EP1057907A1

EP1057907A1 - Spinning mill processing control systems and methods

Info

Publication number: EP1057907A1
Application number: EP99201725A
Authority: EP
Inventors: Rüdiger Zeitler
Original assignee: Barco NV
Current assignee: Barco NV
Priority date: 1999-05-31
Filing date: 1999-05-31
Publication date: 2000-12-06

Abstract

Control systems and methods are described which are particularly suitable for spinning mills. In particular the control methods and systems are designed to regulate and control foreign fibers and materials which may be found during the spinning process.

To reduce the number of foreign fiber detectors some machines (8) may be provided without a detector. Bad quality or very good quality material may be sent to such a machine. Intermediate quality product may be sent to machines (2, 4, 6, 10) with foreign fibre detectors (12, 14, 16, 20).

The control systems and methods also foresee both upstream and downstream control. This may include changing the settings of detectors on one or more machines )2, 4, 6, 8, 10) to optimize the operation. To assist in this process it is preferred if quality data is stored at each processing machine (2, 4, 6, 8, 10) in a label 17, 19 which may be applied to work-in-progress (15) or may be stored in a centralized computer (31).

Description

The present invention relates to a system and a method for control of a production unit, e.g. a spinning mill, including for example (though not exclusively), bale opener, coarse and fine cleaner, mixer, carding machines, drawing benches, combing machines, flyers, spinning machines, winding machines.

TECHNICAL BACKGROUND

In recent years, quality conscious knitters and weavers have increasingly demanded non-contaminated yarn. Devices are known for detecting foreign materials in many stages of the process of spinning natural fibers such as cotton into yarn. There are certain disadvantages in detecting foreign materials late on in the spinning process. At the yarn stage, foreign material is preferably cut out which may cause loss of considerably lengths of yarn and machine stoppages. Hence, it is preferable to detect foreign materials reliably at an early stage.
There are several foreign fiber detectors available for the various machines in a spinning mill. However, these detectors have mainly been used individually to control each machine. Equipping each machine, e.g. each spindle, with a foreign fiber detector is a considerable financial outlay. Further, due to the way contamination is fibrillated by the spinning mill processing machines, foreign fibers from a badly contaminated bale can become distributed throughout the work in progress. This can seriously impair the operation of a spinning mill. On the other hand, running the machines with foreign fiber detectors set to high sensitivities in order to catch the occasional bad batch can result in many machine stops and false alarms and therefore low efficiencies. Tight control of foreign fiber content is in principle useful as it assists in improving quality but excessive machine stops may cause operators to ignore alarms and reduce efficiency.
An object of the present invention is to provide a quality control system and method which improves the efficiency of a spinning mill.
Another object of the present invention is to provide a quality control system and method to obtain maximum production for a given minimum level of contamination.

SUMMARY OF THE INVENTION

The present invention includes a quality control system for a production unit comprising a plurality of different processing machines which carry out processing on intermediate product and which operate sequentially and optionally in parallel; comprising:
a first sensor monitoring at least a first quality parameter of a first intermediate product in a first processing machine;
a second sensor monitoring at least a second quality parameter of a second intermediate product in a second processing machine;
a first device for recording the values of the first quality parameter output by the first sensor; and
a second device for altering the setting of the second sensor in response to the recorded quality values from the first sensor. The first and second quality parameters may be the same parameter. The setting of the second sensor may be a sensitivity level. The quality parameter may be related to the presence or intensity of unwanted foreign materials in the intermediate product. The system may relate to a spinning mill. For example, the quality parameter may be the presence of foreign fiber in a sliver, roving, web or yarn in a spinning mill. The second device may alter the setting of the sensor on the second machine only when the intermediate product processed by the first machine reaches the second machine. Alternatively, the second device may alter the setting of the sensor on the second machine independently of when the intermediate product is being processed. The means for recording may be distributed throughout the system, for example, may be attached or physically associated with the intermediate product after processing, or may be centralized for all machines, or may be compartmentalized, that is centralized for a sub-set of the machines. For example, in a spinning mill, each can containing sliver may be provided with a memory tag, e.g. a bar-code or a remote readable memory card on which the quality information is stored. Alternatively, the recording means may be centralized, e.g. a centralized computer system, in which the quality data may be stored by electronic means. The second device may be hand operated at each machine, e.g. a can with an attached memory device is loaded onto the second machine. The memory tag is read by a reader and a display device on the second machine outputs data for the operator which allows him or her to adjust the sensor on the second machine. Alternatively, the adjustment may be made automatically, e.g. controlled by a distributed or centralized computer system linked to the necessary actuators on the relevant processing machines.
The present invention includes a method of a controlling quality in a production unit comprising a plurality of different processing machines which carry out processing on an intermediate product and which operate sequentially and optionally in parallel; the method comprising the steps of:
a first monitoring step for monitoring a first quality parameter of an intermediate product being processed in a first processing machine;
a second monitoring step for monitoring a second quality parameter of a second intermediate product being processed in a second processing machine;
recording the values of the first quality parameter output by the first monitoring step; and altering at least one monitoring parameter of the second monitoring step in response to the recorded quality values from the first quality step. The monitoring parameter may be the sensitivity of detection. The first and second parameter may be the same parameter, e.g. the presence of foreign fiber in a sliver, roving, web or yarn in a spinning mill.
In the above system and method the second machine may lie downstream or upstream of the first machine in a sequential processing line. The system and method may apply to a spinning mill. The processing machines may include, but are not limited thereto, a bale opener, a mixer, a cleaner, a carding machine or any other machine in the opening line, a draw frame, a flyer, a ring spinning machine, an open end spinning machine, a winder, etc.
The present invention includes a quality control system for a production unit; comprising:
a first sensor monitoring quality of an intermediate product in a first processing machine carrying out a first processing step;
a second machine for carrying out a second processing step on an output of the first machine, the second machine having a quality control device for a quality parameter; a third machine also for carrying out the second processing step on an output of the first machine, the third machine not having a quality control device for the quality parameter;
a first device for recording the quality values output by the first sensor; and a selector for selecting one of the second and third machines for processing the output of the first machine, the selection being based on the recorded values from the first sensor.
The present invention includes a method of a controlling quality in a production unit, the production unit comprising a first processing machine for carrying out a first processing step on an intermediate product, a second processing machine for carrying out a second processing step on an output from the first machine, the second machine having a quality control device for a quality parameter, and a third processing machine also for carrying out the second processing step on an output of the first machine, the third processing machine not having a control device for the qulaity parameter, the method comprising the steps of: monitoring the quality of the intermediate product in the first processing machine; recording the quality values output by the monitoring step on the first machine; and selecting one of the second and third machines for processing the output of the first machine based on the recorded quality values for that intermediate product.
The production unit may be a spinning mill. If the quality data from the first machine are good (acceptable) the selection may be of the third machine. The decision to select one of the second and third machines may also be based on other data obtained before processing in the first machine. For example, a "bad history" may be taken into account so that although the results of the quality measurements in the first machine are very good, the second machine is selected as poor results are still feared because of the bad history.
The present invention may include a method for controlling a spinning mill comprising a plurality of different processing machines which carry out fiber processing on fiber product and which operate sequentially or in parallel, the fiber processing producing different fiber structures at the exit of different machines; comprising the steps of:
detecting foreign fibers or material at at least one of the processing machines; and processing the results of the detecting step to optimize the operation of at least some of the other processing machines.
The present invention also includes a control system for controlling a spinning mill comprising a plurality of different processing machines which carry out fiber processing on fiber product and which operate sequentially or in parallel, the fiber processing producing different fiber structures at the exit of different machines; comprising: a detector of foreign fibers on at least one of the processing machines; a processor for processing the results of the detecting step and to optimize the operation of at least some of the other processing machines. The optimization may include downstream control modifications, e.g. selection of certain of the processing machines in preference to other machines. The optimization may include selecting processing machines with foreign fiber detectors or selecting those without such detectors. The optimization may also include upstream control modifications, e.g. changing the settings of foreign fiber detectors on earlier machines, or removing some bad material from production. The optimization may include one or more of the following decisions as well as the relevant action derived therefrom:

a decision to remove the contaminant at the actual machine where it has been detected,
a decision to record (label) the contaminant including the exact position of the contaminant and tracing the course of the material, e.g. as it is moved by a transport device to other machines,
a decision to change the settings of a subsequent machine in order to detect and remove the contaminant safely,
a decision to change the settings of a quality control device in a later machine from low sensitivity to high sensitivity or vice versa, for example only for the appropriate moment when the contaminant is expected to arrive in the subsequent machine,
a decision to determine a statistical value of number of contaminants (e.g. contamination index = number of contaminants/100km) and to change the working point of at least some of the machines in order to minimize this index with or without the same production level,
a decision to select material dependent on the contamination index (with labeling and/or alarm setting)
a decision to trace contaminant back to cotton bales in order to remove individual bales,
a decision to change parameters at a previous machine in order to minimize contaminants at the actual machine,
a decision to trace the whole material flow in order to trace a contaminant in a textile web back to its origin,

Any of the above decisions and/or actions may be made dependent on at least one of the following criteria:

Optimization of material flow. The stop of a machine at the begin of the production line or in the middle may be made dependent on the buffered material between machines.
Predicting material bottlenecks in order to decide whether an individual machine can be stopped.
Maximization of last machine efficiency.
Using feedback from quality control results on the final woven web and changing parameters in order to reduce number of contaminants (e.g. accepting some loss of efficiency to improve the quality).
Analyzing the results of simulating the effect of changing parameters. The control system may be configured as a self-learning system which may optionally have self-organizing and/or self-teaching abilities in order to find the best strategy.

The dependent claims define individual embodiments of the present invention. The present invention will now be described with reference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic layout of a spinning mill with an automatic transport system in accordance with an embodiment of the present invention.
Fig.2 is a schematic layout of a spinning mill with centralized computer system in accordance with an embodiment of the present invention.
Fig. 3 is a schematic layout of a spinning mill with an automatic transport system and a centralized computer system in accordance with an embodiment of the present invention.
Fig. 4 is a block diagram of a global control system in accordance with another embodiment of the present invention.
Fig. 5 is a flow diagram of a downstream machine selection process in accordance with an embodiment of the present invention.
Fig. 6 is a flow diagram of a control system in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

The present invention will be described with reference to certain figures and embodiments but the present invention is not limited thereto but only by the claims. The present invention will be described mainly with respect to spinning mills but the present invention is not limited thereto but only by the claims. Reference will mainly be made to quality as it refers to foreign fiber content but the present invention is not limited thereto. Other parameters of work in progress (intermediate product) may also be used in the control system and method in accordance with the present invention, for example, the yarn or sliver count, the length of discrete pieces such as the length of sliver in a can, the humidity or color of the material, etc.
In the following a summary of foreign fiber detection in an open end spinning mill is given. The skilled person may easily apply this teaching to ring spinning mills with appropriate processing machines.

Bale opener

In the opening room, the bales are put together in a more or less random manner. The bale openers pick raw cotton flocs from their surface. This is the first position in the spinning mill where a detection and removal of the contaminants has been considered. if the system detects a contaminant the bale opener is stopped and an alarm sounded. Somebody has to inspect and remove the contaminant and start the bale opener again. This process does not influence the material flow as long as the time is short enough otherwise the cards may run out of material. To prevent the cards running out of material it is necessary to ignore the alarms sometimes. Usually, the bale opener is allowed unhindered to pick up the contaminants and feed them, together with the good quality cotton, towards the various stages of opening and blending.

Blowroom

The blowroom itself is quite capable of separating certain contaminants, for example especially small sized foreign matter will be separated. Larger contaminants are more likely to remain in the system all the way to the card where they are almost completely fragmented.

Opening line

Contaminant detection is known between the bale opener and the card entry. The performance of these known systems can be tuned to some extent by the appropriate selection of their position along the material flow. The closer to the bale opener, the larger the tufts and the more diverse their color. This means that limits have to be set less critically in order to avoid false rejects. Furthermore, contaminants can hide inside or between cotton tufts thereby decreasing detection efficacy. Finally, the closer to the bale opener the higher the material loss per eject.
There are advantages in applying the foreign fiber detection somewhat further downstream, where the tufts are only wrist-large and their color is more uniform. Unfortunately, not only the tufts but also the contaminants are affected by the aggressive opening, cleaning and blending processes down this production line. This causes the contaminants to get smaller, torn into smaller pieces that may escape any detection and end up in the yarn.
Contaminant is usually removed by a clap or pneumatic injection valve. Foreign material sitting in cotton clusters cannot be detected. As the system also removes good material (due to the removing system and/or false detection) a high efficiency correlates with high loss. Typical values are 80% efficiency with moderate loses.

Card fleece and card exit

At the card, the contagious nature of the foreign fiber contamination becomes apparent. Any tiny cloth of contaminating matter that succeeds in reaching the card entrance will be shred into individual fibers and spread out lengthwise in the fleece. Detection of these "stripes" of foreign matter in the card fleece has been considered but the automatic removal of these contaminants is however hardly feasible, and would certainly bring about a count deviation in the sliver. An interruption of the carding process will reduce efficiency of the card itself as well as, due to the sliver breakage, at the subsequent first drawing passage.
Whatever the position of the streak of foreign fibers in the fleece, after considering into a sliver this streak will show up at the sliver circumference or at a shallow depth below its surface. An alternative to detection at the card fleece is detection at the card exit. There is a disadvantage in having to stop the card (and hence of the first drawing passage as well).

First passage draw frame entry

The visibility of defects does not change between the card exit and the entry of the first passage draw frames. The same way this sliver is laid in the card can (but in the opposite direction), it will be presented at the draw frame entry. Since a stop at the card will cause a stop at the draw frame anyway, foreign fiber contamination may be defected at the draw frame entry. Upon detection of a foreign fiber at the draw frame entry, the draw frame must be halted, and the contaminated piece of sliver removed by hand.
During carding, the foreign fibers exit the card not as a uniform stripe but rather as a "comet": a rather pronounced first part (the head) followed by the "tail", which can, as extend over several meters. On the draw frame entry, first passage, the tail enters first. This imposes strong stability demands on any detection system installed there, as well as high sensitivity requirements since the tail must be recognized typically within one meter in order to allow timely stoppage.
Individual fibers are usually not allowed to invoke draw frame stops. First of all their number can be so excessive that draw frame efficiency would drop to unacceptable values. Furthermore most of these individual fibers will pass undetected anyway.
Further downstream the drawing line, foreign fibers get so diluted that in the end their presence can hardly be noticed anymore. The possibility of detecting foreign fibers originating from shredded cloths diminishes downstream of the drawing line. The streaks are strongly diluted and get embedded in the middle of the sliver.

Open end spinning frame

Finally the sliver is fed into the breaker of the open-end spinning frame. The yarn is finally formed and usually cannot be contaminated further down the processing line. Each rotor may be provided with a foreign fiber detector guaranteeing the quality of this intermediate product. This detector detects and evaluates each foreign fiber. The contaminant is removed automatically by stopping the machine, removing the contaminant, splicing the yarn together and starting the machine again. But the quality of the yarn is influenced (e.g. strength). As this is the last machine in s spinning mill this influence directly the output of the spinning mill thus the number of cuts should be kept to a minimum. Systems at other positions in the spinning mill do not influence the output as long as enough e.g. containers are available (buffer-function). The inspection also represents an end inspection of the material.
At this stage, one can discriminate between two types of foreign fibers. The one type is the individual foreign fibers. The other type is referred to as swarm, cluster or flock. These are the offspring of the rag that has survived the journey from raw cotton bale to open-en breaker without being detected.

Individual foreign fibers

The most common causes of individual foreign fibers are feathers, jute (which is often claimed to be acceptable) and human or animal hairs. Another origin of such fibers has already been mentioned: the pieces of yarn torn loose from rags during shredding. These end up more or less as a whole in the spun yarn and are almost always unacceptable.

Swarms

The detection of a swarm or cluster of foreign fibers is an even more demanding task for a foreign fiber detector on the open-end frame. The original rag has been fibrillated by the card and is now fed as an extremely dilute streak of tiny foreign fibers distributed along several tens, even hundreds of meters.

Swarm detection

In a typical spinning mill, foreign fiber detection systems installed in the blowroom are capable of handling somewhere between 650 and 1200 kg/hour. Operating after the first opener, with an average 800 kg/hour flow rate, typically 50 rejects per 24 hours can be expected for a rather high quality lot of raw material. Material loss per ejection ranges between 10 and 30 g. Out of the 50, about 40 rejects are legitimate.
Experiments indicate that this corresponds roughly with 80-90% of the contaminants. The remaining 10-20 % are either hidden in or between cotton tufts, or are too small or have too little contrast to allow detection. This remaining 10-20 % inevitably escapes downstream and ends up at the card entrance.
With respect to the present invention it is useful to consider four points:
a) a single uniform quality of yarn is not usually necessary. Several different final levels may be used, such as, for example, two qualities. In the following reference will be made to "high" and "low" qualities. Of course, if only high quality material is produced it can be used for low quality jobs but this may be an expensive alternative. Further, the ratio of high to low quality material required will normally be variable, dependent upon the orders obtained. Processing of low quality material may be made cheaper (less stops on the machines, higher throughput with foreign fiber sensors set to a lower sensitivity, etc.). Therefore, it would be preferable to be able to run the spinning process to obtain an optimum ratio of high to low qualities. Further, it is preferred if the settings on each machine do not have to be changed very often as this causes downtime. Hence, it would be preferable to have relatively stable processing lines. At some point in the process the lower quality material is preferably split off from the higher quality route.
b) The point at which material becomes "low quality" may be undefined or may differ. By undefined its is meant that material which is of a low quality at one stage may be improved in quality at the next stage. Further, material which has a bad history as far as quality is concerned may keep this low quality status despite the quality being good in later machines. Thus, high or low quality is not a final qualification for work in progress. Improving the quality of an intermediate product in subsequent processing steps may require a more costly processing so that improvement may only be an option which is used under certain special circumstances. Thus, it is preferable not to label work in progress simply with a quality grade, e.g. "low" or "high" quality as is done for instance in the system of EP 392 278.
The point at which work in progress becomes low quality may vary. In accordance with the present invention it is preferred if the quality labeling occurs once the work in progress has achieved a relatively well defined form, e.g. as a sliver at the carding stage or during or after drawing, or as yarn after spinning. There are, therefore, various entry points into the low quality processing route. Generally, the flow will be from the high quality line into the low quality line, but as indicated above, the reverse may also be true.
c) The ability to detect and the cost of detection of the same contamination at different machines may be different. For example, at the exit of the carding machine a foreign fiber may be in the form of a "comet" with a dense head and a long tail. When this contamination enters the drawing frame it will do so in the reverse direction, i.e. tail first. A comet is easier to detect at the output of a carding machine. It is much more difficult to detect fast enough to stop and remove all the contaminant in the drawing frame.
d) Action taken at one machine to maintain quality or efficiency may have an effect on later machines, especially their efficiency. Assume a spinning mill with a foreign fiber detection system in the opening line (cotton tufts), a foreign fiber detection system at the exit/condenser of the card (sliver), a foreign fiber detection system at the entrance of the first draw frame (sliver) and a foreign fiber detection system at the open end spinning machine (yarn). In the opening line the contaminants are removed automatically, but with loss of some good material. Not all contaminants can be seen as some are within big tufts. In the card machine only contaminants in the cotton web can be seen at the outer face of the sliver. Stopping the machine is difficult as this results in high efficiency loss. One possibility to remove the contaminant without loosing high efficiency is to force a can doffing and activate an alarm (optical or acoustical). The contaminant can then be removed by a worker. This method produces cans with different sliver length resulting in efficiency loss at the following machine. At the entrance of the drawing frame handling the first passage all contaminants can be found as they were at the exit of the card machine. Stopping the machine is possible without to much efficiency lost as the machine efficiency is typically at 70-80% with relatively high manpower. The contaminant has to be removed by a worker. Typically a contaminant exits the card and of course enters the sensor like a comet with first a clear big, short part and then a long slight tail - this is reversed at the entrance of the draw frame. Detecting the contaminant (with the tail first) as soon as possible requires sensitive settings of the system resulting sometimes in too many false stops. A system at the open end spinning machine requires cutting the yarn and splicing it again. This changes the quality of the yarn (e.g. only 80% of tensile strength with a small knob). Of course a system at this position can detect an individual foreign fiber which is not possible at other positions. The installation of a sensor also represents a final inspection of the produced material. Too many cuts at the spinning machine influence the machine efficiency drastically (typical 80-98%).
Fig. 1 is schematic layout of a spinning mill machine park with which the present invention may be used. The park includes a plurality of different fiber processing machines 2, 4, 6, 8, 10 such as a bale opener, a mixer, a cleaner, a carding machine, a draw bench, a combing machine, a texturing machine, an open end spinning machine, a winder, a flyer, etc. With at least some of the machines 2, 4, 6, 10 a quality control device 12, 14, 16, 20 is provided. With at least one machine 8 no quality control device is provided. The quality control devices 12, 14, 16, 20 may include a foreign fiber detector and optionally a clearer and/or alarm. Intermediate product may be delivered to the machines 2, 4, 6, 8, 10 by an automatic delivery system 21, 23, 25, 27. This has a path 25, 27 through the machine park which may consist of a rail system, or pathways suitable for motorized robots. Intermediate product such as a can, or bobbin 15 may be transported in trays 13. Intermediate product, e.g. cans, bobbins, may be stored in an unloading area 23. Raw product, e.g. cotton bales, and completed product, e.g. bobbins, may be stored in a warehouse 21.
In accordance with one embodiment of the present invention a quality label 17, 19 is associated with an intermediate product (work in progress) which defines some quality characteristics of the product, such as the number and/or position and/or types and/or colors and/or size and/or length of foreign fibers present in fleece, web, a sliver or yarn. Typically, the information which can be stored may be the intensity of the contaminant, its length, its color and its position within the intermediate product (length in meters from the beginning). In addition the level of contamination may be summarized in a contamination index, i.e. a single value calculated from the quality parameters measured in accordance with an appropriate algorithm. The word "label" is meant in its broadest sense and may include remote sensing memory devices in general such as bar-codes or remote readable memory cards, as well as contact reading devices. Where physical labels are used, they are preferably machine readable. For example, the cans may be marked e.g. at the end of processing at the card with a code, including all the information of the contaminants. The information can be recorded as a bar-code or in an electronically read/write device (e.g. small passive chip on the cans with small RAM, which can be accessed by radio frequency devices). The quality information may be alterable in the label. For example, with remote reading memory cards including E²PROM's the stored information may be altered or updated or corrected at a later stage. The label 17, 19 may attached to work in progress 15 or may be attached to a tray 13 carrying the work in progress.
Further, the automatic transport system may also be adapted for directly selecting the intermediate product, e.g. a can, as either good quality and bad quality and influencing its transport to the machines further down the processing line (draw frames and/or OE spinning machines). To do this the automatic transport system may have a reader and processor 11. Processor 11 preferably includes sufficient local intelligence to decide whether an intermediate product is high or low quality. This device 11 reads the label 17, 19 and decides based on the read data whether the intermediate product should be classified as one of a plurality of qualities, e.g. high or low quality. The reader 11 may then update the records for the intermediate product 11 without deleting previous data. The automatic transport system may then decide to move the low quality intermediate product to machines processing low quality product. Such a machine 8 may have no quality control device for foreign fibers (because the quality is not important). Alternatively, the automatic control system may decide that the intermediate product 15 can be improved or that it is reasonably high quality. In this case, the automatic transport system may transport the intermediate product 15 to a machine 2, 4, 6, 10 with a foreign fiber detection system 12, 14, 16, 20. However, if the history data in the label 17, 19 is good, the automatic transport system may decide that, as only a few foreign fibers exist in the intermediate product it can be safely moved to a machine 8 without a foreign fiber detection device. Even if a foreign fiber is present, it may be removed in machine 8 if its position is known accurately. In this case the machine 8 may be stopped at the appropriate length and the foreign material removed. Typically there may be 1 serious foreign fiber for every 10 cans, so that the above arrangement provides no loss of quality and a significant reduction in capital outlay as not all of the machines 2, 4, 6, 8, 10 need to have a foreign fiber detection system. Further, a machine such as 8 when used with high quality intermediate product may be run at full speed as it is known that the quality is good. This may improve efficiency of the spinning mill.
A method of selecting a downstream machine (downstream or feed forward control) is shown schematically in Fig. 5 which will be described with reference to a foreign fiber detector at the exit of a carding machine as an example. In step 61 the label on the can is read including the running contamination index (RCI). The RCI is a weighted average of the contamination indices from previous machines. The RCI therefore gives a measure of the "history" of the intermediate product up to this point. In step 62 the intermediate product (IP) is processed on the machine and the foreign fiber intensity, position, type etc. is recorded onto the label. From these values a current contamination index (CCI) is calculated based on a suitable algorithm. In step 63 the new RC1 is calculated by taking a weighted average of the old RCI and the new CCI, e.g. RC1 = w₁ x RCI + w₂ x CCI, (w₁ + w₂ = 1) and the value stored. In step 64 it is examined if the CCI is above a certain first upper threshold (indicating poor quality). If yes in step 64, it is then examined in step 65 if the RCI is above a second upper threshold (indicating general poor quality). If yes in step 65 the IP is directed to the low quality line, e.g. a machine without a foreign fiber detector and the label is updated to classify the material as low quality. If no in step 65 (indicating general good quality) it may be decided to try and improve the quality so the IP is directed to a machine with a foreign fiber detector and the IP is qualified as of intermediate quality.
If no in step 64 (indicating current good quality) it is determined in step 66 whether the RCI is above the second threshold (indicating general poor quality). If yes in step 66 it is decided that the material may still be of poor quality because of a poor history and the IP is sent to a machine with a foreign fiber detector. If no in step 66 (indicating general good quality) the IP is labeled as good quality and is sent to a machine with no foreign fiber detector.
As an alternative to an automatic centralized intermediate product transport system, the quality of the intermediate product may be first identified at the later machine. To do this a reader and processor 22, 24, 26, 28, 30 may be provided at each machine 2, 4, 6, 8, 10 for reading the label 17, 19 and deciding what should be done based on the data recorded. For intermediate product 15, with high contaminant rates the reader processor on the machine may be adapted to force the relevant machine to stop forcing the operator to change to a new intermediate product or to ask for instructions. Although not shown in Fig. 1 this latter procedure is also suitable for a spinning mill without any automatic transport system. In this case, the intermediate product 15 is delivered to the machines 2, 4, 6, 8, 10 by some other means, e.g. by fork lift truck, and the label 17, 19 is then read by the local reader and processor 22, 24, 26, 28, 30. Further, processing of each intermediate product 15 is controlled by the reader and processor 22, 24, 26, 28, 30 as described above.
Independent of whether an automatic transport system is provided, the reader and processor 22, 24, 26, 30 may also be adapted to write quality data delivered by quality control device 12, 14, 16, 20 to the respective label 17, 19 of any finished intermediate product 15 doffed from the respective machine.
In accordance with an embodiment of the present invention the settings of the foreign fiber detection units 22, 24, 26, 30 at a processing machine 2, 4, 6, 10, e.g. the draw frame, can be adjusted by the reader and processor 22, 24, 26, 30 based on the quality information associated with the intermediate product 15 to be processed. For example, a contaminant exits a carding machine like a comet. On entering the draw frame in reverse direction the settings of the foreign fiber detector at the draw bench must be set to very sensitive to detect the "tail". Knowing the approximate position of the contaminants the settings of the detection system on the drawing frame are adapted for optimally detecting the 'tail' of the contaminant. This change of setting of the foreign fiber detecting device on the draw bench need only be done close to the position of the contaminant, the position of the contaminant being already stored in the label associated with the can being processed. This avoids running the draw bench with the foreign fiber detector continuously set at a very sensitive level (risk of false alarms and unnecessary machine outage). In addition the reader processor 22, 24, 26, 30 can activate a pre-alarm in order to inform the worker that the machine will stop soon.
In accordance with the present invention marking/selecting the intermediate product 15 at each stage up to the open end spinning machine may be used to adjust the settings of a later or earlier detection system and/or marking the final bobbin with the 'history' of yarn production. Dependent on the pre-processing history stored in the label 17, 19 an alternative selection may be made between good and bad quality (normally not all of the contaminants are removed, thus material with a 'good history' commonly produces better yarn than material with a 'bad history'). A flow diagram of a process in accordance with this embodiment is shown in Fig. 6 which will be described with reference to a foreign fiber detector at the exit of a carding machine as an example. In step 71 the label on the can is read including the running contamination index (RCI). The RCI is a weighted average of the contamination indices from previous machines. The RCI therefore gives a measure of the "history" of the intermediate product up to this point. In step 72 the intermediate product (IP) is processed on the machine and the foreign fiber intensity, position, type etc. is recorded onto the label. From these values a current contamination index (CCI) is calculated based on a suitable algorithm. In step 73 the new RCI is calculated by taking a weighted average of the old RCI and the new CCI, e.g. RCI = w₁ x RCI + w₂ x CCI, (w₁ + w₂ = 1) and the value stored. In step 74 it is examined if the CCI is above a certain first upper threshold (indicating poor quality). If yes in step 74 a flag is incremented in step 75. The flag may be reset every suitable time period. In step 76 it is determined if the CCI is above a certain threshold. If yes in step 76 this is an indication of general bad quality. In step 77 it is determined if the value of the flag is above a certain number N₁, e.g. 3. If yes in step 77 it indicates that several bad quality cans are being processed and bale tracing in the blow room is carried out in step 78 to remove a suspected poor bale. If no in step 76 or step 77 this may indicate that the upstream detectors are not set fine enough and the foreign fiber detectors upstream of the card are increased in sensitivity in step 79 to remove more contaminant. If no in step 74, it is determined in step 80 whether the RCI is above a threshold. If yes in step 80 the processing is continued as normal. If no in step 80 it is determined in step 81 if any foreign fiber has been determined in this can. lf yes in step 81 then the next downstream detectors and machine are alerted to remove this contaminant in step 82. In no in step 81 a flag is increased by one in step 83. The flag may be reset as soon as the answer to step 81 is yes. In step 84 it is determined if the flag is greater than a certain number, N₂, say 20. If yes in step 84 this means that very high quality material is being processed. In step 85 the detectors upstream are lowered in sensitivity to remove less good material. If no in step 84, the can is processed normally.
In a further embodiment of the present invention the labels need not be attached to the work in progress. For example, each can processed on a carding machine may be given a number. During processing of this can, information relating to foreign fiber content may be transmitted from the foreign fiber detector on the carding machine to a centralized computer and stored there with a link to the can number. When this can is processed at the next stage, the quality information can be read from the computer by inputting the can number. For example, as shown schematically in Fig. 2, the machine park 2, 4, 6, 8, 10 of Fig. 1 may include a centralized computer system 31, 33, 35, 37. Each intermediate product 15 is provided with a label 17 or 19 as described with reference to Fig. 1, e.g. all intermediate product is marked with a passive code (e.g. number, fixed BAR-CODE on a can or bobbin) which identifies it. If all machines are linked to a central unit, each intermediate product can be identified at each machine or other places in the spinning mill with a simple read device. This label only needs to contain a reference number for the relevant intermediate product. This number is read by a reader and processor 32, 34, 36, 38, 40 at each machine 2, 4, 6, 8, 10. The local processor 32, 34, 36, 38, 40 may retrieve data relating to the reference number from a centralized computer 31 having a processor 33 and non-volatile read/write memory 35. Alternatively, the central computer 31 may download the respective data from its memory 35 on receipt of the reference number as well as a number defining the relevant machine 2, 4, 6, 8, 10. Based on the received information the processor 33, or the reader and processor 32, 34, 36, 38, 40 may decide the appropriate action which may be the same as described for the system according to Fig. 1, i.e. stop the machine and reject the product, change the settings of the foreign fiber detection unit on the machine or move the intermediate product to another machine.
The reader and processor 32, 34, 36, 38, 40 on each machine 2, 4, 6, 8, 10 receives operating data from that machine including, where available, information with respect to foreign fiber detection from a foreign fiber detector 12, 14, 16, 20. This data is transmitted to central computer 31 via bus 37 and this information is stored in the memory 35 of computer 31 with a link to the reference number of the intermediate product and to the machine on which it was processed, thus updating the history.
Fig. 3 is a schematic representation of a further machine park of a spinning mill with which the present invention may be used. It shows the combination of a centralized computer/foreign fiber detection system described with reference to Fig. 2 and the automatic delivery system described with reference to Fig. 1. The functions of the reader and processors 22, 24, 26, 28, 30 of Fig. 1 and 32, 34, 36, 38 and 40 of Fig. 2 are now incorporated into reader and processors 42, 44, 46, 48, 50 respectively. In accordance with this embodiment of the present invention the recorded quality data in the label may not only be used to modify the settings of a quality control sensor on a processing machine either downstream or upstream of the machine where the data was recorded but also to select the next processing machine further downstream in the processing based on the stored information in the label. For example, normally contaminants occur in clusters. With an increasing 'contamination rate' at the card, the settings of the foreign fiber detection devices in the upstream machines such as the opening line can be adjusted in order to detect more contaminants (with the disadvantage of loosing good material but with the advantage of greater efficiency downstream). Further, the stored quality information in the labels may be used for tracing purposes and action taken. For example, knowing the retention time of the individual tufts in the pipeline of the blow room the relevant cotton bale can be determined from where the contaminant originates and this bale can be removed (based on the fact that normally there exists contaminated bales with many contaminants and contaminant free bales). if the card is not stopped or a doffing forced, tracing and/or control of the further processing of the can is necessary, i.e. rectifying action may be taken at a later machine. This may be done by using the information in the label.
By combining the centralized computer system 31 with an automatic transport system the functions of the control system in accordance with the present invention may be partitioned between the two to obtain good efficiency and fast response. There may be a partitioning between local sensing, reading at machine level, and more strategic decisions taken at a higher level in the central computer 31.
In accordance with a further embodiment of the present invention when all foreign fiber detection systems 12, 14, 16, 20 are linked to the centralized computer system 31, this may be adapted to decide where to remove a detected contaminant e.g. at the card or at the draw frame or the open end spinning machine. The decision may be made dependent on the actual efficiency or quality at different processing stages and the material to be processed at the relevant stage. In this way the overall efficiency of the spinning mill can be increased. The traceability is not restricted to the spinning mill, further to the weaving mill is straightforward. In place of a complicated code the cans can be marked simply but automatically and visible allowing the workers to select the cans manually. As described with reference to the above embodiments of a spinning mill different detection systems 12, 14, 16, 20 may be installed at different positions in the production line. Each system 12, 14, 16, 20 may be able to remove the contaminant automatically with minimal interruption of the material flow (e.g. in the blow room), or by stopping the machine and removing the contaminant automatically (short interrupt of the material flow e.g. at a winder or OE spinning machine) or by stopping the machine and alarming a worker to inspect and removing the contaminant. The systems described with reference to Fig. 2 and 3 are typical installation positions of such systems but these can be easily transferred to other positions (e.g. combing machine, flyer, mixer, etc.). Each Detection/Removing system with its own processing unit (e.g. PC or u-controller) is connected to a central processing unit. In accordance with the present invention either the central unit or local units (if appropriate) may decide:

to remove the contaminant at the actual machine,
to record (label the IP) the contaminant including the exact position of the contaminant and trace the course of the material, e.g. as it is moved by a transport device. This enables changing the settings of a subsequent machine in order to detect and remove the contaminant safely. For example, the quality control device in the later machine may be changed from low sensitivity to high sensitivity only for the appropriate moment (e.g. at card detecting but not stopping the machine, labeling the can with the right information, reading the information at the draw frame, changing the settings of the detection system. A similar processing may be done between draw frame and the open end spinning machine , winder, flyer, etc.). In accordance with the present invention a labeling device is provided which writes the information on the transport container, as well as a device which reads the information at the subsequent machine. Alternatively with a material transport system, the information may be stored in a central processing unit and acquired for later machines as required.
to determine a statistical value of number of contaminants (e.g. contamination index = number of contaminants/100km) and changing working point of all machines in order to minimize this index with the same production.
to select material for processing dependent on contamination index (with labeling and/or alarm setting)
to trace contaminant back to cotton bales in order to remove individual bales.
to change parameters at a previous machine in order to minimize contaminants at the actual machine (e.g. high contamination index at card → changing sensitivity of bale opener system or blow room system).
to trace the whole material flow in order to trace a contaminant in a textile web back to its origin (cotton bale → ginner).

The decision(s) may be made dependent on at least one of the following criteria:

Optimization of material flow. The stop of a machine at the begin of the production line or in the middle may be made dependent on the buffered material between machines. For example, a card can be stopped if there is enough material for the draw frames. If no material is buffered in the spinning preparation and the spinning room the sensitivity of the systems in the blow room may be increased (with the disadvantage of loosing good material).
Predicting material bottlenecks in order to decide whether an individual machine can be stopped.
Maximization of last machine efficiency.
Using feedback from quality control results on the final woven web and changing parameters in order to reduce number of contaminants (e.g. accepting some loss of efficiency to improve the quality).
Analyzing the results of simulating the effect of changing parameters.

Moreover in accordance with a further embodiment of the present invention the machines 12, 14, 16, 18, 20 in the machine park may be formed into smaller groups, e.g. linked to each other, to form a sub-group of one of the systems described with reference to Figs. 1 to 3. The sub-system may have its own local computing power in order to get a faster response for changes within the sub-group. Within the sub-group system there may only be control of the machines in the sub-group. Control outside the sub-group reverts to a centralized computer in a hierarchical manner.
In accordance with a further embodiment of the present invention the foreign fiber detection systems associated with respective machines may be linked together to form a single unit with associated electronic processing machines running computer programs capable of finding the optimum operating points and conditions of each sub-system. As each individual setting of a detection system influences the whole production line in a spinning mill this global optimization system adjusts the settings of the other detection systems and of other machines to obtain optimum performance from the whole. The control system may be configured with self-organizing and self-teaching abilities in order to find the best strategy, e.g. implementations as a neural network.
A schematic block diagram of such a system 50 is shown in Fig. 4. The heart of the system 50 is a spinning mill decision center 56. Performance data of the machines in the machine park and their efficiencies given certain product to process, certain levels of contamination and certain sensitivity settings of the foreign fiber sensors as well as the efficiency of any clearers and the effect on machine down-time caused by various levels of contamination at each stage are preferably available to the operator of the decision center 56. Further, the present order situation may also be input along with target efficiencies and manufacturing costs, machine occupations, shift durations and number, public and works holidays and any other data which affects the operation of the spinning mill.
A foreign fiber detection system 54 delivers data at all stages of the process from the detection systems on the machines to the spinning mill decision center 56 as well as the settings, e.g. current levels of sensitivities, of the detectors. The decision center 56 also receives data on the present operation of the processing machines, e.g. their speeds and efficiencies from machine operations capture system 58. The decision center 56 compares the current data and displays a list of machines running at efficiencies below target, and intermediate product of below target quality. Based on this current data, the the outputof the mill is examined against predetermined target levels. If the output is below target either in quality or machine efficiency, an operator may propose downstream and/or upstream modifications (feedforward or feedback control), in particular downstream and/or upstream modifications to a setting of a quality control detector or the selection of a specific downstream machine or the removal of product, e.g. contaminated bales, from production. The decision center 56 may propose such changes automatically. The analysis may be continued until a suitable control modification plan has been obtained. At this point the decision center 56 may activate a control and transport system 59 based on the modified plan as well as sending setting modifications to the detector system 54 and the machine operation 58. The implemented control changes may include changing sensitivities of the individual detectors on the machines, changing the operation of individual machines, moving intermediate product to specific machines or removal of raw (bad bales) or intermediate product (severely contaminated product) from the system in order to optimize the process and achieve the efficiency and cost targets required of the system. The decision center 56 may make use of any of the decisions and criteria listed above as suitable for controlling a spinning mill.
In accordance with a further embodiment of the present invention, for any of the previous embodiments of a control system or method and particularly for the global control system described with reference to Fig. 4, the control may be improved by using one set of detectors as master detectors. The control system and method for the whole spinning mill or a part of the mill is then based on the output of the master detector(s). The master detectors may be foreign fiber detectors or any other quality control detectors. Ideally, a master detector should be located somewhere in the middle of the process so that there are still opportunities for downstream control and sufficient data has been obtained on previous machines to make a valid judgment. In accordance with the present invention a master detector is preferably placed at the exit of a carding machine or at the entrance to a draw bench, e.g. in the creel. At this position the IP is in the form of a sliver and is therefore of a relatively well defined shape. Also the fiber product has been processed by several machines at this point so that quality data is available. The decision process may be as described with respect to Fig. 4 except that the data input by the detection system is reduced to only the data and setting levels obtained from the master detectors thus reducing the total amount of data which has to be processed.
While the invention has been shown and described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes or modifications in form and detail may be made without departing from the scope and spirit of this invention as defined in the attached claims.

Claims

A quality control system for a production unit comprising a plurality of different processing machines which carry out processing on intermediate product and which operate sequentially and optionally in parallel; comprising:

a first sensor monitoring at least a first quality parameter of a first intermediate product in a first processing machine;

a second sensor monitoring at least a second quality parameter of a second intermediate product in a second processing machine;

a first device for recording the values of the first quality parameter output by the first sensor; and

a second device for altering the setting of the second sensor in response to the recorded quality values from the first sensor.
The system according to claim 1, wherein the first and second quality parameters are the same parameter.
The system according to claim 1 or 2, wherein a quality parameter is related to the presence or intensity of unwanted foreign materials in the intermediate product
The system according to any previous claim, wherein the setting of the second sensor is a sensitivity level.
The system according to any previous claim, wherein, the system relates to a spinning mill.
The system according to claim 5, wherein the quality parameter is the presence of foreign fiber in a sliver, roving, web or yarn.
The system according to any previous claim, wherein the second device is adapted to alter the setting of the sensor on the second machine only when the intermediate product processed by the first machine reaches the second machine.
The system according to any previous claim, further comprising a third device for storing the quality values from the first sensor.
The system according to claim 8, wherein the third device is physically associated with said first intermediate product.
A method of a controlling quality in a production unit comprising a plurality of different processing machines which carry out processing on an intermediate product and which operate sequentially and optionally in parallel; the method comprising the steps of:

a first monitoring step for monitoring a first quality parameter of an intermediate product being processed in a first processing machine;

a second monitoring step for monitoring a second quality parameter of a second intermediate product being processed in a second processing machine;

recording the values of the first quality parameter output by the first monitoring step; and

altering at least one monitoring parameter of the second monitoring step in response to the recorded quality values from the first quality step.
The method according to claim 1, wherein the first and second quality parameters are the same parameter.
The method according to claim 10 or 11, wherein the altering step includes altering a sensitivity of the second sensor.
The method according to claim 11 or 12, wherein a quality parameter is related to the presence or intensity of unwanted foreign materials in the intermediate product.
The method according to any of claims 10 to 13, wherein, the method relates to the operation of a spinning mill.
The method according to claim 14, wherein the quality parameter is the presence of foreign fiber in a sliver, roving, web or yarn.
The method according to any of the claim 10 to 15, wherein the altering step includes altering the setting of the sensor on the second machine only when the intermediate product processed by the first machine reaches the second machine.
A quality control system for a production unit; comprising:

a first sensor monitoring quality of an intermediate product in a first processing machine carrying out a first processing step;

a second machine for carrying out a second processing step on an output of the first machine, the second machine having a quality control device for a quality parameter;

a third machine also for carrying out the second processing step on an output of the first machine, the third machine not having a quality control device for the quality parameter;

a first device for recording the quality values output by the first sensor; and

a selector for selecting one of the second and third machines for processing the output of the first machine, the selection being based on the recorded values from the first sensor.
The system according to claim 17, wherein the quality parameter is related to the presence or intensity of unwanted foreign materials in the intermediate product
The system according to claim 17 or 18, wherein, the system relates to a spinning mill.
The system according to claim 19, wherein the quality parameter is the presence of foreign fiber in a sliver, roving, web or yarn.
The system according to any of claim 17 to 19, further comprising a second device for storing the quality values from the first sensor.
The system according to claim 21, wherein the second device is physically associated with said first intermediate product
A method of a controlling quality in a production unit, the production unit comprising a first processing machine for carrying out a first processing step on an intermediate product, a second processing machine for carrying out a second processing step on an output from the first machine, the second machine having a quality control device for a quality, and a third processing machine also for carrying out the second processing step on an output of the first machine, the method comprising the steps of: monitoring the quality of the intermediate product in the first processing machine; recording the quality values output by the monitoring step on the first machine; and selecting one of the second and third machines for processing the output of the first machine based on the recorded quality values for that intermediate product.
A method for controlling a spinning mill comprising a plurality of different processing machines which carry out fiber processing on fiber product and which operate sequentially or in parallel, the fiber processing producing different fiber structures at the exit of different machines; comprising the steps of:

detecting foreign fibers or material on at least one of the processing machines; and

processing the results of the detecting step to optimize the operation of at least some of the other processing machines.
A control system for controlling a spinning mill comprising a plurality of different processing machines which carry out fiber processing on fiber product and which operate sequentially or in parallel, the fiber processing producing different fiber structures at the exit of different machines; comprising: a detector of foreign fibers on at least one of the processing machines;
a processor for processing the results of the detecting step and to optimize the operation of at least some of the other processing machines.
The system or method according to claim 24 or 25, wherein the optimization includes downstream control modifications and/or upstream control modifications with reference to the location of the detector.
The system or method according to any of claims 24 to 26, wherein the optimization includes one or more of the following decisions and optionally the relevant action derived therefrom:

a decision to remove the contaminant at the actual machine where it has been detected,

a decision to record (label) the contaminant including the exact position of the contaminant and tracing the course of the material, e.g. as it is moved by a transport device to other machines,

a decision to change the settings of a subsequent machine in order to detect and remove the contaminant safely,

a decision to change the settings of a quality control device in a later machine from low sensitivity to high sensitivity or vice versa, for example only for the appropriate moment when the contaminant is expected to arrive in the subsequent machine,

a decision to determine a statistical value of number of contaminants and to change the working point of at least some of the machines in order to minimize this index with or without the same production level,

a decision to select material dependent on the contamination index (with labeling and/or alarm setting),

a decision to trace contaminant back to cotton bales in order to remove individual bales,

a decision to change parameters at a previous machine in order to minimize contaminants at the actual machine,

a decision to trace the whole material flow in order to trace a contaminant in a textile web back to its origin.
The system or method according to claim 27, wherein any of the above decisions and/or actions may be made dependent on at least one of the following criteria:

Optimization of material flow,

Predicting material bottlenecks in order to decide whether an individual machine can be stopped,

Maximization of last machine efficiency,

Using feedback from quality control results on the final woven web and changing parameters in order to reduce number of contaminants while optionally accepting loss of efficiency to improve the quality,

Analyzing the results of simulating the effect of changing parameters.