Patent GB-1212027-A (GB)
Title: Improvements relating to the cutting of sheet blanks
Inventor: VALEMBOIS JEAN
IPC: G06Q10/00
Filed: 1967-12-12
Abstract: 1,212,027. Cutting sheets and webs. GLAVERBEL. 12 Dec., 1967 [13 Dec., 1966], No; 56470/67. Heading G4A. [Also in Division C1] . Material in sheet or web form is cut into rectangular pieces of various sizes selected from an order book of required pieces by cutting the whole or part of a " blank " area along straight lines according to a cutting plan which takes account of any defect present and is developed by an iterative process from a first arbitrary plan to a more developed plan which is characterized in that the aggregate of values of pieces in this plan, assessed according to a predetermined criterion, will be optimum, or approximately so. The first plan may be devised by selecting a required piece of large area and value (compatible with the locations V 1 , V 2  and V 3  of defects) and placing it as shown at D a b c in Fig. 5A in a corner of the blank ABCD. Removal of this piece would involve a cut d c (defined as a first rank cut) and a cut a b (defined as a second rank cut). The order book is then scanned to find a further piece of a large area and value as.possible which, is compatible with the dimensions of the resulting remainder A d b a and with the dimensions of any defects. Preferably, the selected piece has one dimension common with said remainder. This process is continued until a remainder A g l k smaller than the smallest required piece is obtained. This first plan is then modified in that starting with the piece of highest rank (the rank of a piece is equal to the rank of the highest rank cut associated therewith) alternative plans are determined on the basis that each of the pieces in the first plan are removed in turn. The aggregates of the values in each case are determined and only that plan having the highest value according to a predetermined criterion is retained. The final plan adopted for the complete blank may be as shown in Fig. 5C, it being noted that defects V 1  and V2 are avoided whereas defect V 3  is included in a piece which required a lower specification. The pieces in the adopted plan are removed from the order book. The values associated with the pieces in the order book may be based on experimental data about the unit costs of different sizes of sheet taking into account the different accounts of wastage for varying sizes of pieces in varying circumstances. The values may be revised periodically. The process is preferably controlled by a computer. The computer may be programmed to select that plan which involves the maximum aggregate value to area used ratio or which produces the largest member of pieces of the same dimensions or involves the minimum number of cutting lines or which makes optimum use of the area of the blank. The pieces in the order book are preferably arranged in order of values or in order of values within size groupings. Whenever a piece is removed from a plan referred to above, a piece from the next smaller size group is then selected. Limits may be imposed as to the number of cuts that may be made or the time that may be devoted to considering the different possible plans. Pieces may be oriented in different ways to avoid defects if the material is isotropic. The defects may be detected manually or photo-electrically and the co-ordinates fed to the computer. They may also be classified. The cutting plan may be such that all pieces arriving at a delivery point during a given time are destined for adjacent handling units such as boxes. New required pieces may be added to the order book during processing. Pieces required urgently may have their cost values artificially inflated. In a plan covering a plurality of sections (separated by rank 1 cuts), the first section may be cut according to the plan and the rest of the plan abandoned and a new plan for the remaining sheet material then being devised. The computer may perform simulation runs assuming a random distribution of defects (e.g. to establish the order of boxes required on the packing lines) and may process imaginary order books and blanks. The computer may control a cutting tool directly or may provide a tracing or print-out of the adopted plan. The cutting may be controlled off-line by way of magnetic or punched tape or film from which an image may be projected on to the blank. The material to be cut may comprise glass, metal, wood, plastics or paper. The program may be coded into punched cards, punched tape or magnetic tape. A suitable program in flow-chart form is disclosed.