FR2941638A1 - Method for forming fatty edge in part with thin wall in e.g. construction, involves carrying out flow drilling of material of part for suppressing side of rear face opposite to support surface and forming fatty edge around opening - Google Patents

Abstract

The method involves carrying out boring operation, at emplacement of a fatty edge (7), on a support surface (5). Flow drilling of the material of a part (2) is carried out for suppressing a side of a rear face opposite to support surface and forming the fatty edge around an opening (10), where the part is made of a light alloy, plastic material, and honeycomb or composite material. An inlet radius (9) of the opening is shaped during or after the flow drilling of the material. An independent claim is also included for a ceramic flow drill tool made of a material e.g. zirconium oxide and yttrium oxide nuance ceramic, and comprising a nose cone.

Description

The invention relates to a method of generating a bead in a thin-walled part, made of light alloy or plastic, or honeycomb, or composite material, or the like.

The invention further relates to a method of manufacturing tapping in a thin-walled part, in particular light alloy, designed tapping adapted to receive an insert such as a threaded insert. The invention also relates to a fluoperceur tool for implementing such a method. The present invention is in the field of machining thin-walled parts, that is to say of the order of a few tenths of a millimeter to a few millimeters thick, the destination of which requires to receive threads of large diameter relative to the local thickness of the wall, especially more than triple or quadruple. The invention relates more particularly to the field of machining thin parts made of light alloys, copper alloys, plastics, walls with a honeycomb structure, or other materials with a low elastic limit. Such thin parts are common in aeronautical constructions, automobile construction, shipbuilding, or building joinery. Their reversible assembly generally requires screw connections. The hardware elements must have a certain section to provide sufficient strength to the assembled assembly. It is then a question of adapting the dimensioning of the connection machining intended to receive these elements of fasteners, according to their dimensions.

It is most of the time necessary to make tappings able to cooperate with the screw thread. Because of the diameter of the latter and the game, that of the threads is determined. It is, in the case of thin-walled parts, important in relation to the local wall thickness, especially more than triple or quadruple, or more. The threads are standardized. It is understood that it is impossible to provide a proper support on a portion of net only, which would be the case if one was satisfied with tapping, the tool, the thin-walled part to receive the screw. It was therefore imagined inserts to ensure sufficient cooperation between the screw and the tapping that receives, on several revolutions. It is, moreover, necessary to strengthen the tapping intended to receive the screw: a tapping performed directly in a thin piece of aluminum alloy or plastic can not receive a steel screw for example, which will be mounted and disassembled in time, without being very quickly, and even often at first time, worn or unusable. Rigid inserts are known which locally reinforce the thickness of the thin-walled piece, in the manner of bosses, and provide, thanks to the choice of a material with a higher elastic limit, a good resistance. This solution is not acceptable when the bearing surface of the mounting components must remain unobstructed. It is then necessary to accommodate the part of the insert intended to ensure the adequate length of the thread, behind this surface. Such rear mounting is generally not possible in the case of a blind part, where one can only access one side to machine or mount components. The case of large parts can also affect the mounting of inserts or nets, preventing access or positioning tools specific to their installation. Another solution, less cumbersome than the rigid insert, is the threaded insert, which is a flexible helical component, generally made of steel, in particular stainless, in the manner of a spring, which is housed in a tapping, and which provides the resistance qualities desired while having a very small footprint. However, such an added thread requires a guide length at least equal to the screw length. Furthermore, for a perfect fit, the part must have a bearing surface perpendicular to the axis of the tapping. But the standards of use, for example in aeronautics, make mandatory the installation of such threads reported in all threads. It has still been imagined pegs similar to those used in the building, including expansion type ankle. But these ankles generate, their pose, significant deformations of the wall of the room, which makes them in most cases unusable. To ensure a length of material allowing, locally, machining a tapping, it has been further conceived to repress the material, in the manner of what is used on steel parts, to form a bead on the opposite side to the support surface. Tests made with tools designed for steel do not make it possible to make beads of controlled geometry: often the beads are burst, and are therefore unfit to receive a thread for a screw. In addition the beads are not regular, and it can not ensure, over the desired length of screwing required, the minimum thickness of material to make a tapping under acceptable conditions. A major disadvantage of fluoperchant carbide tools is the essential use of lubricants under high pressure, creating a paste that requires thorough cleaning of the room before any other use.

It is understood, again, that the technique used can not be random, in fact a badly machined part can become irreparable and sentenced to waste. The invention proposes to provide a method for tapping thin-walled parts, made of light alloy or plastic, or honeycomb, or composite material, or the like, for installing inserts such as nets reported. This method is based on the preparation, on the face opposite to the bearing surface, of a bead whose creep is controlled to ensure, on the desired screwing length, the bead section sufficient to achieve tapping without tearing neither bursting of the material, and under which there remains a sufficient thickness of material for the proper maintenance of a screw, or, preferably, of an added thread for receiving a screw, and thus overcome the disadvantages of the state of the technique. To this end, the invention relates to a method of generating a bead in a thin-walled part, made of light alloy or plastic, or honeycomb, or composite material, or the like, characterized by the fact that: - is carried out on a first surface, said bearing surface, a pointing at the location of said bead; the material of said workpiece is impregnated so as to discharge it on the side of a rear face opposite to said support surface and form a bead around an orifice. According to a characteristic of the invention, during or after said flow of said bead, the forming of an input radius of said orifice on the side of said bearing surface is carried out.

The invention further relates to a method of manufacturing tapping of useful length given in a thin-walled part, light alloy or plastic, or honeycomb, or composite material, or the like, designed tapping suitable for to receive an insert such as an added thread, characterized in that: - it implements such a method for making a bead length greater than or equal to said desired working length, said pointing being located at the location of said tapping; machining said tapping in said bead. According to one characteristic of the invention, the tapping of said tapping is carried out by tapping. According to another characteristic of the invention, said flow of said bead is carried out with a fluopercer ceramic tool. According to another characteristic of the invention, said cold-forming of said tapping is carried out with a ceramic tapping tool.

According to another characteristic of the invention, a lubricant is chosen comprising an extreme pressure additive containing jojoba oil. The invention also relates to a fluoperceur tool for the implementation of such a method, characterized in that it is made of ceramic material, and comprises a designed ogive adapted to perform the fluo-drilling, and the opposite side to the tip said warhead, at least one designed radiated zone capable of performing a cutting operation or deformation of a connection radius.

Other features and advantages of the invention will emerge from the following detailed description of non-limiting embodiments of the invention, with reference to the appended figures in which: FIG. 1 is a diagrammatic sectional representation of FIG. a bead obtained after the implementation of a fluoperceur tool; - Figure 2 shows, schematically and in section, the bead of Figure 1 after tapping by deformation; - Figure 3 shows, schematically and in section, the thread of Figure 2, equipped with a threaded insert; - Figure 4 shows, schematically and in elevation, a fluo-drilling tool for the implementation of the invention, mounted on a specific tool holder. The invention relates to a method for generating a bead in a thin-walled part made of a light alloy or a plastic material, or a honeycomb, or a composite material, or the like, characterized in that: performing a pointing at the location of said bead on a first surface, said bearing surface; the material of said workpiece is impregnated so as to discharge it on the side of a rear face opposite to said support surface and form a bead around an orifice. The invention further relates to a method for manufacturing tapping of useful length given in a thin-walled part, light alloy or plastic, or honeycomb, or composite material, or the like, designed tapping suitable for to receive an insert such as an added thread, characterized in that: - it implements such a method for making a bead length greater than or equal to said desired working length, said pointing being located at the location of said tapping; - Machining said tapping in said bead. A first embodiment of the invention is illustrated in the figures.

The invention relates to a method of manufacturing tapping 1 of useful length L given in a thin walled piece 2, in particular of light alloy. This tapping is designed to receive an insert 4 such as a threaded insert. According to the invention, the following steps are carried out in this order: - on a first surface 5, said support surface, a pointing at the location of said tapping 1; a flow of the material of said piece 2 is carried out, to push it back towards a rear face 6 opposite to said bearing surface 5 and to form, around an orifice 10, a bead 7 of greater or equal length to the desired length L desired; the machining of said tapping 1 is carried out in said bead 7.

The score can also be completed by a coining. The essential thing is that the work surface for the docking of a fluoperceur tool 50 carrying out the flow is clean and regular. It will be understood that it is possible to carry out material-blowing, or, preferably, directly with a fluoperchant tool 50, or from a pre-existing or pre-machined hole. The choice of the procedure depends on the nature of the material that is deformed to make the bead, as well as its thickness. Advantageously, it is preferable during the perforation of said bead, or after the latter, the forming of a radius 9, preferably convex, at the inlet of said orifice 10, on the side of said bearing surface 5. In a particular embodiment, after the flow of the bead 7 as visible in FIG. 1, it is possible to dress the bearing surface 5 perpendicularly to an axis Z which is that of the tapping 1, to produce a surface of FIG. support erected. Advantageously, a convex radius 9 of junction between this upright support surface and the orifice 10 of the bead 7 resulting from the flow-through is also performed. In a preferred manner, the flow of the bead 7 is effected with a fluoperchant tool 50 made of ceramic. However, it is not possible to use any technical ceramic for the fluoiling of light alloys, in particular aluminum-based alloys. This is why, according to the invention, because of the quality of the binder provided by the ytrium which composes it, it chooses a ZrO 2 YO 3 grade ceramic, of which it is the first application in a deformation tool. usually used for making cutting tools and mechanical parts. This ceramic ZrO2YO3 can be used in the case of the deformation of aluminum alloys to dry, the alumina serving as lubricant. It can also, as discussed below, be used with certain very specific types of lubricants, chosen to prevent any thorough cleaning of the machined part 2 before its subsequent use. According to a new and inventive feature of the invention, machining of the tapping 1 is carried out by tapping. This application is known only on thick-walled parts made of high-yielding material such as steel. However, in the context of the invention, the use of a ceramic fluopercer tool 50 in the ZrO2 Y03 grade makes it possible to develop a sufficiently regular bead 7, with respect to the decrease of its diameter and of its section, in order to be able to ensure a sufficient section at any point of the useful travel L, to allow the return of the material, without risk of tearing. The fluoperceur tool 50 has a centering tip 60.

In a particular embodiment, the fluoperchant tool 50 is selected with at its tip 60 at least one cutting portion 51 designed capable of performing a centering operation on the bearing surface 5. This cutting part 51 can in particular be made under form of a tool steel or tungsten carbide insert or the like, housed in a housing that comprises the fluoperceur 50. In another version, the fluoperceur 50 tool has no cutting portion 51, but only one guide tip, which is used to guide the fluoperchant tool 50 in a centering made by another tool upstream, such as a center drill or the like. As can be seen in FIG. 4, the fluoperchant tool 50 comprises, in revolution along an axis Z ', downstream of its end tip 60 or of its cutting part 51, a warhead 52 making it possible to carry out the formation flow and the formation bead 7, comprising, or possibly extended by, a calibration zone 53 cylindrical or very low taper, that is to say less than 5%, and preferably less than 2%, and, on the other hand, opposite the tip 60 of said warhead 52, at least one radiated zone 55 designed capable of performing a cutting operation or deformation of a connecting radius. The fluoperchant tool 50 may further comprise, on the opposite side to the tip of said warhead 52, at least one cutting portion 54 designed capable of performing a dressing operation on the bearing surface 5. The junction between the calibration zone 53 and the cutting part 54 is preferably made according to a radiated area 55 for the execution of a connecting radius 9 between the orifice 10 of the bead 7 and the upright support face 8. The fluoperchant tool 50 can also, in a simplified version, comprise, on the opposite side to the tip of the nose 52, only such a radiated area 55, allowing the execution of a connecting radius 9, either by deformation of the material, or by cutting . The cutting portion 54 is preferably located at the level of at least one lip, preferably at least two to balance the force and maintain the centering, which comprises the fluoperceur tool 50. The radiated area 55 is preferably of revolution. It will be noted, again, that at least the warhead 52 may comprise a plurality of radially-sectioned lips without a sharp angle extending in planes passing through the axis Z ', in order to provide a hammering effect at high speed, which can make it possible to improve the surface hardening and the superficial hardness of the bead 7 formed by its action. It is still possible to equip the calibration zone 53 with such lips, however making this zone in smooth form gives very good results, which reduces its cost. Moreover, in a particularly economical execution while being very reliable, the warhead 52 is also smooth.

The use of the method according to the invention, and of such a fluoperceur tool 50, make it possible to obtain a bead 7 having an evolutionary section in a regular manner, while having a high height, of the order of magnitude of the diameter of the orifice 10 or more, which presents a great advantage for the proper maintenance of an insert or an added thread, and a good resistance at the neck of such a net reported, if it comprises a. In a preferred and innovative way, the tapping of the tapping 1 is carried out with a ceramic tapping tool, designed to discharge the material without risk of tearing, as can be seen in FIG. 2. This tapping tool is not shown. in the figures, in a preferred embodiment, it has no straight edge contrary to a cutting tap, and has a multilobal cross section.

Preferably, one chooses said tapping tool to push ceramic ZrO2 Y03 grade, for the same reasons of choice as for fluoperceur 50. The fluoperceur 50 tool, like the tap tool to repress, is advantageously mounted on a special tool holder, as shown in Figure 4. Figure 3 illustrates the mounting of an insert 4, in the form of a threaded steel net 40 mounted in the tapping 1. The mounting of such threaded nets requires a a certain number of machining precautions: the good calibration of the tapping 1 is ensured by the tap tool to be discharged, and the prior machining of a regular connection radius 9 is essential for a good mounting of such threads 40. last machining of the spoke 9 is optionally completed by the dressing of a bearing face.

The fluo-piercing operations, both for forming the bead 7 and for machining the tapping 1, can be carried out dry, without lubrication. The tapping operation, whatever the tool used, is always a delicate operation, and which is generally not repairable in case of default, including tearing. One of the aims of the invention is to provide machining means which make it possible to guarantee the execution of a very large number of machining operations in a perfectly reproducible manner, in complete safety. Also it was searched for an alternative solution, offering a better security than the fluo-drilling, or especially the dry cold-working. Also, according to a particular characteristic of the invention, the flow-forming is carried out for the formation of the bead 7, and / or the cold-working for the execution of the tapping 1 under lubrication, by choosing a lubricant comprising an extreme pressure additive, in particular containing jojoba oil. According to the work of the same inventor, tests of 100% pure jojoba oil have given excellent results, for the deformation of light alloys, cuprous, stainless steels or titanium alloys. Preferably, a lubricant comprising at least 20% jojoba oil is chosen. In a particular embodiment of the invention, a lubricant comprising at least 98% jojoba oil is chosen. Preferably, such a lubricant is chosen in the IMCT LUBE range developed by the same inventor and comprising at least 20% of jojoba oil, or at least 98% of jojoba oil. The lubrication by deposition or vaporization of jojoba oil, or IMCT LUBE oil comprising jojoba oil, or a composition with a high content of jojoba oil, preferentially more than 95%, allows the proper conduct of the process, in particular of the cold-working. If the invention has been designed preferentially for the fields of light alloys, plastics, honeycombs, or composite material, it is perfectly usable for other materials, especially steels, stainless steels, copper alloys, or others. One of the advantages of the invention is to allow the installation of threaded inserts on thin parts, in materials of limited elastic low, as well as in hollow bodies such as honeycomb structures. The tests carried out demonstrate the good suitability, of the process and the means used, for light alloys of aluminum or titanium, for copper, in particular for brass, as well as for plastics, resins, composites, sandwich materials, and like. The making of an orifice surrounded by a bead of great length, that is to say of the same order as the diameter of the orifice, by the flow of the invention allows variations of use for cases not requiring no tapping, for example for riveting, or other. The implementation of the process of fluo-drilling and cold-forming according to the invention makes it possible, again, to perform in good conditions the repair of a part of which a tapping was damaged, by proceeding to a flow to create a bead of diameter superior, then a cold forming and the installation of an insert or a net dimensionad hoc. Of course, the invention is not limited to the examples illustrated and described above which may have variants and modifications without departing from the scope of the invention.

Claims (13)

REVENDICATIONS1. A method of generating a bead (7) in a thin wall (3), light alloy or plastic, or honeycomb, or composite material, or the like, characterized by the fact that: - is carried out on a first surface (5) support, a pointing at the location of said bead (7); a flow of the material of said part (2) is carried out, to push it back on the side of a rear face (6) opposite to said bearing surface (5) and to form a bead (7) around an orifice (10). 2. Method according to claim 1, characterized in that, during or after said flow of said bead (7), the forming of an input radius (9) of said orifice (10), on the side of said bearing surface (5). 3. Method according to one of the preceding claims, characterized in that said fluoping said bead (7) with fluoperceur tool (50) having a ogive (52) for performing the flow, said ogive (52) having a tip (60) adapted to perform a centering operation, and on the opposite side to said tip (60) of said warhead (52), at least one radiated area (55) adapted to perform a cutting operation or deformation of a connection radius (9). 4. Method according to the preceding claim, characterized in that one chooses said fluoperceur tool (50) ceramic, or ceramic ZrO2 grade Y03. 5. Method for manufacturing tapping (1) of given useful length (L) in a piece (2) with thin wall (3), light alloy or plastic, or honeycomb, or composite material , or the like, tapping (1) adapted to receive an insert (4) such as an added thread (40), characterized in that: - the method of bead generation (7) according to the invention is used; one of claims 1 to 4 for making a bit (7) of length greater than or equal to said desired working length (L), said pointing being located at the location of said tapping (1); - Machining said tapping (1) in said bead (7). 6. Method according to the preceding claim, characterized in that it performs the machining of said tapping (1) by cold forming. 7. A method according to claim 5 or 6, characterized in that one carries out the machining of said tapping (1) by cold-forming under lubrication, and that one chooses a lubricant comprising an extreme pressure additive containing jojoba oil . 8. Method according to one of claims 5 to 7, characterized in that it carries out the machining of said tapping (1) by cold forming with a tapping tool to push ceramic, or ceramic grade ZrO2 Y03. 9. fluoperceur tool (50) for carrying out the method according to any one of the preceding claims, characterized in that it is made of ceramic material, and comprises a nose (52) designed capable of performing the flow, said warhead (52) having a tip (60) designed to perform a centering operation, and, on the opposite side to said tip (60) of said warhead (52), at least one radiated area (55) designed adapted to perform a centering operation cutting or deforming operation of a connecting radius (9). 10. fluoperceur tool (50) according to the preceding claim, characterized in that said warhead (52) comprises, or is extended by, a calibration zone (53) cylindrical or conicity less than 5%. 11. fluoperceur tool (50) according to claim 9 or 10, characterized in that it comprises at least one cutting portion (54) designed capable of performing a dressing operation on a bearing surface, and which is joined to said radiated area (55). 12. fluoperceur tool (50) according to one of claims 9 to 11, characterized in that said warhead (52) comprises a plurality of radially sectioned lips without sharp angle extending in planes passing through an axis (Z ' ) which is that of said warhead (52), to provide a high speed hammering effect, designed to improve the surface hardening and surface hardness of a bead (7) formed by its action. 13. fluoperceur tool (50) according to the preceding claim, characterized in that it is made of ceramic material grade ZrO2 Y03.