Flat-jawed thread rolling machine and method for operating same

Abstract

The invention relates to a flat-die thread rolling machine (1) comprising a stationary first tool part (2) and a second tool part (3) that is movable in an oscillatory manner relative to the first tool part. The two tool parts (2, 3) have a profile that can be rolled into a workpiece (4) arranged between the tool parts (2, 3). The second tool part (3) is connected to a drive (5) that can cause the oscillatory movement of the second tool part (3). In order to provide such a flat-die thread rolling machine that makes it possible to provide workpieces with a profile, and in particular with a thread, in a more flexible manner, the invention provides that the drive (5) comprises a servomotor (6) that is controlled by a machine control system (7). Furthermore, the invention relates to a method for operating such a flat-die thread rolling machine.

Description

[0001] The invention relates to a flat-die thread rolling machine comprising at least one thread rolling module, which has a stationary first tool part (first rolling die) and a second tool part (second rolling die) that is movable in an oscillatory manner relative to the first tool part. The two tool parts have a profile that can be rolled into a workpiece arranged between the tool parts. The second tool part is connected to a drive that can initiate the oscillatory movement of the second tool part. Furthermore, the invention relates to a method for operating such a flat-die thread rolling machine.

[0002] A flat-die thread rolling machine of this type is known. It can be designed with a vertical tool arrangement, i.e., the movable rolling die moves horizontally or at a slight incline; horizontal tool arrangements, i.e., the movable rolling die moves horizontally, are also known. A crank drive is used to drive the movable rolling die. This drive consists of a rotating crank disc (connecting rod disc) to which one end of a connecting rod is attached; the other end of the connecting rod is connected to the movable rolling die or to a carriage that supports it. Accordingly, when the crank disc rotates, the movable rolling die moves back and forth in an oscillating manner. This creates the required relative movement between the two rolling dies.

[0003] Functional sequences are mapped in the machine via cam disks. The machines are characterized by high unit output.

[0004] The disadvantage of the previously known machine concept is that components with a large component length or complex bending geometries consisting of rods, wire sections or tube material cannot be processed or can only be processed to a very limited extent.

[0005] The invention is based on the Task The aim is to provide a flat-die thread rolling machine and a method for operating the same, with which it is possible to provide workpieces, and in particular workpiece ends, with a profile and, in particular, with a thread in a more flexible manner. In particular, the manufacturing process is to be improved.

[0006] The problem is solved by the subject matter of claim 1. This solution is characterized in that the drive comprises a servo motor that is controlled by a machine control system.

[0007] The term "workpiece" refers in particular to rod, wire, or tube sections, and more particularly to their ends. This also includes screw blanks with heads and headless pins.

[0008] The servomotor used is well known in the art. It is a special electric motor that allows the control or regulation of the angular position of the motor shaft, as well as the rotational speed and acceleration. Accordingly, the electric motor includes a sensor that enables the determination of the rotational position. The rotational position determined by the sensor is transmitted to a controller (servo controller), which regulates the motor movement according to a specified setpoint.

[0009] Accordingly, the machine control system specifies the target movement and, in particular, the target speed of the servo motor over a complete stroke cycle of the moving tool part, which is then driven as precisely as possible by the servo motor in a closed control loop.

[0010] The servo motor preferably drives directly or indirectly a spindle, in particular a threaded spindle, which engages in a nut, in particular in a threaded nut, wherein the nut is directly or indirectly connected to the second tool part.

[0011] Preferably, a gear is arranged between the servo motor and the spindle, allowing the rotary motion of the servo motor to be transmitted to the spindle. The gear is preferably a belt drive. However, it is also possible for the servo motor to act directly on the spindle and drive it. The tool arrangement, whether vertical or horizontal, as well as the direction of movement of the movable rolling die in a horizontal or vertical direction, can be flexibly applied.

[0012] A preferred embodiment of the invention provides for two thread rolling elements arranged at a predetermined distance from one another, each comprising a stationary first tool part and an oscillatingly driven second tool part, as well as a servo motor. The distance is preferably adjustable. This solution has proven particularly advantageous when it is necessary to apply a thread or a profile to two ends of a workpiece. Previously known solutions require a very stable machine design to accommodate the entire necessary tool height. The inventive proposal and use of a servo motor provides a simpler and more flexible solution for this purpose.

[0013] The proposed machine design allows for two thread rolling modules, which can be placed at a predetermined distance apart and arranged essentially in a mirror image, to provide a workpiece with two threads or profiles in a single operation without additional handling. The distance is adjustable to accommodate different raw material lengths. The respective servo motors of each thread rolling module enable axis-synchronous machining. This eliminates the need for complex mechanical coupling. However, it is also possible to operate a module in a sequential arrangement to perform several machining steps (e.g., knurling followed by the application of a thread) sequentially. This is also possible at two locations on the workpiece.The sequence and arrangement can be designed flexibly so that different and even consecutive profilings can be carried out on each side of the workpiece.

[0014] It has proven very advantageous if the loading of the machine with raw parts and the removal of the rolled or profiled parts are carried out in a special manner. Specifically, this involves defining a first side area of ​​the machine in the area of ​​a first end position of the second tool part, and a second side area of ​​the machine in the other end position of the second tool part. A first handling element for feeding a raw workpiece is arranged in the first side area, and a second handling element for removing a rolled workpiece is arranged in the second side area.

[0015] The oscillatory movement of the second tool part defines a direction of movement, wherein the first and the second handling element are preferably designed to be displaceable in said direction of movement.

[0016] The proposed machine design also allows for a very advantageous method for its operation. The proposed method generally requires the machine control system to specify a defined motion profile for the servo motor.

[0017] Specifically, this can be achieved by specifying a travel-speed profile for the servo motor, in which a constant speed is maintained over at least part of the travel of the second tool part. Preferably, a constant speed is maintained over at least 50% of the stroke of the second tool part.

[0018] Another possibility is to specify a path-speed profile for the servo motor in which the forward stroke of the second tool part is moved at a lower speed than the return stroke of the second tool part.

[0019] Preferably, the different speeds between the forward and return strokes refer to the areas of the stroke path of the second tool part in which a constant speed is maintained.

[0020] Furthermore, it can be provided that two different speed levels are operated during the forward stroke of the second tool part, with a lower speed level followed by a higher speed level.

[0021] Furthermore, an advantageous embodiment of the method provides that the machine control system provides the servo motor with a path-speed profile that is offset from a nominal profile by a specified offset in the path direction. This allows for optimal adjustment of the thread match (see below in connection with the Figures 9 and 10 ).

[0022] It is possible to use the proposed machine as a stand-alone machine and then equip it with an appropriate interface for loading raw parts and for removing rolled parts (e.g. multi-axis robots and bar loaders).

[0023] The proposed machine can also be used as a module in a production plant in which further work steps are performed on a workpiece. In this respect, reference is made to EP 4 295 968 A1, which describes several such workstations. The interfaces of the module form the workpiece feed and the removal of the finished workpiece with a thread or profile. This interface is shown below in Figure 4 discussed in more detail, where the handling devices for this (feed and discharge grippers) are described.

[0024] The proposed concept of using a servo motor enables a compact and space-saving design. The servo motor offers the advantage of being freely programmable via the machine control system, thus enabling, to a certain extent, any desired path or speed profile over a single movement cycle (forward and return stroke).

[0025] Sensors for detecting rotational positions, torques and currents can be integrated into the servo motor so that useful process and status information can be retrieved.

[0026] The drawings illustrate exemplary embodiments of the invention. They show: Fig. 1 shows a perspective view of a flat-jaw thread rolling machine, which is designed here as a single module. Fig. 2 shows a perspective view of a flat-jaw thread rolling machine, which here has two thread rolling modules that are arranged at a defined distance from one another in order to simultaneously machine a workpiece at two locations. Fig. 3 shows a schematic view of the sequence of loading a flat-jaw thread rolling machine with raw parts and the removal of machined parts according to the prior art. Fig. 4 shows a schematic view of the sequence of loading a flat-jaw thread rolling machine with raw parts and the removal of machined parts according to an embodiment of the invention. Fig. 5 shows a diagram showing the speed profile of the movable tool part over a complete travel cycle (complete forward and back stroke) according to a first embodiment of the invention.6 is a diagram showing the speed curve of the movable tool part over a complete travel cycle according to a second embodiment of the invention, Fig. 7 is a diagram showing the speed curve of the movable tool part over a complete travel cycle according to a third embodiment of the invention, Fig. 8 is a diagram showing the speed curve of the movable tool part over a complete travel cycle according to a fourth embodiment of the invention, Fig. 9 is a schematic diagram showing the shift (Δx) of the speed curve over a complete travel cycle in order to set an optimal thread match, Fig. 10 is a concrete diagram showing the shift (Δx) of the speed curve over a complete travel cycle in order to set the optimal thread match, and Fig.11 is a diagram showing the speed profile of the movable tool part over a complete travel cycle according to another embodiment of the invention to minimize slippage.

[0027] In Figure 1a flat-die thread rolling machine 1 is shown, in which a stationary first tool part 2 in the form of a rolling die and a movable second tool part 3 in the form of a rolling die are provided in a manner known per se for introducing a thread into a workpiece (not shown here). The movable tool part 3 performs an oscillating movement, i.e. over a movement cycle the tool part 3 first moves in one translational direction (forward stroke) and then back in the other translational direction (return stroke) to the starting position. Both rolling dies 2, 3 have a profiling with which a workpiece is provided which is placed between the two rolling dies 2, 3 during the forward stroke. The movable tool part 3 thus moves in the direction of movement B. Such a machine is basically known.

[0028] The special feature is that the required drive 5 for the oscillation movement of the movable rolling jaw 3 comprises a servo motor 6, which is controlled by a machine control 7 with a predetermined path or speed profile over the movement cycle (ie over a complete back and forth stroke of the movable tool part 3).

[0029] In the exemplary embodiment, the rotary movement of the servo motor 6 is transmitted via a gear 9 in the form of a belt drive to a spindle 8, which is provided with a (in Figure 1 not visible) nut, so that when the servo motor rotates, the movable tool part 3 is moved accordingly in translation.

[0030] By specifying a corresponding path or speed profile over the movement cycle by the machine control 7 to the servo motor 6, advantageous operating modes can be enabled (see below).

[0031] In Figure 2 An advantageous embodiment of the invention is shown, in which two thread rolling modules 10 and 11 are placed at a distance a from each other. The distance a can be adjusted as desired by a device not shown. The two thread rolling modules 10 and 11 correspond to those described in connection with Figure 1 were described.

[0032] In Figure 2 a workpiece 4 is shown, which is provided with a thread simultaneously at both end areas of the workpiece by the machine 1 shown.

[0033] Preferably, a loading and unloading method is used, which is described below.

[0034] For this purpose, first Figure 3Reference is made to the drawing, which outlines a previously known loading and unloading process. Six consecutive process steps 1 to 6 are shown; the subsequent process step 7, in turn, corresponds to process step 1. Accordingly, the chronological sequence of the individual substeps for loading the machine with a workpiece and removing the finished workpiece is shown here.

[0035] Viewed in the direction of movement B of the movable tool part 3, two handling elements 14 and 15 (grippers) are arranged in a side area 12 of the machine. First (see steps 1 and 2), the gripper 14 feeds a workpiece 4 into the work area between the two tool parts 2 and 3. Once the gripper 14 is retracted (see step 3), the movable tool part 3 moves (in step 4) to create the desired thread in the workpiece 4. In step 5, the gripper 15 then moves forward to grip the finished workpiece 4 and (in step 6) retract or unload it. The gripper 14 is then used again with a new workpiece.

[0036] In contrast, in Figure 4a method according to the invention is described which can generally be used without the use of a servo motor 6, but preferably with the use of the same, in order to feed and remove workpieces in a generic machine.

[0037] What is important here is that, viewed in the direction of movement B, the two side areas of the machine, namely a first side area 12 and a second side area 13, are used for handling. In each side area 12, 13, a handling element is arranged, namely a first handling element (gripper) 14 and a second handling element (gripper) 15.

[0038] In step 1, the first gripper 14 initially provides a blank of the workpiece 4 in the first side area 12. In step 2, the gripper 14 advances in the direction of movement B and places the workpiece 4 between the two tool parts 2 and 3. The gripper 14 then retracts again (step 3).

[0039] The machining process takes place according to step 4, ie the movable tool part 3 moves in the direction of movement B into the end position of the forward stroke.

[0040] Now (according to step 5), the second gripper 15 is used, which has advanced in the direction of movement B and grips the finished workpiece 4. The second gripper 15 now moves back with the finished workpiece 4, while the first gripper 14 has already prepared the next workpiece. Process step 6 therefore corresponds again to process step 1.

[0041] The proposed procedure according to Figure 4 a significant increase in the unit output of the machine can be achieved, which with the previously known solution according to Figure 3This is not possible because unloading and loading must be performed sequentially. With the proposed procedure, some work can be carried out in parallel. The proposed approach allows the workpiece to be processed in the flow and transport directions. This significantly increases the workpiece output rate.

[0042] The use of the proposed servomotors for driving the movable rolling die provides the advantageous possibility of a freely programmable movement sequence of the movable rolling die, which offers significant process-related advantages. This is illustrated in the following figures.

[0043] The drive by means of a servo motor makes it possible to freely adapt the travel profile of the rolling carriage or the moving tool part and thus the profile or thread forming process, independently of mechanical or geometric connections - as with the previously known crank drive.

[0044] While the motion of the moving tool part is largely predetermined in previously known machines with a crank drive, this is not the case with the proposed solution. Rather, customized speed-displacement profiles can be programmed. While this includes a substantially sinusoidal motion cycle, it goes beyond this. It is possible to adjust the motion curve within certain limits, with particular emphasis on keeping the forming speed constant over a significant portion of the forming process. Furthermore, it is possible to operate at a higher speed for the return stroke than for the (profile- or thread-forming) forward stroke. This leads to a further increase in unit output.

[0045] In Figure 5Such a case is shown, in which a constant speed of the movable tool part 3 is provided over significant distances (namely, approximately + / - 100 cm / s in each case) for both the forward stroke (range between 0 and 180) and the return stroke (range between 180 and 360). Thus, the profile- or thread-generating process (during the forward stroke) is advantageously carried out at a constant feed rate of the movable tool part.

[0046] In Figure 6 Essentially the same principle is illustrated, although here the return stroke is performed at approximately twice the speed of the forward stroke (forward stroke: approx. 100 cm / s; return stroke: approx. 200 cm / s). Accordingly, a significant reduction in process time can be achieved, as the return stroke can be performed in a significantly shorter time.

[0047] In Figure 7Another variant is illustrated: Here, the forward stroke essentially takes place at two different speed levels. At the beginning of the forward stroke (between approximately 10 and 45), the speed is relatively low (approximately 40 cm / s); in the subsequent section of the forward stroke (between approximately 60 and 140), the speed increases (to approximately 100 cm / s). Meanwhile, the return stroke is again performed at a largely constant speed (approximately 100 cm / s). The lower starting speed has advantages in the forming process.

[0048] Figure 8 illustrates another example in which a substantially triangular progression of the feed and retract speed is provided.

[0049] The curves shown demonstrate that the path, speed, and acceleration can be largely adjusted within certain physical limits. This allows the manufacturing process to be carried out optimally.

[0050] The forming process in the flat-die thread rolling machine is carried out on a rotating blank using two opposing dies (short / long die). To obtain an optimally formed thread or profile, the profile crests of the two rolling tools must be exactly opposite each other. The matching position is determined according to the state of the art during a run-in test, in which the blank is formed half a revolution. The result is checked to see whether the two thread traces coincide. If they do not, the thread alignment (track position) must be adjusted by moving it forward / backward until the thread crests align (thread alignment adjustment).

[0051] According to the state of the art, the rolling carriage position is changed depending on the crank angle of the crank drive. For this purpose, an eccentric insert is provided in the crank drive to accomplish the aforementioned advance or retraction of the rolling carriage and thus adjust the track position. Adjustment with the aforementioned solution can only be performed when the machine is at a standstill.

[0052] The proposed machine design with servo motor drive allows for an improved approach in this regard: The chronological sequence of the processes is implemented via software simulating a cam disk function. This allows the temporal relationship between the start time of the slide movement to be freely determined. This enables flexible adjustment of the thread alignment or track position, even during operation. Additional mechanical components (eccentrics) can thus be eliminated.

[0053] This is in principle in Figure 9 illustrated. Curve 1 initially shows the initial position before adjusting the tracking. Curve 2 is offset from curve 1 by the offset amount Δx in the abscissa direction, precisely enough so that the tracking is now correctly adjusted.

[0054] In Figure 10 This is illustrated once again for a different velocity profile over the working cycle, again with larger sections of constant velocity. Here, too, the displacement Δx is plotted.

[0055] The proposed solution also allows for the evaluation of measurement data to achieve effective process monitoring, with particular focus on the process forces generated during forming, which can be used to monitor the forming process. In particular, monitoring of the machine condition is possible.

[0056] For this purpose, the servo motor's drive data can be evaluated. The servo motor offers the ability to record and evaluate the resulting torques and thus force profiles over the traveled distance. This makes it possible to detect wear or prevent overloading. Furthermore, monitoring the forming process is possible, as the current profile progression over a work cycle (forward and return stroke) can be recorded and compared with a profile that has been assessed as being correct.

[0057] This also makes it possible to adjust the rolling carriage stroke. In order to be able to replicate the forming processes of different components with varying complexity, material quality, geometry or diameter, existing solutions require different rolling tool lengths to replicate the forming process on flat-die rolling tools. Accordingly, in existing solutions with a crank drive drive, a defined tool spread or length variation is reproduced through the mechanical design of the crank drive in a thread rolling machine. The maximum tool length that the machine can accommodate defines the necessary crank drive to enable the required overstroke for inserting, forming and ejecting. The use of shorter rolling tools is therefore limited, as a large overstroke makes it difficult to eject the parts smoothly.

[0058] In contrast, the proposed solution allows for variable stroke adjustment. If a sufficiently long roller carriage guide is available, the proposed drive concept can variably adjust the stroke required for the installed tool length. This makes the machine more versatile.

[0059] Furthermore, the movement profile can be adjusted, which is not possible with the previously known solution.

[0060] A further advantage of the proposed method is the prevention of slippage. When inserting a blank into the threading tool, the blank can occasionally "slip" due to excessive slippage, resulting in improper thread profiling. This can even lead to machine damage due to a "backslide." This problem can be specifically counteracted with the inventive design by adjusting the acceleration and thus the movement profile at defined process times.

[0061] This is in Figure 11 illustrated. It can be seen that at the beginning of the movement cycle, ie at the beginning of the forward stroke, the speed initially increases relatively slowly, before then increasing (between approximately 70 and 150) to a constant maximum value (of approximately 100 cm / s).

[0062] If excessive wear occurs in a specific area of ​​the flat-die die tool, it can be counteracted by adjusting the motion profile. This leads to longer tool life, more good parts produced on a pair of flat-die thread rolling dies, reduced production costs, and improved economic and ecological operation. Tool wear can be optimized in this way. List of reference symbols:

[0063] 1 Flat-jaw thread rolling machine 2 Stationary first tool part (rolling dies) 3 Movable second tool part (rolling dies) 4 Workpiece 5 Drive 6 Servo motor 7 Machine control 8 Spindle 9 Gear (belt drive) 10 Thread rolling module 11 Thread rolling module 12 First side area 13 Second side area 14 First handling element 15 Second handling element aDistance BDirection of movement ΔxDisplacement

Claims

1. Flat-die thread rolling machine (1), comprising at least one thread rolling module (10, 11), which has a stationary first tool part (2) and a second tool part (3) which is movable in an oscillatory manner relative to the first tool part, wherein the two tool parts (2, 3) have a profile which can be rolled into a workpiece (4) arranged between the tool parts (2, 3), wherein the second tool part (3) is connected to a drive (5) which can cause the oscillatory movement of the second tool part (3), characterized by that the drive (5) comprises a servo motor (6) which is controlled by a machine control (7).

2. Flat-jaw thread rolling machine (1) according to claim 1, characterized by thatthe servo motor (6) directly or indirectly drives a spindle (8), in particular a threaded spindle, which engages in a nut, in particular in a threaded nut, wherein the nut is directly or indirectly connected to the second tool part (3).

3. Flat-jaw thread rolling machine (1) according to claim 2, characterized by that a gear (9) is arranged between the servo motor (6) and the spindle (8), with which the rotary movement of the servo motor (6) can be transmitted to the spindle (8).

4. Flat-jaw thread rolling machine (1) according to claim 3, characterized by that the transmission (9) is a belt transmission.

5. Flat-jaw thread rolling machine (1) according to one of claims 1 to 4, characterized by thattwo of the thread rolling modules (10, 11) are arranged at a predetermined distance (a) from one another, each comprising a stationary first and an oscillatory-driven second tool part (2, 3) as well as a servo motor (6).

6. Flat-jaw thread rolling machine (1) according to claim 5, characterized by that the distance (a) is adjustable.

7. Flat-jaw thread rolling machine (1) according to one of claims 1 to 6, characterized by that in the region of a first end position of the second tool part (3) a first side region (12) of the machine is defined and in the other end position of the second tool part (3) a second side region (13) of the machine is defined, wherein in the first side region (12) a first handling element (14) for feeding a raw workpiece (4) and in the second side region (13) a second handling element (15) for removing a rolled workpiece (4) is arranged.

8. Flat-jaw thread rolling machine (1) according to claim 7, characterized by that the oscillatory movement of the second tool part (3) defines a direction of movement (B), wherein the first and the second handling element (14, 15) are designed to be displaceable in the direction of movement (B).

9. Method for operating a flat-jaw thread rolling machine (1) according to one of claims 1 to 8, characterized by that the machine control (7) specifies a defined movement profile for the servo motor (6).

10. Method according to claim 9, characterized by that the servo motor (6) is given a path-speed profile in which a constant speed is traveled over at least part of the path of the second tool part (3).

11. Method according to claim 10, characterized in that a constant speed is maintained over at least 50% of the stroke of the second tool part (3).

12. Method according to one of claims 9 to 11, characterized by that the servo motor (6) is given a path-speed profile in which a lower speed is traveled during the forward stroke of the second tool part (3) than during the return stroke of the second tool part (3).

13. Method according to one of claims 10 to 12, characterized by that the different speeds between the forward and return stroke refer to the areas of the stroke path of the second tool part (3) in which a constant speed is traveled.

14. Method according to one of claims 9 to 13, characterized by that During the forward stroke of the second tool part (3), two different speed levels are operated, with a lower speed level being followed by a higher speed level.

15. Method according to one of claims 9 to 14, characterized by thatthe machine control (7) specifies a path-speed profile to the servo motor (6) which is shifted from a nominal profile by a specified displacement (Δx) in the path direction.

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