Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B11/00—Apparatus or processes for treating or working the shaped or preshaped articles
  • B28B11/18—Apparatus or processes for treating or working the shaped or preshaped articles for removing burr
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B19/00—Single-purpose machines or devices for particular grinding operations not covered by any other main group
  • B24B19/14—Single-purpose machines or devices for particular grinding operations not covered by any other main group for grinding turbine blades, propeller blades or the like
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B9/00—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor
  • B24B9/02—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground
  • B24B9/06—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground of non-metallic inorganic material, e.g. stone, ceramics, porcelain

Definitions

• the present invention relates to the finishing of parts obtained by injection of a ceramic paste into a mold formed of the assembly of at least two parts, along a joint plane.
• the invention relates more particularly to the elimination of burrs in the area of the joint plane of the two parts.
• the invention relates to ceramic cores used in the manufacture of hollow turbine engine blades by the lost wax foundry technique.
• foundry cores of a type called “ceramic” is particularly known in certain applications that require the achievement of a set of characteristics and stringent quality criteria such as resistance to high temperatures, lack of reactivity , dimensional stability and good mechanical characteristics.
• these applications having such requirements there are known aeronautical applications and for example the foundry turbine blades for turbojet engines.
• the refinement of foundry processes from the foundry known as equiaxed to the foundry by directed solidification or monocrystalline has further increased these requirements for cores whose use and complexity are imposed by the search for high performance for parts to obtain, as is the case for example for hollow vanes with internal cooling.
• the complex crystalline structure sought in the dawn is not compatible with the burrs on the core. These can become detached during casting and pollute the room by creating inclusions and / or geometric defects. A burr that stays in place creates a crack in the room and therefore a breakaway. The cores must therefore be deburred.
• a method, for deburring a ceramic casting core obtained by injection of a ceramic paste, said paste comprising a binder with a determined glass transition temperature, in a mold and having at least one a surface portion with a surplus of material forming a flash to be eliminated characterized in that it comprises the following steps: a. arranging and fixing the molded foundry core, before baking, on a support, b. place an elongated milling tool with a helical cutting edge on a tool holder, c. rotating the tool about its axis and bringing the milling tool into contact with said surface portion to be deburred, d. cooling the surface portion to be deburred so as to maintain it at a temperature below said glass transition temperature during the deburring operation.
• the invention by deburring before firing the foundry core, it avoids the problem of dimensional variation of the core and opens the possibility of carrying out this operation by means of a controller. Automation ensures a better repeatability of deburring from one core to another. This results in a better deburring quality and a reduction in room breakage. Better kernel quality also reduces crack initiation. The result is a reduction in manufacturing cycles, which reduces costs.
• an angle-propeller milling tool of between 20 and 70 ° and a hemispherical end is used.
• the cut material is dragged away from the cutting area, reducing the risk of jamming.
• the cutting parameters are,
• the cooling is provided by diffusion of a fluid towards the surface portion to be deburred. This is for example air.
• the method is particularly suitable for deburring ceramic cores of turbomachine blades. It makes it possible in particular to reduce the creep primers of the cast products.
• a device for finishing ceramic cores of casting parts comprising a support for said core, a mandrel forming a tool-holder rotatable about its axis and at least one nozzle of injection of cooling fluid.
• FIG. 1 represents the diagram of a turbomachine blade core
• FIG. 2 represents the core of FIG. 1 at the outlet of the injection mold with the flash to be eliminated
• FIG. 3 shows a milling cutter during deburring of the core
• FIG. 4 shows the diagram of a cutter deburring position of a piece of ceramic material
• FIG. 5 shows a device according to the invention.
• FIG. 1 represents an exemplary piece consisting of a core element for a hollow turbine engine blade.
• the envelope of this element 10 has the shape of the internal cavity of the hollow blade once it has been melted.
• the element 10 comprises an upper portion 10A which will constitute the designated bath part of the blade. This part is separated from the central body 10B by a space which will constitute the transverse upper wall of the hollow blade.
• This central portion 10B is extended downwardly by the foot 10D which is used for gripping and fixing the core in the shell mold in which the molten metal is cast.
• the central portion is hollowed out with longitudinal openings 10B 'which will constitute the internal partitions defining the circuit of the cooling fluid to inside the dawn cavity.
• the part 1OB extends laterally on one side by a part of the trailing edge 1OC finer and having openings 1OC which will constitute partitions between them channels that open along the trailing edge of the blade for evacuation coolant.
• the core is intended after casting of the metal and its cooling to be removed to release the circulation cavity of the cooling air of the blade.
• This piece is obtained by injection of a ceramic paste using a press.
• the paste is obtained by mixing a binder, an organic polymer, and particles of ceramic materials.
• the mixture is injected by means of injection presses, such as screw injection presses, into a metal injection mold.
• This mold is formed of an assembly of at least two elements with cavity which are brought into contact with each other along a junction surface which is commonly referred to as joint plane.
• joint plane a junction surface which is commonly referred to as joint plane.
• the paste gradually spreads from the inlet to the volume formed by the fingerprints. However material passes and infiltrates between the surfaces of the joint plane. When demolding, this excess material forms the burrs.
• FIG. 2 shows the appearance of the core of FIG. 1 at the outlet of the injection mold.
• burr Bl which runs along the contour of the nucleus.
• Another burr B2 is visible along the inner edges of the recesses 10C in the trailing edge area 1OC.
• a burr B3 is also seen along the edges of the recesses 10B 'in the area 10B.
• the rest of the process of manufacturing the core consists, after the injection, to unmold the core, bake it in a furnace at high temperature, then to ensure its finishing and dimensional control.
• the purpose of the finish is to remove the burrs B1, B2, B3. They can be removed either just after the injection of the mixture, it is a deburring before cooking or after cooking it is then a deburring core in the cooked state.
• the material is removed before firing, on the part after injection of the polymer-ceramic mixture in order to eliminate said problems related to the deformation of the part during and after firing.
• the method of the invention defines core cutting parameters taking into account the intrinsic properties of the material thereof.
• polyethylene glycol for example, has properties that can change in the vicinity of room temperature, in particular it tends to soften. This causes, when attacking the material forming the burr with a conventional milling, stuffing material. This material jam eventually prevents the removal of the burr.
• a helical bur is used, that is to say with a longitudinal cutting edge in the form of a helix.
• FIG. 3 shows the mode of application of the cutter 100 which is guided along the edge of the piece 10 comprising a burr.
• the material constituting the burr B is cut by the cutting edge 100B in the form of a longitudinal helix. By this helical shape is avoided material jams along the mill 100. The material is removed continuously and the chips removed.
• the inclination of the helix is defined by a helix angle ⁇ of between 20 and 70 degrees preferably between 35 and 65 degrees.
• the diameter of the cutter suitable for this operation given the narrow spaces formed by the recesses is between 0.5 and 1 mm.
• the end of the cutter is preferably hemispherical.
• the material constituting the flash is maintained at a temperature below the glass transition temperature.
• One way is to provide nozzles that expel cool air towards the end of the moving cutter.
• the temperature is maintained between 16 and 26 ° C.
• the tool is rotated on itself along the burr to be eliminated.
• the cutting and feed speeds are adapted to the profile. For example they differ between the contour and the pocket of the core or the grooves at the exit of the trailing edge.
• the illustrative cutting speed is between 5 and 25 m per minute and the feed rate is between 400 and 1800 mm per minute.
• FIG. 4 shows the relative arrangement of the tool with respect to the part.
• the piece 10 is fixed on a support 300 so as to make its contour accessible to a cutter 100 itself mounted on a mandrel 200 forming a tool holder.
• the air injection nozzle 400 or any other suitable cooling fluid is directed on the surface of the portion of the workpiece to be deburred.
• Figure 5 shows a deburring device.
• the mandrel 200 is secured to a rotating support 210 which itself can be mounted on a milling machine, not shown, with three axes for example.
• a fixed plate 220 serves to support the nozzle 400 via a bracket 410 adjustable in position. The plate may have several nozzles as needed.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Inorganic Chemistry (AREA)
• Structural Engineering (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Turbine Rotor Nozzle Sealing (AREA)
• Devices For Post-Treatments, Processing, Supply, Discharge, And Other Processes (AREA)
• Milling Processes (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 2008
  • 2008-04-18 FR FR0802179A patent/FR2930188B1/fr not_active Expired - Fee Related
• 2009
  • 2009-04-17 RU RU2010146980/02A patent/RU2501639C2/ru active
  • 2009-04-17 CA CA2721449A patent/CA2721449C/fr active Active
  • 2009-04-17 EP EP09732323.2A patent/EP2274141B1/de active Active
  • 2009-04-17 WO PCT/EP2009/054591 patent/WO2009127721A1/fr active Application Filing
  • 2009-04-17 BR BRPI0910569-7A patent/BRPI0910569B1/pt active IP Right Grant
  • 2009-04-17 CN CN2009801216015A patent/CN102056717B/zh active Active
  • 2009-04-17 JP JP2011504476A patent/JP5416762B2/ja active Active
  • 2009-04-17 US US12/988,447 patent/US8490673B2/en active Active

Non-Patent Citations (1)

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