APPARATUS FOR CHECKING A STATE OF A MACHINE PART

Abstract

Apparatus for checking a state of a machine part of a shaping machine, comprising an evaluation unit, at least one power loss sensor for ascertaining a power loss measurement signal which is representative of a power loss in and/or at the machine part, and at least one movement sensor for ascertaining a movement measurement signal which is representative of a movement of the machine part, wherein the evaluation unit is adapted to compute a damage indicator for the machine part from the power loss measurement signal and from the movement measurement signal.

Claims

1. Apparatus for checking a state of a machine part of a shaping machine, comprising an evaluation unit, at least one power loss sensor for ascertaining a power loss measurement signal which is representative of a power loss in and/or at the machine part, and at least one movement sensor for ascertaining a movement measurement signal which is representative of a movement of the machine part, wherein the evaluation unit is adapted to compute a damage indicator for the machine part from the power loss measurement signal and from the movement measurement signal.

2. Apparatus as set forth in claim 1 comprising a wear sensor, preferably a particle counter or oil condition sensor, for ascertaining the wear of the machine part, wherein that ascertained wear can be communicated as a wear measurement signal to the evaluation unit which additionally takes account of that wear measurement signal for calculating the damage indicator.

3. Apparatus for checking a state of a machine part of a shaping machine comprising an evaluation unit, and a wear sensor for ascertaining the wear of the machine part, wherein a wear measurement signal which is representative of that ascertained wear (VS) can be communicated to the evaluation unit, wherein the evaluation unit is adapted to compute a damage indicator for the machine part from the wear measurement signal.

4. Apparatus as set forth in claim 3 comprising at least one power loss sensor for ascertaining a power loss measurement signal which is representative of a power loss in and/or at the machine part, and/or at least one movement sensor for ascertaining a movement measurement signal which is representative of a movement of the machine part, wherein the evaluation unit is adapted to calculate a damage indicator for the machine part from the power loss measurement signal and/or from the movement measurement signal together with the wear measurement signal.

5. Apparatus as set forth in claim 1 wherein the machine part is a drive unit, preferably a transmission, particularly preferably a ball screw drive, of a shaping machine.

6. Apparatus as set forth in claim 1 wherein the evaluation unit is adapted to use the power loss measurement signal for correction of an ambient temperature measurement signal representing an ambient temperature, to obtain a cleaned temperature measurement signal.

7. Apparatus as set forth in claim 6 wherein provided on the shaping machine or in the region of the shaping machine is an ambient temperature sensor for measuring the ambient temperature and for outputting the ambient temperature measurement signal.

8. Apparatus as set forth in claim 1 wherein the movement sensor is in the form of a vibration sensor, a speed sensor or an acceleration sensor.

9. Apparatus as set forth in claim 8 wherein different vibration frequency ranges can be output as frequency bands with the acceleration sensor.

10. Apparatus as set forth in claim 1 wherein the evaluation unit calculates a chipping indicator from measurement values of the wear sensor and/or from the features, preferably frequency peaks or pulse signals, of the frequency bands.

11. Apparatus as set forth in claim 1 wherein the evaluation unit calculates a friction indicator from the power loss measurement signal, preferably from the cleaned temperature measurement signal.

12. Apparatus as set forth in claim 1 wherein the evaluation unit calculates an abrasion wear indicator from the movement measurement signal.

13. Apparatus as set forth in claim 10 wherein the damage indicator is composed from the chipping indicator the friction indicator and the abrasion wear indicator.

14. Apparatus as set forth in claim 1 wherein the evaluation unit additionally calculates the damage indicator from at least one electrical signal of the shaping machine.

15. Apparatus as set forth in claim 14 wherein the at least one electrical signal of the shaping machine represents a position and/or a direction of movement of the machine part of the shaping machine.

16. Apparatus as set forth in claim 14 wherein the at least one electrical signal of the shaping machine represents a temperature of a part, for example a spindle of the shaping machine, and said signal is also incorporated into ascertainment of the power loss.

17. Apparatus as set forth in claim 1 wherein the power loss sensor is in the form of a temperature sensor for determining the waste heat or in the form of a virtual sensor which ascertains the power loss from a difference between power fed into the shaping machine and issuing from the shaping machine.

18. A shaping machine, in particular an injection molding machine or injection press, comprising an apparatus as set forth in claim 1.

19. A shaping machine as set forth in claim 18 wherein the shaping machine has an open-loop or closed-loop control unit in signal-transmitting relationship with the evaluation unit for open-loop or closed-loop control of the shaping machine.

20. A shaping machine as set forth in claim 19 wherein the open-loop or closed-loop control unit provides for open-loop or closed-loop control of the shaping machine in dependence on the damage indicator communicated by the evaluation unit to the open-loop or closed-loop control unit and possibly shuts down the machine part.

21. A shaping machine as set forth in claim 19 wherein a warning signal can be output by way of the open-loop or closed-loop control unit in dependence on the damage indicator communicated by the evaluation unit to the open-loop or closed-loop control unit when the communicated damage indicator reaches a fixed threshold value.

22. A shaping machine as set forth in claim 18 wherein the damage indicator can be displayed by way of a display device.

23. A method of checking a state of a machine part of a shaping machine, in particular with an apparatus as set forth in claim 1, comprising the steps: ascertaining a power loss in and/or at the machine part, ascertaining a movement of the machine part, and calculating a damage indicator for the machine part by an evaluation unit from the power loss and from the movement.

24. A method as set forth in claim 23 comprising the step of ascertaining a wear of the machine part with a wear sensor, wherein the wear is taken into consideration for calculation of the damage indicator.

25. A method of checking a state of a machine part of a shaping machine, in particular with an apparatus as set forth in claim 3, comprising the steps: ascertaining a wear of the machine part, and calculating a damage indicator (SI) for the machine part by an evaluation unit from the ascertained wear.

26. A method as set forth in claim 25 comprising the steps: ascertaining a power loss in and/or at the machine part, and/or ascertaining a movement of the machine part, and calculating a damage indicator for the machine part by the evaluation unit, wherein in addition the power loss and/or the movement is/are taken into consideration for calculation of the damage indicator.

Description

[0030] Further details and advantages of the present invention are described more fully hereinafter by means of the specific description with reference to the embodiments by way of example illustrated in the drawings in which:

[0031] FIG. 1 diagrammatically shows a shaping machine with an apparatus for checking a state of a machine part,

[0032] FIG. 2 shows a graph of the power loss of the machine part along a time axis,

[0033] FIG. 3 shows a graph of frequency bands recorded by way of the acceleration sensor along a time axis,

[0034] FIG. 4 shows a graph with the composition of the damage indicator along a time axis,

[0035] FIG. 5 shows a graph of the power loss measurement signal with threshold value, and

[0036] FIG. 6 shows corresponding to FIG. 5 a graph of the damage indicator with an influencing function.

[0037] FIG. 1 diagrammatically shows a shaping machine 3. It has a ball screw drive 10 as a (at least one) machine part 2. The ball screw drive 10 is composed of the spindle 8 and the spindle nut 9. An oil sump 14 is disposed beneath the ball screw drive 10. Provided in the region of that oil sump 14 is a power loss sensor 5 for ascertaining a power loss VL. More specifically that power loss sensor 5 can be a thermometer for ascertaining the oil temperature. A power loss measurement signal M.sub.VL is passed from the power loss sensor 5 to an evaluation unit 4. Also provided in the region of the oil sump 14 is a wear sensor 7 for ascertaining the wear VS of the machine part 2. More specifically that wear sensor 7 can be a particle counter or an oil condition sensor. In detail there is provided an apparatus with which the (number of) ferromagnetic particles in the lubricant or lubricating agent are ascertained. From the wear sensor 7 a wear measurement signal M.sub.VS is also passed to the evaluation unit 4. A movement sensor 6 for ascertaining a movement B of the machine part 2 is arranged in or at the machine part 2. More specifically that movement sensor 6 can be an acceleration sensor for ascertaining frequency bands. A movement measurement signal M.sub.B is also communicated to the evaluation unit 4 from the movement sensor 6. An ambient temperature sensor 11 can also be provided to measure the ambient temperature U and to pass a corresponding ambient temperature measurement signal M.sub.U to the evaluation unit 4.

[0038] Subsequently a damage indicator SI is calculated in the evaluation unit 4 from those input signals, which damage indicator permits (relatively) accurate information about the actually prevailing damage to the machine part 2. For that purpose firstly the power loss measurement signal M.sub.VL and the ambient temperature measurement signal M.sub.U are brought together to give a cleaned temperature measurement signal M.sub.T. A friction indicator RI is then calculated from that cleaned temperature signal M.sub.T in the evaluation unit 4 by way of a stored algorithm. A wear indicator NI is calculated from the movement measurement signal M.sub.B in the evaluation unit 4. The chipping indicator AI is calculated from the wear measurement signal M.sub.VS in the evaluation unit 4. Additionally or alternatively that chipping indicator AI can also be calculated from the frequency peaks or pulse signals of the frequency bands of the movement sensor 6 (see the broken line in FIG. 1). Finally, the damage indicator SI is calculated on the basis of an algorithm stored in the evaluation unit 4 from at least one those indicatorspreferably from all three indicatorsfriction indicator RI, wear indicator NI and chipping indicator AI. FIG. 1 only shows the power loss by virtue of a temperature signal, in actual fact the power loss however can also be ascertained from the additionally consumed drive power.

[0039] That damage indicator SI is then compared to the service life specification of the manufacturer of the machine part 2 whereby the (probable) remaining service life is established. If no manufacturer specifications are available then a moment in time for the prognosticated breakdown (SI=1) can be specified by way of the rise in the damage indicator. That damage indicator SI (or the remaining service life derived therefrom) can then be displayed by way of a display device. More especially that can be effected by way of the display device 13 (screen) of the open-loop or closed-loop control unit 12 of the shaping machine 3. It is however also possible for the damage indicator SI to be output when a limit value is exceeded in the form of an acoustic or optical warning signal W, preferably by way of the display device 13. It is also possible for the open-loop or closed-loop control unit to provide for open-loop or closed-loop control of the shaping machine 3 in dependence on the damage indicator SI communicated by the evaluation unit 4 to the open-loop or closed-loop control unit 12, preferably shutting down the machine part 2, braking it or limiting certain movements. At least one value which originates directly from the shaping machine 3 or its open or closed-loop control unit 12 can also be involved in the calculation of the damage indicator SI. For example at least one electrical signal of the shaping machine 3 can represent a position P and/or a direction of movement R and/or a power consumption of the machine part 2.

[0040] In FIG. 1 the movement sensor 6 and the power loss sensor 5 are arranged or provided separately from the evaluation unit 4. As a difference from the illustrated case, those sensors can also be part of the evaluation unit 4.

[0041] FIG. 2 shows a graph illustrating the cleaned temperature M.sub.T. It will be seen from FIG. 2 that the power loss VL increases almost monotonically (or steadily) and only (slightly) collapses again at the end. For detection of the damage indicator SI it is sufficient if in a certain interval the cleaned temperature M.sub.T exceeds a static value dependent on the interval (scatter, mean value, median, etc). (In that respect reference can already first be made to FIG. 4: as the cleaned temperature M.sub.T collapses again shortly before the time t.sub.6 the value for the friction indicator RI is also taken back).

[0042] FIG. 3 shows three graphs illustrating the signal amplitudes SA measured by way of the acceleration sensor in various frequency ranges. In this respect various frequency bands (band 1, band 2 and band 3) are considered or investigated in isolation.

[0043] In FIG. 4 the various indicators are plotted along the time axis t. At the end of the time axis (fairly accurately between t.sub.5 and t.sub.6) the chipping indicator AI which (in this case) steadily increases, the friction indicator RI and the wear indicator NI are totaled to give a damage indicator SI which from then is above the threshold value L. In the present example that corresponds to a total breakdown. That evaluation of a measurement data set on a ball screw drive test stand extended over a sufficiently large number of test cycles, the number of test cycles corresponding to an average service life of the ball screw drive. In that case the ball screw drive was severely worn or no longer usable at the end. A marked rise in temperature (greater friction), individual frequency peaks (chips) and at the end a general rise in vibration (abrasion wear) can be seen. The rise in the damage indicator SI can be used to already conclude relatively early about the breakdown time t.sub.breakdown (corresponds to the time t.sub.6 or the attainment of the threshold value L). In actual operation countermeasures can already be taken here or maintenance measures can be planned.

[0044] FIG. 5 shows a pattern of a recording of a signal by a temperature sensor which has quite a number of peaks (that is to say abrupt rises and falls over a sufficiently smooth signal configuration). It is only when such a signal peak exceeds the limit value marked in broken line that this acts on the influencing function shown in FIG. 6. In general it is to be noted that the probability of effect after the occurrence of an indicator event can also decrease again.

[0045] FIG. 6 shows an example of the probability of an effect in relation to the friction indicator. After the machine part temperature exceeds the predefined limit value it quickly decreases again. After it falls below the limit value the probability of effect exponentially falls. After the machine part temperature exceeds the predefined limit value (shown in FIG. 5) the influencing function is set to 1, that is to say the indication has an influence on the overall indicator (see FIG. 4 after time t.sub.5). When the limit value is first exceeded therefore the indicator is set to 1 to establish the onset of that event. If the temperature falls below the limit value again the influence is not set to 0 but it begins to fall in accordance with an exponential function. The post-action time of a damage event is modeled in that way. Before the times t.sub.03 and t.sub.09 the limit value is exceeded again, for which reason the influencing function is set to 1 again.

[0046] Finally it is to be noted that a substantial innovation is the combination of power loss and movement (vibration). In addition no attempt is made to simulate an exact mechanical or thermal model but the frequency bands are analyzed in respect of a continuous rise (abrasion wear) or individual swings (chipping). A measurement result by way of example in respect of a ball screw drive test stand is shown in FIG. 4. It will be clearly seen that wear is already established at an early time (in the specific case several weeks before the actual breakdown) and thus the breakdown can be predicted.

[0047] Further measurements have shown that the merging of temperature and vibration does not necessarily have to be sufficient as in some tests in spite of massive damage to the ball screw drive the damage indicator SI did not increase. Therefore the use of the wear sensor is additionally recommended. That provides an output signal proportional to the number of ferromagnetic particles. As these occur even with slight wear on the ball screw drive that sensor value further improves the damage indicator.

LIST OF REFERENCES

[0048] 1 apparatus [0049] 2 machine part [0050] 3 shaping machine [0051] 4 evaluation unit [0052] 5 power loss sensor [0053] 6 movement sensor [0054] 7 wear sensor [0055] 8 spindle [0056] 9 spindle nut [0057] 10 ball screw drive [0058] 11 ambient temperature sensor [0059] 12 open-loop or closed-loop control unit [0060] 13 display device [0061] 14 oil sump [0062] VL power loss [0063] M.sub.VL power loss measurement signal [0064] B movement [0065] M.sub.B movement measurement signal [0066] SI damage indicator [0067] VS wear [0068] U ambient temperature [0069] M.sub.T cleaned temperature measurement signal [0070] M.sub.U ambient temperature measurement signal [0071] RI friction indicator [0072] NI abrasion wear indicator [0073] AI chipping indicator [0074] P position of the machine part [0075] R direction of movement of the machine part [0076] W warning signal [0077] L threshold value [0078] SA signal amplitude