METHOD FOR ASSESSING THE STATE OF PRESSING PUNCHES OF A ROTARY PRESS AND ASSOCIATED DEVICE

Abstract

A method of manufacturing a rotary press that assesses a wear state of pressing punches includes structuring the rotor to comprise an upper punch guide for upper pressing punches, a lower punch guide for lower pressing punches, and a die plate defining a plurality of cavities. A filling apparatus is structured to deliver a powder material into the plurality of cavities. A pressure apparatus includes an upper pressure roller that interacts with the upper press punches and a lower pressure roller that interacts with the lower pressing punches. At least one pressing force sensor is structured to measure pressing force progressions during the pressing of the powder material. An evaluation apparatus is structured to perform a state analysis of the measured pressing force progressions and individually assesses the wear state of at least one of the upper pressing punches and the lower pressing punches based on the state analysis.

Claims

1. A method of manufacturing a rotary press configured to assess a wear state of pressing punches of the rotary press, the method comprising: structuring a rotor configured to be rotated by a rotary drive, structuring the rotor to comprise, an upper punch guide for upper pressing punches, a lower punch guide for lower pressing punches, and a die plate arranged between the punch guides and defining a plurality of cavities, wherein the upper pressing punches and the lower press punches are structured to interact with the plurality of cavities of the die plate; structuring a filling apparatus to deliver a powder material into the plurality of cavities of the die plate; structuring a pressure apparatus to include an upper pressure roller configured to interact with the upper press punches and a lower pressure roller configured to interact with the lower pressing punches during operation in order to press the powder material in the cavities of the die plate; structuring at least one pressing force sensor to measure pressing force progressions at least one of the upper pressing punches and the lower pressing punches during the pressing of the powder material; and structuring an evaluation apparatus to, perform a state analysis of the measured pressing force progressions, and individually assesses the wear state of at least one of the upper pressing punches and the lower pressing punches based on the state analysis.

2. The method according to claim 1, wherein the performing the state analysis comprises comparing the measured pressing force progressions with at least one reference pressing force progression.

3. The method according to claim 1, wherein the performing the state analysis comprises determining a width of the measured pressing force progressions.

4. The method according to claim 1, wherein the performing the state analysis comprises determining a magnitude of a maximum of the measured pressing force progressions.

5. The method according to claim 1, wherein the performing the state analysis comprises determining at least one of; (i) multiple maxima of the measured pressing force progressions; and (ii) a distance between multiple maxima of the measured pressing force progressions.

6. The method according to claim 1, wherein the performing the state analysis comprises determining a time point for at least one of: (i) a rise of the measured pressing force progressions; and (ii) a fall of the measured pressing force progressions.

7. The method according to claim 6, wherein the performing the state analysis comprises determining a gradient of at least one of: (i) the rise of the measured pressing force progressions; and (ii) the fall of the measured pressing force progressions.

8. The method according to claim 3, further comprising structuring the evaluation apparatus to output a warning message when an increased wear of an assessed pressing punch is detected.

9. The method according to claim 8, wherein the warning message comprises at least one of: a suggestion for cleaning the assessed pressing punch; re-treating the assessed pressing punch; replacing the assessed pressing punch with a new pressing punch; replacing the upper pressing punches; and replacing the lower pressing punches.

10. The method according to claim 8, wherein the warning message comprises a suggestion for swapping the assessed pressing punch with increased wear with another pressing punch of the rotary press.

11. The method according to claim 1, wherein the performing the state analysis comprises a multivariate data analysis.

12. The method according to claim 11, wherein the multivariate data analysis comprises a principal component analysis.

13. The method according to claim 12, further comprising determining at least one principal component that exhibits a greatest variance with respect to the wear of at least one of the upper pressing punches and the lower pressing punches is identified for a large number of pressing force progressions.

14. The method according to claim 11, wherein the multivariate data analysis comprises a multivariate regression method.

15. The method according to claim 8, further comprising structuring the evaluation apparatus to assesses, using the state analysis, of at least one of: a state of a mirror surface; a state of a punch tip of the assessed pressing punch; and a pressing force exerted by the assessed pressing punch.

16. The method according to claim 1, further comprising structuring the evaluation apparatus to performs a data preprocessing of the measured pressing force progressions prior to performing the state analysis.

17. The method according to claim 1, further comprising structuring the evaluation apparatus to perform the state analysis using machine learning algorithms.

18. The method according to claim 1, further comprising structuring the evaluation apparatus to display results of the state analysis to an operator.

19. The method according to claim 18, further comprising structuring the evaluation apparatus to comprises an input apparatus configured to enable an operator to set parameters for the state analysis.

20. The method according to claim 1, further comprising positioning the at least one pressing force sensor at the upper pressure roller.

21. The method according to claim 1, further comprising positioning the at least one pressing force sensor at the lower pressure roller. 22. The method according to claim 1, further comprising measuring the pressing force progressions as at least one the upper pressing punches and the lower pressing punches pass through at least one of the upper pressure roller and the lower pressure roller.

23. The method according to claim 1, further comprising: structuring the pressure apparatus to further comprise a pre-pressure apparatus comprising an upper pre-pressure roller and a lower pre-pressure roller; arranging a pressing force sensor at the upper pre-pressure roller and arranging a pressing force sensor at the lower pre-pressure roller of the pressure apparatus; and measuring the pressing force progressions at the upper and lower pressing punches as the upper pressing punches pass through the upper pre-pressure roller and the lower pressing punches pass through the lower pre-pressure roller.

24. A rotary press, comprising: a rotor configured to be rotated by a rotary drive, wherein the rotor comprises, an upper punch guide configured for upper pressing punches, a lower punch guide configured for lower pressing punches; and a die plate positioned between the upper punch guide and the lower punch guide and defining a plurality of cavities, wherein the upper pressing punches and the lower pressing punches interact with the plurality of cavities of the die plate; a filling apparatus configured to dispense a powder material into the plurality of cavities of the die plate; a pressure apparatus comprising, an upper pressure roller configured to interact with the upper pressing punches, and a lower pressure roller configured to interact with the lower pressing punches during operation in order to press the powder material in the plurality of cavities of the die plate; a pressing force sensor arranged at the pressure apparatus and configured to measure a pressing force progressions at least one of: (i) the upper pressing punches, and (ii) the lower pressing punches during pressing of the powder material; and an evaluation apparatus configured to perform a state analysis of the measured pressing force progressions and to individually assess a state of wear of the at least one of: (i) the upper pressing punches; and (ii) the lower pressing punches based on the state analysis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] An exemplary embodiment of the invention is explained in greater detail below with reference to the figures

[0032] FIG. 1 schematically illustrates an embodiment of a rotary press according to the invention showing an unrolled representation of the rotor.

[0033] FIG. 2 graphically illustrates an example of pressing force progressions recorded using the rotary press according to the invention during pressing of powder material.

[0034] FIG. 3 graphically illustrates point values for two principal components determined according to the invention.

[0035] FIG. 4 schematically shows the state, assessed according to the invention, of the pressing punches of the rotary press.

[0036] The same reference signs refer to the same objects in the figures unless indicated otherwise.

DETAILED DESCRIPTION OF THE INVENTION

[0037] The rotary press shown in FIG. 1 is a rotary press for producing tablets, in which powdered material is pressed into tablets. The rotary press comprises a rotor rotatingly driven by a rotary drive with a die plate 10 having multiple cavities 12. The cavities 12 can be formed, for example, by bores in the die plate 10. The rotor further comprises multiple upper pressing punches 14 and lower pressing punches 16 which revolve synchronously with the die plate 10. The upper pressing punches 14 are axially guided in an upper punch guide 18 and the lower pressing punches 16 are axially guided in a lower punch guide 20. The axial movement of the upper pressing punches 14 and lower pressing punches 16 in the course of the rotation of the rotor is controlled by upper control cam elements 22 and lower control cam elements 24. The rotary press further comprises a filling apparatus 26, which comprises a filling reservoir 28 and a filling chamber 30 which are connected via a filling pipe 32. In this manner, in the present example, powder material arrives from the filling reservoir 28 via the filling tube 32 into the filling chamber 30 due to gravity and from there via a filling opening provided on the lower side of the filling chamber 30 into the cavities 12 of the die plate 10.

[0038] The rotary press further comprises a pressure apparatus 34. The pressure apparatus 34 comprises a pre-pressure apparatus having an upper pre-pressure roller 36 and a lower pre-pressure roller 38 as well as a main pressure apparatus having an upper pressure roller 40 and a lower pressure roller 42. Furthermore, the rotary press comprises an ejector apparatus 44 and a scraper apparatus 46 having a scraper element which supplies the tablets 48 produced in the rotary press to a discharge apparatus 50 for discharging from the rotary press. The scraper apparatus 46 may, for example, comprise a preferably crescent-shaped scraper element which scrapes tablets 48 conveyed by the lower pressing punches 16 onto the upper side of the die plate 10 in the region of the ejector apparatus 44 off of the die plate 10 and supplies them to the discharge apparatus 50.

[0039] The rotary press further comprises an evaluation apparatus 52 for controlling the operation of the rotary press and for carrying out the method according to the invention, as explained in greater detail below.

[0040] An upper pressing force sensor 56 is arranged on a holder 54 of the upper pressure roller 40. A lower pressing force sensor 60 is arranged on a holder 58 of the lower pressure roller 42. It should be noted that it is also possible to arrange only one pressing force sensor in the region of the upper pressure roller 40 or in the region of the lower pressure roller 42. Additionally or alternatively, corresponding pressing force sensors can also be arranged in the region of the upper pre-pressure roller 36 and/or lower pre-pressure roller 38. The lower and upper pressing force sensors 56, 60 may, for example, be load cells which are elastically deformed during the pressing of powder material, wherein the elastic deformation outputs an electrical voltage value that is proportional to the pressing force. The measured values of the upper and lower pressing force sensors 56, 60 are applied to the evaluation apparatus 52. In the present case, a pressing force progression is measured by means of the upper and lower pressing force sensors 56, 60 for each of the upper and lower pressing punches 14, 16 during pressing of the powder material in the cavities 12 of the die plate 10, in particular from the start to the end of contact of the punch heads of the pressing punches 14, 16 with the upper and lower pressure roller 40, 42, respectively.

[0041] The evaluation apparatus 52 performs a state analysis of the measured pressing force progressions and individually assesses the state of the upper and lower pressing punches 14, 16 based on the state analysis. This is explained in greater detail below based on an example.

[0042] FIG. 2 shows various pressing force progressions recorded, for example, by the upper pressing force sensor 56 at the upper pressing punches 14 over time. Here, the pressing force is plotted for three progressions against time. The first pressing force progression 62 was recorded using non-worn, in particular new upper and lower pressing punches 14, 16. A further pressing force progression 64 was recorded while a pair of upper and lower pressing punches 14, 16 were passing through the upper and lower pressure rollers 40, 42, wherein, in the example shown, the upper pressing punch 14 exhibited increased wear, in particular an abraded mirror surface of the punch head. The third pressing force progression 66 in FIG. 2 was recorded for a pair of upper and lower pressing punches 14, 16 as they passed through the pressure rollers 40, 42, wherein, in the case of this punch pair, both the upper pressing punch 14 and the lower pressing punch 16 exhibited increased wear, in particular an abraded mirror surface of the punch head.

[0043] A comparison of the pressing force progressions 62, 64, 66 shows that, with increasing wear of the pressing punches 14, 16, the magnitude of the maximum of the pressing force progression becomes smaller and, at the same time, the width of the pressing force progression increases. In particular, the pressing force progression rises earlier and falls later the greater the extent to which the pressing punches 14, 16 are worn. The reason for this is that, in the case of abraded punch heads for example, the mirror surface makes contact with the relevant pressure roller at an earlier point in time and accordingly loses contact with the relevant pressure roller at a later point in time. At the same time, the effective length of the relevant pressing punch 14, 16 is shortened, for example, on account of a worn punch head, and therefore the maximum value of the pressing force, i.e. the maximum of the pressing force curves, decreases while the side length stays the same. The pressing force progressions 62, 64, 66 shown in FIG. 2 are merely examples. Depending on the wear feature of the pressing punches 14, 16, further effects may occur which lead to a deviation of the measured pressing force progression from the pressing force progression of a new pressing punch 14, 16. For example, the presence of multiple maxima in the pressing force progression or a steeper or flatter rise and/or fall of the pressing force progression can indicate further wear features, for example a changed radius of the punch head, an irregular punch head surface, a changed mirror surface shape, or a shortened effective length of the relevant pressing punch 14, 16.

[0044] According to a first embodiment, the evaluation apparatus 52 is configured to compare the recorded pressing force progressions 62, 64, 66 with a reference pressing force progression. In the present case, the pressing force progression 62 of FIG. 2, which was recorded for a new and thus non-worn punch pair, could for example be recorded as the reference pressing force progression. Limit values for particular deviation features of the recorded pressing force 64, 66 from the reference pressing force progression 62 can then, for example, be stored in the evaluation apparatus 52. For example, a limit value can be defined for a permissible widening of the pressing force progressions 64, 66 relative to the reference pressing force progression 62 and/or a limit value can be defined for a permissible reduction of the maximum of the pressing force progressions 64, 66 relative to the reference pressing force progression 62. Said limit values can be entered by an operator, for example based on empirical values. The limit values can be stored individually for the relevant rotary press, the punches in use, and the tablets to be pressed, in particular the powder material and, for example, the side length. It is also possible for software to be stored in the evaluation apparatus 52 which uses machine learning algorithms, for example comprising neural networks, to continuously check and optimize the stored limit values.

[0045] If one of the limit values is exceeded, the evaluation apparatus 52 can, for example, output a warning message, for example on a display apparatus or via software on a computer, tablet, or smartphone, for example. The warning message may, for example, display increased wear of particular pressing punches 14, 16 and give recommendations for action, for example for replacing worn pressing punches 14, 16 or the entire set of upper and/or lower pressing punches 14, 16. Recommendations for action for cleaning or re-treating the worn pressing punches 14, 16 are also conceivable, as are recommendations for swapping pressing punches 14, 16 of the rotary press among themselves, i.e. finding new pairings for upper pressing punches 14 and lower pressing punches 16 in order to prevent unfavorable pairings, for example.

[0046] Another possibility for evaluating the recorded pressing force progressions 62, 64, 66 shall be explained based on FIG. 3. In this case, the evaluation apparatus 52 performs a multivariate data analysis, in particular comprising a principal component analysis. The aim of the principal component analysis is to identify, for a large number of recorded pressing force progressions 62, 64, 66, principal components that exhibit significant variance with regard to the wear of the pressing punches 14, 16, i.e. offer a good distinction with regard to criteria that are decisive for wear.

[0047] FIG. 3 is a so-called scores plot for graphically representing the pressing force curves 62, 64, 66 shown in FIG. 2 in the space of two principal components PC-1 and PC-2 determined in the course of the principal component analysis. The pressing force progressions 62, 64, 66 are shown as points, wherein in each case multiple measurements of the corresponding punch pairs, for example in the course of a multiple revolution of the rotor of the rotary press, are taken as a basis, such that in each case multiple points are represented in accordance with the pressing force progressions 62, 64, 66. The representation in a scores plot of this kind is such that two points are more similar the more densely they are arranged along an axis.

[0048] FIG. 3 clearly shows that the pressing force progression groups 62 for non-worn, new upper and lower pressing punches 14, 16, the pressing force progression points 64 for pairs of upper and lower pressing punches 14, 16 in which the upper pressing punch 14 exhibits increased wear, and the pressing force progression points 66 for punch pairs in which both the upper and the lower pressing punch 14, 16 exhibit increased wear differ significantly, in particular in the principal component PC-1. However, in the principal component PC-2, such a differentiation is not possible.

[0049] In the present case, it can therefore be concluded that the principal component PC-1 describes differences with regard to the state of wear of the pressing punch 14, 16, in particular the punch head, and in the example shown makes up 60.17% of the total variance of the samples. The principal component PC-2 thus describes other differences between the pressing force progressions 62, 64, 66 that cannot be directly assigned to the state of wear of the pressing punches 14, 16. For example, the principal component PC-2 may describe differently set side lengths of the tablets produced. Thus the multivariate data analysis is very useful for evaluating the pressing force progressions 62, 64, 66, for example in order to assess the state of wear of the pressing punches 14, 16, in particular their punch heads. The evaluation apparatus 52 can thus also use this to assess the state of the pressing punches 14, 16.

[0050] FIG. 4 shows an example of a possible display of the state of upper pressing punch assessed in each case by means of the evaluation apparatus 52, wherein, in the example shown, 38 upper pressing punches 14 of the rotary press are assessed and displayed. For each punch position, the assessment of the state of different parameters of the upper pressing punches 14 is displayed. The three bars for a respective punch position are shown enlarged in the bottom left in FIG. 4 for illustrative purposes. The upper bar 76 in each case shows the state of wear of the punch head, in particular the mirror surface. The central bar 78 in each case shows a deviation of the measured maximum pressing force from a target value and the lower bar 80 in each case shows a different geometrical deviation of the pressing punch 14, for example a reduced effective length. These different assessment parameters can be determined, for example, based on a comparison of the recorded pressing force progressions 64, 66 with the reference pressing force progression 62. An assessment is accordingly also possible using the principal component analysis, as explained above.

[0051] In the example shown, a first limit value 68 and 70 and a second limit value 72 and 74 drawn in for the upper bars 76 and the central bars 78, respectively, as shown clearly in the enlarged representation of the bars 76, 78. If the relevant state of wear reaches the first limit value 68 or 70, a first warning is output by the evaluation apparatus 52. In the example shown, this is the case for the upper pressing punch 14 at position 16 in the central bar 78. When the second limit value 72, 74 is reached, a request is output by the evaluation apparatus 52 to replace the relevant pressing punch 14 or to replace the entire set of upper and/or lower pressing punches 14, 16. With regard to the geometrical deviation assessed in each case in the lower bar 80, a corresponding warning message is output by the evaluation apparatus 52 as soon as the end of the bar is reached in each case.

[0052] The representation of FIG. 4 can, for example, be displayed to an operator in a display apparatus of the evaluation apparatus 52 or via a corresponding application on a computer, tablet, or smartphone. This can be continuously updated during operation of the rotary press, such that the operator has an overview of the state of wear of the pressing punches 14, 16 at all times and can react accordingly.

LIST OF REFERENCE SIGNS

[0053] 10 Die plate [0054] 12 Cavities [0055] 14 Upper pressing punches [0056] 16 Lower pressing punches [0057] 18 Upper punch guide [0058] 20 Lower punch guide [0059] 22 Upper control cam elements [0060] 24 Lower control cam elements [0061] 26 Filling apparatus [0062] 28 Filling reservoir [0063] 30 Filling chamber [0064] 32 Filling tube [0065] 34 Pressing apparatus [0066] 36 Upper pre-pressure roller [0067] 38 Lower pre-pressure roller [0068] 40 Upper pressure roller [0069] 42 Lower pressure roller [0070] 44 Ejector apparatus [0071] 46 Scraper apparatus [0072] 48 Tablets [0073] 50 Discharge apparatus [0074] 52 Evaluation apparatus [0075] 54 Holder [0076] 56 Upper pressing force sensor [0077] 58 Holder [0078] 60 Lower pressing force sensor [0079] 62 First pressing force progression [0080] 64 Second pressing force progression [0081] 66 Third pressing force progression [0082] 68 First limit value [0083] 70 First limit value [0084] 72 Second limit value [0085] 74 Second limit value [0086] 76 Upper bar [0087] 78 Central bar [0088] 80 Lower bar