EP3720641A1

EP3720641A1 - Method for producing a tubular frame

Info

Publication number: EP3720641A1
Application number: EP18826929.4A
Authority: EP
Inventors: Sebastian Steinbach; Torsten Scheller; Markus Remm; Torsten Reichl; Jan Langebach
Original assignee: Jenoptik Automatisierungstechnik GmbH
Current assignee: Jenoptik Automatisierungstechnik GmbH
Priority date: 2017-12-07
Filing date: 2018-12-05
Publication date: 2020-10-14
Also published as: DE102017129106B4; CN111526963A; CA3084684A1; JP7281465B2; DE102017129106A1; CN111526963B; US20210178524A1; WO2019110053A1; JP2021505398A

Abstract

The method according to the invention makes it possible to produce actual cutting contours on tubes (R) with only rough tolerances, to which contours others of the tubes (R) can be joined and welded, wherein, as a result of the actual cutting contours being modified, the rough shape tolerance of the tubes (R) does not enter the tolerance chain, or enters the latter only a little, for the tubes (R) to be fully welded to form a tubular frame. It also allows the automated reception of only pre-oriented tubes (R) by a gripping arm and the infeed thereof to a laser cutting device.

Description

Method for producing a tubular frame

Tubular frames represent a metal construction of a plurality of individual tubes which are interconnected e.g. be connected by welded joints. Tube frames are distinguished by a more favorable mass-to-strength ratio compared to solid profile frames with the same tensile strength, and are therefore particularly applicable where load-bearing structures with low weight are required.

For a desired construction, the tubes must be welded together in a predetermined relative position. This creates connections at interfaces, which are each formed by two existing on the pipes joining surfaces. As a rule, the two joining surfaces each represent a sectional contour produced therefor on one of the tubes and a fitted lateral surface of another of the tubes or a further cut contour made on another of the tubes. A cutting contour can be produced by cutting or cutting off a tube.

A disadvantage in the production of a tubular frame from partially curved tubes with a circular cross-section is the production-related large fluctuation of the bending radius for the same tubes, which causes the individual tubes have a relatively low dimensional stability of the course of their tube axes.

From the prior art, two different methods are known to trim bent tubes or tube-like components (hereinafter collectively tubes). The two methods can be automated with a laser as a cutting tool.

In a first method known from practice, prior to the method step of cutting, reference holes are introduced into the tube, via which the tube is received in a workpiece holder for positioning the tube to the cutting tool. Thus, the tube is held with a predetermined relative position of the reference holes to the workpiece holder. At a automated cutting, the cutting contours along which the pipe is cut, determined in their spatial position relative to the position of the reference holes, regardless of a possible tolerance deviation of the pipe bend of the pipe to a target value. The position of the reference holes is selected so that a tube which can be plugged into the receptacle is also within a predetermined tolerance range for the tube bend. This also determines whether the pipe is in or out of tolerance via the slip-on criterion. Due to the geometrical tolerances of the tubes a defined automated recording by a gripper and a plugging over the reference holes in the workpiece holder is not possible.

In a second known from practice, the tube is inserted into a workpiece holder, in which the tube comes into contact within a contact area. Again, the pipes must be manually inserted due to their geometric tolerances. Tubes that can not be inserted to a predetermined extent, deviate with their bending radius so far from a target value that the pipe bend is no longer within a predetermined bending tolerance. The disadvantage here, on the one hand, that due to the rigid position of the tube in the workpiece holder, the tube is limited to a cutting tool, such as a laser beam, accessible. From the workpiece holder on the pipe covered areas are accessible only by a folding of the tube in another workpiece holder for processing. This leads to an increased time and device overhead. On the other hand, out of tolerance form deviations of the tube outside the contact area of the recording are not detected, which is why optionally cut a cut contour out of tolerance on a pipe and the defective pipe is fed unnoticed further processing.

In particular, in the production of complex welding groups, such. As tube frame, it is particularly disadvantageous if it is found only at the later process step of welding the tubes that the tubes can not be connected to each other at all interfaces, because the cut contours of individual of the tubes deviate too far from a predetermined desired position and the thus resulting deviations of the spatial position of the tubes to each other in a tolerance chain summing. It is the object of the invention to provide a method for producing a tubular frame, which is comparatively more automated and advantageously shortens the tolerance chain to be considered for the production.

This object is fulfilled for a method for producing a tubular frame consisting of a multiplicity of tubes, which are welded to one another at a plurality of actual interfaces in each case via two joining surfaces. At least one of the two joining surfaces represents an actual sectional contour, along which one of the two pipes to be welded in each case has been cut or cut off prior to welding with a laser beam. In each case, a tolerance envelope is calculated for the individual tubes and stored with reference to a coordinate system related to a delivery device. For the tubular frame, a nominal sectional contour pattern with nominal sectional contours, which are each assigned to one of the actual sectional contours, is defined and the nominal sectional contours are stored relative to the tolerance envelopes of the individual tubes.

In each case one of the tubes is received by the feed device with a gripping arm and transported relative to an optical measuring device, which occupies a known spatial position in the coordinate system, where the tube is optically detected and measured. The gripper arm moves the tube in space until the tube is within the tolerance envelope calculated for that tube. At the same time or after, the feed device adjusts the tube of a laser cutting device so that the tolerance envelope calculated for the tube assumes a predetermined relative position to the laser cutting device, with which the tube has assumed a spatial position defined by a spatial position of the tolerance envelope relative to the laser cutting device.

The laser beam of the laser cutting device describes the desired cutting contour, which is related to the tolerance sheath, wherein the actual cutting contour is cut on the pipe. The actual sectional contour corresponds to a projection of the desired sectional contour onto the tube.

The actual sectional contour has either the shape of a cutout surface or an end face. The actual sectional contour in the form of a cutout surface in a jacket of one of the tubes corresponds to the tubes inserted into the same tolerance envelope with different tolerance deviations of a differently modified mapping of the nominal sectional contour, so that the other of the tubes welded to this actual sectional contour, irrespective of the position the inserted tube in the tolerance shell occupies a same relative position to the tolerance shell of the inserted tube.

The actual sectional contour in the form of an end face of one of the tubes assumes a different angle with a tube axis of the tube for the tubes inserted with different tolerance deviations in the same tolerance envelope, so that the other of the tubes welded to this actual sectional contour, regardless of the position of the inserted Pipe in the tolerance shell occupies a same relative position to the tolerance shell of the inserted tube.

Advantageously, the tube of the laser cutting device is not delivered when the tube is not available in the tolerance sheath, which is a criterion that the tube is out of tolerance.

In order to connect the pipes as intended to a pipe frame, they are welded together at interfaces (hereinafter actual interfaces). Each actual interface is defined by the position of a real sectional contour (hereinafter actual sectional contour), which results from cutting or cutting one of the tubes. The resulting actual sectional contour, in the form of a cutout surface on the jacket of the tube or an end face at the end of the tube, is in each case joined to the lateral surface or a cut end face of another of the tubes and welded.

It is essential to the invention that for cutting the actual cutting contour the laser beam is not guided relative to the respective real pipe, but the laser beam is guided along the desired cutting contour, which is related to the tolerance envelope calculated for the relevant pipe. The desired cutting contour is preferably within the tolerance envelope, preferably centrally between the positions of two maximum deviating actual Cut contours on the inserted into the tolerance sheath pipes. The actual cutting contour is produced as a projection of the desired cutting contour onto the real pipe. Depending on the angular position of the laser beam in each case to the solder in the impact points along the desired cutting contour, the target sectional contour is reduced, enlarged or otherwise modified projected onto the jacket of the tube. Ideally, the projection takes place in such a way that the other tube applied to the resulting actual cut contour with its lateral surface always has the same relative position to the tolerance casing of the cut tube relative to the tolerance casing, completely independent of how the cut tube lies in the tolerance casing. Thus, the positional tolerance of lying in the tolerance sheath pipes is not in a tolerance chain.

For each tube, the individual tolerance envelope is calculated, which determines the shape tolerance of the respective tube and is stored together with the respective nominal tolerances assigned to the tolerance interface, a desired interface pattern, based on a spatially fixed coordinate system. The tube then taken for processing is delivered to a 3-D camera. The tube is measured three-dimensionally and by moving the gripper arm holding the tube, the tube is inserted into the calculated tolerance sheath. If insertion is not possible, the pipe is out of tolerance. The tolerance envelope may also encase only one or more individual sections of the tube. The tube has a knowledge of the location of the tolerance envelope in space a known spatial position and is relatively delivered with this accuracy of the laser cutting device. This means that the real pipes do not take up a reproducible spatial position relative to the laser cutting device and thus to the laser beam guided through the cutting nozzle. However, a reproducible spatial position is taken up by the tolerance envelope.

The invention will be explained in more detail with reference to an embodiment and drawings.

Show:

1 a a tube frame with four tubes in exploded view, 1 b a representation of the assembled tube frame according to FIG. 1 a,

1 c shows a desired interface pattern for the tubular frame according to FIGS. 1 a and 1 b relative to a coordinate system,

2 shows the tube frame according to FIG. 1 in an exploded view with tolerance sleeves for the tubes, FIG.

Fig. 3a an ideal tube ideally lying in the tolerance envelope,

3b a faulty tube lying in the tolerance envelope,

3c shows another faulty tube lying in the tolerance envelope,

Fig. 4a shows the relative position of a tube, which with its lateral surface on the

Cutting contour of another tube is applied,

4b shows an ideal tube, ideally lying in the tolerance envelope,

4c shows a tube, tilted in the tolerance envelope,

Fig. 4d another tube, tilted lying in the tolerance shell and

Fig. 5 is a schematic diagram of a device suitable for the implementation of

Process.

FIG. 1 a shows a tube frame in an exploded view by way of example, which consists of tubes R, here four tubes Ri-R ₄ , which are welded together at actual interfaces SIST, here specifically five actual interfaces SISTI-SISTS. The actual interfaces SIST _I - SIST _S are formed in each case by welding-compatible joining surfaces V at the two respective tubes R forming a welding partner. In Fig. 1 b, these four pipes Ri - R ₄ are shown welded together as intended. In Fig. 1c A target interface pattern with nominal interfaces SSOLL for the tubular frame is shown. Each of the target interfaces SSOLL is assigned to one of the actual interfaces SIST.

There are basically three different interface types:

The first interface type results in a pairing of two tubes R over two end faces. An example of this is shown in FIG. 1a-1b on the basis of the actual interface SISTI, in which an end face of the tube R3, as the joining face VR ₃ -I, is welded to an end face of the tube Ri, as the joining face V _R11 .

The second interface type results in a pairing of two tubes R over a cut-out surface and a lateral surface. An example of this is shown in FIGS. 1a-1b on the basis of the actual interface SIST ₂ , in which a cut-out surface of the tube Ri, as the joining surface V _R12 , is welded to the lateral surface of the tube R ₂ , as the joining surface V _R22 ,

The third interface type results in a pairing of two tubes R over an end face and a lateral surface. An example of this is shown in FIG. 1 on the basis of the actual interface SIST ₃ , in which an end face of the tube R ₄ , as the joining surface V _R42 , is to be welded to the lateral surface of the tube R ₃ , as the joining surface V _R33 .

Each of the interface types has the at least one joining surface V, which represents a nominal sectional contour "SOLL. According to the invention, its desired position is determined based neither on the ideal tube R nor on the real tube R, but on a calculated tolerance envelope H. This tolerance envelope H encloses the ideal tube R. Likewise, it surrounds the real tube R whose outside dimensions are in tolerance. The tolerance envelope H can also be defined only for individual sections of individual tubes R.

In advance of cutting the tubes R for the tubular frame, tolerance ranges for dimensional accuracy of the shape of the tubes R in question are calculated as the so-called tolerance envelopes H, at least for the tubes R to be cut, on the basis of FIG Pipes R in their pipe cross-section and the Tube lengths are made with sufficient accuracy, the possible shape deviation essentially relates to the deviation of the course of the actual tube axis of a target tube axis due to the deviation of actual bending radii of target bending radii on the tube R and a possible twisting of the actual tube axis in the bending areas.

Each actual interface SIST is assigned to the tolerance envelope H reference interface SSOLL, see Fig. 1 b in combination with Fig. 1c assigned. The desired interfaces SSOLL are stored in a fixed position relative to one another in a desired interface pattern. This means that the relative spatial position of the desired sectional contours K _S OLL are stored relative to each other for the joining surfaces V to be produced by cuts.

The tolerance sheaths Fl are each calculated so that the actual sectional contours K _{! S} T SO can be cut on each tube R which fits into the tolerance sheath F, so that the suitable joining surface V for the welding results. In Fig. 3a, the ideal pipe R is ideally shown lying in the tolerance envelope Fl. The tube axes of the ideal tube R and the tolerance envelope Fl coincide. Advantageously, the desired cutting contours KSOLL are calculated so that they coincide in this case with the actual cutting contours KIST. This would no longer be the case if the ideal tube R were tilted in the tolerance envelope Fl.

In FIGS. 3b and 3c, two tubes Ri are shown, which each fit into the tolerance envelope FI ₁ and deviate differently from the shape of an ideal tube Ri. The nominal sectional contours K -i SOLL, KRI2SOLL, KRI3SOLL have, relative to the tolerance envelope Fl-i _, an equal relative position relative to each other, however, the actual cutting contours K _{R11 | S} T, KREIST, K _R13 IST have the same as the real Ri pipes, here exaggerated drawn, cut, a slightly different spatial position and also a different shape and / or size. A cut-out surface as the joining surface V _Ri2 for the actual interface S ₂ IST extends more or less deeply into the tube R ₁ . An end surface as the joining surface V _R11 for the actual interface SUST is cut at different points along the tube axis of the tube R and at a different angle to it. The tube R _3, in which a face and a cut surface are the same as the tube R _{1, are to be finished} as joining surfaces V _R31 and V _R2i for the actual interfaces S-HST and S ₅ IST, respectively, and are processed analogously to the tube Ri.

On the tube R ₄ , only one end face is cut as the joining face V _R42 for the actual interface S ₃ IST. The tolerance to the second actual interface S ₄ IST is compensated, in which the tube R _{4 is} welded to a mitwandernden area of its lateral surface on a joining surface V _Ri3 , which is a cut surface.

The pipe R ₂ has no actual cutting contours K _{! S} T. His joining surfaces V _R21 , V _R22 are areas on lateral surfaces whose relative position to each other in the Fierstellung of the tube R is formed. This means, in contrast to the joining surfaces V, which arise differently due to the different position of the tube R in the tolerance sleeve F1 due to the cutting of actual sectional contours K _{! S} T on the tubes R, whereby the tolerances can be compensated Tolerance deviation be accepted. Accordingly, either the tolerance envelope F1 must be kept sufficiently narrow at least in the region of the connection points V _R21 and V _R22 , or the tube R is designed so that it is delivered to the joining surfaces V of the other tubes R by a positional adaptation. Specifically, here the u-shaped tube R should be designed so that its two legs do not run parallel to each other, but enclose a small angle with each other, so that a positional adjustment on the displacement in the direction of the legs is possible. After the tubes Ri and R ₂ have been welded together at the actual interface SUST and the tube R _{4 has been} welded on, the tube R is joined from above between the tubes Ri and R ₃ and more or less protruding upwards at the actual interfaces S ₂ IST and S ₅ IS welded.

At Fland of Fig. 4b to 4d is shown once more simplified on a straight pipe R, as a target - sectional contour K _S OLL relative to a tolerance envelope Fl is projected onto each lying in the tolerance envelope Fl pipes R. Actual sectional contours KIST projected onto the jacket of the respective tube R are modified relative to the desired sectional contour KSOLL by a layer, size and / or Change in shape, depending on the spatial position in which the jacket of the respective pipe R is located relative to the desired sectional contour K _S OLL. The other of the tubes R, which in each case is welded to the at least one actual sectional contours K _{| ST} , has in each case the same spatial position as in FIG. 4 a at the edge of three tubes R which lie differently in the tolerance envelope Fl, as shown in FIGS. 4b - 4d is shown.

FIG. 5 shows a schematic diagram of a device suitable for carrying out the method. The device comprises a feed surface 1, a feed device 2 with a gripping arm 2.1, an optical measuring device 3, e.g. a 3-D camera, a laser cutting device 4, with a cutting nozzle 4.1, a storage and control unit 6 and advantageously a further optical measuring device 5. With her is checked whether a pipe or more tubes R and how they are two-dimensionally aligned on the feed surface 1 lie. With this knowledge, the gripping arm 2.1 can be tracked in case of position deviations from a desired position, which may also be due to a shape deviation of the tube R, to optimally grip the tube R.

For processing the tubes R, that is to say for setting the desired cut contours KSOLL, the tubes R are respectively received by the feed arm 2 of the feed device 2 by a feed surface 1. Ideally, the tubes R are pre-sorted, prepositioned and preoriented on the feed surface 1, so that the gripping arm 2.1 when starting a predetermined gripping position in each case the tube R, to the gripping arm 2.1 pre-aligned, picks up. There is no need to position the tubes R so precisely on the feed surface 1 that they are picked up when picking up in a reproducible spatial position to the coordinate system of the feed device 2, which also accommodates the comparatively large tolerance of the shape of the individual tubes R.

The gripper arm 2.1 is preferably a multi-axis gripper arm 2.1, which can freely move a gripped workpiece, in this case the tube R, within a limited operating range. Within the working area is the feed surface 1, the optical measuring device 3 and the laser cutting device 4, each having a known spatial position within the coordinate system. By means of the gripping arm 2.1, the tube R is transported to the optical measuring device 3, where the tube R is optically detected and measured. Subsequently, the tube R is inserted by the gripper arm 2.1 in a tolerance envelope H, which is confirmed that the tube R is in tolerance. The spatial position of the tube R within a coordinate system defined by the feed device 2 is thus determined by the spatial position of the tolerance envelope H in the coordinate system.

Thereafter, or at the same time, the gripping arm 2.1 adjusts the tube R of the laser cutting device 4 in such a way that the tolerance envelope H is in a predetermined relative position to the laser cutting device 4. The laser cutting device 4 then cuts the actual sectional contours K _{! S} T on the tube R, wherein the laser beam is guided through the cutting nozzle 4.1 along a desired cutting profile K _S OLL related to the tolerance envelope H. The method is possible with a laser beam, because the execution of the cut does not require the mechanical contact between a cutting tool and a workpiece and thus a defined position of the working surface, as in the case of a mechanical machining. When laser cutting, the processing surface can occupy a different spatial position at least within the focus area.

The method according to the invention makes it possible to produce the actual sectional contours K _{! S} T on the only roughly tolerated tubes R, to which other tubes R can be added and welded, wherein the coarse tolerance of the tubes R is achieved by modifying the actual sectional contours KIST not or only slightly into the tolerance chain for complete welding of the tubes R flow into a tube frame. It also allows the automated recording of only pre-oriented tubes R by the gripper arm 2.1 and their delivery to the laser cutting device. 4

LIST OF REFERENCE NUMBERS

R tube

S interface

SIST is the interface

SSOLL target interface

K _{| S} T Actual sectional contour

KSOLL nominal cutting contour

V joint surface

H tolerance sleeve

1 delivery area

2 delivery device

2.1 gripping arm

3 optical measuring device

4 laser cutting device

4.1 cutting nozzle

5 additional optical measuring device

6 control and storage unit

Claims

claims

1. A method for producing a tubular frame, consisting of a plurality of tubes (R) which are welded together at a plurality of actual interfaces (SIST) in each case via two joining surfaces (V), wherein at least one of the two joining surfaces (V) one Is - sectional contour (K | _S T) represents along which one of the two respective pipes to be welded (R) was cut or cut before welding with a laser beam, characterized

in that in each case a tolerance envelope (H) is calculated for the individual tubes (R) and stored with reference to a coordinate system related to a delivery device (2),

in that a nominal sectional contour pattern with nominal sectional contours (KSOLL), which are assigned to one of the actual sectional contours (KIST), is defined for the tubular frame, and the nominal sectional contours (K _S OLL) are related to the tolerance enclosures (H) of the individual tubes (R) are stored,

that the feed device (2) with a gripping arm (2.1) receives in each case one of the tubes (R) and transports it relative to an optical measuring device (3) with a known spatial position in the coordinate system where the tube (R) is optically detected and measured,

that the gripper arm (2.1) spatially moves the tube (R) until the tube (R) is within the tolerance envelope (H) calculated for that tube (R),

in that the feed device (2) relatively delivers the tube (R) to a laser cutting device (4) in such a way that the tolerance envelope (H) calculated for the tube (R) assumes a predetermined relative position relative to the laser cutting device (4), whereby the tube (R) engages by a spatial position of the tolerance envelope (H) defined spatial position based on the laser cutting device (4) has taken, and

the laser beam of the laser cutting device (4) describes the nominal cutting contour (KSOLL) related to the tolerance envelope (H) and the actual cutting contour (KIST) is cut on the tube (R), the actual cutting contour (KIST) of a projection the desired cutting contour (K _S OLL) corresponds to the pipe (R).

2. Method for producing a tubular frame according to claim 1, characterized in that in that the actual sectional contour (KIST) has the form of a cutout surface in a jacket of one of the tubes (R) which, for the tubes (R) inserted into the same tolerance envelope (H), has different tolerance deviations of a differently modified illustration of the desired sectional contour (FIG. SOLL), so that another of the tubes (R) welded to this actual sectional contour (KIST), irrespective of the position of the inserted tube (R) in the tolerance sheath (H), has the same relative position to the tolerance sheath (H) of the inserted one Pipe (R) occupies.

3. A method for producing a tubular frame according to claim 1, characterized in that

the actual sectional contour (K _{| ST} ) has the shape of an end face of one of the tubes (R) which, for the tubes (R) inserted into the same tolerance envelope (H) with different tolerance deviations, has a different angle with a tube axis of the tube (R ), so that a welded to this actual - sectional contour (K _{| ST} ) different from the tubes (R), regardless of the position of the inserted tube (R) in the tolerance envelope (H) an identical relative position to the tolerance envelope (H) of the inserted Pipe (R) occupies.

4. A method for producing a tubular frame according to claim 1, characterized in that

that the tube (R) of the laser cutting device (4) is not delivered when the tube (R) is not in the tolerance sheath (H) is available, which is a criterion that the tube (R) is out of tolerance.