SENSOR SYSTEM AND METHOD FOR WEB MANUFACTURING

Abstract

The present invention provides a sensing system and method adapted for use in monitoring and detecting features of a web for manufacturing. The sensing system has an energy source adapted to project an energy beam onto the web and a sensor positioned relative to the web and the energy source to sense attenuation of the energy beam from the energy source to detect, locate, identify, or measure the web or its features. The method includes passing the web through a light from a light source, measuring attenuation of the light from the light source with an optical sensor, and identifying an optical signature as a function of attenuation for characterizing the web and/or its feature.

Description

BACKGROUND

The present invention relates to articles of manufacture prepared from a material web, and in particular to the manufacture of plastic bag rolls suitable for use in most application, including for example, trash can liners, produce bags, and the like. Plastic bag rolls are typically built by continuously extruding plastic film through a die to form a bubble. The bubble, tubular in shape, is later reduced in width to that of the desired bag by flattening the shape and introducing folds known as gussets using rollers. Once flat, the web may be printed before conversion into bags. Timing marks may be incorporated into the print.

Two types of machines are usually involved in the final step, known as conversion. The first machine, commonly referred to as the ‘bag machine,’ perforates and seals the bag web at intervals that determine the length of the final bag. The seals and perforation are approximately perpendicular to the web. The second machine, commonly known as the ‘winder,’ separates the web at the perforation if an overlapped bag is being built but always winds the web into a roll while counting the bags. The ‘winder’ automatically transfers a new spindle into the web to continue winding bags when a roll has been completed.

Because the perforation is introduced onto the web in a different machine than the machine that winds the roll, the ‘winder’ must synchronize its operation to the location of the perforation and seal. The device used to determine the location of the perforation on the web is referred to as the ‘counter.’ The most prevalent form of counter is a perforation spark gap detector. This design incorporates two electrodes at a high voltage potential, one on each side of the web, at close proximity. When the plastic bag is between the electrodes, it acts as an insulator. However, when the perforation section passes the electrodes, the insulator is compromised and a spark can jump the gap between the electrodes. Such a design is not always satisfactory, as the high voltage used for sensing also induces a static bond between the layers of the plastic bag. This effect increases the difficulty that a person will have in opening the bag. Furthermore, the presence of an exposed high voltage device on the input of the winding machine often causes operator shocks. Moreover, the sensor can only detect the perforation, and not any other features of the bag and/or plastic bag web.

Therefore, a need in the art has been identified to provide a sensor system to identify, track, locate, and/or measure features associated with a plastic bag web, such as bag seals, perforations, printed markings, skirt length, or other features on the plastic roll, bag or bag web.

SUMMARY OF THE INVENTION

These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. In one aspect of the present invention a sensing system adapted for use in monitoring and detecting features of a web for manufacturing is disclosed. The sensing system includes an energy source adapted to project an energy beam onto the web and a sensor positioned relative to the web and the energy source to sense attenuation of the energy beam from the energy source to detect, locate or measure the web or features of the web. In a preferred form, the energy source is a light source and the energy beam is a light beam. The energy source is positioned on one side of the web and the sensor is aligned with the energy source on an opposite side of the web so that the web passes between the energy source and the sensor. In a preferred form, at least a portion of the energy beam is transmitted through the web so that the portion of the energy beam passing through the web is sensed by the sensor. The sensing system also includes a comparator in data communication with the sensor to measure a difference in energy between the energy beam and the portion of the energy beam that passes through the web. The sensing system identifies the difference as energy signatures for the web and/or a feature of the web, which may include but are not limited to: a) a perforation of the web; b) a seal of the web; c) a timing mark of the web; d) a skirt length of the web; or e) any part or dimension of the web ascertainable by measuring attenuation of the energy beam.

In another aspect of the present invention, a plastic bag manufacturing machine adapted to detect the existence and/or location of one or more features in the bag is disclosed. The machine includes a machine frame with one or more components for supporting and handling a plastic bag web, an energy source on the machine proximate the plastic bag web to project an energy beam onto the plastic bag web, and a sensor on the machine proximate the plastic bag web and the energy source to sense attenuation of the energy beam projected onto the plastic bag web from the energy source. In a preferred form, the energy source is a light source, the energy beam is a light beam and the light source is adjustable in intensity or frequency to be tuned to each specific plastic bag web or to filter out background light. The energy source may be positioned on the machine on one side of the plastic bag web and the sensor aligned with the energy source on the machine on an opposite side of the plastic bag web to sense at least a portion of the energy beam passing through the plastic bag web, or the energy source and the sensor may be positioned on the machine on one side of the plastic bag web so that the sensor is positioned relative the energy source and the plastic bag web on the machine on the one side to sense at least a portion of the energy beam reflected off of the plastic bag web.

A method of the present invention for detecting and measuring one or more features of a bag web is also disclosed. The method includes the steps of passing the bag web through a light from a light source, measuring attenuation of the light from the light source with an optical sensor, and identifying an optical signature as a function of attenuation for characterizing the bag web and/or its features. In a preferred form, the method includes the steps of: a) acquiring the optical signature from the optical sensor with a controller for comparing with a record describing what optical signatures should have been acquired; and, b) associating the line speed of the bag web with the record of detections for each optical signature for: i) confirming the presence of each feature of the bag web, ii) measuring one or more of the features of the bag web, and/or iii) determining false/positive readings from the optical sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 is a front elevation view of a plastic bag manufacturing machine of the prior art with the sensing system of the present invention.

FIG. 2 is a top view of the plastic bag web taken along line 2-2 in FIG. 1

FIG. 3A is a side view of the plastic bag web taken along line 3A-3A in FIG. 1.

FIG. 3B is another exemplary embodiment of the sensing system of the present invention shown in FIG. 3A.

FIG. 4 is a simplified electrical block diagram of the sensor system according to an exemplary embodiment of the present invention.

FIG. 5 is a flow chart of the feature detection function of the sensor system according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

The present invention is directed towards a sensing system and method adapted for use in manufacturing bags from a bag web and for use in detecting features associated with the bag or bag web.

Referring now to FIG. 1, a plastic bag manufacturing machine 10 of the kind that is commercially available is shown by way of example. Those skilled in the art can appreciate that plastic bag manufacturing machine could be a paper, plastic, metal or any other web type manufacturing machine. The plastic bag manufacturing machine 10 could be a bag machine, a winder, a counter as discussed in the Background or any other machine for manufacturing plastic bags suitable for adaptation with the sensing system 20 of the present invention. The present invention should not be construed as being limited to plastic bag manufacturing machines only. The present invention contemplates that sensing system 20 could be used to monitor, detect, or measure features in other bag webs for manufacturing products where detection by attenuation of an energy beam is plausible, such as for example bag webs of materials suitable for detecting, measuring, locating, or monitoring features of the bag web by attenuation of an energy beam transmitted or reflected off the web. The plastic bag manufacturing machine 10 of the prior art includes a frame 12 for supporting one or more rollers 14 or other components for handling, supporting and shuttling the plastic bag web 16 through the machine. The plastic bag web 16 may be unrolled from a plastic bag roll, such as bag roll 18, or received from another bag manufacturing machine in communication with or tied to plastic bag manufacturing machine 10. The plastic bag manufacturing machine 10 may include controls 24 for operating, controlling and monitoring machine 10. The plastic bag manufacturing machine 10 may also be operated by being linked up by wire or wirelessly with computer 22. Those skilled in the art can appreciate that computer 22 could be any programmable or other controller unit, such as a programmable logic controller (PLC). The controller may include a data store. Computer 22 could be in data communication with plastic bag manufacturing machine 10 to monitor operating parameters of machine 10 such as line speed of the plastic bag web 16. Computer 22 may also be in data communication with sensing system 20 for monitoring, controlling or tuning sensing system 20. The computer 22 or alternatively a controller with a data store could receive and store information, such as readings from sensor 36 (shown in FIG. 3A-B and 4). The computer 22 or alternatively a controller could also be used to control operation of sensing system 20.

Referring now to FIG. 2, a plastic bag web 16 that contains a seal 26 and perforation 28, and optionally a printed mark 30 is shown by way of example. Other optically detectable (or detectable by energy attenuation) and/or notable features of the plastic bag web 16 include skirt length and other like dimensions valuable in ascertaining information about the plastic bag web 16 or plastic bag during manufacturing, handling, packaging or the like. Plastic bag web 16 or plastic bags, like the type illustrated in FIG. 2, are generally manufactured in commercially available machines, such as the machine shown in FIG. 1. The bags manufactured by these machines have a wide variety of uses, including, for example, trash can liners, and produce bags and other like uses for storage or disposal.

Plastic bag rolls or plastic bag webs 16 are typically constructed by continuously extruding plastic film through a die to form a bubble. The bubble, tubular in shape, is later reduced in width to that of the desired bag by flattening the shape and introducing folds known as gussets using rollers. Once flat, the plastic bag web 16 may be printed on before conversion into bags. Timing marks may be incorporated into the print. In the final stages of manufacturing the bag, a machine, referred to as a “bag machine,” perforates and seals the plastic bag web 16 at intervals that determine the length of the final bag. Other machines such as a “winder” may separate the plastic bag web 16 at the perforation if an overlap bag is being built, but ultimately, the “winder” winds the plastic bag web 16 into a roll while counting the bags. The winder may be adapted to automatically transfer a new spindle into the plastic bag web 16 to continue winding bags when a roll is complete.

Because the perforation 28 is introduced into the plastic bag web 16 in a different machine than the machine that winds the roll, the winder is adapted to synchronize the operation to the location of the perforation 28 and the seal 26 on the plastic bag web 16. The device used to determine the location of the perforation 28 on the plastic bag web 16 is often referred to as “counter.” In the prior art, these counters commonly consist of a perforation spark gap detector. Spark gap detection incorporates two electrodes at a high-voltage potential, one on each side of the bagging, at close proximity. When the plastic bag web 16 is between electrodes, it acts as an insulator. However, when the perforation section passes the electrodes, the insulator is compromised and a spark can jump the gap between the electrodes, which is tracked and identified to determine the location of the perforation on the plastic bag web. As discussed in the background, such a design is not always satisfactory, as high-voltage use for sensing also induces a static bond between the layers of the plastic bag. This effect increases the difficulty that a person will have in opening the bag. Furthermore, the presence of an exposed high-voltage device on the input of the winding machine often results in operator shocks. Further, the sensor can only detect the perforation 28 and not any other feature associated with the plastic bag web 16. Because the prior art has these and other limitations, the sensing system 20 of the present invention has been provided to identify, track, locate, and measure features associated with the plastic bag web 16, such as bag seals 26, perforations 28, printed markings 30, or other features on the plastic bag web 16, which may be identifiable, measurable, locatable, and/or detectable by measuring attenuation of an energy beam transmitted through or reflected off of the material used for the bag web, such as plastic bag web 16.

One exemplary embodiment of the optical sensor is shown in FIG. 3A. The sensing system 20 and methods of the present invention may include one or more energy sources 32, such as a light source or any other source capable of emitting energy beam 34, and one or more sensors 36, such as an optical sensor, aligned with energy source 32, energy beam 34 and relative to the plastic bag web 16 such that one or more optically identifiable features (or features identifiable by attenuation of an energy signal) in the plastic bag web 16 may be detected, measured, or positionally identified. In one exemplary aspect of the present invention, plastic bag web 16 may be passed between the aligned energy source 32 and sensor 36 as illustrated in FIG. 3A, whereby an energy beam 34, such as a light beam, from energy source 32 is attenuated as it passes through the plastic bag web 16. The amount of attenuation may be detected at the sensor 36, such as an optical sensor/detector in the case where the energy source 32 is emitting light. Thus, by attenuation of energy beam 34 from energy source 32 passing through the plastic bag web 16, the sensor 36 is able to identify energy signatures associated with each of the features of the plastic bag web 16. For example, in the case where the energy source 32 is a light source, attenuation of light from the light source passing through the plastic bag web 16, is captured by an optical detector, which associates an optical signature with each of the features of the plastic bag web 16, such as the seal 26, perforation 28, printed mark 30, or other optically identifiable features of the plastic bag web 16. Each of these features and other optically identifiable features of the plastic bag web 16 are optically identifiable because they each possess different optical characteristics from each other and the rest of the plastic bag web 16. Using the differences in optical characteristics of these features, their respective locations and measurements may be derived. For example, knowing the line speed of the plastic bag web 16, sensing system 20 could deduct the measurements of one or more features of the plastic bag web by comparing the time between detections with the line speed of the plastic bag web 16. This could be accomplished using a detection algorithm operating as part of the sensing system or computer 22. In the case where the energy source emits light, the attenuation of light from the energy source 32, as previously discussed, may be detected or measured using a sensor 36, such as an optical detector. The optical detector may include a phototransistor, photodiode or like device suitable for measuring attenuation of light source and/or determining an optical signature (as a function of attenuation) for each feature associated with the plastic bag web 16.

Another exemplary embodiment of the sensing system 20 and methods are illustrated in FIG. 3B. In this embodiment, the energy source 32 and sensor 36 are aligned and positioned with respect to the plastic bag web 16 so as to measure or detect variation or attenuation in the energy beam 34 reflected off of the plastic bag web 16 and/or features of the plastic bag web 16. For example, in the case where the energy source 32 is a light source and the sensor 36 is an optical sensor, the two may be aligned and positioned with respect to the plastic bag web 16 so as to measure or detect variances or attenuation in the light to detect changes in the optical characteristics of the plastic bag web 1 using reflective light as an optional detection scheme. In this example, the optical detector/sensor may be positioned relative to the plastic bag web 16 and the light source so that reflected light from the plastic bag web 16 may be detected and attenuation of the reflected light measured (compare the reflected light to the emitted light) to distinguish specific features of the plastic bag web 16 from the rest of the plastic bag web 16.

The present system and methods contemplate other options for identifying the plastic bag web 16 and features of the plastic bag web 16. In one aspect of the present invention, features of the plastic bag web 16 may be identified, located, and measured by comparing the measured energy beam 34 or light to a set point or previously measured light level, such as emitted energy or light levels, that are correlated to or associated with each of the specific features of the plastic bag web 16, such as the perforation 28, seal 26, printed mark 30, skirt length (the distance between perforation 28 and seal 26), or other features of the plastic bag web 16 identifiable by attenuation of energy beam 34, such as optically identifiable features. In another aspect of the present invention, sensing system 20 may be adapted such that the electrical response of the optical sensor may be compared to a threshold response known to represent the overall plastic bag web 16 response to determine if a seal 26, perforation 28, printed mark 30, or other bag features are positioned at the detection aperture between the detector and light source. Furthermore, a baseline response for the plastic bag web 16 may be generated and compared with the response received from each of the features of the plastic bag web 16 when light from the light source is attenuated by transmission or reflection from the various features on the plastic bag web 16. The comparison algorithm for comparing emitted and measured light could be part of sensing system 20 and/or computer 22 (shown in FIG. 1). In other aspects of the present invention, sensor 36 may have features for internal regulation of the frequency and intensity of the energy source 32, such as the light source, so that it can be tuned to a particular plastic bag web 16 or to filter out background light radiation. Computer 22 or a controller in communication with sensing system 20 may also be used to tune the light source to each specific plastic bag web 16 and/or the background light by comparing emitted and measured light readings. In the case where the energy source 32 is a light source, light emitted from the light source may also be adjustable in intensity or frequency. 4. The sensing system 20 may also be configured to maintain a historical record of detections versus time, line speed of plastic bag manufacturing machine 10 or other parameters such that various bag characteristics or features can be determined, measured, located, or identified. The sensing system 20 may include a controller and data store for processing and storing detection information or operating cooperatively with computer 22. The sensing system 20 may also be adapted to use this historical record to substitute missing detection information at the correct intervals, if necessary.

FIG. 4 illustrates an exemplary electrical schematic of energy source 32, sensor 36, and controller 46. Energy source 32 may include, but is not limited to, a regulator 38 that is adapted to convert the available power to a suitable form for the energy source 32 whereby the intensity, frequency, or other parameters of the energy source 32 may be controlled and tuned specifically to the plastic bag web 16 by controller 46 in communication with regulator 38. In another aspect, as also illustrated in FIG. 4 relating to sensor 36, the measured signal from detector 38 may be amplified with amplifier 42 and ultimately compared or correlated to one or more thresholds associated with the plastic bag web 16 in comparator 44. The signal may be converted from an analog signal to a digital signal at any point to optimize processing of data from the detector 40, whether processed in real-time or post-processed with processing algorithms on computer 22 or a controller with a data store as part of the sensing system 11. The regulator 38, energy source 32, detector 40, amplifier 42, and comparator 44 may be operated by computer 22, a controller or a CPU having a control board and programmed with code as shown in the FIG. 5 for operating the detection function of the sensing system 20. Using computer 22 or a controller with a data store not shown, detection data may be collected from the detector 40, such as signal levels or otherwise, time-stamped or otherwise, to perform analysis of the signaled response. Signal thresholds may be determined using the comparator 44. Comparator 44 may be configured to assess statistical methodologies programmed in the computer 22 or a controller to determine the average response of the detector 40, to further identify false/positives detections, and/or supply information to controller 46 for operating the sensing system 20 and/or operational parameters of the plastic bag manufacturing machine 10. Signal response levels having a time signature and carrying embedded line speed information reported by the plastic bag manufacturing machine 10 to computer 22 may be used to measure dimensional parameters of the plastic bag web 16, such as length of the bag, seal 26, perforation 28, printed marks 30, or other optically detectable, measurable, or identifiable features of the plastic bag web 16.

Methods of the invention are also disclosed according to one or more exemplary embodiments. FIG. 5 illustrates a flow chart method for the featured detection function of the sensor system 20 of the present invention. In one exemplary aspect of the present invention, sensing system 20 is configured for detecting and measuring one or more features of plastic bag web 16 for manufacturing plastic bags. Those skilled in the art can appreciate that the sensing system 20 of the present invention could be used to measure, detect, identify and/or monitor features associated with any web used in manufacturing, such as a plastic, paper or metal web. The method includes one or more of the steps of passing the plastic bag web 16 through an energy beam 34, such as light, from an energy source 32, such as a light source, for measuring attenuation of energy beam 34 from the energy source 32 with a sensor 36. The method also includes identifying an energy signature, such as an optical signature, as a function of the resulting attenuation for characterizing the plastic bag web 16 and/or any of its features.

As previously indicated, the methods of the present invention are not limited to monitoring, identifying, and/or detecting features associated with the plastic bag web 16, but the methods of the present invention could be used to monitor, detect and/or measure features associated with any web of material, whether plastic, metal or paper webs used in a manufacturing process that use a web of material. For example, the figures such as FIG. 5 illustrate one exemplary method of the detection function of the present invention or the function for detecting, monitoring and/or measuring features associated with the web 16 used in manufacturing. The detection function could be started by a user inputting operating parameters such as selecting the type of material of the web 16 or the type of product to make from the web 16, such as a plastic bag. Based on these selections, operational parameters of the sensing system 20 are formulated and can be executed by computer 22 or any type of controller, such as a micro-controller in communication with an I/O device that in-turn is in communication with other external hardware structures such as energy source 32, energy beam 34, sensor 36, regulator 38, detector 40, amplifier 42, comparator 44, and/or controller 46 (as shown in FIG. 4).

Upon operation startup, sensing system 20 may acquire an initial timestamp, which could be used as a reference point in the detecting process, such as for example providing information based on the position of the web 16 and/or features in web 16, relative to the reference point. A second timestamp is taken upon the start of perforation 28 in plastic bag web 16. In the case where the start of a perforation 28 is not detected during the expected interval, thereby causing the perforation interval to expire, sensing system 20 checks to see if sensor 36 changed state, and if not provides a no detection warning. If the time interval for detecting perforation 28 has not expired, sensing system 20 checks to see if the sensor 36 has changed state. If sensor 36 has not changed state, sensing system 20 cycles again until a second timestamp is acquired upon the detection of the start of perforation 28. However, if sensor 36 changes state (i.e., an energy signal is detected in excess of the standard response for web 16) then sensing system 20 acquires a third timestamp indicating the end of perforation 28 in plastic bag web 16. In the case where the bounce interval doesn't expire (i.e., interval of time that the signal response is what the expected response should be for the feature in question) the system checks to see if sensor 36 has changed state, and if not repeats the process until either the bounce interval expires or sensor 36 changes state (indicating a detection of the end of perforation 28). In the case where the bounce interval has not expired, but sensor 36 has changed state (i.e., a third timestamp has been acquired for the end of perforation 28), sensing system 20 automatically increments the perforation bounce counter.

Alternatively, in the case where the bounce interval has expired (i.e., sensor 36 changed state and bounce counter was incremented), sensing system 20 acquires a fourth timestamp of the starting point for seal 26 in plastic bag web 16. In the case where the seal 26 interval (time allotted for detection of the seal) expires, meaning that no seal 26 was detected and sensor 36 did not change state, sensing system 20 attempts to reacquire the start of seal 26. If the start of seal 26 is detected, sensor 36 changes state and a fifth timestamp is acquired at the end of seal 26. In the case where the interval for detecting seal 26 expires, without a acquiring a fourth timestamp for the start of the seal 26, sensing system 20 increments the counter for the no seal counter. If the detection interval for seal 26 has not expired and sensor 36 has changed state, the sensing system 20 continues to cycle until the start of seal 26 is detected.

Sensing system 20 attempts to acquire a fifth timestamp at the end of seal 26. In the case where the bounce interval doesn't expire (i.e., interval of time that the signal response is what the expected response should be for the feature in question) and sensor 36 has not changed state, sensing system continues to cycle until sensor 36 changes state indicating a detection of the end of seal 26. In the case where the bounce interval has not expired and sensor 36 has changed state, sensing system 20 automatically acquires the fifth timestamp for the end of seal 26 and increments the seal bounce counter.

Alternatively, in the case where the bounce interval expired (i.e., sensor 36 changed state and bounce counter was incremented), sensing system 20 applies timing delays and provides an output pulse which increments the bag counter, which could be alternatively reset externally. In the case where the seal was detected, the system 20 uses the information to determine and perform statistical analysis, whether by real time or post processing, to determine dimensions, locations, and/or detection of the skirt length, seal length or seal bounces for plastic bag web 16. Alternatively, and in addition to the previous step, in the case where seal 26 was not detected, sensing system 20 can be used to determine other features associated with plastic bag web 16 such as perforation length, perforation bounces, perforation ratio, and/or bag length.

The embodiments of the present invention have been set forth in the drawings and specification and although specific terms are employed, these are used in the generically descriptive sense only and are not used for the purposes of limitation. Changes in the form and proportion of parts as well as in substitution of equivalents are contemplated as circumstances may suggest or are rendered expedient without departing from the spirit and scope of the invention as further defined in the following claims.

Claims

1. A sensing system adapted for use in monitoring and detecting features of a web for manufacturing, the sensing system comprising: an energy source adapted to project an energy beam onto the web; anda sensor positioned relative to the web and the energy source to sense attenuation of the energy beam from the energy source to detect, locate or measure the web and/or features of the web.

2. The sensing system of claim 1 wherein the energy source comprises a light source and the energy beam comprises a light beam.

3. The sensing system of claim 1 wherein the energy source is positioned on one side of the web and the sensor is aligned with the energy source on an opposite side of the web, the web passing between the energy source and the sensor.

4. The sensing system of claim 3 wherein at least a portion of the energy beam is transmitted through the web, the portion of the energy beam passing through the web is sensed by the sensor.

5. The sensing system of claim 4 further comprising a comparator in data communication with the sensor to measure a difference in energy between the energy beam and the portion of the energy beam that passes through the web.

6. The sensing system of claim 5 wherein the difference comprises an energy signature for the web and/or a feature of the web.

7. The sensing system of claim 6 wherein the feature comprises: a) a perforation of the web;b) a seal of the web;c) a timing mark of the web;d) a skirt length of the web; ore) any part, alteration or dimension of the plastic bag web ascertainable by measuring attenuation of the energy beam.

8. The sensing system of claim 1 wherein the energy source and the sensor are positioned on one side of the web, the sensor positioned relative the energy source and the web on the one side to sense at least a portion of the energy beam reflected off of the web.

9. The sensing system of claim 1 in combination with a machine for manufacturing plastic bags.

10. The sensing system of claim 1 in combination with a plastic bag winding machine.

11. The sensing system of claim 1 in combination with a plastic bag counter machine.

12. The sensing system of claim 1 wherein the web comprises: a) a paper web;b) a plastic web; orc) a metal web.

13. A plastic bag manufacturing machine adapted to detect the existence and/or location of one or more features in the bag, the machine comprising: a machine frame with one or more components for supporting and handling a plastic bag web;an energy source on the machine proximate the plastic bag web to project an energy beam onto the plastic bag web; anda sensor on the machine proximate the plastic bag web and the energy source to sense attenuation of the energy beam projected onto the plastic bag web from the energy source.

14. The machine of claim 13 wherein the energy source comprises a light source and the energy beam comprises a light beam.

15. The machine of claim 14 wherein the light source is adjustable in intensity or frequency to be tuned each specific plastic bag web or to filter out background light.

16. The machine of claim 13 wherein: a) the energy source is positioned on the machine on one side of the plastic bag web and the sensor is aligned with the energy source on the machine on an opposite side of the plastic bag web to sense at least a portion of the energy beam passing through the plastic bag web; orb) the energy source and the sensor are positioned on the machine on one side of the plastic bag web, the sensor positioned relative the energy source and the plastic bag web on the machine on the one side to sense at least a portion of the energy beam reflected off of the plastic bag web.

17. The machine of claim 13 further comprising a comparator to measure an energy difference between the energy beam and the portion of the energy beam reflected off of and/or transmitted through the plastic bag web.

18. The machine of claim 17 wherein the energy difference comprises a signature for the plastic bag web and/or a feature of the plastic bag web.

19. The machine of claim 18 wherein the feature comprises: a) a perforation of the plastic bag web;b) a seal of the plastic bag web;c) a timing mark of the plastic bag web;d) a skirt length of the plastic bag web; ore) any part or dimension of the plastic bag web ascertainable by measuring attenuation of the energy beam.

20. A sensing system for use in manufacturing plastic bags from a plastic bag web and adapted to detect the existence and/or location of one or more features of the bag and/or bag web, the sensing system comprising: a light source adapted to project a light onto the plastic bag web;an optical sensor positioned relative to the plastic bag web and the light source to sense attenuation of the light from the light source by transmittance or reflectance; anda comparator in communication with the optical sensor and the light source to measure attenuation of the light transmitted through or reflected off of the plastic bag web to provide an optical signature for the bag and/or one or more features of the plastic bag web.

21. The sensing system of claim 20 wherein the comparator comprises a phototransistor, photodiode or like device adapted to produce an electrical response for each optical signature associated with the bag and/or the features of the plastic bag web.

22. The sensing system of claim 20 further comprising a controller having a data store in communication with the comparator for storing data relating to the existence and/or location of the features of the bag and/or plastic bag web.

23. The sensing system of claim 22 wherein the controller is in communication with the sensor to detect, store, calculate, respond to, and prepare a history of attenuation versus time of attenuated light readings.

24. A method for detecting, monitoring and measuring one or more features of a plastic bag web for manufacturing plastic bags, the method comprising: mounting an energy source and a sensor proximate each other and a plastic bag web on a machine for manufacturing plastic bags;sensing a level of attenuation of an energy beam from the energy source transmitted through or reflected off of the plastic bag web and/or one or more features of the plastic bag web; andassociating the level of attenuation with each feature and/or the plastic bag web for monitoring, measuring and detecting the presence of each feature and/or the plastic bag web during manufacturing.

25. The method of claim 24 further comprising the step of tuning frequency and intensity of the energy source to each plastic bag web.

26. The method of claim 24 further comprising the step of creating a time record for each time the feature is detected for post-processing detections for the plastic bag web and/or the one or more features.

27. The method of claim 24 further comprising the step of measuring an energy signal for the one or more features comprising: a) a perforation of the plastic bag web;b) a seal of the plastic bag web;c) a timing mark of the plastic bag web;d) a skirt length of the plastic bag web; ore) any part or dimension of the plastic bag web ascertainable by measuring attenuation of the energy beam.

28. The method of claim 26 further comprising the step of substituting a missing detection for one of the features at a correct interval using the time record.

29. The method of claim 24 further comprising the step of characterizing the level of attenuation for each feature by comparing to a baseline level of attenuation for the plastic bag web.

30. A method for detecting and measuring one or more features of a bag web, the method comprising: passing the bag web through a light from a light source;measuring attenuation of the light from the light source with an optical sensor; andidentifying an optical signature as a function of attenuation for characterizing the bag web and/or each feature of the bag web.

31. The method of claim 30 further comprising the step of acquiring the optical signature from the optical sensor with a controller for comparing with a record describing what optical signatures should have been acquired.

32. The method of claim 31 further comprising the step of associating the line speed of the bag web with the record of detections for each optical signature for: a) confirming the presence of each feature of the bag web;b) measuring one or more of the features of the bag web; and/orc) determining false/positive readings from the optical sensor.