Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D5/00—Bonded abrasive wheels, or wheels with inserted abrasive blocks, designed for acting only by their periphery; Bushings or mountings therefor
  • B24D5/10—Bonded abrasive wheels, or wheels with inserted abrasive blocks, designed for acting only by their periphery; Bushings or mountings therefor with cooling provisions, e.g. with radial slots
• • 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
  • B24B55/00—Safety devices for grinding or polishing machines; Accessories fitted to grinding or polishing machines for keeping tools or parts of the machine in good working condition
  • B24B55/02—Equipment for cooling the grinding surfaces, e.g. devices for feeding coolant
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D5/00—Bonded abrasive wheels, or wheels with inserted abrasive blocks, designed for acting only by their periphery; Bushings or mountings therefor
  • B24D5/16—Bushings; Mountings

Definitions

• bonded abrasive articles are made by compressing a blend of abrasive particles (e.g., diamond, cubic boron nitride, alumina, or SiC), a binder precursor (e.g., vitreous, metal, or resin), an optional pore inducer (e.g., glass bubbles, naphthalene, crushed coconut or walnut shells, or acrylic glass or PMMA), and a temporary organic binder in a liquid vehicle (e.g., aqueous solutions of phenolic resin, polyvinyl alcohol, urea-formaldehyde resin, or dextrin).
• abrasive particles e.g., diamond, cubic boron nitride, alumina, or SiC
• a binder precursor e.g., vitreous, metal, or resin
• an optional pore inducer e.g., glass bubbles, naphthalene, crushed coconut or walnut shells, or acrylic glass or PMMA
• the abrasive particles, bond precursor, and, usually, the pore inducer are typically dry blended together.
• the temporary organic binder solution is then added to wet out the grain mix.
• the blended mix is then placed in a hardened steel mold treated with a mold release agent and pressed to reach a predefined volume.
• the pressed part is then removed from the mold in a green stage and put in an oven or furnace to be heated until the permanent binder is fully set.
• a grinding system includes a grinding wheel with a coolant channel coupled to a coolant exit.
• the coolant channel extends through a grinding layer of the grinding wheel.
• the coolant exit is on an active grinding surface of the grinding wheel.
• the grinding system also includes a mounting feature configured to couple the grinding wheel to a grinding machine.
• the grinding system also includes a coolant distribution component configured to receive coolant and provide it through the coolant channel to the coolant exit point.
• abrasive articles with such systems may reduce or even prevent surface burning and / or damage of a workpiece subsurface during an abrading operation. Additionally, a customer sees a better cost per cut value because of higher cutting performance due to reduced grinding force and lower temperature in the grinding zone.
• FIGS. 1A-1B illustrate prior art methods ofproviding coolant to an abrasive process.
• FIG. 2A-2D illustrates an abrasive article with coolant providing feature in accordance with embodiments herein.
• FIG. 3 illustrates an example nozzle for a grinding system in accordance with embodiments herein.
• FIGS. 4A-4D illustrate a grinding wheel with a shaft-based coolant delivery system made in accordance with embodiments herein.
• FIGS. 5A-5B illustrates an alternative abrasive article with a shaft-based coolant delivery system in accordance with embodiments herein.
• FIGS. 6 illustrates a method of conducting an abrasive grinding operation in accordance with embodiments herein.
• FIGS 7A-7E illustrate views of an abrading system in accordance with embodiments herein.
• FIG. 8 illustrates an abrasive system as described in further detail in the Examples.
• coolant reduces undesired mechanical, thermal and chemical impact between an abrasive particle and the workpiece being abraded, as well as facilitating removal of debris and worn mineral out of the contact area.
• Lubricant reduces friction between the materials and cools the grinding process area by absorbing and transporting heat generated during grinding away from the process area. If sufficient coolant is not present, the risk of surface burning and / or damage to the subsurface of the workpiece being abraded is high.
• One goal of abrasive article design is to manage coolant delivery, both to and from a work area, so that enough coolant is available to an active grinding area as needed. As discussed below, embodiments of the present invention achieve this by modifying the abrasive article design. For example, some embodiments use internal coolant features designed to capture coolant from an external source and deliver it to an active grinding area.
• FIGS. 1A-1B illustrate prior art methods ofproviding coolant to an abrasive process.
• Internal grinding processes such as process 10 of FIG. 1A, illustrate challenges for coolant delivery.
• nozzles such as nozzle 12 are used to direct cooling into an internal grinding area.
• space for nozzles 12 are limited and the contact length between the abrasive article and the workpiece is high.
• the quantity of coolant reaching the active grinding zone is not enough to sufficiently cool the grinding area, maintain sufficient lubrication, and flush away abraded material.
• Nozzle 40 is designed such that an outlet 42 substantially contacts abrasive wheel 41.
• a significant drawback of a separate nozzle structure is the need for the nozzle to be close to the grinding zone, as illustrated in FIG. 1 A, without taking up space occupied by the abrasive article.
• it may be possible to deliver a sufficient quantity of coolant through a nozzle it is often difficult to deliver the coolant consistently to the right place, i.e. the grinding zone
• Coolant is delivered through the specially designed grinding wheel center (e.g. through a shaft or adapted connection feature) and then passes through the grinding wheel through holes in the abrasive layer.
• a specially designed grinding wheel spindle e.g. through a shaft or adapted connection feature
• Embodiments described herein solve the coolant delivery problem by driving coolant to an abrading contact zone by providing an adapter that retrieves coolant from an external or internal source and provides it to internal coolant structures of an abrasive grinding wheel.
• Some embodiments accomplish this by collecting fluid from the standard environment such that the fluid is captured from a supply, accelerated through a design feature within the grinding wheel, and then redistributed to the grinding zone through openings in an active layer of the grinding wheel.
• the openings may be located to take advantage of acceleration by the design feature(s).
• the supply can either be an external supply, such as from a nozzle 20, or from an internal drive shaft of process 10.
• abrasive articles may include impellers inside the grinding wheel itself, as well as cooling channels and holes. These features may be printed into the wheel using powder bed binder jetting.
• Powder bed binder jetting is an additive manufacturing, or "3D printing" technology, in which a thin layer of a powder is temporarily bonded at desired locations by a jetted liquid binder mixture.
• that binder mixture is dispensed by a bindeijet printing head, and consists of a polymer dissolved in a suitable solvent or carrier solution.
• the binder is a powder which is mixed with the other powder, or coated onto the powder and dried, and then an activating liquid, such as water or a solvent mixture, is jetted onto the powder, activating the binder in select areas.
• the printed powder layer is then at least partially dried and lowered so that a next powder layer can be spread. The powder spreading, bonding and drying processes can be repeated until the full object is created.
• the object and surrounding powder is removed from the printer and often dried or cured to impart additional strength so that the now hardened object can be extracted from the surrounding powder prior to final curing or sintering.
• One benefit of additive manufacturing, particularly through powder bed binder jetting is the ability to design internal coolant delivery channels that can provide coolant from a source, through an interior of an abrasive article, and along an exterior of an article, in fluid flow patterns that would be prohibitively expensive to machine or mold into an abrasive article using traditional methods.
• Some example methods and systems for powder bed binder jetting are described in PCT Publication No. WO 2020/128779, published on June 25, 2020, and in PCT Publication IB 2020/055913, filed on June 23, 2020, both of which are incorporated herein by reference.
• Bevel gear plunge grinding operations are specifically difficult for the coolant to reach the grinding area as the space for the nozzle is limited and the contact length between the workpiece and the abrasive article is high. Forthat reason, the quantity of coolant which can reach the active grinding zone could be poor and therefore cannot sufficiently cool, lubricate, flush and transport chip/swarf. Usually the quantity of fluid delivered is large enough; the challenge is to have it on the right place.
• Machine builders have attempted to solve this issue by multiplying the numbers of pipes coming from outside of the grinding zone, increasing the amount of coolant using high pressure nozzles, but still high porosity wheels and adapted grinding parameters are needed to avoid damages on the surface or sub-surface of the ground piece.
• Described herein are systems and methods for driving coolant collected from the environment to the contact zone through the grinding layer. Effectively, the fluid is captured from a standard supply, accelerated into a specifically designed feature included in the grinding wheel, and redistributed to the grinding zone via openings in the active grinding layer, located in the acceleration zones. In some embodiments, like cup wheels for bevel gear grinding, specific nozzle designs are also provided.
• Systems and method are desired for providing sufficient coolant flow to coolant features of an abrasive article to provide adequate cooling during an abrading operation.
• FIG. 2A-2D illustrate an abrasive article with coolant providing feature in accordance with embodiments herein.
• System 100 is configured to receive coolant from a source through nozzle 102.
• the coolant is provided to an active grinding layer 110 through a nozzle receiving point 132, which provides coolant from nozzle 102 to coolant reservoir portions 134, and then to internal coolant features 150, from which it exits through coolant exit holes 152.
• Coolant reservoir component 130 couples to a mounting plate 120 through mounting features 124. Active grinding surface 110 spins during a grinding operation, while mounting plate 120 and nozzle receiving points 132 remain stationary. A drive shaft responsible for spinning the abrasive article and causing grinding surface 110 to abrade a worksurface is received by bore 122.
• FIG. 2B which illustrates a cutaway view of coolant reservoir component 130, illustrating a plurality of coolant reservoir portions 134 and part of a turbofan structure 160.
• the internal coolant features 150 provide coolant from coolant reservoir portions 134 through an abrasive article structure before providing it to an abrading surface 110 using coolant exit holes 152.
• the internal coolant features 150 are coolant channels 154, for example either tortuous or arcuate coolant channels.
• the coolant reservoir component 130 is configured to fit to an existing mounting plate 120, such that existing machinery can be retrofitted to better supply coolant through an abrasive article to an abrading surface using system 100.
• FIG. 2D illustrates a cutaway view of a system 100, illustrating how coolant reservoirs 134 receive fluid from nozzle receiving points 132.
• FIG. 3 illustrates an example nozzle for a grinding system in accordance with embodiments herein.
• a specialized nozzle 200 is used to provide coolant from an external source into an abrasive system. While some abrading systems may have a coolant receiving component that can accept standard nozzles, it may be beneficial to have a specially designed nozzle that fits into a coolant receiving point of a coolant component. This may help ensure that coolant flows directly through an abrasive article and onto an abrading area. As the shape of nozzle 200 conforms closely to the grinding wheel size and shape, it reduces loss of coolant and consequent pressure drop, compared to a flat opening. The shape of nozzle 200 also accelerates the fluid having a minimum pressure drop due to turbulences. Therefore, the flow pressure is transformed into flow rate.
• the design of a nozzle opening may, as illustrated in FIG. 3, contain an asymmetrical nozzle opening to ensure that nozzle 200 is insertable only in one direction, creating a lock- and-key combination of nozzle and nozzle receiving point.
• the opening in the grinding wheel is designed to increase an amount the flow going into the grinding wheel and not on the faces.
• the nozzle shape is then designed to fit.
• the opening shape may vary depending on the fluid being used and the application.
• the nozzle entrance may be placed anywhere around the 360° exterior that is convenient for a customer.
• the nozzle design may also be adjusted to decrease the intensity of turbulence in the flow through an abrasive article.
• Nozzle 200 has a nozzle length 210, which extends from a coolant receiving end to a coolant delivery end.
• Coolant delivery end has a nozzle width 220 and a height that may vary from edge to edge, for example form an edge height 204 to a maximum height 202. While FIG. 3 illustrates an embodiment where an edge height 204 is a minimum height of a delivery opening of nozzle 200, it is expressly contemplated that, in some embodiments, a minimum nozzle height is located elsewhere along length 220.
• FIGS. 4A-4E illustrate a grinding wheel with a shaft-based coolant delivery system made in accordance with embodiments herein.
• a coolant distribution component can distribute fluid received from the spindle through an abrasive article and out coolant exit holes in the surface of the abrasive article such that the coolant is delivered to the abrading area.
• FIGS. 4A-4D illustrate a bevel grinding wheel receiving an internal coolant supply delivered through a machine spindle.
• Some grinding machines may have an ability to dispense coolant through a spindle in the driveshaft, such that coolant can flow through the abrasive article without the need of an external source.
• an alternate abrading system 300 may be more suitable than abrading system 100.
• Abrading system 300 includes a spindle shaft connection 310 with a shaft mounting point 312 that receives a drive shaft of an abrading article.
• Spindle shaft connection 310 connects to a mounting plate 320, which, along with coolant distribution component 330, remains stationary during an abrading operation, in some embodiments.
• FIG. 4A illustrates the full abrading assembly 300.
• FIG. 4B illustrates a cutaway view of coolant distribution component 330, just below mounting plate 320, and FIG. 4B illustrates a second cutaway view of the coolant distribution component 330, closer to the connection plane between component 330 and abrading article with surface 340.
• a coolant distribution component 330 provides coolant received through the spindle shaft connection 310 and, as illustrated in FIGS. 4B and 4C at coolant receiving points 314, into coolant chambers 316, which then provide coolant to coolant distribution points 318, which connect to internal coolant delivery features within the abrading article with abrading surface 340. Coolant then exits the abrading article through coolant delivery points 350.
• FIG. 4D illustrates a cutaway view 360, cut perpendicularly to the coolant distribution component 330 and through a spindle.
• a fluid path includes fluid flowing from the spindle, into the coolant distribution component 330, into coolant chambers 316, where it is provided to internal coolant chambers 316 where it flows through the abrasive article until it reaches an exit point 350.
• FIGS. 5A-5B illustrate an alternative abrasive article with a shaft-based coolant delivery system in accordance with embodiments herein.
• Bevel grinding systems are illustrated in, and have been discussed with respect to FIGS. 1, 2 and 4 thus far, however it is expressly contemplated that such systems may be useful for other grinding systems as well.
• a single rib gear grinding wheel is illustrated in FIGS. 5A-5B.
• Abrading system 400 includes a shaft spindle connection 410, that receives coolant from a machine spindle or from a flange and provides it to a coolant distribution component 430 which, similar to coolant distribution components 130 and 330, receives coolant and provides it to coolant chambers 416, where it is distributed through the abrasive article at coolant distribution points 418 before exiting an abrading surface 440.
• One or more internal delivery features 442 provide the coolant from coolant distribution points 418 to coolant delivery point 450.
• the fluid path 470 is illustrated in cutaway view 460 of FIG. 5B.
• the design for a single rib gear grinding wheel should take into account the other geometry for such type of wheel.
• the coolant distribution component 430 includes a turbine shape that captures the fluid close to a tangential way nearly parallel to the grinding wheel face and turn the flow at 90° to have it axially distributed. Then, inside of the grinding wheel, the flow should turn again by 90° for having it ejected via the openings which are distributed along the periphery of the grinding wheel. Similar considerations are also applicable to other applications such as profile grinding, creep feed grinding, reciprocating grinding, tool flute grinding, etc.
• an entry of the fluid coming through the spindle can be designed which should even increase the efficiency of the coolant flow coming out of the openings.
• FIGS. 6 illustrates a method of conducting an abrasive grinding operation in accordance with embodiments herein.
• Method 500 may be useful for providing coolant through an abrasive article using a coolant distribution component coupled to the abrasive article.
• a fluid connection source is coupled to an abrasive article.
• the abrasive article is an abrasive grinding wheel, for example a vitreous, resin, or metal-bonded abrasive grinding wheel.
• the abrasive grinding wheel is a bevel gear grinding wheel, a cup grinding wheel, a single rib gear grinding wheel, a double ball bearing outer ring grinding wheel, a threaded gear grinding wheel, a face grinding wheel, a double face grinding wheel, a fine grinding wheel, an internal-diameter grinding wheel, a grinding cup wheel, a threaded wheel, a cylindrical wheel, a profiled wheel, or another suitable grinding wheel. Any of these, or other suitable, grinding wheels and processes could be modified with any suitable abrasive particle size to facilitate rough, finishing and super finishing operations.
• Connecting a fluid source may include coupling a coolant distribution component directly to the abrasive article. Fluid may then be provided through the coolant distribution component from a nozzle 512, through a machine spindle 516, or another suitable mechanism 516.
• coolant flow is initiated. Coolant flow may be initiated at the same time, before, or after an abrasive article actuates. Actuation may include, for example, a grinding wheel rotationally contacting a worksurface.
• a coolant distribution component may, in some embodiments, remain stationary while the abrasive article rotates, for example being coupled to the abrasive article through the drive shaft of a machine which causes the abrasive article to rotate but allows the coolant distribution component to remain stationary. In other embodiments, the coolant distribution component rotates with the abrasive article.
• Initiating coolant flow may cause coolant to flow from a fluid source, such as a nozzle 512 or through a machine spindle 514, through a coolant delivery component, which may have internal geometry 526 configured to cause turbulent flow of the coolant. Coolant may then be provided through interior channels 522 of the abrasive article, or flow along exterior channels cut into an abrasive surface of the abrasive article. Other flow patterns are also envisioned, for example through internal turbine or other structures of the abrasive article.
• abrasive articles with an active grinding surface layer configured to abrade a surface of a workpiece.
• the abrasive properties of the active grinding layer can be customized, for example diameter, height, abrasive wheel thickness, grit size, abrasive particle size and density within the grinding layer, etc.
• the abrasive article may have an internal bore, configured to allow the abrasive article to be mounted on a machine shaft.
• the abrasive article may have multiple receiving points for bolting screws, such as used for face grinding wheels.
• the abrasive article may have its own internal reservoir configured to collect coolant from a coolant distribution component. Located within internal reservoir may be one or more acceleration features configured to accelerate coolant.
• the acceleration feature may be a turbofan. However, other possible designs for acceleration feature are specifically contemplated.
• the acceleration feature may use the rotation of the grinding wheel to increase the speed and / or pressure of provided coolant to ensure that it is delivered to an active grinding area.
• the abrasive article may have a vitreous, metal-based or resin bond that holds abrasive particles in place within a bond matrix. While some of the discussion herein focuses on the example of a vitreous bonded abrasive article, it is expressly contemplated that other binders, such as metal-based bond or a resin-based bond, are also possible in some embodiments of the present invention.
• Abrasive articles described herein include openings in the abrasive layer that provide coolant to a contact zone. Additionally, channels, extending internally throughout, and externally across an abrasive article may assist in distributing coolant throughout the external surface area of a grinding wheel. While curved channels have been illustrated herein, resulting in rectangular openings, it is also expressly contemplated that other suitable shapes and designs may be possible, or even desired, based on the parameters of an abrading operation.
• Acceleration feature designs within a coolant distribution component may contain a variety of features in addition to, or instead of, coolant chambers illustrated herein.
• the coolant distribution component may contain one or more blades.
• blades may resemble those used in axial fans, centrifugal fans, turbo fans, axial pumps, centrifugal pumps and turbo chargers. Additionally, in some embodiments, the blades can be straight, or curved clockwise or counterclockwise. Additionally, in some embodiments, the blades are twisted. Each blade may extend along a length of the coolant distribution component, extending from a central bore, effectively separating the coolant distribution component’s interior into a plurality of reservoir portions, in one embodiment.
• each blade only extends partway into a reservoir.
• Each blade may have a flat surface or a curved surface. While a central bore is illustrated in some embodiments here, it is expressly contemplated that, in some embodiments, some or all of the coolant is provided from an external source into the coolant distribution component for distribution.
• abrasive grinding wheels having an active grinding layer that can be customized based on the needs of an abrasive operation.
• diameter, height, abrasive article thickness, abrasive particle type, size, and concentration; wheel layer profile and shape, etc. are all customizable variables of an abrasive wheel.
• an abrasive wheel for threading operation may have one or more threads.
• an internal bore of an abrasive wheel may be sized to fit a machine shaft.
• Methods of making bonded abrasive articles according to the present disclosure include an additive subprocess.
• the subprocess comprises sequentially, preferably consecutively (although not required) carrying out at least three steps.
• a layer of loose powder particles is deposited .
• Each layer should be of substantially uniform thickness.
• the thickness of the layer may be less than 500 microns, less than 300 microns, less than 200 microns, or less than 100 microns.
• the layers may have any thickness up to about 1 millimeter, as long as the jetted liquid binder precursor material can bind all the loose powder where it is applied.
• the thickness of the layer is from about 10 microns to about 500 microns, 10 microns to about 250 microns, about 50 microns to about 250 microns, or from about 100 microns to about 200 microns.
• the loose powder particles comprise vitreous bond precursor particles and abrasive particles.
• the vitreous bond precursor particles may comprise particles of any material that can be thermally converted into a vitreous material. Examples include glass frit particles, ceramic particles, ceramic precursor particles, and combinations thereof.
• the vitreous bond which binds together the abrasive grain in accordance with this disclosure can be of any suitable composition which is known in the abrasives art, for example.
• the vitreous bond phase also variously known in the art as a “ceramic bond”, “vitreous phase”, vitreous matrix”, or “glass bond” (e.g., depending on the composition) may be produced from one or more oxides (e.g., a metal oxide and/or boria) and/or at least one silicate as frit (i.e., small particles), which upon being heated to a high temperature react to form an integral vitreous bond phase.
• oxides e.g., a metal oxide and/or boria
• silicate as frit i.e., small particles
• glass particles e.g., recycled glass frit, water glass frit
• silica frit e.g., sol-gel silica frit
• alumina trihydrate particles e.g., alumina particles, zirconia particles, and combinations thereof.
• Suitable frits, their sources and compositions are well known in the art.
• Abrasive articles are typically prepared by forming a green structure comprised of abrasive grain, the vitreous bond precursor, an optional pore former, and a temporary binder. The green structure is then fired.
• the vitreous bond phase is usually produced in the firing step of the process for producing the abrasive article of this disclosure. Typical firing temperatures are in the range of from 540°C to 1700°C (1000°F to 3100°F). It should be understood that the temperature selected for the firing step and the composition of the vitreous bond phase must be chosen so as to not have a detrimental effect on the physical properties and/or composition of abrasive particles contained in the vitreous bond abrasive article.
• Useful glass frit particles may include any glass frit material known for use in vitreous bond abrasive articles. Examples include glass frit selected from the group consisting of silica glass frit, silicate glass frit, borosilicate glass frit, and combinations thereof.
• a typical vitreous binding material contains about 70 - 90% SiOa + B2O3, 1-20% alkali oxides, 1-20% alkaline earth oxides, and 1-20% transition metal oxides.
• the vitreous binding material has a composition of about 82 wt% SiCh + B2O3, 5% alkali metal oxide, 5% transition series metal oxide, 4% AI2O3, and 4% alkaline earth oxide.
• a frit having about 20% B2O3, 60% silica, 2% soda, and 4% magnesia may be utilized as the vitreous binding material.
• a frit having about 20% B2O3, 60% silica, 2% soda, and 4% magnesia may be utilized as the vitreous binding material.
• the particular components and the amounts of those components can be chosen in part to provide particular properties of the final abrasive article formed from the composition.
• the size of the glass frit can vary. For example, it may be the same size as the abrasive particles, or different. Typically, the average particle size of the glass frit ranges from about 0.01 micrometer to about 100 micrometers, preferably about 0.05 micrometer to about 50 micrometers, and most preferably about 0. 1 micrometer to about 25 micrometers. The average particle size of the glass frit in relation to the average particle size of the abrasive particles having a Mohs hardness of at least about 5 can vary. Typically, the average particle size of the glass frit is about 1 to about 200 percent of the average particle size of the abrasive, preferably about 10 to about 100 percent, and most preferably about 15 to about 50 percent.
• the weight ratio of vitreous bond precursor particles to abrasive particles in the loose powder particles ranges from about 10:90 to about 90: 10.
• the shape of the vitreous bond precursor particles can also vary. Typically, they are irregular in shape (e.g., crushed and optionally graded), although this is not a requirement. For example, they may be spheroidal, cubic, or some other predetermined shape.
• the coefficient of thermal expansion of the vitreous bond precursor particles is the same or substantially the same as that of the abrasive particles.
• Glassy inorganic binders may be made from a mixture of different metal oxides.
• these metal oxide vitreous binders include silica, alumina, calcia, iron oxide, titania, magnesia, sodium oxide, potassium oxide, lithium oxide, manganese oxide, boron oxide, phosphorous oxide, and the like.
• vitreous binders based upon weight include, for example, 47.61 percent SiCh, 16.65 percent AI2O3, 0.38 percent Fe2O3, 0.35 percent TiCh, 1.58 percent CaO, 0.10 percent MgO, 9.63 percent Na2O, 2.86 percent K2O, 1.77 percent Li2O, 19.03 percent B2O3, 0.02 percent MnCh, and 0.22 percent P2O5; and 63 percent SiCh, 12 percent AI2O3, 1.2 percent CaO, 6.3 percent Na2O, 7.5 percent K2O, and 10 percent B2O3.
• One preferred vitreous bond has an oxide-based mole percent (%) composition of SiCh 63.28; TiO 2 0.32; AI2O3 10.99; B2O3 5.11; Fe 2 O 3 0.13; K2O 3.81; Na 2 O 4.20; Li 2 O 4.98; CaO 3.88; MgO 3.04 and BaO 0.26. Firing of these ingredients is typically accomplished by raising the temperature from room temperature to 1149° C (2100° F) over a prolonged period of time (e.g., about 25-26 hours), holding at the maximum temperature (e.g., for several hours), and then cooling the fired article to room temperature over an extended period of time (e.g., 25-30 hours).
• the vitreous bond precursor particles may comprise ceramic particles. In such cases sintering and/or fusing of the ceramic particles forms the vitreous matrix. Any sinterable and/or fusible ceramic material may be used. Preferred ceramic materials include alumina, zirconia, and combinations thereof.
• the vitreous bond precursor particles may be present in an amount from 10 to 40 volume percent of the combined volume of the vitreous bond precursor particles and abrasive particles, preferably from 15 to 35 volume percent of the abrasive composition.
• suitable metal binders include tin, copper, aluminum, nickel, iron, tungsten, cobalt, titanium, manganese, silver and combinations thereof.
• Suitable resin binders include formaldehyde-containing resins, such as phenol formaldehyde, novolac phenolics and especially those with added crosslinking agent (e.g., hexamethylenetetramine), phenoplasts, and aminoplasts; unsaturated polyester resins; vinyl ester resins; alkyd resins, allyl resins; furan resins; epoxies; polyurethanes; cyanate esters; and polyimides.
• the amount of resin should be sufficient to fully wet the surfaces of all the individual particles during manufacturing such that a continuous resin structure is formed with the inorganic components discretely bonded throughout.
• alpha-alumina ceramic particles may be modified with oxides of metals such as magnesium, nickel, zinc, yttria, rare earth oxides, zirconia, hafnium, chromium, or the like.
• Alumina and zirconia abrasive particles may be made by a sol-gel process, for example, as disclosed in U.S. Pat. Nos. 4,314,827 (Leitheiser et al.); 4,518,397 (Leitheiser et al.); 4,574,003 (Gerk); 4,623,364 (Cottringeret al.); 4,744,802 (Schwabel); and 5,551,963 (Larmie).
• additives in the making of bonded abrasive articles both to assist in the making of the abrasive article and/or improve the performance of such articles.
• Such conventional additives which may also be used in the practice of this disclosure include but are not limited to lubricants, fillers, pore inducers, and processing aids.
• lubricants include, graphite, sulfur, polytetrafluoroethylene and molybdenum disulfide.
• fillers include secondary abrasive, carbides, nitrides, oxides or metal based particles.
• pore inducers include glass bubbles and organic particles. Concentrations of the additives as are known in the art may be employed for the intended purpose of the additive, for example. Preferably, the additives have little or no adverse effect on abrasive particles employed in the practice of this disclosure.
• the loose powder particles may optionally be modified to improve their flowability and the uniformity of the layer spread.
• Methods of improving the powders include agglomeration, spray drying, gas or water atomization, flame forming, granulation, milling, and sieving. Additionally, flow agents such as, for example, fumed silica, nanosilica, stearates, and starch may optionally be added.
• the bond precursor particles may comprise a ceramic precursor (e.g., a precursor of alumina or zirconia) such as, for example, bauxite, boehmite, calcined alumina, or calcined zirconia that when fired converts to the corresponding ceramic form.
• a ceramic precursor e.g., a precursor of alumina or zirconia
• bauxite, boehmite calcined alumina, or calcined zirconia that when fired converts to the corresponding ceramic form.
• Procedures and conditions known in the art for producing bonded abrasive articles may be used to make the abrasive articles of this disclosure. These procedures may employ conventional equipment well-known in the art.
• the abrasive particles may comprise any abrasive particle used in the abrasives industry.
• the abrasive particles have a Mohs hardness of at least 4, preferably at least 5, more preferably at least 6, more preferably at least 7, more preferably at least 8, more preferably at least 8.5, and more preferably at least 9.
• the abrasive particles comprise superabrasive particles.
• the term "superabrasive” refers to any abrasive particle having a hardness greater than or equal to that of silicon carbide (e.g., silicon carbide, boron carbide, cubic boron nitride, and diamond).
• suitable abrasive materials include aluminum oxide (e.g., alpha alumina) materials (e.g., fused, heat-treated, ceramic, and/or sintered aluminum oxide materials), silicon carbide, titanium diboride, titanium nitride, boron carbide, tungsten carbide, titanium carbide, aluminum nitride, diamond, cubic boron nitride (CBN), garnet, fused alumina-zirconia, sol-gel derived abrasive particles, cerium oxide, zirconium oxide, titanium oxide, and combinations thereof. Examples of sol-gel derived abrasive particles can be found in U.S. Pat. No. 4,314,827 (Leitheiser et al.), U.S.
• sol-gel derived abrasive particles can be found in U.S. Pat. No. 4,314,827 (Leitheiser et al.), U.S.
• Shaped abrasive particles according to the present disclosure may be used in a wide range of particle sizes, typically ranging in size from about 10 to about 10000 microns; preferably from about 100 to about 10000 microns, more preferably from about 500 to about 10000 microns, although this is not a requirement.
• the shaped abrasive particles have an average particle size of at least 20 U.S. mesh (i.e., > about 840 microns).
• Shaped abrasive particles according to the present disclosure can be screened and graded using techniques well known in the art, including the use of an abrasives industry recognized grading standards such as ANSI (American National Standard Institute), FEPA (Federation of European Producers of Abrasives), and JIS (Japanese Industrial Standard).
• ANSI American National Standard Institute
• FEPA Federation of European Producers of Abrasives
• JIS Japanese Industrial Standard
• ANSI grade designations include: ANSI 4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 36, ANSI 40, ANSI 50, ANSI 60, ANSI 80, ANSI 100, ANSI 120, ANSI 150, ANSI 180, ANSI 220, ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI 600.
• FEPA grade designations include P8, P12, P16, P24, P36, P40, P50, P60, P80, P100, P120, P150, P180, P220, P320, P400, P500, P600, P800, P1000, and P1200.
• JIS grade designations include JIS8, JIS 12, JIS16, JIS24, JIS36, JIS46, JIS54, JIS60, JIS80, JIS100, JIS150, JIS 180, JIS220, JIS240, JIS280, JIS320, JIS360, JIS400, JIS400, JIS600, JIS800, JIS 1000, JIS 1500, JIS2500, JIS4000, JIS6000, JIS8000, and JIS 10,000.
• the loose powder particles may be sized (e.g., by screening) to have a maximum size of less than or equal to 400 microns, preferably less than or equal to 250 microns, more preferably less than or equal to 200 microns, more preferably less than or equal to 150 microns, less than or equal to 100 microns, or even less than or equal to 80 microns, although larger sizes may also be used.
• the size of the powder particles may relate to the size of the abrasive particle used.
• the vitreous bond precursor particles, abrasive particles, and any optional additional particulate components may have the same or different maximum particle sizes, D90, D50, and/or D10 particle size distribution parameters.
• the loose powder particles may optionally further comprise other components such as, for example, pore inducers, and/or fdler particles.
• pore inducers include glass bubbles and organic particles.
• a liquid binder precursor material is jetted by printer onto predetermined region(s) of the layer deposited in step 1.
• the liquid binder precursor material thus coats the loose powder particles in region, and is subsequently converted to a binder material that binds the loose powder particles in region to each other.
• the liquid binder precursor material may be any composition that can be converted (e.g., by evaporation, or thermal, chemical, and/or radiation curing (e.g., using UV or visible light)) into a binder material that bonds the loose powder particles together according to the jetted pattern (and ultimate 3-D shape upon multiple repetitions).
• the liquid binder precursor material comprises a liquid vehicle having a polymer dissolved therein.
• the liquid may include one or more of organic solvent and water.
• Exemplary organic solvents include alcohols (e.g., butanol, ethylene glycol monomethyl ether), ketones, and ethers, preferably having a flash point above 100°C.
• a suitable solvent or solvents will typically depend upon requirements of the specific application, such as desired surface tension and viscosity, the selected particulate solid, for example.
• the liquid vehicle can be entirely water, or can contain water in combination with one or more organic solvents.
• the aqueous vehicle contains, on a total weight basis, at least 20 percent water, at least 30 percent water, at least 40 percent water, at least 50 percent water, or even at least 75 percent water.
• one or more organic solvents may be included in the liquid vehicle, for instance, to control drying speed of the liquid vehicle, to control surface tension of the liquid vehicle, to allow dissolution of an ingredient (e.g., of a surfactant), or, as a minor component of any of the ingredients; e.g., an organic co-solvent may be present in a surfactant added as an ingredient to the liquid vehicle.
• an ingredient e.g., of a surfactant
• an organic co-solvent may be present in a surfactant added as an ingredient to the liquid vehicle.
• Exemplary organic solvents include: alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, and isobutyl alcohol; ketones or ketoalcohols such as acetone, methyl ethyl ketone, and diacetone alcohol; esters such as ethyl acetate and ethyl lactate; polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, 1,4-butanediol, 1,2,4-butanetriol, 1,5- pentanediol, 1,2,6-hexanetriol, hexylene glycol, glycerol, glycerol ethoxylate, trimethylolpropane ethoxylate; lower alkyl ethers such as ethylene glycol methyl or ethyl
• the amounts of organic solvent and/or water within the liquid vehicle can depend on a number of factors, such as the particularly desired properties of the liquid binder precursor material such as the viscosity, surface tension, and/or drying rate, which can in turn depend on factors such as the type of ink jet printing technology intended to be used with the liquid vehicle ink, such as piezo-type or thermal -type printheads, for example.
• the liquid binder precursor material may include a polymer that is soluble or dispersible in the liquid vehicle.
• suitable polymers may include polyvinyl pyrrolidones, polyvinyl caprolactams, polyvinyl alcohols, polyacrylamides, poly(2-ethyl-2- oxazoline) (PEOX), polyvinyl butyrate, copolymers of methyl vinyl ether and maleic anhydride, certain copolymers of acrylic acid and/or hydroxyethyl acrylate, methyl cellulose, natural polymers (e.g., dextrin, guar gum, xanthan gum).
• PEOX poly(2-ethyl-2- oxazoline)
• polyvinyl butyrate copolymers of methyl vinyl ether and maleic anhydride
• acrylic acid and/or hydroxyethyl acrylate methyl cellulose
• natural polymers e.g., dextrin, guar gum, xanthan gum.
• the liquid binder precursor material may include one or more free -radically polymerizable or otherwise radiation-curable materials; for example, acrylic monomers and/or oligomers and/or epoxy resins.
• An effective amount of photoinitiator and/or photocatalysts for curing the free-radically polymerizable or otherwise radiation-curable materials may also be included.
• suitable (meth)acrylate monomers and oligomers and otherwise radiation-curable materials e.g., epoxy resins
• suitable (meth)acrylate monomers and oligomers and otherwise radiation-curable materials can be found in, for example, U.S. Pat. No. 5,766,277 (DeVoe et al.).
• the liquid binder precursor material is essentially free of (e.g., contains less than 1 percent, less than 0.1 percent, less than 0.01 percent, or is even free of) metal nanoparticles and/or metal oxide nanoparticles.
• nanoparticles refers to particles having an average particle diameter of less than or equal to one micron; for example less than or equal to 500 nanometers (nm), or even less than or equal to 150 nm.
• the liquid binder precursor may be an aqueous sol including a ceramic precursor for alumina and/or zirconia.
• aqueous boehmite sols and zirconia sols examples include aqueous boehmite sols and zirconia sols.
• the liquid binder precursor may have the same or different composition as the abrasive particles. Details concerning zirconia sols can be found, for example, in U. S. Pat. No. 6,376,590 (Kolb et al.). Details concerning boehmite sols can be found, for example, in U.S. Pat. Nos.
• the jetted liquid binder precursor material is converted into a binder material that bonds together the loose powder particles in predetermined regions of the loose powder particles to form a layer of bonded powder particles; for example, by evaporation of a liquid vehicle in the liquid binder precursor material.
• heating the binder material to sufficiently high temperature causes it to volatilize and/or decompose (e.g., "bum out") during a subsequent firing step. Cooling may be accomplished by any means known to the art (e.g., cold quenching or air cooling to room temperature).
• the jetted liquid binder precursor material is converted into a binder material that bonds together the loose powder particles in at least one predetermined region of the loose powder particles to form a layer of bonded powder particles; for example, by evaporation of a liquid vehicle in the liquid binder precursor material.
• heating the binder material to sufficiently high temperature causes it to volatilize and/or decompose (e.g., "bum out") during subsequent sintering or infusion steps.
• the above steps, of laying down a powder layer and jetting a temporary binder material are then repeated with changes to the region where jetting is carried out according to a predetermined design resulting through repetition, layer on layer, in a three-dimensional (3-D) abrasive article preform.
• the loose powder particles and the liquid binder precursor material may be independently selected; that is, either or both or the loose powder particles and the liquid binder precursor material may be the same as, or different from those in adjacent deposited layers.
• the abrasive article preform comprises the bonded powder particles and remaining loose powder particles. Once sufficient repetitions have been carried out to form the abrasive article preform, it is preferably separated from substantially all (e.g., at least 85 percent, at least 90 percent, preferably at least 95 percent, and more preferably at least 99 percent) of the remaining loose powder particles, although this is not a requirement.
• multiple particle reservoirs each containing a different powder may be used.
• multiple different liquid binder precursor materials may be used, either through a common printhead or, preferably, through separate printheads. This results in different powders/binders distributed in different and discrete regions of the bonded abrasive article.
• relatively inexpensive, but lower performing abrasive particles and or vitreous bond precursor particles may be relegated to regions of the bonded abrasive article where it is not particularly important to have high performance properties (e.g., in the interior away from the abrading surface).
• bonded abrasive articles made in such ways have considerable porosity throughout their volumes. Accordingly, the abrasive article preform may then be infused with a solution or dispersion of additional bond precursor material, or pore growth modifiers.
• Powder bed jetting equipment suitable for practicing the present disclosure is commercially available, for example, from ExOne, North Huntington, Pennsylvania. Further details concerning powder bed jetting techniques suitable for practicing the present disclosure can be found, for example, in U.S. Pat. Nos. 5,340,656 (Sachs et al.) and 6,403,002 Bl (van der Geest).
• abrasive articles made according to embodiments described herein are configured to receive a coolant fluid from an external source and provide the coolant to an active grinding area.
• Abrasive articles described herein have an internal reservoir that receives coolant from an external source. Within the internal reservoir is a feature that changes a property of the coolant. For example, the coolant pressure and / or flow speed may increase. The coolant is then delivered to an active grinding area, for example through one or more openings extending through a grinding layer of the abrasive article. Additionally, one or more fluid channels may be present along the surface of the grinding area. Using abrasive articles with such systems may reduce or even prevent surface burning and / or damage to a workpiece subsurface during an abrading operation.
• a grinding system includes a grinding wheel with a coolant channel coupled to a coolant exit.
• the coolant channel extends through a grinding layer of the grinding wheel.
• the coolant exit is on an active grinding surface of the grinding wheel.
• the system also includes a mounting feature configured to couple the grinding wheel to a grinding machine.
• the system also includes a coolant distribution component configured to receive coolant and provide it through the coolant channel to the coolant exit point.
• the grinding system may be implemented such that the grinding wheel is a single rib gear grinding wheel, a threaded gear grinding wheel, a bevel gear grinding wheel, an ID grinding wheel, an OD grinding wheel, a Cam/Crank grinding wheel, a centerless grinding wheel, a face grinding wheel, a double face grinding wheel, a cup wheel, ball grinding wheel, a surface grinding wheel, a surface grinding cup, a flute grinding wheel, a pencil edge grinding wheel, or a straight or angular plunge grinding wheel.
• the grinding wheel is a single rib gear grinding wheel, a threaded gear grinding wheel, a bevel gear grinding wheel, an ID grinding wheel, an OD grinding wheel, a Cam/Crank grinding wheel, a centerless grinding wheel, a face grinding wheel, a double face grinding wheel, a cup wheel, ball grinding wheel, a surface grinding wheel, a surface grinding cup, a flute grinding wheel, a pencil edge grinding wheel, or a straight or angular plunge grinding wheel.
• the grinding system may be implemented such that the grinding wheel includes a resin-bond, vitreous-bond or metal-bond.
• the grinding system may be implemented such that the grinding wheel includes shaped abrasive particles.
• the grinding system may be implemented such that the grinding wheel is a product of an additive manufacturing process.
• the grinding system may be implemented such that the coolant channel is an arcuate or tortuous coolant channel.
• the grinding system may be implemented such that the mounting feature is integral to the coolant distribution component.
• the grinding system may be implemented such that the mounting feature includes an internal bore that receives a spindle of the grinding machine.
• the grinding system may be implemented such that the spindle provides the coolant.
• the grinding system may be implemented such that the coolant distribution component is mechanically coupled to the mounting feature, such that the coolant distribution component and the mounting plate remain stationary with respect to the grinding wheel during a grinding operation.
• the grinding system may be implemented such that the coolant distribution component includes a nozzle receiving feature.
• the grinding system also includes a nozzle received by the nozzle receiving featureThe nozzle provides the received coolant.
• the grinding system may be implemented such that the nozzle receiving feature has an asymmetric opening.
• the grinding system may be implemented such that the coolant distribution component includes a plurality of reservoirs, each configured to receive coolant and provide it to one of a plurality of coolant channels.
• the grinding system may be implemented such that the coolant distribution component includes an internal space defined by an inner edge with an inner radius and an outer edge with an outer radius.
• the coolant distribution component includes a plurality of blades coupled to the inner edge. Each of the plurality of blades extends toward the outer edge.
• the grinding system may be implemented such that the blades are curved.
• the grinding system may be implemented such that the curved blades are all curved in the same direction.
• the grinding system may be implemented such that each of the plurality of blades connect to both the inner and outer edge.
• the grinding system may be implemented such that the grinding system includes a plurality of coolant channels such that the number of coolant channels is at least as many as a number of blades.
• the grinding system may be implemented such that the plurality of blades are positioned such one of the plurality of coolant channels is positioned between adjoining blades.
• the system may be implemented such that the coolant exit is radially separate from a coolant entry of a coolant channel connecting the coolant exit and coolant entry.
• the system may be implemented such that the mounting feature is a mounting plate or a mounting flange.
• a coolant distribution component for an abrading system includes a mounting component configured to couple the coolant distribution component to a grinding machine.
• the component also includes a shaped coolant reservoir configured to receive coolant from a source other than the coolant distribution component.
• the component also includes a coolant distribution component configured to provide the coolant to an interior of an abrasive article.
• the coolant distribution component may be implemented such that the mounting component is a complementary feature that couples to a feature of a mounting plate of a grinding machine.
• the coolant distribution component may be implemented such that the complementary feature is a receiving component that receives a fastener.
• the coolant distribution component may be implemented such that the fastener extends through both the mounting plate and the coolant distribution component.
• the coolant distribution component may be implemented such that it includes a bore configured to receive a spindle of the grinding machine.
• the mounting component couples the coolant distribution component to the spindle.
• the coolant distribution component may be implemented such that the spindle provides the coolant into the shaped coolant reservoir.
• the coolant distribution component may be implemented such that the coolant is received from a nozzle.
• the coolant distribution component may be implemented such that it includes a nozzle receiving feature that has a complementary shape to the nozzle opening.
• the coolant distribution component may be implemented such that the shaped coolant reservoir has a plurality of chambers, and wherein each chamber has a separate coolant distribution point.
• the coolant distribution component may be implemented such that the coolant distribution point includes an aperture configured to align with an internal channel of an abrasive article.
• the coolant distribution component may be implemented such that each chamber is shaped to induce turbulent coolant flow.
• the coolant distribution component may be implemented such that the shaped coolant reservoir includes a plurality of blades extending from an interior edge toward an exterior edge.
• the coolant distribution component may be implemented such that the plurality of blades are curved.
• the coolant distribution component may be implemented such that the mounting component is a mounting plate or a mounting flange.
• a method of providing coolant to an active grinding surface includes receiving coolant from a coolant source. The method also includes directing the coolant through a bonded abrasive article to the active grinding surface. The coolant is provided through the bonded abrasive article in a turbulent flow. The method may be implemented such that directing the coolant through a bonded abrasive article includes collecting the received coolant in a coolant reservoir and directing the received coolant to an internal channel of the bonded abrasive article.
• the method may be implemented such that the reservoir includes a curved edge.
• the method may be implemented such that the internal channel is an arcuate or tortuous channel extending through the bonded abrasive article.
• the method may be implemented such that the internal channel extends to an exit point on the active grinding surface.
• the method may be implemented such that the exit point is at least 45° away from an entry point of the internal channel with respect to a radial axis extending through a center of the bonded abrasive article.
• the radial axis is parallel to the active grinding surface.
• the method may be implemented such that the exit point is at least 90° away from the entry point.
• the method may be implemented such that the coolant reservoir includes a material free of abrasive particles.
• the method may be implemented such that the coolant reservoir is a non-ceramic material.
• the method may be implemented such that the coolant is received from a nozzle.
• the method may be implemented such that the nozzle provides coolant directly into a nozzle receiving feature.
• the method may be implemented such that the coolant is received from a spindle of a grinding machine.
• the method may be implemented such that the reservoir includes a plurality of internal features, each extending outward from an internal bore.
• the method may be implemented such that each of the plurality of features extend from the internal bore to an edge of the reservoir, such that a plurality of chambers are separated within the reservoir from each other.
• the prepared mixture was placed in the hopper of the ExOne Innovent lab printer.
• a 3D model was prepared into an STL file to make a rotating grinding wheel having features as illustrated in FIGS. 7A-7D. Holes and channels were created to reach the most difficult areas to be touched/reached by the coolant during the grinding process, for example the deeper area of the gear. 8 rectangular holes and channels having a size of 2mm x 3mm with a helicoidal shape of 10° were designed to drive the coolant out of the wheel.
• the file was created into Solidworks CAD system and saved as an STL file which is readable by the Exone Innovent lab printer.
• the file was transferred into a print job for the ExOne Innovent lab printer. Printing was made of successive steps to spread powder layers, to jet binder in 2D patterns made from cross sections of the 3D objects and to at least partially dry that binder between jetting and spreading steps.
• the most commonly used parameters were: Recoat speed (mm/s) : 25 - Oscillator speed (rpm) : 2800 - Roller Speed (rpm) : 200 - Roller Traverse speed (mm/s) : 15.
• This print job was run and completed on the printer, and the result was a powder bed holding loose powder and 3D shapes of binder and powder. That powder bed was removed from the printer and baked in an oven at 195°C for 6 hours. After cooling, those 3D shapes or “green” parts were extracted and de-powdered. Those de-powdered parts were placed into a furnace for burning out the binder and then melting and sintering the vitreous based frit which bonded the PSG grits into a solid matrix.

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• 2021
  • 2021-10-25 WO PCT/IB2021/059837 patent/WO2022090904A1/en active Application Filing
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