METHOD FOR DIAGNOSING A STATE OF AT LEAST ONE COMPONENT OF A MOLDING MACHINE

Abstract

A method of diagnosing a state of at least one component of a molding machine is performed such that a state of the at least one component is determined on the basis of a vibration measured at the molding machine. A drive unit of the molding machine accelerates and/or decelerates at least one movable element provided at the molding machine in such a way that the vibration is stimulated in a predetermined frequency range.

Claims

1. A method for diagnosing a state of at least one component of a molding machine, wherein a state of the at least one component is determined on the basis of a vibration measured at the molding machine, wherein a drive unit of the molding machine accelerates and/or decelerates at least one movable element provided at the molding machine in such a way that the vibration is stimulated in a predetermined frequency range.

2. The method according to claim 1, wherein the predetermined frequency range is selected such that at least one natural frequency of the at least one component to be diagnosed lies in the predetermined frequency range.

3. The method according to claim 1, wherein the predetermined frequency range is defined by a plus/minus of 5% of the natural frequency around the natural frequency of the at least one component to be diagnosed.

4. The method according to claim 1, wherein as vibration, a vibration of the molding machine and/or of the at least one movable element and/or of the at least one component to be diagnosed is stimulated.

5. The method according to claim 1, wherein at least one ambient condition is taken into account when defining the predetermined frequency range.

6. The method according to claim 1, wherein a movable plate of a molding machine is used as the movable element, which is accelerated and/or decelerated via a closing unit, which preferably has a toggle mechanism.

7. The method according to claim 1, wherein a measuring device of the molding machine is used to measure the vibration.

8. The method according to claim 1, wherein a measurement of the vibration by stimulation in a predetermined frequency range is carried out several times—preferably 5 to 10 times—and the results of the measurements are used as an average value for diagnosis.

9. The method according to claim 1, wherein a frequency of the measured vibration is compared for diagnosis with a natural frequency of the at least one component to be diagnosed in a predefined state.

10. The method according to claim 9, wherein, in the event of a deviation of the frequency of the measured vibration with respect to the natural frequency of the at least one component to be diagnosed in the predefined state, being greater than/equal to a predetermined deviation, a damage and/or a defect and/or a misadjustment of the at least one component is detected, wherein preferably an error message is output.

11. A molding machine with at least one movable element, wherein a drive unit is designed in order to accelerate and/or decelerate the at least one movable element, at least one measuring device for measuring a vibration of the molding machine, and at least one control unit configured to carry out the method according to claim 1.

12. The molding machine according to claim 11, wherein the drive unit is designed as a rotational drive which transmits the rotational movement to the molding machine via at least one belt.

13. The molding machine according to claim 11, wherein the drive unit comprises at least one encoder which is designed as a sensor of the measuring device for measuring a vibration.

14. A computer program product comprising commands which, when the program is executed by a computer, instruct the computer to execute the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Further exemplary advantages and details of the invention can be seen in the figures and the description below, in which:

[0056] FIG. 1 is a schematic illustration of an embodiment of a molding machine,

[0057] FIG. 2 shows a schematic sequence of an exemplary method according to the invention,

[0058] FIGS. 3a, 3b show exemplary profile dynamics of the speed profile of a closing unit to vibration stimulation, and

[0059] FIG. 4 shows an exemplary frequency analysis.

DETAILED DESCRIPTION OF THE INVENTION

[0060] FIG. 1 shows a schematic illustration of an embodiment of a molding machine 7 according to the invention. More precisely, FIG. 1 shows a closing unit 8 of the molding machine 7, in which a movable plate 9 can be moved by means of a toggle mechanism 6 which is braced on a face plate 2. A plasticizing and injection unit known per se and possible peripheral devices are not shown.

[0061] In this embodiment, the toggle mechanism 6 is driven by a drive unit 3 via a hollow shaft 1, wherein the drive unit 3 in this particular embodiment is designed as a spindle drive.

[0062] The drive unit 3 is connected to an encoder 4 via a belt 5. This embodiment of a drive unit 3, which is connected to an encoder 4 via a belt 5, is known from the prior art, and is used to determine a position of the drive unit 3 and/or the closing unit 8 via the encoder 4.

[0063] FIG. 2 shows a schematic sequence of an exemplary method according to the invention. To initiate the method for diagnosing a state of at least one component of the molding machine 7, a vibration 11 in a predetermined frequency range is first stimulated by accelerating or decelerating at least one movable element provided on the molding machine 7 (for instance of the movable plate 9) by appropriate control or regulation of the drive unit 3.

[0064] Depending on the desired frequency range of the vibration 11, the stimulation by the drive unit 3 can be changed.

[0065] Subsequently, a vibration 11 can be detected via a measuring device 10 of the molding machine 7 (for instance an encoder 4). This vibration 11 measured by the measuring device 10 can then be transmitted to a control unit 12 of the molding machine.

[0066] The stimulation to a vibration 11 in a predetermined frequency range and measurement by the measuring device 10 can be repeated n times by the control unit 12 (wherein n is greater than or equal to 1, preferably a repetition of 5 to 10 times is provided), in order to be able to take into account any unpredictable outliers that may be present by an averaged measuring result.

[0067] The control unit 12 of the molding machine can evaluate the results after the measurement procedure has been completed and output an error message 13 if the frequency of the vibration 11 deviates from a previously defined natural frequency of a component to be diagnosed by more than a tolerable deviation.

[0068] This error message 13 can make itself recognizable to an operator of the molding machine 7 as an acoustic and/or visual signal. However, it can also be provided alternatively or additionally that the molding machine 7 is automatically set to an idle state by the control unit 12.

[0069] In addition, as indicated by the dashed chain in FIG. 2, it may be provided that the signals of the measuring device 10 are transmitted by the control unit 12 to an external storage medium and/or calculation medium 15 by means of a data transmission link 14.

[0070] The calculation of a deviation of the frequency of the vibration 11 from a natural frequency of the component to be diagnosed may also be carried out in this external storage medium and/or calculation medium 15, wherein the deviation or the diagnosis result may be passed on to an external person or an external company 16.

[0071] The external person or the external company 16 may be, for instance, an owner or another person of the company who remotely monitors or controls the production of the molding machine 7. Access by a maintenance company or a molding machine manufacturer is also quite imaginable.

[0072] In an example of a closing and/or opening movement of a closing unit 8 by means of a movable plate 9 for stimulation of the vibration 11, the following characteristic quantities for changing the frequency range are obtained: [0073] travelled lift, [0074] speed, [0075] clamping force, and [0076] profile dynamics.

[0077] FIGS. 3a and 3b show how, by way of example, the profile dynamics of the speed profile of a closing unit 8 can be changed in order to stimulate a component to be diagnosed and/or the closing unit 8 and/or the entire molding machine 7 to a vibration 11 in a defined frequency range. The Y-axis represents the acceleration in arbitrary units.

[0078] In this context, FIG. 3a shows the profile dynamics of the speed profile of a closing unit 8, more precisely the speed profile of a movable plate 9 in the normal production cycle, wherein the opening movement is shown on the left side and the closing movement on the right side.

[0079] FIG. 3b shows an adapted profile dynamic for stimulation of a vibration 11, wherein again the opening movement is shown on the left and the closing movement on the right.

[0080] From comparing FIG. 3a directly with FIG. 3b, it can be seen how the profile dynamics setting creates a very good option for stimulating a vibration 11 in a certain frequency range, even with little freedom of movement available (such as, for instance, the lift of the movable plate 9).

[0081] FIG. 4 now shows an exemplary frequency analysis, wherein a molding machine 7 has been stimulated to a vibration, which is shown as a solid line.

[0082] Then, a measurement was made by a measuring device 10 on the molding machine 7, wherein the measured vibration 11 is shown by the dashed line.

[0083] It can be seen that a deflection of the amplitude of the measured vibration 11 forms in a frequency range of X, which provides direct information about the state of the at least one component to be diagnosed.

[0084] Since a natural frequency of the at least one component to be diagnosed of Y has now been defined in the optimum case, a frequency deviation of the vibration of approx. Z can be determined, wherein it has been found from testing that a defect of the at least one component to be diagnosed is to be assumed already from a deviation smaller than Z.

[0085] Consequently, in this case, an error message 13 can be output by the control unit 12.

LIST OF REFERENCE SIGNS

[0086] 1 hollow shaft [0087] 2 face plate [0088] 3 drive unit [0089] 4 encoder [0090] 5 belt [0091] 6 toggle mechanism [0092] 7 molding machine [0093] 8 closing unit [0094] 9 movable plate [0095] 10 measuring device [0096] 11 vibration [0097] 12 control unit [0098] 13 error message [0099] 14 data transmission link [0100] 15 external storage medium and/or calculation medium [0101] 16 external person or external company