Evaluating the influence of cutting parameters on part’s accuracy and grinding wheel’s wear in grinding profile for ball bearing’s inner ring groove

This paper presents some research results to determine the impact of grinding parameters on grinding wheel’s wear and part’s accuracy in grinding profile for ball bearing''s inner ring groove.

Vietnam Journal of Science and Technology 56 (4) (2018) DOI: 10.15625/2525-2518/56/4/10892 EVALUATING THE INFLUENCE OF CUTTING PARAMETERS ON PART’S ACCURACY AND GRINDING WHEEL’S WEAR IN GRINDING PROFILE FOR BALL BEARING’S INNER RING GROOVE Nguyen Anh Tuan1, *, Vu Toan Thang2, Nguyen Viet Tiep2 University of Economic and Technical Industries, 456 Minh Khai, Hai Ba Trung, Ha Noi Hanoi University of Science and Technology, Dai Co Viet, Hai Ba Trung, Ha Noi * Email: natuan.ck@uneti.edu.vn Received: 14 November 2017; Accepted for publication: July 2018 Abstract This paper presents some research results to determine the impact of grinding parameters on grinding wheel’s wear and part’s accuracy in grinding profile for ball bearing's inner ring groove Firstly, the distribution diagrams of part’s tolerance zone and grinding wheel’s wear at different cutting conditions has been used to determine important outputs in the profile grinding process for the inner ring groove of the ball bearing Based on that, the experimental regression functions that express the dependencies of the important outputs (grindstone wear Hzi, surface roughness Ra, oval Op) on the technical parameters (normal feed rate Fn, speed of part Vp, depth of cutting t and the number of part in a grinding cycle Np) are determined by the least squares experimental planning method From those mathematical functions, the effect of grinding parameters on the grinding wheel’s wear and part’s accuracy in profile grinding for the inner ring groove is evaluated Keywords: Profile grinding, surface roughness, cutting parameters Classification numbers: 5.1.1, 5.1.3 INTRODUCTION Grinding is a popular finish processing method During the process, the accuracy of part, the durability of grinding wheel as well as the productivity of the process is highly dependent on the parameters of the cutting mode [1] Thus, one of the most important points to achieve the technical and economic efficiency of grinding process is to evaluate the influence of input factors on the change of output factors Then, the output factors will be controlled as requirement Among the output factors that need to be controlled, the part’s accuracy is the most important factor, especially for bearing items (roller bearing) [2] In term of structure, the roller bearing consists of four parts: outer ring, inner ring, roller and cage as the Figure [3, 4] For the inner and outer ring parts of the bearing, the groove surface is the most important The profile grinding currently is one of the most popular machining methods applied to assure the accuracy of the groove surface Vietnam Journal of Science and Technology 56 (4) (2018) DOI: 10.15625/2525-2518/56/4/10892 Figure Structure of roller [3, 4] However, the previous researches have studied primarily on the influence of cutting parameters on part’s surface roughness under surface grinding or cylindrical grinding [5, 6] The influence of technical parameters on part’s accuracy under profile grinding for the inner ring groove of the 6208 ball bearing has not been considered deeply In this paper, the profile grinding operation for the inner ring groove of the 6208 ball bearing was studied Thus, the theoretical background was analyzed to assure the accuracy in profile grinding for the inner ring groove At the same time, experiments were conducted to evaluate the influence of grinding parameters on the accuracy of the parts as well as the wear of grinding wheel RESEARCH CONTENT 2.1 Theoretical basis to assure processing accuracy in profile grinding for the inner ring groove of ball bearing For processing the groove surface, it requires not only dimension accuracy for groove bottom’s diameter, groove’s radius and distance from groove central line to head surface, but also the accuracy for correlative positions including the oval of groove bottom’s diameter, the circular run-out of the groove central line in comparison to the head surface Especially, the surface roughness of groove must be smaller 0.5 µm (Ra < 0.5 µm) [7] These technical requirements of the finish grinding operation for the 6208 ball bearing’s inner ring groove are shown as Figure 9±0.025 R6,17+0.05 Ø48±0.01 0.008 A 0.003 0.5 Figure Drawing shows the technical requirements of the finish grinding operation for the groove of the 6208 ball bearing’s inner ring [7] Evaluating the influence of cutting parameters on part’s accuracy and grinding wheel’s wear … However, the important issue is to find out a solution to assure the part’s accuracy during the process The processing standard errors and cause of these standard errors are necessary to be determined to reduce them Thus, the following solutions would be applied to assure the accuracy in dimension and correlative position as well as surface roughness of the inner ring groove: - The groove surface would be lathed before grinding by hard turning method on CNC machine This decreases surplus stock, increases productivity for groove grinding and decreases the press error causing by bending deform occurring from previous heat treatment During the grinding process, the errors in the geometry of the work-piece cause the same type of errors in the part such as oval, cone, circular run-out, etc [2] If material hardness and surplus stock are inhomogeneous, the errors in the geometry of part will happen It is necessary to lathe the surface of groove before grinding - Applying the profile grinding principle and using 3MK136B profile grinder to process the groove surface The Figure presents the principle diagram of grinding profile for the inner ring groove of ball bearing with grinder 3MK136B nw Grinding wheel e np Work-piece Work-piece holder 3 sn Fn Figure Diagram of profile grinding principle for the groove of the ball bearing’s inner ring [7] 1, 2: Work-piece holder; 3: Magnetic pole; 4: Grinding wheel; 5: Grinding work-piece In this method, the profile of processing surface and working surface of grinding wheel are coincided Grinding process is proceeded by normal motion of machine (rotation motion of work-piece np, rotation motion of grinding wheel (nw) and normal feed motion of workbench Fn) Especially, rough grinding mode, finishing grinding mode and grinding mode without spark are implemented in the same process to improve productivity and ensure the part’s accuracy The normal motion process of the worktable for grinding one product is shown in Figure It is divided into the following stages: The workbench turns rapidly; The workbench approaches forward; The workbench performs a normal motion for the rough grinding; The machine grinds without normal feed motion in a period of ÷ seconds to rough bound; The workbench performs a normal motion for the fine grinding; The machine grinds without normal feed motion in a period of ÷ seconds to fine bound This is fine grinding period to grind without spark It helps to increase the polish and accuracy of the part; The workbench turns back rapidly and returns its origin position; Swing arm of grinder loads/unloads automatically Nguyen Toan Thang, et al Displacement distance of workbench Normal cycle of grinding Annotation Megnetic coil Mechanical arm Feed step motor Demagnetization Magnetization Grasp head in Swing arm load/unload Compensation feed Swing arm load/unload Grasp head out Swing arm return Grasp head in Rapid feed Fast approach feed Rough grinding feed No spark grinding Fine grinding feed No spark grinding 01 02 03 04 05 06 Rapid jump back and return origin Dynamic Compensation profile of movement of workbench workbench 07 08 Grinding time Figure The radial feed motion process of the worktable to grind a part with profile grinding machine 3MK136B - The surface of groove and the head surface of the inner ring are used as the positioning standard to minimize the mounting error and assure the correlative position between the groove central line and the head surface The grinding part is positioned at groove surface by two lock pins or a short V shape block with 120 degree angle to control two degrees of freedom Therefore, the standard surface is coincident with the machining surface to minimize the mounting error Besides, the top face of the work-piece is positioned at the top of the magnetic pole to control three degrees of freedom and ensure parallelism between the groove center and the head The part is tightly clamped by magnet as shown in Figure For this reason, the process of positioning and clamping part is done simply and quickly It improves the machining efficiency and minimizes installation errors However, because profile grinding has a big contact area between the grinding wheel and the work-piece, the cutting force and cutting heat generated in this process are much larger than those in other normal grinding process Thus, the grinding wheel is worn continuously and unequally at various points on the working surface As a result, its initial shape and accuracy change quickly, causing geometric error of the processing surface In addition, the grinding wheel’s wear decreases its cutting capability and durability, increases the cutting force, cutting heat, consumption power and vibration in the grinding process Therefore, grinding wheel’s wear influences directly on the precision elements of the grinding parts including groove’s surface roughness, groove bottom diameter’s oval and dimension accuracy, groove radius’s dimension accuracy For those reasons, the grinding wheel must be dressed frequently in the profile grinding process However, the most important issue is to determine the suitable time to dress the grinding wheel This determines the machining accuracy and the durability of the grinding wheel Thus, it is necessary to determine the economical limitation wear value of the grinding wheel However, the accuracy of the processing part and the wear value of the grinding wheel depend on parameters of the grinding mode Therefore, it is very important to evaluate the effect of grinding parameters on the grinding wheel’s wear and part’s accuracy in profile grinding for the inner ring groove This is the basis to determine suitable cutting parameters 2.2 Experiment to determine the important outputs in profile grinding for the groove of the ball bearing’s inner ring Evaluating the influence of cutting parameters on part’s accuracy and grinding wheel’s wear … 2.2.1 Tools and experimental equipment - The grinding wheel with white fused alumina grains was used to grind the inner ring groove of 6208 ball bearing made from SUJ2 alloy steel Table and table show the specifications of the grinding conditions and grinding wheels Table Specifications of grinding conditions Table Specifications of grinding wheel Work-piece: SUJ2 alloy steel Hardness: 60 ÷ 65 HRC Grinding method: Profile grinding Code Grade Grain Bond 500x8x203WA100xLV60 Soft White fused alumina Vitrified - Equipment for experiment: Profile grinding machine 3MK136B (Figure 5) - Roughness measuring device: SJ400 Roughness Tester (Figure 6) Figure SJ400 Roughness Tester Figure Profile grinding machine 3MK136B - Equipment for measuring radius of the inner ring groove: In the experiment, the roughness and contour meter CL-1A of Shanghai Taile (Figure 7) was used to measure radius of the inner ring groove Figure The pneumatic measuring probe systems to measure grinding wheel’s wear [8, 9] Figure The roughness and contour meter CL-1A of Shanghai Taile - Equipment for measuring wear of the grinding wheel: In this experiment, the wear value of grinding wheel was measured by applying pneumatic probe system [8-10] (Figure 8) The pneumatic probe system measures the wear value at two different points on the working surface of Nguyen Toan Thang, et al the grinding wheel However, this study only considers the wear value at the margin of the curving edge surface of the grinding wheel where the wear value is maximum - Equipment for measuring the diameter of the groove bottom, the oval of the groove bottom diameter, the distance from central line of groove to its head surface and the circular run-out of the groove central line with its head surface In this experiment, the Chinese measurement equipment D022 was used to determine position and the diameter of inner ring groove of the ball bearing (Figure 9) 07 05 04 02 03 01 05 06 06 07 04 03 08 02 01 09 45° 90 ° Figure Images and diagram for structural principle of the measurement equipment D022 This equipment applies the comparative method to measure tolerance of groove bottom’s diameter, the oval of the groove bottom diameter, the circular run-out of its groove central line with its head surface and tolerance of distance from its groove central line to its head surface Before measuring, it is necessary to select standard sample bearing In measuring process, the first step is to press the lever of bracket that is used to fix the groove of bearing (part No 7) to take out the sample bearing After that, the ball bearing’s inner ring No (part need to be measured) is put in the measurement equipment Then, the lever No is released to let the pin No to fix the groove’s position Next, the groove surface that need to be measured will be located on two lock pins No and No In this position, the ball bearing’s inner ring will be circled one round The measuring meter No indicates the maximum and minimum values of the groove bottom’s diameter The difference Evaluating the influence of cutting parameters on part’s accuracy and grinding wheel’s wear … between these maximum and minimum values is its oval value Meanwhile, the measuring meter No indicates the maximum and minimum values of the distance from its groove’s central line to its head surface Based on that, the circular run-out of its groove central line with its head surface is easily determined The value of this tolerance is exactly equal to the difference between the maximum and minimum values of the distance from its groove’s central line to its head surface Therefore, each measurement can simultaneously determine four tolerances including groove bottom diameter’s oval level, the circular run-out of its groove central line to its head surface, groove bottom diameter’s dimension tolerance, the dimension tolerance of distance from its groove central line to its head surface 2.2.2 Experiment method In profile grinding operation, the parameters of the grinding regime include the velocity of cutting (Vw), the velocity of part (Vp), the rate of normal feed (Sn) for rough grinding and fine grinding, the depth of cut (t) for rough grinding and fine grinding, the number of parts in a grinding cycle (Np) However, for grinding on a CNC grinder with a specific grinding wheel, the velocity of grinding wheel is usually chosen according to the specifications of the grinding wheel that has been given by the manufacturer For example, the grinding wheel of 500x8x203WA100xLV60 has the grinding wheel’s velocity (Vw) of 60 m/s Thus, some grinders are manufactured with fixed spindle speed value Therefore, in order to simplify the study, this paper considers only four input parameters which are the rate of normal feed (Sn), the velocity of part (Vp), the depth of cut (t) and the number of parts in a grinding cycle (Np) In addition, the cutting regime for rough grinding has insignificant effect on the quality of grinding parts This article considers only cutting regime parameters for fine grinding to evaluate the influence of its on the machining accuracy and the grinding wheel wear Therefore, the four parameters of the cutting mode selected in this study are the normal feed rate for fine grinding (Sn fine), the velocity of part (Vp), the depth of cut for fine grinding (tfine) and the number of parts in one grinding cycle (Np) The values of other parameters are kept constant throughout the experiment Those input parameters are selected according to basis experiments and a mechanical notebook [10] The specific values are chosen for the experiment including three sets of cutting mode parameters as shown in Table Table Three sets of cutting parameters in the experiment Sn fine Vp tfine Vw Sn rough trough (µm) Np (part) (µm/s) (m/min) (m/s) (µm/s) (µm) The first set of cutting parameters 12.5 12 15 30 60 30 120 The second set of cutting parameters 12.5 12 10 30 60 30 120 The third set of cutting parameters 18 20 30 60 30 120 2.2.3 Experiment results Nguyen Toan Thang, et al After carrying out experiments and collecting results, data is analyzed and processed From the measurement results and based on the technical drawing of the grinding operation (Figure 2), using an application of Matlab software, the diagrams for distribution of the part accuracy tolerances zone and the grinding wheel wear were built as shown in Figure 10, Figure 11 and Figure 12 Part’s accuracy and grinding wheel’s wear (µm) Suitable time to dress grinding wheel to assure part’s accuracy since at this time Ra12 = 0.5 = RaRe Hzlimitation = 9.6 The number of parts Figure 10 Diagram for distribution of the part’s accuracy tolerances zone and the grinding wheel’s wear according to the number of parts with the first set of cutting mode parameters Part’s accuracy and grinding wheel’s wear (µm) Suitable time to dress grinding wheel to assure part’s accuracy since at this time Ra15 = 0.5 = Rare Hzlimitation = 9.9 The number of parts Figure 11 Diagram for distribution of the part’s accuracy tolerances zone and the grinding wheel’s wear according to the number of parts with the second set of cutting mode parameter Evaluating the influence of cutting parameters on part’s accuracy and grinding wheel’s wear … Part’s accuracy and grinding wheel’s wear (µm) Suitable time to repair grinding wheel to assure part’s accuracy since at this time Ra16 = 0.5 = Rare Hzlimitation = 10.3 The number of parts Figure 12 Diagram for distribution of the part’s accuracy tolerances zone and the grinding wheel’s wear according to the number of parts with the third set of cutting mode parameters In Figure 10, Figure 11, Figure 12: + D: Deviation of groove diameter dimension * O: Oval level of groove diameter ∆ A: Dimension deviation of distance from groove’s central line to head surface MD: Circular run-out of groove central line to head surface o R: Dimension deviation of groove radius • Ra: Surface roughness of groove x Hz: Wear value at the edge of the curving edge surface of grinding wheel (All the values showing in diagram with plotting scale of 1, exception for Ra value using plotting scale of 10) From the above diagrams, some findings can be presented as follows: - For a certain set of cutting parameters, when the number of parts in one grinding cycle increases, the wear of grinding wheel and the surface roughness of groove also increase Therefore, according to time progress for each cutting mode, there is a moment at which the processing accuracy of part will exceed the required accuracy With the first set of cutting parameters, when the 12th part is grinded its surface roughness of groove is equal to the required surface roughness value (Ra12 = Rare = 0.5 µm) For this reason, from the 12th part onward, the surface roughness in particular and the processing accuracy in general are not guaranteed as the requirement This is the appropriate time to dress grinding wheel Thus, the wear value at the 12th part is the economic limitation wear value of the grinding wheel corresponding the above cutting mode Therefore, with the first set of cutting parameters the economic limitation wear value is equal to the wear value at the 12th part, i.e Hzlimitation = Hz19 = 9.6 µm - With different cutting parameters, the economic limitation wear values of the grinding wheel are different With the second set of cutting parameters, the economic limitation wear Nguyen Toan Thang, et al value is equal to the wear value at the 15th part, i.e Hzlimitation = Hz15 = 9.9 µm Meanwhile, with the third set of cutting parameters, the economic limitation wear value is equal to the wear value at the 16th part, i.e Hzlimitation = Hz16 = 10.3 µm - When the parameters of cutting mode (Sn, Vp, t) changes, the grinding wheel’s wear value (Hz1, Hz2, etc.), the part’s surface roughness (Ra1, Ra2, etc.) and the oval of groove bottom’s diameter (O1, O2, etc.) will also change For the first set of cutting parameters (figure 10), those values after grinding part no 1, 2, and will be respectively Hz1 = 3.9 µm; Hz2 = 5.0 µm; Hz3 = 5.9 µm; Hz4 = 6.5 µm; Ra1 = 0.37 µm; Ra2 = 0.40 µm; Ra3 = 0.42 µm; Ra4 = 0.44 µm; O1 = O2 = O3 = O4 = 2.83 µm Meanwhile, with the second set of cutting parameters (Figure 11) those values after grinding part no 1, 2, and will be respectively Hz1 = 3.8 µm; Hz2 = 4.9 µm; Hz3 = 5.7 µm; Hz4 = 6.3 µm; Ra1 = 0.35 µm; Ra2 = 0.39 µm; Ra3 = 0.41 µm; Ra4 = 0.42 µm; O1 = O2 = O3 = O4 = 2.67 µm Thus, the cutting mode parameters have influence on the grinding wheel’s wear, the groove’s surface roughness and the oval level of groove bottom’s diameter While the other precision elements of part including groove bottom’s diameter, groove’s radius, distance from its groove center line to its head surface and the circular run-out-of its groove center line to its head surface can be impacted but at very low level This proves that the cutting parameters has influence on the part’s accuracy but mainly on the grinding wheel’s wear, the part’s surface roughness and the groove bottom diameter’s oval This can be explained that in the profile grinding process for the groove of the 6208 ball bearing’s inner ring, the deviation of distance from the groove center line to the head surface and the circular run-out of the groove central line to the head surface are mainly due to the standard error of jigs and fixtures The input parameters of the cutting mode influence insignificantly on the two precision factors mentioned previously Meanwhile, the grinding wheel’s wear has impact on deviation of groove radius and groove bottom diameter However, the error is insignificant in comparison with the requested standard accuracy because the wear value of grinding wheel is very small In order to estimate the degree of this influence, the experiment planning methods should be applied However, the above research results are the base to set up a suitable experiment planning issue in the following section To decrease the number of experiments but still guarantee the expected requirement, it normally only considers the influence of grinding parameters on three output factors which are the most affected They are the part’s surface roughness, groove bottom diameter’s oval and grinding wheel’s wear 2.3 Experiment to determine mathematical functions for the important outputs over technical parameters in profile grinding for the ball bearing’s inner ring groove The experimental conditions here are similar to the experimental conditions in the previous section However, these experiments are implemented with the cutting mode as shown in table Table Experimental conditions Parameters/Factors Experimental levels Low level (1) Base level (2) High level (3) Fn (µm/s) 12.5 20 Vp (m/min) 12 18 t (µm) 10 15 20 Np (part) 10 20 30 Evaluating the influence of cutting parameters on part’s accuracy and grinding wheel’s wear … These input parameters are selected via basic experiment and reference of machine manufacturing technology manual [10] Each above factors varies in levels Thus, it is essential to select orthogonal experiment matrix L81 (34) In other words, 81 experiments have been implemented (as shown in Table 5) Each experiment is equivalent to a collection For example: S2V2t2N2 means of Fn = 12.5; Vp = 12; t = 15; Np = 20 Table Experimental data from 81 experiments Experimental structure Grinding mode Measurement data No Fn Vp t Np Fn µm/s Vp m/min t µm Np part Hzi µm Ra µm Op µm 1 1 10 10 7.8 0.9 2.5 2 2 12.5 12 15 20 11.7 0.53 2.8 18 20 30 15.0 0.64 3.5 … 81 3 3 20 After carrying out experiments and collecting results, data is analyzed and processed In the article, Matlab software was used to determine experimental regression functions under traditional least square method Based on that, the mathematical models, which show the relationship between three important output parameters and four technology parameters, are determined as follows: - Function of grinding wheel’s wear (Hzi): Hzi = 2.1688 ⋅ Fn0.0965⋅ Vp0.0657⋅ t0.0557 ⋅ Np0.3772 By the least squares method, the average error (θtb) is equal to 0.2 %, the error dispersion (σ) is equal to 0.13 - Function of part’s surface roughness (Ra): Ra = 0.163 ⋅ Fn0.1224⋅ Vp0.10002⋅ t0.1005 ⋅ Np0.1194 By the least squares method, the average error (θtb) is equal to 0.3%, the error dispersion (σ) is equal to 0.27 - Function of part’s oval (Op): Op = 1.4498 ⋅ Fn0.19996 ⋅ Vp-0.1127 ⋅ t 0.1966 By the least squares method, the average error (θtb) is equal to 4.58 %, the error dispersion (σ) is equal to 2.94 From the above mathematical functions, some findings can be presented as follows: - When the normal feed rate (Fn) increases, the grinding wheel’s wear (Hzi), the part’s surface roughness (Rai) and the part’s oval (Oi) will increase However, the effect of normal feed rate (Fn) on grinding wheel’s wear (Hzi) and part’s surface roughness (Rai) at the low workpiece speed is smaller than that of at the high work-piece speed In case of part’s oval level (Oi), the influence trend is the opposite At the low work-piece speed, the influence degree of normal feed rate (Fn) on part’s oval level (Oi) is greater than that of at the high work-piece speed 11 Nguyen Toan Thang, et al - When the velocity of work-piece (Vp) increases, grinding wheel’s wear (Hzi) and part’s surface roughness (Rai) will also increase However, the impact of work-piece velocity (Vp) on grinding wheel’s wear (Hzi) and part’s surface roughness (Rai) is smaller than that of normal feed rate (Fn) Especially, the effect of work-piece velocity on the part’s oval (Oi) will be reversed When the velocity of work-piece (Vp) increases, the part’s oval (Oi) decreases And vice versa - When the depth of cut (t) increases, grinding wheel’s wear (Hzi), part’s surface roughness (Rai) and part’s oval (Oi) will also increase However, the amount of increase is negligible This shows that the impact of cutting depth on grinding wheel’s wear and part’s accuracy is insignificant - When the number of parts in a grinding cycle (Np) increases, part’s surface roughness (Rai) and grinding wheel’s wear (Hzi) will also raise Especially, the impact of the number of parts in a grinding cycle (Np) on part’s surface roughness (Rai) and grinding wheel’s wear (Hzi) is much bigger than that of normal feed rate (Fn), work-piece velocity (Vp) and cutting depth (t) However, the number of parts in a grinding cycle (Np) does not affect the part’s oval (Oi) The reason is that when the number of parts in a grinding cycle (Np) increases, the grinding time will also increase On the other hand, the grindstone dresses is only implemented at the end of a grinding cycle in the machining process Therefore, grinding wheel’s wear (Hzi) will increase when the number of parts in a grinding cycle (Np) increases This leads to increase part’s surface roughness However, this does not affect the groove bottom’s diameter deviation of grinding parts at different cross sections CONCLUSION In this study, by using the point coordinate diagram method, the tolerance zone distribution of processing accuracy and the grinding wheel wear according to the number of grinding parts at three different sets of cutting parameters are determined Then, the important outputs of the profile grinding process for the inner ring groove of the ball bearing are determined These important outputs are the part’s surface roughness (Hzi), the groove bottom diameter’s oval (Op) and the grinding wheel’s wear (Hzi) Therefore, among the output parameters there are only three output factors that were selected to study in experiment planning issue Based on that, the experimental regression functions which show the relationship between three important output parameters (grinding wheel’s wear Hzi, part’s surface roughness Ra, part’s oval Op) and the technical parameters (normal feed rate Fn, velocity of part Vp, depth of cut t and the number of part in a grinding cycle Np) are determined At the same time, the impact of cutting parameters on the grinding wheel’s wear Hzi, the part’s surface roughness Ra, the part’s oval Op in profile grinding for the inner ring groove was evaluated The experimental results show that the impact of the number of parts in a grinding cycle (Np) on part’s surface roughness (Rai) and grinding wheel’s wear (Hzi) is the biggest Meanwhile, the normal feed rate (Fn) has the greatest impact on the part’s oval (Op) REFERENCES Yan Li - Intelligent selection of grinding conditions, Ph.D.Thesis, Liperpool John Moores University, 1996 Evaluating the influence of cutting parameters on 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pneumatic probes”, Journal of Mechanical Science and Technology 32 (3) (2018) 1297-1305 10 Nguyen Dac Loc, Le Van Tien, Ninh Duc Ton, Tran Xuan Viet - Handbook of manufacturing technology No 1, Science and Technics Publishing House, Ha Noi, 2005 (written in Vietnamese) 13 ... the technical requirements of the finish grinding operation for the groove of the 6208 ball bearing’s inner ring [7] Evaluating the influence of cutting parameters on part’s accuracy and grinding. .. on parameters of the grinding mode Therefore, it is very important to evaluate the effect of grinding parameters on the grinding wheel’s wear and part’s accuracy in profile grinding for the inner. .. the cutting force, cutting heat, consumption power and vibration in the grinding process Therefore, grinding wheel’s wear influences directly on the precision elements of the grinding parts including