IMPROVEMENTS RELATING TO THE CUTTING OF SHEET BLANKS

1,212,026. Cutting sheets and webs. GLAVERBEL. 12. Dec., 1967 [13 Dec., 1966], No. 56469/67. Heading G4A. [Also in Division C1] Materials in sheet or web form are cut into pieces of dimensions predetermined by an order book by cutting the sheet or web into sections along spaced lines and cutting the sections into required pieces a check being made before at least one section is cut that a suitable cutting plan for the following section can be devised having regard to any defects the sheet or web may contain, the cutting plan being so as to limit waste of material according to a predetermined criterion. The process is preferably performed under the control of a computer program and is of particular application to cutting sheets of glass according to three different specifications (e.g. for horticultured purposes, window panes and glass for mirrors respectively) from long webs of glass following its manufacture. Sheet metal, plastics wood and paper making applications are also referred to. The required pieces are preferably arranged, by the computer, into groups such that the aggregate width of the pieces in each group is less than or equal to the sheet or web width. The pieces within any one group are preferably of similar lengths. Individual pieces may feature in more than one group and in different orientations if the material is isotropic. Limitations may be imposed as to the number of pieces that may be cut from any one section or the number of cuts that may be made per The pieces to be cut may be arranged in an order of priority based on size (e.g. largest pieces first) and or on cost-to-area ratio where the cost (or marginal cost price) of each required piece is based upon experimental data about the unit cost of different sizes of sheet taking into account the different amounts of wastage for different size sheets in varying circumstances. Small pieces may be inclined with respect to the sides of the blank to avoid defects and so-called warehouse sheets may be cut if no suitable cutting plan appears to be possible. The blank may be marked manually with colours (a 3- colour classification is described) to denote the type and location of any defects. The marks may then be detected photo-electrically to feed this information automatically into the computer. Alternatively, the information may be fed in manually. The computer may produce a number of alternative plans for cutting and select the most economic. The cutting tool may be directly controlled by