JPH0430957A - Control method for grinder - Google Patents

Abstract

PURPOSE:To achieve the prevention from burning in grinding and the improvement in efficiency, by varying a grinding speed in accordance with the change in the grinding wheel sharpness with the grinding wheel sharpness being found on each grinding cycles. CONSTITUTION:A grinding speed is operated by the signals transmitted from a grinding wheel diameter arithmetic part 2 and grinding force detection part 3 by an arithmetic control part 1 and the result thereof is output to a notch control part 4. The grinding wheel arithmetic part 2 divides the grinding wheel diameter in three large, medium and small ranges, for instance, and sets the grinding start speed and steady grinding speed corresponding thereto like starting speed and steady speed. Namely the grinding wheel sharpness is found on each grinding cycles from the grinding speed detection value during grinding and grinding force detection value and the grinding speed is made to be controlled in proportion to this grinding wheel sharpness. Consequently it is effective very much as a grinding seizure counter measure and grinding efficiency and the improvement of the working accuracy of a work can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of controlling a grinding machine that grinds the inner and outer surfaces of a cylindrical or cylindrical workpiece.

(Prior art) In this type of grinding machine, the cutting quality K (metal removal parameter) of the grinding wheel has a great influence on the machining accuracy and grinding cycle time, as does the grinding feed rate (grinding speed), but the cutting quality of the grinding wheel It varies depending on the type, grinding wheel diameter, truing, dressing, etc. When grinding with a grindstone that has large variations in cutting quality, such as a CBN grindstone, the cutting quality of the grindstone is generally poor after dressing or when the grindstone is tilted to a large diameter, and if steady grinding feed is performed in this condition, the grinding force will be excessive. This often results in grinding burn. FIG. 7(a) is a diagram showing the relationship between grinding force and grinding speed to show that a difference in grindstone cutting quality results in a difference in grinding force. In the figure, A shows a condition in which the diameter of the grindstone is small and the sharpness of the grindstone is good, and B shows a state in which the diameter of the grindstone is large and the sharpness of the grindstone is poor.

It is known from experience that the cutting quality of a CBN grindstone improves with repeated grinding, but in FIG. 7(a), the slope of the straight line changes from B to A. Rough grinding speed v
When set to 1, a grinding force of F is applied when the cutting quality is good, and a grinding force of F2 is applied when the cutting layer is sharp.

When F2 >F, a large force is generated on the machined surface of the workpiece. : Since the force of rubbing against the bond surface of the grindstone is greater than the force of grinding, it is easy to cause grinding burn due to grinding heat (points C and D in Fig. 7 (C)). Therefore, we usually set an empirical number of skips until the cutting quality becomes good, as shown in Fig. 7(b).
As shown in (C), the grinding speed is increased in stages.

Figure 8 shows the relationship between the spark-out grinding time and the final grinding force when feed rate grinding is used and the final grinding force is controlled to a constant level. This is an example showing that there is a dimensional change. A is a case where the cutting quality is good, and B is a case where the cutting quality of the whetstone is poor. From the completion of finishing feed to spark-out grinding 10 seconds after stopping feed, the grinding force after 10 seconds becomes F and F2, and the workpiece dimensional change is (F2-Fl)X2X per diameter.
This appears as a difference of about 1/ktIm. Note that k is the grindstone shaft spring constant (KG/μm).

(Problem to be solved by the invention 'I3) As mentioned above, in the conventional grinding method, the grinding speed was determined by the number of skips set empirically regardless of the sharpness of the grinding wheel, so it was inevitable to set the speed on the safe side. settings, limiting grinding efficiency. On the other hand, there is a method of calculating the sharpness of the grinding wheel and changing the grinding force, but in the case of grinding the inner groove of the outer ring of the bearing, in the case of grinding force control, the grinding force is applied to the grooved part 10a of the work 10 as shown in FIG. 9 hits, and excessive force is likely to be applied locally, causing grinding burn on the workpiece. In addition, the conventional method of determining the spark-out time based on experience,
In the case of feed rate grinding, there was a problem in that it caused slight dimensional changes. In addition, the cutting quality of a CBN grindstone is affected not only by the diameter of the grinding wheel, but also by changes in the condition of the lure, etc., and is easily affected by truing and dressing, making it extremely difficult to control the sharpness within a certain range. Met.

In view of these problems, the present invention automatically determines the grinding speed and truing based on the grinding quality of the grinding wheel, thereby improving the grinding efficiency and efficiency even in the case of CBN grinding wheels, and also improves the grinding efficiency of the grinding wheel. It is an object of the present invention to provide a grinding control method capable of improving workpiece machining accuracy and grinding efficiency by automatically controlling spark-out time according to taste.

(Means for Solving the Problems) A method for controlling a grinding machine according to the present invention determines the grinding wheel cutting quality for each grinding cycle from the grinding speed detection value and the grinding force detection value during grinding, and calculates the grinding wheel cutting quality proportional to this grinding wheel cutting power. Can you control the grinding speed? ! l
(increase/decrease).

Further, according to the present invention, there is provided a grinding control method characterized by monitoring the sharpness of the grindstone after true ink, and performing truing and dressing so that the sharpness of the grindstone falls within a predetermined range.

Furthermore, according to the present invention, the grinding force during spark-out is monitored, and when the grinding force falls to a target value, the grinding wheel is rapidly retreated, or when the spark-out time deviates from the set value, the spark-out is performed. A grinding control method is provided that is characterized by changing the grinding force and correcting the cut-up point (dimensional adjustment).

Further, according to the present invention, the grinding wheel cutting quality is determined for each grinding cycle from the grinding speed detection value and the grinding force detection value during grinding, and the spark-out time during grinding is controlled according to the grinding wheel cutting quality. A grinding force control method is provided.

(Function) According to the present invention, grinding is very effective as a countermeasure because the cutting speed is changed depending on the sharpness of the grindstone, and the grinding efficiency can be improved. Furthermore, by monitoring the sharpness of the grindstone, the properties of the grindstone after truing and dressing, that is, the sharpness of the grindstone, can be controlled within a predetermined range. In addition, the spark-out time is automatically controlled by the sharpness of the grindstone, so that the machining accuracy of the workpiece can be maintained stably.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a control system for implementing the control method according to the present invention, and FIG. 2 is a plan view of an internal grinder to which the present invention is applied. As described above, the present invention detects the grinding speed and grinding force, calculates the grindstone cutting quality, and increases or decreases the grinding speed in proportion to the grindstone cutting quality. Specifically, the arithmetic control section 1 calculates the grinding speed according to a calculation formula described later based on signals from the grindstone diameter calculation section 2 and the grinding force detection section 3, and outputs the result to the cutting control section 4. For example, the grindstone diameter calculation unit 2 divides the grindstone diameter into three ranges: large, medium, and small, and sets the corresponding grinding start speed and steady grinding speed to the start speed (medium).
, set like steady speed (medium). Of course, the diameter of the grinding wheel can be further divided into multiple stages, and the corresponding speed can be set. By changing the grinding speed, the grinding force during grinding is lowered and settings are made to prevent grinding burn from occurring.If the grinding wheel diameter is large and the grinding speed remains at V, the grinding force F will be large as F2. In order to avoid this, the grinding speed is set to v2 when the diameter of the grinding wheel is large.

Further, since the amount of change in the diameter of the grinding wheel during use can be indirectly determined by the amount of change in the cutting slide position during truing, the size of the diameter of the grinding wheel can be determined based on this. A cutting control section 4 for controlling the cutting speed to a constant value outputs a speed command signal to a cutting feed control section 5. The cutting feed control section 5 is connected to the cutting motor 7 (second
), and the grinding section 6 drives the cutting slide 8. in FIG. The grindstone 9 is operated to cut into the workpiece IO.

11 is a grindstone shaft motor, 12 is a grindstone shaft, and 13 is a grindstone feed motor.

After truing is completed, a grinding start speed is set, for example, a grinding speed corresponding to the grindstone diameter, and grinding is started. In this case, grinding is started using two starting speed settings: a rough speed setting and a finishing speed setting. During grinding, each grinding force is measured by the grinding force detection unit 3, and the grindstone cutting edge K is calculated using the calculation formula shown below.

■,...Rough speed setting (vw/s), ■,...finishing speed setting (msr/s), Fll...rough grinding force (KG), F,...finishing grinding force (K( 1,), Dw...workpiece finishing dimension (ms+), B...during grinding (am), all of these are executed by the arithmetic control unit 1.Once the grinding wheel sharpness K has been determined, next this Whetstone sharpness K
Based on the following calculation formula, the rough grinding speed ■1. The finish grinding degree (■) is automatically calculated by the calculation unit 1.

Vr = V++oX (mm/s)K
mt? Vr = VFIIX (mm/s
)K□.

■1゜... Steady state finishing speed (ms/S), ■
,. ... Steady state finishing feed rate (am/s), K
, E, -...Steady state sharpness (III+"/K G-
s) According to the above formula, grinding is performed at a speed proportional to the grindstone cutting quality until the cutting edge of the grindstone reaches a steady state, and once it reaches a -degree steady state, grinding is continued at a steady speed.

FIGS. 3(a) to 3(C) show the relationship between the number of grinding pieces (number of skips N), the sharpness of the grindstone, the grinding speed (2), and the grinding force F, respectively. The number of grinding pieces N is required for the above type of whetstone sharpness.
It is also conceivable to use a moving average of 1, or to limit the rate of increase in speed.

In this way, it changes as shown in Figure 3(b) and (C),
Compared to FIGS. 7(b) and 7(C), grinding can be performed smoothly and efficiently. Kll! , is the steady speed at which the sharpness of the whetstone is stable (■7°, ■,
. )) (Figure 3 (a))
).

In another embodiment of the present invention, the sharpness of the whetstone after truing is monitored, and the truing and dressing are controlled so that the sharpness of the whetstone falls within a predetermined zone. C
I have experienced that the cutting quality of BN whetstones deteriorates due to truing. After truing is completed, the workpiece is ground to obtain the grindstone cutting edge K, and the above-mentioned characteristics are utilized. For the sharpness of the whetstone,
K〉In the case of maximum setting sharpness, it is determined that truing is insufficient,
All operations for executing truing are executed by the arithmetic control unit 1. Even if the predetermined N-tero truing is performed, if K〉maximum setting sharpness, the truing is determined to be NG and the cycle is terminated to prevent grinding burns. On the other hand, if excessive truing results in K<the minimum setting sharpness, dressing is performed to bring out the sharpness of the whetstone. Similarly, after the completion of drenching, the workpiece is ground, the grindstone cutting quality K is determined, and dressing is determined to be insufficient. To prevent this, the cycle is terminated.

A series of these steps is shown as a flowchart in FIG. Figure 5 is a diagram for explaining the method of determining the truing zone by judging the sharpness of the grinding wheel, and shows the relationship between the number of workpieces and the sharpness of the grinding wheel from the start of truing to the start of actual grinding (Fig. −■ process). The illustrated example is a case where the grindstone sharpness is controlled to fall within the predetermined truing determination zone for the fourth time. Through this series of cycles, the sharpness of the whetstone after truing can be brought into a state of minimum set sharpness <grindstone sharpness <maximum set sharpness.

As another embodiment of the present invention, an example in which the grinding force during spark-out is monitored and the depth of cut is retracted at a constant speed when the grinding force at the completion of spark-out has decreased to a target value will be shown below. It has already been mentioned that the dimensions of the workpiece change depending on the relationship between the sparkout time and the sharpness of the grinding wheel after finish grinding is completed, but it is clear that as a countermeasure to this, the dimensions of the workpiece will be the same if the grinding force at the completion of sparkout is kept constant. be. As an example of this, the relationship between spark-out time and grinding force is shown in Figures 6 (a) and (b).
). F is the finish grinding force, and spark-out starts after cutting feed stops. F is the grinding force at which the spark-out is completed, and the grinding force detector 3 in Fig. 1
The grinding force and Fz are compared with each other, and when it is confirmed that the two match, a rapid retraction command is issued to the cutting control unit 4, and the cutting force is input to the cutting feed control unit. 5 drives the cutting motor 7, and the cutting slide 8 starts to retreat and returns to the grinding origin. In this way, even when the sharpness of the grindstone is good or bad as shown in FIG. 6(a), the influence of dimensional changes due to the sharpness of the grindstone is reduced. However, depending on the sharpness of the grindstone, the threshold force (the limit of grinding force that can be ground) is shown in Figure 7 (
As shown in a), it fluctuates as Fat→F o+, and F
As # and F o+ get closer, the grinding progresses as expected and disappears. In order to improve the roundness and vibration of the workpiece, it is better to keep F# somewhat close to the threshold force. If this situation is shown in FIG. 6(a), it is conceivable that the spark-out extension time β becomes longer and the cycle time fluctuation becomes larger. As a countermeasure to this, change F# as follows. As a guideline for change, measure the spark-out time T& (the time it takes to drop from FF to FI) and change F#. How to change: First, spark out lower limit time T L < T # < Spark out upper limit time T
, T is controlled by adding or subtracting a predetermined offset amount α1 to F so that . It is also possible to use N moving averages for T.

T#≧Tlj, Fgu'-Fν+α, (KG)Ta≦TL
So F ,'= F , -α, (KG) The above condition is continuous N
It is also possible that it will be changed to F in the second round. All of the above calculations are executed by the calculation control section 1. Next, regarding the control of the workpiece dimensions when F is changed, the dimensional change is calculated in terms of diameter using the formula shown below.

Δd=(F#'-F#)Xi/kX2 (μm)k...
・Spindle spring constant (KG/μm) In order to correct this amount of change in diameter conversion, the 57 finishing feed completion points are changed. If the finish feed completion point after the change is St', it becomes ST' -3r-Δd (μm), and the dimensional correction corresponding to the change in F& is controlled at the finish feed completion point. All of the above calculations are executed by the calculation control unit l. (Thus, stable spark-out can be executed by To. These situations are shown in Fig. 6(b) and (C).

A similar measure can also be taken by changing the spark-out time T0 depending on the sharpness K of the grindstone. An example of this is shown below.

The grinding force that changes from finish grinding force to sparkout is F.
#, the change in grinding force F due to sparkout is F a = (F F F ,, 6) e-” as shown in the following formula.
F...

Second, if L in the above equation is set as the spark-out time T0, F# can be kept constant by changing To with the sharpness K of the grindstone. To is calculated by solving t from the above equation. These are all calculated by the arithmetic control section 1, and To is input to the cutting control section 4 as a new spark-out time. Thus, as shown in Figure 6(a), To
By changing F, it is controlled to be almost constant, and the influence of dimensional changes due to grindstone cutting quality is reduced. It is also conceivable to use N moving averages for the above-mentioned grindstone cutting quality, and it is also possible to set a limit on the spark-out time. Even in this method, since Fd is too close to Fn@, there may be a drawback that To becomes too long. In this case, the force F== at the spark-out completion point and the finish completion point S7 is changed.

F. is found from (VIFF-V, F,)/(ve-VF), F,>Fa>F. F −= F−o
+α.

seek. α. is a predetermined constant. This allows T
o can be kept almost constant.

Next, a method of controlling the spark-out time in inverse proportion to the grinding wheel sharpness K and keeping F constant to reduce changes in workpiece dimensions will be described below. As shown in FIG. 6(a), the spark-out time is varied depending on the sharpness of the grindstone, and the grinding force F at the time of completion of spark-out is controlled to be approximately constant. The spark-out time T0 to be controlled is calculated using the following formula (% formula %) (1) However, T...optimum spark-out time when grinding in a steady state (stable cutting quality, steady grinding speed), K IEF...in a steady state The cutting quality of the CBN whetstone is poor after truing, but as the grinding process continues, it becomes almost stable. The sharpness in this state is K
When the sharpness of the grindstone is worse than the steady state sharpness as RtF, T,>T, (TO=T+α). Also, assuming that the sharpness of the whetstone has become better than in the steady state, To <
”r, but since spark out is originally intended to improve the roundness and chatter of the workpiece, T0≧T, and once it reaches a -degree steady state, then T, =T. Continue grinding.

It is possible to use N moving averages for the above-mentioned grindstone cutting quality, and it is also possible to limit the rate of change of the spark-out time. In this way, as shown in FIG. 6(a), the influence of dimensional changes due to the sharpness of the grindstone can be reduced. T above.

is automatically calculated by the arithmetic control unit l and applied during the next grinding.

(Effects of the Invention) As explained above, according to the present invention, since the grinding speed is changed according to the change in the sharpness of the grinding wheel, not only is it possible to prevent grinding burn and improve efficiency at the same time, but also the speed setting is automated. This enables unmanned operation of the grinding machine. In addition, by controlling spark-out, stable quality with good processing accuracy can always be obtained.

By determining the truing zone, it is possible not only to use the grindstone in a good condition, but also to be able to determine whether the truing device itself or the drainage device itself is NG.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a control system when implementing the control method according to the present invention, Fig. 2 is a plan view of an internal grinder applied to the present invention, and Figs. 3 (a) to (C) are Each figure shows the relationship between the number of pieces to be ground, grinding wheel cutting quality, grinding speed, and grinding force. Fig. 4 is a flowchart of truing zone determination in the present invention. Fig. 5 shows truing zone determination by grinding wheel cutting quality judgment. A diagram showing the relationship between the number of grinding pieces (number of skimps) and the sharpness of the grindstone for explaining the method, FIGS. Figure (C) is a diagram showing the cutting pattern in the present invention, Figure 7 (a) is a diagram showing the relationship between grinding force and grinding speed, and Figure 7 (C) is a diagram showing the relationship between grinding force and grinding speed. Figure 8 is a diagram showing the relationship between rough grinding speed and rough grinding force, Figure 8 is a diagram showing the grinding cover turn from general finish grinding to spark out, and Figure 9 is a diagram showing the state of the grindstone hitting the groove edge in groove grinding of the outer ring of the bearing. FIG. l... Enka control section, 2... Grinding wheel diameter calculation section, 3...
Grinding force detection unit, 4... Cutting control unit, 5... Cutting feed control unit, 6... Grinding unit, 7... Cutting motor, 8...
- Cutting slide, 9... Grinding wheel, 10... Workpiece, 11... Grinding wheel shaft motor, 13... Grinding wheel feed motor.

Claims (6)

[Claims] (1) A grinding machine characterized in that a grinding wheel cutting edge K is determined for each grinding cycle from a grinding speed detection value and a grinding force detection value during grinding, and the grinding speed is controlled in proportion to this grinding wheel cutting edge. Control method. (2) Monitoring the grindstone sharpness K after truing,
A method for controlling a grinding machine, characterized in that truing and dressing are performed so that the sharpness of the grindstone falls within a predetermined zone. (3) The grinding wheel cutting edge K is determined for each grinding cycle from the grinding speed detection value and the grinding force detection value during grinding, and the spark-out time during grinding is controlled according to the grinding wheel cutting edge. How to control a grinding machine. (4) A method for controlling a grinding machine, which comprises monitoring the grinding force during spark-out, and rapidly retracting the grindstone when the grinding force falls to a target value. (5) The method for controlling a grinding machine according to claim 3, characterized in that when the actual spark-out time deviates from the set value, the spark-out grinding force is changed and the cutting point is corrected. (6) The method for controlling a grinding machine according to claim 3, characterized in that the spark-out time is controlled in inverse proportion to the grinding wheel cutting edge K so that the grinding force during spark-out is constant.