EP2110266A2 - Method and device for creating a marking in a workpiece surface through impression - Google Patents

Abstract

The method involves pressing a stamping needle (18) in a work piece surface, moving the needle parallel with the surface, and determining resultant stamping depth of a symbol using a distance sensor. The sensor is mounted on the needle and moved with the needle. The needle is placed on the surface before the stamping begins. Resultant distance between the sensor and the surface is measured. The needle is subsequently pressed into the surface. Another resultant distance between the sensor and the surface is measured. Stamping depth is determined based on a difference between the two distances. An independent claim is also included for a device for creating a symbol in a work piece surface via stamping.

Description

The invention relates to a method and an apparatus of the genera specified in the preambles of claims 1 and 5.

The generation of characters such. As alphanumeric characters in workpiece surfaces used for example in the automotive industry the purpose of workpieces such as chassis, motors od. Like. To provide with largely forgery-proof markers in the form of labels or other markings. As embossing tools embossing needles are used for this purpose, either the characters composed in a matrix of a plurality of points (needle embossing) or in plain writing by the embossing needle is pressed into the workpiece surface and then moved across it (scratch marking or embossing by pressure forming).

In the two last-mentioned cases in which the individual characters are formed as continuous, substantially V-shaped scribe lines or grooves, in order to achieve a well readable, uniform typeface, it is increasingly required that the characters have a uniform, hereinafter abbreviated as embossing depth Have scoring or groove depth z. B. is 0.2 mm. As a visual Final check of the embossing depth is practically impossible and the embossing devices commonly used not ensure that a given embossing depth is actually achieved and adhered to, methods and devices of the types described are required by means of which the embossing depth automatically determined and compliance with a preselected embossing depth are automatically ensured can.

Known methods and devices of the generic types described initially use optical means for determining the embossing depth (eg. DE 199 30 272 A1 . DE 10 2005 037 411 A1 ), the od with laser light sensors. Like. Have. The disadvantage here is that a measurement of the embossing depth actually achieved is possible only in a subsequent operation on the embossing and prone to contamination, in particular the inevitable in scratch marking ejection of the displaced material. The embossing depths obtained therefore do not correspond with sufficient certainty to the prescribed nominal values. It is also known to first determine the distance of the embossing needle from the workpiece surface by means of a capacitive proximity sensor and then advance the embossing needle in the direction of the workpiece surface. This method does not allow high accuracy because the workpiece, if it is z. B. is formed as a sheet metal, can bend during the embossing process and then leads to an embossing depth that is smaller than the desired embossing depth.

Finally, it would be possible to check the embossed markings with the help of a camera. As a result, however, can usually only be determined whether the desired characters are actually present. In addition, e.g. existing dirt particles (ejection), changing light conditions and different colors of the workpieces unfavorable to the measurement results, which is why poor availability is achieved with these methods and devices.

Proceeding from this, the technical problem underlying the invention is to further develop the method and the device of the generic types described at the beginning in such a way that a rapid determination taking place during the stamping process and with high accuracy is carried out the embossing depth is possible and thus incorrectly marked workpieces are largely avoided.

This problem is solved according to the invention with the characterizing features of claims 1 and 5.

The invention has the advantage that the distance sensor, since it is moved together with the needle perpendicular and parallel to the workpiece surface, constantly indicates its distance from the workpiece surface during the embossing process, including one at the beginning of the embossing process and the rest of the embossing needle At the same time, the reference value determined on the workpiece surface supplies an exact measure of the current embossing depth. The closer the Abstandssenor is arranged on the embossing needle, the more accurate is the determined embossing depth, since in this way a possible deflection of the workpiece is neutralized. Finally, the influence of any wear of the embossing needle can be largely compensated by determining a new reference value before the generation of each character.

Further advantageous features of the invention will become apparent from the dependent claims.

• Fig. 1 eine schematische, perspektivische Ansicht einer Prägeeinheit zur Durchführung von Ritzmarkierungen;
• Fig. 2 eine perspektivische Ansicht eines Nadelkopfes der Prägeeinheit nach Fig. 1;
• Fig. 3 den Nadelkopf nach Fig. 2 in einer teilweise aufgebrochenen und geschnittenen Darstellung;
• Fig. 4 eine perspektivische Darstellung einer mit einem optischen Sensor versehenen Einrichtung zur Erfassung von Relativbewegungen zwischen der Prägeeinheit und den Werkstück;
• Fig. 5 und 6 das der Erfindung zugrundeliegende Messprinzip für die Prägestufe anhand je einer Vorderansicht der Prägenadel und eines Abstandssensors;
• Fig. 7 eine Regeleinrichtung zur Regelung der Prägetiefe mittels der Prägeeinheit nach Fig. 1 bis 5;
• Fig. 8 eine Einrichtung zur Überwachung der Bewegung der Prägenadel parallel zu einer Werkstückoberfläche; und
• Fig. 9 und 10 eine perspektivische Darstellung und eine Vorderansicht einer mit einem mechanischen Taster versehenen Einrichtung zur Erfassung von Relativbewegungen zwischen der Prägeeinheit und dem Werkstück.

The invention will be explained in more detail below in connection with the accompanying drawings of an embodiment. It shows in different scales:

• Fig. 1 a schematic, perspective view of a stamping unit for performing scribe marks;
• Fig. 2 a perspective view of a needle head of the embossing unit according to Fig. 1 ;
• Fig. 3 follow the needle head Fig. 2 in a partially broken and cut representation;
• Fig. 4 a perspective view of a device provided with an optical sensor for detecting relative movements between the embossing unit and the workpiece;
• FIGS. 5 and 6 the measurement principle underlying the invention for the embossing stage based on a respective front view of the embossing needle and a distance sensor;
• Fig. 7 a control device for controlling the embossing depth by means of the embossing unit according to Fig. 1 to 5 ;
• Fig. 8 means for monitoring movement of the embossing needle parallel to a workpiece surface; and
• FIGS. 9 and 10 a perspective view and a front view of a device provided with a mechanical button for detecting relative movements between the embossing unit and the workpiece.

Fig. 1 shows a device in the form of an embossing unit 1 for producing markings according to the method of the so-called scratch marking. The embossing unit 1 includes a base frame, of which in Fig. 1 only an upper cover plate 2, a parallel side wall 2a and a side wall 3 are shown. The base frame is in the usual way on a handling system such. B. a robot arm mounted in order to put the embossing unit 1 to that point of a workpiece surface can, at which a mark is to be attached. At the intermediate wall 2a of the base frame at least one parallel to a Y-axis of an imaginary coordinate system extending guide 4 is fixed, along which a only schematically indicated Y-slide 5 back and forth. At an underside of the Y-carriage 5 at least one parallel to the X-axis of the imaginary coordinate system extending guide 6 is mounted, along which an X-carriage 7 is mounted back and forth. The movement of the Y-carriage 5 is z. B. by means of a base frame attached to the stepping motor 8, by means of a toothed belt pulley 9 and a timing belt, not shown, a toothed belt pulley 10 drives, which sits on a threaded spindle which projects through a threaded bore of the Y-carriage 5. In a corresponding manner, the X-carriage 7 z. B. by means of a stepping motor 11 which is fixed by means of a mounting plate 12 on the Y-carriage 5 and a toothed belt pulley 14 which can put a toothed belt pulley 15 in revolutions by means of a toothed belt, not shown. This is mounted on a rotatably mounted in the mounting plate 11 threaded spindle 16 which extends through a threaded bore of the X-carriage 7.

At the bottom of the X-carriage 7, a stamping or needle head 17 is fixed, in which an embossing needle 18 is movably mounted and parallel to the Z-axis of the imaginary coordinate system can be moved back and forth.

Incidentally, the embossing unit 1 described so far can be designed in such a way as corresponds to the general state of the art. Therefore, in particular, the stepping motors 8 and 11, as is common in the case of XY tables, can be rotated in rotation with control units, not shown, in such a way that the embossing needle 18 in the X and Y directions along the surface of an in Fig. 1 Unillustrated workpiece is moved to write one or more characters and form by a scratching operation in the workpiece surface. Since such controls are familiar to those skilled in the art, their detailed description is omitted.

FIGS. 2 and 3 show details of the attached to the X-carriage 7 needle head 17. This contains in an upper part of a holding plate 19, on the underside of a housing 20 is fixed, which surrounds a preferably cylindrical cavity 21. In the cavity 21 as a means for pressing the embossing needle 18 in the workpiece surface, a likewise preferably cylindrical piston 22 is slidably mounted in the Z direction, which forms a cylinder / piston arrangement together with the housing 20. An in Fig. 3 the upper end of the cavity 21 is closed by a cover wall 24 having a through opening 23. The opening 23 serves, via a connected to it, not shown line a pressure medium, preferably to introduce compressed air into the cavity 21 and thereby act on the piston 22.

On the side facing away from the opening 23 of the piston 22, a bottom part 25 is fixed, which has a coaxial with the piston 22, extending in the Z direction guide bore 26. In the guide bore 26 guide lugs 27 are slidably mounted with sliding fit, which are provided on a piston 22 fixed to the piston rod 28, at the lower end of the embossing needle 18 is preferably secured easily replaceable (see also FIGS. 5 and 6 ). A loose surrounding the piston rod 28 ring 29 rests on a formed at a transition from the cavity 21 to the guide bore 26 shoulder and supports the lower end of a compression spring 30, the upper end of the piston 22 abuts. As a result, the piston 22 in Fig. 3 upwardly biased to a starting position, from which it by means of the introduced through the opening 23 into the cavity 21 pressure medium in the Z direction and in Fig. 3 can be advanced down.

In a lower portion of the piston rod 28, a radially extending bracket 31 is fixed, which by a lateral recess 32 (FIG. Fig. 2 ) of the bottom part 25 protrudes to the outside. In this holder 31, a parallel to the embossing needle 18 extended distance sensor 33 is fixed, wherein the recess 32 is formed so that the holder 31 and thus the distance sensor 33 can join all occurring in the Z direction movements of the embossing needle 18. The lower end of the distance sensor 33 has a distance A from the underside or tip 18a of the embossing needle 18, (FIG. Fig. 3 ) which is at least as large as corresponds to the desired embossing depth of the characters to be produced. Preferably, the distance A is also so much greater than the embossing depth, as corresponds to a tolierbaren wear of the embossing tip 18a in use. It is thereby achieved that the distance sensor 33 is always arranged above a workpiece surface and therefore does not touch it, even if the embossing needle 18 is pressed into the workpiece surface with the maximum embossing depth.

Fig. 4 shows a workpiece 34 with a surface to be labeled 34a and in To simplify the deposition of the embossing unit 1 by means of a robot arm od. Like. On the surface 34a such that the embossing needle 18 by means of X and Y slides not shown here 7 and 5 parallel to the surface 34a along a to be provided with signs Labeling zone 35 can be moved back and forth. The bottom part 25 expediently penetrates through a recess 36 formed in a bottom of the base frame. On a side wall 3 opposite another side wall 3a of the base frame of the embossing unit 1, a sensor 37 is arranged, the z. B. is an optical sensor, emits a directed onto the surface 34 a light beam and receives a reflected light from the surface 34 a. On the basis of the sensor signals obtained in this way can be determined in the manner of a motion detector, whether the embossing unit 1 moves during a stamping phase in the X and / or Y-direction relative to the workpiece 34 or if no such relative movement takes place as required. If necessary, the embossing process can be interrupted and provided for a shift-free storage of the embossing unit 1 on the workpiece 34.

FIGS. 5 and 6 show how, by means of the distance sensor 33, an exact measurement of the embossing depth can be made if the surface 34a is marked by scratches with a mark 34b (FIG. Fig. 6 ) should be provided. Before the start of the scribing process, the embossing needle 18 is first characterized in that the piston 22 ( Fig. 3 ) is acted upon by the opening 23 through a first, relatively low pressure, advanced in the Z direction so far that it sits with its tip 18a on the surface 34a, without penetrating into it. Reaching this state can z. B. by means of a sensor, not shown, for. B. a speed sensor, an electrical, the contact between the tip 18 a and the surface 34 a indicative contact sensor od. The like., To be assigned to the piston 22 or the piston rod 28 and outputs a signal when the speed v = 0 accordingly the stoppage of the embossing needle 18 is reached or a contact takes place. Alternatively, the pressure of the printing medium can also be chosen so that, although a touch, but no penetration of the embossing needle 18 in the surface 34 a is possible, and a predetermined time to wait, within which the Embossing needle 18 is securely placed on the workpiece surface 34a. The final state obtained is in Fig. 5 in which the distance sensor 33 (or its underside facing the surface 34a) shows a first distance L1 from the workpiece surface 34a.

In a next method step, the pressure of the pressure medium introduced through the opening 23 is now increased so much that the tip 18a of the embossing needle 18 correspondingly Fig. 6 penetrates into the surface 34a to a desired embossing depth L3. When this stamping depth L3 is reached, the distance sensor 33 outputs a signal L2 which corresponds to the value L2 = L1-L3. It follows that the current embossing depth L3 is always equal to the difference L1 - L2. Therefore, when the distance L1 measured on the surface 34a when the embossing needle 18 is set is used as a reference value in the subsequent formation of a character 34b by scribing, the difference L3 = L1-L2 at each position of the image character 34b gives the current actual value of the embossing depth at. Consequently, it is possible according to the invention to not only permanently measure the current embossing depth L3 during an embossing process, but also to modify it, if necessary, by controlling the pressure acting on the piston 22. A provision of the embossing needle 18 in a direction away from the workpiece surface 34 a direction is effected in each case by the compression spring 30.

In a presently considered best mode for carrying out the invention, the difference L3 = L1-L2 will be used as a control variable for a pressure indicative of the piston 22 in FIG Fig. 7 used simplified control device. The control device includes a regulator 38, a connected thereto adjusting device 39, for example in the form of a pressure control valve, which in one with the opening 23 (FIG. Fig. 1 ) is connected and controls the pressure of the force acting on the piston 22 pressure medium, and acted upon by the actuator 39 embossing needle 18 which is fixedly connected to the distance sensor 33. The signal output by the distance sensor 33 is supplied to a comparator 40, in which it is compared with a predetermined, output from a setpoint generator 41 setpoint. The difference signal resulting from the comparison is supplied to the controller 38.

During operation of the embossing unit 1, the control device preferably operates as follows:

Before embossing a mark 34b, the embossing needle 18 is first placed on the workpiece surface 34a under the control of the stepping motors 8 and 11 as described, where the embossing operation is to begin. He is doing according to Fig. 5 resulting distance L1 (eg 1 mm), is taken as a reference value in the setpoint generator 41 and modified there to a target value for the embossing process, which corresponds to the difference L2 = L1 - L3, wherein L3 is a fixed preset value for the embossing depth , Subsequently, the embossing process is started by the control device after Fig. 7 is turned on, whereby the current output signal of the distance sensor 33 is compared in the comparator 40 with the setpoint L1 - L3. The difference signal supplied to the controller 38 controls the Stelleinrichtug 39, z. B. the pressure control valve for the cylinder / piston assembly 21, 22 ( Fig. 3 ), in such a way that the embossing needle 18 to the desired embossing depth L3 ( Fig. 6 ) penetrates into the workpiece surface 34a. As soon as the distance sensor 33 indicates this by the fact that its output value corresponds to the distance L2, the Y and X motors 8 and 11 (FIGS. Fig. 1 ) is turned on to write the relevant character 34b into the surface 34a.

After completion of the embossing process, the embossing needle 18 is lifted by venting the cylinder / piston assembly 21, 22 by means of the compression spring 30 from the workpiece surface 34a and successively brought to the starting points for the next character, the process steps described are respectively repeated accordingly. A particular advantage of the invention is therefore that the determination of the reference value L1 can be made anew before the embossing of each individual character. Even if the embossing needle 18 slightly wears during embossing of a character or the distance between the tip 18a and the bottom of the sensor 33 should have changed for some reason, the next character is still scribed with the predetermined embossing depth, since in this case the reference value L1 changes accordingly and the differential value formed in the setpoint generator 41 is adjusted accordingly. In this way, the embossing depth L3 at least as long as kept absolutely constant until the embossing needle 18 is worn to a no longer tolerable value.

A further advantage of the invention results from the fact that any deflections of the workpiece 34 are also included in the formation of the reference value L1. Namely, if the workpiece 34 is slightly deflected by the embossing needle 18 before it penetrates into the surface 34a, the reference value L1 required for the control does not change because the distance sensor 33 constantly participates in the movements of the embossing needle 18. Therefore, it is particularly advantageous if the distance sensor 33 as close as possible, d. H. as close as the installation conditions permit, is arranged next to the embossing needle 18. Any deformations of the workpiece 34 then have at most a negligible effect on the reference value L1.

As a result of the invention, it can thus be ensured even during an embossing phase that a predetermined embossing depth L3 is actually achieved and maintained. If, for some reason, the embossing depth L3 assumes a value outside a predetermined tolerance range, which can be monitored by the comparator 40, then the embossing process is preferably interrupted in order to preclude the attachment of defective markings on the workpiece surface 34a.

The basis of the Fig. 4 Monitoring monitoring movements of the embossing unit 1 relative to the workpiece 34 further ensures that the embossing process is not disturbed by a poor assembly of the embossing unit 1 on the workpiece 34.

Finally, in a development of the invention, it is also ensured that the various characters are attached to the predetermined X and Y positions and formed as intended. For this purpose, it is provided on the guides 4 and 6 themselves or a parallel part of the base frame or the Y-slide 5, as in Fig. 8 is exemplified for the guide 6, a z. B. by bar marks 42 or otherwise scaled scale 43 to attach and assign this one on the corresponding carriage, here the X-carriage 7, mounted sensor 44. When moving the X-carriage 7 of the sensor counts 43 z. The number of bar marks reached is compared with the setpoint specification for the X-carriage 7, so that it is ensured on equality that the X-slide 7 has reached the correct position. Accordingly, it is proceeded with respect to the Y-carriage 5.

FIGS. 9 and 10 Finally, show an alternative embodiment of a device for detecting relative movements between the embossing unit 1 and the workpiece 34 during a stamping operation. In contrast to Fig. 4 rejects the device FIGS. 9 and 10 a z. B. attached to the side wall 3 a, mechanical button 45. This is pivotally mounted with a ball joint 46 in a connected to the side wall 3a holder 47 and supported on the workpiece surface 34a lowered embossing needle 18 by means of a rubber buffer 48 on the workpiece surface 34a. At the same time, the embossing unit 1 is supported by means of at least one support foot 49 on the workpiece surface 34a. Relative displacements of the embossing unit 1 and of the workpiece 34 in the X and / or Y direction therefore result in a pivoting of the probe 45 in the ball joint 46. This pivoting is by means of a z. B. inductively acting, the top of the probe 45 associated sensor 50 is scanned and used when exceeding the preselected tolerance range for switching off the embossing process.

The invention is not limited to the described embodiment, which could be modified in many ways. This applies in particular to the type and design of the various sensors. Instead of the distance sensor 33, which is particularly preferably an inductively or according to the eddy current principle working sensor that provides analog or digital distance signals, for example, a capacitive or optical sensor could be provided. In this case, the statement "attachment of the distance sensor 33 to the embossing needle 18" in the description and in the following claims, of course, include the case that the distance sensor 33 is not with the embossing needle 18 itself, but with a receiving this holder, z. B. the piston rod 28 ( Fig. 3 ), connected is. Furthermore, it may be expedient to dispose two or more distance sensors 33 at the circumference of the embossing needle 18. As a result, errors can be detected and compensated, which could result from the fact that the distance sensor 33 comes to rest on penetration of the embossing needle 18 in the workpiece surface 34a above a groove or groove of an already finished, previously attached character or character part. Furthermore, it is clear that the described determination of the embossing depth L3 is independent of whether the embossing of the sign 34b is effected by scribing or by plastic deformation of the workpiece surface 34a. Further, it is expedient, the distance sensor 33, since he must work without contact, with its underside at least as much above the tip 18a of the embossing needle 18 to order that the distance measurement also works when the embossing needle 18 is worn to a maximum tolerable level , The control device after Fig. 7 can z. B. be modified in that between the distance sensor 33 and the comparator 40 a dashed line indicated subtraction stage 51 is switched, in which the difference between the reference value L1 and after switching on the control device currently obtained distance L2 is formed, the actual value of the embossing depth L3 corresponds. In this case, only one desired value for the embossing depth L3 would be specified by the setpoint generator 41. In any case, the embossing depth L3 is the actual control variable, which is to be controlled constantly. It is also clear that the described monitoring of the various functions and the regulation of the embossing depth L3 are preferably carried out with the aid of microprocessor controls or the like, and thus fully automatically. Finally, it is understood that the various features may be applied in combinations other than those described and illustrated.

Claims (17)

A method of generating a character (34b) in a workpiece surface (34a) by embossing, wherein a marking pin (18) in the workpiece surface (34a) is pressed and moves parallel to this and wherein the resulting characterized embossing depth (L3) of the character (34b ) is determined using a distance sensor (33), characterized in that a stamping needle (18) attached to the embossing needle (18) and movable together with this distance sensor (33) is used, the embossing needle (18) before the embossing on the workpiece surface (34a) is placed and a resulting characterized first distance (L1) of the sensor (33) from the workpiece surface (34a) is measured, the stamping needle (18) then into the workpiece surface (34a) is pressed and thereby resultant second distance ( L2) of the sensor (33) from the workpiece surface (34a) is measured and the embossing depth (L3) from the difference (L1 - L2) of the two distances is determined. A method according to claim 1, characterized in that the embossing depth (23) during the generation of the character (34b) is controlled as a control variable to a preselected value constant. A method according to claim 2, characterized in that the embossing needle (18) is pressed by applying a pressure in the workpiece surface (34a) and the control of the embossing depth (L3) is carried out using the pressure as a manipulated variable. Method according to one of claims 1 to 3, characterized in that the embossing of the character (34b) is stopped when the embossing depth (L3) assumes a value lying outside a preselected tolerance range. Device for producing a mark (34b) in a workpiece surface (34a) by embossing, comprising an embossing needle (18) which can be placed on the workpiece surface (34a) and movable in parallel therewith, means (21, 22) for pressing in the Embossing needle (18) into the workpiece surface (34a) for the purpose of embossing and a distance sensor (33), characterized in that the distance sensor (33) attached to the embossing needle (18) and established for determining the embossing depth (L3) obtained during the embossing process is. Apparatus according to claim 5, characterized in that the distance sensor (33) immediately adjacent to the embossing needle (18) and with its underside at least as much above an outer tip (18a) of the embossing needle (18) is arranged as a desired embossing depth (L3 ) corresponds. Apparatus according to claim 5 or 6, characterized in that the embossing needle (18) in a needle head (17) which is mounted on a in two directions (X, Y) and parallel to the workpiece surface (34 a) slidable carriage (7), in a third direction (Z) is mounted back and forth. Device according to one of claims 5 to 7, characterized in that the means (21, 22) for impressing the embossing needle (18) in the workpiece surface (34a) in a third direction (Z) on the embossing needle (18) acting cylinder / - Piston arrangement included. Apparatus according to claim 8, characterized in that it comprises an adjusting device (39) for adjusting the pressure in the cylinder / piston arrangement (21, 22) such that the embossing needle (18) with a preselected embossing depth (23) in the workpiece surface (34a) penetrates. Apparatus according to claim 9, characterized in that the adjusting device (39) is part of a control device for the pressure. Apparatus according to claim 10, characterized in that as the controlled variable of the control device, the embossing depth (L3) is used, which consists of the difference of a distance (L1) of the distance sensor (33) from the workpiece surface (34a) this seated embossing needle (18) and a distance (L2) of the distance sensor (33) from the workpiece surface (34a) results in this embossed embossing needle (18). Device according to one of claims 5 to 11, characterized in that it comprises means (32, 45) for detecting relative movements between the embossing unit (1) and the workpiece (34) during a stamping operation. Apparatus according to claim 12, characterized in that the device includes an optical sensor (32). Apparatus according to claim 12, characterized in that the device includes a mechanical button (45). Device according to one of claims 5 to 14, characterized in that it contains at least two spaced apart on the circumference of the embossing needle (18) spaced sensors (33). Device according to one of claims 5 to 15, characterized in that it comprises means (42, 43, 44) for monitoring the movements taking place in the X and / or Y direction of the embossing needle (18). Device according to one of claims 5 to 16, characterized in that the one or more distance sensors (33) on a piston rod (28) are fixed, in which the embossing needle (18) is mounted easily replaceable.

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