Automatic operations on materials

Details Automatic operations on materials Automatic operations on materials

1995-03-16

1999-03-23

Evans, Geoffrey S.

Electric heating

Metal heating

By arc

21912183, 36447005, 36447409, B23K 2600

Patent

active

058863192

DESCRIPTION:

BRIEF SUMMARY
This invention relates to automatic operations on materials and inter alia to carrying out high speed operations particularly but by no means exclusively cutting operations on materials especially lace.
Lace is made in wide e.g. 5 m widths from which narrower widths are cut usually along more or less deeply scalloped figuring. Mechanical arrangements exist capable of cutting relatively shallowly scalloped edges at reasonable speeds but require time-consuming setting up and constant operator attention. For the more intricate designs and deeper scalloping, it is possible to cut only by hand, which adds very considerably to the cost of the finished product.
It is, of course, known that lasers will cut materials and it is natural to contemplate the use of lasers for cutting lace. There are, however, some considerable problems involved in tracking a laser spot along the precisely required line of cut, not least because of the fact that lace is a flexible and easily distortable fabric which may well have faults which add to the problem of knowing where to cut. Moreover, the act of cutting--because the cut threads are under tension--necessarily brings about its own distortions.
Various proposals have been made for using machine vision to guide an operation effector such as a laser spot or a hot wire along a path such as a lace cutting path. I. Kimoto et al, "Automation of Sealant Painting and Lace Cutting Using Pattern Tracking Techniques", The International Journal of Advanced Manufacturing Technology, 1 (4) 101-107, 1986 discloses the use of a photo-sensor array to detect the flange pattern of a crankcase while it is on a moving conveyor and a micro-computer to deliver appropriate pre-recorded commands after processing input signals from the array and conveyor speed sensors to deposit liquid sealant on the flange with nozzles installed behind the sensing devices. For lace cutting, a CCD camera is mounted with a laser cutter on an X-Y traversing mechanism above the travelling lace, which is enhanced to eliminate dot ambiguities and generate a clear pattern. The curved contours of figuring on the lace can thus be clearly discriminated, and "followed" by the traversing mechanism. Pattern recognition speed for lace cutting depends on the lace pattern, but for simple patterns, cutting speeds as high as 100 mm/s are promised.
U.S. Pat. No. 4,907,169 also discloses an adaptive tracking vision and guidance system with a vision system and a robot end effector mounted on a moving platform controlled to follow a path approximating the actual path of the feature being tracked, the end effector being further controlled in real time to follow the path even though the platform might deviate therefrom.
DE-OS-40 26 250 discloses cutting lace by a CNC controlled cutting head traversing, with a camera, a travelling lace path, following a line thereon such as the edge between the lace and a connecting web between two lace sections.
A disadvantage of all such systems is that the pattern recognition algorithms are relatively slow in operation; more complicated patterns can be cut only relatively slowly as compared to simple patterns, which, in the case of lace, can be cut quite quickly in any event using conventional equipment. Moreover, some lace patterns may not have a clearly defined tracking feature, and the same will be true to a greater extent with other materials, where, indeed, a feature may be or appear to be bifurcated, creating a dilemma for the control system.
The present invention provides new methods of dealing with aspects of the problem of cutting lace that are of general application to cutting, marking or effecting other operations on other textile fabrics or indeed on materials generally.
The invention, in one aspect, comprises a method for guiding an operation effector to effect an operation along a path on a patterned material using machine vision, characterised in that machine vision is used to make a map of a repeat of the pattern, a path is defined on the map, the material and operation effector are moved rela

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