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WO1999019115A9 - Procede et dispositif permettant de donner a des boules en ceramique ou autres materiaux durs une forme spherique - Google Patents

Procede et dispositif permettant de donner a des boules en ceramique ou autres materiaux durs une forme spherique

Info

Publication number
WO1999019115A9
WO1999019115A9 PCT/SE1998/001662 SE9801662W WO9919115A9 WO 1999019115 A9 WO1999019115 A9 WO 1999019115A9 SE 9801662 W SE9801662 W SE 9801662W WO 9919115 A9 WO9919115 A9 WO 9919115A9
Authority
WO
WIPO (PCT)
Prior art keywords
grinding
balls
hard
grinding cell
ball blanks
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.)
Ceased
Application number
PCT/SE1998/001662
Other languages
English (en)
Other versions
WO1999019115A1 (fr
Inventor
Niklas Axen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of WO1999019115A1 publication Critical patent/WO1999019115A1/fr
Anticipated expiration legal-status Critical
Publication of WO1999019115A9 publication Critical patent/WO1999019115A9/fr
Ceased legal-status Critical Current

Links

Classifications

    • 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
    • B24B31/00—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor
    • B24B31/10—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor involving other means for tumbling of work
    • 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
    • B24B11/00—Machines or devices designed for grinding spherical surfaces or parts of spherical surfaces on work; Accessories therefor
    • B24B11/02—Machines or devices designed for grinding spherical surfaces or parts of spherical surfaces on work; Accessories therefor for grinding balls

Definitions

  • the present invention relates to a method of grinding and polishing spheres of hard materials according to the preamble of claim 1, and an apparatus for the realisation of the method according to the preamble of claim 6.
  • Balls of hard materials such as cemented carbides or ceramic materials are being increasingly used in various applications.
  • such balls are used in fully ceramic ball bearings and in so called hybrid ball bearings, combining ceramic balls with races of ball bearing steel.
  • Hybrid ball bearings are used in applications involving small tolerances and high rotational speeds, e.g. highly efficient machine tools or turbines. Ceramic bearings do also withstand higher temperatures than metallic bearings; they are more chemically resistant and are also less dependent on continuous lubrication with oil or grease, which is advantageous in the chemical or food industries.
  • the conventional machining methods do however suffer from problems such as low machining rates and high tool wear, making the machining sequences slow and expensive parts of the manufacturing route for ceramic balls.
  • grinding agents containing hard particles that cut the surface to be machined are often used.
  • the grinding agent may be bonded to the surface of a tool, or may move freely between the tool and the surface to be machined.
  • the machining of hard and thereby often brittle materials is generally more difficult, expensive and time-consuming than the machining of softer and more ductile materials. Because of the high requirements on the abrasive grits, and on the hardness and wear resistance of the tools, only the very hardest materials (often diamond) can be used. Still the wear of the tools often becomes unacceptably high and the risk of surface fracture of brittle materials is critical.
  • balls are ground in a magnetic fluid containing grits in a grinding cell having such a geometry that the balls are forced to rotate in many different directions, leading to an even distribution of the material removal over the surface.
  • the balls are machined against the surfaces of the grinding cell through the grits available in the magnetic fluid.
  • a novel method for the grinding of balls should possess the following properties:
  • the method should enable rapid and cheap grinding and polishing. 2)
  • the technique should offer possibilities to control the size of the spheres and the surface finish.
  • the method is mechanical and based on the grinding of balls of hard materials against balls of softer materials through the addition of grinding agents in an apparatus in which the balls are pressed against each other and forced to rotate and slide relative to each other.
  • Fig. Ia and Ib illustrate schematically, in cross-section and in a plane view from above, the method of the invention put into practice in a first version of the apparatus;
  • Fig. 2 a and 2b illustrate schematically the method applied in a second version of the apparatus, in views corresponding to the views of Fig. 1;
  • Fig. 3 and 4 illustrate schematically alternative geometries of grinding cell incorporated in the apparatus.
  • the method is based on the principle of grinding hard balls, such as ceramic balls, from coarsely shaped blanks, against already manufactured softer balls, such as steel balls, to which grinding particles, e.g. diamond powder, are added.
  • This can take place in a grinding cell, which may be of different geometries.
  • the grinding cell consists of an upper and a lower part, both of rotational symmetry, which are at least partially manufactured of an elastic material of suitable hardness, preferably softer than the softer balls.
  • An elastic material is referred to as a material, which regains its original shape after deformation.
  • a number of balls of alternatingly hard and soft materials are positioned in a ring in a race-rack within the grinding cell, in such a way that each hard ball is in contact with at least one soft ball. It is an advantage to sort the balls so that every second ball is hard and every second soft. For the grinding of ceramic balls, softer balls of ball bearing steel may be used. ⁇
  • the dimensions of the grinding cell racetrack are adopted to the size and number of the hard and the soft balls, so that when the parts of the grinding cell are pressed together, the balls are pressed against the walls of the grinding cell, and hard ball presses against soft ball in a ring.
  • the friction between the balls and the grinding cell force the balls to follow the grinding cell in its rotation and thereby to slide relatively to each other.
  • the grits will stick to the surface of the softer balls and machine the surface of the harder balls. This implies a suitable choice of material for the grinding cell walls, so that the friction between the walls and the balls is higher than that between the balls.
  • the geometry of this type of grinding cell should be such that the balls are forced to rotate essentially equally in all directions, for the machining rate to distribute equally over the surfaces of the balls.
  • the size of the softer balls and the geometry of the grinding cell determine the size of the hard balls. The grinding rate of the hard balls is reduced when their size is reduced to that of the softer balls, since the force pressing them together thereby falls.
  • the grinding method according to the invention may use both coarse and fine, hard and soft particles.
  • Hard particles generally produce higher machining rates, while smaller and softer particles give smoother surfaces. Machining rate and surface finish are controlled by suitable choices of grinding agent, the magnitude of the applied load, the rotational speed, and the number of balls in the grinding cell.
  • Fig. Ia schematically shows a cross-section of a first embodiment, of a grinding cell, comprising two axially on top of each other journalled rotationally symmetrical bodies, 1 and 2.
  • the bodies 1 and 2 are designed to define a circular racetrack 3 therebetween for the hard ball blanks 4 and the softer balls 5.
  • One of the bodies, 1 or 2, of the grinding cell is propelled relative to the other, and during the process a load is applied axially towards the other body.
  • the grinding cell according to Fig. Ia and Ib is provided with a central core 6, the geometry of which being designed to exert a pressure directed radially outwards during the process.
  • Fig. Ib illustrates schematically in a plane-view from the top, how the hard ball blanks 4 and the softer balls are arranged alternatingly in the lower grinding cell body 2.
  • FIG. 2a and 2b an alternative embodiment of the grinding cell is illustrated schematically.
  • the grinding cell of Fig. 2 differs from that in fig. 1 mainly in that the rotationally symmetrical bodies 1' and 2' are designed to exert a radially inwardly directed pressure or load during the process.
  • the circular racetrack 3 has a trapezoid cross-section, wherein the ball blanks and the softer balls are in contact with three sides of the cross-section of the racetrack.
  • the racetrack 3 has an inner periphery which diverges from the central axis of the grinding cell, while in the second embodiment the outer periphery of the racetrack's cross-section diverges from the central axis.
  • Fig. 3 shows schematically a sectioned, partial view of a grinding cell 30.
  • the grinding cell 30 comprises two rotationally symmetrical bodies 31 and 32, axially aligned and with their opposed surfaces formed to define a circular racetrack 33.
  • racetrack 33 In an unspecified way, one of the bodies is driven to rotate in relation to the other body.
  • the racetrack 33 are hard ball blanks and softer balls, both referred to with the reference numeral 34 in the figure, positioned in a ring to follow the rotational motion of the bodies, under an axially applied load.
  • the cross section of the racetrack 33 is essentially triangular for which both the outer and the inner periphery are diverging away from the central axis of rotation C. It is realised from considering fig. 3, the racetrack 34, within an interval, can hold ball and ball blanks of different sizes to be pressed against each other and against the inner, slanting periphery.
  • Fig. 4 shows schematically a sectioned, partial view of a grinding cell 40.
  • the grinding cell 40 comprises two rotationally symmetrical bodies, one loading body 41 and one supporting body 42, axially aligned and journalled for relative rotation around an axis C.
  • the lower body, in this embodiment the supporting body 42 has a cylindrical, partially conical core 43, which is slidably arranged in the centre of the stationary supporting body 42.
  • the body 42 with the core 43 and the body 41 together define a circular racetrack 44 having a trapezoidal cross section.
  • An axis 45 is centrally extended from the core, the body 41 being rotatably journalled on the axis near the top of the core 43.
  • a driving means 46 drives the body 41 in rotation around the shaft 45 under the application of an axial pressure from a loading means 47.
  • a channel 48 passes through the core 43.
  • the racetrack 44 within an interval, is permitted to receive balls and ball blanks of varying dimensions 49, 50 in contact against each other and against the periphery of the core, as well as against the loading body 41 and against the supporting body 42.
  • balls and ball blanks are in contact with each other and with the three surfaces defined by the bodies building up elements constituting the grinding cell.
  • the racetrack may have a polygonal cross-section in which the balls or the balls and the ball blanks are in contact with four or more surfaces of e.g. a facetted racetrack.
  • the cross-section of the racetrack may be curved, concave or convex, either partially in the areas which are in contact with the periphery of the balls, or alternatively along sections or along whole peripheries of the racetrack.
  • a material should be chosen which is elastic enough to be able to adapt in form to the size of both the soft balls and the harder balls, which normally initially has a larger diameter, in order to rotate these through the friction.
  • the material should also be softer than the softer balls, and as en example can here be mentioned plastics or rubber, either for the grinding cell in its entirety or only partially on the surfaces which are in contact with the periphery of the balls.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)

Abstract

L'invention concerne un procédé permettant donner à des ébauches de boules en matériaux durs la forme de sphères d'une grande sphéricité et d'un grand fini de surface. Selon l'invention, les boules en matériaux durs (p.ex. en céramique) sont amenées à glisser contre des boules déjà sphériques de matériaux plus souples (p.ex. acier) dans une cellule de meulage (1, 2) par addition d'agents de meulage, p.ex. grains de diamants. Avec la cellule de meulage, les boules dures et souples placées en alternance sont pressées les unes contre les autres dans une piste circulaire, définie par les surfaces, se faisant face, de deux corps à symétrie de rotation tournant l'un par rapport à l'autre. Ces corps exercent à la fois une force axiale dirigée vers les boules et une force radiale dirigée vers l'intérieur ou vers l'extérieur.
PCT/SE1998/001662 1997-10-10 1998-09-16 Procede et dispositif permettant de donner a des boules en ceramique ou autres materiaux durs une forme spherique Ceased WO1999019115A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9703721A SE512408C2 (sv) 1997-10-10 1997-10-10 Metod och slipcell för rundslipning av kulor av keramiska eller andra hårda material
SE9703721-2 1997-10-10

Publications (2)

Publication Number Publication Date
WO1999019115A1 WO1999019115A1 (fr) 1999-04-22
WO1999019115A9 true WO1999019115A9 (fr) 2007-08-09

Family

ID=20408587

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1998/001662 Ceased WO1999019115A1 (fr) 1997-10-10 1998-09-16 Procede et dispositif permettant de donner a des boules en ceramique ou autres materiaux durs une forme spherique

Country Status (2)

Country Link
SE (1) SE512408C2 (fr)
WO (1) WO1999019115A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20010008210A (ko) * 2000-11-11 2001-02-05 한재만 합성수지를 소재로 한 정밀 볼 제조방법
ITBA20010022A1 (it) * 2001-05-11 2002-11-11 Jupiter Srl Testa di precisione ad assi controllati con cambio automatico degli elettromandrini
KR100472931B1 (ko) 2002-08-09 2005-03-10 정동택 세라믹구 제조방법
CN100464951C (zh) * 2007-05-15 2009-03-04 山东东阿钢球集团有限公司 G3级氮化硅球加工工艺

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE555753C (de) * 1930-10-15 1932-07-28 Otto Kadzik Einrichtung zum Schleifen von Kugeln, insbesondere Billardkugeln
GB9401593D0 (en) * 1994-01-27 1994-03-23 Univ Leeds Surface grinding

Also Published As

Publication number Publication date
SE9703721L (sv) 1999-04-11
SE512408C2 (sv) 2000-03-13
SE9703721D0 (sv) 1997-10-10
WO1999019115A1 (fr) 1999-04-22

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