JP5151091B2 - Grinding condition determination method - Google Patents

Description

  The present invention relates to a grinding condition determination method using a grindstone in which a grindstone layer in which abrasive grains are bonded by a bond is formed on the outer peripheral surface of a disk-shaped core.

  Conventionally, in order to determine the grinding conditions by a grindstone in which a grindstone layer in which abrasive grains are bonded with a bond is formed on the outer peripheral surface of a disk-shaped core, an operator actually grinds a workpiece and evaluates grinding burn, When the predetermined standard is not satisfied, the grinding condition is set again. However, in this method for determining grinding conditions, the grinding conditions were set by trial and error, so a lot of time was required. Also, since the grinding conditions were set based on the experience of the operator, the grinding conditions were likely to vary by the operator.

  On the other hand, the grinding condition determination method of patent document 1 is proposed. This grinding condition determination method is shown below. First, at least one of a normal grinding resistance and a tangential grinding resistance and an allowable value of the ratio are set in advance, and the normal grinding resistance and the tangential grinding resistance are measured during processing, and the ratio is calculated. When the ratio is within the allowable range, the grinding condition is determined by comparing at least one of the normal grinding resistance and the tangential grinding resistance with the measured value.

According to the grinding condition determination method described in Patent Document 1, it is possible to determine a grinding condition without variations in a short time without trial and error or operator experience.
JP-A-4-315571

  However, in the grinding condition determination method described in Patent Document 1, the relationship between the allowable value and the grinding burn is unclear, and it is difficult to say that the evaluation of the grinding burn is sufficient.

  The present invention has been made in view of the conventional problems, and provides a grinding condition determination method capable of determining a grinding condition without variation in a short time and suppressing the occurrence of grinding burn. To do.

  The inventor has conducted earnest research to solve the above problems, paying attention to the fact that the normal grinding resistance is calculated by conic modeling the cutting edge of the abrasive grains, and the following invention is completed. It came.

That is, the grinding condition determination method according to claim 1 is characterized in that in the grinding condition determination method using a grindstone in which a grindstone layer in which abrasive grains are bonded by a bond is formed on the outer peripheral surface of a disk-shaped core, the grinding surface of the grindstone is formed. A cross-sectional area acquisition step for obtaining an abrasive cross-sectional area at a predetermined cutting depth from the outermost surface of the abrasive grain to be performed, a cone of an abrasive cutting edge having the abrasive cross-sectional area as a bottom area and the predetermined cutting depth as a height Assuming a model, a tangent calculation step for calculating a tangent to a half apex angle that is ½ of the apex angle of the conical model, a parameter setting step for setting a grinding parameter, and a tangential grinding resistance from the grinding parameter and the tangent A tangential grinding resistance calculating step for calculating the tangential grinding resistance, a grinding heat amount calculating step for calculating a grinding heat amount from the tangential grinding resistance, a maximum temperature calculating step for calculating a maximum temperature at a grinding point from the grinding heat amount, and the maximum temperature The comparator compares the value is to comprise a grinding burn determining step determines grinding burn.

  The grinding condition determination method according to claim 2 is characterized in that, in claim 1, the cross-sectional area acquisition step includes a data group acquisition step of acquiring a data group representing a three-dimensional shape of the abrasive grain surface with a laser microscope, and the data A cross-sectional area calculating step for obtaining the cross-sectional area of the abrasive grains based on a group.

The grinding condition determination method according to claim 3 is characterized in that, in claim 1 or 2, the grinding parameters include specific grinding energy Cp, grinding wheel peripheral speed V, cutting depth d per work rotation, grinding width b, work Work speed v, friction coefficient μ between abrasive grains and workpiece, contact length L between grinding wheel and workpiece, workpiece density ρ, specific heat c of workpiece, thermal conductivity k of workpiece, workpiece When the half apex angle of the conical model is α and the constants are K1 and K2,
Tangential grinding resistance Ft is
Ft = Cp (vdb / V) + μCp (πvdb / 2V) tanα
The amount of grinding heat Q is
Q = (FtV) / (Lb)
Maximum temperature θmax is
θmax = K1 {L / (ρckv)} ^K2 × aQ
It is required by.

A feature of a grinding condition determination method according to a fourth aspect is that in any one of the first to third aspects, the predetermined cutting depth is a cutting depth of an abrasive cutting edge.

In the grinding condition determination method according to claim 1, since the grinding condition is determined so that the maximum temperature obtained through the predetermined process is equal to or lower than the threshold value, the grinding condition is determined without trial and error or operator experience. Can be determined. Further, in this grinding condition determination method, assuming a conical model of an abrasive cutting edge having a bottom area of the abrasive grain cross-sectional area at a predetermined cutting depth from the outermost surface of the abrasive grains, and a predetermined cutting depth as a height, The normal grinding resistance calculated from the tangent to the half apex angle and the grinding parameters agrees well with the measured values. Therefore, based on this conical model, it is considered that the tangential grinding resistance, the amount of grinding heat and the maximum temperature calculated from the normal grinding resistance also agree well with the actual values. Therefore, according to this grinding condition determination method, it is possible to determine a grinding condition that does not vary in a short time, and to suppress the occurrence of grinding burn.

In the grinding condition determination method according to claim 2, a data group representing a three-dimensional shape of the abrasive grain surface is obtained by a laser microscope in the data group acquisition step, and the abrasive grain cross-sectional area is based on the data group in the cross-sectional area calculation step. Therefore, it is possible to accurately measure the abrasive grain cross-sectional area at a predetermined cutting depth from the outermost surface of the abrasive grain.

  In the grinding condition determination method according to claim 3, the specific grinding energy Cp, the grinding wheel peripheral speed V, the cutting depth d per rotation of the workpiece, the grinding width b, the workpiece speed v, and between the abrasive grains and the workpiece. Friction coefficient μ, contact length L between grinding wheel and workpiece, workpiece density ρ, workpiece specific heat c, workpiece thermal conductivity k, workpiece heat distribution a, and cone model half apex angle Since tangential grinding resistance Ft, grinding heat quantity Q and maximum temperature θmax are calculated from α, the maximum temperature θmax can be easily obtained.

In the grinding condition determination method according to the fourth aspect, since the predetermined depth of cut is the depth of cut of the abrasive cutting edge, it becomes an appropriate conical model, and the tangential grinding resistance Ft, the grinding heat quantity Q, and the maximum temperature θmax are accurately determined. Can be requested.

  An embodiment embodying a grinding condition determination method according to the present invention will be described below with reference to the drawings. FIG. 1 shows a grinding machine used in this grinding condition determination method. In this grinding machine, the workpiece 1 is pressed and supported by the spindle 5 a of the spindle stock 5 and the tailstock 6 a of the tailstock 6. A grindstone 10 is fixed to the rotary shaft 7 a of the grindstone table 7, and the rotary shaft 7 a and the grindstone 10 are driven to rotate at a higher speed than the motor 8. Then, when the grindstone 10 contacts the workpiece 1, the workpiece 1 is ground. Here, the grinding width is represented by b.

  The relationship between the grindstone 10 and the workpiece 1 is shown in FIG. In the grindstone 10, a grindstone layer 12 in which superabrasive grains of CBN (cubic boron nitride) or diamond are bonded together is formed on the outer peripheral surface of the disk-shaped core 11. The grindstone layer 12 is composed of a plurality of grindstone chips 13. Here, the grindstone peripheral speed is represented by V, the workpiece speed is represented by v, the cutting depth per rotation of the workpiece 1 is represented by d, and the contact length between the grindstone 10 and the workpiece 1 is represented by L.

  FIG. 3 shows a grinding condition determining apparatus used in the grinding condition determining method of the embodiment. This grinding condition determination device includes a laser microscope 20 and a control device 21. The laser microscope 20 includes a laser projector 20 a that irradiates the grindstone chip 13 with laser and a CCD camera 20 b that detects the laser reflected from the grindstone chip 13. The laser microscope 20 and the control device 21 are electrically connected.

  Next, the grinding condition determination method will be described with reference to the flowchart of the grinding condition determination program shown in FIG. The grinding condition determination device is provided at a predetermined position on the grinding machine, for example, on the rear side of the grinding wheel 10. Then, by pressing a start switch (not shown), execution of the grinding condition determination program shown in FIG. 4 is started.

  When the execution of the grinding condition determination program shown in FIG. 4 is started, first, in step S10, a data group representing a three-dimensional shape of a predetermined region of the grindstone tip 13 is acquired. Specifically, the grindstone chip 13 is irradiated with laser from the laser projector 20 a according to a command from the control processing device 21. Further, the laser reflected from the grindstone chip 13 is detected by the CCD camera 20 b, and the data is transferred to the control processing device 21. This data represents the distance in the Z-axis direction from the reference XY plane of the surface of the grindstone tip 13 when the grinding surface of the abrasive grains is the reference XY plane. Thus, the data transferred from the CCD camera 20 b to the control processing device 21 is a data group representing a three-dimensional shape of a predetermined area of the grindstone chip 13 and is stored in the memory of the control processing device 21. As shown in FIG. 5, one data group is acquired for each mesh divided at predetermined intervals in the X-axis direction and the Y-axis direction, and stored as matrix data. However, in FIG. 5, for convenience, the matrix rows are b1 to b10 and the columns are a1 to a10. Here, step S10 is a data group acquisition step.

  In step S11, based on the data group, the abrasive grain cross-sectional area A at the cutting depth g of the abrasive grain cutting edge is calculated from the abrasive grain outermost surface. Specifically, the area surrounded by the data representing the cutting depth g in the data group shown in FIG. In this way, the abrasive grain cross-sectional area A at the cutting depth g of the abrasive grain cutting edge can be accurately measured. In addition, the cutting depth g is 10 micrometers or less, and is about 3-5 micrometers normally. Further, the position from the outermost surface of the abrasive grains for obtaining the abrasive grain cross-sectional area A is arbitrary, but if this is the cutting depth g of the abrasive grain cutting edge, it is preferable because the calculated value and the measured value are more consistent. Here, step S11 is a cross-sectional area calculation step. Moreover, step S10 and step S11 are cross-sectional area acquisition processes.

  In step S12, the cutting edge of the abrasive grain is assumed by the conical model 30, and the tangent tan α of the half apex angle α is calculated. That is, as shown in FIG. 6, assuming a conical model 30 of an abrasive cutting edge having an abrasive grain cross-sectional area A as a bottom area with a radius r and a cutting depth g as a height, the apex angle of the conical model 30 is assumed. The tangent tan α with respect to the half apex angle α, which is 1/2, is calculated by the following equation (4). In FIG. 6, Ft is a tangential grinding resistance that is a force necessary to grind the workpiece 1. Further, Fn is a normal grinding resistance which is a force necessary for penetrating the abrasive grains into the workpiece 1. Here, step S12 is a tangent calculation step.

  In step S13, grinding parameters are set. The grinding parameters are specific grinding energy Cp, grinding wheel peripheral speed V, cutting depth d per work rotation, grinding width b, work speed v, friction coefficient μ between the abrasive grains and the work piece, grinding wheel and work piece. At least one of a contact length L, a density ρ of the workpiece, a specific heat c of the workpiece, a thermal conductivity k of the workpiece, and a heat distribution ratio a to the workpiece. However, the grinding parameters automatically determined by the workpiece 1 need only be set once at the beginning. Here, step S13 is a parameter setting step.

  In step S14, the tangential grinding resistance Ft is calculated. When the grinding parameters are set as described above, the normal grinding resistance Fn is calculated from the grinding parameters and the tangent tan α of the half apex angle α according to the following equation (5). Further, the tangential grinding resistance Ft is calculated by the equation shown in the following formula 6. Then, the tangential grinding resistance Ft is obtained by the following equation (7) from the equations (5) and (6). Thereby, the tangential grinding resistance Ft about one abrasive grain is obtained. Here, step S14 is a tangential grinding resistance calculation step. In this embodiment, the tangential grinding resistance Ft for 10 abrasive grains is obtained.

  In step S15, the grinding heat quantity Q is calculated. The amount Q of grinding heat is calculated by the equation shown in the following equation (8). Step S15 is a grinding heat quantity calculation step.

  In step S16, the maximum temperature θmax is calculated. The maximum temperature θmax is obtained by the equation shown in the following equation (9). However, in the present embodiment, K1 is 1.1128 and K2 is 0.5, and calculation is performed according to the following equation (10). Step S16 is a maximum temperature calculation step.

  In this grinding condition determination method, the specific grinding energy Cp, the grinding wheel circumferential speed V, the cutting depth d per rotation of the workpiece, the grinding width b, the workpiece speed v, the friction coefficient μ between the abrasive grains and the workpiece, Contact length L between the grindstone and the workpiece, the density ρ of the workpiece, the specific heat c of the workpiece, the thermal conductivity k of the workpiece, the heat distribution rate a to the workpiece, the half apex angle α of the cone model, the constant Since the tangential grinding resistance Ft, the grinding heat quantity Q and the maximum temperature θmax are calculated from K1 and K2, the maximum temperature θmax can be easily obtained.

  A graph showing the relationship between the tangent tan α of the half apex angle α and the normal grinding resistance is shown in FIG. G1 is a calculated value graph, and G2 is a measured value graph. FIG. 7 shows that there is a correlation between the calculated value and the actually measured value.

  In step S17, the maximum temperature θmax is compared with a threshold value. However, the maximum temperature θmax is an average value for 10 abrasive grains. When the maximum temperature θmax is smaller than the threshold value (YES), it is determined that grinding burn does not occur, and the process proceeds to step S18. If the maximum temperature θmax is equal to or higher than the threshold (NO), it is determined that grinding burn will occur, and the process proceeds to step S19. At this time, the relationship between the half apex angle α and the maximum temperature θmax is shown in FIG. In FIG. 8, if grinding burn occurs when the maximum temperature θmax is equal to or greater than θ0 (that is, θ0 is set as a threshold value), it indicates that grinding burn occurs when the half apex angle α is equal to or greater than α0.

  In step S18, the fact that the grinding conditions do not cause grinding burn is displayed on the monitor of the control device 21, and the execution of the program is terminated. Further, in step S19, the fact that the grinding condition is caused by grinding burn is displayed on the monitor of the control device 21, the process returns to step S13, and the grinding parameters are set again. Therefore, the grinding parameters are reset until the maximum temperature θmax becomes smaller than θ0. However, the grinding parameters to be reset are other than those automatically determined by the workpiece 1, and are mainly the workpiece speed v and the cutting depth d. Here, steps S17, S18, and S19 are grinding burn determination steps. The grinding condition determination program is executed before starting the grinding operation and every predetermined time between truing operations or every time a predetermined number of workpieces 1 are ground.

  In the grinding condition determination method of the present embodiment, since the grinding conditions are determined so that the maximum temperature θmax obtained through a predetermined process is equal to or less than the threshold value, the grinding conditions are not caused by trial and error or operator experience. Can be determined. Further, in this grinding condition determination method, a conical model of an abrasive cutting edge in which the abrasive grain cross-sectional area A from the outermost surface of the abrasive grain to the cutting depth g of the abrasive grain is the bottom area and the cutting depth g is the height. Assuming 30, the normal grinding resistance Fn calculated from the tangent tan α to the half apex angle α and the grinding parameters is in good agreement with the measured value. Therefore, based on the cone model 30, it is considered that the tangential grinding resistance Ft, the grinding heat quantity Q, and the maximum temperature θmax calculated from the normal grinding resistance Fn agree well with the actual values. Therefore, according to the grinding condition determination method of the present embodiment, it is possible to determine a grinding condition that does not vary in a short time, and it is possible to suppress the occurrence of grinding burn.

  In the present embodiment, the three-dimensional shape of a predetermined region of the grindstone tip 13 is measured to obtain the abrasive grain cross-sectional area A. However, the three-dimensional shape of the predetermined region of the workpiece 1 is measured to obtain an abrasive. The grain cross-sectional area A may be obtained. Alternatively, the surface of the abrasive grain may be subjected to gold vapor deposition, and the area of the gold peeled off by grinding may be measured to obtain the abrasive grain cross-sectional area A. Further, the abrasive grain cross-sectional area A may be obtained by mechanically measuring a three-dimensional shape of a predetermined region of the workpiece 1 using a stylus. Moreover, when calculating | requiring the abrasive grain cross-sectional area A, a grinding machine may be stopped and it does not need to be stopped.

  As mentioned above, although the grinding condition determination method of the present invention has been described according to the embodiment, the present invention is not limited to these, and it can be applied with appropriate modifications as long as it is not contrary to the technical idea of the present invention. Needless to say.

The outline figure of a grinding machine concerning an embodiment. The figure which concerns on embodiment and shows the relationship between a grindstone and a workpiece. 1 is a schematic diagram of a grinding condition determination device according to an embodiment. The flowchart of the grinding condition determination program according to the embodiment. The figure of the data group which concerns on embodiment and represents the three-dimensional shape of the grindstone chip surface. The perspective view of the cone model of the cutting edge of an abrasive grain according to an embodiment. The graph of a tangent of a half apex angle and a normal grinding resistance according to the embodiment. The graph of a half apex angle and the maximum temperature according to the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Disk shaped core, 12 ... Grinding stone layer, 20 ... Laser microscope, 30 ... Conical model, S10, S11 ... Cross-sectional area acquisition process (S10 ... Data group acquisition process, S11 ... Cross-sectional area calculation process), S12 ... Tangent calculation process , S13 ... parameter setting step, S14 ... tangential grinding resistance calculation step, S15 ... grinding heat quantity calculation step, S16 ... maximum temperature calculation step, S17, S18, S19 ... grinding burn judgment step, 21 ... control device), Ft ... tangential grinding Resistance, α: Half apex angle, A: Abrasive cross section, g: Depth of cut, d: Depth of cut, Cp: Specific grinding energy, V: Grinding wheel peripheral speed, v: Workpiece speed, b: Grinding width, L ... contact length, μ ... friction coefficient, ρ ... density, c ... specific heat, k ... thermal conductivity, a ... heat distribution rate, Q ... grinding heat quantity, Qmax ... maximum temperature.

Claims (4)

In a method for determining grinding conditions by a grindstone in which a grindstone layer in which abrasive grains are bonded by a bond is formed on the outer peripheral surface of a disk-shaped core,
A cross-sectional area acquisition step of obtaining an abrasive cross-sectional area at a predetermined cutting depth from the outermost surface of the abrasive grains forming the grinding surface of the grindstone,
Assuming a conical model of an abrasive grain cutting edge with the abrasive grain cross-sectional area as the bottom area and the predetermined cutting depth as the height, the tangent to the half apex angle that is ½ of the apex angle of the conical model is calculated. Tangent calculation process,
A parameter setting process for setting grinding parameters;
A tangential grinding resistance calculation step of calculating a tangential grinding resistance from the grinding parameters and the tangent;
A grinding heat quantity calculating step for calculating a grinding heat quantity from the tangential grinding resistance;
A maximum temperature calculation step of calculating the maximum temperature at the grinding point from the amount of grinding heat;
A grinding condition determining method comprising: a grinding burn determining step of comparing the maximum temperature with a threshold value and determining grinding burn.   In Claim 1, the cross-sectional area acquisition step includes a data group acquisition step of acquiring a data group representing a three-dimensional shape of the abrasive grain surface by a laser microscope, and a cross-sectional area for obtaining the abrasive cross-sectional area based on the data group. A grinding condition determination method comprising: a calculation step. 3. The grinding parameter according to claim 1, wherein the grinding parameters include specific grinding energy Cp, grinding wheel peripheral speed V, depth of cut d per workpiece rotation, grinding width b, workpiece speed v, and between the abrasive grains and the workpiece. The friction coefficient μ, the contact length L between the grindstone and the workpiece, the density ρ of the workpiece, the specific heat c of the workpiece, the thermal conductivity k of the workpiece, and the heat distribution ratio a to the workpiece, Assuming that the half apex angle of the conical model is α and the constants are K1 and K2, the tangential grinding resistance Ft is the following formula 1, the grinding heat quantity Q is the following formula 2, and the maximum temperature θmax is the following formula 3. The grinding condition determination method characterized by being calculated | required by the type | formula of this.
(Equation 1)
Ft = Cp (vdb / V) + μCp (πvdb / 2V) tanα
(Equation 2)
Q = (FtV) / (Lb)
(Equation 3)
θmax = K1 {L / (ρckv)} ^K2 × aQ 4. The grinding condition determination method according to claim 1, wherein the predetermined depth of cut is a depth of cut of an abrasive cutting edge.

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