NO830090L - PROCEDURE FOR CUTTING PIECES OF A PLATE OR SHEET-SHAPED MATERIAL - Google Patents

Description

The invention relates to a method for processing a collection of pieces in an optimal way from animal skins that have various local defects, which pieces that are cut into these skins are destined to be put together to form a finished object.

The invention can primarily be used in the manufacture of footwear; although it is not necessarily limited to this area, but it is nevertheless this area of application that it'

is referred to below, in order to give a concrete explanation of the implementation of the method which is the subject of this invention.

One of the special conditions that occurs when processing different pieces of genuine leather that are cut into hides,

is that these inevitably exhibit varying and local defects whose location and extent differ from one hiid to another

another. For this reason, it is not possible to lay the skins on top of each other to create a multi-layered stack that could be cut in a single operation as is known and commonly practiced

in other areas, such as when making garments. It is necessary to treat each skin individually in order to seek to make the greatest possible number of pieces while avoiding the defects.

Until now, it has been considered logical and rational to proceed in the following way: Each skin is taken separately and the contours of the various pieces, which have varying shapes and dimensions, are placed manually, excluding the defects, in order to make the best possible use of the applicable surface of the skin. Usually, the placement is not done with the help of drawing models, but directly with the help of cutting or hole tools so that the placement and the cutting become two operations that are practically carried out simultaneously. When it is necessary to process a large number of skins in order to achieve the desired quantity of the various pieces to be used, the number of piercing tools itself is high, and furthermore the optimal utilization of a skin requires a large number of assembly and disassembly operations on a press, for hole tools that are used successively in. dependency

of possibilities for their location on the usable surface of a skin outside the defects. The production costs for

■ a large number of hole tools and the capital tied up in the tool holding adds up to a significant value. ■ It should also be noted that cutting to size using a hole tool makes it necessary to leave a gap of a few millimeters between two pieces, because the tangent of the contour of two neighboring pieces does not allow the production of two pieces that are correctly cut to size in the area of the point of tangency. The result of this is in each skin a loss of material which is not negligible when you take into account the high price of . genuine leather .-The main purpose of the invention is to provide a new method for placing and cutting pieces of genuine leather from animal skins which. treated individually, which makes it unnecessary to use the aforementioned hole tools and which also enables improved economy with regard to leather thanks to a closer placement of the pieces on a given hide. According to the invention, one proceeds in the following way': Models are produced which each represent the contour of a specific piece and each model is identified by placing a code on it which can be read by per se known reading devices.

In a computer memory, the code for the models is entered and

the definition of their outline.

Starting from a skin from which the largest possible number of pieces are to be created, models are placed manually on the skin while avoiding defects.

With the help of a known in and of itself, so-called digitization table, the position of the models on the skin is determined by means of markings placed on each model, and the said position is recorded in the computer memory in connection with an individual marking that is used for that person.skin.

After this operation, one could immediately move on to cutting the skin, but according to one aspect of the invention, it is preferred to retain the marked skin and not cut it until later, when there is a need for the pieces that are been placed on this.

Regardless of whether one or the other of these two methods is used, the skin is cut by means of a laser known per se, whose function is controlled by the computer in whose memory the location of the models on this skin and the definition of the contour of these models, on has been registered in advance, as mentioned above.

Application of a laser as a cutting device for real leather does not present any particular difficulty, apart from the regulation of the working conditions, but this regulation is within the competence of a professional. It is therefore not necessary to give a detailed description of this operation. The laser is perfectly suited for controlling the trimming of wood

with the help of a computer, due to the laser's ability to accurately follow the most complicated contours. The cut in leather becomes completely clean and, moreover, the contours can lie very close to each other, namely so close to each other that they are tangents,

without the accuracy of the contour of the cut pieces suffering

below this. Furthermore, a laser is suitable for each piece to carry out complementary operations which are mostly impossible to realize with conventional means for cutting, such as e.g. creation of incisions or slits or pre-cut parts or possibly marking of seam lines. which the side is to be sewn.

In the embodiment of the method according to the invention that has just been described, several improvements can be made. Instead of making the placement on the skin using real-size models, the placement can be done by optical projection of their image on the skin. In this case, the models or, more specifically, the drawings or curves that make them up, do not need to be realized in real dimensions. They may be reduced in scale and their depiction may be magnified during staging.

An advantage of the method according to the invention is that it becomes easy and quick to move from a collection of pieces that are part of a first specified object to collections of pieces that make up objects derived from the first object, as the computer is -suitable to make this transposition when the contours of the pieces of the first object,- have been introduced into it.

According to a further development of the invention, a general contour of skins is defined to form a normalized contour whose data is entered into the computer's memory. Based on each individual skin that has this general normalized contour, defects, such as this one, are then marked on each of these

exhibits, and the computer is allowed to carry out the placement using ehi "and per se" known optimization method.

The coding of the models and the definition of their outline can be carried out by appropriate means. According to the invention, it is preferred to use ehstrek-kbde (code to be barred) to identify the different models and their outline and

furthermore, to mark on each model two points A and B which can be easily detected by automatic, optical reading devices. These points have a specific mutual distance that is specific to each model depending on its contour. It will be understood that this marking can also be carried out by means of magnetic marks which are suitable for being read by means of electromagnetic means.

The method according to the invention is. specially developed for the treatment of hides of genuine leather or leather which is a material that can be described as heterogeneous due to the presence of variable defects and areas of different qualities. However, it is clear that the invention can also be used for cutting homogeneous materials in sheet or roll form. In this case, the location does not need to avoid unexpected or accidental defects. The placement can thus be made directly on each plate using models with. reduced 'painting' stick which is projected optically.

Another further development can also be carried out with the method according to the invention, whether it is applied to genuine leather or leather or to a homogeneous material. When the type and location of models placed on a surface - with a view to cutting pieces - is entered into memory, when this cutting has been carried out, it is advantageous to use automatic devices or at least semi-automatic devices for grasping, -carrying and arrange the cut pieces'. These devices are controlled by the computer and 'make the arrangement of the pieces according to a predetermined' classification, depending on data relating to the corresponding models, which data. has been read into memory.