Method and apparatus for cutting sheet material with preprocessed data

A method of cutting pattern pieces from sheet material with a cutting blade and preprocessed marker data defining the pattern pieces in a closely packed array comprising:

• reducing the pattern pieces in the marker array to machine readable data defining the shapes and positioning of the patteren pieces in the array in terms of rectangular coordinates;
• preprocessing the machine readable data by comparing the data of one pattern piece with another in a data processor to determine the separation between the pieces in the array, and identifying in the data processor critical segments of a cutting path for a pattern piece which segments are located closer to an adjacent pattern piece than a predetermined amount, the step of identifying including defining rectangular windows around adjacent pattern pieces by means of the maximum and minimum coordinates along each coordinate axis, and examining the distance between the pattern pieces along those segments of the cutting paths falling within any area of a rectangular window overlapping an adjacent window;
• generating basic command signals from the machine readable data for guiding the cutting blade along cutting paths defined by the shapes and positioning of the pattern pieces in the array;
• generating remedial command signals for guiding the cutting blade past the identified critical segments;
• and
• cutting the pattern pieces from the sheet material by guiding the cutting blade along cutting paths defined by the shapes and positioning of the pattern pieces with the basic and remedial command signals.

A method of preprocessing data defining a marker of pattern pieces to be cut from a layup of sheet material with an automatically controlled knife blade comprising the steps of:

• reading data defining the marker of pattern pieces into a data processor with the periphery of each pattern piece and the positioning of the pieces within the marker fully defined by the data;
• comparing the data of each pattern piece with the data of each other pattern piece in the processor to identify critical segments of the pattern peripheries lying closer to adjacent pattern pieces than a predetermined minimum separation distance;
• and
• selectively modifying the marker data defining the pattern pieces by calculating from the data identified as a critical segment new data defining a cutting path for the blade offset from the identified critical segment and away from a closely adjacent pattern piece to establish a separation not less than the predetermined minimum.