METHOD FOR STRAIGHTENING BAR-SHAPED MATERIAL AND A STRAIGHTENING MACHINE

Abstract

The invention relates to a method for straightening non-straight bar-shaped material (1) by determining a target plastic deformation (s_soll) at a forming position (12) of the bar-shaped material (1), moving a straightening hammer (8) with integrated measuring probe (7) to the forming position (12), a first forming stroke (h_1) of the straightening hammer (8) is carried out, an actual plastic deformation (s_ist) caused by the first forming stroke (h_1) is determined by means of the integrated measuring probe (7), a second forming stroke (h_2) is determined from the actual plastic deformation (s_ist) caused by the first forming stroke (h_1) and the target plastic deformation (s_soll).

Claims

1. A method for straightening non-straight bar-shaped material (1), in that a target plastic deformation (s_soll) is determined at a forming position (12) of the bar-shaped material (1), a straightening hammer (8) with integrated measuring probe (7) is moved to the forming position (12), a first forming stroke (h_1) of the straightening hammer (8) is carried out, an actual plastic deformation (s_ist) caused by the first forming stroke (h_1) is determined by means of the integrated measuring probe (7), a second forming stroke (h_2) is determined from the actual plastic deformation (s_ist) by the first forming stroke (h_1) and the target plastic deformation (s_soll).

2. The method according to claim 1, characterised in that a characteristic diagram (60) is provided which indicates a plastic deformation span (b) for the material for each forming stroke (h).

3. The method according to claim 2, characterised in that the target deformation (s_soll) within the upper 10% of the deformation span (b) is preferably selected as the maximum value of the deformation span (b) of the first forming stroke (h_1).

4. The method according to claim 1, characterised in that an elastic deformation of the material and the actual plastic deformation (s_ist) within a deformation span (b) is carried out by the first forming stroke (h_1).

5. The method according to claim 2, characterised in that the first forming stroke (h_1) is selected such that a deformation span (b) associated therewith has a maximum value corresponding to the target deformation (s_soll), and the actual deformation (s_ist) generated by the first forming stroke (h_1) defines a characteristic curve (61) within the characteristic diagram (60), and the characteristic curve (61) is selected for determining the second deformation stroke (h_2).

6. The method according to claim 1, characterised in that the target deformation (s_soll) is determined at the forming position (12) of the bar-shaped material (1), the bar-shaped material (1) is clamped, a zero position of the straightening hammer (8) is determined, a first measured value of the integrated measuring probe (7) is determined in the zero position of the straightening hammer (8), the first forming stroke (h_1) of the straightening hammer (8) is executed, the straightening hammer (8) is moved back to the zero position, a second measured value of the measuring probe (7) is determined in the zero position of the straightening hammer (8) and the actual plastic -deformation (s_ist) of the bar-shaped material (1) by the first forming stroke (h_1) is determined from the first and second measured values, the actual plastic deformation (s_ist) is compared with the target plastic deformation (s_soll).

7. The method according to claim 1, characterised in that a tolerance range is specified and if, after the first forming stroke (h_1) has been carried out, a difference between the actual deformation (s_ist) and the target deformation (s_soll) lies outside the tolerance range, the second forming stroke (h_2) is carried out at the forming position (12).

8. The method according to claim 1, characterised in that a characteristic curve (61) of the bar-shaped material (1) within a characteristic diagram (60) is determined from the actual deformation (s_ist) after the first forming stroke (h_1) and the second forming stroke (h_2) is determined from the characteristic curve (61) in that the second deformation stroke (h_2) corresponds to a deformation stroke (h) to the target plastic deformation (s_soll) along the characteristic curve (61).

9. The method according to claim 1, characterised in that an actual outer surface of the bar-shaped material (1) is measured and a deviation profile of the actual outer surface from a straight-line target outer surface is determined, the forming position (12) is determined from the deviation profile.

10. The method according to any of the preceding claim 1, characterised in that the forming position (12) is determined from the deviation profile as an angle (?, ?) about a longitudinal direction (L) of the bar-shaped material (1) and as a position along a travel axis (G) of the straightening hammer (8) along the longitudinal direction (L).

11. The method according to claim 1, characterised in that the bar-shaped material (1) is placed on two anvils (5, 6) spaced apart from each other and the forming position (12) is arranged in longitudinal direction (L) between the two anvils (5, 6).

12. A straightening machine for non-straight, bar-shaped material (1) for carrying out a target plastic deformation (s_soll) at a forming position (12) of the bar-shaped material (1) with a control for a traversing device with a straightening hammer (8) with integrated measuring probe (7), with a memory for a characteristic diagram (60) which indicates an actual plastic deformation span (b) for the material for each forming stroke (h), whereby the control determines a first forming stroke (h_1) from the target deformation (s_soll), the integrated measuring probe (7) measures an actual plastic deformation (s_ist) caused by the first forming stroke (h_1) and feeds its measured values to the control via a data-conducting connection, a characteristic curve (61) within the characteristic diagram (60) can be determined from the actual deformation (s_ist) in the control system and a second forming stroke (h_2) can be determined by the control from the target deformation (s_soll) and the characteristic curve (61).

13. The straightening machine according to claim 12, characterised by at least two anvils (3, 4) spaced from each other in a longitudinal direction (L) for supporting the bar-shaped material (1).

14. The straightening machine according to claim 12, characterised in that the integrated measuring probe (7) with a measuring head (7a) is guided centrally through the straightening hammer (8) and the measuring head (7a) enables a distance measurement beyond an impact surface (8a) of the straightening hammer (8).

15. The straightening machine according to claim 12, characterised in that the integrated measuring probe (7) is a tactile measuring probe, the measuring head (7a) of which projects centrally from a bore of the straightening hammer (8) and can be returned completely on the inside behind the striking surface (8a) of the straightening hammer (8).

16. The straightening machine according to claim 12, characterised in that the straightening hammer (8) is arranged on a traversing axis (H) which can be NC-controlled transversely to the actual outer surface of the bar-shaped material.

17. The straightening machine according to claim 12, characterised in that a measuring system for measuring an outer surface of the bar-shaped material (1) is arranged along a receptacle (16) for the bar-shaped material (1).

18. The straightening machine according to claim 17, characterised in that the measuring system comprises oppositely arranged, rotatable holders (5, 6) for clamping the bar-shaped material (1) and measuring probes (2) arranged between the holders (5, 6), which are arranged next to the clamped bar-shaped material (1).

Description

[0048] The invention is described by means of an embodiment example in six figures. Thereby show:

[0049] FIG. 1 a schematic construction of a straightening machine according to the invention for non-straight, bar-shaped material,

[0050] FIG. 2 the straightening machine for non-straight, bar-shaped material of FIG. 1 in a first process step,

[0051] FIG. 3 the straightening machine for non-straight bar-shaped material of FIG. 1 in a second process step,

[0052] FIG. 4 the straightening machine for non-straight, bar-shaped material according to FIG. 1 in a third process step,

[0053] FIG. 5 the straightening machine for non-straight bar-shaped material according to FIG. 1 in a fourth process step,

[0054] FIG. 6 a map.

[0055] A straightening machine 10 shown schematically in FIGS. 1 to 5 and the process according to the invention carried out on the straightening machine 10 are used for straightening non-straight, bar-shaped material. By bar-shaped material is meant here in particular tubes, profiles, solid profiles etc. extending along a longitudinal direction L, which may preferably be circular in cross-section, but also angular, in particular square.

[0056] The embodiment example refers to a tube 1 without, however, being limited to it in any way. The tube 1 can have a length of several metres and diameters of several centimetres or decimetres. Other dimensions are also conceivable.

[0057] When viewed roughly, the tube 1 appears straight in the longitudinal direction L along its actual outer surface 11. On closer inspection, and this is the point of the present invention, the tube 1 is not straight.

[0058] The tube 1 shown in FIG. 1 is, for example, wave-shaped in a Y-direction. The wave form is not shown to scale here, but is greatly exaggerated. Usually, amplitudes of the waves formed in the tube are in the mm range or below for tube lengths of one to two metres. The wave extends along the longitudinal direction L, which here corresponds to the Z-direction. Wavelike bulges can also occur in an X-direction (not drawn in), which are superimposed on the waveform in the Y-direction. The bulges do not have to be wave-shaped.

[0059] The tube 1 has the actual outer surface 11, which deviates from the straight target outer surface extending in the longitudinal direction L. The deviation profile can be determined along the longitudinal direction L. A deviation profile can be determined along the longitudinal direction L by forming the difference between the actual outer surface and the target outer surface. For this purpose, the straightening machine 10 has a receptacle 16, on the end faces of which tool tips 5, 6 are arranged for tube clamping and tube rotation. The receptacle 16 can have a preferably conical support surface for supporting the tube 1. Here, the receptacle 16 is to be understood as the clearance between the two tool tips 5, 6. The tool tips 5, 6 are individually movable back and forth along traversing axes A and B, respectively, which are both arranged in the Z-direction. The tool tips 5, 6 can also be moved individually in the X-Y plane in FIG. 1. In FIG. 1 a traversing axis C is drawn for one tool tip 5 and a traversing axis D for the other tool tip 6, both running in the Y-direction. The two traversing axes in the X-direction of the two tool tips 5, 6 are not drawn. The two tool tips 5, 6 are arranged exactly opposite each other so that their axes of rotation run in extension of each other. The tube 1 can be clamped between them by moving the tool tips 5, 6 towards each other. The clamped tube 1 can itself be rotated by rotating the tool tips 5, 6.

[0060] Along the receptacle 16 located between the tool tips 5, 6, measuring probes 2 for measuring the straightness of the tube 1 are arranged at a distance from each other along the longitudinal direction L. The distance can be equidistant. The distances from each other can be equidistant. Different distances can also be selected. The probes 2 may also be arranged in cross-section perpendicular to the longitudinal direction L around the receptacle 16 and the tube 1 at different angles. The measuring probes 2 may be tactile or optical or otherwise designed. They enable distance measurements in the range with an accuracy of 0.1 pm or less. The measuring probes 2 for measuring the straightness of the tube 1 are connected in a data-conducting manner to a control system with a data memory in which, in particular, measured distance values of the individual measuring probes 2 to measuring points on the outer surface 11 of the tube 2 are stored. The straightness of the tube 1 is measured in such a way that the tube 1 is clamped as shown in FIG. 1, the measuring probes 2 each carry out a first distance measurement, the tube 1 is rotated a short distance by an angle ?, ?, the measuring probes 2 carry out a second distance measurement in the rotated angular position, the tube 1 is rotated by a further angle ?, ? and the measuring probes 2 carry out a third distance measurement, and so on. The distance measurement values are stored and evaluated together with the position of the probe 2 along the longitudinal direction L and the angular position, and the actual outer surface 11 of the tube 1 is determined. The actual outer surface 11 of the tube 1 deviates from the straight target outer surface of the tube 1. In FIG. 1 the tube 1 is shown exaggeratedly curved.

[0061] Usually, deviations from straightness with a predefined tolerance of 1 ?m or less are tolerated for further processing of the tubes 1. Non-straightness outside the tolerance range is sorted out and straightened according to the invention. The tube 1 is straightened by the straightening machine 10 according to the invention to get back within the tolerance range.

[0062] The straightening of the tube 1 is preferably carried out with the aid of two anvils 3, 4, which are shown schematically in FIG. 1, and by means of a straightening hammer 8 according to the invention, in which an integrated measuring probe 7 is arranged centrally. The straightening hammer 8 is a cylindrical structure with a central bore, preferably a central circular bore, in which the tactile or optical integrated measuring probe 7 is preferably embedded. The integrated measuring probe 7 can be moved back and forth along a vertical travel axis J within the straightening hammer 8 relative to the straightening hammer 8 and can disappear in the straightening hammer 8 with a measuring surface 7a aligned with a striking surface 8a of the straightening hammer 8.

[0063] The integrated measuring probe 7 is mounted in the straightening hammer 8 with a return spring 15, which pushes the measuring surface 7a out of the striking surface 8a in the load-free state.

[0064] According to FIG. 1, the straightening hammer 8 can be moved along a vertical traversing axis H towards and away from the tube 1, it can be moved along a horizontal traversing axis G along the longitudinal direction L of the tube 1 and can also be moved along a (not drawn) horizontal traversing axis perpendicular to the longitudinal direction L. The measuring surface 7a of the measuring probe 7, as shown in FIG. 1, can also be moved parallel to the traversing axis H of the straightening hammer 8, preferably very easily, i.e. almost without resistance.

[0065] FIG. 2 shows the arrangement of the straightening hammer 8, the measuring probe 7 as well as the two anvils 3, 4 and the tube 1 clamped between the tool tips 5, 6 immediately before straightening. The two anvils 3, 4 can be moved back and forth along the longitudinal direction L along traversing axes E, F.

[0066] From the deviation profile of the actual from the target outer surface of the tube 1, a forming position 12 of the straightening hammer 8 on the tube 1 and support points 13, 14 of the tube 1 on the anvils 3, 4 and thus calculates positions of the traversing axis G and angles ?, ? of the two angular tips 5, 6 and the required target deformations of the tube 1 at the forming position 12 in order to straighten the tube when the tube 1 is supported between the two anvils 3, 4 spaced at a certain distance from each other.

[0067] The problem is that the target deformation at the forming position 12 of the tube 1 and a forming stroke h of the straightening hammer 8 cannot be clearly assigned to each other.

[0068] The straightening process in the prior art is basically always the same process. In order to plastically deform the tube 1, it is first necessary to exert the forming stroke h on the tube 1 with the straightening hammer 8 and to exceed the elastic range of deformation. Only after the elastic deformation does a plastic deformation s take place. The forming stroke h of the straightening hammer 8 must basically correspond to the elastic deformation plus the plastic deformation s. When the straightening hammer 8 is moved back again and the tube 1 is unloaded, the elastic deformation component essentially springs back and only the plastic deformation component remains, which here also corresponds to the actual plastic deformation s_ist.

[0069] It is known in principle how large the plastic deformation s at the forming position 12 should be in order to achieve sufficient straightness of the tube 1 by straightening. However, no function between the elastic deformation component and the plastic deformation component of the forming stroke h is known. The function between elastic deformation component and plastic deformation component depends on many conditions, especially on the properties of the material, work hardening or other material variations. However, they are so different that even within a length of a tube 1 the function between elastic portion and plastic portion is not predictable. It is therefore not known with certainty which forming stroke h must be performed by the straightening hammer 8 in order to achieve a target deformation s_soll. Although statistical methods can be used to predict the possible forming stroke h, there is then also a considerable probability that the tube 1 will be plastically deformed too much or too little. If overforming occurs, the tube 1 would have to be measured again, lifted off the anvils 3, 4, rotated and put down again, and straightened again. This is time-consuming.

[0070] FIG. 6 schematically shows the idea of the procedure carried out in FIGS. 2, 3, 4, 5. FIG. 6 first shows a given characteristic diagram 60, which can be obtained by statistical methods in connection with artificial intelligence, machine learning, etc., for example according to Deep Learning with Python and Keras (ISBN 978-3-95845-838-3). There, the statistical connection between the forming stroke h of the straightening hammer 8 and the plastic deformation s generated by the forming stroke h for a certain material is shown. The distances between the two anvils 3, 4 and the position of the straightening hammer 8 are also included in the characteristic diagram 60. The characteristic diagram 60 is to be read in such a way that, when a first forming stroke h_1 is carried out, an actual plastic deformation s_ist is within a deformation span b along the X-axis within the characteristic diagram 60. The actual plastic deformation s_ist is located within the deformation span b with a probability of 95%, 99%, 99.9%. The width of the characteristic diagram 60, i.e. the length of the deformation span b in the X-direction, depends primarily on the material properties. The width depends in particular on residual stresses in the material, strain hardening or other material fluctuations. On the other hand, although the global shape of the characteristic diagram 60 also depends on how far apart the anvils 3, 4 are from each other, what diameter the tube 1 has, what wall thickness the tube 1 has, etc., these are all parameters that allow an exact bending behaviour to be predicted and do not significantly influence the width of the characteristic diagram 60 as such. They only influence the global shape, i.e. the gradient of the characteristic diagram 60, etc.

[0071] Furthermore, it is known that the actual deformation s_ist of a bar-shaped material, in particular of the tube 1, which is subjected to a different first forming stroke h at a forming position 12, follows a characteristic curve 61 which moves within the characteristic diagram 60 shown in FIG. 6. The characteristic curve 61 is inserted into the characteristic diagram 60. It has been found that the characteristic curve 61 within the characteristic diagram 60 can also be precisely specified in real terms by two points.

[0072] The process according to the invention proceeds as described below.

[0073] The tube 1 is positioned on the anvils 3, 4 at a certain angle ?, ? in a known manner according to FIG. 2. The forming position 12 of the straightening hammer 8 and the support points 13, 14 on the anvils 3, 4 are known. In a first process step according to FIG. 2, the straightening hammer 8 is arranged above the forming position 12 by means of the traversing axis G. The straightening hammer 8 is positioned on the anvils 3, 4. It is known how large the target plastic deformation s_soll at the forming position 12 must be in order to be able to provide a tube 1 that is as straight as possible after the straightening process.

[0074] In a second process step, as shown in FIG. 3, the straightening hammer 8 is moved along the traversing axis H in the direction of the forming position 12 of the tube 1 until the measuring surface 7a of the probe 7 touches the outer surface of the tube 1. However, the probe 7 does not exert any pressure on the forming position 12 which would already bend the tube. The straightening hammer 8 is in the zero position. The zero position is determined and its coordinates are recorded. A first measurement is now carried out in the zero position by the measuring probe 7 and the first measured values of the measuring probe 7 are stored. For example, the measurement data is recorded as to how far away the measuring surface 7a of the measuring probe is from the striking surface 8a in the Y-direction or a similar measurement. The first measurement values are measurement values that determine the distance between the forming position 12 and the striking surface 8a of the straightening hammer 8. However, this need not be so, it is only important that the position of the forming position 12 relative to the straightening hammer 8 is recorded.

[0075] In a third process step, the first forming stroke h_1 is applied to the forming position 12 as shown in FIG. 4.

[0076] The first forming stroke h_1 is determined in advance from the known target deformation s_soll at the forming position 12. For this purpose, the intersection of the target deformation s_soll with the lower, minimum limit of the characteristic diagram 60 is determined according to FIG. 6. The intersection point determines the first forming stroke h_1. The selected first forming stroke h_1 statistically generates a target deformation s_soll in the deformation span b for the material. Through the first forming stroke h_1, the target deformation s_soll is only achieved in the best case. If this is not the case, an actual deformation s_ist is produced which is below the target deformation s_soll within the deformation span b. The tube 1 is therefore deformed less than it should actually be deformed.

[0077] The deformation process is carried out as shown in FIG. 4 by the straightening hammer 8, which is firmly mounted on an NC-controllable axis H. The straightening hammer 8 is moved by the first forming stroke h_1 in the opposite direction to the Y-direction. The straightening hammer 8 is moved against the Y-direction by the first forming stroke h_1 by means of the NC-controllable axis H as shown in FIG. 4 and bends the tube 1 to some extent as shown in FIG. 4. The bending contains an elastic and a plastic part.

[0078] In FIG. 5 the straightening hammer 8 has moved back again and the elastic deformation has receded. The plastic deformation s has remained and straightens the tube 1.

[0079] The information acquisition according to the invention is carried out by the measuring probe 7. Then, in a fourth process step, the straightening hammer 8 is moved back according to FIG. 5, the tube 1 is relieved, the straightening hammer 8 is moved back to the zero position according to FIG. 3, and a second measurement is carried out by means of the measuring probe 7, and second measured values are determined. The second measured values are compared with the first measured values of the measuring probe 7, and from the difference of the measured values, for example the difference of the distances of the forming position 12 from the striking surface 8a of the straightening hammer 8, the actual deformation s_ist is determined after the first forming stroke h_1.

[0080] The inventive idea is to use the information about the first actual deformation s_ist to narrow down the characteristic diagram 60 considerably in order to be able to execute a second forming stroke h_2 much more precisely and to get very close to the target deformation s_soll.

[0081] The actual plastic deformation s_ist after the first forming stroke h_1 does not usually correspond to the target plastic deformation s_soll, but is lower than the target deformation s_soll. However, the measurements of the measuring probe 7 allow to indicate a concrete value for the actual deformation s_ist which was generated by the first forming stroke H_1, so that according to FIG. 6 an actual deformation s_ist which actually took place can be assigned to the first forming stroke h_1, and thus the characteristic curve 61 within the characteristic diagram 60 in FIG. 6 can be assigned to the forming position 12 with its specific material properties. The characteristic curve 61 shows the plastic deformation behaviour at different strokes h for the forming position 12.

[0082] In a further process loop, according to FIGS. 3, 4, 5, the tube 1 is straightened at the forming position 12 by means of the second forming stroke h_2. The size of the second forming stroke h_2 is determined from the characteristic curve 61 in FIG. 6 and its point of intersection with the target deformation s_soll.

[0083] If necessary, the process loop can also be carried out a third or fourth time. In the real implementation of the process, it has been shown that several process loops are necessary. However, it has also been shown that specified straightness tolerances can be maintained with a high degree of certainty by this process, which iteratively approaches the target deformation s_soll.

LIST OF REFERENCE SIGNS

[0084] 1 Tube/rod-shaped material

[0085] 2 Probes

[0086] 3 Amboss

[0087] 4 Amboss

[0088] 5 Tool tip

[0089] 6 Tool tip

[0090] 7

[0091] 7a Measuring surface

[0092] 8 Judging hammer

[0093] 8a Stroke surface

[0094] 10 Straightener

[0095] 11 Actual external surface

[0096] 12 Forming position

[0097] 13 Support point

[0098] 14 Support point

[0099] 15 Return spring

[0100] 16 Receptacle

[0101] 60 Known field

[0102] 61 Characteristic

[0103] b Deformation span

[0104] h Forming stroke

[0105] h_1 First forming stroke

[0106] h_2 Second forming stroke

[0107] s Plastic deformation

[0108] s_ist Plastic deformation

[0109] s_soll Target deformation

[0110] A

[0111] B

[0112] Travel axis

[0113] Travel axis

[0114] C Travel axis

[0115] D Travel axis

[0116] E Travel axis

[0117] F Travel axis

[0118] G vertical travel axis

[0119] H horizontal travel axis

[0120] J Travel axis

[0121] L Longitudinal direction

[0122] ? Angle

[0123] ? Angle