Cold Forming Machine

This application claims priority under 35 U.S.C. § 119 to the following German Patent Application No. 10 2024 111 210.7, filed on Apr. 22, 2024, the entire contents of which are incorporated herein by reference thereto.

The present disclosure refers to a cold forming machine for cold forming of a workpiece, particularly a cylindrical or hollow cylindrical section of a workpiece. During the deformation a profile is produced on the circumference of the workpiece by means of cold forming, for example a spur toothing parallel to an axis of the workpiece or a helical toothing obliquely to the axis of the workpiece or a thread.

Cold forming machines and methods for producing such a profile are known, for example from EP 1 286 794 B1 or EP 3 807 023 B1.

Starting from the known cold forming machines, it is the object of the present disclosure to increase the productivity and to thereby guarantee a high quality and low waste parts of deformed workpieces.

This object is solved by means of a cold forming machine for cold forming of a workpiece in order to create a profile on a workpiece outer surface including: two tool pairs each having one first cold forming rack extending in a longitudinal direction and one second cold forming rack extending in the longitudinal direction arranged with distance to the one first cold forming rack in a transverse direction, at least three tool slides that can be moved independently from one another, wherein the one first cold forming rack and the one second cold forming rack of a common tool pair of the two tool pairs are arranged on different tool slides of the at least three tool slides, a controllable drive unit for each tool slide of the at least three tool slides that is configured to move an assigned tool slide of the at least three tool slides in the longitudinal direction, a control unit that is configured to control the controllable drive unit of at least two of the at least three tool slides in a manner so that the one first cold forming rack and the one second cold forming rack of each of the two tool pairs take an individually adjustable reference position relative to one another in the longitudinal direction, wherein the control unit is also configured to move the at least three tool slides by the controllable drive unit of each tool slide of the at least three tool slides in the longitudinal direction after adjustment of the individually adjustable reference position, so that the one first cold forming rack moves opposite to the one second cold forming rack in the longitudinal direction in order to thereby deform the workpiece between the one first cold forming rack and the one second cold forming rack.

The cold forming machine according to the present disclosure is configured to produce a profile on one workpiece outer surface respectively by means of cold forming of at least a cylindrical or hollow cylindrical section of a workpiece or also on different workpieces. The toothing can extend parallel to the workpiece axis or obliquely inclined in circumferential direction around the workpiece axis and thus can form a spur toothing or helical toothing. The workpiece outer surface or the profile created thereon is coaxially arranged relative to the workpiece axis.

For cold forming the cold forming machine comprises two or also more than two tool pairs. For a distinction the tool pairs can be denoted as first tool pair and as second tool pair and, if applicable, additional tool pairs can be numbered consecutively respectively. Each of the tool pairs has two cold forming racks extending in a longitudinal direction. The cold forming racks can be denoted as first cold forming rack and second cold forming rack for distinction purposes. The first cold forming rack and the second cold forming rack of a common tool pair are arranged with distance to one another in a transverse direction.

Here, it has to be noted that the numerals in direct combination with a feature (for example “first”, “second”, . . . ) serve only for distinction of the features and do not pose a restriction in relation to the sequence or the number of present features.

Each cold forming rack has a cold forming profile, wherein the cold forming profiles of the cold forming racks of a common tool pair face one another in transverse direction. In transverse direction the workpiece can be arranged between the cold forming racks of a common tool pair and can thereby be arranged rotatably around the workpiece axis. For deformation, the cold forming racks of a common tool pair are pressed in transverse direction from opposite sides with their cold forming profiles against the workpiece outer surface and are moved in longitudinal direction opposite to one another, whereby the workpiece outer surface of the workpiece rolls between the cold forming profiles and is thereby deformed for creation of the profile.

The cold forming machine according to the present disclosure can concurrently deform two or more than two workpieces using the two tool pairs. For this purpose, it comprises at least three and preferably four independently movable tool slides for the movement of the cold forming racks in longitudinal direction for the two tool pairs. To any additional tool pair, also one or two individually movable tool slides can be assigned. Thus, to each tool pair, one or two of the individually movable tool slides can be assigned. The tool slides are particularly not mechanically movably coupled and can be moved individually in longitudinal direction by means of an assigned controllable drive unit. The controllable drive units for the tool slides are controlled by means of a common control unit and can thus be moved in coordinate manner relative to one another. Exactly one controllable drive unit is assigned to each tool slide so that the cold forming machine, in case of two tool pairs, comprises at least three and preferably four drive units. Each drive unit can have a controllable electric motor, for example.

The control unit can be any electrical and/or electronic unit that is configured for carrying out a control program. For this purpose, the control unit can comprise a microcontroller and/or a random access memory and/or a non-volatile memory, for example.

The control unit of the cold forming machine is configured to adjust the cold forming racks of the tool pairs so that the two cold forming racks of each tool pair take an individually adjustable reference position relative to one another in longitudinal direction. The reference position thus describes the relative position of the cold forming racks of a common tool pair with view in longitudinal direction. For this purpose, the control unit uses the individually movable tool slides and the controllable drive unit assigned to each tool slide. By means of the individually movable tool slides, the reference positions as well as any additional position of the two tool pairs can be individually adjusted independent from one another.

Referencing or adjustment guarantees that the geometry or form of the profile with view in circumferential direction of the workpiece axis corresponds to the requirements. Particularly, due to the adjustment or referencing, pitch errors of the produced profile can be reduced or eliminated so that the profile corresponds to the desired values for the pitch or the defined tolerance range for the pitch. The pitch defines the distance of two adjacent flanks of the profile along the respective pitch circle around the workpiece axis (for example in case of a spur toothing) or in direction parallel to the workpiece axis (for example, thread) or orthogonal to the extension direction of the profile teeth (for example helical toothing).

After the adjustment or referencing, the workpieces can be deformed and thereby the profiles can be produced on the workpiece outer surfaces. For this purpose, the tool slides are moved in coordinate manner in longitudinal direction so that the first cold forming racks of the tool pairs move opposite to the second cold forming racks of the tool pairs and the workpieces respectively roll between one first cold forming rack and one second cold forming rack of each tool pair, as already explained above.

Due to the concurrent deformation of two workpieces, a high productivity is achieved. The deformed workpieces can be identical or can be different from one another. Compared to two cold forming machines having only one tool pair, the footprint of the cold forming machine according to the present disclosure is smaller. The pitch of the profile to be produced on the two workpieces can be individually optimally adjusted for each tool pair in order to comply with the set point requirements. Corrections can be controlled by means of the control unit if a reference position or both reference positions shall be modified. A mechanical release and re-establishment of a connection between a cold forming rack and a tool slide is thereby not necessary. The required setup times in such an adjustment or referencing are thus short.

The adjustment or referencing can be carried out automatically based on at least one parameter, which is automatically determined or preset by an operating person, such as at least one pitch parameter characterizing a set point value of the pitch and/or an actual value of the pitch of a profile.

Due to the arrangement of the cold forming racks on three or preferably four (or also more than four) tool slides, in addition, the vibration transmission between the individual cold forming racks can be reduced so that the vibrations or oscillations occurring during the deformation of one workpiece by means of one tool pair only have less influence on the deformation of the workpiece by means of the respective at least one additional tool pair, whereby vibration-induced drawbacks can be reduced. Also, an influence due to thermal length changes can be reduced and can be compensated more simply due to the individual referencing or adjustment of the tool pairs.

In an embodiment the first cold forming racks of the two tool pairs or, alternatively, the second cold forming racks of the two tool pairs can be arranged on a common tool slide. The respective other cold forming racks are then arranged on an individual tool slide respectively. In doing so, the cold forming racks of each tool pair can be adjusted or referenced in longitudinal direction in order to adjust the respective reference positions.

In a further embodiment each cold forming rack is arranged on a separate individual tool slide. Therefore, an additional degree of freedom for the control of the movement of the tool slide is available. Another advantage of this arrangement is that mutual influences of the tool pairs (for example, due to vibrations, thermal length changes, etc.) are not transmitted along a common tool slide, and thus, a further improvement of the decoupling is achieved.

It is preferred that the control unit is configured to move the tool slides in longitudinal direction during the deformation of the workpieces, so that the first cold forming racks are temporally synchronously moved relative to one another and that the two second cold forming racks are temporally synchronously moved relative to one another. A temporally synchronous movement means that the movement of each tool slide starts concurrently and ends concurrently and as an option that the tool slides have the same movement speed at each point in time.

The cold forming racks of each tool pair can also be moved multiple times in longitudinal direction opposite to one another for deforming the workpieces (multiple strokes) and can thereby change the movement direction between two strokes.

It is advantageous if the control unit is configured to move the tool slides during deformation of the workpieces in longitudinal direction in a manner that all cold forming racks are moved about the same path lengths respectively.

Preferably, the tool slides are moved during the deformation so that the first cold forming racks are temporally synchronously commonly moved without changing their relative position in longitudinal direction and also the second cold forming racks are temporally synchronously moved relative to one another without changing their relative position in longitudinal direction. In other words, during the deformation no relative movement in longitudinal direction of the first cold forming racks relative to one another and no relative movement in longitudinal direction of the second cold forming racks relative to one another occurs.

If multiple tool slides are provided for the first cold forming racks or if multiple tool slides are provided for the second cold forming racks, the tool slides for the respective first cold forming racks or the tool slides for the respective second cold forming racks have a longitudinal distance to one another in longitudinal direction. This longitudinal distance is thus provided between two respective tool slides that are arranged on the same level with view in transverse direction. Due to this longitudinal distance, the tool slides are decoupled from one another and particularly not mechanically drivingly coupled.

The longitudinal distance between two adjacent tool slides can be less than the path length travelled during the deformation in an embodiment. The path length is the distance in longitudinal direction between an initial position of a cold forming rack prior to deformation and an end position of the cold forming rack after deformation.

In an advantageous embodiment the cold forming machine comprises a position sensor arrangement. The position-sensor arrangement has multiple position sensors that are configured to determine the position of each tool slide in longitudinal direction relative to a machine basis of the cold forming machine in direct or indirect manner and to transmit respective position sensor values to the control unit. The position sensors can be absolute measurement sensors or relative measurement sensors. A position sensor value can indicate the position of a tool slide relative to the machine basis directly or indirectly.

As an option, the position sensor arrangement can also be configured to detect the position of one or more tool slides in another spatial direction than the longitudinal direction, for example in transverse direction if the tool slide can be moved or positioned in another spatial direction.

It is additionally advantageous if the control unit is configured to determine the individual reference position for the assigned tool pair based on at least one pitch parameter of the profile to be produced or the produced profile on a workpiece and to set the individual reference position by means of a respective control of at least one drive unit in the context of the adjustment or referencing. The pitch parameter can thereby describe a set point value and/or an actual value and/or a deviation between the set point value and the actual value.

Indifferent embodiments of a cold forming machineare illustrated in the type of a block diagram. The cold forming machineis configured to produce a profileon a workpiece, particularly a workpiece outer surfaceof the workpieceby means of cold forming (). The workpiece outer surfaceis present on a cylindrical or hollow cylindrical section of the workpiece. Prior to deformation, the workpiece outer surfaceextends coaxially to a workpiece axis W.

The produced profilecan be a toothingor alternatively a thread. Ina spur toothing is illustrated by way of example as an embodiment of toothing. The teeth of this toothing extend parallel to the workpiece axis W. Alternatively, the toothingcan also be a helical toothing, wherein the teeth then extend obliquely relative to the workpiece axis W with view in circumferential direction around the workpiece axis W.

By means of the cold forming machine, concurrently multiple workpieces, for example two workpieces, can be deformed. For this purpose, the cold forming machinecomprises multiple tool pairs, according to the example a first tool pairand a second tool pair. Each tool pair,has respectively one first cold forming rackand one second cold forming rack, wherein the cold forming racks,extend in a longitudinal direction L. Orthogonal to the longitudinal direction L, in a transverse direction Q, the first cold forming rackand the second cold forming rackof a common tool pair,are arranged with distance to one another.

Inan embodiment of a cold forming rack is schematically illustrated that can be used as first cold forming rackand a second cold forming rack. The cold forming rack,has a cold forming rack profilehaving a multiplicity of cold forming profile teetharranged with distance to one another in longitudinal direction L. Two directly adjacent cold forming teethare separated from one another by a cold forming tooth gap. In, by way of example, only two of the cold forming profile teethare illustrated schematically. The cold forming rack profileextends in longitudinal direction L along the entire cold forming rack,as schematically illustrated by way of the dashed line and the dash-dotted line.

In the embodiment illustrated inthe cold forming rack profilecomprises a run-in section, a central sectionadjoining the run-in sectionand a run-out sectionadjoining the central section. The run-in sectionis optional and can also be omitted and replaced by a respectively longer central section.

In the run-in sectionthe tooth height of the cold forming profile teethincreases with view in transverse direction Q toward the central section. In the central sectionthe tooth height of the cold forming profile teethis constant. In the run-out section, the tooth height of the cold forming profile teethis constant and preferably as high as in the central section. While the tooth heads of the profile teethin the central sectionare arranged along a common plane E extending in longitudinal direction L, the profile tooth heads of the profile teethare arranged with distance to this plane in the run-out section, whereby the distance from this plane E increases in the run-out section, the farther the cold forming profile toothis distanced from the central sectionin longitudinal direction L.

In the embodiment the cold forming profile teethextend orthogonal to the longitudinal direction L in order to create the spur toothing illustrated by way of example in. Alternatively, the cold forming profile teethcan also extend obliquely relative to the longitudinal direction L, for example if helical toothing shall be produced.

As additionally illustrated in, each cold forming rack,can be attached to an assigned tool slideby means of a tool carrier, for example by means of a screw connection or another releasable connection. The cold forming racks,are (according to the example indirectly or alternatively directly) releasably arranged on an assigned tool slideand are arranged immovably relative to the respective tool slide.

The cold forming machinehas multiple tool slides. In the embodiment illustrated inthe cold forming machinehas three tool slidesand in the embodiment according to, four tool slides. Each tool pair,, two separate tool slidesfor the first cold forming rackand the second cold forming rackare assigned.

The tool slidesare individually movable in longitudinal direction. A rigid mechanical coupling between the present tool slidesdoes not exist. The movement control of the tool slidescan be individually set for each tool slide.

A separate individually controllable drive unitis assigned to each tool slide. Each drive unitcan comprise a controllable electric motor, for example. The control of the drive unitsfor movement of the respectively assigned tool slidein longitudinal direction L is carried out by means of a control unitof the cold forming machine. For example, control unitcan be any electrical and/or electronic device configured for carrying out a control program and can, for example, comprise a micro-controller, a random access memory and a non-volatile data memory.

The control unitcreates a control signal Ai for each present drive unit. In the embodiment illustrated in, three drive unitsare present, so that three individual control signals A, A, Aare created. The embodiments of the cold forming machineaccording tohave four drive units, so that four individual control signals A, A, A, Afor each present drive unitare created respectively. In doing so, it is possible to move each tool slidein longitudinal direction L relative to a machine basisby using control unitand drive units.

The machine basisis only schematically illustrated inby means of a dashed line. For example, the tool slidescan be arranged movably in longitudinal direction L on the machine basisby means of a suitable rail guide or another suitable guide device.

In the embodiments illustrated here, cold forming machinecomprises a position sensor arrangement. The position sensor arrangementis configured to detect the position of each present tool slidein longitudinal direction L relative to a common reference system, for example the machine basis. In doing so, the absolute position of each tool slide can be determined.

The position sensor arrangementcan comprise multiple position sensorsthat create one position sensor value Pi (i=1, 2, 3, 4) respectively. One separate position sensorcan be assigned to each individually movable tool slide. The position sensorcan be configured as absolute measurement position sensor or as relative measurement position sensor. The position sensorscan be arranged on an assigned tool slideor on the machine basisor can be part of the drive unit. For example, by means of an encoder of the electric motor of the drive unit, a movement and/or position determination of the assigned tool slidecan be realized.

The arrangement of the position sensorsof the position sensor arrangementillustrated inis only exemplary and highly simplified. Depending on the number of individually movable tool slidesin the embodiments illustrated here, three or four position sensorsare present that create one position sensor value Pi respectively and transmit the latter to the control unit. In the embodiment according to, three position sensor values P, P, Pare provided to control unit, whereas in the embodiment according to, four position sensor values P, P, P, Pare provided for control unit.

The control unitis configured to determine the position and movement of the tool slidesin longitudinal direction L, depending on the received position sensor values Pi and to control the position and movement by means of control signals Ai.

The control unitis configured to carry out an adjustment or referencing for each present tool pair,and to bring the first cold forming rackand the second cold forming rackof each common tool pair,in a defined reference position Ri (i=1, 2). The reference position Ri is a relative position between the two cold forming racks,of a common tool pair,in longitudinal direction L. Relative to this reference position Ri, the cold forming racks,move in longitudinal direction L about the same distance respectively and particularly synchronously and thereby opposite to one another.

Parallel to the longitudinal direction L each cold forming rack,can be moved by means of the assigned tool slideeither in a forward direction F or in a backward direction B opposite to the forward direction F. The forward direction F and the backward direction B are one sense of direction of the longitudinal direction L respectively, so-to-speak. Starting from the adjusted reference position Ri, the second cold forming rackis moved about a distance in forward direction F, for example if the first cold forming rackof the same tool pair,is moved about the same distance in backward direction B starting from the reference position Ri. The same applies also for movements with opposite sense of direction (forward direction F or backward direction B) parallel to the longitudinal direction L respectively.

Thus, by means of control unitusing the drive units, the respective reference position Rfor the first tool pairand the reference position Rfor the second tool paircan be individually adjusted. The referencing or adjustment of cold forming racks,of the two tool pairs,is only highly schematically illustrated in. For example, for this purpose the tool slidescan be moved and positioned respectively on which the first cold forming racksof the respective tool pairs,are arranged. Additionally or alternatively, it would also be possible to move the tool slideor the tool slideson which the second cold forming racksare arranged.

The control unitcan determine the reference positions R, Rbased on the respectively detected position sensor values Pi. Due to the referencing of cold forming racks,of a respective tool pairorrelative to one another, it is guaranteed that the desired pitch of the profileon the workpieceis achieved with the required accuracy. Pitch errors during manufacturing of the profileare reduced or eliminated.

Following the referencing, workpiecescan be deformed in order to create the profilerespectively (). Thereby the tool slidescarry out a movement in longitudinal direction L respectively, that is either in forward direction F or in backward direction B, so that the first cold forming rackand the second cold forming rackof each tool pair,move oppositely. During the progress schematically illustrated inthe first cold forming racksare moved in backward direction B and the second cold forming racksare moved in forward direction F. The path length s that the tool slidesand thus the cold forming racks,travel thereby have equal lengths.