Patent Application
20190002227
The invention relates to a method for regulating the processing of a material web, in particular a packaging material web, that has register marks which are guided past a processing device for the purpose of processing. The invention also relates to an apparatus for the processing of a material web, in particular a packaging material web, on a processing device having at least one drive roller for driving the material web, having at least one processing tool for carrying out said method having at least one sensor for capturing register marks of the material web guided past the sensor, having an evaluation device for determining a deviation of an actual position, corresponding to the capturing event of a register mark by the at least one sensor of at least one processing tool of the processing device from a predetermined position of the at least one processing tool for the same capturing event, and having a regulating device for regulating the actual processing position of the at least one processing tool on the basis of the deviation between the actual position and the predetermined position of the at least one processing tool determined by the evaluation device.
Material webs are in many cases processed in a number of successive steps, wherein each individual processing step is repeated at predetermined distances along the material web. In this way, material webs with a number of identical sections arranged one after another can be manufactured. During processing, the material web is typically driven by at least one drive roller.
Material webs can, by way of example, be provided with a multicolour print. In order to ensure a high print quality in the process, the individual printing steps must be synchronised, i.e. there must be congruency between them. Alternatively or additionally, depending on the material web and the intended use of the material web, other processing steps, such as for example stamping, cutting, folding, embossing and perforation, may be coordinated, so that the most precisely manufactured material webs or material blanks as possible can be obtained.
These basic principles are to a large extent independent of the material web. The material webs to be processed can, by way of example, be single-layer materials. However, multilayer material webs may also be involved comprising a composite and/or laminate. These may, by way of example, be used as packaging material. The packaging material, by way of example, involves a packaging material laminate with individual layers of different materials bonded to one another, providing the packaging material laminate with differing properties. For foodstuffs, in many cases what is known as cardboard/plastic packaging material laminates or composite cardboard packaging is involved, formed from a laminate comprising a cardboard layer and outer, in particular thermoplastic, plastic layers, for instance in polyethylene (PE). The cardboard provides the packaging with sufficient stability to allow the packages to be easily handled and, by way of example, stacked. The plastic layers can be sealed and protect the cardboard from moisture and the food from absorption of undesired substances from the package. In addition, further layers such as barrier layers, for instance comprising aluminium, polyamide and/or an ethylene-vinyl alcohol may be provided, preventing diffusion of oxygen and other gases through the package. Such material webs are relatively thick and relatively rigid, which can make the precise processing of the material webs in successive steps difficult.
To regulate the processing of a material web that has register marks which are guided past a processing device for the purpose of processing what is known as register regulation or print marks regulation is used. To this end, the material web is provided with register marks or print marks at certain distances, that can be captured by an optical sensor, immediately they pass the sensor. Here, print marks are represented by register marks applied by printing, which can basically also be provided in a manner other than printing.
Capture of the register marks usually takes place at a position corresponding to a whole multiple of repeat lengths of the material web. The repeat length is determined by the length of identical sections of the material web, for instance blanks separated out from the material, in particular packaging material blanks. In this case a repeat length would, by way of example, be defined by the distances from the front edges of the subsequent packaging material blanks in the material web. Alternatively or additionally, the repeat length may be understood as the distance between two identical processing points along the material web. If, by way of example, the same decoration is always printed, the repeat length would be the distance between two identical points of successive decorations. The register marks are preferably similarly provided at distances corresponding to the repeat length.
If a register mark is captured by the sensor, also captured is the position of the subsequent processing tool at the time of capturing the register mark, i.e. the capturing event. This position is then compared with the predetermined position of the processing tool, which the processing tool should have been in at the time of capturing the register mark. From this comparison a deviation is derived between the two positions, which is optimally equal to zero but if necessary can also be positive or negative. In order to compensate for this deviation, a regulating device, on the basis of the amount and the sign of the deviation, regulates the position of the processing tool. To this end, the processing tool is briefly accelerated or briefly braked. This means that the drive of the processing tool briefly moves this somewhat faster or somewhat slower. The length of time over which the acceleration and/or braking or deceleration takes place, is typically shorter than the length of time between the capture of two successive register marks by the at least one sensor. The purpose of the brief acceleration or braking is therefore to influence the position of the processing tool such that this corresponds with the predetermined position of the processing tool. Therefore, and due to the usually only slight deviations, the acceleration or braking only takes place very briefly. Because of the usually very high speed of the material strips, the braking or deceleration or the acceleration is performed in a pulsed manner.
Practice shows that a very great regulation effort is required to achieve a precise processing of the material webs. All the more so, if inaccuracies from previous work steps have to be taken into account in subsequent processing steps. By way of example, during a processing a register mark can be introduced for a subsequent processing with another processing tool. By way of example, in one processing device part of the material web can be punched or a fold line provided in the material web. In order now to align the subsequent processing precisely with the previous processing and thus take into account any errors in the previous processing, the edge of the material web around the stamped part of the material web or the fold line can be used as a register mark for a subsequent processing step, for instance in order to align this subsequent processing with the location of the stamping or folding.
Furthermore, slip occurring during the transport of the material web and/or an acceleration or a deceleration in the speed of transport of the material web can cause the register marks not to be captured by the sensor in the precise chronological sequence envisaged. Therefore, on the one hand deviations in the regularity of capture of the register marks and deviations in the position of the processing tools in relation to the predetermined position of the processing tools can occur independently of one another. The regulation must seek to balance out these two deviations.
This is particularly problematical for those applications in which the intention is to achieve very high path velocities and/or strong accelerations of the material web. With increasing interest in more efficient production and ever-lower unit costs, there is a constant focus on increasing even more the path velocities and the accelerations of the material web during the processing of the material web. However, time and again this leads to operating states in which the regulation has neither sufficient speed nor accuracy to balance out errors relating to the material web and/or the processing tool or to avoid these. If in doing so, predefined error tolerances are exceeded, parts of the material web must be rejected as scrap. Thus, there is an optimisation problem of allowing high path velocities and strong accelerations and simultaneously lowering scrap, so that production can be as economical as possible. This optimisation problem has to date not been solved satisfactorily, in particular for packaging material webs.
The object of the present invention is therefore to design and develop the method and device of the abovementioned type, respectively, in such a way that high path velocities and accelerations of the material web when starting up the device for processing the material web can be achieved with simultaneous low levels of scrap.
This problem is solved according to claim 1 by a method for regulating the processing of a material web, in particular a packaging material web, that has register marks which are guided past a processing device for the purpose of processing,
The abovementioned problem is also solved with an apparatus according to the preamble of claim 12, in that the evaluation device is configured to determine a pilot-control value as a function of the path velocity of the material web in the area of the at least one sensor on the basis of successive capturing events of register marks by the at least one sensor, wherein the pilot-control value is determined on the basis of a correlation between the actual distance of successive register marks in relation to the measurement system of the at least one drive roller, in particular in relation to the angular difference and/or the circumferential difference of the drive roller, and an expected distance between the register marks in relation to the measurement system of the at least one drive roller, and in that a control device, preferably a pilot-control device, is provided for adjusting the speed of the at least one processing tool as a function of the pilot-control value determined.
According to the invention the regulation of the position of the processing tool of the processing device is supplemented by a control of the speed of the processing tool. In doing so, the speed of the processing tool is not determined on the basis of the speed of a drive of the material web as such, for instance the angular speed or the circumferential speed of a roller or roll for driving the material web or on the basis of the speed of the motor for driving the material web. On the contrary, the speed of the material web or an appropriate speed parameter corresponding to the speed of the material web is captured on the basis of the capture of successive register marks and thus very accurately. The high accuracy is achieved because in the manner described the effective speed of the material web or an appropriate pilot-control value corresponding to the effective speed of the material web, for instance in the form of a speed parameter, is determined.
If the register marks are not provided at precisely predetermined distances on the material web, for instance because execution of the previous processing of the material web, in which, by way of example, the register marks are formed, was defective, then it is not so much a matter of the actual speed of the material web or the predetermined path velocity more one of the relevant speed for the pending processing, thus the effective path velocity, of the material web. This describes, by way of example the speed with which the register marks are introduced to the next processing device or the processing tool. If the intention is to match the processing of the material web with the processing tool to the register marks, the speed of the register marks, which can but do not have to correspond with the absolute speeds of the material web or the predetermined path velocity, is of fundamental importance.
The capture of the path velocity on the basis of the register marks is also therefore more accurate than the determination of the path velocity using the drive for the material web, be this in relation to a motor, the speed of a drive roller or another parameter, because in this way a slippage between drive and material web and/or a stretching of the material web during its transport is also captured. This can then be taken into account in the further processing of the material web.
Finally, the capture of the effective speed of the material web allows the speed of the processing tool to be adjusted to the effective path velocity. In doing so, however, the speed of the processing tool is not regulated but controlled. The control is characterised by an open action flow, in which an input variable influences an output variable according to certain laws or requirements, without the outcome of the influencing being continuously checked or corrected. With regulation, on the other hand, an output variable, also referred to as a control variable or actual value, is continuously captured and compared with a reference variable or a target value. Regulation is therefore characterised by a closed action flow, what is known as a control loop, the purpose of which is to adjust the output variable to the reference variable or the target value.
In other words, the speed of the processing tool is raised if an increased effective path velocity is determined, whereas the speed of the processing tool is lowered, if a decreased effective path velocity is determined. Since the speed of processing tools for the processing of material webs can typically be set with great accuracy and reproducibility, in the present case it is basically superfluous to continuously capture the speed of the processing tool and regulate it by comparison with the predetermined speed of the processing tool. Furthermore, through the control, account is taken of the fact that the desired speed of the processing tool does not for instance have to remain more or less constant, but if necessary can change very quickly, which may in particular be the case when starting up and shutting down the system for processing the material web. A regulation could be easily overstretched by this and lead to an inaccurate or unstable operation of the system.
The material web is in particular a packaging material web, since the method can be used with such material webs particularly advantageously. This applies in particular to packaging materials in the form of packaging material laminates, which in the case of a cardboard/plastic packaging material laminate may have at least one inner cardboard layer and outer, in particular printed, sealable plastic layers. There is also usually at least one further layer, in particular in aluminium. The packaging material laminates are used for the formation of packages, which are usually filled with foodstuffs.
The material web can be easily, reliably and quite accurately driven via the at least one drive roller. This can result in a frictional contact between the drive roller and the material web, so that the material web, by way of example, is at least driven substantially with the circumferential speed of the drive roller. The circumferential speed of the drive roller and the path velocity can then correspond to one another. In the case of driving via a drive roller, the pilot-control value determined on the basis of the capture of the register marks by the at least one sensor, for instance in the form of speed parameter, can easily be correlated to the measurement system of the at least one drive roller. The capturing events of successive register marks will thus, by way of example, be correlated to the distance by which the drive roller has further rotated between the capture of the successive register marks. Here, the corresponding pilot-control value or speed parameter can for the sake of simplicity be correlated to the angular difference and/or the circumferential difference of the rotating roller or drive roller between two capturing events. The angular difference is the angle through which the roller has continued to rotate between the corresponding capturing events and the circumferential difference is the distance by which a circumference point has moved further along the circumference between the corresponding capturing events. With rollers with a circular cross-section, therefore, there is a correlation between the circumferential difference and the angular difference. Thus, it can be determined whether or not the speed of the register marks or the effective path velocity correspond to the expected path velocity or the drive speed of the material web, in order to be able to respond to this appropriately and as necessary.
Furthermore, the evaluation device can use capturing events to determine the actual distance of successive register marks in relation to the measurement system of the at least one drive roller, in particular in relation to the angular difference and/or the circumferential difference of the corresponding roller, and correlate this to an expected distance between the register marks in relation to the measurement system of the at least one corresponding roller. The amount and the sign of the deviations determined in doing so can be very easily used here to adjust the speed of the processing tool. For the sake of simplicity, here the speed of the processing tool can initially be set to be identical to the speed of the drive roller. If a deviation between two speeds has to be taken into consideration, this is captured metrologically in the manner described and taken into consideration by means of the pilot-control value for the purpose of compensation of the deviation. The deviation described can accordingly be used for precisely altering the speed of the processing tool.
Put another way, on the basis of the relationship between the actual distance between the register marks determined in relation to the measurement system of the drive roller and the expected distance between the register marks a pilot-control value can be determined, which can then be passed to the control loop. The pilot-control value alters the speed of the processing tool essentially like a control, while apart from that the position of the processing tool is regulated in particular by means of briefly expressed differential speeds. Here the manipulated variable can in particular be the result of overlaying the pilot control of the speed and the regulation of the position respectively of the at least one processing tool.
The correlation to the measurement system of the drive roller can by way of example be achieved in that for each capturing event a register mark is recorded for the distance of a particular reference point along the circumference of the drive roller from a particular reference location on the circumference of the drive roller. This distance can, by way of example, for one capturing event be 300mm (L1) and for a successive capturing event 405 mm (L2). If the theoretically expected distance between two successive register marks is 100 mm (LT), for the distance of the reference point from the reference location on the successive capturing event an actual value of 400 mm would be expected. The corresponding difference between the actual and expected value in relation to the measurement system is therefore 5 mm (LD) and can be used to determine the pilot-control value.
LD=L2−L1+LT
To begin with, and in particular, it is appropriate to normalise to the expected length value, which can be used as a pilot-control value or for determining a pilot-control value, for instance in the form of a speed parameter (VD), for which the circumferential speed of the drive roller (VA) can be used.
VD=VA·(LT−LD)/LT
Instead of circumferential distances or circumferential lengths, the calculation of a pilot-control value explained here by way of example could also be performed on the basis of angular differences of a reference point of the drive roller from an angular reference of the drive roller.
To allow a better understanding and to avoid unnecessary repetitions, in the following the method and the device of the abovementioned kind are described jointly, without distinguishing in detail between the method and the device respectively. For the person skilled in the art, however, the context will in any case indicate which features are preferred for the device and the method respectively.
In a first preferred form of the method the evaluation device determines as the pilot-control value a speed parameter dependent upon the path velocity of the material web in the area of the at least one sensor in relation to the measurement system of the at least one drive roller. This simplifies the control, since the speed to be set can be corrected or adjusted by the corresponding speed parameter. The result is therefore if necessary a target speed dependent upon the speed parameter for the processing tool, which can be suitably set or specified.
Alternatively or additionally, it is preferred if the at least one processing tool is motorised. In this way the speed of movement of the processing tool can be set quite accurately and reliably. Here it is also preferred, if the processing tool rotates about an axis. This is a simple movement that can be maintained easily with more or less constant speed. In addition, the regulation of the position of the processing tool is then quite possible. This applies in particular in the event that the axis is aligned parallel to the material web and perpendicularly to the transport direction of the material web in each case in the area of the processing device or the processing tool. Thus, the speed of rotation of the processing tool can be easily adjusted to the path velocity. Here, the rotation can take place both in the direction of movement of the material web and counter to this direction. In order to be able to easily provide rotating processing tools, these can be formed of or supported by a processing roller.
Irrespective of the drive and the type of movement of the processing tool, the processing position of the at least one processing tool can also be regulated at least by a brief, in particular pulsed, acceleration and/or deceleration of the speed of the processing tool. This allows the position of the at least one processing tool to be easily adapted to the sections to be processed of the material web. This applies in particular to rotating processing tools and also in particular to those with an axis of rotation, aligned parallel to the material web and perpendicularly to the path velocity in each case in the area of the processing device or of the processing tool.
Alternatively or additionally, for stable and rapid regulation it is expedient if the processing position of the at least one processing tool is regulated by means of a control loop through brief acceleration or braking or deceleration of the at least one processing tool moving with a predetermined speed. Irrespective of this, if necessary the predetermined speed of the at least one processing tool can be increased or reduced via a pilot control. This pilot control can be performed easily and with sufficient accuracy.
Particularly expediently, the method can be used if the at least one processing tool involves a cutting tool, a perforation tool, an embossing tool, a stamping tool, a folding tool and/or a printing tool. These processing tools must constantly work with very high accuracy and are also generally open to very rapid regulation.
The method is also particularly effective when using material webs in the form of packaging material webs, preferably made from a packaging material laminate, in particular a cardboard/plastic packaging material laminate. Such material webs cannot be satisfactorily processed with the known methods.
Alternatively or additionally, the present invention can be correlated to register marks, integrated into or provided alongside a decoration. If necessary, however, print marks, embossings, folds, punchings and/or material differences may be considered. In this way subsequent processings of the material web can be matched to previous processings of the material web. With embossings and folds, by way of example, indentations or elevations in the material can be formed, which can be captured by a sensor. If parts of the material web are punched out, edges result which similarly can be captured by a sensor. Parts of the material web may possibly be stamped out in order to make it easy to insert drinking straws, attach spouts or to open packages.
In order that marks other than the register marks to be captured by the at least one sensor are not inadvertently captured, what is known as a door control can be used. In so doing, a release device is used which opens time-related and/or length-related windows, by way of example correlated to the measurement system of the material web, in which the capture of the register mark is permitted. Only then can a register mark be captured by the at least one sensor or the result of the capture passed to an evaluation device or processed by the latter. The corresponding windows are determined on the basis of the capturing events of the register marks by the at least one sensor. The windows are therefore always open for a certain length of time or a certain length of the material web, in which the next register mark is expected. Since the distance between the register marks is known at least approximately, on the basis of the capture of the last register mark and if necessary also the speed of the material web it can be estimated more or less when the next register mark is to be captured. Around the expected next register mark, a further window, in particular of a predetermined width is opened by the release device.
To allow correlation of the capturing events precisely to the measurement system of the drive roller, it is appropriate if the corresponding roller comprises a roller sensor for capturing a parameter dependent upon the measurement system of the at least one roller, in particular an angle, an angular difference of a circumferential length and/or a circumferential difference. So that alternatively or additionally the position of the processing tool can be captured precisely, the processing tool and/or the processing roller can be associated with a position sensor, which by way of example captures the position of the processing tool or the angle of the processing roller.
In the following the invention is explained in more detail by means of a single exemplary embodiment.
The drawing shows as follows:
Here the material web 2 is transported to the right and in so doing is guided past a sensor 7 which, in the device 1 shown and in this respect preferred involves an optical sensor 7. If necessary, however, other sensors and/or further sensors can be provided for. The sensor 7 is provided in such a way that it recognises register marks 8 provided on the material web 2 in the form of print marks, when these pass the sensor 7. Once the material web 2 has passed the sensor 7, the material web 2 reaches a processing device 9 with a processing tool 10. The device 1 shown and in this respect preferred, is a processing device 9 for dividing the material web 2 into individual blanks, which can be used as packaging material blanks for the formation of packages, in particular for filling with foodstuffs. For cutting the blanks from the material web 2, the processing device 9 has a processing tool 10 in the form of a processing roller with two cutting blades 11. The processing roller rotates in the transport direction T of the material web 2 so that the cutting blades 11 are guided past a fixed cutting edge 12 provided on the other side of the material web 2 and in so doing sever or cut the material web 2 transversally to the transport direction T. The processing tool 10 is driven by a drive 13, configured here as an electromotive drive.
Alternatively or additionally, however, other processing tools can be provided which, by way of example, print, perforate, emboss, fold or stamp the material web 2. In addition, instead of print marks, fold lines, punchings, perforations, material differences or other features of the material web 2 can be used as register marks 8. Here, if necessary, it may also be expedient to use a sensor other than an optical sensor 7.
The drive roller 3 and the processing tool 10 are associated with a roller sensor 14 and a position sensor 15, which capture the position of the associated rollers 3,10 and pass on this position in the form of a signal S to an evaluation device 16. Similarly, the sensor 7 capturing the register marks transmits a signal S to the evaluation device 16, when a register mark 8 passes the sensor 7. Thus, the evaluation device 16 can compare the processing position of the processing tool 10 upon capturing a register mark 8 or the processing position of the processing tool 10 corresponding to a capturing event of a register mark 8 with a predetermined processing position of the processing tool 10 for the capturing event. If in the process a deviation between the actual and the predetermined processing position is established, by means of a regulating device 17 a regulating intervention takes place, which influences the drive 13 of the processing device 9 in such a way that the corresponding deviation of the processing positions is reduced or as far as possible eliminated. In the method shown, and in this respect preferred, this takes place by a brief or pulsed acceleration or deceleration in the speed of the processing tool 10.
On the basis of the successive capturing events of register marks 8 by the at least one sensor 7, the evaluation device 16 can determine a speed parameter, dependent upon the path velocity of the material web 2 in the region of the at least one sensor 7. The evaluation device 16 correlates the path velocity to the measurement system of the drive roller 3, in that the angle, through which the drive roller 3 continues to rotate between two capturing events, is correlated to the capturing events. Thus, it can be determined if the expected distance between the register marks 8 with regard to time and/or length of the material web 2 corresponds with the actually determined distance between the register marks 8 similarly with regard to time and/or length of the material web 2. If this is not the case because, by way of example, the register marks 8 do not have the predetermined distances between them, slip during transport of the material web 2, or stretching of the material web 2 occurs, via a control device 18 the speed of the processing tool 10 can be adapted accordingly. In addition, separately from this a regulation of the processing position of the processing tool 10 takes place. Both the regulation and the control generate manipulated variables U which, if necessary by superimposing, have an effect on the drive 13 of the processing roller 10 of the processing device 9.
In
If now a deviation between the predetermined processing position of the processing tool 10 and the actual processing position of the processing tool 10 occurs for a capturing event of a register mark 8 by the sensor 7, the comparator unit D1, in which the information E of the capturing event and information P of the position of the processing tool converge, transmits a signal S dependent upon the amount and sign of the deviation to a position regulation device PR, which adds a corresponding manipulated variable U to the manipulated variable U leaving the regulator R. If, alternatively or additionally, the effective path velocity determined on the basis of the capturing events of the register marks 8 by the sensor 7 does not correspond to the path velocity that would be expected on the basis of the speed of the drive roller 3, the comparator unit D2, in which the information E of the capturing event and information L of the measurement system of the drive roller 3 depending on the amount and sign of the corresponding deviation, provides a signal S to a calculation unit B, which on the basis of the corresponding signal S calculates a correction speed, which is then passed as a reference variable W to a correction speed regulation device KR, which for its part outputs a manipulated variable U, to which the manipulated variable U is added, which has already been determined beforehand.
A door control T receives information E of the capturing events and on the basis of this and if necessary additionally on the basis of a path velocity parameter, determines a window according to time and/or material web position, in which the next capturing event can be expected, and passes on the information concerning the window as door control information TS to the sensor 7. Outside of this window, no capturing takes place or the respective capturing event is not further processed in the manner described.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 122 430.5 | Dec 2015 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/077696 | 11/15/2016 | WO | 00 |
