JP2017056516A - Surface grinding method of workpiece and surface grinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface grinding method and a surface grinder capable of efficiently grinding hard-brittle material, hardly grind material and other workpiece with a properly high load.SOLUTION: When a grinding load is raised while monitoring the grinding load upon surface grinding of a workpiece by means of a grinding stone, a cutting speed of the grind stone is reduced and, when the grinding load is lowered, the cutting speed is increased. Corresponding to a plurality of respective load thresholds of grinding load, such respective cutting speeds that, as the grinding load gets to larger, the cutting speed of grinding stone gets to slower are preset, the grinding is started at a prescribed speed and, thereafter, every time when the grinding load is raised/lowered to a prescribed threshold, the speed of grinding stone is reduce/increased up to the corresponding cutting speed.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a surface grinding method and a surface grinding machine for surface grinding a workpiece.

  In a surface grinder equipped with a cup-type grindstone, when grinding a work made of hard and brittle materials such as silicon wafers used for manufacturing semiconductor elements, the load current of the grindstone shaft drive motor is monitored and the tip of the grindstone shaft is Grinding the grindstone by retracting the grindstone when the load current of the grindstone shaft drive motor exceeds the specified threshold due to clogging of the grindstone, cutting the grindstone at a predetermined cutting speed and performing in-feed grinding of the work on the rotary table. After the operation is interrupted, the grindstone is cut again and brought into contact with the workpiece to promote self-growth of the grindstone (Patent Document 1).

JP 2006-35406 A

  In such a conventional grinding method, the grindstone is cut at a predetermined cutting speed, but when the grindstone being ground becomes clogged, the grindstone is temporarily retracted and the grinding is interrupted. It cuts again to encourage the self-growth of the grindstone. For this reason, the workpiece cannot be ground in a high load state where the grinding efficiency of the grindstone is high, and the grinding cycle becomes long, making it difficult to efficiently grind the workpiece in a short time.

  Also, in conventional grinding methods other than the grinding method of Patent Document 1, a grinding method in which a grinding wheel is cut into a workpiece at a constant cutting speed during grinding, and a rough grinding feed according to the cutting feed amount of the grinding stone. There is a grinding method (hereinafter, referred to as a normal grinding method) in which grinding is carried out while the intermediate finish grinding feed, the finish grinding feed and the feed speed are sequentially shifted in the deceleration direction.

  However, with the former grinding method, the balance between the wear amount of the grinding wheel, the removal amount of the workpiece and the cutting amount of the grinding wheel is lost during grinding, so that the grinding load increases rapidly or only the grinding wheel is worn. For this reason, it has been difficult to efficiently and stably grind the workpiece in a high load state where the grinding wheel is efficiently ground.

  Even in the latter grinding method, the workpiece could not be efficiently and stably ground in a high load state with good grinding efficiency of the grindstone for the following reasons. Especially when grinding a hard and brittle material with high hardness and brittleness, the grinding wheel is cut while changing the feed speed of the grinding wheel so as not to be overloaded by the grinding of the grinding wheel. It is necessary to grind for a long time.

  However, in the case of such a hard and brittle material, the surface of the grindstone is self-generated (changed) several times during grinding, and the grinding load changes greatly up and down. This is because the sharpness of the grindstone is poor before self-growth, but once the self-growth of the grindstone occurs, the cutting edge of the grindstone increases and the sharpness sharply improves. As a result, the friction coefficient between the grindstone and the workpiece changes, and the grinding load changes greatly up and down. Therefore, it is impossible to efficiently and stably grind in a short time with a high load with good grinding efficiency.

  Further, during self-growth, the axial distance between the grindstone shaft and the rotary table often decreases due to rapid thermal displacement of the grindstone, workpiece, and machine due to an increase in frictional heat. This is the same as increasing the cutting speed of the grindstone, and causes a sharp increase in grinding load. If the grinding load increases too much, an abnormal grinding load may be detected and the machine may finish processing, or in the worst case, the grindstone or workpiece may be damaged, or the machine may be damaged.

  In view of such conventional problems, the present invention can efficiently grind hard and brittle materials, difficult-to-cut materials, and other workpieces with an appropriate high load, and a workpiece or a grindstone caused by a sudden increase in grinding load, Furthermore, it is an object of the present invention to provide a surface grinding method and a surface grinding machine that can prevent damage to a machine and reduce grinding wheel wear.

  The surface grinding method for a workpiece according to the present invention reduces the cutting speed of the grinding wheel as the grinding load increases while the grinding load is monitored when the workpiece is surface ground with the grinding stone.

  In another surface grinding method for a workpiece according to the present invention, when grinding a workpiece with a grindstone, the grinding load is reduced when the grinding load is increased while the grinding load is monitored, and the grinding load is lowered. When it is done, the cutting speed is increased.

  In addition, corresponding to each load threshold of the grinding load, each cutting speed at which the cutting speed of the grindstone becomes slower as the grinding load increases is set, and after starting grinding at a predetermined speed, the grinding load Each time is increased / decreased to a predetermined load threshold, the grindstone may be decelerated / accelerated to the corresponding cutting speed.

  Alternatively, a return load threshold higher than the maximum load threshold at the time of cutting of the grindstone may be set, and grinding may be performed while returning the grindstone at a predetermined return speed when the grinding load exceeds the return load threshold. You may repeat cutting and returning of a grindstone before a spark out.

  Furthermore, when the grinding load exceeds the load threshold for speed limit execution, even if the grinding load subsequently drops to the load threshold for the predetermined cutting speed, the grindstone is moved at a limited cutting speed that is slower than the predetermined cutting speed. You may make it not make it cut faster than the cutting and the limit cutting speed.

  A surface grinder according to the present invention is a surface grinder for infeed grinding a workpiece with a grindstone, and includes a grinding load measuring means for measuring a grinding load of a grindstone being ground, and a plurality of load thresholds corresponding to a plurality of load thresholds. Compare the speed setting means with the grinding wheel cutting speed and the grinding load and load threshold during grinding so that the grinding wheel cutting speed decreases and increases as the grinding load increases and decreases. Speed control means for increasing and decelerating the grindstone at a cutting speed corresponding to each load threshold with reference to the load threshold.

  According to the present invention, hard and brittle materials, difficult-to-cut materials, and other workpieces can be efficiently ground with a moderately high load, and damage to the workpiece, the grindstone, and the machine due to a sharp increase in the grinding load can be prevented. In addition, there is an advantage that grinding wheel wear can be reduced.

It is a front view of the surface grinding machine which shows the 1st Embodiment of this invention. It is a perspective view of the principal part. It is a block diagram of the control system. It is the same speed table. It is a flowchart of the grinding operation. It is a figure which shows the change of the grinding load, etc. It is a block diagram of a control system showing a second embodiment of the present invention. It is a flowchart of the grinding operation. It is the same speed table. It is a figure which shows the change of the grinding load. It is a block diagram of a control system showing a third embodiment of the present invention. It is the same 1st speed table. It is the 2nd speed table. It is a speed table which shows the 4th Embodiment of this invention. It is a block diagram which shows the 5th Embodiment of this invention. It is a wave form diagram of the same speed change.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  1 to 6 illustrate a first embodiment of the present invention. As shown in FIGS. 1 and 2, the surface grinder 2 used when in-feed grinding a work W made of a hard and brittle material such as a sapphire wafer with the cup-type grindstone 1 detachably mounts the work W on the upper surface. A rotating table 3, a work driving means 4 such as a motor for rotating the rotating table 3 around the vertical axis in the direction of arrow a, and a grindstone shaft 5 arranged on the rotary table 3 so as to be movable up and down. And a grindstone driving means 6 such as a motor for rotating the grindstone shaft 5 in the direction of arrow b around the vertical axis, and a rotary table that is detachably attached to the lower end of the grindstone shaft 5 and rotated in the direction of arrow b. 3 is provided with a grindstone 1 for surface-grinding the workpiece W on 3 and a grindstone feeding means 7 for feeding the grindstone 1 in a vertical cutting direction c and a return direction d via a grindstone shaft 5. In addition, the rotation direction of the rotary table 3 and the grindstone 1 is arbitrary.

  FIG. 3 shows a control system for controlling the grinding operation of the surface grinding machine 2. The control system includes, for example, a sizing control means 10 and a grindstone cutting back control means 11 in addition to the NC control means 9 for controlling a general grinding operation related to the infeed grinding of the surface grinder 2.

  The sizing control means 10 measures the dimensions of the workpiece W being ground by the dimension measuring means 12, and issues a spark out command to the grindstone feeding means 7 when the predetermined spark out time comes, and the workpiece W is moved by the spark out. Control to finish to a predetermined dimensional accuracy.

  If there is a spark-out command, the grindstone feeding means 7 stops the grindstone shaft 5 feed so that the grindstone 1 continues to process the workpiece W at that position. When there is no fixed size control means 10, a spark-out command may be issued when a predetermined cutting amount is reached from the start of grinding of the workpiece W or when a predetermined time has elapsed.

  The grindstone cutting back control means 11 cuts the grindstone 1 so that the grindstone 1 efficiently grinds the workpiece W with an appropriate high load with high grinding efficiency while monitoring the grinding load during grinding of the workpiece W. A function for controlling the return, a function of reducing the cutting speed of the grindstone 1 as the grinding load increases, and a function of repeating the cutting and returning of the grindstone 1 when the grinding load rises to near the upper limit. And a function of increasing the speed of the grindstone 1 as the grinding load decreases.

  The grinding wheel cutting / returning control means 11 is specifically a grinding load measuring means 13 for measuring the grinding load of the grinding wheel 1 during grinding, and a speed setting for setting the cutting speed and the returning speed of the grinding wheel 1 for each load threshold. The speed at which the grindstone feeding means 7 is controlled by the cutting speed and the return speed set by the speed setting means 14 in accordance with the increase / decrease of the grinding load by comparing the means 14 with the actual grinding load during grinding and the load threshold. And control means 15.

  The grinding load measuring means 13 measures the grinding load of the grinding wheel 1 being ground by a change in current, power, torque, etc. flowing through the grinding wheel driving means 6. The speed setting means 14 has a speed table as shown in FIG. In the speed table, load thresholds L1 to L7 at which the grinding load increases step by step for each of high speed cutting, early cutting, middle cutting, slow cutting, slow return, middle return, fast return, and emergency return operations. (N · m) and cutting speeds V0 to V7 (mm / min) that increase and decrease in stages corresponding to the load threshold values L1 to L7 (N · m) are set.

  The high-speed cutting is a cutting when the grindstone 1 comes into contact with the workpiece W to start grinding, and the high-speed cutting speed V0 is set to 0.5 (mm / min). Early cutting is performed at an early cutting speed V1 = 0.3 (mm / min) with respect to the load threshold L1, and intermediate cutting is performed at an intermediate cutting speed V2 = 0.1 (mm / min) with respect to the load threshold L2. The slow cutting is set to a slow cutting speed V3 = 0.05 (mm / min) with respect to the load threshold L3.

  Further, the slow return is a slow return speed V4 = −0.05 (mm / min) with respect to the load threshold L4, and the medium return is a medium return speed V5 = −0.1 (mm / min) with respect to the load threshold L5. The fast return is set to the fast return speed V6 = −0.3 (mm / min) with respect to the load threshold L6. The emergency return is set to the return speed V7 (full speed) with respect to the load threshold L7.

  In addition, since the return is in the reverse direction with respect to the cut, in order to describe the slow return speed V4 and the like, a numerical value is added to indicate that the process proceeds in the reverse direction.

  Each of the load thresholds L1 to L7 has a relationship that increases sequentially from the load threshold L1 to the load threshold L7 as illustrated for the load thresholds L1 to L4 in FIG. The cutting speeds V0 to V3 and return speeds V4 to V7 of the grindstone 1 corresponding to the load thresholds L1 to L7 of the grinding load take into account the combination of the material and size of the workpiece W, the grindstone 1, the surface grinder 2, and the like. Thus, it is determined in advance by experiments or the like so that the grindstone 1 can efficiently grind the workpiece W in a moderately high load state with high grinding efficiency.

  Therefore, high-speed cutting, early cutting, medium cutting, and slow cutting are performed in the cutting direction stepwise toward the cutting speeds V1 to V3 as the grinding load increases stepwise to the load thresholds L1 to L3. It is designed to slow down. In addition, the slow return, middle return, fast return, and emergency return increase in the return direction stepwise from the return speed V4 to V7 as the grinding load increases stepwise from the load threshold L4 to L7. Yes. The return speeds V4 to V7 of the grindstone 1 are that the grindstone 1 moves in the direction opposite to the cutting direction, so that if the grindstone 1 is based on the cutting direction, it is decelerated stepwise from slow return to emergency return. Yeah.

  In addition, when there is a standard speed table corresponding to the standard work W, the numerical value of the standard speed table is read according to the difference in the material of the work W, etc., and the control is performed while correcting it. May be.

  The load threshold value L3 at the time of delay cutting and the load threshold value L4 at the time of delay return are higher than the load threshold value L4 at the time of delay return, but before the spark out after exceeding the load threshold L3, When repeating the slow return multiple times, for example, when the grinding load is equal to or higher than the load threshold L3 and lower than the load threshold L4, the grindstone 1 is delayed and when the grinding load is equal to or higher than the load threshold L4, the grindstone 1 is delayed. As described above, the slow cutting and the slow return of the grindstone 1 are switched based on the load threshold L4.

  Next, a method for grinding the workpiece W will be described with reference to the flowchart of FIG. In-feed grinding of the workpiece W by the surface grinding machine 2 is performed under the control of the NC control means 9. When the surface grinder 2 starts grinding operation for in-feed grinding (S1), the grindstone feeding means 7 is at a high speed feed speed higher than the high speed cutting speed V0 until the grindstone 1 first contacts the workpiece W. 5 is sent in the cutting direction. On the other hand, the dimension of the workpiece W measured by the dimension measuring means 12 is measured (S2), the grinding load measured by the grinding load measuring means 13 is measured (S3), and whether or not the sizing control means 10 is a spark-out time is determined. Judgment is made (S4).

  Immediately after the start of the grinding operation, since it is not yet the spark-out time (S4), it is determined whether or not the grinding load is less than the load threshold L1 for early cutting (S5), and the feed speed of the grinding wheel shaft 5 is determined from the high speed feed speed. The speed is reduced to the high speed cutting speed V0, and the grindstone 1 starts grinding the workpiece W at the high speed cutting speed V0 (S6).

  Until the grindstone 1 comes into contact with the workpiece W, the grindstone shaft 5 is fed at a high feed rate that is faster than the high-speed cutting speed V0, and immediately before the grindstone 1 comes into contact with the workpiece W, the air is decelerated to the high-speed cutting speed V0. The cutting time can be shortened to efficiently shift to grinding of the workpiece W.

  When the grindstone 1 comes into contact with the workpiece W and starts grinding, the grinding load applied to the grindstone shaft 5 increases, but the grindstone 1 is cut at a high cutting speed V0 while the grinding load is less than the load threshold L1 (S6). . If the grinding load increases due to the high-speed cutting at the high-speed cutting speed V0 and becomes equal to or higher than the load threshold L1 and less than the load threshold L2 (S5, S7), the cutting speed of the grindstone 1 is changed from the high-speed cutting speed V0. The speed is reduced to the fast cutting speed V1 (S8), and the grinding of the workpiece W is continued while cutting the grindstone 1 at the fast cutting speed V1.

  If the grinding load increases due to the rapid cutting at the rapid cutting speed V1 and becomes equal to or greater than the load threshold L2 and less than the load threshold L3 (S7, S9), the cutting speed of the grindstone 1 is cut from the rapid cutting speed V1. The speed is reduced to the medium cutting speed V2 (S10), and the grindstone 1 is cut at the medium cutting speed V2.

  Further, if the grinding load increases due to the medium cutting at the cutting speed V2 and becomes the load threshold L3 or more and less than the load threshold L4 (S9, S11), the cutting speed of the grindstone 1 is delayed from the medium cutting speed V2. The workpiece is decelerated to a slow cutting speed V3 (S12), and grinding of the workpiece W is continued while cutting the grindstone 1 at the slow cutting speed V3.

  Grinding is started at such a high speed cutting speed V0, and thereafter the grinding load increases from the load threshold L1 to the load threshold L3 through the load threshold L2, and for each load threshold L1 to L3, The grindstone 1 is cut while gradually decelerating to the cutting speeds V1 to V3.

  In addition, when it becomes less than the load threshold L3 during the slow cutting of the grindstone 1 (S9), the cutting speed of the grindstone 1 is increased from the slow cutting speed V3 to the medium cutting speed V2 (S10), etc. If the grinding load is reduced, the cutting speed of the grindstone 1 is increased as the grinding load is reduced.

  If the grinding load increases during grinding at the slow cutting speed V3 and becomes greater than or equal to the load threshold L4 and less than the load threshold L5 (S11, S13), the slow cutting speed V3 to the slow return speed V4. The grinding of the workpiece W is continued while the grindstone 1 is returned by switching to the slow return (S14). Also, if the grinding load becomes less than the load threshold L4 during the grinding with the slow return (S11), the grindstone 1 is slowly cut by switching from the slow return at the slow return speed V4 to the slow cut at the slow cut speed V3. (S12).

  Therefore, if the grinding of the workpiece W proceeds until the grinding load of the grindstone 1 reaches a high load range near the load threshold L4, then the grindstone 1 performs slow cutting and slow return once above and below the load thresholds L3 and L4. Alternatively, the grinding of the final stage of the workpiece W is continued while repeating a plurality of times.

  During this time, the sizing control means 10 reads the dimensions of the workpiece W, and if the sparking time is close to the predetermined finishing accuracy dimension (S4), the grindstone is based on the spark-out command from the sizing control means 10. The feeding means 7 stops the movement of the grindstone 1, and the grindstone 1 performs a spark out for grinding the workpiece W at the stop position (S21). Then, when the workpiece W has a finished dimension due to the spark-out, the grinding is finished (S22).

  If the grinding load is greater than or equal to the load threshold value L5 and less than the load threshold value L6 during grinding with slow return (S13, S15), grinding is continued while returning the grindstone 1 at the intermediate return speed V5 (S16), and further If the grinding load is greater than or equal to the load threshold L6 and less than the load threshold L7 during the middle return (S15, S17), the grinding is continued while returning the grindstone 1 at the fast return speed V6 (S18).

  If the grinding load is equal to or greater than the load threshold L7 (S17), emergency return is performed at the emergency return speed V7 (full speed) (S19), and grinding is stopped (S20). Then, after the grinding is stopped, appropriate measures are taken such as performing dressing of the grindstone 1 to restore the sharpness of the grindstone 1.

  After starting the high-speed cutting of the grindstone 1 at the high-speed cutting speed V0 in this way, the grinding load is changed from the load threshold L1 to the load threshold L3 through the load threshold L2 while monitoring the fluctuation of the grinding load of the grindstone 1. As the speed increases, the cutting speed of the grindstone 1 is decelerated sequentially from high speed cutting to early cutting, from early cutting to middle cutting, and from middle cutting to slow cutting.

  Therefore, by adopting such a grinding method, it is possible to grind the workpiece W by the grindstone 1 so that the cutting speed of the grindstone 1 and the speed at which the workpiece W is ground by the grindstone 1 substantially coincide. The workpiece W can be efficiently ground in a state where a moderately high load with high grinding efficiency is applied to the grindstone 1.

  In particular, when the grindstone 1 is cut at a high speed, the speed at which the workpiece W is ground by the grindstone 1 and the cutting speed of the grindstone 1 do not match as the grinding progresses, and a grinding residue is generated on the workpiece W side. 1 grinding load rises abnormally. As a result, if grinding is continued in a high-speed cutting state, the load applied to the workpiece W becomes excessive, causing problems such as the workpiece W breaking. However, since the cutting speed of the grindstone 1 is reduced as the grinding load increases while monitoring the grinding load, it is possible to prevent an excessive load from being applied to the workpiece W.

  Further, at the final stage of grinding the workpiece W, the grinding load is increased to the load threshold L3 or more and the grinding wheel 1 is switched to the slow return if the grinding load increases to L4 during the grinding with the slow cutting. Grinding the workpiece W under high load while repeating slow return. Therefore, the grinding load of the grindstone 1 does not continue to increase and an excessive load is not applied to the workpiece W, and grinding can be continued with a moderately high load with high grinding efficiency.

  FIG. 6 shows changes in the grinding load and dimensions of the workpiece W when the workpiece W is actually ground. A is a grinding load curve showing a change in grinding load from the start of grinding to the end of spark out in the present invention, and B is a dimension curve showing a change in the size of the workpiece W in that case. A1 is a grinding load curve in the case of conventional normal grinding, and B1 is a dimensional curve showing a change in the dimension of the workpiece W in that case.

  In conventional normal grinding, in order to avoid overloading, grinding is performed while controlling the rough grinding feed, intermediate finish grinding feed, finish grinding feed and the cutting speed of the grinding stone 1 according to the cutting feed amount of the grinding stone 1. As shown in the grinding load curve A1, grinding must be performed at a slow cutting speed, and the grinding load of the grindstone 1 increases with the progress of grinding, but the gradient is gentle. Therefore, conventionally, since the workpiece W is ground in a low load state in which the grinding stone 1 is likely to be clogged and the grinding efficiency cannot be sufficiently exhibited, the grinding cycle of the workpiece W becomes long, the grinding efficiency is poor, and the grinding temperature is low. There was a problem of rising.

  On the other hand, in the present invention, as shown in the grinding load curve A in FIG. 6, each time the grinding load reaches a predetermined load threshold based on the grinding load of the grindstone 1, high speed cutting, fast cutting, medium cutting, The grindstone 1 is gradually decelerated in the order of slow cutting, and cutting, slow cutting, and slow returning are repeated several times to shift to spark out.

  Therefore, since the self-generated action of the abrasive grains can be promoted by increasing the grinding load of the grindstone 1, the workpiece W can be ground in a short time with high grinding efficiency, and the grinding can be efficiently performed with a grinding cycle shorter than conventional normal grinding. it can. As a result, it was found that the grinding time in the present invention can be shortened to about 2/3 as compared with the conventional normal grinding, and efficient grinding is possible. Further, in the present invention, since the grinding is efficiently performed with a high load with high grinding efficiency, an increase in the grinding temperature can be prevented as compared with the case of the normal grinding in which the grinding is performed with a low grinding load.

  7-10 illustrate a second embodiment of the present invention. The grindstone cutting back control means 11 of this embodiment has a speed limit execution function. As shown in FIG. 7, the grinding load measuring means 13, the speed setting means 14, and the speed control means 15 are the same as those of the first embodiment. In addition, a speed limit execution means 14A is provided.

  When the grinding load of the grindstone 1 exceeds the load threshold LA for executing the speed limitation, the speed limiting execution means 14A is capable of cutting the grinding wheel 1 even if the grinding load subsequently drops below the slow cutting load threshold L3. Has a function of executing a speed limit to limit the speed to a limit cut speed Vα (= 0.03 mm / min) slower than the slow cut speed V3 (= 0.05 mm / min).

  The speed table is configured as shown in FIG. 9, and the grinding load is gradually reduced to the cutting speeds V1 to V3 of the grindstone 1 as the grinding load increases stepwise to the load thresholds L1 to L3. The grindstone 1 is returned at the slow return speed V4 (= −0.05 mm / min) when the speed rises to the load threshold L4 at the time of slow return, and the limit cutting speed Vα ( = 0.03 mm / min), and grinding is interrupted when the load threshold LX at the time of grinding interruption is increased.

  In the in-feed grinding of the workpiece W, as shown in FIG. 8, it is determined whether or not the grinding load is equal to or greater than the load threshold LX when grinding is stopped (S23). If the grinding load is equal to or greater than the load threshold LX, grinding is stopped (S24). ). When the grinding load is less than the load threshold LX, it is checked whether the grinding load has exceeded the load threshold LA when the speed limit is executed until that time (S25). Even if it is less than the threshold value L4 (S26), the grindstone 1 is limited to the limited cutting speed Vα (= 0.03 mm / min) (S27). If the load threshold LA has not been exceeded, the grinding load is compared with the load threshold L1 (S28), and if it is less than the load threshold L1, the cutting speed V0 for high speed cutting is set (S29). When the grinding load is greater than or equal to the load threshold L1, when compared with the load threshold L2, when the grinding load is less than the load threshold L2 (S30), the rapid cutting speed V1 is set (S31).

  Similarly, when the grinding load is equal to or greater than the load threshold L2, if the grinding load is less than the load threshold L3 compared to the load threshold L3 (S32), the medium cutting depth V2 is set (S33). When the grinding load is equal to or greater than the load threshold L3, if it is less than the load threshold L4 compared to the load threshold L4 (S34), the slow cutting speed V3 is set (S35). When the grinding load during grinding with slow cutting becomes equal to or greater than the load threshold L4, the grindstone 1 is returned at the slow return speed V4 (S36), and the grinding load is reduced by the slow return of the grindstone 1.

  During grinding with slow return, the grinding load of the grindstone 1 is compared with the load threshold LA at the time of speed limit execution (S37), and if it is less than the load threshold LA, the process returns to step S2. However, if the grinding load temporarily rises above the load threshold LA at the time of speed limit execution due to some cause without lowering the grinding load during the slow return grinding (S37), the grinding load becomes the load threshold LA. (S38), and the cutting speed limiting function of the speed limiting execution means 14A is activated.

  After that, if the cause of the temporary increase in the grinding load is eliminated, the grinding load is rapidly reduced by the slow return of the grindstone 1 at the slow return speed V4. However, since the grinding load once exceeds the load threshold LX (S25), even if the grinding load of the grindstone 1 becomes less than the load threshold L4 at the time of slow cutting (S26), the cutting speed of the speed control means 14A The limiting function is activated, and the subsequent slow cutting speed Vα (= 0.03 mm / min) for the subsequent cutting of the grindstone 1 without the original slow cutting speed V3 (= 0.05 mm / min). (S27).

  Therefore, the grindstone 1 and the workpiece W do not repeat contact and separation. If the speed limit execution function is not provided, when the grinding load decreases to less than the load threshold L3 during grinding of the workpiece W with the slow return (S34), the slow cut speed V3 is switched from the slow return to the slow cut. The grindstone 1 is cut at (= 0.05 mm / min). Therefore, if the cutting speed of the grindstone 1 is controlled in accordance with the increase or decrease of the grinding load, the grindstone 1 moves back and forth violently at a fast cutting speed and a fast return speed, and the grindstone 1 and the workpiece W are brought into contact with and separated from each other. Repeatedly, the grinding of the workpiece W may not proceed.

  However, even if the grinding load decreases to less than the load threshold L3 due to the slow return of the grindstone 1, the grindstone 1 is not cut immediately at a fast cutting speed V3 (= 0.05 mm / min), but the limited cutting speed. Cutting is performed slowly at a slow speed of Vα (= 0.03 mm / min), and a sharp increase in the grinding load of the grindstone 1 can be prevented by switching from slow return to slow cut. There is no such thing as violent repetition. Therefore, as shown in the grinding load curve in FIG. 10, the subsequent change in the grinding load becomes stable, and the workpiece W can be efficiently ground.

  In this embodiment, after exceeding the load threshold LA at the time of speed limit execution, control is performed so that the grindstone 1 is not cut at a speed faster than the limit cut speed Vα even if the grinding load is reduced. However, even when the grindstone 1 is returned, there is a case in which after the limit return speed Vβ is set and the grinding load exceeds a certain load threshold value LB, the grinding load subsequently decreases to near the upper side of the load threshold value L4. Alternatively, the return speed may not be higher than the limit return speed Vβ.

  11-13 illustrate a third embodiment of the present invention. As shown in FIG. 11, the grindstone cutting back control means 11 of this embodiment has a table selection means 16 that can appropriately select a speed table stored in the speed setting means 14, and is selected by the table selection means 16. The speed control means 15 is configured to control the grindstone feeding means 7 according to the table.

  Tables stored by the speed setting means 14 include, for example, a first speed table T1 shown in FIG. 12 and a second speed table T2 shown in FIG. The table selection means 16 can select the first speed table T1 and the second speed table T2 individually, and can select a combined table obtained by combining a part of both speed tables T1 and T2.

  The combination table selects before and after the first speed table T1 and the second speed table T2, and changes the speed table when changing from one speed table T1 or speed table T2 to the other speed table T2 or speed table T1. The load is appropriately set as a load threshold, and the speed table change load is used to change the front and back of both speed tables T1 and T2 and combine them, and from one speed table T1 or speed table T2 to the other speed table T2 or speed table. It is one speed table comprised so that it may switch to T1.

  For example, when the first speed table T1 is set to the front and the second speed table T2 is set to the back, and the load threshold L3 is set as the speed table change load, the first speed table T1 up to the load threshold L3 is set. One speed table combining the first half and the second half of the second speed table T2 after the load threshold L3 can be configured.

  Accordingly, during in-feed grinding, the grindstone cutting back control means 11 controls the cutting speed of the grindstone 1 according to the coupling table by the speed control means 15 while monitoring changes in the grinding load. For example, the first half of grinding is controlled according to the first speed table T1, and when the grinding load is less than the load threshold L3, the grinding wheel 1 is rotated at the slow cutting speed V3 (= 0.05 mm / min) of the first speed table T1. Make a slow cut. And if it becomes more than the load threshold value L3, it will change from 1st speed table T1 to 2nd speed table T2, and according to this 2nd speed table T2, the return speed V3 (= -0.05 mm / min) of the grindstone 1 is changed. Perform a slow return. Other configurations, controls, and the like are the same as those in each embodiment.

  In this way, a combined table can be configured by selectively combining a part of the first speed table T1 and the second speed table T2, and work can be performed while using a small number of speed tables T1 and T2. It is possible to grind under the optimum conditions for the material of W and others.

  There may be three or more types of speed tables, and there may be a plurality of types of speed table changing loads. Further, in addition to changing the table according to the speed table changing load, a plurality of speed tables may be changed based on the cutting time, the cutting amount, the removal amount read from the sizing device or the like.

  FIG. 14 illustrates a fourth embodiment of the present invention. When the workpiece W is in-feed ground with the grindstone 1, the grinding load during grinding may rise and fall according to the conditions at that time. Accordingly, as illustrated in FIG. 14 as an example of the speed table, it is possible to select whether to use a load threshold value for the rising phase or the decreasing phase of the grinding load in the speed table (ON is selected, OFF is not selected). In addition, necessary conditions may be selected as appropriate according to grinding conditions.

  In the case of the speed table of FIG. 14, there are control elements of high speed cutting, fast cutting, middle cutting, slow cutting, slow returning, middle returning, fast returning, and emergency returning. , And can be appropriately selected according to the decline phase. For example, in the rising phase of the grinding load, medium cutting, slow return and medium returning are not selected, and in the decreasing phase, slow cutting is not selected.

  In actual in-feed grinding, whether the grinding at that time is in the rising phase or the falling phase is determined by determining a judgment time of the past several seconds and obtaining a moving average of the grinding load during the judgment time. You may judge by.

  15 and 16 illustrate a fifth embodiment of the present invention. As shown in FIG. 15, the grinding wheel cutting / returning control means 11 sets a grinding load measuring means 13 for measuring a grinding load of the grinding wheel 1 during grinding, and sets a cutting speed and a returning speed of the grinding stone 1 for each load threshold. The speed setting means 14 for performing, the time setting means 17 for setting the acceleration / deceleration time at the time of changing the cutting speed and switching between cutting and returning, and the grinding load during grinding and the load threshold value are compared, and the grinding load The grindstone feeding means 7 is controlled to be cut and returned to the cutting speed and return speed set by the speed setting means 14 in accordance with the increase / decrease of the speed, and when the cutting speed is changed, switching between cutting and returning is performed. And a speed control means 15 that gradually changes the speed in one direction with the acceleration / deceleration time T set by the time setting means 17.

  In the grindstone cutting / returning control means 11 having such a configuration, if the acceleration / deceleration time T is set in advance by the time setting means 17, the cutting speed is changed or the switching is made between cutting and returning. In addition, since a rapid change in speed can be prevented, there is no problem that the grinding load temporarily decreases, and the workpiece W can be efficiently ground with a high grinding load.

  For example, when decelerating from a high-speed cutting with a cutting speed V0 to a fast cutting with a cutting speed V1, the cutting speed V1 is changed from the cutting speed V0 with the acceleration / deceleration time T as shown by the solid line in FIG. Since the speed is gradually decelerated, it is possible to suppress a change in grinding load by suppressing a rapid change in speed as compared with a case where switching is performed immediately as indicated by a dotted line.

  Also, when switching from slow cutting at the cutting speed V3 to slow returning at the returning speed V4, the cutting speed V3 is changed to the returning speed V4 at the acceleration / deceleration time T as shown by the solid line in FIG. Since the switching is performed gradually, it is possible to suppress a change in the grinding load by suppressing a rapid speed change in the reverse direction as compared with a case where the switching is performed immediately as indicated by a dotted line.

  The acceleration / deceleration time T can be appropriately set according to the material of the workpiece W or the like. In addition to making the acceleration / deceleration time T variable, the speed control means 15 performs acceleration / deceleration gradually or stepwise according to a predetermined acceleration / deceleration characteristic when changing the cutting speed or switching between cutting and returning. You may make it do.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to this embodiment, A various change is possible. For example, it is desirable that the number of load thresholds of the grinding load is large. Therefore, it is possible to increase the number of load thresholds innumerably, and by continuously increasing the number of load thresholds, continuously variable transmission that continuously reduces the cutting speed of the grindstone 1 as the grinding load increases. Is possible.

  In the embodiment, the work W made of a hard and brittle material is illustrated. However, the present invention is not limited to the hard and brittle material, and general surface grinding of the work W made of various materials can be similarly performed.

  Although the rotational load torque of the grindstone shaft 5 is exemplified as the grinding load, the grinding load may be determined by a change in the current and power of the grindstone driving means 6 or a change in the load applied to the grindstone driving means 6. The grinding load may be determined based on changes in torque, current, power, and load of the driving unit 4. Further, in the case of the surface grinding machine 2 having no workpiece driving mechanism, the grinding load may be determined from the load applied to the workpiece W. Further, the judgment is made by combining two or more related elements related to the change of the grinding load, such as combining the change of the current, power or load of the grindstone driving means 6 with the change of the current, power or load of the work driving means 4. You may do it.

  In the first and second embodiments, the case where the grinding load increases during cutting is described in detail. However, if the grinding load falls below a predetermined load threshold during cutting, the cutting speed is increased. Needless to say, the speed may be controlled. Also in that case, the cutting speed may be accelerated over a predetermined time.

  In addition, when the grinding load accelerates or decelerates the cutting speed based on a predetermined load threshold or switches between cutting and returning, the grinding wheel 1 can be cut and returned based on the predetermined load threshold. It is sufficient, and it is possible to make a determination based on either less than the load threshold or more than the load threshold.

  Fast cutting, early cutting, middle cutting, slow cutting, slow returning, middle returning, fast returning, etc. are merely examples, and may be subdivided more than these, or roughly divided by a small number good. The values of the load threshold value, the cutting speed, and the return speed are merely examples, and are not limited to these.

DESCRIPTION OF SYMBOLS 1 Grinding wheel 2 Surface grinder 3 Rotary table 4 Work drive means 5 Grinding wheel shaft 7 Grinding wheel feeding means 10 Fixed dimension control means 11 Grinding wheel cutting back control means 12 Dimension measuring means 13 Grinding load measuring means 14 Speed setting means 14A Speed limit executing means 15 Speed control means 16 Table selection means 17 Time setting means

Claims (7)

  A surface grinding method for a workpiece characterized in that when a workpiece is surface ground with a grindstone, the cutting speed of the grindstone is reduced as the grinding load increases while monitoring the grinding load.   When grinding a workpiece with a grindstone, while monitoring the grinding load, the cutting speed of the grindstone is reduced when the grinding load increases, and the cutting speed is increased when the grinding load decreases. Surface grinding method for workpieces.   Corresponding to each load threshold of the grinding load, each cutting speed is set so that the cutting speed of the grindstone becomes slower as the grinding load becomes larger, and after starting grinding at a predetermined speed, the grinding load is predetermined. The surface grinding method for a workpiece according to claim 1, wherein the grinding wheel is decelerated / accelerated to a corresponding cutting speed each time the load threshold is increased / decreased.   A return load threshold higher than a maximum load threshold at the time of cutting of the grindstone is set, and grinding is performed while returning the grindstone at a predetermined return speed when the grinding load exceeds the return load threshold. Item 4. A method for surface grinding a workpiece according to any one of Items 1 to 3.   The surface grinding method for a workpiece according to any one of claims 1 to 4, wherein cutting and returning of the grindstone are repeated before sparking out.   When the grinding load exceeds the load threshold for speed limit execution, the grindstone is cut at a limited cutting speed that is slower than the predetermined cutting speed even if the grinding load subsequently drops to the load threshold for the predetermined cutting speed. The method for surface grinding of a workpiece according to any one of claims 1 to 5, wherein the workpiece is not faster than a cutting speed and a limit cutting speed.   A surface grinding machine for in-feed grinding a workpiece with a grindstone, wherein a grinding load measuring means for measuring a grinding load of a grinding wheel during grinding, and a plurality of grinding wheel cutting speeds corresponding to a plurality of load thresholds are set. While comparing the speed setting means with the grinding load during grinding and the load threshold, each load threshold is set to each load threshold so that the cutting speed of the grindstone decreases and increases as the grinding load increases and decreases. A surface grinding machine comprising speed control means for increasing or decreasing the speed of a grindstone at a corresponding cutting speed.

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