EP1369193A1 - Formage à froid par roulage de pièces en matériau pressé-fritté - Google Patents
Formage à froid par roulage de pièces en matériau pressé-fritté Download PDFInfo
- Publication number
- EP1369193A1 EP1369193A1 EP03076687A EP03076687A EP1369193A1 EP 1369193 A1 EP1369193 A1 EP 1369193A1 EP 03076687 A EP03076687 A EP 03076687A EP 03076687 A EP03076687 A EP 03076687A EP 1369193 A1 EP1369193 A1 EP 1369193A1
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- European Patent Office
- Prior art keywords
- blank
- phase
- rolling
- tools
- force
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/18—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by using pressure rollers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21H—MAKING PARTICULAR METAL OBJECTS BY ROLLING, e.g. SCREWS, WHEELS, RINGS, BARRELS, BALLS
- B21H5/00—Making gear wheels, racks, spline shafts or worms
- B21H5/02—Making gear wheels, racks, spline shafts or worms with cylindrical outline, e.g. by means of die rolls
- B21H5/022—Finishing gear teeth with cylindrical outline, e.g. burnishing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
- B22F5/08—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of toothed articles, e.g. gear wheels; of cam discs
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B11/00—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses
- B30B11/005—Control arrangements
- B30B11/006—Control arrangements for roller presses
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49462—Gear making
- Y10T29/49467—Gear shaping
- Y10T29/49471—Roll forming
Definitions
- the invention relates to the cold forming of parts from blanks, in particular metal. It applies in particular to blanks of pressed-sintered material.
- Cold forming means a deformation of the metal of the blank at temperature ambient or semi-warm (up to a temperature of 300 to 500 ° C depending on the metal of the blank), below its melting temperature.
- the blank is often driven by the tool or tools; but she can also do the object of a separate training, synchronized or not.
- the present invention improves the situation.
- the cold forming process by rolling a blank of material pressed-sintered is of the type in which at least one tool for approaching the blank is approached pre-determined peripheral geometry, to then roll the tool over the blank by soliciting towards each other.
- appendix 1 expresses, in the form of a table, the characteristics of the order cold forming machines according to the invention.
- Cold forming makes it possible in particular to achieve a very precise shape (forming proper), and / or to adjust a surface finish, which is often called burnishing, or still "superfinish".
- the blank is what enters the forming machine, with or without preform, and the part, which comes out.
- the invention relates a priori to the methods using machines known as "with variable center distance”, with tools of substantially constant profile on their periphery, and working "in diving ", that is to say by getting closer to the part or blank.
- This differs from “Incremental” machines (registered trademark), which have tools with a profile variable, generally progressive, on their periphery, and work with a fixed center distance, i.e. without relative movement of approximation of the axes of revolution of the tools and the piece, or machines working "in a row”, involving an axial circulation of the part compared to tools with a constant working distance.
- Figure 1 relates to a rolling machine with two tools O1 and O2, which work on a blank to form EB (which can also be called “part”).
- the machine includes, on a general frame (not shown), two half-frames F1 and F2, which support the tools in rotation O1 and O2, around substantially parallel axes A1, A2.
- An M1 motor electric by example, drives two worm gear / threaded roller SCR1 -G1 and SCR2-G2 (or just one), whose exit movement is applied to tools O1 and O2 to rotate them in the same sense in synchronism.
- the axes A1 and A2 define the respective reference axes tools for forming the blank.
- the machine comprises, on the general frame, a support (not shown) of the EB blank, so that it can move in rotation, in opposite direction of the tools, around an axis substantially coplanar with the two axes of rotation A1 and A2.
- the two half-frames F1 and F2 are movable relative to each other, here under the effect of a cylinder system, with piston P1 and cylinder C1, placed on one of the half-frames, while the end of the piston rod is fixed in P10 to the other half-frame.
- the laterality of this command can be compensated by a mechanical balun, not shown.
- the machine further comprises, illustrated diagrammatically, an XS position sensor relative of the two half-frames, therefore of the axes A1 and A2.
- the two actuator chambers and on the other side of the piston P1 are supplied with fluid from a hydraulic power station HG, at through an SV servo valve. This is controlled by a digital control controller NC.
- the NC controller receives an indication of the pressures Pa, Pb in the two chambers of the cylinder. It also receives the indication of the X position of the XS sensor. It addresses to the servo valve an SVC command, in correspondence with PRG program data, and its entries.
- FIG. 1 corresponds for example to the machines of the Hxx CN series from ESCOFIER TECHNOLOGIE, where xx corresponds to two digits indicating a dimension.
- the program data are used to carry out the forming of the EB blank, by relative advance of axes A1 and A2, taking into account the peripheral geometry of the tools, and many other parameters.
- penetration, calibration, decompression we can distinguish three major phases: penetration, calibration, decompression.
- the machine shown in Figure 2 is of the same kind, except that instead of being moved only by tools O1 and O2, the blank is driven positively by an M2 motor, for example electric. This variant can also be applied to the embodiments below.
- Figure 3 is similar to Figure 1, and the training of tools O1 and O2 is not repeated.
- the difference is that the general frame B appears, on which the half-frames F1 and F2 are mounted by means of screw / nut systems BSD1 and BSD2, which are activated by two homologous transmissions from an electric motor M3 fixed to the frame.
- the NC controller receives motor state quantities, in particular the information on the angular speed ( ⁇ ) and the position of the rotor ( ⁇ ); he drives the M3 engine accordingly, based on the PRG program database, and the instantaneous position X, which is a function of the angular position ⁇ .
- Figure 3 corresponds for example to the NT series machines from ESCOFIER TECHNOLOGIE.
- Figure 4 partially illustrates another variant.
- the EB draft, annular is housed in a PP workpiece holder. and the tool O1 is inside, driven by the motor M1, while at outside, a roller G driven in rotation by contact with the workpiece carrier allows the application of the rolling force.
- the position sensor XS is inside, between F2 and B.
- the elements of control of figure 1 (SV, HG, NC, PRG) can be transposed to figure 4, only the servo-valve SV (or equivalent) being shown in Figure 4.
- a variant of Figure 4 is to use for training one of the systems Figure 3, for example that illustrated in BSD1, and its auxiliaries, with the corresponding control elements (M3, NC, PRG).
- FIG. 4 corresponds for example to the machines of the ALS series from ESCOFIER TECHNOLOGIE.
- peripheral geometries of tools are used, in particular for forming grooves, knurling, threading, gearing, or any other basic shape cylindrical.
- tools will designate one or more tools, also called “knurls”.
- the physical quantities relating to the previous parameters determine at all times the resulting effort, necessary and sufficient, which is brought into play during the deformation.
- the surface deformed by the tool also increases during rolling, while the roughing gradually takes the combined form of the tool (s).
- the rolling force is the product of the contact pressure of the tool (s), by the surface of action of these. Assuming (for simplicity) a constant penetration speed of tools, the rolling effort therefore increases with the advancement of the rolling, and this at least also faster, generally faster, than this speed of penetration.
- the rolling tools are subjected to significant forces. intensity and the repetition of these will determine the duration of use of a tool.
- the cost of the tool is an important part of the cost of the rolling operation, and can even compromise the profitable or competitive nature.
- the aforementioned machines generally work on blanks for solid metal parts.
- the servos which control the support of the tools on the workpiece are controlled in position, and apply the effort required - whatever it is - to maintain the relative position expected between the tools and the workpiece, during the forming process.
- press-sintered blank means a part obtained at an earlier stage by sintering metallic powders, i.e. a part whose relative density remains below 100 %.
- a press-sintered blank can be obtained by mechanical uniaxial pressing of powders, and solid phase sintering.
- the blanks thus obtained are incomplete densified, their density ranging from 80 to 95% of that of a solid material (relative density), typically 90 to 92%.
- the Applicant is again interested in the rolling of parts made of pressed-sintered material. She observed that when a rolling technique is applied to press-sintered blanks, the limits and conditions for producing the parts from these blanks are very different from what would be encountered for identical parts rolled from of a massive blank of the same material. Indeed, the density and resistance of the material pressed-sintered are lower than those of solid material, and the distributions of the characteristics dimensional of the blanks are more spread out, in particular the eccentricity, the roundness.
- the distance between the external surface of the part is called here "densification thickness” and its core limit, where the pressed-sintered material retains the initial density of the blank (density obtained at the last sintering operation).
- this densified layer locally more resistant, is not enough to resist the overall strain effort when it becomes significant; then the heart is not itself not strong enough. This causes various deteriorations. This results in particular in local or complete bursting of the part, for example from the core, for parts solid, or from surfaces, for ball bearing rings.
- the Applicant observed that excessive tri-axial stresses occur on areas insufficiently resistant to breakage, because not completely densified. Were also observed phenomena of material collapse or disintegration thereof on the surface, which then leaves in dust or small fragments, which makes it impossible to continue driving. An instability of the deformation has also been observed, which seems specific to the material.
- the pressed-sintered material has significant variations in homogeneity, which are increased by the manufacturing process sketches. These variations are large enough to help increase the difficulties in controlling driving conditions, as necessary for generate parts in accordance with the user's geometric and functional wishes.
- the NC command is carried out as shown schematically in Figure 6.
- the output stage NC90 which controls the servo valve is itself controlled by a stage NC 10 which defines the flow rate of the servo valve as a function of the current position X, and possibly of its previous values (or its derivative). So we actually act on the speed of advance of the tools, and therefore on positions.
- the floor NC90 which controls the servo valve or the servo valve is itself controlled by an NC20 stage which defines a variation in the flow rate of the servo-valve or the servo-distributor, so as to control the forces or forces transmitted to the part or blank during the driving cycle, depending on the current effort.
- this effort is calculated from values of pressure sensors, such as Pa, Pb, mentioned above, taking into account the surfaces exposed to the fluid on either side of the piston. Effort can also be measured.
- the means of measuring physical variables of effort and position, necessary for control and to the servo are chosen in accordance with the solutions selected for the design of the different types of machines involved.
- the thickness of densification obtained with "effort" control is generally a little more important than the one obtained in position control. This seems to be due to better "regularity" of the rolling action, in the presence of imperfections.
- work hardening can be better controlled. The same is true for the effects of variations in ambient temperature on the machine, as well as the temperature of its internal components, especially the driving elements (such as the fluid). It is also the same for effects of surface heating of the workpiece or blank, which are also better controlled. In addition, this heating is less, due to the better control of work hardening.
- the difficulty is due not only to the effects of small irregularities of all kinds, but also to the fact that the interaction between a given area of the blank and the active tools takes place in a "chopped" manner, n times per revolution of the draft, where n is the number of active tools.
- rolling cycles are implemented comprising the operations described below.
- the X positions are considered to be decreasing when the tools approach the workpiece (since the tools then approach each other, and at the same time play time).
- An initial approach operation 80 or (a 0 ), not shown in table 1, can be carried out in any desired manner, up to a position of the tools at a short distance from the part.
- phase 82 or (a 1 ) - (a) in table 1 - approaches the part. It comprises a slow advance at speed Ca, and under a weak force Fa, linked to the movement of the carriages.
- the docking is carried out by looking for the position Xa, between Xa 1 and Xa 2 , for which the force required to advance increases appreciably to a value Fa 1 , indicating contact between tools and part.
- the value of the force threshold Fa 1 is suitably adjusted to avoid a harmful imprint of the tools on the part at first contact. This adjustment is more delicate with a press-sintered blank, and may have to be carried out by trial and error, during development tests.
- the force applied to the tools as a result of their displacement relative to the part, then gradually increases in a controlled manner to a desired level Fb.
- a limit is set in advance X, to avoid possible disastrous consequences of a beginning of collapse of the pressed-sintered material on itself (like a human foot on ungroomed snow). By "collapse”, here we hear an unexpected sudden jump in position.
- the initial phase or phases 84 of operation (b) are carried out with one or more levels of rate of growth of the effort.
- two growth rates are predicted, substantially equal to (Fb 1 - Fa 1 ) / Tb 1 , then (F b2 - Fb 1 ) / Tb 2 , to reach the levels Fb 1 and Fb 2 , respectively .
- the progression of the effort applied to the roughing can be maintained under a value defined limit, so as not to have a critical state during the deformation (in particular triggering of the above-mentioned collapse).
- the increase in effort is chosen as fast as possible, to limit the effects of strain hardening after contact successive tool / part. Indeed, excessive hardening results in hardening superficial, which increases the effort required to continue forming, and therefore also increases the risk of incurring a critical condition, recall that the drafts have dimensional tolerances, surface irregularities, and also inhomogeneity intrinsic.
- the effort is then controlled (F) for one or more several successive phases, so that its evolution continues to respect a predefined cycle, until reaching a final relative position tools / part (Xb) in accordance with the final dimension of the part.
- the most complicated can be a succession of phases with controlled effort evolving gradually, regularly or in successive stages, in a controlled manner. In general, the values of controlled effort Fb remain close to the effort Fb 2 reached at the end of step b 2 (or more generally b n ).
- phase (b) During phase (b), generally called “penetration”, densification is obtained surface of the blank, over a selected densification thickness.
- This thickness of densification depends on the density of the blank before rolling, on the nature of its material constitutive, as well as the geometrical modification imposed by the tools during the taxiing, taking into account the applied servo force values. There too, the conditions required to obtain a chosen densification thickness can be determined by preliminary tests.
- This phase can use a position control, to fix a relative position tools / part (Xc). This can for example make it possible to obtain a part meeting criteria of user-defined circularity.
- the effort is no longer the basic size of the enslavement for this phase, and it generally varies appreciably decreasing, up to a low value, linked to the plastic deformation limit value, below which the part only undergoes elastic deformations.
- the relative roughing / tool position is kept substantially constant during a chosen time, defined to obtain a part of acceptable geometry, in particular in circularity.
- the periphery of the rolling tool (s) is substantially circular (in section straight) or generally cylindrical (relative to an average diameter, in the presence of teeth, or thread).
- the blank can be pre-formed, in particular with teeth, in which case, in principle, the tool or tools are provided with homologous teeth.
- the blank can be pre-formed into a ring, in particular a bearing, in which case, in principle, the tool or tools have a uniform external periphery (not necessarily cylindrical of revolution).
- a terminal phase (d) or 88 of decompression is planned to move the tools away from the room.
- This phase can be conventionally determined in terms of recoil speed, or better controlled, in the form of a decreasing effort in a controlled way.
- the penetration phase or phases take place under servo-control effort.
- a programmed position Xb we end the control when the desired position is reached (86).
- the set can therefore be called servo effort / position (effort then position).
- the process described performs cold forming by rolling a blank in pressed-sintered material, in which at least one geometry tool is approached from the blank pre-determined device, to then roll the tool on the blank while urging them towards each other.
- a phase (a) of approaching the blank the method comprises a penetration phase (b).
- this penetration phase comprises, towards its end (b n ), at least one rolling phase under substantially constant force, to a chosen position, this force, the chosen position, and the number corresponding passages being determined to control the surface densification and the dimensions of the rolled part.
- the substantially constant force can be defined with respect to a critical value, maintained below the deterioration threshold, which can be determined experimentally and / or in another way (for example by extrapolation from similar parts).
- substantially constant is meant a variation which may be of the order of 10% of the critical value. The 10% is preferably taken below the critical value, which can allow the latter to be brought closer to the deterioration threshold, if desired. By that same, one can decrease the rolling time, and, then, have a better control of the work hardening.
- phase (b) can include maintaining the force applied to the blank below a limit value defined in relation to a threshold of deterioration of the pressed-sintered blank.
- the deterioration can be due to a burst of the heart, to a disintegration of the surface, and / or undue hardening.
- the deterioration threshold depends on various factors, such as the constraints acceptable by the blank with regard to the desired conformity for the part finished, as well as the constraints linked to the desired longevity of the tool.
- Phase (b) can also understand the maintenance of the force applied to the roughing at a sufficiently close value of said limit, to avoid excessive strain hardening by minimizing the rolling time (including depends on the production cost).
- there are applications like "burnishing" correctionion of the geometry of a part), where work hardening is less critical, even sought.
- phase of penetration (b) is carried out at least partially under force control.
- the phase (b n ) of rolling under substantially constant force can be preceded by (b 1 ) at least one phase of rise in rolling force, bounded by a maximum value of this force of rolling.
- the increase in effort of phase (b 1 ) is also limited in terms of progression of the effort over time. More precisely still, the increase in force of phase (b 1 ) can be carried out according to a critical law tending to bring the progression closer to an admissible limit value, determined experimentally, taking into account the geometric and mechanical characteristics of the blank and of the finished part. This makes it possible to get closer to the ideal consisting (except in special cases) of carrying out the rise in effort as quickly as the characteristics of the blank and of the finished part can admit.
- the periphery of the tools can be uniform or smooth, in order to form, rings or worn, which is particularly advantageous in pressed-sintered material, since the material can densify, without spreading longitudinally in the direction of the axes A1 and A2, as the would make a massive material.
- it may also take various other predetermined forms: threads, or annular grooves, or straight or helical teeth, in particular, to form grooves, knurling, thread, or a gear.
- the blanks may themselves have shapes from the development pressed-sintered, for example teeth.
- Figures 9A and 9B illustrate general patterns of the force and position curves that can be observed according to the invention.
- Figure 14 is a schematic sectional view which shows the blank EB, and the part ultimately desired PI.
- the area in a single hatched line corresponds to the part of the blank which is not modified by rolling.
- the area in double hatched lines indicates the geometry final part, while the blank is slightly larger, as shown.
- Such a part is known under the name "biconic roller", and can have by example a diameter of 30 mm (draft).
- Such a part can be manufactured by a conventional method, using a servo position (expressed in speed and final position), to obtain an outside diameter final 29.5 mm.
- a servo position expressed in speed and final position
- the same kind of part was prepared by rolling according to the invention, with a servo effort, followed by a final command in position, for superfinishing.
- the variation of the finished diameter is now at most equal to 15 ⁇ .
- the variations in circularity are at most equal to 10 ⁇ .
- the implementation of the invention also results in a variation of the speed of advance tools, depending on the actual strength of the blank during rolling.
- the Applicant has sought conditions corresponding to a reduction in diameter on the sidewall as well as the tooth foot diameter, to reach the diameters fixed to the plane of definition, from preformed blanks of different natures and geometries. It follows variations in the densification thickness.
- a conventional rolling was carried out in position control, in order to obtain a final dimension of 34.50 mm.
- the result was a broken coin, which exploded in multiple fragments.
- the cause analyzed was a dispersion of hardness between drafts. It results in a variable final effort from one room to another, occasionally taking on values too large which produce the above-mentioned case.
- the possible remedy (known as enslavement position) consists in such a case of decreasing the speed of advance. But the result is a time Rolling (or number of parts revolutions) too high, which results in a excessive surface hardening of the blank or part, and a decohesion thereof.
- the force command described can be applied to the rolling of parts according to variable implementations and means, based on current techniques used, or others to come in the field, such as linear motors, for example.
- current techniques used or others to come in the field, such as linear motors, for example.
- Measured variables are not necessarily efforts: we have seen that we can, in particular from pressures, which is only an example not limiting.
- the action quantities are also not necessarily efforts, since we will be able to link them to efforts or forces, with the required precision.
- the invention also covers the essential element which constitutes a program for controlling a numerically controlled machine, for implementing the method, in all of its described variants.
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Abstract
Description
- formage externe de l'ébauche, à l'aide d'un outil, l'ébauche étant tenue par ailleurs, ou bien de deux outils ou plus, régulièrement répartis autour de la périphérie externe de l'ébauche;
- formage interne d'une ébauche creuse, à l'aide d'au moins un outil interne et d'au moins un outil externe, ou d'un support externe tournant avec l'ébauche.
- la figure 1 représente schématiquement une machine de formage à froid, possédant un premier type d'entraínement d'outils,
- la figure 2 représente schématiquement une variante applicable notamment à la machine de la figure 1,
- la figure 3 représente schématiquement une machine de formage à froid, possédant un second type d'entraínement d'outils,
- la figure 4 représente schématiquement et partiellement une machine du même type que celle de la figure 1, mais dans laquelle l'un des outils travaille à l'intérieur d'une ébauche annulaire,
- les figures 5A à 5G illustrent différentes variantes de la disposition géométrique des outils de formage,
- la figure 6 est un schéma de principe d'une commande de machine connue, à maítrise de position,
- la figure 7 est un schéma de principe d'une commande de machine utilisée selon l'invention, à maítrise de force,
- la figure 8 est un diagramme d'étapes illustrant un exemple de mise en oeuvre de l'invention,
- les figures 9A et 9B sont respectivement des diagrammes temporels schématiques de force et de position, dans un exemple d'application de l'invention,
- les figures 10 à 13 sont des diagrammes mesurés, de force et de position, dans différents exemples de mise en oeuvre de l'invention, et
- la figure 14 illustre schématiquement une ébauche et une pièce pour un exemple particulier de roulage.
- entraínement indépendant dans la machine dite H40 CN galetage d'ESCOFIER TECHNOLOGIE,
- entraínement synchronisé dans la machine dite Syncroll d'ESCOFIER TECHNOLOGIE., Le moteur M2 est alors maintenu dans le synchronisme voulu avec le moteur M1, compte-tenu notamment du rapport de synchronisme requis. Ce rapport peut être pris entre la vitesse angulaire ω1 des outils et celle ω2 de l'ébauche, plus exactement pour préserver l'égalité de leurs vitesses tangentielles respectives à leurs diamètres de fonctionnement. S'agissant de profils à dents, on peut prendre un rapport de nombre de dents.
- 2 outils externes tous deux mobiles en translation relative (Figure SA), comme déjà décrit à propos des figures 1 à 3 ;
- 2 outils externes dont l'un O1 est d'axe fixe, et l'autre O2 d'axe mobile en translation (Figure 5B);
- plus de deux outils externes, en principe régulièrement distribués, mobiles en translation relative, par exemple 3 outils (Figure 5C), ou 4 outils (Figure 5D) ;
- un outil interne et l'autre externe, pour une ébauche annulaire (Figure 5E);
- des variantes à un seul outil, qui peut être interne (Figure 5F), l'ébauche étant tenue sur un support EBS mobile en rotation, comme décrit par exemple à propos de la figure 4, ou externe (Figure 5G), l'ébauche étant montée sur un support rotatif.
- les matériaux de la pièce et des outils,
- les formes réalisées,
- les diamètres respectifs de la pièce et des outils (ou autre dimension critique),
- la surface de contact entre la pièce et chaque outil, résultant de la profondeur de pénétration à chaque action ou passe des outils.
- US-A-5,711,187 et US-A-5,884,527 décrivent un ré-usinage superficiel d'engrenages en fritté déjà préformés, en roulage classique, c'est-à-dire sans comporter de préoccupations ni d'enseignements spécifiques en ce qui concerne les conditions du roulage, et leurs conséquences;
- US-A-5,659,955 part également d'ébauches frittées, sur lesquelles il exécute soit un usinage qui progresse en longueur (dans la direction de l'axe de rotation de l'ébauche), soit là aussi un ré-usinage superficiel d'engrenages en fritté déjà préformés, dont le principe est du type "enfilade", sur une machine à entr'axe fixe.
- d'autres brevets, comme US-A-4,708,912 ou encore DE-A-3 140 189 tentent d'appliquer un roulage classique, essentiellement pour l'obtention d'engrenages fortement sollicités.
- le coeur de la pièce en pressé-fritté possède une résistance aux différentes contraintes mécaniques inférieure à celle d'une pièce solide,
- par contre, la pression de surface nécessaire à la déformation va croítre en même temps que la densification périphérique qui résulte de cette déformation, jusqu'à atteindre une valeur proche de celle du matériau solide.
- L'ébauche frittée a toujours des défauts de dimension, de circularité, de concentricité, et d'homogénéité
- La profondeur d'action des outils dans la pièce évolue entre une valeur nulle (contact outils/pièce du début) et une profondeur résultant de leur pénétration progressive au cours de la rotation de la pièce avant que le point de contact d'origine ne rencontre à nouveau les outils (un demi tour de pièce par exemple sur une machine à deux molettes)
- Les parties mécaniques de la machine subissent des déformations variables en relation avec la variation de l'effort de travail.
- pour des opérations spéciales, comme le galetage, ou encore,
- lorsque le cycle roulage d'une ébauche contient plusieurs sous-cycles, avec ou sans inversion du sens de rotation entre sous-cycles, pour les sous-cycles qui précèdent le sous-cycle final.
- figure 10 : approche (a0 , a1) semi-rapide, montée en effort (b1) rapide, roulage (b2) sous effort sensiblement constant, pas de phase (c), phase (d) très courte;
- figure 11 : se distingue de la figure 10 par une approche (a0 , a1) plus rapide, montée en effort (b1, b2) en deux temps, d'abord lente, puis plus rapide; roulage (b3) sous effort sensiblement constant, pas de phase (c), phase (d) très courte;
- figure 12 : se distingue de la figure 11 par une approche (a0 , a1) encore plus rapide; la montée en effort (b1, b2) est aussi en deux temps, avec des taux différents ; la phase (c), présente un effort globalement décroissant, mais avec des fluctuations dues, en présence d'un entr'axe fixe, aux imperfections géométriques, légères mais inévitables, au contact outil/pièce, notamment quant à la circularité de la pièce (avec deux outils, une zone donnée de la pièce rencontre un outil deux fois par tour);
- Figure 13 : généralement semblable à la figure 10, mais avec un dédoublement en deux parties 1a0 à 1d, et 2a0 à 2d ; une inversion du sens de rotation des outils peut être effectuée entre les deux parties, au début de 2a0. Autrement dit, les phases (a) d'approche et (b) de pénétration sont réitérées après inversion du sens de rotation du ou des outils. Ceci peut être fait plusieurs fois.
- le temps (c'est-à-dire le nombre de révolutions de la pièce ou ébauche) sera augmenté ;
- une sécurité peut stopper la machine si le cycle devient trop long ;
- les outils ne cassent pas.
- deux moteurs respectifs pour entraíner les outils O1 et O2, avec ou sans liaison mécanique entre leurs réducteurs,
- deux moteurs pour entraíner les systèmes vis/écrou BSD1 et BSD2 sur la figure 3, deux vérins pour déplacer les deux chariots F1 et F2 par rapport au bâti B sur les figures 1 et 2,
- adaptations pour des machines à 3 outils ou plus.
Claims (15)
- Procédé de formage à froid par roulage d'une ébauche en matériau pressé-fritté, dans lequel on approche de l'ébauche au moins un outil de géométrie périphérique pré-déterminé, pour faire rouler ensuite l'outil sur l'ébauche en les sollicitant l'un vers l'autre, caractérisé en ce qu'il comprend, après une phase (a) d'approche de l'ébauche, une phase de pénétration (b), avec:(bn) au moins une phase de roulage sous effort sensiblement constant, jusqu'à une position choisie, cet effort, la position choisie, et le nombre de passages correspondant étant déterminés pour contrôler la densification de surface et les dimensions de la pièce roulée.
- Procédé selon la revendication 1, caractérisé en ce que la phase de pénétration (b) s'effectue au moins partiellement sous asservissement en effort.
- Procédé selon l'une des revendications 1 et 2, caractérisé en ce que la phase (bn) de roulage sous effort sensiblement constant est précédée de :(b1) au moins une phase de montée en effort de roulage, bornée par une valeur maximum de cet effort de roulage.
- Procédé selon la revendication 3, caractérisé en ce que la montée en effort de la phase (b1) est également bornée en termes de progression de l'effort dans le temps.
- Procédé selon l'une des revendications 3 et 4, caractérisé en ce que la montée en effort de la phase (b1) est effectuée selon une loi critique tendant à rapprocher la progression d'une valeur limite admissible, déterminée expérimentalement, compte-tenu des caractéristiques géométriques et mécaniques de l'ébauche et de la pièce finie.
- Procédé selon l'une des revendications 1 à 5, caractérisé en ce que la phase (b) comprend le maintien de l'effort appliqué à l'ébauche sous une valeur limite définie par rapport à un seuil de détérioration de l'ébauche pressée-frittée et/ou des outillages.
- Procédé selon la revendication 6, caractérisé en ce que la phase (b) comprend le maintien de l'effort appliqué à l'ébauche à une valeur suffisamment voisine de ladite limite, pour éviter un écrouissage excessif en minimisant le temps de roulage.
- Procédé selon l'une des revendications 1 à 7, caractérisé en ce que les phases (a) d'approche et (b) de pénétration sont réitérées après inversion du sens de rotation du ou des outils.
- Procédé selon l'une des revendications précédentes, caractérisé en ce qu'il comprend en outre:(c) une phase de finition dans laquelle on maintient sensiblement constante la position relative ébauche/outil pendant un temps choisi.
- Procédé selon l'une des revendications précédentes, caractérisé en ce que la périphérie du ou des outils est sensiblement circulaire ou globalement cylindrique.
- Procédé selon l'une des revendications précédentes, caractérisé en ce que l'ébauche est pré-formée, en particulier avec des dents.
- Procédé selon la revendication 11, caractérisé en ce que le ou les outils sont munis de dents.
- Procédé selon l'une des revendications 1 à 10, caractérisé en ce que l'ébauche est pré-formée en bague, notamment de roulement.
- Procédé selon la revendication 13, caractérisé en ce que le ou les outils ont une périphérie externe uniforme.
- Programme pour piloter une machine à commande numérique, pour la mise en oeuvre du procédé selon l'une des revendications précédentes.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0206980 | 2002-06-06 | ||
FR0206980A FR2840552B1 (fr) | 2002-06-06 | 2002-06-06 | Formage a froid par roulage de pieces en materiau presse-fritte |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1369193A1 true EP1369193A1 (fr) | 2003-12-10 |
Family
ID=29433336
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP03076687A Withdrawn EP1369193A1 (fr) | 2002-06-06 | 2003-06-02 | Formage à froid par roulage de pièces en matériau pressé-fritté |
Country Status (3)
Country | Link |
---|---|
US (1) | US6729171B2 (fr) |
EP (1) | EP1369193A1 (fr) |
FR (1) | FR2840552B1 (fr) |
Families Citing this family (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2003285135A (ja) * | 2002-03-26 | 2003-10-07 | Minebea Co Ltd | ねじ転造盤 |
WO2004082872A2 (fr) * | 2003-03-18 | 2004-09-30 | The Penn State Research Foundation | Procede et appareil de renforcement d'engrenages a base de metal pulverulent par ecrouissage de l'austenite avant trempe |
US7267024B2 (en) * | 2003-05-21 | 2007-09-11 | O-Oka Corporation | Gear, and method and apparatus for manufacturing the same |
DE10341156A1 (de) * | 2003-09-06 | 2005-03-31 | Ina-Schaeffler Kg | Maschinenelement |
DE102004056921A1 (de) * | 2004-11-25 | 2006-06-01 | Kamax-Werke Rudolf Kellermann Gmbh & Co. Kg | Verfahren und Vorrichtung zum Präzisionsrollen von rotationssymmetrischen Bauteilen |
DE102005027144A1 (de) * | 2005-06-10 | 2006-12-14 | Gkn Sinter Metals Gmbh | Oberflächenverdichtung einer Verzahnung |
DE102005027142A1 (de) * | 2005-06-10 | 2006-12-14 | Gkn Sinter Metals Gmbh | Vorformgeometrie einer Verzahnung |
DE102005027054A1 (de) * | 2005-06-10 | 2006-12-28 | Gkn Sinter Metals Gmbh | Werkstück mit unterschiedlicher Beschaffenheit |
DE102005027049A1 (de) * | 2005-06-10 | 2006-12-14 | Gkn Sinter Metals Gmbh | Belastbare Verzahnung |
DE102005027137A1 (de) * | 2005-06-10 | 2006-12-14 | Gkn Sinter Metals Gmbh | Verzahnung aus Sintermaterial |
AT505118B1 (de) * | 2007-03-28 | 2013-03-15 | Miba Sinter Austria Gmbh | Verfahren zur bearbeitung einer verzahnung an einem sinterteil |
US20080282544A1 (en) * | 2007-05-11 | 2008-11-20 | Roger Lawcock | Powder metal internal gear rolling process |
CN112958769A (zh) * | 2021-01-29 | 2021-06-15 | 向朝霞 | 一种利用径向滚压方式生产双金属滑动轴承的制造方法 |
Citations (2)
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GB1186951A (en) * | 1968-05-24 | 1970-04-08 | Ostrander Seymour Co | Improvements in or relating to Dimensional Control Systems |
GB2098901A (en) * | 1981-03-18 | 1982-12-01 | Deutsche Ind Anlagen | Roll forming a workpiece |
Family Cites Families (10)
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US3874049A (en) * | 1973-04-13 | 1975-04-01 | Burdsall & Ward Co | Method of making a powdered metal part having a bearing surface |
US4059879A (en) * | 1975-11-17 | 1977-11-29 | Textron Inc. | Method for the controlled mechanical working of sintered porous powder metal shapes to effect surface and subsurface densification |
US4111031A (en) * | 1977-09-09 | 1978-09-05 | General Motors Corporation | Powder metal crown gear forming process |
DE3140189A1 (de) | 1981-10-09 | 1983-04-28 | Helmut 4030 Ratingen Eichhorn | Scheibe fuer synchronriemengetriebe und ihre herstellung |
US4708912A (en) | 1984-07-18 | 1987-11-24 | Sintermetallwerk Krebsoege Gmgh | Sintered metal body with at least one toothing |
US5711187A (en) | 1990-10-08 | 1998-01-27 | Formflo Ltd. | Gear wheels rolled from powder metal blanks and method of manufacture |
US5659955A (en) | 1994-01-21 | 1997-08-26 | Plamper; Gerhard | Method of making powder metal helical gears |
AT405494B (de) * | 1996-02-14 | 1999-08-25 | Miba Frictec Gmbh | Verfahren zum herstellen einer ebenen reiblamelle |
US6151941A (en) * | 1999-01-25 | 2000-11-28 | Federal-Mogul World Wide, Inc. | Apparatus and method for roll forming gears |
DE19950595C1 (de) * | 1999-10-21 | 2001-02-01 | Dorn Gmbh C | Verfahren zur Herstellung von Sinterteilen aus einer Aluminiumsintermischung |
-
2002
- 2002-06-06 FR FR0206980A patent/FR2840552B1/fr not_active Expired - Fee Related
- 2002-06-24 US US10/176,618 patent/US6729171B2/en not_active Expired - Fee Related
-
2003
- 2003-06-02 EP EP03076687A patent/EP1369193A1/fr not_active Withdrawn
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1186951A (en) * | 1968-05-24 | 1970-04-08 | Ostrander Seymour Co | Improvements in or relating to Dimensional Control Systems |
GB2098901A (en) * | 1981-03-18 | 1982-12-01 | Deutsche Ind Anlagen | Roll forming a workpiece |
Also Published As
Publication number | Publication date |
---|---|
US20030226386A1 (en) | 2003-12-11 |
US6729171B2 (en) | 2004-05-04 |
FR2840552A1 (fr) | 2003-12-12 |
FR2840552B1 (fr) | 2005-02-18 |
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