RU2567165C2 - Grinding wheel with polymer binder - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to grinding and may be used for grinding of drill bit polycrystalline diamond insert. Claimed process comprises contact of polycrystalline diamonds insert with grinding wheel including diamonds, polymer binder and mix of filler solid particles and filler soft particles. Note here that said diamonds feature concentration of diamonds of 175-225. Polymer binder makes 30-40 vol %. Mix of filler solid and soft particles makes 5-30 vol %. Solid-to-soft filler particles ratio in the mix makes 85:15 to 15:85.

EFFECT: higher efficiency of grinding, ruled out or decreased necessity in dressing the wheel outer surface.

8 cl, 2 tbl, 2 dwg

Description

Polycrystalline Diamond Insert (PDC) of the drill bit includes a layer of polycrystalline diamonds glued to a tungsten carbide substrate. The polycrystalline diamond layer provides high hardness and abrasion resistance, while a tungsten carbide substrate improves the strength of the composite material. Polycrystalline diamond inserts are often used as cutting elements of a drill bit, which are used to drill the earth to extract natural resources.

Grinding wheels with abrasive diamond particles can be used for grinding and final processing of polycrystalline diamond inserts (PDC) to their final specified sizes. Polycrystalline diamond inserts (PDC) are very difficult to grind due to the contact surface of two materials of different hardness. Due to the increased hardness of the polycrystalline diamond layer, the diamond abrasive of the grinding wheel on the polymer bond wears out very quickly. In addition, the tungsten carbide substrate clogs the grinding wheel, which reduces its ability to further grind a layer of polycrystalline diamonds. As a result, a polymer bonded grinding wheel with abrasive material must be continuously cleaned with a carborundum bar to reduce or remove clogged tungsten carbide particles from the grinding wheel and to allow fresh diamond cutting edges to exit onto the grinding surface.

To improve the grinding efficiency of polycrystalline diamond inserts (PDC) using grinding wheels with abrasive material on a polymer bond, it is desirable to reduce or eliminate the need to constantly clean the abrasive grinding wheel using a carborundum bar. Reducing or eliminating the need to clean the abrasive grinding wheel, provided that the cutting ability of the layer of polycrystalline diamond inserts (PDC) is still acceptable, improves the safety and efficiency of the grinding operation. A grinding machine operator can service more than one machine if a polymer bonded grinding wheel does not require constant dressing during fine grinding of polycrystalline diamond inserts (PDC).

Thus, on the one hand, the invention relates to a grinding method, which includes: contacting a polycrystalline diamond insert with a grinding wheel; the grinding wheel includes diamonds, a binder resin (polymer binder) and a mixture of solid filler particles and soft filler particles; as for the diamond content, the diamond concentration is from 175 to 225 per volume, the polymer bond is from 30 percent to 40 percent per volume, the ratio of solid particles of filler and soft particles of the filler in the mixture is from 85:15 to 15: 85, and the mixture of solid filler particles and soft filler particles is from 5 percent to 30 percent based on volume.

On the other hand, the invention relates to an abrasive material, which includes: a grinding wheel, a grinding wheel containing diamonds, a polymer bond, as well as a mixture of solid filler particles and soft filler particles; as for the diamond content, the diamond concentration is from 175 to 225 per volume, the polymer bond is from 30 percent to 40 percent per volume, the ratio of solid particles of filler and soft particles of the filler in the mixture is from 85:15 to 15: 85, and the mixture of solid filler particles and soft filler particles is from 5 percent to 30 percent based on volume.

BRIEF DESCRIPTION OF THE DRAWINGS

The repeated use of symbols in the technical description and figures is intended to display the same or similar characteristics or elements of the present invention.

Figure 1 depicts the process of centerless grinding using a grinding wheel with abrasive material on a polymer bond, which are processed polycrystalline diamond inserts (PDC) to the final diameter.

Figure 2 displays the results of grinding efficiency, contrasting the inventive grinding wheel on a polymer bond to a comparative sample - a grinding wheel on a polymer bond, in relation to the different frequency of the operation to edit the wheel.

DEFINITIONS

The variations of the words “consist of,” “have,” and “include” used herein are legal equivalents and their use is not limited. From this it follows that additional not listed elements, functions, steps or features of the invention may be presented in addition to the listed elements, functions, steps or features of the invention.

DETAILED DESCRIPTION

With reference to FIG. 1, a centerless grinding machine 10 is illustrated here. A centerless grinding machine consists of a grinding wheel with abrasive material on a polymer bond 12, a control wheel 14 and a support member 16 for holding a polycrystalline diamond insert (PDC) 18 between two circles. The PDC includes a layer of polycrystalline diamonds 20 glued to a tungsten carbide substrate 22. The speed at which the polycrystalline diamond insert (PDC) passes through the grinding surfaces between the two circles is controlled by the angle of elevation of the screw thread α between the axis of the grinding wheel with the abrasive material on polymer bundle 12 and the axis of the control circle 14 in combination with the speed of rotation of the control circle.

A prototype of a grinding wheel with an abrasive material on a polymer bond requires constant dressing of the outer surface 26 with a carborundum bar to maintain the ability of the abrasive grinding wheel on a polymer bond to grind a layer of polycrystalline diamonds.

In order to reduce or completely eliminate the need to edit the outer surface when grinding polycrystalline diamonds (PDC), it is desirable to make the grinding wheel with abrasive material on a polymer bond work similarly to a grinding wheel with a vitreous bond. This effect can be achieved by using a very large concentration of diamonds when solid filler particles and soft filler particles are included in the mixture to control the rate of plasticization of the grinding wheel with an abrasive material on a polymer bond. Such an abrasive grinding wheel on a polymer bond should provide a protrusion value of fresh diamond particles on the wheel while reducing or eliminating the effect of salting the outer surface of the wheel during its use. A high concentration of part of the diamonds may be the outer ring of the grinding wheel; it can be either a surface divided into segments, or the entire grinding wheel as a whole.

Suitable diamonds to be used as abrasive material for a wheel include, for example, natural diamonds, synthetic diamonds, polymer bonded diamonds, metal bonded diamonds, diamond based abrasive powder, diamond agglomerates mentioned above, polymer bonded or vitreous bonded , as well as combinations of all of the above. To achieve the necessary hardness of the abrasive grinding wheel on a polymer bond, the diamond concentration must be very high. In particular, the concentration of diamonds, based on the percentage by volume of the total volume of a high concentration of the proportion of diamonds in the grinding wheel, is from 175 to 225 or from 180 to 200. The concentration of diamonds lower than 175 does not reduce the number of edits of the grinding layer, but at a concentration higher than 225 it becomes difficult to bind diamonds with a sufficiently high degree of layer integrity. Diamonds can be either coated or uncoated using a metal coating made of nickel or copper. If metal coated diamonds are used, the percentage of weight of the coating layer should be less than 40% or less than or equal to 30%. Excessive doses of the coating reduce the diamond concentration to the lowest level and do not contribute to reducing the number of dressings of the grinding wheel on the polymer bond during its use. The size of diamonds not combined into agglomerates should be from 60/80 sieve mesh sizes to 200/230 sieve mesh sizes. The sizes above and below the specified boundaries do not provide the necessary density of the components to obtain the required diamond concentration.

Although polymeric bonded abrasive diamonds can be considered suitable for grinding, especially when they are used as diamond agglomerates, it is preferred to use metallic bonded abrasive diamonds. Polymer bond diamonds are generally too unstable and weak to be used as abrasive material on a polymer bond grinding wheel for grinding polycrystalline diamond inserts (PDC).

Diamonds used on a metal bond are divided according to strength according to the following scale: from crumbling diamonds (weak) to small crumbling diamonds (strong). This strength rating has been developed by various material suppliers who use different diamond strength designations. In order for fresh diamonds to protrude more strongly from the grinding layer, it is preferable to use weaker diamonds on a metal bond. For example, if you use diamonds supplied by ABC Superabrasives, strength will be graded on a scale of ABS 2 (weak) to ABS 9 (durable). When using ABCE Superabrasive diamonds, it is advisable to use ABS 2 or ABS 3 diamonds for this purpose. The Worldwide Superabrasives diamond strength scale is designated WSG 200 to WSG 900. Diamonds with a strength of WSG 200, WSG300, WSG400 are suitable for the above purpose. and WSG500. LANDS Superabrasives has gradations of strength designated LS200, LS230, LS250, LS260, LS270 and LS290. For the above purpose, diamonds with the strength LS200, LS230 and LS240 are suitable. Basically, in order to ensure that fresh diamonds protrude stronger from the grinding layer during grinding, the entire lower part of the scale (50% of the scale from the designation of the lower level of strength) of the strength of all these suppliers of diamonds with a metal bond is suitable.

Polymeric binders suitable for use with abrasive diamond particles include formaldehyde-containing resins such as phenol-formaldehydes, novolac phenol-formaldehyde resins and, in particular, resins with the addition of a crosslinking agent (eg, hexamethylenetetramine), phenoplasts and amines; unsaturated ester resins (phenol-formaldehyde polymers); vinyl ester resins; alkyd resins, allyl resins; furan resins; epoxy resin; polyurethanes; cyanic acid esters and polyimides. The amount of polymer binder used in abrasive grinding wheels is approximately 30% to 40% by volume, such as the amount of polymer binder, approximately 35%, by volume is used for a high concentration of the proportion of diamonds in the grinding layer. Basically, the amount of binder resin should be sufficient to completely wet the surfaces of all the individual particles during production, so that a permanent polymer substrate, largely devoid of porosity, is formed using inorganic components separately glued over the entire area (length), which would be mechanical design of the grinding wheel.

Suitable filler additives may include reinforcing particles, auxiliary grinding media, moisture absorbers, coloring agents, and lubricants. As noted earlier, both hard and soft particles are used in addition to diamonds to strengthen the layer and control the rate of destruction of the grinding wheel. Solid filler particles (excluding diamonds) are those that have a Mohs hardness of 7 or higher. Suitable solid filler particles include alumina, silicon carbide (carborundum), zirconium, particles of ceramic alpha alumina (ceramic alumina) are usually derivatives of boehmite bauxite salts, or other abrasive particles having an appropriate Mohs hardness. Soft filler particles are those that have a Mohs hardness of 5 or lower. Suitable soft filler particles include petroleum coke, pyrophyllite, aluminum fluoride (cryolite), calcium hydroxide (lime), graphite, refractory material (chamotte), plastic clay, copper, or talc.

The volume ratio of hard and soft particles of the filler is (may be) from 15:85 to 85:15, or from 30:70 to 70:30, or from 40:60 to 60:40. Sizes of suitable particulate filler particles include sizes equal to or less than 30 microns, such as sieve equivalents of 600, 800, or 1000 in accordance with ANSI (American National Standards Institute) standards. The sizes of suitable soft filler particles include sizes equal to 100 mesh sizes, or even smaller ones. If necessary, soft filler particles may have either a finely divided fraction or a coarse-grained fraction. The fine fraction can be finer than 280 mesh sizes, and the coarse fraction can be between 100 and 180 mesh sizes. When using two sizes of soft particles, the volume fractional content of coarse particles to fine particles can range from 50:50 to 70:30. Too high a volumetric content of solid particles of the filler prevents destruction, which leads to heat generation and gloss of the grinding wheel, and too large a volumetric content of soft particles of the filler undesirably increases the wear rate of the grinding wheel. The volume percentage of a mixture of solid filler particles and soft filler particles in the abrasive layer of the grinding wheel on a polymer bond is from 5% to 30%, or from 8% to 20% of a high concentration of diamonds.

Other fillers may include fibrous materials and plate materials, such as carbon or glass fiber crystals and mica. Auxiliary grinding agents are substances such as: aluminum fluoride (cryolite), potassium tetrafluoroborate (KBF ₄ ), polyvinyl chloride, lignosulfonates and various mixtures thereof. Coloring agents, such as organic and inorganic pigments or crystals, may be included in the grinding wheel.

EXAMPLES

The objectives and advantages of this described invention are clearly shown below in the form of grinding wheel samples that are not restrictive. Certain materials and their quantities in the composition indicated in relation to these samples, as well as other conditions and details, should not be presented in such a way that may unfairly limit the essence of this invention. Unless otherwise indicated, all parts, percentages, ratios, proportions, etc., indicated for examples, are weighted.

The following materials were used to prepare the grinding wheel presented for obtaining a patent for the invention and the grinding wheel serving as a comparative sample.

Table 1: Components Symbol Description NP1 Phenolic resin (powder) from Hexion Specialty Chemicals Inc., Augusta, Georgia, USA, trade name Durite® AD-3237 NP2 Phenolic resin (powder) from Hexion Specialty Chemicals Inc., Augusta, GA, trade name Durite® AD-5575 NP3 Phenolic resin (powder) from Hexion Specialty Chemicals Inc., Augusta, GA, trade name Durite® AD-3235 SC Abrasive with a grain size of 1000, Green Carborundum from Washington Mills Electro Minerals Corp., Niagara Fole, NY, trade name "CGW-3" Green Silicon Carbide (green carborundum), strength - for abrasive grinding wheel, class strength - 1000

Sun Boron Carbide, Strength Category - 1000, from Electro Abrasives Corporation, Buffalo, NY, NY; trade name Electrobor ™ Cu Raw copper powder from ACuPowder International LCC, Union, NJ, Copper Powder EL-100 untreated (EL-100 copper powder untreated) MO Magnesium oxide from Atlantic Equipment Engineers, Bergenfield, NJ, trade name Magnesium Oxide MG-601 (Magnesium Oxide MG-601) RS1 Calcined Petroleum Coke (4082) Calcined Petroleum Coke, a calcined petroleum coke from Asbury Graphite Mills Inc., Asbury, NJ PC2 Calcined Petroleum Coke (4372) Calcined Petroleum Coke, a calcined petroleum coke from Asbury Graphite Mills Inc., Asbury, NJ With Mississippi Lime Calcium Oxide, Alton, Ill., Polycal ™ OF325 Calcium Oxide (Polycal ™ OF325 Calcium Oxide) 321 3M Ceramic Abrasive, St. Paul, Minnesota, 321 Cubitron ™ JIS800 321V 3M Ceramic Abrasive, St. Paul, Minnesota, 321 Cubitron ™ JB800 D1 Synthetic diamonds (powder) on a metal bond, 30% nickel plated, sieve size 100/120 from Worldwide Superabrasives, Fort Lauderdale, Florida, trade name MV-100 N30 100/120 D2 Synthetic bonded diamonds (powder), 30% nickel plated, sieve size 140/170 from Worldwide Superabrasives, Fort Lauderdale, Florida, trade name MV-100 N30 140/170 D3 LSMBO Uncoated synthetic diamonds (powder) on a metal bond, sieve size 200/230 from LANDS Superabrasives Co., New York, NY D4 LSMBO Uncoated synthetic diamonds (powder) on a metal bond, sieve size 325/400 from LANDS Superabrasives Co., New York, NY D5 LS-MAO Uncoated synthetic diamonds (powder) on a metal bond, sieve size 100/120 from LANDS Superabrasives Co., New York, NY D6 LS-MAO Uncoated synthetic diamonds (powder) on a metal bond, sieve size 120/140 from LANDS Superabrasives Co., New York, NY D7 LS-MAO Uncoated synthetic diamonds (powder) on a metal bond, sieve size 140/170 from LANDS Superabrasives Co., New York, NY D8 Polymer-bonded synthetic diamonds (powder), uncovered, sieve size 140/170 from Worldwide Superabrasives, Fort Lauderdale, Florida, trade name RB-150 140/170 D9 Polymer-bonded synthetic diamonds (powder), 50% copper plated, sieve size 120/140 from Worldwide Superabrasives, Fort Lauderdale, Florida, trade name RB-150 C50 120/140 NP4 Powder Resin from Bitrez Ltd., Standish Wigan, Lancashire, UK, Trade Name Dialok AR939P Resin Powder (Dialok AR939P Powder Resin) SC Synthetic aluminum fluoride (cryolite) from Washington Mills, Tonavanda, New York, USA, trade name SODIUM HEXAFLUOROALUMINATE (sodium hexafluoroaluminate), CRYOLITE K

D10 Polymer-bonded synthetic diamonds (powder), 30% nickel plated, sieve size 140/170 from Worldwide Superabrasives, Fort Lauderdale, Florida, trade name RB-150 N30 140/170 D11 Polymer-bonded synthetic diamonds (powder), 56% nickel plated, sieve size 100/120 from Worldwide Superabrasives, Fort Lauderdale, Florida, trade name RB-150 N56 100/120 G Graphite / carbon 4539 Powder (Aspirated Graphite / Carbon Powder 4539) from Asbury Graphite Mills Inc., Asbury, NJ D12 Synthetic bonded diamonds (powder), 30% nickel plated, 60/80 sieve from Worldwide Superabrasives, Fort Lauderdale, Florida, brand name MB-100 N30 60/80 D13 Synthetic bonded diamonds (powder), 30% nickel plated, 80/100 sieve from Worldwide Superabrasives, Fort Lauderdale, Florida, trade name MV-100 N30 80/100 D14 LSMBO Uncoated synthetic diamonds (powder) on a metal bond, sieve size 60/80 from LANDS Superabrasives Co., New York, NY D15 LSMBO Uncoated synthetic diamonds (powder) on a metal bond, sieve size 80/100 from LANDS Superabrasives Co., New York, NY D16 LSMBO Uncoated synthetic diamonds (powder) on a metal bond, sieve size 100/120 from LANDS Superabrasives Co., New York, NY D17 LS-MAO Unbonded synthetic diamonds (powder) on a metal bond, sieve size 80/100 from LANDS Superabrasives Co., New York, NY D18 LSOO Uncoated synthetic diamonds (powder) on a metal bond, sieve size 200/230 from LANDS Superabrasive Co., New York, NY

Grinding wheels of Examples 1, 7, 9 to 14 and grinding wheels of Comparative Examples 1A to 6A were manufactured and tested on PDC polycrystalline inserts to evaluate their grinding performance. The grinding wheels of Example 1 and Comparative Example 1A were evaluated using various grinding wheel dressing procedures. The weight percentages of various grinding wheels are shown in Table 2.

General procedure for forming a grinding wheel section

Each grinding wheel composition listed in Table 2 was thoroughly mixed for 4 hours in 1000 ml of a polyethylene mixing tank, and a 2-roller mill on a bed (2-Var Tumbler Base, manufacturer - C&M Topline Inc., Goleta, California) was set at approximately 180 rpm. Abrasive wheels were directly pressed onto preformed phenolic cores to obtain a 1A1-type abrasive wheel sections with dimensions: outer diameter (OD) 8 inches (20.32 cm) × thickness (TC) 1.25 inches (3.17 cm) × inner diameter (ID) 1.25 inches (3.17 cm), with diamond depth x = 0.375. The matrix cavity consisted of five parts, the steel mold of the double seal for cutting rings was filled with a mixed abrasive composition while rotating the die matrix on a round table, while the mixture of abrasive powder was poured into an annular cavity around the core. The powder was then leveled and smoothed with a plastic molding tool, and the filled mold was closed using the upper ring die.

The filled mold was placed in a 200-ton hydraulic press with hot plates, the plates were heated to 350 degrees Fahrenheit (176.67 ° C). The press plates were closed so as to bring the surface of the annular press die to the same level with the mold. A magnetic thermometer was attached to the edge of the mold, and the temperature of the mold was monitored. When the temperature reached 350 ° F (176.67 ° C), the mold was kept under pressure in the closed state for 20 minutes.

After 20 minutes at 350 ° F (176.67 ° C), the mold was removed from the press with hot plates and placed on a water-cooled steel table, after which it was cooled to room temperature. The mold was removed from the formed section of the circle using a 50-ton hydraulic press and steel washers. The formed sections of the circle underwent air vulcanization in accordance with the following regulations. One hour - changing the temperature range to 150 degrees Fahrenheit (65.56 ° C), one hour - keeping at 150 ° F (65.56 ° C), 4 hours - changing the range to 350 ° F (176.67 ° C ), seven hours - keeping at 350 ° F (176.67 ° C), followed by 3 hours of cooling to room temperature.

The sections of the circle had a ground surface in thickness, then the two sections were glued together using epoxy glue. Then, the glued structure was ground and straightened using a 40/60 carborundum (SiC) grinding wheel on a leveling leveling machine ЗМ Е228 for manufacturing grinding wheels intended for final tests.

table 2 Grinding wheel composition Percentage by Weight Component Sample 1 Comparative sample 1A Comparative sample 2A Comparative Sample 3A Comparative Sample 4A Comparative Sample 6A Sample 7 Sample 9 Sample 10 Sample 11 Sample 12 Sample 13 Sample 14 NP1 0 19.5 NP2 8.4 0 19,4 18,4 16.5 18.2 8.4 8.3 16,2 16.3 NP3 8.4 0 8.4 8.3 SC 0 10.6 14.6 11.1 Sun 0 1.7 5,0 Cu 0 18.5 MO 0 1,5 RS1 3.9 0 4,5 4.3 2.1 3,5 3.9 3.8 3.8 PC2 3.9 0 3.9 1.9 With 0.7 0 0.6 1,1 0.9 0.7 0.6 0.5 0.7 0.7 0.7 0.7 321 12,2 0 14.0 13.3 7.7 11.3 12,2 8.0 321V 8.0 19.5 11.8 D1 0 34.5 38.8 16.5 21 D2 0 8.1 9.1 D3 0 2,8 3.2 D4 0 2,8 3.2 D5 23.6 0 25,2 23.5 20,4 20,0 D6 23.6 0 25,2 23.5 20,4 20,0 20,2 D7 15.3 0 23.5 D8 11.6 D9 48.7 NP4 14.1 12.1 16.1 SC 10,4 6.9 6.5 5.8 D10 13.5 D11 55.3 G 6.9 D12 16.5 21 D13 23.8 41,4 D14 18.8 D15 33.9 D16 204 D17 166 D18 20,2 19.8 200

Grindability Test

Cylindrical polycrystalline insert cutters (PDCs), obtained from US Synthetic Corporation, Orem, Utah, were the basis for use in a centerless grinding machine (model Acme Model 47 Centerless Grinder, Acme Manufacturing Company, Auburn Hills, state Michigan) using grinding wheels with a diameter of: 8 inches (20.32 cm) × 2.5 inches (6.35 cm) wide for Sample 1 and Comparative Example A. Insert diamond cutters (PDCs) were installed in a spring-loaded clamping device for them retention during the grinding process. The grinding wheel rotational speed was approximately 4000 SFPM (surface treatment speed in feet per minute, 1219 meters per minute), and the adjusting wheel speed was approximately 55 SFPM (16.76 m / min), and the incline of the cutter / spiral line was set to approximately 3 degrees. This design provided a contact time during grinding of approximately 5.5 seconds per single force of a polycrystalline diamond cutter (PDC). A Shell Metalina Y-850 5% cooling agent (Shell Lubricants, Houston, Texas) dissolved in water was used. Depending on the size of the polycrystalline diamond insert bits (PDCs), the test was carried out using either 2 polycrystalline insert bits (PDCs) in one effort, or 3 polycrystalline insert bits (PDCs) in one effort, as follows:

Test Format PDC Diameter Diamond Saturation at PDC Saturation carborundum on PDC 2 polycrystalline insertion cutters (PDCs) Nominal 0.63 in. (1.60 cm) 0.085 in. (0.22 cm) 0.4365 inches (1.11 cm) 3 polycrystalline insertion cutters (PDCs) Nominal 0.63 in. (1.60 cm) 0.062 inch (0.15 cm) 0.257 inch (0.65 cm)

The test was carried out using Comparative Example 1A, which confirmed that a design of 2 polycrystalline insertion cutters (PDC) gives the same level of material removal rate (polycrystalline inserts) as a design with 3 polycrystalline insertion cutters. The load on the electric motor during grinding was regulated in the range of 2.5-3.1 amperes within the load during machine idle time through the feed control using a control wheel. The test grinding wheels were corrected after each pass to high-frequency test the effect of dressing. In the low-frequency test of the dressing effect, each grinding wheel underwent a dressing process after every 10th pass. Editing was carried out manually when processing the circles with a white straight bar, grain size 220, dimensions: 1 inch (2.54 cm) × 1 inch (2.54 cm) × 6 inches (15.24 cm) (name "3M Dressing Stick 200TH" - “3M straight bar 200TN”, manufacturer - 3M Company, St. Paul, Minnesota) and moving the correct bar through the grinding wheel in just 6 passes.

Comparative example 1A is a prototype of a grinding wheel with a synthetic bonded abrasive material, provided for a fee by 3M, having the part number MMMRBDW26435-R. Comparative Examples 2A and 3A used non-agglomerated synthetic-bonded diamonds that crumbled strongly and quickly cut off the outer abrasive layer of the grinding wheel when grinding a polycrystalline diamond tool (PDC), which caused excessive grinding of the grinding wheel and poor grinding efficiency. Comparative Example 4A used the same diamond concentration as Comparative Example 1A, approximately 125, as well as crumbling soft filler particles instead of plastically deformable soft filler particles.

The need for editing was reduced, but slightly. Comparative Example 6A used the same 125 diamond concentration, but smaller diamond particles were replaced with larger diamond abrasive particles. No significant changes in performance were noted. Example 1 (185), example 7 (225), example 9 (200) and example 10 (200) used a significantly higher concentration of diamonds with a mixture of hard and soft filler particles, as described above. During the grinding test on polycrystalline diamond inserts (PDC), the need for dressing was significantly reduced.

Turning now to Figure 2, it should be noted that the cutting (grinding) speed of the inventive grinding wheel was significantly higher than that of comparative samples in which dressing was used in each pass (0.0027 cubic inches (0.044 cm ³ ) versus 0.0023 cubic inches (0.037 cm ³ )), in addition, the invented wheel had a good level of cutting (grinding) speed when dressing was used only after every 10th pass (0.0013 cubic inches (0.021 cm ³ ) versus 0.0008 cubic inches (0.013 cm ³ )). The cutting speed of the inventive grinding wheel, taking into account editing, only after every 10th pass was approximately 48% of the cutting speed with a single pass, versus 35% in comparative example 1A of the grinding wheel.

Example 1 was evaluated by a customer who produces polycrystalline diamond cutters (PDC) using centerless grinding. The use of centerless grinding reduces the outer diameter of polycrystalline diamond cutters (PDC) to the required final diameter / to the required tolerance, the grinding operation is carried out using a flowing cooling agent. The existing grinding wheel, which was previously used by the customer, required frequent or almost constant dressing of the abrasive medium in order to maintain the removal of the required layer using the existing abrasive diamond grinding wheel. When Example 1 of the grinding wheel was mounted on a centerless grinding machine, the polycrystalline diamond cutters (PDC) were machined taking into account the similar above grinding conditions with an abrasive diamond wheel, which was available from the customer. To Example 1, no external means were used to dress the grinding wheel during the centerless grinding of polycrystalline diamond cutters. Centerless grinding operations could be continued to process the polycrystalline diamond inserts (PDC) to the required final size using existing process parameters, while achieving the same performance standards without using grinding wheel dressing processes or without using regulatory tools on the surface of Example 1 grinding wheel during processing time for polycrystalline diamond inserts (PDC). Previously, the complete absence of the need to use tools for dressing was impossible in the existing processing modes for any of the previously used grinding wheels. Moreover, examples 1 of grinding wheels were used all the way to the core when grinding polycrystalline diamond inserts (PDC) and were not greasy or did not become inoperative at any stage of the grinding process.

Other modifications and variations of the present invention may be carried out by those skilled in the art without departing from the spirit and scope of the present invention, which are more specifically set forth in the appended claims. It should be understood that aspects of various embodiments of the present invention may be replaced in whole or in part or in combination with other aspects of various embodiments. All references, patents, or patent applications cited in the above patent application are hereby incorporated by reference in their entirety and in a consistent manner. In case of inconsistency or contradiction between the parts of the combined reference materials and this patent application, the information in the previous description should be checked. The previous description, given in order to enable any person skilled in the art to practice the claimed invention, should not be construed as limiting the scope of the entire invention, which is defined by the claims and all its equivalents.

Claims (8)

1. A method of grinding a polycrystalline diamond insert of a drill bit, including:
contacting the polycrystalline diamond insert with a grinding wheel,
including diamonds, a polymer binder and a mixture of solid filler particles and soft filler particles,
while diamonds have a diamond concentration of 175 to 225, a polymer binder is from 30 to 40 vol.%, a mixture of solid filler particles and soft filler particles is from 5 to 30 vol.%, and the ratio of solid filler particles to soft filler particles in the mixture ranges from 85:15 to 15:85. 2. The method according to p. 1, in which the ratio between the solid particles of the filler and the soft particles of the filler in the mixture is from 70:30 to 30:70. 3. The method of claim 1, wherein the diamonds are metal-bonded diamonds. 4. The method of claim 2, wherein the solid filler particles are ceramic alpha alumina particles and the soft filler particles are petroleum coke. 5. An abrasive product for grinding a polycrystalline diamond insert of a drill bit, made in the form
a grinding wheel consisting of diamonds, a polymer bond, and
a mixture of solid particles and soft filler particles, while
diamonds have a concentration of from 175 to 225, a polymer binder is from 30 to 40 vol.%, and the mixture of solid filler particles and soft filler particles is from 5 to 30 vol.%, and the ratio of solid filler particles to soft filler particles in the mixture is from 85:15 to 15:85. 6. The abrasive product according to claim 5, in which the ratio of the solid particles of the filler and the soft particles of the filler in the mixture is from 70:30 to 30:70. 7. The abrasive product according to claim 5, in which the diamonds are diamonds on a metal bond. 8. The abrasive article of claim 5, wherein the solid filler particles are ceramic alpha alumina particles and the soft filler particles are petroleum coke.

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