Patent Grant
8924002
This invention is related generally to the field of cutting of graphics areas or the like from sheets for various purposes, and other narrow-path processing about graphics areas on sheets and specifically to improving the speed and accuracy of such processing.
The technical field involving the cutting of graphic areas from sheets, or otherwise doing narrow-path processing about graphics images on sheets, includes, for example, the face-cutting of laminate sheets to form decals. More specifically, a graphic-image area on the face layer of a laminate needs to be cut away from the remainder of the face layer so that the graphic area (e.g., a decal) can subsequently be pulled away from the backing layer of the laminate and be applied elsewhere as intended. Extremely accurate face-layer cutting about the graphics is obviously highly desirable.
This is but one example in which highly accurate sheet cutting is desirable. In many other situations, highly accurate sheet cutting may not involve face-cutting, but through-cutting, in which the full thickness of the sheet is cut about a graphics area on the sheet. And in many situations, rather than highly accurate cutting, highly accurate scoring, creasing, line-embossing or the like is desired, and in each case, of course, such processing is along a line the varying direction of which is determined by the shape of the graphics area. Together, cutting and these other types of operations on sheets having one or more graphics areas thereon are referred to herein for convenience as “narrow-path processing.” For convenience, the prior art problems and the invention herein which solves such problems will be discussed primarily with reference to sheet-cutting methods and apparatus, but such discussion is not intended to limit the scope of the invention but merely to be exemplary.
Methods of cutting and associated apparatus which address many of the problems encountered in such processing of sheet material are part of the i-cut® vision cutting system from i-cut, Inc. (formerly Mikkelsen Graphic Engineering) of Lake Geneva, Wis., and are the subject of several patents, including for the U.S. Pat. Nos. 6,772,661, 6,619,167, 6,619,168, 6,672,187, 7,140,283 and 7,040,204. The invention described in U.S. Pat. No. 6,772,661 is a method and apparatus for achieving highly improved accuracy in cutting around graphics areas in order to fully compensate for all types of two-dimensional distortion in the sheets from which the graphics areas will be cut, including distortion of differing degrees in one dimension or along one direction on the sheet of material or distortion which varies non-uniformly across the sheet. The distortion may be from the printing process or from some other post-printing process such as material handling or during the cutting process itself. This invention also provides improved speed and accuracy in cutting or other narrow-path processing and greater efficiency of material usage.
The inventions described in U.S. Pat. Nos. 6,619,167, 6,619,168 and 6,672,187 relate to improvements in the cut-processing of sheets in flatbed plotters, including methods and apparatus to speed up processing and to automate the processing of multiple sheets. In particular, U.S. Pat. Nos. 6,619,168 and 6,672,187 include a search feature which enables the apparatus to search for the first two registration marks or other reference features (e.g., corners of the sheet, elements in a graphics area, or other objects for which a position can be unambiguously determined) if one or both of these registration marks or other reference features is not where it is expected to be on the work surface.
In some cases, such as in the i-cut® system, a flatbed plotter is used. These are devices having a position-controlled cutting implement above a flat work surface on which the sheet to be cut rests. The cutting implements are controlled with controller-supplied instructions and specific graphics data based on the X-Y coordinates necessary to achieve cutting along the intended path, such as about the perimeter of a graphics area.
Despite significant advances such as those in the i-cut® system, computer-controlled cutting and other processing of graphics sheets have not yet achieved the highest levels of efficiency and performance which potentially can be reached by such automated systems. Achieving greater speed, overall efficiencies and accurate performance in cutting or other forms of narrow-path processing are continuing challenges encountered with such systems. Increased efficiency of multiple-sheet processing would be achieved if the time to “read” a group of registration marks can be reduced while at the same time maintaining a desired level of accuracy. The present invention provides improvement in such processing by reducing the total time required to “read” (sense) registration marks.
It is an object of the present invention to provide an improved system for precision cutting or other narrow-path processing of graphics areas on sheets by addressing some of the problems and shortcomings of the prior art, including those referred to above.
Another object of the invention is to provide an improved system for precision cutting or other narrow-path processing of graphics areas on sheets which maintains accurate processing performance while reducing the total time for reading registration marks.
Another object of the invention is to provide an improved system for precision cutting or other narrow-path processing of graphics areas on sheets which enables a user to adjust the speed and accuracy of system operation.
Another object of the invention is to provide an improved system for precision cutting or other narrow-path processing of graphics areas on sheets which enables improvements in speed to be achieved during completely automated operation.
Still another object of the invention is to provide such a system which enables the user to trade off speed and accuracy in a single user setting.
Yet another object of the invention is to provide such a system which permits the user to pre-print a large number of registration marks at and about the graphics areas without such marks necessarily reducing processing time, while at the same time ensuring high processing accuracy with arbitrary sheet distortions.
And yet another object of the invention is to provide such a system the operation of which relieves the user of the task of determining where the best locations are for registration marks at and about the graphics areas to ensure accurate cutting.
How these and other objects are accomplished will become apparent from the following descriptions and the drawings.
The invention is an improved method and apparatus (for carrying out the method) for cutting graphics areas from a multiplicity of substantially-identical sheets having registration marks at predetermined positions at and about the graphics areas.
The inventive method includes (a) providing a plotter for sequentially receiving the sheets, (b) providing a sensor operatively connected to the plotter for moving over a work surface and configured to sense work-surface positions of registration marks on the sheets, (c) providing a cutter operatively connected to the sensor and movable to cut the graphics areas from a sheet in response to sensed registration-mark positions with respect to the work surface, and (d) providing a programmed controller operatively connecting the cutter to the sensor to control cutter movement. The improvement comprises: (1) sensing the work-surface positions of the registration marks of a sheet and calculating an expected work-surface position for each of such registration mark based on the work-surface positions of at least some of the other registration marks; (2) classifying each registration mark as active or inactive based on a first error criterion and applying the classification to corresponding marks of a subsequent sheet, the active marks being fewer than the total number of registration marks; (3) sensing the work-surface positions of the active registration marks of the subsequent sheet; and (4) cutting the graphics area(s) from the subsequent sheet based on the sensed positions of the active marks. The inventive method reduces the time for accurate cut-processing of the subsequent sheet.
The term “plotter” as used herein includes flatbed plotters in which a sheet to be processed is placed on a flat (two-dimensional) table surface. Such surface is referred to as the work surface or the sheet-receiving surface. The term “plotter” also includes apparatus having a cylindrical surface as its sheet-receiving and work surface. Such apparatus may process either roll-fed material or sheet material.
The term “registration marks” as used herein refers to printed marks at and about graphics areas. Registration marks may be pre-printed circles, filled or unfilled, of equal or unequal size. Registration marks may have a variety of different shapes and sizes, i.e., any shape and size which enables a sensor and controller to determine or read their locations (i.e., positions) on the work surface unambiguously. In circular form, registration marks typically may be about 3 to 12 mm in diameter. The color of registration marks is such as to create sufficient contrast to the background of a sheet containing graphics. The term “registration marks” includes holes through a sheet which can be sensed in the same way printed marks are sensed.
The sensor, cutter, and plotter are all operatively connected. “Operatively connected” as used herein does not imply merely direct connections between the two components said to be operatively connected (such connections may or may not be used), but means that there is functional connectivity such that information flows to and from the various components enabling these components to operate as described. In the present invention, the controller is configured to connect sensor, cutter and plotter as it controls the process being carried out within the inventive method.
Preferred embodiments of the inventive cutting method further include the steps of (i) calculating an expected work-surface position for an active registration mark of the subsequent sheet based on the work-surface positions of at least some of the active registration marks of the subsequent sheet, (ii) determining whether an active registration mark violates a second error criterion, and (iii) if a mark violates the second error criterion, determining whether the expected work-surface positions of any inactive registration marks are influenced by the violating mark and reclassifying the influenced inactive marks as active marks for a further subsequent sheet. Such preferred embodiments may also include repetitive steps of determining which registration marks are active for sheets to accurately and quickly cut-process the multiplicity of sheets.
In some preferred embodiments of the inventive cutting method, the first error criterion is a first threshold distance and the classifying includes (i) computing the distance between the expected and sensed work-surface positions of an active registration mark and (ii) comparing the computed distance for such mark with the first threshold distance. Such mark thereupon is classified as inactive if its computed distance is less than the first threshold distance.
In other preferred embodiments, the method further includes the step of adjusting the first error criterion threshold distance to select a desired accuracy and speed of cutting. In some of these embodiments, the second error criterion is a second threshold distance, and some embodiments include the step of adjusting the second error criterion threshold distance to select a desired accuracy and speed of cutting.
In highly-preferred embodiments of the inventive cutting method, the method further includes the step of randomly selecting one or more inactive registration marks and classifying them as active marks. The number of randomly-selected marks is a user-adjustable percentage of the inactive marks and the first threshold distance, the second threshold distance, and the user-adjustable percentage are simultaneously adjusted with a single user-setting.
The inventive method also applies to a method for narrow-path processing graphics areas on a multiplicity of substantially-identical sheets having registration marks at predetermined positions at and about the graphics areas in the same way as with cut-processing.
As mentioned above, the invention includes apparatus for carrying out the inventive method. The apparatus for cutting graphics areas from a multiplicity of substantially-identical sheets having registration marks at predetermined positions at and about the graphics areas includes (a) a plotter for sequentially receiving the sheets, (b) a sensor operatively connected to the plotter for moving over a work surface and configured to sense work-surface positions of registration marks of the sheets, (c) a cutter operatively connected to the sensor and movable to cut the graphics areas from a sheet in response to sensed registration-mark positions, and (d) a programmed controller operatively connecting the cutter to the sensor to control cutter movement. The apparatus is adapted to (a) sense the work-surface positions of the registration marks of a sheet and calculate an expected work-surface position for each such registration mark based on the work-surface positions of at least some of the other registration marks, (b) classify each registration mark as active or inactive based on a first error criterion and apply the classification to corresponding marks of a subsequent sheet, the active marks being fewer than the total number of registration marks, (c) sense the work-surface positions of the active registration marks of the subsequent sheet, and (d) cut the graphics area(s) from the subsequent sheet based on the sensed positions of the active marks. The inventive apparatus reduces the time for accurate cut-processing of the subsequent sheet.
Referring to
Cutting apparatus 10 includes two longitudinal guide rails 14 (one shown) mounted on the two sides of base 12 and a transverse member 18 suspended between longitudinal guide rails 14. Transverse member 18 is driven along guide rails 14 by a motor (not shown). A cutting tool 20, also driven by a motor (not shown), rides on transverse member 18. Cutting tool 20 has a cutting knife (not shown). Movement of cutting tool 20 over work surface is performed by transverse member 18 moving back and forth along guide rails 14 and cutting tool 20 moving back and forth along transverse member 18. Cutting tool 20 may have pressure- and tangential-controlled tungsten carbide blades or other blades that are generally known or lasers (all not shown). The cutter driver (not shown) which controls cutting tool 20 is standard and is known in the art.
A sensor 22 is shown attached to cutting tool 20, although it is not necessary for it to be attached cutting tool 20. Sensor 22 may be an optical detector, such as a CCD camera, which is known in the art, responsive to the registration marks 44 (see
Cutting apparatus 10 also includes a controller 50. Controller 50 may include a programmed computer or other programmable device which contains instructions for controlling the movement of cutting tool 20 in response to data from sensor 22 and information provided to controller 50 describing the graphics areas 42a-42d (see
Sensor 22 is connected to an input of controller 50 by cables 28 and 30. Controller 50 is also connected to and drives cutting tool 20. Controller 50 receives the inputted external data and compares it to the information which it has stored in it. For each graphics area 42a-42d, the information provided to controller 50 is the position of points along the cut paths (e.g., perimeter of the graphics area) relative to the positions of registration marks 44 as printed on sheet 40. Controller 50 may have the positions of registration marks 44 and the intended cutting path defined in X-Y coordinates.
Referring to
Controller 50 compares the actual distance between the three registration marks 44 which are closest to a point on the intended cutting path and adjusts the cutting path according to the changes between these registration marks 44 using the information of their positions on sheet 40 when the marks were printed. The cutting-path adjustments are made by making changes in the X-Y coordinates of points along the cutting path. In operation, sensor 22 is positioned over a registration mark 44. Sensor 22 and controller 50 find the mathematical center of a registration mark 44, and the X-Y coordinates of the mark center define the work-surface position of mark 44 in X-Y coordinates of work surface or sheet-receiving surface 16. Two other registration marks 44 are located, and their centers are defined by X-Y coordinates in like manner.
These data are inputted to controller 50, and controller 50 compares the actual work-surface positions of registration marks 44 on ready-to-be-cut sheet 40 to the positions of the registration marks in the predetermined cutting instructions provided to controller 50. The predetermined cutting path, which is a collection of X-Y coordinates, is adjusted according to the actual X-Y coordinates of registration marks 44. These comparisons are made interactively throughout the cutting process, making the process a dynamic process.
The cutting path is adjusted according to the actual coordinates of the three registration marks 44 closest to a cutting point. When the cutting of an individual graphics area is completed, cutting tool 20 is lifted and moved to the next graphics area and the process is repeated.
Duration operation, sheet 40 is placed on work surface 16 and may be held in place by a vacuum 60 which acts through work surface 16. The cutting of graphics areas 42a-42d is effected by movement of computer-controlled cutting tool 20 and computer-controlled transverse rail 18. The predetermined cutting instructions contained in controller 50 are based upon graphics areas 42a-42d which were originally printed on sheet 40. The cutting path is defined in X-Y coordinates.
Rectangular boxes generally indicate a functional element or functional block (these two terms are used herein interchangeably) which operates within cutting process 100, and generally, such functional elements operate on an input such as the position of one mark or a set of marks and produce output quantities as indicated. Diamond-shape boxes represent functional decision elements within the flow of process 100, each having possible results “Yes” and “No.” The decisions of a decision element having a reference number ddd are indicated by reference number dddY and dddN, for Yes and No decisions, respectively. Small circles containing uppercase letters indicate points within process 100 which connect with like circles (letters are the same). Thus, point C at the top of
The embodiment of process 100 of the inventive method begins in
In process 100, marks 44 are classified as either active or inactive. Active marks correspond to registration marks 44 which are read by apparatus 10 in order to process one sheet 40, and inactive marks correspond to registration marks 44 which are ignored (skipped; not read) by apparatus 10 as it processes one sheet 40. Notationally, the inactive set is referred to as Si, and Si contains n-m inactive marks where m is the number of active marks in Sa.
Returning to the function C(Sa) of element 104, C(Sa) creates two sets ep and Δp. ep represents the expected work-surface positions of the marks in Sa where each expected work-surface position ep(i) is determined based on all of the actual work-surface positions p except p(i). Δp represents a set of scalar distances between p(i) and ep(i) such that Δp(i)=|p(i)−ep(I)|.
At several stages in process 100, such as in functional element 104, an operation is carried out which includes determination of the expected work-surface position of a mark g based on the actual positions of a set of other marks F. An algorithm for this determination of expected work-surface position is presented here, using general notation for both marks and a set of marks as follows: For each mark f in F, two positions forg and fcur are known. forg(i) is the original position of the ith mark in the data which describes the positions of the pre-printed marks on sheet 40. This data is called the job file. An arbitrary origin for the coordinate system of this data can be chosen, such as 0,0 for the X,Y values of the origin of the job file. fcur(i) is the actual sensed work-surface position of the ith mark in F. Using this notation, one possible way to make this determination of expected work-surface mark position includes the following steps:
Referring again to
Process 100 then continues by processing (cutting the graphics area from) the first sheet 40 in functional block 112 and then reading the work-surface positions of active marks 44 on the next sheet 40 to be processed in functional block 116. At this point, in decision element 118, if there are no inactive marks (decision result 118Y), process 100 returns to functional element 104 to begin classifying marks based on the measurements made in functional element 116. Note that if all marks remain active as a multiplicity of sheets 40 are processed, process 100 continues as described above to process sheets 40. If there are inactive marks (Si is not empty; decision result 118N), process 100 proceeds to functional block 120 to calculate ep and Δp for the reduced set of active marks Sa.
Process 100 then continues with operations which determine whether an inactive mark should remain as inactive. In functional block 122, a mark p(i) is selected from the active set Sa, and its corresponding value Δp(i) is compared with a second error criterion threshold T2 in decision element 124. If Δp(i) is not greater than threshold T2 (decision result 124N), then process 100 continues by returning to select another mark in the active set Sa in block 122. If Δp(i) is greater than threshold T2 (decision result 124Y), then process 100 proceeds to determine if any inactive marks are influenced by the active mark p(i) and reclassifying any such influenced marks as active marks.
Functional elements 128 and 130 carry out operations similar to the function of block 104, with the following differences: Instead of determining an expected work-surface position for one mark in Sa based on the positions of all of the other marks in Sa, (a) C1(Sa) in functional block 128 determines the expected position eq(j) of an inactive mark q(j) in Si based on the positions of all of the active marks in Sa and (b) C1(S′a) in functional block 130 determines the expected position eq′(j) of an inactive mark q(j) in Si based on the positions of all of the active marks in S′a where, as indicated by the input to functional element 130, the work-surface position of active mark p(i) is replaced by the expected work-surface position ep(i) as determined in functional element 120. Note that the operations occurring in functional elements 128 and 130 do not proceed until both inputs to the functional blocks are provided; the operation of functional block 126 selects the jth registration mark in inactive set Si.
Expected positions eq(j) and eq′(j) are compared in decision block 132. If these two expected work-surface positions are equal (decision result 132Y), then it has been determined that inactive mark q(j) is not influenced by active mark p(i) which has violated the second error criterion in functional decision block 124 and process 100 continues by selecting another inactive mark q(j) in functional block 126 and proceeding with determining whether or not its expected work-surface position eq(j) is influenced by active mark p(I).
If in decision block 132 it is determined that inactive mark q(j) is influenced by active mark p(i) (decision result 132N), then the actual position of inactive mark q(j) is sensed by sensor 22 in functional block 134 and inactive mark q(j) becomes an active mark and is moved from set Si to set Sa in functional block 136.
Functional decision blocks 138 and 140 carry out similar loop control functions, directing the flow of process 100 such that all marks in inactive set Si are examined with respect to a specific active mark p(i) (decision block 138) and such that all marks in active set Sa are examined with respect to the second error criterion (decision element 140). If in either decision block 138 or 140, these two tasks are not complete, process 100 returns to point E (decision 138N) or functional block 122 to make another mark selection as appropriate and continue through the determinations as described above.
When these two loop control functions are both satisfied as indicated by decision 140Y in decision block 140, then decision element 142 determines at which point in process 100 to continue the processing of multiple sheets 40. If it is determined that no marks were moved from Si to Sa during the previous operations (decision result 142N), then process 100 continues operation at point D (see
Process 100, one embodiment of the inventive method, proceeds as described via apparatus 10 to rapidly and accurately cut (or otherwise narrow-path-process) a multiplicity of sheets 40. Functional element 114 in
The time saved in processing, while still ensuring accurate cutting performance, may be significant. Using a number of simplifying assumptions, the amount of time saved during processing may be estimated. Assume that (a) one thousand (1,000) substantially-identical sheets 40 (such as
It should also be noted that this invention enables a user to liberally print a large number of registration marks at and about graphics areas on a sheet without the time-penalty of processing extra marks since the inventive system reduces this time according to the current distortion. Further, the liberal application of registration marks ensures that all regions of distortion are found and compensated for without having to predict where the best mark locations should be.
Functional elements 109, 115 and 125 each represent that thresholds T1 and T2 and percentage T3 may be adjusted to select the desired speed and accuracy of the processing of multiple sheets on which graphics areas are being processed. Such adjustment may be made to the individual values of T1, T2 and T3 or simultaneously adjusted as illustrated in FIGS. 5 and 6A-6C.
Control 150 includes a slider bar 152 with an indicator 154 and a position scale 156 with seven individual scale marks 156M. Two of these scale marks 156M are end marks 156A and 156S indicating positions of processing maximum accuracy (156A) and processing maximum speed (156S). Values of parameters T1, T2 and T3 are set simultaneously by the user positioning indicator 154 along slider bar 152 at one of the seven preset positions corresponding to marks 156M.
T1 is a first threshold distance (first error criterion) which represents a distance below which a user is satisfied that the difference between the actual and expected work-surface positions of a mark indicate that is acceptable to ignore the sensing of the position of such mark until it is later determined that the distortion of sheet 40 has created the need to again sense the position of such mark. T2 is a second threshold distance (second error criterion) the value of which is selected to identify regions of larger distortion on sheet 40. Values for T1max may usefully be on the order of 225 microns. Values for T2max may usefully be on the order of 2,250 microns.
The function of the parameter T3 has been described above. Values for T3max may usefully be on the order of 25%.
It should be noted that although the registration marks and the graphics areas to be processed are normally printed on and processed from a single side of a sheet, systems (and methods they perform) which sense and process from an underside or from both sides with using marks (and/or through-holes which serve as marks) and graphics prepared accordingly are within the scope of this invention.
While the principles of the invention have been shown and described in connection with specific embodiments, it is to be understood that such embodiments are by way of example and are not limiting.
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| Number | Date | Country | |
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| 20120266728 A1 | Oct 2012 | US |
