EP3180164B1 - Grinding element, method for producing the grinding element, and injection-molding tool for carrying out the method - Google Patents

Description

The invention relates to a grinding element, a method for producing such a grinding element and an injection molding tool for producing such a grinding element according to the method.

It is known to use ceramic abrasive grains produced in accordance with the so-called SolGel technique in bonded abrasive elements or in coated abrasives. Furthermore, it is known by the sol-gel technique geometrically determined abrasive grains z. B in. Triangular shape. Grinding tools equipped with this are more aggressive and more stable than conventional tools with SolGel abrasives.

From the US RE37,997 E For example, a polishing pad is known for polishing disc-shaped integrated circuit wafers. This polishing pad has differently sized cylindrical openings in its planar surface.

From the WO 2013/186146 A1 It is known to mix abrasive grains with binder and to roll this mass flat with the orientation of the abrasive grains. The binder is at least partially removed. Subsequently, the mass can be subjected to a heat treatment.

The invention has for its object to provide a grinding element that is particularly easy to produce with very good grinding properties and high stability.

This object is achieved by a grinding element having the features of claim 1, by a method having the features of claim 14 and the production in an injection molding tool having the features of claim 20.

It is essential that the grinding element is produced according to the invention as a unitary part by injection molding, wherein the disk-shaped base body and formed on this cutting of hard materials are formed. The individual cutting edges are each - in relation to the direction of rotation of the grinding element in use - immediately downstream of a generally cylindrical opening in the main body, so that the rake face of the respective cutting edge directly adjoins the wall of the opening, and extends in the extension thereof, whereby the rake angle forms. It can be set in a very simple manner, a rake angle of α = 0 ° or a positive or negative rake angle, the limits for this are given in claim 2.

A particularly favorable and optimal for the cutting effect arrangement results from the features of claims 3 to 5, as a result, the blades have a small radial offset relative to the trailing or leading edge. Through the development according to claim 6 and / or 7, the conclusion to the outer edge of the grinding element is then created as it were.

The further embodiment according to claim 8, the aforementioned advantages are optimized.

Through the development according to claims 9 and / or 10 it is achieved that the cutting only with its cutting edge with the to be cut Material come into contact and that thus no or no significant friction on the side edges of the cutting occurs. Furthermore, this ensures that the cut off during the grinding process material of the workpiece to be machined soft or smooth can flow over the rake face.

Claims 11 and 12 indicate the particularly favorable materials for the production of the abrasive element; their optimum grain size results from claim 13.

The core of the particularly favorable method according to claim 14 is that the production of the grinding element takes place practically in one operation from a starting mass prepared by mixing and kneading by injection molding. In this case, the grinding element is essentially already given its final shape consisting of a generally disc-shaped basic body, the openings and the cutting edges. After demolding of the raw component produced by injection molding, the binder is removed by solvent and / or thermally, ie under heat. This is followed by sintering of the raw component, whereby the grinding element reaches its final hardness.

The claims 15 to 19 show again, in what form the hard materials and which binders are used and how the binder removal and sintering material-specific done.

Claim 20 is the injection molding tool again, with which in particular the shaping essential for the grinding element takes place.

Fig. 1

eine schematische Darstellung eines Spritzgieß-Werkzeugs zur Herstellung eines Roh-Bauteils eines erfindungsgemäßen Schleifelementes,

Fig. 2

eine Draufsicht auf eine Formplatte des Spritzgieß-Werkzeugs gemäß Fig. 1,

Fig. 3

einen Teilschnitt durch das Werkzeug gemäß der Schnittlinie III-III in Fig. 2,

Fig. 4

die Anordnung von Bolzen am Werkzeug-Oberteil,

Fig. 5

einen Teilquerschnitt durch ein Schleifelement nach der Erfindung, mit Schneiden mit teilzylindrischer Spanfläche,

Fig. 6

eine Draufsicht auf die Schneide nach Fig. 5 mit vorgeordneter Öffnung im Schleifelement,

Fig. 7

eine die Lage der Schneide zur vorgeordneten Öffnung zeigende Draufsicht,

Fig. 8

eine Draufsicht auf eine Schneide mit teilkonischer Spanfläche und vorgeordneter Öffnung,

Fig. 9

einen Querschnitt durch die Schneide nach Fig. 8 gemäß der Schnittlinie IX-IX in Fig. 8,

Fig. 10

eine Draufischt auf eine Schneide mit gegenüber den Fig. 8 und 9 abgewandelter teilkonischer Spanfläche mit vorgeordneter Öffnung und

Fig. 11

einen Querschnitt gemäß der Schnittlinie XI-XI in Fig. 10.

Further features, advantages and details of the invention will become apparent from the following description of an embodiment with reference to the drawing. It shows:

Fig. 1

a schematic representation of an injection molding tool for producing a raw component of a grinding element according to the invention,

Fig. 2

a plan view of a mold plate of the injection mold according to Fig. 1 .

Fig. 3

a partial section through the tool according to the section line III-III in Fig. 2 .

Fig. 4

the arrangement of bolts on the tool upper part,

Fig. 5

a partial cross section through a grinding element according to the invention, with cutting with part-cylindrical rake face,

Fig. 6

a plan view of the cutting edge after Fig. 5 with an upstream opening in the grinding element,

Fig. 7

a top view showing the position of the cutting edge to the upstream opening,

Fig. 8

a plan view of a cutting edge with part-conical rake face and upstream opening,

Fig. 9

a cross section through the cutting edge after Fig. 8 according to the section line IX-IX in Fig. 8 .

Fig. 10

a Darufischt on a cutting edge with respect to the 8 and 9 modified partial conical rake face with pre-apertured and

Fig. 11

a cross section according to the section line XI-XI in Fig. 10 ,

An abrasive element 1, which will be described in greater detail below in the manner of a grinding wheel, is produced by injection molding in an injection molding tool 2 shown only schematically. This injection molding tool 2 has a tool lower part 3 and a tool upper part 4, which engage in one another in the closed state of the tool 2. The upper tool part 4 has a two-part construction and has an inner mold plate 4 'and an upper closing plate 4 "In the closed state of the injection mold 2, a mold space 5 is delimited by the lower part 3 and by the mold plate 4', in which the grinding element The mold space 5 is circular in plan view and has a center axis 6. Concentric to this axis 6, an inlet 7 for a spray mass 8 to be injected by an injection molding machine 8 is provided in the tool top 4.

In the tool upper part 4 - the mold space 5 facing - numerous bolts 9 are fixed, which in each case a hole 10 in the tool base 3 and a bore 10 'are assigned in the mold plate 4', so that - with closed injection mold 2 - in each case a bolt 9 passes through a bore 10 'and travels into a bore 10, as in FIG Fig. 3 is indicated.

In the mold cavity 5 facing surface 11 of the mold plate 4 'each bolt 9 facing a respective recess 12 is formed, which will be discussed in more detail below.

The axes 13 of the holes 10 and 10 'and corresponding to the bolt 9 are - as Fig. 4 on a first lane 14 designed as an Archimedean spiral or a spiral with a progressive gradient, the radius of which increases from the inner beginning 15 of this first track 14 to its outer end 16 from a radius R1 to a radius R2. From this end 16 to a short extending over about half a circumference in any case but less than a full circumference extending portion of a declining second spiral track 17. Outside are still on a circular track 18 with the axis 6 as the central axis also holes 10th and accordingly bolt 9 is arranged.

The distance a from one another on a track, so the first track 14, the second track 17 and the track 18 adjacent holes 10 from each other, is the same for all holes 10, 10 '.

The shape of the recesses 12 in the inner surface 11 of the mold plate 4 'is based on the FIGS. 5 and 6 explained indirectly. These figures each show a partial section of an injection molding tool 2 formed from the injection molding compound 8 grinding element 1 with a cutting edge 19 whose shape corresponds to the respective recess 12, which is closed by a respective bolt 9. The cutting edge 19 has a part-cylindrical or part-conical rake face 20 which is concentric with the axis 13 of the bolt 9 or the bore 10 and has a rake angle -30 ° ≦ α ≦ 30 °, corresponding to the peripheral surface of the bolt 9. To generate an in Fig. 5 shown rake angle α = 0 °, the portion located in the recess 12 9 'of the bolt 9 is cylindrical. To produce a rake angle α ≠ 0 °, this section 9 'of the bolt 9 is conical. If the portion 9 'tapers away from the tool lower part 3, then the demoulding tool 9 must be mounted in the tool lower part 3.

The cutting edge 19 has a wedge angle β, for which the following applies: 30 ° ≦ β ≦ 120 °.

The cutting edge 19 has a rounded end portion 22 with a radius r2, which is smaller than the radius r1 of the respective bore 10 and the bolt 9. From the rake face 20 side flanks 23, 24 lead to said end portion 22, in particular Fig. 6 is removable. The cutting edge 19 thus tapers towards the end portion 22. The cutting edge 19 has a height b above the main body 25 of the grinding element 1, wherein this height b is simultaneously the height above a cylindrical opening 26 which is formed by the respective pin 9 in the disk-shaped base body 25 of the grinding element. The part-cylindrical or partially conical rake face 20 thus directly adjoins this opening 26.

As FIGS. 5 and 6 Furthermore, the cutting edge 27 formed by the penetration of the rake surface 20 and the blade back (clearance surface) 21 is offset outwards relative to the first track 14 or the second track 17 or the circular track 18. In Fig. 7 this is shown in an xyz-coordinate system whose y-axis is defined by the respective axis 13 of a bore 10 and thus the opening 26 and the central axis 6 of the grinding element 1. The x-axis is perpendicular to this and the axis 13. The only in Fig. 5 indicated z-axis is congruent with the respective axis 13 of an opening 26. In Fig. 7 the boundary lines of the side edges 23, 24 of the cutting edge 19 in the plane of the main body 25 are shown, as well as in Fig. 5 is indicated. In this plane, from which project the cutting edges 19, the side flanks 23, 24 cut the boundary line, ie the wall 28 of the opening 26 shown as a circle. Directed to these intersection points or corner points 23 'and 24', starting from the respective axis 13 Rays r23 and r24 respectively include angles γ and δ with the x-axis. The angle γ is the angle of the - with respect to the center axis 6 - outside Side edge 23 of the cutting edge 19 is assigned. The angle δ is the angle which is associated with the side edge 24 of the cutting edge 19, which faces the central axis 6. The following applies: 0 ° ≤ γ ≤ 45 ° and 0 ° ≤ δ ≤ 45 °.

If α <0, then fall in the plan view, as in the Fig. 6 and 7 is shown for a part-cylindrical rake face 20, the wall 28 of the opening 26 and the cutting edge 27 is not together. Rather, in this case for α <0, the representation of the cutting edge 27 draws drawing from the wall 28 of the opening 26 in the tooth back (free surface) 21, such as 8 and 9 is removable. Alternatively, the cutting edge 27 for α> 0 bulges from the wall 28 of the opening 26 towards the latter, such as 10 and 11 is removable. In the 8 to 11 with teilkonischen embodiments of the clamping surfaces 20 with cutting edges 27, the same reference numerals as for the above-described part-cylindrical configuration of the clamping surfaces 20 were selected with cutting edge 27, so as not to disturb the clarity of the description.
If the two angles γ and δ are unequal, a cutting edge 27 formed at an angle to the cutting speed vector formed by the x-axis results, thereby reducing dynamic cutting forces generated by the dipping of the cutting edge 27 into a material to be ground. By this configuration, the immersion is particularly gentle. As is apparent from the above description further in connection with Fig. 7 results, the end portion 22 is offset from the x-axis, ie the cutting speed vector, inwardly so that a collision of the side edges 23 and 24 of the cutting edge 19 is reliably avoided with a workpiece during the cutting movement. In particular Fig. 2 can be seen, the respective opening 26 of the cutting edge 27 and the rake face 20 of the associated blade 19 is related preceded by the direction of rotation 29 at the grinding insert, so that chips can be conveyed away through this opening 26.

It should be repeated that the recesses 12 and the respective section 9 'of the bolts 9 form, as it were, the negative image of the cutting edge 19.

The production of the grinding element takes place as follows:

To prepare the actual - already mentioned - injection molding process, a so-called feedstock, ie a starting material, produced. This starting material contains organic binders which are moldable or sprayable when heated. Such organic binders are high polymers, for example polyolefins, polyamides or polyacrylates and suitable plasticizers for lowering the melt viscosity, such. As phthalates, paraffins or polyethylene glycols. Hard material in the form of particles, which are either Al ₂ O ₃ or ZrO ₂ or Si ₃ N ₄ or SiC particles or cobalt-sheathed tungsten carbide particles, is added to these organic binders. From the high polymers and the hard material particles, the so-called feedstock is produced on an extruder by mixing and kneading. The hard material particles are dispersed in the high polymers.

In a subsequent step, the starting material is heated in an injection molding machine and injected into the injection mold 2, whereby the main body 25 with the numerous according to the above description formed and arranged cutting edges 19 and the respective edges 19 associated openings 26 is formed. After demolding of the injection-molded abrasive element 1 present as a raw component, the organic binders of this raw component become removed by commercial solvents and / or thermal treatment. This binder removal takes place when using Al ₂ O ₃ or ZrO ₂ or Si ₃ N ₄ or WC-Co particles at a temperature of 510 ° C and under ambient air.

For SiC particles, the binder removal is carried out under protective gas or vacuum at a temperature of 280 ° C to 1000 ° C. The choice of temperature depends on what residual strength of the injection molded component is required after binder removal for further handling. If the thermal removal of the binder would result in destruction or high embrittlement of the green component, substantial or total removal of the binder by suitable commercial solvents will be used.

• Al₂O₃ und ZrO₂: 1300°C bis 1700°C unter Atmosphäre, drucklos
• SiC: 1900°C bis 2200°C unter Argon-Schutzgas, drucklos
• Si₃N₄: 1600°C bis 1800°C unter Stickstoff-Schutzgas, 7 bis 50 bar
• WC-Co: 1250°C bis 1500°C unter Argon-Schutzgas, 1 bis 50 bar.

Subsequent to binder removal, the green component is sintered under the following operating conditions:

• Al ₂ O ₃ and ZrO ₂ : 1300 ° C to 1700 ° C under atmospheric pressure
• SiC: 1900 ° C to 2200 ° C under argon blanketing gas, no pressure
• Si ₃ N ₄ : 1600 ° C to 1800 ° C under nitrogen blanketing gas, 7 to 50 bar
• WC-Co: 1250 ° C to 1500 ° C under argon inert gas, 1 to 50 bar.

In the sintering process, the particles grow by solid state diffusion into a body, the grinding element 1 together, with grain sizes k of 0.1 microns ≤ k ≤ 15 microns.

In the sintering process, the respective cutting edge 19 essentially retains the shape that it has received during injection molding. The rake face 20 is formed by the portion 9 'of the respective bolt 9. The rest of the form the cutting edge 19 has been formed by the corresponding shape of the recess 12.

Claims (22)

1. Grinding element (1) consisting of a disk-shaped main body (25) and blades (19) formed as a unit therewith,
   wherein - in relation to a direction of rotation (28) of the grinding element (1) about a center axis (6) - each blade (19) is immediately preceded by an opening (26) passing through the main body (25), and wherein each blade (19) has a rake face (20) having a partially cylindrical shape with a rake angle α = 0° or a partially conical shape with a rake angle α ≠ 0°, characterized in
   that the main body (25) and the blades (19) are made of sintered hard material, and the blades (19) have a height b above the main body (25), wherein 0.1 mm ≤ b ≤ 10 mm.
2. Grinding element (1), characterized in
   that when the rake face (20) has a partially conical shape, the following applies: -30° ≤ α ≤ 30°.
3. Grinding element (1) according to claim 1 or 2, characterized in
   that the openings (26) are arranged, with their respective axes (13), on a first curve (14), which, seen from a starting point (15) adjacent to the center axis (6) to an outer end (16), has the shape of a spiral.
4. Grinding element (1) according to claim 3, characterized in
   that the first curve (14) has the shape of an Archimedean spiral.
5. Grinding element (1) according to claim 3, characterized in
   that the first curve (14) has the shape of a spiral with a progressive pitch towards the outer end (16).
6. Grinding element (1) according to any one of claims 3 to 5, characterized in
   that openings (26) are provided that are arranged on a second curve (17) adjoining the outer end (16) of the first curve (14) and extending in the shape of a partial spiral across less than a circumference of the main body (25).
7. Grinding element (1) according to any one of claims 2 to 6, characterized in
   that openings (26) are provided that are arranged on an outer circular curve (18).
8. Grinding element (1) according to any one of claims 1 to 7, characterized in
   that openings (26) arranged immediately adjacent to each other on the at least one curve (14, 17, 18) have identical distances a from each other.
9. Grinding element according to any one of claims 1 to 8, characterized in
   that - in relation to an x-y-z coordinate system the z-axis of which is congruent with the axis (13) of a respective opening (26) and the y-axis of which runs through the center axis (6) and the axis (13) of the respective opening (26), in other words radially to the center axis (6), and the x-axis of which runs perpendicularly to the y-axis and to the z-axis - the cutting edge (27) extends, in relation to the x-axis, outwardly across an angle γ and inwardly across an angle δ, wherein: $$0°\le \gamma \le 45°\mathrm{and}0°\le \delta \le 45°.$$

   
10. Grinding element (1) according to any one of claims 1 to 9, characterized in
    that the blades (19) taper towards a rear end section (22) in a direction counter to the direction of rotation (28), and
    that the respective end section (22) is arranged on the main body (25) in a position opposite to the respective x-axis and inwardly offset towards the center axis (6).
11. Grinding element (1) according to any one of claims 1 to 10, characterized in
    that the hard material is crystalline.
12. Grinding element (1) according to any one of claims 1 to 11, characterized in
    that the blades (19) and the main body (25) consist of a hard material in the form of Al₂O₃ or ZrO₂ or Si₃N₄ or SiC or of a hard metal, in particular WC-Co.
13. Grinding element (1) according to any one of claims 1 to 12, characterized in
    that the sintered hard material has a grain size k, wherein 0.1 µm ≤ k 15 µm.
14. Method for producing a grinding element (1) according to any one of claims 1 to 13,
    wherein an initial material is produced by kneading and mixing from an organic binding agent that becomes moldable when heated and hard material in the form of particles;
    wherein, in a subsequent step, a raw component of the grinding element, consisting of the disk-shaped main body (25) and the blades (19), is produced by injection molding;
    wherein, in a subsequent step, the binding agent is removed from the raw component, and
    wherein, in a subsequent step, the grinding element is formed from the raw component in a sintering process.
15. Method according to claim 14, characterized in
    that the hard material used is in the form of particles of Al₂O₃ or ZrO₂ or Si₃N₄ or SiC or hard metal, in particular WC-Co.
16. Method according to claim 14 or 15, characterized in
    that the following organic high polymers are used as binding agent: polyolefins, polyamides or polyacrylates.
17. Method according to any one of claims 14 to 16, characterized in
    that the binding agent is removed from the raw component by means of heat and/or solvents.
18. Method according to claim 17, characterized in
    that the binding agent is removed by means of heat under the following conditions:

    when using Al₂O₃ or ZrO₂ or Si₃N₄ or WC-Co particles at a temperature of 510°C in the presence of ambient air, and

    when using SiC particles at a temperature of 280°C to 1000°C in an inert gas atmosphere or under vacuum.
19. Method according to any one of claims 15 to 18, characterized in
    that sintering takes place under the following conditions when using:

    Al₂O₃ and ZrO₂: 1300°C to 1700°C under atmosphere, without pressure;

    SiC: 1900°C to 2200°C in an argon inert gas atmosphere, without pressure;

    Si₃N₄: 1600°C to 1800°C in a nitrogen inert gas atmosphere, 7 to 50 bar;

    WC-Co: 1250°C to 1500°C in an argon inert gas atmosphere, 1 to 50 bar.
20. Injection-molding tool (2) for producing the grinding element (1) according to any one of claims 1 to 13 using the method according to any one of claims 14 to 19,
    wherein two tool components (3, 4) are provided that define a molding space (5) when the injection-molding tool (2) is closed;
    wherein bolts (9) are arranged on one tool component (4) for molding the openings (26) and the rake faces (20), the bolts (9) engaging drill holes (10) of the other tool component (3) when the injection-molding tool (2) is closed,
    and wherein recesses (12) are formed in one tool component (4) for molding the blades (19), said blades (19) having a height b above the main body (25), wherein 0.1 mm ≤ b ≤ 10 mm.
21. Injection-molding tool according to claim 20, characterized in
    that one tool component (4) is formed in two pieces with the molding plate (4') defining the molding space (5), wherein the molding plate (4') comprises the recess (12) for molding the blades (19) and drill holes (10') penetrated by the bolts (9).
22. Injection-molding tool according to claim 20 or 21, characterized in
    that the bolts (9) are cylindrical or conical in the region of the recess (12).

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