Method for controlling a piecing process for re-piecing a yarn at a workstation of a textile machine

Description

[0001] The present invention relates to a method for controlling a piecing process for piecing a yarn at a workstation of a textile machine, in particular for re-piecing a yarn on a spinning unit of a spinning machine, using a piecing device. During the piecing process, several work steps preparatory to the actual piecing process are performed one after the other in a chronological sequence. Each work step is assigned a predetermined time period within which the respective work step is performed.

[0002] The piecing of a thread after a thread break or after a clearing cut is largely automated in modern open-end spinning machines, with the piecing being carried out either by a robot that can be moved along the spinning stations of the open-end spinning machine or by handling devices located on the spinning station itself. In any case, piecing a thread always requires several preparatory steps, which are carried out sequentially or sometimes in parallel. These steps can include, for example, locating a thread end that has run onto the bobbin on the bobbin surface, rewinding the thread end from the bobbin, preparing the yarn end for re-spinning, cleaning the spinning element, returning the prepared yarn end to the spinning element, and the like.In contrast, the actual piecing process begins with the return of the thread end to the spinning element.

[0003] Likewise, when splicing a thread on a winding machine or performing other thread joining processes on textile machines, several preparatory work steps are required in chronological order one after the other or sometimes in parallel.

[0004] In conventional textile machines, the individual work steps are always performed with a constant cycle time. This means that the time required for each piecing step is fixed and always lasts the same length, even in different piecing processes. The cycle time is selected so that, on the one hand, an advantageous, short cycle time is achieved for this step, in order to minimize downtime of the textile machine's workstation, while, on the other hand, an acceptable success rate is achieved for this piecing step, thus avoiding time-consuming repetitions of piecing processes.

[0005] In order to improve the success rate of individual work steps, some measures have already been proposed.

[0006] For example, DE 35 02 118 A1 describes a pneumatic cleaning process for cleaning the friction surfaces of a friction spinning machine, in which the timing and duration of the pneumatic cleaning are controlled depending on the expected degree of contamination. However, no further details are provided on how the expected degree of contamination is determined or how the cleaning duration is set.

[0007] DE 44 18 743 C2 describes an optimization of the thread search process intended to improve the reliability of finding the thread on the bobbin surface. A sensor monitors the suction of the thread end through a suction nozzle. If the thread end is missing after a specified period of time, the bobbin's rewind speed is reduced, for example, to less than a third of the usual rewind speed, in order to expose the thread end to the suction air flow for a longer period, thus facilitating the suction of the thread end.

[0008] DE 10 2012 100 553 A1, on the other hand, describes an adjustment of the yarn end preparation parameters, including the duration of the yarn end preparation, depending on the success of the yarn end preparation. If the yarn parameters of the piecing machine are within a specified tolerance range, the yarn end preparation parameters remain unchanged; however, if they are outside the tolerance range, an adjustment is made.

[0009] Such measures can achieve overall economical operation of a textile machine. However, such control of individual work steps, which is geared towards the success rate, often has a negative impact on the machine's efficiency.

[0010] The object of the present invention is therefore to propose a method for controlling a piecing process by means of which an improved machine efficiency can be achieved.

[0011] The problem is solved with the features of the independent claims.

[0012] In a method for controlling a piecing process for piecing a yarn at a workstation of a textile machine using a piecing device, several work steps that prepare for the actual piecing process are carried out in chronological order. Each work step is assigned a predetermined time period within which the respective work step is carried out. The piecing device can be provided either on a maintenance device that can be moved along the workstations of the textile machine or as a workstation-specific piecing device at the individual workstations of the textile machine. The textile machine can be designed, for example, as a winding machine or a spinning machine.The invention can be used on any textile machine on which a yarn is produced or processed and on which, after a production interruption, the yarn must be returned to the regular process on the textile machine. Accordingly, a piecing process is understood here to mean the re-spinning of a yarn on a spinning machine, as well as splicing on a winding machine, or other yarn joining processes.

[0013] It is now provided that the predetermined time duration is variable for at least one of the work steps, wherein the time duration for the work step of searching for a yarn end that has run up onto a bobbin and / or for the work step of returning the yarn end to the work station of the textile machine is variable, wherein the current time duration for the work step of searching for a yarn end that has run up onto a bobbin and / or for the work step of returning the yarn end to the work station of the textile machine is determined depending on a yarn character of the yarn currently being produced. In this case, at least the time duration for searching for a yarn end that has run up onto a bobbin and / or at least the time duration for returning the yarn end to the work station of the textile machine is varied.The current time period is determined by setting a value of a rewind speed depending on the yarn character of the currently produced yarn.

[0014] According to an advantageous embodiment of the method, the current duration of the at least one work step can additionally also be determined as a function of a utilization of the attachment device and / or a success rate of the work step and / or as a function of a success of the individual work step.

[0015] Preferably, the duration of the at least one work step is determined at least for each production batch as a function of the yarn character of the yarn produced. It is thus possible, for simple applications in which the yarn is easy to handle in the respective work step due to its yarn character, to significantly reduce the duration of this work step without thereby impairing the success rate of the respective work step. Conversely, for more difficult applications in which a certain work step is to be expected to fail more frequently, this work step can be carried out more slowly, i.e. with a longer cycle time, in order to increase the success rate of this work step. The duration can be varied within wide limits and, depending on the current yarn character, can also be set to 0 s, i.e. an individual work step can be omitted entirely.On the other hand, if the piecing device is underutilized or if certain yarn characteristics are present, certain work steps can also be added by setting a specific time duration for them, starting from a standard time duration of 0s.

[0016] It is also possible to specify the duration of a work step depending on the success rate of that work step. For example, if a work step fails in the previous preparation process, the cycle time of the relevant work step in the current preparation process can be increased. It is of course also conceivable to record the success rate of a work step across multiple preparation processes and to redefine the duration of the relevant work step depending on the success rate. Regardless of the criteria used to determine the duration, the duration for the relevant work step can be set permanently or temporarily, allowing for continuous adjustment or optimization during ongoing operations.

[0017] It is also possible to determine the duration of a work step depending on the success of that individual step. This means, for example, that if a step fails in a piecing process, the respective step is repeated, but the duration for that step is changed, in particular, increased.

[0018] Since the duration of the individual work steps is often in the range of several seconds, this can result in a significant reduction in the overall cycle time, during which unproductive downtimes at work stations can be avoided.

[0019] In addition, the wide range of variable durations for specific work steps also offers the possibility of adaptation to specific operating conditions. For example, the duration of a work step can also be determined based on the utilization of the piecing device. A shortened cycle time can be specified for a specific work step if the utilization of the piecing device is high because of frequent maintenance calls or, in the case of movable piecing devices, because another piecing device has failed. This allows overall downtime at the work stations to be kept to a minimum. Conversely, if only a few piecing processes need to be performed, the cycle time of the relevant work step can also be increased to ensure the success of the respective work step and avoid operator requests.

[0020] The duration of the individual work steps can either be determined automatically by a control device based on stored criteria or manually. This also allows for the possibility of manually setting longer durations to achieve greater process reliability, for example, when limited operating personnel are available or a particularly high-quality yarn is desired, and vice versa. According to the invention, however, the current duration of at least one work step is determined independently by a control unit of the textile machine.

[0021] On a spinning machine, the individual work steps preparing for piecing include at least returning the yarn end to the spinning element, preferably also preparing the yarn end for re-piecing and / or cleaning the spinning element.

[0022] When splicing on a winding machine, the preparatory steps for piecing or splicing also include at least introducing the yarn into the splicing chamber. Further steps may include locating the yarn end that has wound onto the bobbin, rewinding, clamping, and cutting the yarn end to length, as well as preparing the yarn end for splicing.

[0023] According to the invention, the time required for locating a yarn end that has run onto a bobbin and / or returning the yarn end to the workstation of the textile machine, in particular to a spinning unit, can be varied depending on the yarn character of the produced yarn. For simple applications, the cycle time or time required for locating and / or returning can be shortened by up to 10 seconds or more. For example, a coarse yarn can generally be located comparatively quickly on the bobbin surface, so that the time required for thread searches for such yarns can be shortened. In addition, the time required for feeding the yarn end to a handling element of the piecing device can also be varied.

[0024] According to the method, various yarn characteristics are stored in a knowledge memory, each of which is assigned at least one suitable rewinding speed value for the work step of locating a yarn end that has run onto a bobbin and / or for the work step of returning the yarn end to the work station of the textile machine. A rewinding speed value corresponding to the yarn characteristics of the currently produced yarn is then selected from the knowledge memory. This is done automatically by the control device.

[0025] The duration for each work step is generally determined by the specified settings for performing that work step. According to the invention, the current duration for the respective work step is determined by setting a rewinding speed depending on the yarn characteristics of the currently produced yarn.

[0026] For example, a coarse, less delicate yarn can be unwound at a high rewind speed during thread search, as this avoids yarn damage or further thread breakage, thus saving time. To protect the more delicate yarn, a low rewind speed can be specified.

[0027] Conversely, however, it is often difficult to feed a coarse, comparatively stiff yarn back into the spinning element. The time required for rewinding the yarn back into the spinning element can therefore be extended to ensure successful rewinding. This is preferably achieved by setting a lower rewind speed during rewinding.

[0028] This results in a significant increase in machine efficiency, as significant time savings are possible when rewinding simple yarns. By setting slower rewinding speeds where necessary, yarn damage can be avoided and unnecessary repetitions of the respective work step can be avoided, thus increasing overall efficiency.

[0029] According to the invention, different yarn characters are stored in a knowledge memory. At least one suitable rewinding speed is each assigned to these different yarn characters. In the method, a rewinding speed corresponding to the yarn character is selected from the knowledge memory for the yarn currently being produced, i.e. in the respective production batch. An optimized rewinding speed can therefore be stored as a standard value for each yarn, so that the best compromise between fast processing and a high success rate of the respective work step is achieved. It is of course also possible to store further values or value ranges for specific, additional conditions for one or more yarn characters. If none of these additional conditions are met, the standard value is selected from the knowledge memory.However, if such an additional condition exists, a value that corresponds to and is optimized for this condition is selected from the knowledge store. It is also possible to store permissible ranges in the knowledge store within which an adjustment is permitted.

[0030] Preferably, the rewinding speed for the thread search step is determined by the rotational speed of a roller driving the bobbin. In a spinning machine, the rewinding speed for the return to the spinning unit step is determined by the rotational speed of the piecing rollers.

[0031] It is advantageous to specify a starting value for the rewinding speed, preferably based on experience, and to adjust the rewinding speed based on the starting value over several piecing processes depending on the success rate of the respective work step, in particular reducing it until a specified minimum success rate is reached. This allows for a temporal optimization of the respective work step while still maintaining a high level of process reliability.

[0032] It is particularly advantageous if the rewinding speed determined in the manner described above is selected as the working value for the rewinding speed for subsequent piecing processes once the specified minimum success rate has been reached. Thus, the optimal rewinding speed only needs to be determined at the beginning of a production batch; once this is found, the subsequent piecing processes can then be carried out at the optimized rewinding speed, referred to here as the working value, instead of with the starting value based on empirical values.

[0033] It is also advantageous if the optimized work value for the rewinding speed determined in this way is stored in the knowledge memory and specified as the starting value for a subsequent production batch. This eliminates the need to determine a work value based on a minimum success rate for subsequent production batches involving the same yarn type.

[0034] Preferably, the knowledge storage is connected to the control device, so that the determination of a work value can be carried out automatically by the control device, and the newly determined work values can be automatically stored in the control device or the knowledge storage. The control device is thus designed to be self-learning.

[0035] In addition to the work steps of searching for the thread and feeding it to a working element of the piecing device or returning it to the work station, in particular the spinning unit, the duration of other work steps can of course also be changed depending on the yarn character or the capacity utilization of the piecing device.

[0036] It is therefore also advantageous if the time for cleaning a spinning element of the spinning unit, in particular a spinning rotor, can be varied on a spinning machine. In the case of a movable device for cleaning the spinning element that is part of a movable maintenance or piecing device, the time can be varied depending on the load of the movable device. For example, during periods of high load, a shorter cleaning time can be set to save time and avoid downtimes at other workstations that are also waiting for the device. Conversely, for yarn types where a high degree of contamination is to be expected, the time for cleaning the spinning element can also be extended to avoid problems during piecing and to ensure process reliability. Typical rotor cleaning times are, for example, in the range of 1 - 6 seconds.Here too, the variance of the cycle time can be up to 10 s or more, so that the machine efficiency can be significantly improved by such a shortening of the cleaning time.

[0037] According to another embodiment of the method, the duration of at least one of the work steps can be varied by changing the travel speed of a handling element of the piecing device. For example, with thicker, more robust yarns, handling elements for transferring or storing a yarn end can be moved more quickly.

[0038] It is also advantageous if the actual duration of at least one work step is determined depending on the bobbin format of the respective production batch. For example, for a cylindrical bobbin, the acceleration or deceleration of the bobbin during piecing or during scheduled spinning stops can occur more quickly than for a conical bobbin.

[0039] Furthermore, it is advantageous if the work result of the work step is determined during the execution of at least one work step and the current duration and / or the intensity of the work step is determined during the execution of the work step depending on the determined work result. For example, in the case of mechanical rotor cleaning, the work result can be determined by drawing conclusions about the cleaning result from the current consumption of the motor driving the cleaning device. The time for rotor cleaning is extended or shortened accordingly depending on the work result by continuing cleaning until the current consumption corresponds to that of a clean rotor. A different time period can therefore also be specified for each individual cleaning cycle within predetermined minimum and maximum time periods.

[0040] Further advantages of the invention are described with reference to the following exemplary embodiments. They show: Figure 1 a spinning station of a spinning machine with several handling elements for spinning a yarn in a schematic side view and Figure 2 a schematic representation of the adjustment of the time duration for a specific work step.

[0041] Figure 1shows a spinning station 2 of a spinning machine 1 in a schematic side view. The spinning machine 1 usually has a plurality of spinning stations 2 arranged next to one another, each of which has a plurality of working elements for producing a yarn G. Each spinning station 2 has at least one spinning unit 7 with a spinning element 8 and a take-off element 10. The yarn F produced by the spinning element 8 is taken off during regular spinning operation by a take-off device 11 and fed to a bobbin 6, onto which it is wound. For this purpose, the bobbin 6 is rotatably and drivably mounted, with a roller 4 being provided in the present case to drive the bobbin 6. During regular spinning operation, the bobbin 6 is driven by the roller 4 in the yarn take-off direction (dashed arrow). Alternatively, the bobbin 6 can also be driven by a direct drive.

[0042] Furthermore, the spinning machine 1 has a piecing device 5, which has several handling elements 14, 15, 16, 17, 18, 19, 20, 21, 22 for piecing the yarn G. In the present case, the handling elements are a suction nozzle 14, a pneumatic handling element 15, a yarn catcher 16, a feed unit 17 with a clamping device 18, a yarn preparation unit 19 and a separating device 20, as well as a pair of auxiliary rollers 21. According to the present example, the piecing device is arranged within a maintenance device 3 that can be moved along the spinning stations 2. However, a piecing device can also be arranged at the spinning station 2. In addition, the handling elements 14, 15, 16, 17, 18, 19, 20, 21, 22 listed here are merely examples.Depending on the design of the spinning machine 1, some of the handling elements 14, 15, 16, 17, 18, 19, 20, 21, 22 mentioned are not required, or other handling elements 14, 15, 16, 17, 18, 19, 20, 21, 22 are provided instead of the aforementioned elements, which can also be combined into different assemblies. Some of the handling elements 14, 15, 16, 17, 18, 19, 20, 21, 22 can also be equipped with a sensor S to monitor the presence of the yarn G. Sensors S can also be provided which detect the correct movement or pivoting of individual handling elements 14, 15, 16, 17, 18, 19, 20, 21, 22 or assemblies. In the present case, sensors are shown in the suction nozzle 14 and in the pneumatic handling device 15. Another sensor S is arranged in the usual way in the thread path at the spinning station 2 to monitor the presence of the yarn G and, if necessary, also the quality of the yarn G.

[0043] If a thread break occurs or a clearing cut is performed, the end of the yarn G runs onto the still rotating bobbin 6 and must first be located on the surface of the bobbin 6 for piecing (thread search step). For this purpose, according to the present example, the bobbin 6 is driven by a roller 4 of an auxiliary drive 22 against the regular take-off direction (solid arrow). Meanwhile, the suction nozzle 14 is pivoted in the direction of the bobbin 6 (dashed line) in order to locate and grasp the yarn end G'. Once the suction nozzle 14 has grasped the yarn end G', it is pivoted into the position shown in solid lines, whereby the yarn G is presented to a pneumatic handling device 15. From the solid line position, the yarn end G' can now be grasped by the yarn catcher 16 and presented to the feed unit 17 by pivoting the yarn catcher 16 into the dashed line position.At the same time, the yarn end G' is inserted into the pair of auxiliary rollers 21, by means of which, after piecing has been completed, the yarn F is temporarily withdrawn from the open-end spinning device 7.

[0044] In the yarn end preparation step, the yarn end G' is first clamped in the clamping device 18 and separated by a separating device 20. This creates a new yarn end G', which is then prepared for re-tensioning in the yarn preparation unit 19.

[0045] Meanwhile, the work step of cleaning the spinning element 8 can be carried out in the spinning unit 7.

[0046] After the yarn end G' has been prepared, the work step of feeding the prepared yarn end G' to the spinning unit 7 now takes place. For this purpose, the movably mounted feeding unit 17 is moved from its preparation position shown in solid lines into a feeding position shown in dashed lines and the yarn end G' is thereby placed in front of the take-off device 10.

[0047] This is followed by the work step of returning the yarn end G' to the spinning unit 7 or to the spinning element 8. For this purpose, the auxiliary roller pair 21 and / or a further auxiliary roller pair 21 (not shown), which is arranged on the feed unit 17, is driven counter to the regular take-off direction, so that the yarn end G' finally returns to the effective area of the spinning element 8.

[0048] In the prior art, the individual work steps for all applications were always performed with a fixed cycle time or duration, resulting in an overall temporally constant cycle sequence. The duration for each work step was generally set such that a good success rate for the respective work step was achieved even with more difficult yarns G.

[0049] In contrast, it is now planned to adapt the cycle time of at least individual work steps to the yarn character GC of the currently produced yarn G in order to achieve time savings and thus increase machine efficiency. Likewise, the cycle time of a specific work step can also be extended if this seems necessary in a more difficult application due to a lower success rate of the respective work step.

[0050] For example, in the spinning machine 1 shown here, an adjustment of the cleaning time of the spinning element 8 or an adjustment of the yarn end preparation time is possible. Likewise, a time period can be specified for the thread search, for the transfer of the yarn G through the yarn catcher 16, for the feeding of the yarn end G' to the spinning unit 7, and for the return of the yarn end G' to the spinning unit 7.

[0051] In order to enable convenient setting of the duration of a work step, a knowledge memory 13 is provided in the present case, which is operatively connected to a control unit 12 of the spinning machine 1. Various yarn characters GC 1 , GC 2 , ..., GC n are stored in the knowledge memory 13, each of which is assigned at least one suitable value W 1 , W 2 , ..., W n of the duration for the respective work step. It is thus possible, after input of the yarn character GC of the current application, to obtain a value W suitable for this yarn character GC through the knowledge memory 13. The stored values W are based on experience from past piecing processes and are permanently stored in the knowledge memory 13 after a first execution. The selection of a suitable value W for the current yarn character GC can be carried out by an operator.In this case, the control unit 12 merely suggests a specific, suitable value W for the current yarn character GC, which, however, must still be confirmed by the operator. Only then is this value W adopted by the control device 12 to control the piecing device 5 or its handling elements 14, 15, 16, 17, 18, 19, 20, 21 accordingly. However, it is particularly advantageous if the selection and adoption of a suitable value W takes place automatically by the control unit 12.

[0052] According to a particularly advantageous embodiment, the control unit 12 is designed as a self-learning control unit 12, so that the values W stored in the knowledge memory 13 for specific yarn characteristics GC can be changed. It is particularly advantageous if the initially selected value W of the duration of a work step for a specific yarn character GC can also be automatically adjusted during the spinning process or during a production batch. A corresponding procedure for adjusting the duration of a specific work step is shown schematically in Figure 2 shown.

[0053] While for some work steps the appropriate time duration can be stored directly as the value W, in some other work steps the time duration for a specific work step results from certain setting values for carrying out this work step. Such setting values can be, for example, the travel speed of handling elements 14, 15, 16, 17 such as the suction nozzle 14, the pneumatic handling element 15, the yarn catcher 16, and in particular the feed unit 17. Likewise, the setting values can be the rewinding speed of the yarn G or certain rotational speeds, for example the rotational speed of the auxiliary roller pair 21 or the roller 4 for driving the bobbin 6, or other parameters. In this case, the value W stored does not represent the corresponding time durations, but rather suitable values for such speeds or rotational speeds.

[0054] Here, the procedure is explained using the example of the work step of thread search or of returning the yarn end G' to the spinning unit 7. In both cases, specific values W of the rewinding speed of the yarn G' are stored as setting values. As described in relation to Figure 1, for each yarn character GC 1 , GC 2 , ... GC n at least one suitable value W 1 , W 2 , ..., W n of the rewinding speed is stored in the knowledge memory 13. At the start of the spinning process, in particular at the start of a specific production batch, the operator enters the yarn character GC of the current application via the control unit 12. Furthermore, it is possible for the operator to enter a specific, desired minimum success rate for the relevant work step. However, in contrast to the illustration shown, such a minimum success rate can also be permanently stored in the control unit 12.From the knowledge memory 13, the appropriate value W for the entered yarn character GC can now be selected from the stored values W 1 , W 2 , .., W n and output as the starting value SW via the control unit 12. This starting value SW can now be specified either automatically or by the operator as a suitable value W for performing the respective work step.

[0055] After preferably several piecing processes have been carried out with this predefined value W, a check can be made to determine whether the desired, previously entered minimum success rate or the permanently stored minimum success rate has been achieved. If this is the case, the predefined value W is also used as the working value AW for future piecing processes, and further adjustment of the value W is not necessary. If, however, the minimum success rate is not achieved, the control unit 12 reduces the predefined value W, and this reduced value W is in turn specified for the execution of the respective work step. The correction of the value W, in this case the reduction of the value W of the rewind speed, is carried out until the predefined minimum success rate is finally reached.Once this is the case, the value W determined in this way is again specified as the work value AW for future batching processes, and no further adjustment is necessary. In addition, the work value AW determined in this way can be stored in the knowledge store 13 to serve as the starting value SW for future production batches.

[0056] Alternatively, or in addition to the previously described variation in the duration depending on the success rate of the respective work step across multiple preparation processes, the duration can also be varied within a single preparation process depending on the success of the individual work step. This is the case if a work step was unsuccessful and needs to be repeated.

[0057] For example, the rewinding speed can be changed when searching for a yarn end G that has accumulated on a spool 6 (thread search) to improve the chances of success of the thread search. A rewinding speed value W is selected for the thread search, and the thread search is initially started with this selected value W as the starting value SW of the rewinding speed of, for example, 1 m / s. The time duration for the work step of searching for the yarn end G is set, for example, to a search duration of 5 s as the starting value SW, and the work step is performed at a regular vacuum level.

[0058] If this step is successful, the starting value SW of the rewind speed is adopted as the working value AW for the subsequent piecing processes at other work stations. Likewise, the duration of the step and the vacuum level for the subsequent piecing processes remain unchanged.

[0059] If the work step fails, the selected starting value SW is changed, and the corresponding work step—here, the thread search—is repeated with the changed value W. For example, the rewind speed is now reduced to 0.5 m / s. The duration and the vacuum level remain unchanged. If the thread search is successful, the reduced rewind speed of 0.5 m / s is adopted as the working value AW for the subsequent piecing processes.

[0060] If the work step fails again within the same piecing process, the reduced rewind speed of 0.5 m / s can also be adopted as the working value AW for repeating the work step and for subsequent piecing processes. However, further values W are now adjusted and the relevant work step is repeated with the adjusted values W. For example, the vacuum level can now be increased. If the work step fails again, the time for the thread search can be increased starting from the starting value SW, in this case 5s. If the relevant work step is then successful, the values W for future piecing processes are reset to the starting values SW.

[0061] Only if the respective work step frequently fails in various piecing processes with the starting values and thus the success rate of the respective work step is low, the changed values W, here the reduced rewinding speed, as described above, are permanently or at least for the respective batch adopted as values W in the control unit.

[0062] In this case, the determination of suitable values W was described based on the rewinding speed of the yarn G. In a similar way, suitable values W can also be determined for other setting values as described above. It is, of course, not always necessary to start with a relatively high starting value SW and gradually reduce this. If more difficult applications are frequently run that require slower cycle times, it is also possible to start with a low rewinding speed or a low value W and gradually increase this until a just acceptable success rate is achieved. The success rate of a work step can, as in Figure 1 described, for example by means of sensors S.

[0063] Furthermore, the described procedure, with the determination of suitable values W for specific setting values using a knowledge memory 13, can also be applied analogously to other textile machines. For example, in a winding machine, an adjustment of the time duration for yarn end preparation, for thread search, for transferring the yarn G by a working element of the textile machine, for feeding the yarn end G' into the splicing chamber, and, if necessary, for returning the yarn end G' to the work station could be specified.

[0064] This allows the cycle time to be optimized for each individual work step and each yarn type (GC) to achieve optimal efficiency for the respective application. Particularly when such cycle time optimization is performed for multiple work steps of the piecing process, significant time savings and thus increased efficiency are achieved. List of reference symbols

[0065] 1 Spinning machine 2 Spinning station 3 Maintenance device 4 Roller for bobbin drive 5 Piecing device 6 Bobbin 7 Spinning unit 8 Spinning element 10 Take-off device 11 Take-off device 12 Control unit 13 Knowledge storage 14 Suction nozzle 15 Pneumatic handling device 16 Yarn catcher 17 Feeding unit 18 Clamping device 19 Yarn preparation unit 20 Separating device 21 Pair of auxiliary rollers 22 Auxiliary drive GGarn G'Yarn end SSensor WValue SWStart value AWWorking value GCGarn character

Claims

1. A method for controlling a piecing process for piecing a yarn (G) at a working station of a textile machine, in particular a piecing process for re-piecing a yarn (G) at a spinning unit (7) of a spinning machine (1), by means of a piecing device (5), in which a number of working steps which prepare the actual piecing process are carried out successively in a chronological sequence, wherein the working steps are each assigned a predefined time period within which the respective working step is carried out, wherein the predefined time period can be changed for at least one of the working steps, characterized in that the time period can be changed for the working step of searching for a yarn end (G') which has run onto a bobbin (6) and / or for the working step of returning the yarn end (G') to the working station of the textile machine, wherein the current time period of the at least one working step is defined as a function of a yarn characteristic (GC) of the currently produced yarn (G), wherein the current time period is defined by defining a value (W) of a rewinding speed as a function of the yarn characteristic (GC) of the currently produced yarn (G), wherein different yarn characteristics (GC) are stored in a knowledge memory (13), each of which is assigned at least one suitable value (W) of the rewinding speed for the working step of searching for a yarn end (G') which has run onto a bobbin (6) and / or for the working step of returning the yarn end (G') to the working station of the textile machine, and in that a value (W) of the rewinding speed which corresponds to its yarn characteristic (GC) is selected from the knowledge memory (13) for the currently produced yarn (G), wherein the current time period of the at least one working step is determined independently by a control unit (12) of the textile machine.

2. The method according to the preceding claim, characterized in that the current time period of the at least one working step is defined as a function of a success rate of the working step over a number of piecing processes and / or as a function of a success of the individual working step within a single piecing process.

3. The method according to one of the preceding claims, characterized in that the time period for feeding the yarn end (G') to a handling element (15, 16, 17, 18, 19, 20, 21) of the piecing device can be changed.

4. The method according to one of the preceding claims, characterized in that the time period for cleaning a spinning element (8) of the spinning unit (7) can be changed.

5. The method according to one of the preceding claims, characterized in that the time period for at least one of the working steps can be changed by changing a movement speed of a handling element (14, 15, 16, 17, 18, 19, 20) of the piecing device (5).

6. The method according to one of the preceding claims, characterized in that an initial value (SW) for the rewinding speed is predefined and in that the rewinding speed is adapted, in particular reduced, starting from the initial value (SW) over a number of piecing processes as a function of a success rate of the relevant working step until a predefined minimum success rate is reached.

7. The method according to the preceding claim, characterized in that the value (W) of the rewinding speed when the predefined minimum success rate is reached is selected as a working value (AW) for the rewinding speed for subsequent piecing processes and / or is stored in the knowledge memory (13) and is predefined as an initial value (SW) for a subsequent production batch.

8. The method according to one of the preceding claims, characterized in that the current time period of the at least one working step is defined as a function of a bobbin format of the respective production batch.

9. The method according to one of the preceding claims, characterized in that during the performance of the at least one working step, the working result of the working step is determined and the current time period and / or the intensity of the working step during the performance of the working step is defined as a function of the determined working result.

10. A textile machine (1) having a piecing device (5) for piecing a yarn (G) at a working station of the textile machine and having a control unit (12) for controlling a piecing process for piecing the yarn (G), wherein the piecing process comprises a number of working steps which prepare the actual piecing process and which are each assigned a predefined time period, wherein the predefined time period can be changed for at least one of the working steps, characterized in that the control unit is designed to operate the textile machine (1) according to a method according to one of the preceding claims, wherein the control unit is set up to independently define the time period for the working step of searching for a yarn end (G') which has run onto a bobbin (6) and / or for the working step of returning the yarn end (G') to the working station of the textile machine as a function of a yarn characteristic (GC) of the currently produced yarn (G).