MXPA97010046A

MXPA97010046A - Processing with material leaf laser leaf

Info

Publication number: MXPA97010046A
Application number: MXPA/A/1997/010046A
Authority: MX
Inventors: W Robichaud Arthur; W Duffy Timothy
Original assignee: Combibloc Inc
Priority date: 1995-06-12
Filing date: 1997-12-11
Publication date: 1998-04-01

Abstract

The present invention relates to a process for treating material with laser, said process consisting of: imbricating loose sheets of said material on a conveyor, in such a way that each of said loose sheets of material is superimposed on a portion of one of said adjacent loose sheets of material, conveyor each of said loose sheets in a previously determined path, so that they move continuously, said path being in view of a laser system, and direct a laser beam from said laser system towards; a beam from said laser system towards said single sheets, one sheet at a time, successively

Description

LASER PROCESSING OF SINGLE LEAVES OF MATERIAL BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates, generally, to a system that is used to treat material with laser and, specifically, to a method and apparatus for rapidly providing scratch cuts or lines or other treatments to the material with laser. Many processing systems of the currently known employ a coil feed of uncut material in a process. For example, in the packaging industry, a continuous roll of material is fed through a printing system, which is then cut into individual packaging units that are folded to take the desired package configuration. Newspaper presses are another example of continuous feeding of material (in this case, paper) that undergoes a printing process and that is then cut into individual sections. Of course, printing is not the only process that is incorporated into such systems, and paper is not the only kind of material that is continuously fed into such systems. The industry in general has applied many different processes to many different materials in continuous feeding systems. The ability to process a coil of material with a laser system requires power, tracking and optical devices to meet the requirements of the maximum speed of the coil. The processes of conventional coil systems, such as that shown in US Patent No. 5,001,325, are characterized by their high speed, which could require a wide field of vision in the direction of the coil, to allow its tracking and This results in a greater focal length for the laser system. The greater the focal length requirements, the greater the power of the laser system must be in order to process the material. The present invention offers a process and a system in which imbricated sheets of material are passed through a section where the laser system can apply a treatment to the material. The source of the sheets can be a stack of sheets, or it can be the output of sheets of a coil system, or other loose material supply techniques. The imbricated material sheets reduce the apparent velocity of the material when it passes through the processing area of the laser system, in relation to the total speed of the coil, and in this way allows a smaller field of vision for that the laser system tracks and performs its function. When there is a high percentage of overlays, this results in a lower speed of the conveyor belt and decreases the overall requirements of the system. In addition, in the event that the reel length of the reel is too large compared to the length that needs to be processed (ie, 100 a), the amount of time that is spent processing can also be increased by the overlap , since the field of vision only needs to cover 1% of length, while in the case of the coil, in order to have an equivalent time to process, it is necessary to trace the entire repetition (100%). If the entire repetition is not followed, then the process time will be shorter (ie, 50% tracking = 1/2 of the time available for processing). These kinds of decompensation of the systems considerably affect the power of the laser as well as the scanning speed and the effective power density on the work surface. In this way, it can be seen that this technique allows one to considerably improve the efficiency of using the optimal advantages of the laser and its optical tracking system. As a result of the present invention, the power requirements of the laser system can be reduced. With the present invention, the lower power requirements allow the use of laser systems that were previously thought to be impractical for such laser treatment systems. Currently many C02 laser systems can be used in conjunction with state-of-the-art galvanometer systems that have limited power handling capabilities. The overlap allows the conveyor speed to be greatly reduced. The speed of the imbricated blanks that go over a conveyor can be reduced by a factor of 10 if an overlap of 90% is used, compared to the speed of the coil. For example, if a coil process running at 200 meters per minute is feeding an imbrication system that has a 90% overlap, the imbrication conveyor speed will be 20 meters per minute. This example assumes that the laser treatment that will be carried out will be carried out on 10% of the surface that is exposed. As the speed is reduced to 20 meters per minute in the nesting system, it travels 1/10 of the distance during the cutting cycle. In this way, the crawler distance of the galvanometer only needs to be 1/10 of what is needed in a continuous coil feed system. In turn, this allows the use of shorter focal lengths. A shorter focal length is important because it is directly proportional to the diameter of the focused scanning point. In this example, the focal length of the galvanometer is reduced by a factor of 10. This reduction in the diameter of the scanning point will have a great impact on the power densities achieved. Since the power density is related to the size area of the scanned point, any reduction in the diameter of the scanner point will increase the power density by the square of the change in diameter. The power requirements of the optical elements should be reduced accordingly. In addition, the optical path (ie the galvanometer, the optical elements and the mirrors) should only have this lower power requirement. The present invention can be used to provide lines of scratching or cutting in certain places of the containers, to provide something to the ease of handling thereof by the consumer. Such containers can easily be opened without using tools such as scissors or knives. These and other advantages will be obvious with the following detailed description of the invention, plus its drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS The various features and advantages of the present invention will be more readily understood with reference to the following detailed description, together with the accompanying drawings, in which like reference numerals designate similar structural elements, and in which: Figure 1 is a view schematic of an embodiment of the present invention; Figure 2A is a plan view of a stack of imbricated card material of the present invention; Figure 2B is a plan view of a continuous reel method for transporting cardboard material that is not yet cut; Figure 3 is a plan view of an embodiment of the paperboard processing system of the present invention; and Figure 4 is a schematic view of yet another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT (S) With reference to Figure 1, a laser cutting system of the present invention is generally shown at 10. A paperboard stack of material 12 can be fed to an imbrication transfer 14. This process can be implemented on any physical plane. Cartons can be nested 90 degrees to the right or left of the coil, or also in line with the coil. This allows selective exposure of all edges of the cardboard. Imbricator transferrs are well known in the art and can be purchased from Multifold International of Milford, Ohio. An example of an imbricator transferor sold by Multiford International is the Model 4026 TOTF (Top Dump Feeder). The interweaving transfer 14 can interlock each individual card of the stack in order to expose a portion of a surface of each carton and then transport the interleaved cartons to another stack 16. As the nested cartons 18 are passed through the interleaver 14, it can be direct a laser beam to the surface of individual cartons to cause local evaporation of material from the cartons. A laser system 20 can generate a laser beam and send it to a Z-axis approach 22. The laser beam is then moved through the two-axis laser galvanometer 24, which consists of mirrors with X and Y axis positioning. Figure 2A shows a plan view of a portion of imbricate cards 26. Each individual interlocked cardboard can expose a portion of its surface 28 when it is overlapped. Sensors may be used to detect the front edge of each carton 30 to activate the laser system. Each individual card only needs to expose a sufficient portion of area to allow the laser beam to contact the area to be treated with the laser beam as shown in 32. Figure 2B shows a plan view of the laser beam. a coil of material. A repeat print may also be used to activate the laser system so that it comes in contact with the area 32. In some systems the entire surface 28 of each repeat material is exposed, and then the entire surface must pass before any new piece of material can be started. In this case, you can see that the speed of the process would be the same (ie the number of cartons per minute), but that the process time will only be the same if the laser and the galvanometer system are allowed to track the repetition of the impression during all the elapsed time, which demands a greater field of vision, equal to the repetition of the impression. Referring now to Figure 3, it illustrates a plan view of an embodiment of a laser system 40 of the present invention. The material cartons of the system of Figure 3 can be constituted by several layers of different materials together forming each cardboard of material. Each cardboard can have an inner surface and a printed side. A spool of material can be supplied to the rotating blade 42, which cuts the reel of material into individual cartons. The cartons can then be separated by the divider wheels 44 and supplied to the conveyor 46. In this embodiment, the cartons are orthogonally imbricated with respect to the reel. The cartons can be brought into contact with the stopping plates 48 and pass through the staging plates 50 which place the cartons as they are being transported. In the embodiment shown, the cartons are shown with a printed side 52 facing upwards. A laser system 54 applies treatment to the cartons while a protection and ventilation system 56 functions. The cartons are then stacked and flipped at station 58, where they can be turned over so that their printed side 60 faces down. Alternatively, in Figure 4 an interlocking conveyor 100 can transport the cartons 102 under a laser system consisting of a laser 104 and a galvanometer 106 (plus a field flattening lens 108 in one embodiment, or a focusing lens). Z axis 109 in another embodiment). A tachometer 110 can be used to provide a speed input to a control system 112 that allows the processor to track the cutting surface. The control system 112 activates the laser and guides the laser beam through its desired configuration by controlling the placement of the mirrors of the galvanometer 106 in combination with the focus compensation of the Z axis. A front edge driver 120 detects the front edge of the laser. a cardboard and sends a signal to start the laser process. Upon receiving the signal, the control system 112 tracks the material through the tachometer signal 110 and initiates the laser process 104 and the positioning of the laser beam 106. The field flattening lens (or in another embodiment, the Z-axis focus) provides a means to allow the laser beam to remain focused over the entire field of view of the galvanometer's mirrors. Loose material sheets can be imbricated in a straight orientation, on the right or left side, from the loading point to the nesting conveyor. If a spool of material is cut into loose sheets before the loading point, the loose sheets can be turned 90 ° and then transported. This arrangement allows the different edges of each sheet to be exposed to the laser. The loose sheets can also be transported at any angle after the laser system, while the loose sheets are vertically inclined or tilted in any plane through a 360 ° rotation. The vertical arrangement (as well as other arrangements) allows even the overlap (overlap) of adjacent sheets and offers the same advantages as if the sheets are interwoven in a horizontal plane.

EXAMPLE In order to make the relevant aspects of the present invention more comprehensible, a brief example of the advantages that can be achieved with the present invention is set forth below. A hypothetical case has the following parameters: Coil Speed 200 meters per minute Repeat Printing .333 meters per part Processing capacity 600 parts per minute (200 meters per minute .333 meters per part) Total Cycle Time 100 milliseconds = .001667 minutes Cutting Time 90 milliseconds = .00150 minutes Galvanometer Replenishment Time 10 milliseconds = .000167 minutes Laser Cutting Area .033 m wide (across the coil, transversely) by .033 m length (coil direction) Maximum Angle of the Galvanometer plus or minus 15 degrees Laser power 200 wats Imbricator Conveyor Speed In this example, the reel is cut into blanks, which are transferred to an imbricator conveyor. The imbricated blanks would need to have an exposed area of .033 m (90% overlap). It can be shown that the resulting speed of the imbricator conveyor would be reduced by a factor of ten (10): Conveyor Speed = (surface exposed per parts per minute) = (0.033 m surface exposed per part) x (600 parts per min) 20m / min (depending on a speed of 200m / min of the coil). Field of View In order to maximize the cutting time in a continuous coil system, the laser system would track the part during the cutting time.

Coil Tracking Distance Coil Speed x Laser Cutting Time 200m / min x .0015 min = .3m In this way, the field of view of a continuous coil system would need to be .3m, while the work area is only .033m. Similarly, in an imbricator system the laser system would track the part during the cutting time. This can be demonstrated mathematically: Icing Tracking Distance Conveyor speed x laser cutting time 20m / min x .0015 min. = .03m The field of view of an imbricator system is reduced to .033m Focal Distance The focal length of a given field of view can be calculated as follows: Focal Distance = Field of View - 2 x Inv Tan 15 degrees The Focal Distance for the Focal Distance of the Coil System = .562m. The Focal Distance for the Imbrication System = .056m Therefore, the reduction of the focal distance in an imbricate system is a factor of 10.

Diameter of the Explorer Point The diameter of the scanner point is directly proportional to the focal distance, such comp shows in the following formula: Tip of the Diameter of the Explorer Point = 4L xf -í- px W (in microns) This relation can be analyzed with more detail in the text called "Bases of the Theory and Practice of Machining with Laser", author George Chryssolouris. Where: The Wavelength (L), in Microns, is 10.6 by laser C02. The Focal Distance (f), in Millimeters, is 567 for the Continuous Coil System and 56.7 for the imbricator system. The Beam Diameter (W), in Millimeters, is 30 for either of the two systems.

The respective Explorer Point Diameters are as follows: Diameter of the Explorer Point in the Coil System = 253 microns Diameter of the Imbricator System Scanner Point = 25 microns In this way, the imbricator system has a smaller scanner point because the distance focal is shorter. The total diameter of the focused scanner point is reduced by a factor of 10.

Power Density The power density of the imbricator system increases considerably over the power density of the continuous coil system: Power Density with the Coil System = Laser Power - Explorer Point area = .40MW / cm2 Power Density with the Imbricator System = Laser Power -r Explorer Point area = 40MW / cm2 The power density of the imbricator system is increased by a factor of 100 times.

END OF EXAMPLE The present invention has been described with reference to various embodiments and an example, but it should also be recognized that various modifications and variations to the invention may be made that fall within the scope of the appended claims.

Claims

WHAT IS REVINDED IS:

1. A process for treating laser material, said process consisting of: imbricating loose sheets of said material on a conveyor, such that each of said loose sheets of material is superimposed on a portion of one of said sheets of adjacent loose material; transporting each of said loose sheets in a previously determined path, so that they move continuously, said path being in the vision of a laser system; and directing a laser beam from said laser system to said loose sheets, one sheet at a time, in succession.

2. The process of claim 1, further comprising: providing a stack of loose sheets of material, previously cut, adjacent to said conveyor.

3. The process of claim 1, further comprising: providing a reel sheet feeder apparatus adjacent to said conveyor; providing cutting means related to such a sheet-fed sheet feeder to cut said coil into sheets of loose material.

4. The process of claim 1, further comprising: providing a detector of the front edge of the loose sheet to activate said laser system.

5. The process of claim 1, wherein a surface velocity measuring device provides data information to said laser system, which allows the tracking of said loose sheets during said transport.

6. The process of claim 1, wherein a relative tracking distance of said laser system substantially decreases when compared to the distance of a tracking of a laser system necessary for use in a conventional continuous coil system, when both are processed with the same speed of production capacity of material and both have the same time requirements with respect to laser treatment.

7. A system for dealing with laser sheets of loose material, consisting of: a conveyor to transport said loose sheets by a predetermined path; a laser positioned relative to said conveyor, for treating said loose sheets, wherein the focal length of said laser is considerably shorter than the focal length of a laser used in a conventional continuous coil system, when both are processed with the same speed of material production capacity and both have the same time requirements with respect to laser treatment.

8. The process of claim 6, wherein at least a 10% decrease in the apparent velocity of the sheets of loose material is obtained when said loose sheets pass through said laser system, in comparison with the actual speed of said material in a conventional coil system or as fed by non-nested pieces of raw material.

9. The process of claim 8, wherein the focal length of said laser system decreases by at least 10% while maintaining the same processing speed and material production capacity, and the same time requirements of the treatment with To be.

10. The process of claim 1, wherein said direction of said laser beam includes providing a X-Y beam director system of the galvanometer, with a fixed or dynamic compensation of the Z axis.

11. The process of claim 1, wherein said laser beam is directed to the bare surface of each of said loose sheets, said surface being uncovered the portion of each of said loose sheets that is not superimposed by an adjacent loose sheet.

12. A process for treating laser material, said process consisting of: imbricating loose sheets of said material on a conveyor, such that each of said sheets of loose material is superimposed on a portion of one of said sheets of adjacent loose material; transporting each of said loose sheets by a previously determined path, with continuous movement, said path being in the vision of a laser system; directing a laser beam from said laser system to said loose sheets, one sheet at a time, successively; providing a stack of pre-cut loose sheets of material adjacent to said conveyor, and providing a detector for the front edge of the loose sheets activating said laser system.