KR102573501B1 - Surface grinding method for workpiece and surface grinder - Google Patents

Abstract

The present invention enables efficient grinding of hard and brittle materials, difficult-to-cut materials, and other workpieces under an appropriately high load.
When surface 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. Corresponding to each of the plurality of load thresholds of the grinding load, each cutting speed at which the cutting speed of the grindstone becomes slower as the grinding load increases is set, grinding is started at a predetermined speed, and then the grinding load rises to the predetermined load threshold. ·Decelerates/increases the grindstone at the cutting speed corresponding to each decrease.

Description

Surface grinding method and surface grinding machine of work {SURFACE GRINDING METHOD FOR WORKPIECE AND SURFACE GRINDER}

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

In a surface grinding machine equipped with a cup-shaped grindstone, when grinding a workpiece made of a hard and brittle material such as a silicon wafer used for manufacturing semiconductor elements, the grindstone at the tip of the grindstone shaft is adjusted while monitoring the load current of the grindstone shaft drive motor. Infeed grinding of the workpiece on the rotary table is performed by cutting at a cutting speed of , and when the load current of the grindstone shaft driving motor exceeds a predetermined threshold value due to clogging of the grindstone, the grindstone is retracted to stop grinding, and then the grindstone is removed. By incising again and bringing it into contact with the workpiece, the spontaneous growth of the grindstone is promoted (Patent Document 1).

Patent Document 1: Japanese Unexamined Patent Publication No. 2006-35406

In such a conventional grinding method, while cutting the grindstone at a predetermined cutting speed, when clogging occurs in the grindstone during grinding, the grindstone is temporarily retracted to stop grinding, and then the grindstone is cut again to promote the growth of the grindstone. are making it For this reason, it was not possible to grind the workpiece under a high load state with high grinding efficiency of the grindstone, and the grinding cycle became long, making it difficult to grind the workpiece efficiently in a short time.

In addition, even in conventional grinding methods other than the grinding method of Patent Document 1, a grinding method in which a grindstone is cut into a workpiece at a constant cutting speed during grinding, rough grinding feed, semi-finish according to the cutting feed amount of the grindstone ) There is a grinding method (hereinafter referred to as a normal grinding method) in which grinding is performed while the feed speed is sequentially shifted in the deceleration direction with grinding feed and finish grinding feed.

However, in the former grinding method, the balance between the abrasion amount of the abrasive stone, the amount of workpiece removal, and the amount of cut of the abrasive stone may be lost during grinding, and the grinding load may increase rapidly or only the abrasive stone may be worn, and the grinding efficiency of the abrasive stone is high. It was difficult to efficiently and stably grind the workpiece in this condition.

In addition, even in the latter grinding method, it was not possible to grind the workpiece efficiently and stably under a high load condition with good grinding efficiency of the grindstone for the following reasons. In particular, when grinding workpieces made of hard and brittle materials with high hardness and brittleness, grinding is performed while changing the feed speed of the grindstone so as not to become overloaded by cutting the grindstone, so it is necessary to slow the cutting speed of the grindstone and grind for a long time. .

However, in the case of such a hard and brittle material, grains change on the surface of the abrasive stone occurs several times during grinding, and the grinding load varies greatly up and down. This is because the sharpness of the abrasive stone is bad before spontaneous generation, but once the spontaneous generation of the abrasive stone occurs, the cutting edge of the abrasive stone increases and the sharpness improves rapidly. As a result, the coefficient of friction between the grindstone and the workpiece changes, and the grinding load varies greatly up and down, so efficient and stable grinding cannot be performed in a short time at a high load with good grinding efficiency.

In addition, in many cases, the distance between the grindstone axis and the rotary table in the axial direction is reduced due to rapid thermal displacement of the grindstone, workpiece, and machine due to an increase in frictional heat during autogenous growth. This is equivalent to an increase in the cutting speed of the grindstone and becomes a factor in a sharp increase in the grinding load. And, if the grinding load rises too much, there is a risk that the abnormal grinding load is detected and the machine terminates processing, or in the worst case, the grindstone and the workpiece are damaged, or the machine is damaged.

In view of these conventional problems, the present invention can efficiently grind hard and brittle materials and other workpieces at an appropriately high load, and at the same time, prevent damage to the workpiece, grindstone, and consequently the machine due to a sudden increase in grinding load. It is an object of the present invention to provide a method for surface grinding of a workpiece and a surface grinding machine capable of reducing grinding stone wear.

In the method for surface grinding a workpiece according to the present invention, when performing surface grinding of a workpiece with a grindstone, the cutting speed of the grindstone is reduced as the grinding load increases while monitoring the grinding load.

In another method of surface grinding a workpiece according to the present invention, when surface 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 when the grinding load decreases to increase the cutting speed.

In addition, corresponding to the plurality of load thresholds 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 grinding is started at a predetermined speed, the grinding load is reduced to a predetermined load threshold. It is also possible to decelerate or increase the cutting speed corresponding to the grindstone whenever it rises or falls.

It is also possible to set a return load threshold higher than the maximum load threshold at the time of cutting the grindstone, and return the grindstone at a predetermined return speed when the grinding load exceeds the return load threshold. You may repeat the infeed and return of the grinding stone before sparking out.

In addition, when the grinding load exceeds the load threshold for speed limit execution, even if the grinding load subsequently decreases to the load threshold of the predetermined cutting speed, the grindstone is cut at a limiting cutting speed slower than the predetermined cutting speed, and the grinding stone is cut at a limit cutting speed or higher. It is better not to do it quickly.

A surface grinding machine according to the present invention is a surface grinding machine that in-feeds grinds a workpiece with a grindstone, and includes a grinding load measuring means for measuring a grinding load of the grindstone during grinding, and a plurality of grindstone cuts corresponding to a plurality of load thresholds. Cutting speed corresponding to each load threshold based on each load threshold so that the cutting speed of the grindstone decelerates and increases according to the rise and fall of the grinding load while comparing the speed setting means with set speed and the grinding load and load threshold during grinding It is provided with a speed control means for increasing or decreasing the grindstone.

According to the present invention, it is possible to efficiently grind hard and brittle materials and other workpieces under an appropriately high load, and at the same time, it is possible to prevent damage to the workpiece, grindstone, and/or machine due to a sudden increase in grinding load, etc. There are advantages to doing less.

1 is a front view of a surface grinding machine showing a first embodiment of the present invention.
Fig. 2 is a perspective view of the main part;
Fig. 3 is a block diagram of the same control system;
4 is a dynamic speed table;
Fig. 5 is a flowchart of the same grinding operation;
Fig. 6 is a diagram showing changes in the grinding load and the like.
Fig. 7 is a block diagram of a control system showing a second embodiment of the present invention;
Fig. 8 is a flowchart of the same grinding operation;
9 is a speed table;
Fig. 10 is a diagram showing changes in copper grinding load;
Fig. 11 is a block diagram of a control system showing a third embodiment of the present invention.
Fig. 12 is the same first speed table;
Fig. 13 is a second speed table;
Fig. 14 is a speed table showing a fourth embodiment of the present invention;
Fig. 15 is a block diagram showing a fifth embodiment of the present invention;
Fig. 16 is a waveform diagram of dynamic speed change;

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is detailed based on drawing.

1 to 6 illustrate a first embodiment of the present invention. When performing in-feed grinding of a workpiece W made of a hard brittle material such as a sapphire wafer with the cup-shaped grindstone 1, a flat grinding machine 2 as shown in FIGS. 1 and 2 is used. As shown in Figs. 1 and 2, this surface grinding machine 2 includes a rotary table 3 to which a workpiece W is detachably attached to the upper surface, and the rotary table 3 is rotated around the axis in the vertical direction. A work driving means 4 such as a motor that rotates in the direction of the arrow a, a grindstone shaft 5 arranged so as to be movable up and down on the rotary table 3, and a grindstone shaft 5 around the shaft center in the vertical direction A grindstone drive means 6 such as a motor that rotates in the direction of arrow b and a workpiece W on the rotary table 3 is detachably mounted to the lower end of the grindstone shaft 5 and is rotated in the direction of arrow b It is provided with a grindstone 1 for surface grinding, and a grindstone transfer means 7 for conveying the grindstone 1 in the vertical cutting direction (c) and return direction (d) via the grindstone axis (5). Further, the rotational directions of the rotary table 3 and the grindstone 1 are arbitrary.

3 shows a control system that controls the grinding operation of the surface grinding machine 2. This control system includes, for example, a sizing control means 10 and a grindstone infeed return control means 11 in addition to the NC control means 9 that controls the general grinding operation related to the infeed grinding of the surface grinding machine 2. have

The sizing control means 10 measures the size of the workpiece W during grinding with the size measurement means 12, and issues a spark-out command to the grindstone transfer means 7 when a predetermined spark-out time arrives, The workpiece W is controlled to be finished with a predetermined dimensional accuracy.

Further, when there is a spark-out command, the grindstone transfer means 7 stops the feed of the grindstone shaft 5 so that the grindstone 1 continues machining the workpiece W at that position. If there is no sizing control means 10, a spark-out command may be issued when a predetermined cutting amount is reached or when a predetermined time elapses from the start of grinding the workpiece W.

The grindstone infeed return control means 11 monitors the grinding load during grinding of the workpiece W so that the grindstone 1 grinds the workpiece W efficiently under an appropriately high load with high grinding efficiency. , For controlling the return, a function of decelerating the cutting speed of the grindstone 1 as the grinding load rises, and a function of repeating the cutting and return of the grindstone 1 when the grinding load rises to near the upper limit; It has a function of increasing the speed of the grindstone 1 according to a decrease in the grinding load.

Specifically, the grindstone cutting return control means 11 includes a grinding load measurement means 13 that measures the grinding load of the grindstone 1 during grinding, and sets the cutting speed and return speed of the grindstone 1 for each load threshold. The actual grinding load during grinding is compared with the load threshold value, and the grindstone conveying means 7 is moved at the cutting speed and return speed set by the speed setting means 14 according to the increase or decrease of the grinding load. It has speed control means 15 for controlling.

The grinding load measuring means 13 measures the grinding load of the grindstone 1 during grinding by a change in current, electric power or torque flowing through the grindstone driving means 6. The speed setting means 14 has a speed table as shown in FIG. 4 . The speed table includes load thresholds L1 to L7 (N m) in which the grinding load increases step by step for each operation of high-speed infeed, fast infeed, medium infeed, slow infeed, slow return, intermediate return, fast return, and emergency return; Corresponding to the respective load threshold values L1 to L7 (N·m), cutting speeds V0 to V7 (mm/min) that are gradually increased or decreased are set.

The high-speed cutting is cutting when the grindstone 1 contacts the workpiece W to start grinding, and the high-speed cutting speed V0 is set to 0.5 (mm/min). Fast infeed with fast infeed speed V1 = 0.3 (mm/min) for load threshold L1, medium infeed with medium infeed speed V2 = 0.1 (mm/min) for load threshold L2, slow infeed with load threshold L3 Slow infeed speed V3 = 0.05 (mm/min) is set respectively.

Also, slow return is slow return speed V4 = -0.05 (mm/min) for load threshold L4, medium return is medium return speed V5 = -0.1 (mm/min) for load threshold L5, and fast return is load threshold L5. Regarding L6, the fast return speed V6 = -0.3 (mm/min) is set respectively. Emergency return is set at return speed V7 (full speed) with respect to load threshold L7.

In addition, since the return is in the opposite direction to the incision, in the description of the slow return speed V4 or the like, - is added to the numerical value to indicate that it proceeds in the opposite direction.

Each of the load thresholds L1 to L7 has a sequentially increasing relationship from the load threshold L1 to the load threshold L7, as illustrated for the load thresholds L1 to L4 in FIG. 6 . The cutting speed V0 to V3 and return speed V4 to V7 of the grindstone 1 corresponding to each load threshold value L1 to L7 of the grinding load are the material and size of the workpiece W, the grindstone 1, and the surface grinding machine 2 Considering the combination of the above, it is determined in advance by experiments or the like so that the grindstone 1 can efficiently grind the workpiece W under an appropriately high load state with high grinding efficiency.

Therefore, high-speed infeed, fast infeed, medium infeed, and slow infeed are decelerated in the infeed direction step by step at the cutting speed V1 to V3 as the grinding load increases stepwise to the load threshold values L1 to L3. In addition, slow return, intermediate return, fast return, and emergency return are designed to increase the speed in the return direction step by step at return speed V4 to V7 as the grinding load increases step by step to load threshold values L4 to L7. Since the return speed V4 to V7 of the grindstone 1 moves in the opposite direction to the cutting direction, it can be said that the grindstone 1 decelerates step by step from slow return to emergency return when the grindstone 1 takes the cutting direction as a reference. can

In addition, if there is a standard speed table corresponding to the standard workpiece W, the numerical value of the standard speed table is read according to the difference in the material of the workpiece W, and the control is performed while correcting it. good night.

The load threshold L3 at slow infeed and the load threshold L4 at slow return are higher than the load threshold L4 at slow return, but the slow infeed and slow return are repeated multiple times before sparking out after exceeding the load threshold L3. In this case, for example, when the grinding load is greater than or equal to the load threshold L3 and less than the load threshold L4, the grindstone 1 is slowly inserted, and when the load threshold L4 or more, the grindstone 1 is slowly returned, based on the load threshold L4. Switch between slow infeed and slow return in (1).

Next, the grinding method of the workpiece|work W is demonstrated referring the flowchart of FIG. The 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 grinding machine 2 starts the grinding operation of infeed grinding (S1), first, until just before the grindstone 1 comes into contact with the work W, the grindstone conveyance means 7 operates at a high speed faster than the high-speed cutting speed V0. The grindstone shaft 5 is fed in the infeed direction at the feed rate. On the other hand, the dimensions of the workpiece W are measured by the dimension measuring means 12 (S2), the grinding load is measured by the grinding load measuring means 13 (S3), and the sizing control means 10 sparks out. It is determined whether it is time or not (S4).

Immediately after the start of the grinding operation, since it is not the spark-out time yet (S4), it is determined whether or not the grinding load is less than the load threshold value L1 of fast infeed (S5), and the feed rate of the grindstone shaft 5 is determined from the high feed rate. It decelerates to the high-speed cutting speed V0, and the grindstone 1 starts grinding the work W at the high-speed cutting speed V0 (S6).

Until the grindstone 1 contacts the workpiece W, the grindstone shaft 5 is fed at a high feed rate faster than the high feed rate V0, and the grindstone 1 moves at a high feed rate immediately before contacting the workpiece W. By decelerating to V0, it is possible to shorten the air cut time and efficiently transfer to grinding of the workpiece W.

When the grindstone 1 contacts the work W and starts grinding, the grinding load applied to the grindstone shaft 5 increases, but the grindstone 1 is cut at the high cutting speed V0 while the grinding load is less than the load threshold L1. Do (S6). And, when the grinding load rises due to the high-speed infeed by the high-speed infeed speed V0 and becomes more than the load threshold L1 and less than the load threshold L2 (S5, S7), the infeed speed of the grindstone 1 is changed from the high infeed speed V0 to the fast infeed speed. It decelerates to V1 (S8), and grinds the workpiece W while cutting the grindstone 1 at the fast cutting speed V1.

When the grinding load rises due to the fast infeed by the fast infeed speed V1 and becomes more than the load threshold L2 and less than the load threshold L3 (S7, S9), the infeed speed of the grindstone 1 is changed from the fast infeed speed V1 to the middle of the medium infeed. It decelerates at the speed V2 (S10), and cuts the grindstone 1 at the intermediate cutting speed V2.

In addition, when the grinding load is increased by the intermediate infeed by the infeed speed V2 and becomes more than the load threshold L3 and less than the load threshold L4 (S9, S11), the infeed speed of the grindstone 1 is changed from the medium infeed speed V2 to the slow infeed of the slow infeed. It decelerates at the speed V3 (S12), and continues grinding the workpiece W while cutting the grindstone 1 at the slow cutting speed V3.

Grinding is started at such a fast cutting-in speed V0, and then, while the grinding load rises from the load threshold L1 through the load threshold L2 to the load threshold L3 or higher, for each load threshold L1 to L3, the grindstone 1 is cut. It cuts while decelerating step by step at the cutting speed V1 to V3.

In addition, when the load threshold L3 is less than the load threshold L3 during slow cutting of the grindstone 1 (S9), the cutting speed of the grindstone 1 is increased from the slow cutting speed V3 to the intermediate cutting speed V2 (S10), etc., the grinding load is reduced , the cutting speed of the grindstone 1 is increased according to the decrease in the grinding load.

When the grinding load rises during grinding by the slow infeed speed V3 and becomes more than the load threshold L4 and less than the load threshold L5 (S11, S13), switching from slow infeed by the slow infeed speed V3 to slow return by the slow return speed V4 Grinding of the work W is continued while returning the grindstone 1 (S14). In addition, when the grinding load is less than the load threshold L4 during grinding by slow return (S11), the grindstone 1 is cut slowly by switching from slow return by slow return speed V4 to slow infeed by slow cutting 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 around the load threshold L4, thereafter, the grindstone 1 will perform slow infeed and The grinding of the final plate of the work W is continued while repeating the slow return once or a plurality of times.

Even during this time, the sizing control means 10 is reading the dimensions of the workpiece W, and when the spark-out timing comes close to the predetermined finish precision dimension (S4), the spark-out command from the sizing control means 10 Based on this, the grindstone transfer means 7 stops the movement of the grindstone 1, and the grindstone 1 performs spark-out to grind the workpiece W at the stop position (S21). Then, when the workpiece W reaches the finished size due to sparking out, the grinding is finished (S22).

In addition, if the grinding load is greater than the load threshold L5 and less than the load threshold L6 during grinding by slow return (S13, S15), grinding continues while returning the grindstone 1 at the intermediate return speed V5 (S16), and furthermore During the intermediate return, when the grinding load is greater than or equal to the load threshold value L6 and less than the load threshold value L7 (S15, S17), grinding continues while returning the grindstone 1 at a fast return speed V6 (S18).

In addition, when the grinding load exceeds the load threshold value L7 (S17), an 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 such as dressing the grindstone 1 to restore the sharpness of the grindstone 1 are taken.

After starting the high-speed cutting of the grindstone 1 at the high-speed cutting speed V0 in this way, while monitoring the change in the grinding load of the grindstone 1, the grinding load sequentially increases from the load threshold L1 through the load threshold L2 to the load threshold L3. As it rises, the cutting speed of the grindstone 1 is sequentially decelerated from high-speed cutting to fast cutting, from fast cutting to medium cutting, and from medium to slow cutting.

Therefore, by adopting such a grinding method, the workpiece W is ground 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 are approximately the same. This is possible, and the workpiece W can be efficiently ground in a state where an appropriately high load with high grinding efficiency is applied to the grindstone 1.

In particular, when the grindstone 1 is cut at 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 grinding progresses, and the workpiece W Grinding residue is formed on the side and the grinding load of the grindstone 1 rises abnormally. As a result, if grinding is continued in the high-speed cutting state, the load applied to the workpiece W becomes excessive, resulting in problems such as cracking of the workpiece W. However, since the cutting speed of the grindstone 1 is decelerated 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.

Also, at the end of the grinding of the workpiece W, when the grinding load rises to L4 during grinding by slow infeed when the grinding load rises above the load threshold L3, the grindstone 1 is switched to slow return, so slow infeed and The workpiece W is ground under a high load while repeating slow return. Therefore, there is no case where the grinding load of the grindstone 1 continues to rise and an excessive load is applied to the workpiece W, and grinding can be continued at an appropriately high load with high grinding efficiency.

6 shows the change in the grinding load and size of the workpiece W when the workpiece W is actually ground. A is a grinding load curve showing the change in grinding load from the start of grinding to the end of sparking in the case of the present invention, and B is a dimensional curve showing the 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 changes in the dimensions of the workpiece W in that case.

In the conventional normal grinding, grinding is performed while controlling the cutting speed of the grindstone 1 with rough grinding feed, heavy finish grinding feed, and finish grinding feed according to the cutting feed amount of the grindstone 1 so as not to overload, so the grinding in FIG. As shown by the load curve A1, it is inevitable to grind at a slow cutting speed, and the grinding load of the grindstone 1 rises with the progress of grinding, but the gradient is gentle. Therefore, in the prior art, since the workpiece W is ground under a low load condition where the grindstone 1 is prone to clogging and the grinding efficiency cannot be sufficiently exhibited, the grinding cycle of the workpiece W becomes long and the grinding efficiency is poor. There was a problem such as an increase in the grinding temperature.

On the other hand, in the present invention, as shown by the grinding load curve A of FIG. 6, whenever the grinding load reaches a predetermined load threshold based on the grinding load of the grindstone 1, high-speed cutting, fast cutting, medium cutting, and slow cutting In the order of infeed, the grindstone 1 is incised while decelerating sequentially, and the slow infeed and slow return are repeated several times to shift to spark-out.

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

7 to 10 illustrate a second embodiment of the present invention. The grindstone infeed return control means 11 of this embodiment has a speed limit execution function, and as shown in Fig. 7, the same grinding load measuring means 13, speed setting means 14, and speed control as in the first embodiment. In addition to the means 15, a speed limiting execution means 14A is provided.

When the grinding load of the grindstone 1 exceeds the load threshold LA of speed limit execution, this speed limit execution means 14A, even if the grinding load is subsequently lowered to less than the load threshold L3 of slow infeed, of the grindstone 1 It has the function of executing speed limit which limits the infeed speed to the limit infeed speed Vα (= 0.03 mm/min) slower than the slow infeed speed V3 (= 0.05 mm/min).

The speed table is configured as shown in Fig. 9, and as the grinding load increases stepwise to the load threshold values L1 to L3, the grindstone 1 is decelerated stepwise to the cutting speed V1 to V3, and the grinding load is slow at the time of return. When the load threshold L4 is raised, the grindstone 1 returns to the slow return speed V4 (= -0.05 mm/min), and when the load threshold LA at the time of speed limit execution is raised, the limit cutting speed Vα (= 0.03 mm/min ), and grinding is stopped when it rises to the load threshold LX at the time of stopping grinding.

At the time of infeed grinding of the work W, as shown in Fig. 8, it is determined whether or not the grinding load is equal to or greater than the load threshold value LX at the time of stopping grinding (S23), and if it is equal to or greater than the load threshold value LX, grinding is stopped (S24). . In addition, when the grinding load is less than the load threshold LX, it is checked whether or not the grinding load has ever exceeded the load threshold LA at the time of speed limit execution (S25), and even if the grinding load is less than the load threshold L4 (S26 ), the grindstone 1 is limited to the limit cutting speed Vα (= 0.03 mm/min) (S27). If there is no case where it becomes more than the load threshold LA, the grinding load is compared with the load threshold L1 (S28), and if it is less than the load threshold L1, it is set as the cutting speed V0 of high-speed cutting (S29). And when grinding load is more than load threshold value L1, compared with load threshold value L2, when it is less than load threshold value L2 (S30), it is set as cutting speed V1 of fast incision (S31).

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

Even during grinding by 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 does not decrease during grinding by slow return and for some reason the grinding load primarily rises above the load threshold LA at the time of speed limit execution (S37), the grinding load exceeds the load threshold LA. The exceeding is memorized (S38), and the cutting speed limiting function of the speed limit execution means 14A operates.

After that, when the cause of the temporary increase in the grinding load is eliminated, the grinding load is rapidly reduced by the slow return by the slow return speed V4 of the grindstone 1 . However, since the grinding load once exceeds the load threshold LX (S25), even if the grinding load of the grindstone 1 is less than the load threshold L4 at slow infeed (S26), the speed limit execution means 14A cuts The speed limit function operates, and the cut-off of the grindstone 1 is limited to the slowest limit cut-off speed Vα (= 0.03 mm/min) instead of the original slow cut-off speed V3 (= 0.05 mm/min). (S27).

Therefore, contact and separation between the grindstone 1 and the workpiece W are not repeated. Because if there is no speed limit execution function, when the grinding load falls below the load threshold L3 during grinding of the workpiece W by slow return (S34), it switches from slow return to slow infeed and slow infeed speed V3 (= 0.05 mm /min) to cut the grindstone (1). Therefore, when the cutting speed of the grindstone 1 is controlled according to the rise and fall of the grinding load, the grindstone 1 comes and goes rapidly at a fast cutting speed and a high return speed, and the grindstone 1 and the workpiece W come into contact There is a case where the grinding of the workpiece W does not proceed by repeating the separation.

However, even if the grinding load is lowered below the load threshold value L3 due to the slow return of the grindstone 1, the grindstone 1 is not immediately cut at a high cutting speed V3 (= 0.05 mm/min), and the limit cutting speed Vα (= 0.03 mm/min), it is possible to prevent a rapid increase in the grinding load of the grindstone 1 by switching from slow return to slow infeed, and the grindstone 1 returns and cuts There is no case of rapid repetition of the mouth. Therefore, as shown in the grinding load curve in FIG. 10 , the subsequent change in grinding load becomes stable, and the workpiece W can be efficiently ground.

In addition, in this embodiment, after exceeding the load threshold LA at the time of speed limit execution, even if the grinding load decreases, control is performed so as not to cut the grindstone 1 at a speed higher than the limit cutting-in speed Vα, but the grindstone 1 Even when returning, even if the limit return speed Vβ is set, and after the grinding load exceeds a certain load threshold LB, even if the grinding load goes down to near the upper side of the load threshold L4 thereafter, return faster than the limit return speed Vβ It is also possible not to return to speed.

11 to 13 illustrate a third embodiment of the present invention. As shown in Fig. 11, the grindstone cutting return control means 11 of this embodiment has a table selection means 16 capable of appropriately selecting the speed table stored by the speed setting means 14, and this table selection means The speed control means 15 is configured to control the grindstone conveying means 7 according to the table selected by (16).

Tables stored by the speed setting unit 14 include, for example, a first speed table T1 shown in FIG. 12 and a second speed table T2 shown in FIG. 13 . The table selector 16 can select the first speed table T1 and the second speed table T2 individually, or select a combined table combining parts of both the speed tables T1 and T2.

The combination table selects the front and back of 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. By setting the load appropriately to the load threshold value, changing the front and back of both speed tables T1 and T2 in the speed table changing load and combining them, from the speed table T1 or speed table T2 on one side to the speed table T2 or speed table on the other side It is one speed table configured to be converted to T1.

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

Therefore, at the time of infeed grinding, the grindstone cutting return control means 11 controls the cutting speed of the grindstone 1 according to the engagement table by the speed control means 15, respectively, while monitoring the change 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 value L3, the slow cutting speed of the grindstone 1 is set at the slow cutting speed V3 (= 0.05 mm/min) of the first speed table T1. make an incision Then, when the load threshold value L3 or more is reached, the first speed table T1 is changed to the second speed table T2, and the grindstone 1 is moved at a slow return speed V3 (= -0.05 mm/min) according to the second speed table T2. make a slow return In addition, other configurations, controls, and the like are the same as in each embodiment.

In this way, it is possible to configure a combination table by selectively combining parts of the first speed table T1 and the second speed table T2, and while using a small number of speed tables T1 and T2 as a standard, the material of the workpiece W, its It is possible to grind under optimum conditions outside.

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

14 illustrates a fourth embodiment of the present invention. In the case of infeed grinding the workpiece W with the grindstone 1, the grinding load during grinding may rise or fall depending on the conditions at that time. Therefore, as illustrated in the speed table in FIG. 14, it is possible to select which load threshold value to use for the rising phase and the decreasing phase of the grinding load in the speed table (ON is selected, OFF is not selected), and grinding Depending on conditions, necessary conditions may be appropriately selected.

In the case of the speed table of FIG. 14, there are control elements of high-speed infeed, fast infeed, medium infeed, slow infeed, slow return, intermediate return, fast return, and emergency return, and each control element is classified according to the rising phase and the falling phase. It is designed to be properly selected. For example, in the rising phase of the grinding load, intermediate infeed, slow return, and intermediate return are not selected, and in the lower phase, slow infeed is not selected.

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

15 and 16 illustrate a fifth embodiment of the present invention. As shown in FIG. 15, this grindstone cutting return control means 11 includes a grinding load measuring means 13 for measuring the grinding load of the grindstone 1 during grinding, the cutting speed of the grindstone 1 for each load threshold value, By comparing the speed setting means 14 for setting the return speed with the time setting means 17 for setting the acceleration/deceleration time when changing the cutting speed and switching between cutting and returning, the grinding load during grinding and the load threshold value. With the cutting speed and return speed set by the speed setting means 14 according to the increase or decrease of the grinding load, the grindstone transfer means 7 is controlled for cutting and returning, and at the same time, when the cutting speed is changed, the It has speed control means (15) for gently changing the speed in one direction in an acceleration/deceleration time (T) set by time setting means (17) at the time of switching.

In the grindstone infeed-return control means 11 having this structure, if the acceleration/deceleration time T is set in advance by the time setting means 17, the speed Since rapid change of can be prevented, there is no problem such as a temporary decrease in the grinding load, and the workpiece W can be efficiently ground under a high grinding load.

For example, when decelerating from a high-speed infeed of the infeed speed V0 to a fast infeed of the infeed speed V1, gradually decelerating from the infeed speed V0 to the infeed speed V1 in the acceleration/deceleration time T as indicated by the solid line in FIG. Therefore, as shown by the dotted line, compared to the case of immediate switching, it is possible to suppress a rapid change in speed and suppress a change in grinding load.

Also, even when switching from slow infeed at the infeed speed V3 to slow return at the return speed V4, as indicated by a solid line in FIG. Because of switching, as indicated by the dotted line, compared to the case of immediate switching, it is possible to suppress a rapid change in speed in the reverse direction and to suppress a change in grinding load.

In addition, it is also possible to set the acceleration/deceleration time T appropriately according to the material of the workpiece W and the like. In addition, in addition to allowing the acceleration/deceleration time T to be set variably, when changing the cutting speed and switching between cutting and returning, the speed control means 15 gradually or stepwise accelerates/decelerates according to predetermined acceleration/deceleration characteristics You can do it.

In the above, although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various changes are possible. For example, it is preferable that the number of load threshold values of the grinding load is large. Therefore, it is also possible to infinitely increase the number of load thresholds, and by increasing the number of load thresholds infinitely, stepless speed change in which the cutting speed of the grindstone 1 is steplessly reduced according to the increase in the grinding load is also possible.

Further, in the embodiment, although the workpiece W of hard and brittle material is exemplified, it is not limited to the hard and brittle material, and the same can be applied to the first half of surface grinding of the workpiece W of various materials.

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 current or electric power of the grindstone drive means 6 or a change in load applied to the grindstone drive means 6 , You may judge the grinding load by the change of the torque, current, electric power, and load of the work drive means 4. In the case of the surface grinding machine 2 without a work drive mechanism, the grinding load may be determined from the load applied to the work W. In addition, a combination of two or more related factors related to a change in the grinding load, such as combining a change in current, power or load of the grindstone drive means 6 and a change in current, power or load of the work drive means 4. You might as well make a decision.

In the first and second embodiments, the case where the grinding load increases during cutting is described above, but it goes without saying that if the grinding load during cutting decreases below a predetermined load threshold, the cutting speed may be controlled to increase. . Even in that case, the cutting speed may be accelerated over a predetermined period of time.

In addition, when the grinding load accelerates or decelerates the infeed speed based on a predetermined load threshold, or switches between infeed and return, it is sufficient if the grindstone 1 can enter and return based on a predetermined load threshold, It is also possible to determine whether it is below the load threshold or above the load threshold.

High-speed infeed, fast infeed, medium infeed, slow infeed, slow return, intermediate return, and fast return are just examples, and may be divided more finely than these, or roughly divided into small numbers. In addition, the values of each load threshold, infeed speed, and return speed are merely examples, and are not limited thereto.

1: grinding stone
2: flat grinding machine
3: rotary table
4: work driving means
5: grinding stone axis
7: wheel transfer means
10: sizing control means
11: grinding stone infeed return control means
12: dimension measuring means
13: grinding load measuring means
14: speed setting means
14A: speed limit execution means
15: speed control means
16: table selection means
17: time setting means

Claims (10)

When surface grinding a workpiece with a grindstone,
While monitoring the grinding load,
As the grinding load rises, the cutting speed of the grindstone is reduced,
When the grinding load exceeds a load threshold higher than the maximum load threshold at the time of cutting the grindstone, grinding is continued while relatively moving the grindstone in a direction opposite to that at the time of cutting at a predetermined speed according to the high load threshold A method for flat grinding of workpieces. When surface grinding a workpiece with a grindstone,
While monitoring the grinding load,
When the grinding load increases, the cutting speed of the grindstone is reduced,
When the grinding load decreases, the cutting speed is increased,
When the grinding load exceeds a load threshold higher than the maximum load threshold at the time of cutting the grindstone, grinding is continued while relatively moving the grindstone in a direction opposite to that at the time of cutting at a predetermined speed according to the high load threshold A method for flat grinding of workpieces. The method according to claim 1 or 2, wherein each cutting speed at which the cutting speed of the grindstone becomes slower as the grinding load increases corresponding to the plurality of load thresholds of the grinding load is set, and grinding is started at a predetermined speed. , A method for surface grinding of a workpiece, characterized in that the grindstone is decelerated or increased at a corresponding cutting speed whenever the grinding load rises or falls to a predetermined load threshold. The method according to claim 1 or 2, wherein a return load threshold higher than the maximum load threshold at the time of cutting 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. A method for grinding the surface of a characterized workpiece. The surface grinding method of a workpiece according to claim 1 or 2, characterized in that the incision and return of the grindstone are repeated before sparking out. The method according to claim 1 or 2, wherein when the grinding load exceeds the load threshold for speed limiting, the grinding load is reduced to the load threshold of the predetermined cutting speed after the grinding load exceeds the load threshold for speed limiting. A method for flat grinding of a workpiece, characterized in that the cutting stone is cut at a limiting cutting speed slower than a predetermined cutting speed even if it is lowered, and not faster than the limiting cutting speed. The work according to claim 3, wherein a return load threshold higher than the maximum load threshold at the time of cutting 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. of flat grinding method. 4. The method of flat grinding a workpiece according to claim 3, characterized in that cutting and returning of the grindstone are repeated before sparking out. The method according to claim 3, wherein when the grinding load exceeds the load threshold for speed limit execution, even if the grinding load decreases to the load threshold of the predetermined cutting-in speed after the grinding load exceeds the load threshold for speed limit execution, the predetermined A method for grinding the surface of a workpiece, characterized in that the cutting stone is cut at a limiting cutting speed slower than the cutting speed and not faster than the limiting cutting speed. As a surface grinding machine for in-feed grinding a workpiece with a grindstone,
grinding load measurement means for measuring the grinding load of the grindstone during grinding;
Speed setting means for setting cutting speeds of a plurality of grindstones corresponding to a plurality of load thresholds;
While comparing the grinding load and the load threshold during grinding, the grindstone is increased/decelerated at the cutting speed corresponding to each load threshold based on each load threshold so that the cutting speed of the grindstone decreases or increases according to the increase or decrease of the grinding load, and grinding When the load exceeds a load threshold higher than the maximum load threshold at the time of cutting the grindstone, while continuing grinding, speed control means for relatively moving the grindstone in the opposite direction to that at the time of cutting at a predetermined speed according to this high load threshold A flat grinding machine characterized in that it is provided.

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