Patent Application
20110226434
The present invention relates to a method for guiding web patching, using a re-reeler, in connection with a paper machine and an off-line coating machine, in which method a defect map of the web is created on the paper machine, to show deviations to the operator, the said deviations being patched using the re-reeler, guided by the defect map and preset patching rules. The invention also relates to a corresponding system, in connection with a paper machine, re-reeler, and off-line coating machine. By way of an analogy, it is possible to speak of an increase in the efficiency of the coating machine, because the patching of the web is the most significant factor in it.
Systems are known from the prior art for monitoring deviations in a web being coated, on an off-line coating machine. In these systems, a defect map of the web is created, based on defect detection that has taken place on the fibre-web machine, which is then displayed to the operators of the off-line coating machine. More specifically, the defect map created on the basis of defect detection taking place on the fibre-web machine prior to reeling is synchronized for the coating machine, where is it displayed to the operators. The defect maps can be further transferred to other subsequent process stages. In addition to this, the post-coating quality can be monitored by imaging the coating web and displaying the deviations found as a defect map. On the basis of these two defect maps, the quality of the web arriving at coating can be seen, as can the quality of the web leaving coating. The defect map, which is imaged after coating, is typically shown in the same display as the defect map that has been imaged prior to coating. By showing the defect maps on the same display, the operator can easily see how the original deviations have changed during coating, provided the web does not break during coating. A method and apparatus for monitoring a rapidly moving web, in which event chains are detected from the web by means of real-time image analyses and displayed in essentially real time, are known from PCT publication WO 2007/096475 A 1.
In the apparatuses according to the prior art, the paper machine, re-reeler, and coating machine are independent units, between which information on deviations causing web breaks on the coating machine is transferred poorly. The poor transfer of information between the units considerably hinders the investigation of the cause-effect relationships of the deviations causing web breaks.
The invention is intended to create a new type of method and system for guiding patching using a re-reeler, in connection with a paper machine and an off-line coating machine. The method permits better investigation of the cause-effect relationship, particularly in break situations. The characteristic features of the present invention are stated in the accompanying Claims. The invention is also intended to create a system for monitoring defects of a web being coating using an off-line coating machine. By means of the system according to the invention, the preceding processes can be provided with better feedback than previously. In the system according to the invention, the movement of a deviation detected in the previous process stages is monitored with the aid of virtual monitoring, which takes place by monitoring in real time the location, at the coating machine, of a point depicting the deviation on the machine screen, on the basis of an animated web map of the coating machine. The web map shows the horizontal dimensions of the coating machine web, the critical points on the coating machine, and a point showing each deviation to be monitored. The critical points on the coating machine are, for instance, the coating machine's coating stations. On the other hand, it is good to indicate the defect-detection cameras on the machine screen. The location of a point depicting a deviation, in virtual monitoring, using an animated web map, relates correctly, in terms of speed and location, to the actual location of the deviation on the coating machine (web speed). In virtual monitoring, the location of the animated point depicting a deviation on the animated web map is calculated on the basis of the real location information and the web speed of the coating machine. With the aid of virtual monitoring, it is possible to decide the location of a deviation causing a web break, relative to the critical points on the coating machine and to return the corresponding images taken by the cameras to be displayed to the operator.
In one embodiment, the system includes means for monitoring the web at the coating section and for finding deviations in the web using selected criteria, the analysis means for connecting each deviation with a deviation shown in the defect map by selected criteria or ascertaining it to be a new deviation, and display means for showing selected deviations in at least one selected position. In one preferred embodiment, the two and three most significant deviations are monitored virtually through the entire coating machine by showing animated images of them automatically on the machine screen. Monitoring of the web considerably facilitates the investigation of the cause-effect relations of web breaks.
In addition, the invention is intended to create an off-line coating machine, in which there is a system for monitoring deviations in the web being coated. By means of the off-line coating machine according to the invention, breaks can be avoided better than previously.
Here, the term web refers to board or paper webs. For its part, the term fibre-web machine, which precedes the off-line coating machine, refers to web-forming machines that manufacture board or paper. An off-line coating machine includes an unwinder, a coating section, and a winder. The coating section includes a drying section. Before the coating section, a defect map of the web being coated is formed, in order to show deviations. The defect map to be shown is created on the basis of defect detection taking place on the fibre-web machine, or by imaging the web after unwinding before the coating section. The types of deviations that enter the coating section are seen from the relevant defect map. In addition, at the coating section the web is monitored automatically, when web deviations are detected using selected criteria. The automatic monitoring can take place using machine vision or some other imaging system. The visualization of the formation of each deviation increases the possibility of preventing breaks and deviations, thus increasing the machine's efficiency.
A set of machine-direction co-ordinates of the web is attached at the paper machine to the edge of the web with colour-coded marks. A tachometer measures the length of the area between the codes. Each deviation detected is connected by means of selected criteria to a deviation shown in the defect map, or is ascertained to be a new deviation. A selected deviation that is detected automatically during monitoring is shown to the operator from a selected position in the coating section. When the detected deviation is connected with a deviation shown in the defect map using the selected criteria, or is ascertained to be a new deviation, the deviation can be monitored through the entire process after they have been found. When deviations are followed through the process, it is possible to see what kinds of deviation cause problems. Monitoring also makes it possible to see what deviations, which appear harmless before coating, cause problems during coating. The problems appear either as a worsening of the deviations, or even as breaks.
In one preferred embodiment, a high-speed camera reads the location of the colour code and the edge of the web. Immediately after the first colour code is read by the colour-code reader, a virtual position calculation can be created on the basis of the colour code and the tachometer reading. Web breaks can also be detected with the aid of the high-speed camera.
In one embodiment, selected deviations are shown in real time. When displaying deviations in real time, they are shown as quickly as possible, preferably within one second. Displaying the images in real time to the operator gives the operator more time to react to events and, for example, to prevent a break. When implementing the display of images in real time, the images are analysed at least at the imaging frequency after they are taken, i.e. the images are not stored in a cache memory, but are analysed immediately.
On the basis of the monitoring taking place in the coating section, feedback is preferably provided for the process stages preceding the coating machine by updating the deviations causing web breaks on the coating machine into the patching rules. The information obtained when monitoring the coating section allows feedback to be sent to those working on the re-reeler and the fibre-web machine. At its simplest, feedback can be taken care of by making a telephone call to someone working in the previous process stage, who can, on the basis of the feedback, examine the defect map to reduce the described deviations. Generally, the patching rules of the re-reeler are a computer application, which uses selected criteria to select deviations from the defect map. Naturally, all deviations cannot be patched, only those that meet the preset criteria for the patching rules. The criterion for a defect to be patched is usually a specific boundary size, but the type of deviation will also affect the matter. The feedback is preferably entered in the system, i.e. new criteria are defined in the system for patching rules for the computer application, by means of which it classifies the deviations. Updates to the patching rules in the computer application are preferably made directly on the coating machine. Those working on the fibre-web machine can see the point of origin of a deviation interfering with coating and take steps to eliminate it. Feedback is preferably given to those working on the re-reeler, as those working on the re-reeler can remove deviations interfering with coating, which appear in the base web, which is typically referred to as the base paper.
Thus, feedback makes it possible to deal with precisely the right deviations, as, for example, there is no need to react to all deviations that appear as light-coloured streaks by removing them. When those working at the re-reeler receive accurate information as to what kinds of deviations worsen during coating, or even cause breaks, deviations that will probably cause problems during coating can be removed. Thanks to the information that is more accurate than in the prior art, it is also possible to partly avoid the unnecessary patching of some deviations that will not cause web breaks. Because using the method according to the invention provides a new type of information on the coating process, information can be given to the preceding processes on deviations that have not previously been known to significantly interfere with the coating event.
In a third embodiment, the web is monitored automatically between the unwinder and the coating section. Information is then obtained on defects that have arisen after re-reeling. As the deviations in the web are known more accurately, the behaviour of the web in coating can be forecast better. The cause-effect relations will also be more apparent.
In a fourth embodiment, the defect map formed of the web being manufactured on the fibre-web machine is synchronized for the coating section, on the basis of automatic monitoring between the unwinder and the coating section. Thus, the synchronization is performed more accurately than previously, allowing defects found on the web to be ascertained with greater probability as being due to a defect in the web.
In a fifth embodiment, in which the coating section includes at least one coating station and at least one drying station, machine vision is used to monitor the web at the coating station. When imaging the web at the coating station, breaks caused by deviations will be seen more than when imaging the web elsewhere in the coating section, as typically about 80% of breaks take place at the coating station. If a break is seen immediately when it happens, the break blades can be used considerably more quickly than before, which, for its part, will facilitate getting the machine quickly back into operating condition. In other words, by seeing a break as soon as possible, the break blades can be used quickly, thus reducing tangling in the coating machine. As the coating machine becomes entangled less frequently and less seriously than previously, less time than previously need be used for maintenance and washing.
In a sixth embodiment, the automatic monitoring takes place using machine vision. Machine vision includes imaging using cameras, while examination of the images takes place mechanically using a computer, i.e. automatically. Using machine vision, information on the web is obtained, on the basis of which many different kinds of analysis can be performed, in order to connect deviations. Machine vision allows the operator to be shown an image of the defect.
More specifically, the invention is characterized by the virtual location of deviations selected on the coating machine to be monitored through the coating machine, and in the event of a possible web break for the deviation to be localized relative to the web break, and on the basis of this monitoring feedback is given to the patching rules of the re-reeler, in order to optimize them.
In the following, the invention is examined in detail with reference to the accompanying drawings showing some applications of the invention, in which
a shows a system according to the prior art, on a re-reeler and off-line coating machine,
b shows a system according to the invention, on the paper machine of
a shows a system 10′ according to the prior art, in which first of all a web is manufactured on a paper machine 12. The manufactured web is re-reeled, cut to a standard width, and patched on the re-reeler 14, after which the web in question is coated on an off-line coating machine 16. The coating machine 16 is roughly divided into three parts, i.e. unwinding 18, the coating section 20, and winding 22. After the coating machine, coating lumps and streaks are removed from the web on a second re-reeler (not shown). After this, the web can be calendered. It is possible to use the same re-reeler in the removal of coating lumps and streaks after the coating machine as in the re-reeling taking place before the coating machine, but typically a second re-reeler is used for re-reeling after the coating machine.
In the system according to the prior art shown in
A colour-code reader 143 and a tachometer 142, by means of which it is possible to run to the positions of the defect points and perform patching according to the preset patching rules 144, are used at the re-reeler 14. Suitable software is used to filter out from the defect map 31 all defects that have been shown by experience not to cause harm. The reader gives the distance of the next deviation three times a second and the remaining time and distance to the following deviation is displayed to the operator. The rest of the defects are shown to the patcher for repair.
In the system of
However, the system according to the prior art does not provide information as to the stage at which problems appear in the coating section. The typical length of the web circulating through the coating section is several hundred metres, for example 300 m. If break occurs, it can typically be seen from the defect map that there are several deviations in the coating section that could have caused the break. Using imaging that takes place before coating, it cannot be decided with certainty which of the deviations possibly caused the web break. In such a case, imaging after coating provides no information on the break. Typically, the operator guesses that the break has been caused by the largest deviation visible in the defect map, but in reality some other deviation may have caused the break and thus be considerably more significant. In addition, the break may be caused by a deviation that does not even appear in the defect map.
In the system 10′ according to the prior art shown in
b shows a system 10 according to the invention, improved from the system 10′ of
In this case, in order to maintain and optimize the patching rules the coating machine is equipped with a code reader 183 and a tachometer 182, by means of which each deviation in the defect map 31 can be located quite precisely (±50 cm). The system includes display means 52, in which it is possible to follow the location of each defect P through the coating machine (machine screen 56). When the deviation P travels in the image from the top down, and a possible break occurs precisely at the location of the deviation at that moment, it can be concluded that such a deviation P is critical and it can be classified to be patched in the patching rules. Correspondingly, a correction can be made in the running parameters of the paper machine, if the correction should be made already on the paper machine. Each deviation that is classified to be monitored is monitored through the entire coating machine. In
The coating machine 16 preferably has its own machine-vision system, so that additional information in support of a conclusion as to whether the defect is significant can be attached to each defect. Such an own machine-vision system is useful, because a specific type of defect does not cause a break immediately, but only once it accumulates, for example only 50 m later. An own machine-vision system reveals such cases, when the defect location, for example a roll, can be monitored stage by stage. A considerable dispersion relates to the behaviour of defects, so that there is reason to monitor more closely certain types of deviation, such as thinnings, detached fibre threads, and glue accumulations. The coating machine's own machine-vision application also permits the examination of ‘near-miss’ situations. This is because deviations appear now and then on the coating machine, which are clearly close to causing a web break, but the web is able to the wound before the web break occurs. Such deviations can be avoided with the aid of feedback, i.e. the patching rules are examined correspondingly.
By using the system according to the invention on an off-line coating section, information is obtained on deviations that worsen at the coating section. All the information obtained from a worsening deviation is displayed to the operator and recorded. This allows worsening deviations to be reacted to when they are already in the coating section. Information on the worsening of deviations permits, for example, the break blades to be used before a break is caused. In systems according to the prior art, for their part, information is not obtained on deviations that worsen in the coating section without causing a break when they are in the coating section. Information on the worsening of deviations is obtained only once the deviation has gone through the entire coating section, when a new defect map is imaged. However, many deviations worsen first at one coating station and break only at the following one. When using an off-line coating section according to the prior art, there is no possibility to react to a worsening deviation, as information about it is not obtained.
The analysis means 35 belonging to the system according to the invention, shown in
The system 10 according to the invention, shown in
The system 10 according to the invention, shown in
The system 10 shown in
The coating section according to the invention, shown in
The break-monitoring means 44 belonging to the coating machine according to the invention, shown in
Information from the coating section is shown in the left-hand side 52 of the user interface. Thus, information that has not previously been displayed is displayed in the left-hand side. In the upper right-hand corner of the left-hand side 52 is a machine screen 56, from which the operator sees the configuration of the coating unit, as well as at which positions the cameras are. When the deviation moves out of the defect map 31, i.e. when the deviation moves to the coating section, the deviation is monitored from the machine screen 56 on the coating section with the aid of virtual monitoring. The deviation can be seen on the coating machine shown on the machine screen 56. When the deviation has gone through the coating section the deviation is shown in the defect map 48. Deviations that have been found only in the coating section can also be seen in the machine screen. Two of the most significant deviations in the coating section, i.e. which appear in the machine screen 56, are monitored virtually through the entire coating section, by displaying animated images of them automatically in the screens 58 and 60, in each imaging position in which the deviations are detected. In other words, the two or three most significant deviations P are monitored virtually through the entire coating machine 16, by displaying animated images of them automatically at each moment relative to the coating machine. The deviations shown in the screens 58 and 60 can be viewed afterwards from the screen 54 in the right-hand side 50 of the user interface. In addition, all of the information collected on the deviation in question can be read in the right-hand half of the user interface. Statistical data on the deviations detected in the coating section are displayed in the screens 62 and 64.
The deviations that meet the selected criteria obtained from the register are shown at the initial point of the animation, which refers to the start of the coating machine. The location of a deviation through the coating machine is monitored in animation from the machine screen 56 while animated images of the deviations are shown at the imaging positions.
The method and corresponding system according to the invention combine web monitoring and web-break analysis in a single totality. All process disturbances causing deviations or web breaks are recorded and displayed automatically. By means of the method and system according to the invention in their totality, an increase of as much as 13% in overall efficiency can be achieved on a process line.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20086127 | Nov 2008 | FI | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FI09/50951 | 11/24/2009 | WO | 00 | 5/25/2011 |
