EP1098722B1 - Bending machine with improved precision - Google Patents

Abstract

A numerical control device for a bending machine includes a keyboard, a memory and a processor. The memory stores one or more groups of data, each containing bending conditions, a bend angle and at least one penetration depth. The memory further stores program instructions for searching whether data input with the keyboard is stored in the memory, in a same group of data, and that sends a signal to the bending machine so that the bending machine peforms bending according to the penetration depth included in the group of data. The processor that executes said program instructions.

Description

Technical field and prior art

The invention relates to a press brake used in particularly for folding metal sheets.

An example of a press brake as known in the art is shown schematically in Figures 1 and 2.

It includes an upper deck 1 arranged above a lower deck 2. The latter is fixed, bearing at its ends, while the upper deck 1 is movable, and actuated in a plane vertical by drive members also located at its two ends.

Drives provide strength necessary for folding metal sheets or sheets.

More specifically, the decks 1, 2 are mounted in a frame formed by two flanges 9a and 9b joined together in particular by a bracing beam (not shown).

The upper 1 and lower 2 aprons are contained in the same vertical plane and the upper apron slides relative to the flanges 9a and 9b using guide means 8a and 8b formed for example by two hydraulic cylinders.

The working edges of these two upper aprons and lower respectively carry a folding punch P and a corresponding matrix M.

As can be seen in Figure 2, the lower part 4 of the lower deck 2 is fixed by welding or by any other means to its ends to the flanges 9a and 9b forming the press frame folder.

Figure 3 shows a sheet 10 placed on the matrix M in which a "V" is made which will allow folding. In the axis of the "V" and at the end point 12 of the punch P, a force F is exerted to flex the sheet.

The bending angle of a metal sheet or sheet depends the importance of the penetration of the punch P inside the matrix M.

A press brake can, in general, perform three types folding.

The relative movement of the punch can be stopped at stage shown in Figure 4. This is a first type of folding, known as "folding in the air in 3 points".

This type of folding is obtained by limiting the travel of the apron 1 when adjusting the machine.

• le rayon Ri de la tôle, ou plaque, 10, intérieur à la zone pliée, est en général égal ou légèrement supérieur à l'épaisseur de la tôle,
• lorsqu'on annule la pression du poinçon, il se produit une réouverture du pli, due à l'élasticité résiduelle de la tôle 10.

If, on the contrary, the penetration is increased, the sheet 10 descends in the "V" to a limit defined by the bottom of the V (FIG. 5). This is the technique known as the "semi" This technique also has the following characteristics:

• the radius Ri of the sheet, or plate, 10, inside the folded zone, is generally equal to or slightly greater than the thickness of the sheet,
• when the punch pressure is canceled, the fold is reopened, due to the residual elasticity of the sheet 10.

• le rayon intérieur Ri est inférieur à l'épaisseur de la tôle ; il est conditionné par le rayon du poinçon,
• l'angle du pli est égal à celui du "V" de la matrice M et du poinçon, l'élasticité de la tôle ayant disparue.

Finally, if the force is increased again, the point 12 enters the sheet 10 and "matrix" the bending radius (Figure 5). This is called "striking" folding which has the following particularities:

• the internal radius Ri is less than the thickness of the sheet; it is conditioned by the radius of the punch,
• the angle of the fold is equal to that of the "V" of the matrix M and of the punch, the elasticity of the sheet having disappeared.

In the case of 3-point folding in the air, the sides of the fold, the punch and the die never being in contact with each other, the shape of the matrix is of little importance. It can also be a U.

In comparison with the folds at the bottom of "V" and in strikes, bending in the air requires the least amount of force, and the metal remains very elastic.

These elements make this form of folding the most sensitive to angular deviations and requires special attention to the execution.

In particular, in a "3-point" fold, the experience proves that a mechanical deviation of 1/10 mm, noted for example between 2 tip elements 12 of two punches, has for consequence an angular variation of 2 ° in a bending of sheet metal 2 mm executed in a V of 12 (6 times the thickness).

In general, and always in the case of a folding "3 points", a choice of a width corresponding to 8 to 12 times the thickness of the sheet 10 to be folded allows the production of folds partial with a tolerance of ± 1 °.

This is the optimal precision obtained with folding in the air.

A method to help with folding with optimal precision is to use a protractor 16, mounted as illustrated in FIG. 6: the sheet 10 can rest on branch 18 of the protractor, itself mounted on the matrix M.

When the edge of the sheet 10 is parallel to the branch of the protractor, pressure on the punch is minimized to using power adjustment, to allow the sheet to release elastic bending stress. The angle A of this elasticity is appreciated in relation to the desired angle indicated by the reporter.

The pressure is then increased so that increase the bending depth of the elasticity angle, appreciated above (angle A).

The technique of "semi-striking" is also back elastic sheet. Therefore, we choose for example a corner tool at the top 88 ° for 90 ° folding. This angle of 88 ° can be reduced to 85 ° for thick sheets.

Folding precision, under optimal conditions, achieves a tolerance of ± 30 minutes of angle.

The bending in striking is that which achieves the highest angular precision, the elasticity of the sheet being canceled. But this type of folding requires being able to increase, during the ^2nd phase of folding, the force applied to the punch, in order to bring the edges of sheet metal to the sides of the V of the die. The tool angle is then the desired folding angle. The tools used must therefore be very precise to, in turn, form the sheet to their own characteristics.

The angular precision obtained with this type of folding may be at best 15 minutes of angle.

Therefore, it appears that the question of accuracy of a press brake is a critical problem, which is difficult to resolve in most cases.

Furthermore, bending precision is all the more difficult to obtain that the thickness of the sheet 10 is thin.

For a heavy plate unlike a thin sheet, the imperfections become negligible compared to penetration unit for 1 °.

There are also numerically controlled presses, in which an operator enters a desired angle. The command then calculates the penetration and force required to obtain the desired angle. The calculation is made using a formula, known or developed by the user.

But, this formula can only be an approximation of reality and is not generally applicable in all cases or in different types of folding, or does not have the same precision in all cases or in the different types of folding.

There is the problem of making the folding machines more precise.

In particular, the problem arises of obtaining a calculation more precise, or a more precise assessment or indication, of the folding penetration.

Document JP-60 - 247,415 describes a press brake provided with means for measuring distances between a lower tool and a superior tool, and a calculating means for calculating an angle of effective folding of a part according to distance measurements performed. The effective folding angle is compared with the angle of bending to be achieved, and a correction of the lowering of the tool is determined. A memory stores information concerning the relationship between the effective and target bending angles and the angles of bending and the level of descent of the tool.

The device described in this document involves a step of calculating the effective angle, from measured distances, and determines a correction on the descent of the tool based on these distances measured.

The precision obtained with this type of device is not satisfactory. Indeed, the calculation made during the calculation step is necessarily limited in its precision and validity.

In addition, this method does not distinguish according to the different types of folding performed. Now an angle calculated for a distance measured and for a given type of bending is not necessarily valid, or does not necessarily have the same type precision, for another type of folding.

WO 99/14641 describes a folding process using a neural network.

Document US Pat. No. 5,497,647 describes a device for correct angle errors due to offsets between the flanges side of the folding machine.

Document DE-3,441 13 describes a device in which angle data is entered into the numerical control, a folding is carried out, then a measurement of the angle obtained is carried out. This measurement is compared to the desired angle value.

The document (US-4 430 879) also describes a device with bending angle measurement in real time, during the folding, until the desired angle is obtained. Once a certain folding performed, the angle obtained is compared with the desired angle, and a new folding is performed, if the difference between the two values of angles is too important.

The document (US-4,864,509) also describes a process in which calculation steps 108, 110 are implemented, from stored angle and geometric data.

Statement of the invention

• des moyens pour introduire en tant que données d'entrée un angle de pliage souhaité et des conditions ou critères de pliage,
• des moyens pour mémoriser un ou plusieurs groupes de données comportant chacun des conditions d'utilisation ou de pliage, un angle de pliage et au moins une profondeur de pénétration,
• des moyens pour rechercher si les données d'entrée sont mémorisées dans les moyens de mémorisation, dans un même groupe de données, et
• des moyens pour émettre un signal représentatif de la profondeur de pénétration incluse dans ledit même groupe de données, ou pour émettre un signal de commande de la machine plieuse selon cette profondeur de pénétration.

The invention firstly relates to a digital control system for a folding machine, comprising:

• means for entering as input data a desired folding angle and folding conditions or criteria,
• means for storing one or more groups of data each comprising conditions of use or folding, a folding angle and at least one penetration depth,
• means for checking whether the input data are stored in the storage means, in the same group of data, and
• means for transmitting a signal representative of the penetration depth included in said same group of data, or for transmitting a control signal from the folding machine according to this penetration depth.

So when bending conditions and an angle desired, indicated by an operator, exist in the database data, the control device or system returns the value of penetration, stored in the storage means, which corresponds to these folding conditions and desired angle.

It is therefore possible to fold according to operating conditions implemented, hence improved precision folding.

The value of the penetration depth does not depend no longer just a single variable such as the distance between lower and upper parts of the press.

The device is particularly interesting for three-point folds in the air or V-folds in the air (semi-striking technique). It is indeed in these modes of bends that the precision problems arise with the most acute.

According to a particular embodiment, the device order can also include means to find out if two groups of data exist in the storage means having the same folding conditions as those introduced by the insertion means, and respective folding angles between which the desired angle is understood, and to calculate a penetration depth as a function of the depths of penetration belonging respectively to the two groups of data.

The calculation of the penetration depth can consist for example in an interpolation of penetration depths contained in the two data groups.

In case the desired conditions are not in the storage means and / or when the two groups of aforementioned folding data cannot be found, it is possible perform a penetration depth calculation according to a formula predetermined and preprogrammed.

Advantageously, means can make it possible to modify, in the storage means, at least one parameter among the folding conditions, the folding angles and the penetration depths.

Thus, the operator is not limited to the stored values in the storage means.

Preferably, means are also provided for perform a comparison of a measured bending angle and the angle desired fold, and means for correcting the depth of penetration if it results from the comparison that the angle measured is different from the desired angle.

Preferably also, means make it possible to update data in the storage means in depending on the result of the penetration depth correction. Other means can be provided for writing in the means of storage an additional group of data, comprising input data and corrected penetration depth. These last means are used when the input data was not not already present in the same data group stored in the means of memorization.

The device according to the invention thus has a base of scalable, or dynamic, data that provides precision increased as it is used.

It is thus possible to evolve the data collected according to the experiments carried out or the machine operation. None of the known machines day does not allow such an evolution. The precision of the machine is is found to increase as it is used: the more it is used, the more it encounters various situations (which, statistically, cannot fail to happen), and more many situations can be memorized in the database.

The invention also relates to a press system folder comprising a control system as described above.

• mémoriser dans des moyens de mémorisation un ou plusieurs groupes de données comportant chacun des conditions de pliage, un angle de pliage et au moins une profondeur de pénétration,
• recevoir, en tant que données d'entrée, un angle de pliage souhaité et des conditions ou critères de pliage,
• rechercher si les données d'entrée sont mémorisées dans les moyens de mémorisation, dans un même groupe de données, et
• émettre un signal représentatif de la profondeur de pénétration contenue dans ledit même groupe de données, ou un signal de commande de la machine selon cette profondeur de pénétration.

The invention also relates to a method of numerically controlling a folding machine comprising the following steps:

• memorize in storage means one or more groups of data each comprising folding conditions, a folding angle and at least one penetration depth,
• receive, as input data, a desired folding angle and folding conditions or criteria,
• find out whether the input data are stored in the storage means, in the same group of data, and
• send a signal representative of the penetration depth contained in said same data group, or a machine control signal according to this penetration depth.

This process has the same advantages as those described above in conjunction with the control system digital according to the invention.

Brief description of the figures

• la figure 1 représente une vue schématique d'une presse plieuse selon l'art antérieur, avec des organes de déplacement,
• la figure 2 représente une vue en coupe verticale selon la ligne II-II de la figure 1,
• les figures 3 à 5 représentent différents types de pliage,
• la figure 6 représente une presse équipée d'un rapporteur d'angle,
• la figure 7A représente schématiquement un système de presse plieuse selon l'invention,
• la figure 7B représente des modes de fonctionnement du système de presse plieuse selon l'invention,
• les figures 8A à 8C représentent un détail respectivement d'une matrice, d'un poinçon et d'un pli,
• la figure 8D représente une position décalée d'une pièce à plier par rapport au centre d'une presse plieuse,
• la figure 9 représente un organigramme d'un mode programmation exécuté par le système de presse plieuse selon l'invention,
• la figure 10 représente schématiquement un rapporteur d'angle numérique compris dans le système de presse plieuse selon l'invention,
• la figure 11 représente schématiquement un circuit d'un rapporteur d'angle numérique selon la figure 10,
• la figure 12 représente un organigramme d'un mode correction automatique exécuté par le système de presse plieuse selon l'invention,
• la figure 13 représente un organigramme d'un mode contrôle qualité exécuté par le système de presse plieuse selon l'invention,
• la figure 14 représente un organigramme d'un mode visualisation exécuté par le système de presse plieuse selon l'invention,
• la figure 15 représente un affichage obtenu lors du déroulement du mode correction automatique,
• la figure 16 représente un affichage obtenu lors du déroulement du mode contrôle qualité, et
• la figure 17 représente un affichage obtenu lors du déroulement du mode visualisation.

The characteristics and advantages of the invention will appear better in the light of the description which follows. This description relates to the exemplary embodiments, given by way of explanation and without limitation, with reference to the appended drawings in which:

• FIG. 1 represents a schematic view of a press brake according to the prior art, with displacement members,
• FIG. 2 represents a view in vertical section along the line II-II of FIG. 1,
• FIGS. 3 to 5 represent different types of folding,
• FIG. 6 represents a press equipped with a angle protractor,
• FIG. 7A schematically represents a press brake system according to the invention,
• FIG. 7B shows operating modes of the press brake system according to the invention,
• FIGS. 8A to 8C represent a detail respectively of a die, a punch and a fold,
• FIG. 8D represents an offset position of a piece to be folded relative to the center of a press brake,
• FIG. 9 represents a flowchart of a programming mode executed by the press brake system according to the invention,
• FIG. 10 schematically represents a digital angle protector included in the press brake system according to the invention,
• FIG. 11 schematically represents a circuit of a digital protractor according to FIG. 10,
• FIG. 12 represents a flowchart of an automatic correction mode executed by the press brake system according to the invention,
• FIG. 13 represents a flowchart of a quality control mode executed by the press brake system according to the invention,
• FIG. 14 represents a flowchart of a display mode executed by the press brake system according to the invention,
• FIG. 15 represents a display obtained during the automatic correction mode,
• FIG. 16 represents a display obtained during the quality control mode, and
• FIG. 17 represents a display obtained during the display mode.

Detailed description of embodiments of the invention

FIG. 7A schematically represents a system of press brake 20 implementing a method according to the invention. This system comprises two upper and lower aprons 1, 2, of the type of those described above in relation to Figures 1 and 2, a digital control system 22 which controls cylinders hydraulic 8a, 8b for moving the deck 1 relative to apron 2, and a digital protractor 21 used to measure angles obtained after folding.

A terminal comprising a PC-type microcomputer, a display screen 25 and a keyboard 27 can also be connected to the digital control device 22 by a link wired, for example RS232 type. This terminal allows to execute bending simulation programs.

The digital control system 22 includes a display screen 24 and a keyboard 26 allowing an operator to enter data or indications relating to an angle at reach and / or folding or use conditions such as explained below in more detail. It also includes a processor 32, which in particular implements algorithms for calculation and management of the numerical control which will be described further on, an interface 30 used to read digital data transmitted by the digital reporter 21 via a cable 21a, and storage means, or memory area, 34.

• un ensemble de conditions de pliage, ou d'utilisation,
• un angle de pliage, et
• une ou plusieurs valeurs de profondeur de pénétration.

The storage means 34 store the above calculation and management algorithms. In accordance with the present invention, the storage means 34 also contain a database. The database consists of groups of data, or values, G1 to GN, where N is an integer, each group of data relating to three types of elements, namely:

• a set of folding or use conditions,
• a folding angle, and
• one or more penetration depth values.

• critères de la matrice (voir figure 8A):
  • angle β de la matrice,
  • le rayon R_M de la matrice,
  • la largeur L de la matrice,
• critères du poinçon (voir figure 8B):
  • angle γ du poinçon,
  • rayon r_P de l'extrémité du poinçon,
• critères de la pièce (voir figure 8C):
  • épaisseur e de la pièce,
  • type de matière,
  • résistance de la matière,
• critère du pli (voir figures 8C et 8D):
  • largeur L' du pliage,
  • décalage D de la pièce par rapport au centre de la machine.

The folding conditions or criteria can be as follows:

• matrix criteria (see Figure 8A):
  • angle β of the matrix,
  • the radius R _M of the matrix,
  • the width L of the matrix,
• punch criteria (see Figure 8B):
  • angle γ of the punch,
  • radius r _P of the end of the punch,
• room criteria (see figure 8C):
  • thickness e of the part,
  • type of material,
  • material resistance,
• fold criterion (see figures 8C and 8D):
  • width L 'of the folding,
  • offset D of the workpiece in relation to the center of the machine.

As an illustration, Table I shows three groups of data G1, G2 and G3 stored in the database. content of the database G1 G2 G3 G4 G5 G6 Matrix angle 90 90 90 Matrix radius 0.20 0.20 0.20 Matrix width 10 10 10 Punch angle 90 90 90 Punch radius 0.2 0.2 0.2 Workpiece thickness 1 1 1 Material type Steel Steel Steel Material resistance 40 40 40 Folding length 1,000 1,000 1,000 Workpiece offset 0 0 0 Folding angle 90 120 135 Initial Y1 penetration - 2.26 - 1.55 - 1.11 Initial Y2 penetration - 2.26 - 1.55 - 1.11 CO1 correction - 0.05 - 0.12 0.08 CO2 correction - 0.05 - 0.12 0.08

Each data group G1 to GN contains data representative of bending conditions, a value of one folding angle and penetration depth values, say also updated penetration depth values or corrected. Penetration depth values are broken down into initial penetration values Y1 and Y2 and values of corresponding correction CO1 and CO2. Each depth of penetration (update) is equal to the sum of the value of initial penetration Y1, Y2 and the corresponding correction CO1, CO2. Each penetration depth Y1 + CO1, Y2 + CO2 is associated with a hydraulic axis of the press brake. More specifically, the values Y1 + CO1 and Y2 + CO2 are representative displacement of the punch in the V of the matrix which must perform respectively the cylinders 8a, 8b shown in Figure 7A to get the folding angle. Some machines, including "working lower" type, in which the lower deck 2 is mobile and the upper deck 1 is fixed, use only one axis per fold and therefore only require a penetration value indication Y and as an indication of correction value.

Data groups G1 to GN can be previously stored in the database above all operation, by the manufacturer or a user. The base of data may subsequently be modified or supplemented by the user, via the keyboard 26 and the screen 24. It can also be modified or supplemented by the digital control system 22 when executing a correction mode, which will be described in detail in the following.

The initial penetration values Y1, Y2 are generally values which have been previously obtained by calculation or by interpolation, for example from conditions of folding and a desired folding angle provided to the numerical control 22 by the operator, during the execution of a programming mode which will also be described below in detail. The correction values CO1, CO2, when they are non-zero, are values that have been previously obtained when executing the aforementioned correction mode.

Figure 7B schematically illustrates the different operating modes of the press brake system according to the invention.

On a main menu 80 appearing on the screen of display 24 of the digital control system 22, the operator can select programming mode 81, correction mode 82, a production mode 83 or a display mode 84.

In programming mode 81, the operator can program a part to bend. To do this, it enters conditions folding angle and desired folding angle in the numerical control 22, via the keyboard 26. The folding conditions entered by the operator must be the same type than those stored in the database (criteria of the die, punch, coin and fold). System 22 determines then, for each hydraulic axis, a penetration value Y1, Y2 to obtain the desired folding angle.

Figure 9 shows the algorithm implemented by the digital control system 22, and more particularly by its processor 32, during the execution of the programming mode.

In a step 100, the digital control system 22 reads the folding conditions and the value α of the desired folding angle entered by the operator via the keyboard 26.

During a step 102, the control system digital 22 queries the database, contained in the storage means 34, to check whether there is, in this base of data, a group of data having the same conditions of folding and the same folding angle as those entered by the operator.

If such a group exists, the depth of penetration included in the group, equal to the sum of the depth value initial penetration and the corresponding correction, for each axis, is selected as penetration depth to be implemented and displayed on the display screen 24 (step 104). The operator can then request the control system numeric 22, via keyboard 26, to send an order or a signal to the press brake 1-2-8a-8b, in order to make it execute folding with this depth of penetration. Folding is performed under the action of hydraulic cylinders 8a, 8b which move the deck higher 1 along a distance to reach this penetration depth.

If there is no data group in the database having the same folding conditions and the same folding angle as those entered by the operator, it is searched (step 106) if there are two groups of values GR1 and GR2 each having folding conditions identical to those entered by the operator and having respective folding angles α1 and α2 such that α1 <α < α2 . If these two groups exist, it is proceeded (step 110), for each axis, to an estimation of a penetration depth p to be implemented from depths p1 and p2, corresponding to this axis, stored in the groups GR1 and GR2 respectively. This is for example a calculation of p by interpolation of p1 and p2, for example: p = (p2 - p1). (α - α1) / (α2 - α1). As the depth value p1, p2, the sum of the initial value of penetration depth and the corresponding correction contained in the database is taken.

Yp_α représente la pénétration pour obtenir l'angle α

Y_RE représente le retour élastique

e représente l'épaisseur de la tôle ou de la pièce au voisinage du pli

r représente le rayon du Vé

V représente la largeur du Vé

β représente l'angle de la matrice

α représente l'angle demandé

r_i représente le rayon intérieur du pli

K représente le coefficient de la courbe de Hook

P_u représente la pénétration unitaire.

If no GR1 and GR2 groups are found having the same folding conditions as those indicated by the operator and for which α1 <α <α 2 , then a depth p is calculated (step 112) from a predetermined formula, for example the following formula (1): (1) Y Pα + Y RE = e + r + [ V 2 + r tg (45 - β 4 )] tg (90 - α 2 ) - ( r i + e + r cos (90- α 2 ) + r i V [V + 2r tg (45 - β 4 ) - 2 r sin (90 - α 2 )] + K sin 2 (α-90) + V 8th P u . or:

Yp _α represents the penetration to obtain the angle α

Y _RE represents the elastic return

e represents the thickness of the sheet or part in the vicinity of the fold

r represents the radius of the Vé

V represents the width of the Vé

β represents the angle of the matrix

α represents the requested angle

r _i represents the inside radius of the fold

K represents the coefficient of the Hook curve

P _u represents unit penetration.

• on applique une formule préétablie, telle que par exemple la formule (1) ci-dessus avec, comme paramètres, notamment les conditions de pliage et l'angle de pliage indiqués par l'opérateur au système de commande numérique 22, pour obtenir une première valeur de pénétration ; et
• on ajoute à cette première valeur de pénétration un terme correctif égal à (Corr2-Corr1).(α-α1)/(α2-α1),

   où Corr2 est la partie de correction de la profondeur p2 (égale à la différence entre la profondeur de pénétration p2 et la profondeur de pénétration initiale correspondante) et Corr1 est la partie de correction de la profondeur p1. According to another embodiment of the algorithm illustrated in FIG. 9, step 110, implemented when two groups GR1 and GR2 as described above have been found in the database, is carried out not by means of '' a simple interpolation on the penetration depth values, but as follows:

• applying a predetermined formula, such as for example formula (1) above with, as parameters, in particular the folding conditions and the folding angle indicated by the operator to the digital control system 22, to obtain a first penetration value; and
• a corrective term equal to (Corr2-Corr1) is added to this first penetration value. (α-α1) / (α2-α1),

where Corr2 is the depth correction part p2 (equal to the difference between the penetration depth p2 and the corresponding initial penetration depth) and Corr1 is the depth correction part p1.

According to yet another embodiment of the present invention, step 110 is implemented by performing a interpolation not on the folding angle, but on one of the folding conditions, such as the thickness of the workpiece.

• ayant les mêmes conditions de pliage que celles indiquées par l'opérateur, sauf en ce qui concerne l'épaisseur de la pièce,
• ayant le même angle de pliage que celui programmé par l'opérateur, et
• tels que les épaisseurs de tôle respectives e1, e2 satisfassent à la condition suivante : e1<e<e2, où e est l'épaisseur de la tôle programmée par l'opérateur.

Thus, instead of looking for two groups of data having the same folding conditions as those indicated by the operator and respective angles α1 and α2 such that α1 <α <α2, the digital control system 22 will search, in its base of data, two data groups GR1 'and GR2'

• having the same folding conditions as those indicated by the operator, except with regard to the thickness of the part,
• having the same folding angle as that programmed by the operator, and
• such that the respective sheet thicknesses e1, e2 satisfy the following condition: e1 <e <e2, where e is the thickness of the sheet programmed by the operator.

An interpolation, for example of the type p '= (p2'-p1'). (E-e1) / (e1-e2), where p1 'and p2' are the depths of penetration (updates) of the GR1 'and GR2' data groups, can then be performed to obtain an estimate of the depth of penetration.

Alternatively, you can also apply a formula preset such as formula (1) above with, as parameters including bending conditions and bending angle indicated by the operator, to obtain a first value of penetration, and add to this first penetration value a corrective term equal to (Corr2'-Corr1 '). (e-e1) / (e2-e1). where Corr1 'is the correction part of the penetration depth p1 'and Corr2' is the penetration depth correction part p2 '.

According to yet another embodiment of the present invention, step 106 may consist in carrying out a first searches the database to determine if two GR1 and GR2 data groups of the type described previously (with α1 <α <α2) are present and, if such groups are not found, do a second search for determine whether two data groups GR1 'and GR2' (with e1 <e <e2) are present. So, in case the system of numerical control 22 does not find groups GR1, GR2, but finds two groups GR1 'and GR2', it performs an interpolation on the thickness of the part.

The penetration depth value p calculated at step 110 or 112 is displayed on the display screen 24, and the operator can, as described above for step 104, do perform folding based on this value.

Correction mode, designated by the reference 82 in the figure 7B, corrects the penetration depth determined by the digital control system 22 during the execution of the mode programming, when the operator, after requesting the making a fold from this penetration depth, is not satisfied with the angle actually obtained.

In practice, after programming a room in the programming mode, the operator can, as has already been explained, ask the digital control system 22 to controls the folding machine 1-2-8a-8b depending on the value of penetration depth determined by the control system numeric 22. The operator can then measure the angle of the fold as performed, to check if this angle corresponds to the angle α that it had programmed.

Such a measurement can be carried out with a tool or a traditional reporter of the type described above in relation to the figure 6. In this case, after activating the correction mode, the operator enters, via the keyboard 26, the angle measured in digital control system 22, which compares the angle programmed and the angle measured. If these two angles are different, the numerical control system 22 determines a value of correction for penetration depth depending on the angle difference, in a manner known to those skilled in the art, in using a predetermined formula, such as formula (1) described previously. More specifically, the formula is applied to the angle programmed, to obtain a first penetration depth; the same formula is then applied to the measured angle, for get a second depth of penetration. The value of correction then corresponds to the difference between the first and second penetration depths. The operator can then do perform a fold from the corrected penetration depth, equal to the sum of the initial penetration depth and the calculated correction value.

The system 22 further modifies the database to to take into account the correction made. If the folding conditions and the folding angle entered by the operator in the numerical control 22 when executing the mode programming were already stored in the database, in the same data group, with a depth value initial penetration and a corresponding correction value (which is equal to zero if no correction had already been made on the penetration depth value corresponding to said folding conditions and folding angle), the control system numeric 22 changes the correction value in the database data.

If, on the other hand, the set constituted by the conditions of folding and the folding angle entered by the operator was not memorized in the database, i.e. if the penetration depth as determined during the execution of the programming mode a been calculated using an interpolation or formula preset as explained above, the system of numerical control 22 introduced into the database a additional data group, including the conditions of folding, the folding angle, the initial depth value of penetration (as determined by interpolation or the formula preset during the execution of the programming mode), and the value correction.

According to another embodiment, the reporter digital 21 is used in place of the aforementioned traditional reporter to measure the angle obtained.

FIG. 10 shows in detail the digital reporter 21. This protractor allows you to measure the angle of a part in the way next. A part 40 is wedged on a first support element 42, appearing for example in the form of an L, and against a flat face 44 of an element 46 pivoting about an axis of rotation 48. An angle indicator 50 displays the angles of rotation of the pivoting part 46. A graduated ruler 52 is marked on the circumference of the pivoting element 46. A detector 54 makes it possible to read the value of rule 46 at a certain fixed point relative to the case 58 of the part.

The detector 54 sends the measurement signals to a interface 60, which comprises (FIG. 11) a central unit 62 including a ROM memory 64, a RAM memory 66 and means for switching 68 (for locating an origin), 70 (for recording), and 72 (general switching). The reference 50 represents, as in FIG. 10, a screen for viewing the data. Means 74 also make it possible to transmit signals corresponding to the measurements made, towards the interface 30 of the digital control system 22.

The digital protractor can be previously calibrated by the operator. To this end, the operator activates a calibration mode. A calibration page appears on screen 24 of the control digital 22. In practice, the calibration mode is activated automatically by digital control system 22 when, when launching a correction mode automatic, a quality control mode or a display, which will be described later, the system 22 goes account that the calibration has not been carried out.

During the calibration, the pivoting element 46 is brought, by example manually, in a position chosen as position of reference for an angle of 180 °. The operator validates the choice of this position by acting on the switching means 68. The display screen 50 or the console 24 then displays a value 180 ° angle. By acting a second time on the means of switching 68, the operator ends the calibration phase.

When the operator activates, in correction mode 82, a function, or a so-called automatic correction mode, designated by the reference 85 in FIG. 7B, the value of the angle measured by the digital recorder 21 is read by the control system numeric 22, which then compares the programmed angle and the angle measured, and determines a correction value for the depth of penetration as a function of the angle difference. The determination of the correction value is performed in the same way as described above in relation to the correction mode, that is to say in applying a preset formula at the programmed angle, applying this same formula to the measured angle, and calculating the difference between the two penetration depths thus obtained.

The system 22 further modifies the database to to take into account the correction made. If the folding conditions and the folding angle entered by the operator in the numerical control 22 when executing the mode programming were already stored in the database, in the same data group, with a depth value initial penetration and a corresponding correction value (which is equal to zero if no correction had already been made on the penetration depth value corresponding to said folding conditions and folding angle), the control system numeric 22 changes the correction value in the database data.

If, on the other hand, the set constituted by the conditions of folding and the folding angle entered by the operator was not memorized in the database, i.e. if the penetration depth as determined during the execution of the programming mode a been calculated using an interpolation or formula preset as explained above, the system of numerical control 22 introduced into the database a additional data group, including the conditions of folding, the folding angle, the initial depth value of penetration (as determined by interpolation or the formula preset during the execution of the programming mode), and the value correction.

The database according to the invention is therefore dynamic, that is to say that it can be supplemented as and when measurement of the use of the press brake system.

Figure 12 illustrates in detail the algorithm implemented by the digital control system 22 during the execution of the automatic correction mode.

In a first step 160, a display is made of the programmed angle.

One or two values of are then displayed (step 162) penetration Y1, Y2 and one or two correction values of the penetration (see Figure 15), depending on the number of axes hydraulics provided on the bending machine 1-2-8a-8b. Values of correction are null if no correction had previously been performed on penetration depths.

The real angle obtained after folding and measured by the operator using the digital protractor described above, is displayed by the digital control system 22 (step 164).

The device is then reading a validation order (step 166), given by the operator for example by pressing more or shorter the switch button 68 of the protractor digital.

If the operator indicates in response that the action taken by the digital protractor is not correct (step 168), the step of measure is iterated (back to 164).

If the operator indicates in response that the measurement is correct, this is taken into account by the control system numeric 22 to assign a correction value to the depth of initial penetration, as explained above, for the axis concerned (step 170).

If the current axis is the last axis (step 172), it is performed an update of the database (step 174), of the previously explained.

Otherwise, the process resumes for the next axis (step 176).

Finally, the correction process can be continued for a other fold (steps 178, 180), also characterized by one or two axes, or the operator decides to end the correction process automatic (step 182)

An example of information presented to the operator in how this automatic correction mode is run is illustrated in Figure 15. This screen displays the two penetration values Y1, Y2, the two correction values, and the measured angle value (here: 90 °).

The production mode, designated by the reference 83 in the figure 7B, is activated by the operator when the latter, after having programmed a part (programming mode) and possibly done correct penetration depth (correction mode), wishes mass production. The digital control system 22 sends a command signal to the press brake 1-2-8a-8b to start production based on penetration depth determined during programming mode or, if correction mode has was also activated, based on the penetration depth corrected.

During the production cycle, the operator can also activate a so-called quality control mode, designated by the reference 86 on Figure 7B. This mode allows you to check the angle of the last fold made. The algorithm implemented by the digital control system 22 during the execution of the quality control mode is illustrated in the figure 13.

In a first step 140, a display is made of the programmed angle.

There is then reading and display of an angle measured by the operator using the digital reporter 21 (step 142). This measured angle is displayed. An operator can thus view both the programmed angle and the measured angle, as illustrated in figure 16.

A comparison is made by the control system numeric 22 between the measured angle and the programmed angle, and it is checked (step 144) if the angle measured is within the range of tolerance with respect to the programmed angle.

Depending on the result of the comparison, a message of correct or out of tolerance folding is displayed (steps 146, 148).

The device is then reading an end of quality control (step 150), given by the operator for example in pressing the switch button 68 of the digital reporter 21.

If the end of quality control order is present (step 152), the machine exits the quality control mode. Otherwise reading resumes (step 142).

The operator can carry out, using this control mode quality, random checks on any angle during the production or folding.

The display mode, designated by the reference 84 on the FIG. 7B, makes it possible to display on the screen 24 an angle measured at digital reporter 21 and transmitted by the latter to the digital control system 22 via cable 21a.

The algorithm implemented by the control system digital 22 when executing viewing mode is illustrated in FIG. 14. In a step 130, an angle of a part positioned on the digital reporter 21 is measured and displayed on the screen 24 (cf. Figure 17) until an order to end viewing (step 134) or a calibration order (step 138) is present. The end order of visualization is given by the operator for example by pressing protractor switch button 68 numeric 21, while the calibration order is given by pressing impulse this same button. If the order digital 22 detects an order to end viewing, the execution of the display mode ends at a step 136. If the command digital detects a calibration order, the calibration mode, described above, is activated in step 140.

The method according to the invention, described above in conjunction in particular with FIGS. 7B, 9, 12, 13 and 14, is preferably implemented by means of a program executed by the processor 32 of the digital control system 22 and stored in the area memory 34. This program may have been loaded from a medium (for example: floppy disk or CD Rom or any medium magnetic) capable of being read by a computer system or by the digital control system 22.

Such a support therefore includes instructions for making execute a method according to the invention, as described above, and in particular in connection with one of FIGS. 7B, 9, 12, 13 and 14.

The set can also be connected to other devices peripherals, for example to an electronic network of communication, to send and / or receive data on angles or folding conditions.

Thus, a plurality of machines from the same manufacturer can be linked by a network to a central unit which collects data stored by all machines individually. This results in the creation of larger files important, allowing, for example, to achieve statistical processing.

Claims (38)

1. Numerical control device (22) for a bending machine (1, 2, 8a, 8b), characterised in that it comprises:

   means (26) for inputting, as input data, a desired bend angle and bending conditions or criteria;

   means (34) for storing one or more groups of data, each containing bending conditions, a bend angle and at least one penetration depth;

   means (32) for searching, or especially programmed for searching, whether said input data is stored in the memory means, in the same group of data; and

   means for transmitting a signal representative of the penetration depth included in said same group of data, or for transmitting a signal for controlling the bending machine according to this penetration depth.
2. Numerical control device according to Claim 1, further including means (32) for searching, or especially programmed for searching, whether there exists, in the memory means, two groups of data (GR1, GR2) having the same bending conditions as those input by the inputting means, and respective bend angles (α1, α2) between which the desired angle (α) lies, and for calculating a penetration depth according to the penetration depths (p1, p2) belonging to the two groups of data, respectively.
3. Numerical control device according to Claim 1 or 2, further including means for calculating, or especially programmed for calculating, a penetration depth using a predetermined formula when the input data is not contained in the same group of data stored in the memory means and when two groups of data (GR1, GR2) having the same bending conditions as those input by the inputting means and respective bend angles (α1, α2) between which the desired angle (α) lies do not exist in the memory means.
4. Numerical control device according to Claim 1, the bending conditions including the thickness of the workpiece and the device further including means (32) for searching, or especially programmed for searching, whether there exists, in the memory means, two groups of data:

   having the same bending conditions as those of the input data, except with regard to the thickness of the workpiece,

   having the same bend angle as that desired, and

   such that the respective sheet thicknesses e1, e2 of both data groups satisfy the following condition: e1<e<e2, where e is the desired thickness of the sheet.
5. Device according to Claim 4, further including means (32) for calculating a penetration depth according to the penetration depths of the two groups of data.
6. Numerical control device according to one of Claims 1 to 5, including means for modifying, in the memory means, at least one parameter from among the bending conditions, the bend angles and the penetration depths.
7. Numerical control device according to one of Claims 1 to 6, the bending conditions being chosen from among the following conditions:

   conditions pertaining to the die (M) used

   conditions pertaining to the punch (P) used

   conditions pertaining to the workpiece to be worked

   conditions pertaining to the bend to be produced.
8. Numerical control device according to Claim 7, the conditions pertaining to the die comprising the angle of the die and/or the radius of the die and/or the width of the die.
9. Numerical control device according to Claim 7 or 8, the conditions pertaining to the punch used comprising the angle and/or the radius of the punch.
10. Numerical control device according to one of Claims 7 to 9, the conditions pertaining to the workpiece comprising the thickness of the workpiece and/or the type of material of which the workpiece is composed and/or the strength of this material.
11. Numerical control device according to one of Claims 7 to 10, the conditions pertaining to the bend relating to the bend angle and, possibly, to the length of the bending and/or the offset of the workpiece with respect to the centre of the machine.
12. Numerical control device according to one of Claims 1 to 11, further including means for comparing, or especially programmed for comparing, a measured bend angle with the desired bend angle.
13. Numerical control device according to Claim 12, including means for correcting, or especially programmed for correcting, the penetration depth if the result of the comparison is that the measured angle is different from the desired angle.
14. Numerical control device according to Claim 13, including means for updating, or especially programmed for updating, data in the memory means according to the result of the correction to the penetration depth.
15. Numerical control device according to Claim 13 or 14, including means for writing, or especially programmed for writing, into the memory means, an additional group of data containing said input data and the corrected penetration depth.
16. Numerical control device according to one of Claims 1 to 15, including means for displaying a measured bend angle and/or the desired bend angle.
17. Numerical control device according to one of Claims 1 to 16, including means for indicating, or especially programmed for indicating, whether a measured angle lies within a certain tolerance range with respect to the desired bend angle.
18. Press brake system including:

    a first beam (1) and a second beam (2), one of which is intended to receive a punch (P) and the other a die (M);

    means (8a, 8b) for producing a relative movement between the punch and the die; and

    a control device according to one of Claims 1 to 17, for controlling the means in order to produce a relative movement between the punch and the die.
19. Press brake system according to Claim 18, further including a digital angle-measuring device (42, 52, 58, 60) and means (74, 21a) for transmitting a measured value of an angle to the control device.
20. Numerical control process for a bending machine including the following steps:

    storing, in memory means, one or more groups of data each containing bending conditions, a bend angle and at least one penetration depth;

    receiving, as input data, a desired bend angle and bending conditions or criteria;

    searching whether the input data is stored in the memory means, in the same group of data; and

    transmitting a signal representative of the penetration depth contained in said same group of data, or a signal for controlling the machine according to this penetration depth.
21. Process according to Claim 20, further including a step consisting in searching whether there exists, in the memory means, two groups of data (GR1, GR2) having the same bending conditions as those contained in the input data, and respective bend angles (α1, α2) between which the desired angle (α) lies, and in calculating a penetration depth according to the penetration depths (p1, p2) belonging to the two groups of data, respectively.
22. Process according to Claim 20 or 21, further including a step consisting in calculating a penetration depth using a predetermined formula when the input data is not contained in the same group of data stored in the memory means and when two groups of data (GR1, GR2) having the same bending conditions as those contained in the input data and respective bend angles (α1, α2) between which the desired angle (α) lies do not exist in the memory means.
23. Process according to Claim 20, the bending conditions including the thickness of the workpiece, the process further including a step consisting in searching, whether there exists, in the memory means, two groups of data:

    having the same bending conditions as those of the input data, except with regard to the thickness of the workpiece,

    having the same bend angle as that desired, and

    such that the respective sheet thicknesses e1, e2 of both data groups satisfy the following condition: e1<e<e2, where e is the desired thickness of the sheet.
24. Process according to Claim 23, further including a step for calculating the penetration depth according to the penetration depths of the two groups of data.
25. Process according to one of Claims 20 to 24, including a step consisting in modifying, in the memory means, at least one parameter from among the bending conditions, the bend angles and the penetration depths.
26. Process according to one of Claims 20 to 25, the bending conditions being chosen from among the following conditions:

    conditions pertaining to the die (M) used

    conditions pertaining to the punch (P) used

    conditions pertaining to the workpiece to be worked

    conditions pertaining to the bend to be produced.
27. Process according to Claim 26, the conditions pertaining to the die including the angle of the die and/or the radius of the die and/or the width of the die.
28. Process according to Claim 26 or 27, the conditions pertaining to the punch used including the angle and/or the radius of the punch.
29. Process according to one of Claims 26 to 28, the conditions pertaining to the workpiece including the thickness of the workpiece and/or the type of material of which the workpiece is composed and/or the strength of this material.
30. Process according to one of Claims 26 to 29, the conditions pertaining to the bend relating to the bend angle and, possibly, to the length of the bending and/or the offset of the workpiece with respect to the centre of the machine.
31. Process according to one of Claims 20 to 30, a comparison being further made between a measured bend angle and the desired bend angle.
32. Process according to Claim 31, including a step consisting in correcting the penetration depth if the result of the comparison is that the measured bend angle is different from the desired bend angle.
33. Process according to Claim 32, including a step consisting in updating data in the memory means, on the basis of the result of the correction to the penetration depth.
34. Process according to Claim 32 or 33, including a step consisting in writing, into the memory means, an additional group of data containing said input data and the corrected penetration depth.
35. Process according to one of Claims 32 to 34, a measured bend angle and/or the desired bend angle being displayed.
36. Process according to one of Claims 32 to 35 including indicating whether a measured angle lies within a certain tolerance range with respect to the desired bend angle.
37. Computer program including instructions for carrying out a process according to one of claims 20 to 36.
38. Support medium likely to be read by a data processing system or a numerical control system, on which medium data is recorded to cause said data processing system or said numerical control system to carry out a process according to one of claims 20 to 36.

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