EP1614487B1 - Process of geometric construction of a flash for forging a workpiece of complex shape - Google Patents

Description

The present invention relates to the geometrical construction of the engravings of the press dies and more precisely the burrs cords and their clearances provided on the periphery of the etchings for forging complex parts, here turbomachine blades.

Burr is the means by which the filling of the engraving by the material is perfected during the forging of the pieces. By providing a suitable burr cord, it is ensured that the enclosed material has an obligation to first fill the cavity of the etching before escaping. The burr cord allows the evacuation of surplus material at the end of the engraving.

In addition to the good flow of the material, optimizing the shape of the burr cord allows a good repeatability of the parts obtained and a reduction in forging forces, which leads to an increase in the life of the press tools.

This optimization depends in particular on the temperature of the part and the tools, their coefficient of mutual friction, and the shape of the blank of the part before the forging.

In order to determine the geometry of the burr bead, the definition of the shape of the forged part is used in particular. For complex parts such as turbine engine blades, it is necessary to define the characteristics of the cross sections of the blade, in the direction of the thickness, of the burr cords to connect them in extension of the cross sections of the blade from the characteristics. above.

For turbine blade die-forming tools, calculations are tedious (thousands of points to be defined for the construction of a matrix) and therefore the process is expensive. In addition the risk of input errors is important and may cause the appearance of parasitic ripples in the surfaces defining the burrs cords.

The applicant has sought to improve this process.

• on choisit au moins trois sections de référence de la pale selon des plans de référence correspondants au bas, milieu et sommet de pale,
• dans lesdits plans de référence, on détermine la longueur du cordon de bavure et une distance de retrait pour les trois sections de référence,
• dans lesdits plans prédéterminés, on construit par interpolation les sections intermédiaires du cordon et du dégagement de bavure à partir desdites sections de référence.

To this end, the invention relates to a geometric construction method of a burr bead, to be provided in a turbomachine blade forging die according to determined parameters, the blade comprising a blade and the blade being defined by sections. planes according to predetermined planes, and the burr bead and the flash clearance being defined in said planes to obtain planar sections of the blade and the bead, characterized in that:

• at least three reference sections of the blade are chosen according to reference planes corresponding to the bottom, middle and top of the blade,
• in said reference planes, the length of the burr cord and a withdrawal distance for the three reference sections are determined,
• in said predetermined planes, the intermediate sections of the bead and the flash clearance are constructed by interpolation from said reference sections.

Preferably, before calculating the intermediate sections of the bead and its clearance, various bead bead parameter determinations are made by varying the said parameters in the reference sections.

Also preferably, the blade of the turbomachine blade having a leading edge and a trailing edge, the sections of the burrs and clearance corresponding to the leading and trailing edges are determined simultaneously.

The intermediate sections of the burr cord and its clearance can thus be largely calculated automatically, which allows a considerable saving of time.

Advantageously, to determine the intermediate cross sections of the bead and its release, a polynomial interpolation is used.

Preferably again, after interpolation, the stripping reliefs are rectified in order firstly to prevent the creation of undercuts or substantially vertical surfaces which can weaken the matrix, and secondly to reduce the differences in the height of the apex. 'dawn.

• les figures 1 et 2 représentent une vue perspective de l'ensemble des sections planes Pi et des sections de référence choisies parmi ces sections planes pour une aube de turbomachine, ainsi que des sections du cordon de bavure générées avant redressement ;
• la figure 3 est une figure géométrique montrant les différents points caractéristiques de définition d'une section de bord d'attaque ou de fuite d'une aube de turbomachine ainsi que ceux du raccordement du cordon de bavure et de son dégagement aux dits bords, points utilisés dans le procédé selon l'invention,
• la figure 4 représente une vue perspective de l'ensemble des sections de la pièce, du cordon de bavure et du dégagement de bavure correspondant non redressé d'une aube de turbomachine, et redressé lorsque nécessaire ;
• la figure 5 représente une vue de l'outillage de presse pour forger une aube de turbomachine, montrant l'axe de frappe, le plan de frappe et les angles du dégagement de bavure non redressé et redressé d'une section plane du cordon de bavure et du dégagement de bavure correspondant;
• la figure 6 représente une vue perspective des surfaces, cordon et dégagement de bavure d'une matrice de presse pour forger une aube de turbomachine, en regard l'une de l'autre, montrant le résultat de l'interpolation après application du procédé de l'invention ; et
• la figure 7 représente une vue perspective de la surface définitive d'une matrice de forge d'une aube de turbomachine.

The invention will be better understood from the following description of the bead bead determination method with reference to the accompanying drawing, in which:

• Figures 1 and 2 show a perspective view of the set of plane sections Pi and reference sections selected from these planar sections for a turbine engine blade, and sections of the burr cord generated before recovery;
• FIG. 3 is a geometrical figure showing the different characteristic points of definition of a leading edge section or leakage section of a turbomachine blade as well as those of the connection of the burr cord and its release to said edges, points. used in the process according to the invention,
• FIG. 4 represents a perspective view of all the sections of the part, the burring bead and the corresponding unfurned burr clearance of a turbomachine blade, and straightened when necessary;
• FIG. 5 represents a view of the press tooling for forging a turbomachine blade, showing the striking axis, the strike plane and the angles of the unreflected and straightened burr clearance of a flat section of the burr cord. and corresponding flash clearance;
• FIG. 6 represents a perspective view of the surfaces, bead and flash clearance of a press die for forging a turbomachine blade, facing one another, showing the result of the interpolation after application of the method of FIG. the invention; and
• FIG. 7 represents a perspective view of the final surface of a forge matrix of a turbomachine blade.

With reference to FIG. 1, a turbine engine blade blade 10 comprises the two intrados and extrados surfaces comprised between a leading edge BA and a trailing edge BF, on the one hand, and a blade tip 9 and a blade root 8, on the other hand. Between the intrados and the extrados, the dawn consists of a material 1 forged by means of a forging machine (not shown) of given power and acting on a press tool consisting of two matrices which will be evoked by the following.

The blade 10 is geometrically defined by plane Si sections located in predetermined planes Pi, at the intersection of these planes with the intrados 2 "and the extrados 2 '.

These sections are also those of the dies when they are in forging position of the part or the blade during its forging. They will no longer be distinguished from each other in the rest of the document.

In a first initial step, it is necessary to choose at least three planes 8, 10, 9 of reference Pa, Pb and Pc, providing three sections Sa, Sb, Sc. The three reference sections make it possible to determine parameters of cord construction. This is what has been done in FIG. 2, the three reference sections being the sections S2, S6, S11 corresponding to the foot, middle and top of the blade.

In a second so-called verification step, the burr cords 5 are geometrically constructed and their corresponding clearance 6 only for the sections Sa, Sb and Sc, on the BA side and on the BF side.

The construction is based on the geometric elements shown in FIG. 3, on which the intersections of the intrados 2 "and the extrados 2 'are recognized with a reference plane Pj taken from the set Pa, Pb and Pc, and the trace on Pj of the leading edge BA or leakage BF.

• la courbe squelette 3 ensemble des points centres de cercles 4 tangents simultanément à l'extrados (en 4') et à l'intrados (en 4"),
• un point de mesure 11 issu de la définition de CAO (conception assistée par ordinateur) de la pièce et servant de point de contrôle ou de mesure pour la pièce finie.

The following additional elements are used here:

• the skeleton curve 3 together points centers of circles 4 tangent simultaneously to the extrados (in 4 ') and the intrados (in 4 "),
• a measuring point 11 derived from the definition of CAD (computer-aided design) of the part and serving as a control point or measurement for the finished part.

These elements are part of the geometric definition of dawn or dies, which is available on a computer medium in any CAD format.

• le point de retrait 13, situé entre le point de mesure 11 et le bord d'attaque BA, ou le bord de fuite BF selon le cas, à une distance de retrait d du point de mesure 11,
• à une distance l du point de retrait 13, et dans le prolongement du point de retrait par rapport au point de mesure, le point de dégagement 14, délimitant un segment de longueur l, longueur théorique du cordon de bavure.
• α l'angle d'ouverture du dégagement de bavure et R = h/2, le rayon du cercle tangent au dégagement de bavure définissent la longueur du dégagement de bavure ainsi que la hauteur du dégagement entre matrices.
  En général, la valeur de l'angle α est de 60°.

In the plane Pj, we further define the tangent 12 to the skeleton curve 3 at the measuring point 11, and on this tangent, the following geometric elements:

• the point of withdrawal 13, situated between the measuring point 11 and the leading edge BA, or the trailing edge, as appropriate, at a withdrawal distance d from the measuring point 11,
• at a distance l from the point of withdrawal 13, and in the extension of the point of withdrawal from the measurement point, the clearance point 14 delimiting a segment of length l , the theoretical length of the burr cord.
• At the opening angle of the flash clearance and R = h / 2, the radius of the circle tangent to the flash clearance defines the length of the flash clearance as well as the height of the clearance between dies.
  In general, the value of the angle α is 60 °.

Pour une pièce en titane, forgée à une température de 940°C, λ est moitié moindre.The burr cords are defined by two dimensions, the length λ and its thickness ε, they are linked by the relation λ / ε. They are fixed from a criterion of complexity relative to the shape of the part and the type of gear used. For example, for a steel part, forged at 1050 ° C on a screw press, the actual length of the bead must be: $$\lambda ={\left(\mathrm{greater\; width\; of\; the\; <figure-callout\; id="1"\; label="room"\; filenames="imgf0001.png"\; state="\{\{state\}\}">room</figure-callout>}\right)}^{1/2}$$

For a piece of titanium, forged at a temperature of 940 ° C, λ is half less.

• les points théoriques 13' et 13" respectivement intersections des courbes 2' (extrados) et 2" (intrados) avec la droite dr, normale à la courbe squelette et passant par le point 13, distante, d'une certaine distance dite de retrait, du point de mesure 11 du bord d'attaque ou de fuite de la pale
• les parallèles T' (extrados) et T" (intrados) à la tangente 12 passant respectivement par 13' et 13"
• les points théoriques 14' et 14" respectivement intersections de la perpendiculaire N1 menée du point de dégagement 14 à la tangente 12 avec les parallèles T' et T",
• les points théoriques 16' et 16" respectivement intersections des demi droites parallèles 21' et 21 " tangente au cercle de rayon h/2 et les demi-droites 20' et 20".

All these elements make it possible to define the theoretical characteristic points of the section, called optimal, of the burring bead and the corresponding flash clearance by the plane Pi:

• the theoretical points 13 'and 13 "respectively intersections of the curves 2' (extrados) and 2" (intrados) with the straight line dr, normal to the skeleton curve and passing through the point 13, distant, of a certain distance called withdrawal , measuring point 11 of the leading edge or leakage of the blade
• the parallels T '(extrados) and T "(intrados) to the tangent 12 passing respectively by 13' and 13"
• the theoretical points 14 'and 14 "respectively intersections of the perpendicular N1 led from the clearance point 14 to the tangent 12 with the parallels T' and T",
• the theoretical points 16 'and 16 "respectively intersections of the parallel half-lines 21' and 21" tangent to the circle of radius h / 2 and the half-lines 20 'and 20 ".

The segments 15 'defined by the points 13'-14', 20 'defined by the points 14'-16', the right half 21 'on the one hand, and the segments 15 "defined by the points 13" -14 " , 20 "defined by the points 14" -16 ", the half-right 21" on the other hand determine the section, called optimal theoretical, of the burr cord 5 and the corresponding flash clearance 6 in the plane Pj.

To obtain the characteristic geometrical points of the optimum section of the bead and the clearance actually used for the manufacture of the dies of the press tool, points marked by the letters A ', B', C ', D', E ', F the extrados side and the letters A ", B", C ", D", E ", F" on the intrados side, three connecting radii R1, R2, R3 are respectively introduced, as shown in FIG. 3, and the coordinates of Geometric points above. It is necessary that R1 is not too big so as not to touch the measuring point on the one hand and large enough so that there is no edge between the burr cord and the blade on the other hand . In other words, A 'and A "are, in FIG. 3, to the right of the normal N. Finally, a useful length of cord B'C' or B" C 'equal to the length λ is obtained.

Thus we proceed for each reference plane Pa, Pb, Pc and we obtain global plane sections, so called because meeting sections of the room, the cord and the clearance in these reference planes, so assembly of the reference sections Sa, Sb, Sc and optimal sections of the burr cord and its clearance.

In a third step, called choice, the parameters l and d are determined, then the connections R1 and R2 in the sections Pa, Pb, Pc. These variable parameters will make it possible to obtain the length λ of the burr cord best suited to the part.

Once the parameters are determined, we proceed to an interpolation step, to obtain the optimal sections of the cord and its release in all the plants Pi.

The interpolation, automatic, can be linear, quadratic, cubic, in polynomial summary, and the optimal sections 5 and 6 of FIG. 2 are thus obtained for all the planes Pi. These optimal sections are also shown in FIG. detail of the segments 15 ', 15 ", 20', 20" of the plane Pi.

The sections of the burr cords corresponding to the leading and trailing edges can be calculated simultaneously, but with different parameters, such as the theoretical length l of the bead, the withdrawal distance defining its thickness ε, the height h, the angle α, etc .....

However, with reference to FIG. 5, the result of the automatic interpolation can, for certain extreme values of i, near the root of the blade, for example, not be acceptable and provide segments, such as C13, which are misdirected. relative to the orientation of the Fo strike of the forging machine. In the example of the figure, the matrix can not push the material back into the clearance angle.

It is during a fourth step, called straightening, that rectify segments C11, C12 and C13, poorly oriented, along segments C "12, C" 11 and C "10.

To make the clearings of burr it is necessary to choose the sections of references BA and BF side foot of the dawn and top of the dawn. By choosing four reference sections, two sides BA, s3 at the foot and s9 at the end of the blade, and two sides BF, s4 at the foot and s8 at the end of blade, to straighten the orientation of the flash clearances, the construction process allows to get perfectly smooth surfaces.

The segments C10 and C20 of the reference section are projected on the previous or next section, represented C'10, depending on whether one is towards the foot or the top of the blade. Through points 18 'and 18 "of FIG. 3 and shown in FIG. 5, the parallels are taken at C'10 and C'20 respectively, then the bisectors between C11 and C" 10 parallel to C'10 passing through are constructed. by point 18, on the one hand and C21 and C "in the same way by point 18" on the other hand. These segments are the new flash clearances so the reference segments are projected on the previous or next section and so on.

A program provided for this purpose can make several attempts to choose the reference sections that give the best result. The recovery of the flash clearances is thus achieved in a single operation.

After having adjusted the orientation of the flash clearances, the construction of the surfaces defining the theoretical flash cords and the associated clearances which will be used to produce the press tooling as shown in FIGS. 6 and 7 are carried out.

• 101' pour la pale,
• 102' pour le raccordement rayon R1,
• 103' pour le cordon utile,
• 104' pour raccordement de rayon R2,
• 105' pour le dégagement de bavure,
• 106' pour le raccordement de rayon R3,
• 107' pour le dégagement de l'outillage, correspondant à la demi droite 21 '

In FIG. 6, the two contact surfaces of the forging dies of a turbomachine blade are shown face to face, and the surfaces of the dies 110 and 120 are distinguished thereon:

• 101 'for the blade,
• 102 'for the connection radius R1,
• 103 'for the useful cord,
• 104 'for radius connection R2,
• 105 'for flash clearance,
• 106 'for the connection of radius R3,
• 107 'for the release of the tool, corresponding to the right half 21'

The matrix 120 is represented by the same corresponding elements, the surfaces corresponding to X 'being here marked X ".

Figure 7 shows the matrix 120 alone by its elements already shown in Figure 6.

Claims (5)

1. Geometrical construction of a flash land (5), to be provided in a die (110, 120) for the forging of a turbomachine vane, in accordance with determined parameters (l, d, ε, α, h), where the vane includes a blade (10), the blade is defined by plane sections (Si) according to predetermined planes (Pi), and the flash land (5) and its flash gutter must be defined in accordance with the said predetermined planes to obtain plane sections of the blade and of the flash land, a process which is characterised by the fact that:

   - one chooses at least three reference sections (Sa, Sb, Sc) of the blade in reference planes (Pa, Pb, Pc) corresponding to the root, middle and tip of the blade,

   - in the said reference planes, one determines length (λ) of the flash land and a shrinkage distance (d) for the three reference sections,

   - in the said predetermined planes, one constructs, by interpolation, the intermediate sections of the flash land and flash gutter from the said reference sections.
2. A process according to claim 1, in which, before calculating the intermediate sections of the flash land and its gutter, one effects different determinations of flash land parameters by varying the said parameters in the reference sections.
3. A process according to either of claims 1 and 2, in which the sections of the flash land and the corresponding flash gutter at the leading (BA) and trailing (BF) edges are calculated simultaneously.
4. A process according to either of claims 1 to 3, in which, in order to determine the intermediate sections of the flash land and of the flash gutter, one uses a polynomial interpolation technique.
5. A process according to claims 1 to 4, in which, after interpolation, one rectifies the orientation of the sections of the flash gutter (20', 20") in order to remove the undercuts or vertical walls.

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