 2, have a substantially cylindrical shape. Furthermore, the vibration sensor 2 can be arranged directly on the base plate 7. Galvanic decoupling of the vibration sensor 2 from the injection molding tool 1 is particularly preferred. For this purpose, the holder 3, in particular the base plate 7 of the embodiment shown in the figures, is preferably made at least partially of an electrically non-conductive material. Thus, the base plate 7 can be made of polished steel but have a ceramic plate that serves as a contact surface for the vibration sensor.

[0058] The injection molding device preferably has one or more additional sensors, such as a temperature sensor for measuring the injection mold temperature or a pressure sensor for measuring the pressure in the chamber. None of these additional sensors are shown in the figures. For example, it would be conceivable to arrange a pressure sensor in the chamber or in the nozzle 10. A temperature sensor can be arranged, for example, on the surface of the injection mold 1.

[0059] The figures are merely schematic representations and serve only to illustrate the invention. Identical or equivalent elements are provided with the same reference numerals throughout.

[0060] LIST OF REFERENCE SYMBOLS

[0061] 1 injection molding tool

[0062] 2 Vibration sensor 3 Bracket

[0063] 4 Ejector side

[0064] 5 Nozzle side

[0065] 6 Elastic element

[0066] 7 Base plate 8 Housing

[0067] 9 through hole

[0068] 10 nozzle

[0069] 11 Recess

Claims

PATENT CLAIMS Injection molding device for producing molded parts, comprising: an injection molding tool (1), a vibration sensor (2) for measuring the vibrations of the injection molding tool (1) during the production cycle, a holder (3) which receives the vibration sensor (2) and holds it in a defined position on the injection molding tool (1), a control device for controlling the injection molding device, and an evaluation unit, wherein the injection molding tool (1) comprises an ejector side (4) and a nozzle side (5), wherein the ejector side (4) and the nozzle side (5) are movable relative to one another between a closed and an open position, wherein the ejector side (4) and the nozzle side (5) are in the closed Position and form a chamber, wherein the holder (3) has an elastic element (6), wherein the elastic element (6) exerts a force on the vibration sensor (2), and wherein the evaluation unit is designed such that the evaluation unit determines the state of the injection molding tool (1) on the basis of the measured vibrations and on the basis of the control signals of the control device. Injection molding device according to one of the preceding claims, wherein the elastic element (6) is a disc spring. Injection molding device according to one of the preceding claims, wherein the holder (3) has a base plate (7) and a housing (8), and wherein the housing (8) and the base plate (7) have a plurality of through holes (9) which serve to screw the holder (3) to the injection molding tool (1). Injection molding device according to claim 3, wherein the through holes (9) are arranged asymmetrically to one another. Injection molding device according to one of the preceding claims, wherein the holder (3), in particular the base plate (7), is made of electrically insulating material, and / or wherein the holder (3) is designed such that the vibration sensor (2) is galvanically decoupled from the injection molding tool (1) in the mounted state. Injection molding device according to one of the preceding claims, comprising a pressure sensor for measuring the pressure in the chamber, wherein the evaluation unit is designed such that the evaluation unit additionally determines the state of the injection molding tool (1) based on the measured pressure.Injection molding device according to one of the preceding claims, wherein the injection molding device has at least one further vibration sensor, wherein the evaluation unit is designed such that the evaluation unit additionally determines the state of the injection molding tool (1) on the basis of the vibrations measured by means of the further vibration sensor, and wherein the injection molding device preferably has a further holder which receives the further vibration sensor and holds it in a defined position on the injection molding tool (1). Injection molding device according to one of the preceding claims, wherein the vibration sensor (2) and / or the further vibration sensor are arranged on the ejector side (4), preferably at a distance from one another on the ejector side (4). Injection molding device according to one of the preceding claims, wherein the vibration sensor (2) and / or the further vibration sensor is a piezoelectric sensor.Injection molding device according to one of the preceding claims, wherein the injection molding device has at least one further sensor, preferably a temperature sensor for measuring the injection molding tool temperature, and. wherein the evaluation unit is designed such that the evaluation unit additionally determines the state of the injection molding tool (1) based on the parameters measured by the further sensor, preferably a temperature sensor.

11. A method for determining a state of an injection molding device according to one of the preceding claims, wherein the method comprises the following method steps: Detecting the vibrations of the injection moulding tool (1), Detecting the control signals of the control device, - Evaluating the detected vibrations depending on the detected Control signals, wherein for each production cycle of a molded part a spectrogram is generated on the basis of the detected vibrations, wherein the state of the injection molding tool (1) is deduced from the spectrogram and the control signals.

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