GB2582771A - A super-abrasive grinding wheel and a method of optimising operation of a super-abrasive grinding wheel - Google Patents
A super-abrasive grinding wheel and a method of optimising operation of a super-abrasive grinding wheel Download PDFInfo
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
- B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
- B24D3/34—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties
- B24D3/342—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties incorporated in the bonding agent
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
- B24D18/00—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for
Abstract
A super abrasive grinding wheel has a core with a surface layer of super abrasive grains, each grain having an aspect ratio, AR, between 1.0 and 2.0, but preferably between 1.29 and 1.86. The super abrasive grains may comprise diamond or cubic boron nitride and preferably have a toughness index (TI) around 60%. The grinding wheel has a grit performance index, M, equal to 100AR/af where af is the wheel to workpiece contact area. The effect of AR on the power required during machining is shown in fig.9 where a higher AR results in a more efficient grind.
Description
A SUPER-ABRASIVE GRINDING WHEEL AND A METHOD OF OPTIMISING OPERATION OF A SUPER-ABRASIVE GRINDING WHEEL
FIELD OF THE INVENTION
This disclosure relates to a super-abrasive grinding wheel and a method of optimising operation of the super-abrasive grinding wheel.
BACKGROUND ART
Grinding is an important abrasive machining process at the end of many manufacturing chains. Its chip forming capability is used either to produce a suitably smooth surface or to grind materials that are too hard for other conventional machining methods. Grinding wheels are a common tool used in the grinding process, which is defined by the interaction between the cutting tool and the workpiece.
Grinding wheels are conventionally comprised of a core, with a layer of abrasive material on a surface of the core in a bond with abrasive material (grit) uniformly distributed through its volume. Grits are responsible for cutting away workpiece material while the bond provides the necessary support to retain the grits during their cutting operation. Wheels are normally distinguished by their abrasive material, e.g., conventional (aluminium oxide or silicon carbide) and super-abrasive (cubic boron nitride (CBN) or diamond). Additionally, they are classified with respect to their bonding system, which can be vitrified, resin, metal and electroplated. In industrial grinding, the most favourable bond used is vitrified due to its self-sharpening and dressing abilities. This advantage is a consequence of superior mechanical properties of the bonding system, abrasive material and porosity [1].
A number of different factors affect the performance of vitrified grinding wheels. They have roughly been divided into two groups: (i) operating conditions/system and (ii) wheel design.
The first group involves type of grinding operation, grinding parameters, conditioning/dressing, coolant system and machine dynamics. The second group is focused on the geometrical (macro) and structural (micro) properties of the grinding wheel.
The grinding response encapsulates all physical processes acting at the wheel-workpiece interface, as a consequence, relationships involving grinding parameters have been the subject of intense research since the 1950s [2-8]. The effect of dressing parameters [1,9-14], specific application [15,16], coolant system/design [17-19] and machine dynamics [20] on the grinding performance have been extensively investigated. Although these investigations have contributed to improvements in the overall grinding practice, the wheel design has the first-order effect on the grinding performance.
In spite of the fact that a grinding wheel can have many macro geometries, its shape is generally constrained by components size and attributes. Thus, the most common control variable is the wheel microstructure, i.e. porosity, bonding system and abrasive material (see Figure 1). Porosity is one of the most important properties of a vitrified grinding wheel. The pores support the supply of coolant into the grinding zone, facilitate the removal of chips and residues, reduce likelihood of thermal degradation or damage and allow better dressing ability [1,8]. Despite the wide variety of bond types and strengths, no one type of bond is considered the best. Instead, the best bond is the one which offers the right benefits for a particular application and is simultaneously optimized for the abrasive material used [21-23].
It is well known that CBN grits possess superior wear resistance, mechanical and physical properties. It has great hardness and resistance to plastic deformation, high thermal conductivity and is chemically inert. This makes CBN grits ideal in applications with harsh environment conditions, particularly, those encountered in steel grinding application. Although grits are the element responsible for cutting, only a limited number of studies investigated the effects of grit properties on wheel performance. Traditionally, there is strong correlation between the grit strength, which is dictated by the grit structure morphology and chemistry, and the wheel wear [7,24,25]. To the best knowledge of the inventors, an investigation focused on the effect of CBN grit shape on the performance of vitrified grinding wheels has not been performed to-date.
In this patent application, the effect of the vitrified wheel microstructure, more precisely CBN grits shape, is investigated through a series of grinding tests conducted in a low alloy chrome steel 100Cr6 with a creep-feed grinding machine. The reason for choosing 100Cr6, also known as bearing steel, is its application range and the possibility of achieving hardness in access of 60 HRC. The tool performance and wear are evaluated using a simple interface model proposed by Malkin and Cook [5] and Detoumay and Defourny [26]. A real world application is then proposed.
SUMMARY OF THE INVENTION
In a first aspect of the invention, there is provided a method of optimising operation of a super-abrasive grinding wheel, said super-abrasive grinding wheel comprising a core, a super-abrasive grain layer provided on a surface of the core, the super-abrasive grain layer comprising a plurality of super-abrasive grains, each grain having a specific aspect ratio (AR), said super-abrasive grinding wheel having a wheel-to-workpiece contact area (ar), said method comprising: - providing a first super-abrasive grinding wheel having a first grit performance index Mi of 100ARilam -removing said first super-abrasive grinding wheel - providing a second super-abrasive grinding wheel having a second grit performance index M2 of 100AR2/af2, - M, being different to Mi.
Preferable and/or optional features of the first aspect of the invention are provided in dependent claims 2 to 9.
In a second aspect of the invention, there is provided a super-abrasive grinding wheel comprising a core, a super-abrasive grain layer provided on a surface of the core, the super-abrasive grain layer comprising a plurality of super-abrasive grains, each super-abrasive grain having an aspect ratio (AR) of between 1.0 and 2.0. Preferably the aspect ratio is between 1.2 and 2.0, and more preferably between 1.29 and 1.86.
Preferable and/or optional features of the second aspect of the invention are provided in dependent claims 11 to 19.
BRIEF DESCIPTION OF THE DRAWINGS
Non-limiting example arrangements to illustrate the present disclosure are described with reference to the accompanying drawings, in which: Figure 1 shows the structure and composition of vitrified bond grinding wheel; Figure 2 shows the interaction between the workpiece, grit and bond; Figure 3 shows (a) tte -Q' correlation between input and output of grinding process and (b) ue -se correlation between two grinding outputs [26]; Figure 4 shows the correlation between AR and TI (%) for the six investigated grits; Figure 5 shows grit with (a) lowest AR and (b) highest AR; Figure 6 indicates the grinding set-up; Figure 7 shows (a) force generation immediately after dressing and (b) stabilised forces; Figure 8 shows changes of (a) P4-and (b) Pk when increasing Q' for Grit D; Figure 9 shows the correlation between grits AR and Pi; Figure 10 shows the estimated of for (a) Grit A and (b) Grit F; Figure 11 shows the difference in contact are of for Grit A, B, E and F; Figure 12 shows ue -se graph for the six evaluated grit types; Figure 13 shows two graphs for Grit A and F in (a) tie -Q' and (b) ue -hin spaces; Figure 14 shows (a) Pa', Pt' and (b) 1.4" -s, generated during micro wear test for grit A. vs=40m/s, vw=24000mm/min and cte=0.033mm.
Figure 15 shows the correlation between WI' and AR for vs=40m/s, 12w-24000mm/1n n ae=0.033mm and Q1-13.2mm3/mms; Figure 16 shows the correlation between I/177.N and AR/Ptri for 12,=40m/s,12,-24000mm/min 5 ae=0.033mm and (21=13.2mm3/mms, and Figure 17 shows the correlation between W7 and M.
DETAILED DESCRIPTION
Variables It is commonly accepted in the literature [3,5,26-28] that the energy in grinding is dissipated into three independent mechanisms that are taking place at the wheel-workpiece interface: (i) pure cutting or shearing, (ii) ploughing or plastic displacement and (iii) frictional, sliding or rubbing contact along the grit and bond wear flats, see Figure 2. However, it is commonly acceptable that the ploughing component is considerable less when all active grains are engaged with the workpiece and generating chipping [4,29,30].
The tool force F acting on the wheel can thus be decomposed into two components [5]: F=F+Ff (1) where F (N) is the cutting or shearing component and F1 (N) the friction or rubbing component mobilized at both contact areas: grits wear flat and bond bearing surface.
The normal F" and the tangential Ft components can be expressed as: = Fcn + F1,1 (2) Ft = Ft + Ft The cutting process is often described as either a ductile chip-forming process (plastic failure) or a brittle process (propagation of fractures). Models normally used, implicitly consider that a ductile regime is dominant and the magnitude of the cutting force is proportional to the cross-sectional cutting area a, (mm2). It is important to mention here that even brittle materials can be machined in a ductile mode, depending on process design and operating conditions imposed [31].
The cutting component F in ductile grinding can be written as [26,28]: = fiCa, (3) Ft, = tea, where u, (J/mm)) represents the intrinsic cutting specific grinding energy and. corresponds to the inclination of the cutting force or the ratio Fn /Ft [26]. The adjective "intrinsic" is used to emphasize that a,* corresponds to the lowest energy required to remove a unit volume of workpiece. Typically, it represents the response of a perfectly sharp wheel at maximum imposed material removal rate [29]. By the conservation of volume in plasticity, the cross sectional cutting area a, can be expressed as [32]: a, = aewm," / vs (4) where a, (mm) is the depth of cut, w (mm) is the wheel width, v," (mm/min) is the workpiece speed and vs (m/s) is the wheel speed.
Assuming that the friction or the rubbing process is constrained by a frictional relation, Fit = pFT, a following equation can be derived by combining Fn and Ft: Ft = 14aewliwivs(1-12) + PFn (5) where it is the friction coefficient at the wheel-workpiece interface.
It is convenient for the purpose of the analysis to define new set of variables, Pt' = Ftvs/w, Pv= = Env, / w and pp = rinvs/w (6) where Pt' is the total specific power, PI is the specific threshold power, Pru is the total specific normal work and Pr is the specific normal threshold work.
Combining Eqs. (2), (3) and (6) yields: = rn.J2' + (7) where Q' = czevu" (mm3/mms) is the specific material removal rate. It is important to stress that Eq. (7) is only valid in the cutting regime, when Q' > Q. ,". In the case of Q' < Q"' i", the response is dominated by rubbing and ploughing and, consequently, there is a nonlinear relationship between Pt' and Q' [28]. In the event of Q' > Q,' ax, the grinding response is in the brittle regime and a different model is needed for the cutting force.
After scaling Eq. (7) by Q', the specific grinding energy ue = /Q' can thus be described as: = + PF/Q'e (8) The tie -Q' diagram has been widely used by the grinding industry to evaluate grinding performance. Using the new variables, Eq. (5) can be rewritten as: Pt' = ueQ'(1-ptO + yen' (9) Scaling Eq. (9) also by Q' additional representation of ue can be obtained: ue = 24(1 -ite) + mse (10) where se = P"' /Q' is called the cutting strength [26].
A conceptual sketch of ue -Q' and tie -se diagrams are shown in Figure 3. If the grinding response corresponds to an ideal condition or maximum efficiency then v., = ue and se = On the other hand, if an increase of overall rubbing or contact between the wheel and the workpiece takes place, the points will move away from the ideal point and the grinding efficiency (n) will decrease, = uVue (11) Notice that both diagrams can estimate tie, however, the ue -se space, which combines two outputs (F" and Ft), provides additional information regarding frictional or rubbing contact it and the inclination of the cutting force C. Maximum Undeformed Chip Thickness ft, The maximum undeformed chip thickness h", is a key variable often used to evaluate grinding processes and, consequently, the estimation of kin is considered critical for performance evaluation. The maximum undeformed chip thickness lint is commonly expressed as [29]: relvwcte\1/2 hin Vrvsl, (12) where Cis a number of active grits per unit of wheel surface, r is the chip width-to-thickness ratio and lc = (Cied,31/2 is the wheel-workpiece contact length, while deq is the equivalent wheel diameter [29]. Although frequently used, hm is governed by many factors and its experimental determination is ambiguous and time consuming. Additionally, lint can remain constant with a significant variation of the operating conditions (A", vs, cle) and wheel design (deq, C and r). Thus, a more practical way to evaluate the effect of the grit shape is to eliminate C and r from the formulation, assuming that they remain constant regardless of the operating conditions and deg used. In this case, any variation of the grinding response in the 131' -Q', ue -Q' and u, -se diagrams corresponds to the effect of the wheel microstructure.
cBN grit and wheel The first CBN grit was synthesized in 1957 by Wentorf [33], using boron and boron nitride at high temperatures and pressures in the presence of a catalyst. CBN grits have excellent properties such as high hardness, toughness, thermal conductivity and chemical stability; and are particularly suitable for machining ferrous materials.
The main measurable property commonly accepted for the grinding community to differentiate abrasives is the impact strength value or Toughness Index (TI) from the Friability Impact (FI) tester [34]. The purpose of measuring TI originates from diamond due to the necessity for monitoring the quality (or strength) of synthesized products. Recently, FI has been used to differentiate CBN products as well as to help determine the most suitable super-abrasive product for a particular application. This is the case of Element SixTM ABN800 (high TI) and ABN200 (low TI) products, which are typically used for crankshaft and double-disc grinding, respectively.
Another important property of grits is their shape or morphology. The geometrical features of CBN are normally descriptive rather than quantitatively evaluated. Blocky, elongated or irregular are common metrics used by grit manufacturers. However, a typical grit attribute used to quantify shape is Aspect Ratio (AR), which is an image projection attribute that describes the proportional relationship between the width of an image and its height. Although there are some challenges to estimate AR of small grits, several commercial devices have been used to automatically process grits AR. In this investigation, the Camsizer XT is used to estimate the CBN grit shape.
Six grit types in ANSI US mesh 120/140 (average grain size = 126p.m) with AR in the range [1.29-1.86] are investigated here. Three grits (Grit A, Grit D and Grit F) were produced with the same chemistry and synthesis process. The grits B, C and E, on the other hand, have not only different shapes, but also different synthesis processes. The difference in TI between grits is less than 10%, which is within a typical specification for super-abrasives. It is worth mentioning that, particularly for CBN, shape and toughness are not necessarily dependent properties.
Figure 4 illustrates the shape (AR) and the strength (TI) of all CBN grits considered here. Notice that grits C, D and E have very similar attributes and grits A and F are the most different in terms of AR (see Figure 5) Vitrified bond wheels are normally designed to hold the grit through different grinding conditions and at the same time have the self-sharpening ability, which helps generate lower grinding forces. In this analysis, all wheels have the same bond properties and grits concentration, C150 (6.6 ct/cm3).
Methodology The grinding experiments were carried out at the Element SixTM Global Innovation Centre in the UK with a creep-feed grinding machine (Blohm MT408). A sketch of the experimental setup is shown in Figure 6. The sensor utilized to measure the two components of the force was a Kistler dynamometer (Type 9257A). The workpiece material used in all tests was 100Cr6 with hardness of 60-61HRC and dressing parameters were kept constant: Ud=4, ad=0.003mm and q=0.81, where Ud is the dressing overlap ratio, ad ("um) the dressing depth and q the speed ratio between the dressing and grinding wheel.
The methodology used consisted of two types of test: (i) 'window of operation' and (ii) 'micro 15 wear'.
The 'window of operation' test evaluates the grinding efficiency over a wide range of Q' by changing both, feed rate (vv) and depth of cut (ae). After the wheel was dressed a number of passes were run through the workpiece in order to eliminate the effect of dressing on the grinding response, as shown in Figure 7 [29]. Once the wheel topology was stabilised, only two passes for each Q' were conducted in order to avoid wheel wear. The coolant utilized in the window of operation test was Hocut 768 (with 4.5-5% concentration) applied through high pressure cleaning nozzle using 50 bar and the lower pressure nozzle, 9 bar, pointing between the wheel and the workpiece.
The 'micro wear' test measures the wear of the wheel after a specified amount of workpiece material was removed or ground. The term 'micro' wear refers to wear on the grain level [35]. In this test, a constant Q'=13.2mm3/mms was used, the forces were monitored in situ and the wheel wear was measured at the end. The wear was estimated by measuring the step height between used and unused part of the wheel (only half of the wheel was used during the test). The step was ground into a soft graphite block. Here, the coolant used was Quaker 370 KLG (with 5-5.5% concentration) with the same nozzle configuration of the window of operation test.
Window of Operation Test Results A known phenomenon in grinding is a proportional increase of Pt' with Q' as displayed in Figure 8 (a) [3]. The two relevant parameters that can be obtained from the P' -Q' space are PI and 24. Figure 8 (b) shows similar correlation but now in the Pt' -Q' diagram. An important parameter that can be extracted here is e.
The summary of the three parameters for six tested grit types can be seen in Table 1.
Grit type 1.4 [i/mm3] Ptr[Wirrim] p f Grit A 49 77 2.76 0.15 Grit B 49 68 2.61 0.13 Grit C 46 61 2.59 0.16 Grit D 48 55 2.71 0.12 Grit E 45 50 2.64 0.13 Grit F 46 19 2.28 0.12 Table I: mc, Pt' 1, and it for the six tested grit types.
The linear relationship between Pt' and Q' indicates that u; (see Figure 8 (a)) is constant and thus independent of Q' in the ductile grinding regime. Similar observation is presented by Pecherer and Malkin [3]. Comparison of u; for different grain types suggests that uL also does not change significantly with the grit shape (see Table 1). However, previous research suggests that tt; can be altered by changing the workpiece [3], dressing parameters [36] or exposure of grits [28].
Figure 8 (b) is showing a constant ratio between Pry and Q'. This phenomenon indicates that the cutting force inclination e stays constant regardless of Q' imposed. Similar to u; , e is unaffected by the grits shape. The reason for this could be stochastically distributed grains, which minimise the effect of properties of individual particles.
The main differentiator between the grits in this study is shape (AR). The correlation between PI and AR has been established as illustrated in Figure 9. The results are trending towards linear relationship. Based on Pt -AR plot, it is suggested that overall contact area between the wheel and workpiece is affected by CBN grit shape. The more elongated the grit (higher AR), the sharper the wheel (less flat area) and vice-versa. Additionally, the higher the grit AR, the less power is required to grind due to more efficient cutting with less rubbing and ploughing. It is important to stress here again that all wheels have the same diameter, grain size, concentration, porosity and bond.
To confirm the difference in the wheel-workpiece contact area af, image analysis is conducted with wheel containing Grit A, B, E and F. 3D images are taken with Keyence VH500 at the end of the window of operation test at 200x magnification. They are then overlaid with height map, where dark red colour identifies the highest points and dark blue the lowest. The amount of the highest area is evaluated with ImageJ software as illustrated in Figure 10 for Grit A and F. The ratio between the highest area and the total measured area is expressed as percent of contact area (al). The difference in of (%) for the four evaluated grit types is shown in Figure 11.
The evaluated of differences displayed in Figure 11 confirm that the grit with higher AR has less wheel-workpiece contact, which was previously observed in the PI -AR space (Figure 9). Increased contact area can generate more heat during the grinding process resulting in thermal damage, but can also provide superior surface finish on the workpiece. On the other hand, reducing the contact area, the thermal damage can be minimised, but then surface finish can be compromised.
A correlation between specific grinding energy and cutting strength [26] is shown in Figure 12. ue -se diagram provides invaluable information regarding the mechanics of the wheel-workpiece interface, it and It also reveals how quickly a particular wheel reaches the ue.
Based on the Ft results summarised in Table 1, we can observe that the frictional contact between the wheel and the workpiece is unaffected by the different grit types and the wheelworkpiece contact area. The values obtained are between 0.11 and 0.16, which is very close to friction coefficient between diamond and metal [37]. According to Malkin and Guo [29], a drastic change in it can be expected when thermal damage occurs at the grinding interface. Additional important observation can be made from the shift of points with increase of Q' towards We., where they eventually cluster.
By plotting the results of Grit A and Grit F in the ue -Q' space (see Figure 13 (a)), it is easier to establish the Q' at which particular grit type reaches t4. We can observe that grit A has to be subjected to higher Q' in order to achieve i4. This suggests that Grit F is more efficient at lower Q' while Grit A has to be subjected to higher Q' in order to achieve similar grinding efficiency. By plotting the same results in the ue -it, space highlights that ite* is achieved at similar hm, assuming that C=15, deq=300mm, r=15 for Grit A and r=6.1 for Grit F [30,38].
These results suggest that for the same Q' the wheel with Grit F generates, on average, higher hm when compared to Grit A. Micro Wear Test Results Under a certain Q'employed, the grinding response is characterised by a minimum variation of Pru and Pt' after a period of stabilisation (see Figure 14 (a)). The stabilisation (highlighted in red) is a known phenomenon in CBN vitrified wheels [3]. Notice that the forces are high immediately after dressing and decrease significantly in a short period of time or volume ground until reaching the steady state response or the self-sharpening regime. The corresponding data points of Figure 14 (a), but in the tie -se diagram, are illustrated in Figure 14 (b). The same observation of Figure 14 (a) applies here; however, information regarding the frictional contact can be estimated with this diagram. The value for p appears to be significantly higher than the one found in the window of operation test (a 0.4), suggesting that the stabilisation period is dominated by a severe contact between fractured grits and the workpiece (3-body abrasion). The dressing process plays a critical role in ensuring that acceptable wheel form and topography are achieved prior to grinding. Nonetheless, it causes greater fracture of the abrasive grits, depending on the dressing parameters.
The maximum observed wheel wear for four different grits is shown in Figure 15. The 25 normalised radial wheel wear W,P1 is defined as W" = wri/wrmax(o4), where 144! is radial wheel wear for particular wheel and W"'" the maxmum wheel wear within the tested group. This result indicates that material with lower (higher) AR is more (less) wear resistant. Considering that Pi decreases by increasing AR (see Figure 5), the only way to isolate the effect of the grit shape on the wheel wear is scaling by PI, see Figure 16.
Here, we can notice a nonlinear relationship between observed wear and the AR/PT/ ratio. Taking into account that Pt'l ix at, a new grit performance index, 3W, is proposed: = 100AR/al (11) This variable describes the relationship between the two wheel design, grit shape (AR) and wheel-workpiece contact area (a1). Thus, the wheel wear can be controlled by changing not only the grit strength, size and concentration, but also the shape. The relationship between W7 and M is shown in Figure 17. In this case, the results can be approximated by a straight line, indicating that there is a linear relation between WP and.7/C for the wheels investigated here.
Based on the grinding parameters and workpiece material used in this study, it can be expected that a 20% reduction in wheel wear can be achieved by reducing M by 20.
Considering that the specific grinding energy it, is also affected by grit shape (and consequently by NC), this finding can help to design a wheel that would reduce the amount of heat generated by the grinding process and, consequently, grinding temperatures.
Conclusions
The effects of the CBN grit shape on the performance of vitrified-bonded grinding wheel are evaluated by a series of tailored experiments. At first, a novel methodology to investigate grinding wheels is introduced and quantitative information from the grinding response related to the wheel performance, grinding efficiency and wear are obtained. The results from two different experimental set-ups lead to several observations: (i) the intrinsic specific grinding energy ue*, coefficient of friction it and the inclination of the cutting force are unaffected by the CBN grit shape, suggesting that these parameters are mainly controlled by the workpiece material, dressing parameters and grit protrusion; (ii) the specific grinding energy it, is affected by the CBN grit shape, depending on the Q' used; (iii) the overall contact surface at the interface or the grit wear flat area al. and, consequently, the specific threshold power P7 increases with the grit aspect ratio AR, i.e., elongated or sharper grits generates less 131(ar), (iv) the wheel wear is proportional to M = 100AR /at, called the grit performance index, that corresponds to the relationship between two wheel design parameters and (v) grit shape (AR) affects the undeformed chip thickness hin through parameter r, which fundamentally affects the grinding performance.
Although the results were obtained on a limited series of tests, they are encouraging in regard to the potential use of this methodology to investigate the effect of grits on the grinding response.
While this invention has been particularly shown and described with reference to certain embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as defined by the appended claims.
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Claims (19)
- CLAIMS1 A method of optimising operation of a super-abrasive grinding wheel, said super-abrasive grinding wheel comprising a core, a super-abrasive grain layer provided on a surface of the core, the super-abrasive grain layer comprising a plurality of super-abrasive grains, each grain having an aspect ratio (AR), said super-abrasive grinding wheel having a wheel-to-workpiece contact area (ar), said method comprising: - providing a first super-abrasive grinding wheel having a first grit performance index Mi of I 00ARilam - removing said first super-abrasive grinding wheel - providing a second super-abrasive grinding wheel having a second grit performance index M2 of 1 00AR2/af2, - M2 being different to Mi.
- 2. A method of optimising operation of a super-abrasive grinding wheel as claimed in claim 1, wherein M2 is more than NIL
- 3. A method of optimising operation of a super-abrasive grinding wheel as claimed in claim 3, wherein the step of providing M2 comprises using super-abrasive grains with an increased aspect ratio AR.
- 4. A method of optimising operation of a super-abrasive grinding wheel as claimed in claim 3, wherein the step of providing ratio M., comprises using a super-abrasive grinding wheel with a decreased wheel-to-workpiece contact area an.
- 5. A method of optimising operation of a super-abrasive grinding wheel as claimed in claim 4, wherein the step of using a super-abrasive grinding wheel with a decreased wheel-to-workpiece contact area an comprises using a plurality of super-abrasive grains with a decreased grain size and, optionally, additionally increasing the quantity of super-abrasive grains.
- 6. A method of optimising operation of a super-abrasive grinding wheel as claimed in claim 4 or 5, wherein the step of using a super-abrasive grinding wheel with a decreased 19 wheel-to-workpiece contact area an comprises using a reduced concentration of super-abrasive grains in the super-abrasive grain layer.
- 7. A method of optimising operation of a super-abrasive grinding wheel as claimed in claim 4, 5 or 6, wherein the step of using a super-abrasive grinding wheel with a decreased wheel-to-workpiece contact area an comprises using an increased porosity in the super-abrasive grain layer.
- 8 A method of optimising operation of a super-abrasive grinding wheel as claimed in claim 1, wherein M2 is less than Mi.
- 9. A method of optimising operation of a super-abrasive grinding wheel as claimed in any one of the preceding claims, wherein the aspect ratio AR of M2 is between 1.29 and 1.86.
- 10. A super-abrasive grinding wheel comprising: a core, a super-abrasive grain layer provided on a surface of the core, the super-abrasive grain layer comprising a plurality of super-abrasive grains, each super-abrasive grain having an aspect ratio of between 1.0 and 2.0, preferably between 1.2 and 2.0, and more preferably between 1.29 and 1.86.
- 11. A super-abrasive grinding wheel as claimed in claim 10, wherein the super-abrasive grains comprise diamond.
- 12. A super-abrasive grinding wheel as claimed in claim 10 or 11, wherein the super-abrasive grains comprise cubic boron nitride (cBN).
- 13. A super-abrasive grinding wheel as claimed in any one of claims 10, 11 or 12, wherein the super-abrasive grains have a toughness index of between 10 % and 90 %.
- 14. A super-abrasive grinding wheel as claimed in 13, wherein the super-abrasive grains have a toughness index of between 55 % and 65 %.
- 15. A super-abrasive grinding wheel as claimed in claim 14, wherein the super-abrasive grains have a toughness index of 60 %.
- 16. A super-abrasive grinding wheel as claimed in 13, 14 or 15, wherein when comparing Mi and M2 the variation of toughness is between 0.1 % and 10 %.
- 17. A super-abrasive grinding wheel as claimed in any one of claims 10 to 16, wherein the super-abrasive grain size is between ANSI US mesh 60/80 and US mesh 325/400 inclusive.
- 18. A super-abrasive grinding wheel as claimed in claim 17, wherein the super-abrasive grain size is ANSI US mesh 120/140.
- 19. A super-abrasive grinding wheel as claimed in any one of claims 10 to 18, wherein the super-abrasive grain layer comprises a vitrified bonding agent to bond the plurality of super-abrasive grains to the core.
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|---|---|---|---|---|
| JPH1058329A (en) * | 1996-08-23 | 1998-03-03 | Noritake Dia Kk | Segment chip structure of diamond cutting grinding wheel |
| EP1854858A1 (en) * | 1999-08-31 | 2007-11-14 | De Beers Industrial Diamonds (Proprietary) Limited | Abrasive material comprising elongate abrasive bodies |
| EP2324957A2 (en) * | 2005-09-30 | 2011-05-25 | Saint-Gobain Abrasives, Inc. | Abrasive tools having a permeable structure |
| US20120055098A1 (en) * | 2010-09-03 | 2012-03-08 | Saint-Gobain Abrasifs | Bonded abrasive article and method of forming |
| GB2504824A (en) * | 2012-06-11 | 2014-02-12 | Element Six Ltd | Aligning abrasive grains to form tools |
| US20140090308A1 (en) * | 2009-06-25 | 2014-04-03 | 3M Innovative Properties Company | Method of sorting abrasive particles, abrasive particle distributions, and abrasive articles including the same |
| US20160177154A1 (en) * | 2014-12-23 | 2016-06-23 | Saint-Gobain Ceramics & Plastics, Inc. | Shaped abrasive particles and method of forming same |
| WO2016123321A1 (en) * | 2015-01-28 | 2016-08-04 | Diamond Innovations, Inc. | Friable ceramic-bonded diamond composite particles and methods to produce same |
-
2019
- 2019-04-01 GB GB1904564.0A patent/GB2582771A/en not_active Withdrawn
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1058329A (en) * | 1996-08-23 | 1998-03-03 | Noritake Dia Kk | Segment chip structure of diamond cutting grinding wheel |
| EP1854858A1 (en) * | 1999-08-31 | 2007-11-14 | De Beers Industrial Diamonds (Proprietary) Limited | Abrasive material comprising elongate abrasive bodies |
| EP2324957A2 (en) * | 2005-09-30 | 2011-05-25 | Saint-Gobain Abrasives, Inc. | Abrasive tools having a permeable structure |
| US20140090308A1 (en) * | 2009-06-25 | 2014-04-03 | 3M Innovative Properties Company | Method of sorting abrasive particles, abrasive particle distributions, and abrasive articles including the same |
| US20120055098A1 (en) * | 2010-09-03 | 2012-03-08 | Saint-Gobain Abrasifs | Bonded abrasive article and method of forming |
| GB2504824A (en) * | 2012-06-11 | 2014-02-12 | Element Six Ltd | Aligning abrasive grains to form tools |
| US20160177154A1 (en) * | 2014-12-23 | 2016-06-23 | Saint-Gobain Ceramics & Plastics, Inc. | Shaped abrasive particles and method of forming same |
| WO2016123321A1 (en) * | 2015-01-28 | 2016-08-04 | Diamond Innovations, Inc. | Friable ceramic-bonded diamond composite particles and methods to produce same |
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