JPH03294174A - Retraction grinding method in grinding by controlling grinding force - Google Patents

Abstract

PURPOSE:To automatize the setting of a retraction quantity, by fixing a retraction quantity to the bending equivalent quantity of a grindstone spindle at the grindstone place immediately before changing a grinding force. CONSTITUTION:A retraction quantity R is decided by a decision part 7 from the difference in the rough grinding force set value FR of the grinding force constant control and finish grinding force set value FF and the product (FR - FF) k. The retraction quantity R calculated by this decision part 7 is taken into a cutting control unit 4, the difference in the rough and finish grinding forces set values fed from a grinding force set part 1 and the grinding force output from a grinding force detecting part 3 is taken as well and a speed command is output to a cutting feed control motor 5 in order to control the rough and finish grinding forces based on this difference output. The cutting slide of a grindstone or work is then operated by a grinding part 6 by the command of this motor 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a grinding method using grinding force control, particularly to a glue traction bond grinding method when transitioning from rough grinding to finish grinding.

(Conventional technology) In the grinding process by grinding force control, the rough grinding force.

When controlling the final grinding force at a constant level, the grinding force setting is determined by the processing conditions (grinding wheel diameter, truing, and grinding wheel replacement).

Work type! Depending on the
Also, during the grinding cycle, for example, an internal grinder requires inclination adjustment, and the finishing grinding force setting is sometimes changed midway through. In response to such a situation, conventionally, when transitioning from rough grinding to finish grinding, the amount of torque is not changed and is usually left at the initial setting value. In addition, in internal grinding with a CBN grindstone, in order to eliminate poor cylindricity of the workpiece immediately after truing, grinding is carried out for a predetermined period of time after truing or for a predetermined number of workpieces by increasing the amount of traccitane than usual or grinding with a traxitane amount than usual, and then grinding with a traxitane amount of the normal amount. There is also a known method of reverting to (
For example, Japanese Patent Publication No. 63-62336).

(Problem to be solved by the invention) Retraction when transitioning from rough grinding to finish grinding is an action that reduces the amount of bending of the grinding wheel spindle that occurs during rough grinding and improves the machining accuracy of the workpiece at a low finishing speed. There is. Therefore, it is necessary to perform retraction as fast as possible after rough grinding is completed. If retraction is insufficient, the bending of the grinding wheel spindle caused by rough grinding remains, so even if you switch to finish grinding feed, the cutting speed due to bending is faster than the cutting speed due to finish feed rate, and the machining speed of the workpiece is reduced. If you think about it, it will exceed the finish grinding speed, which will have a negative effect on the machining accuracy of the workpiece (chattering, poor surface roughness), and if there is too much retraction, the grinding wheel will separate from the workpiece, resulting in new grinding wheel runout. (preload loss) occurs, causing chatter, which similarly has an adverse effect on the machining accuracy of the workpiece.

On the other hand, as a grinding detection method in constant grinding force control,
For example, there are various methods such as detecting the power of the grinding wheel spindle (tangential force) or tile bending with a displacement sensor (normal force, tangential force), or measuring it with some kind of strain gauge (normal force, tangential force). However, in these cases, a low-pass filter is often used to reduce the influence of the rotation component of the grinding wheel spindle, the rotation component of the workpiece, and the vibrations of the mechanical system. However, this time constant causes a delay in control, which is inherently undesirable.For this reason, in constant grinding force control, the grinding force of the grinding wheel at the completion of traction from rough grinding to finish grinding is equal to the finish grinding force. It is preferable that they be at the same level.

In conventional grinding force control grinding with fixed retraction completion, there are times when the retraction amount is appropriate depending on the grinding force change, and times when it is not.If the retraction amount is inappropriate, the above-mentioned processing accuracy may be affected. In addition to the negative effects, there is also the problem that grinding time becomes longer. Fig. 3 (aJ to (C)) is a diagram showing the grinding process by changing the grinding force when grinding is carried out with the beam traction amount fixed. First, Fig. 3 (a) shows the case where the beam traction amount is insufficient; Rough grinding completed (A
Shift to retracting at point), finish grinding force F, then F
Retraction is completed (point B) with a grinding force of F + α. At this point, finish grinding begins, so the finish grinding force F, a
The grinding time increases by T (seconds) until m. in this case,
Since the speed of the cutting slide is stopped and the cutting is performed by bending the grindstone spindle, if the cutting quality of the grindstone is poor, the time T1 will become longer. FIG. 3(b) shows a case where the retraction amount is appropriate, and the grinding force at the time of completion of retraction matches the finishing grinding force FF. Figure 3 (C) is a case of excessive beam traction, and the grinding force is lower than the final grinding force F by β, so the period T until the final grinding force is controlled to F is
z (seconds) Grinding time will be extended.

In addition, with the method of increasing the retraction amount only immediately after truing, the actual retraction amount is manually changed based on experience, so the amount of retraction may be insufficient or excessive depending on the grinding force, and unmanned operation is The problem is that it can't be done.

SUMMARY OF THE INVENTION An object of the present invention is to provide a retraction grinding method that can automatically grind with an optimum amount of traction even when the grinding force is changed.

(Means for Solving the Problems) According to the present invention, in the traction grinding method, the grinding wheel is returned to the direction opposite to the cutting direction when changing the grinding force during processing, and then the grinding wheel is ground again with a different grinding force. A grinding force controlled grinding paste traction grinding method is provided in which the amount of retraction is determined to be the amount equivalent to the bending of the grindstone spindle at the point of the grindstone immediately before the grinding force is changed.

Here, in order to determine the bending equivalent amount R of the grindstone spindle, the rough grinding force setting value is Fヮ, the finishing grinding force setting value is F2. If the spring constant of the grinding wheel spindle is k, then R=
(Ft - FF)xk.

(Function) In the present invention, the rough grinding force setting value of constant grinding force control,
The amount of bending of the grinding wheel spindle is determined from the difference between the final grinding force set value and the spindle spring constant, and this is used as the retraction amount. Therefore, when the retraction is completed, the grinding force of the grinding wheel will be at the same level as the final grinding force, and the final grinding time will be reduced. and improves machining accuracy. Since the retraction amount is quantified as described above, it is possible to automatically set the traction amount when changing the grinding force, and it becomes easier to control the finishing grinding force.

(Example) Next, an example 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 method of the present invention, and FIG. 2 is a plan view of a grinding machine to which the present invention is applied. 1 is a grinding force setting section that sets the grinding force, and sets the rough grinding force F++ and finish grinding force F. 2 is a grinding wheel diameter determination section, and the grinding force setting section 1 performs rough and finish grinding. The force setting is switched by the signal from the second grindstone diameter determination section 2. Generally, the grindstone cutting quality differs depending on the grindstone diameter, but this means that if the grinding efficiency is kept constant, the rough grinding force and finish will vary depending on the grindstone diameter. It becomes necessary to change the grinding force setting.

That is, when the diameter of the grinding wheel is large, it is necessary to set the constant value of the grinding force (threshold force) tst to be larger than when the diameter of the grinding wheel is small, and the retracting amount also changes accordingly. Specifically, the diameter of the grinding wheel is divided into three ranges: large, medium, and small, and the finishing grinding force is set accordingly. Note that the diameter of the grinding wheel may be divided into multiple stages, and the finishing grinding force can be set accordingly. Since the amount of change in the grindstone diameter can be indirectly determined by the amount of change in the cutting slide position during truing, the size of the grindstone diameter is determined based on this. 3 is a grinding force detection unit for detecting the grinding force; 7 is a retraction amount determining unit;
Rough and finish grinding force setting values Fl, FF from grinding force setting section 1
The retraction amount R is determined by the product (F mFF )k of the O difference and the spring constant of the grindstone spindle measured in advance. Note that k is measured in a static state where the grindstone spindle is not rotating. Reference numeral 4 denotes a cutting depth control device for controlling the grinding force at a constant level, which takes in the retraction amount R calculated in step 7 at the time of completion of the retraction, and also controls rough and finishing grinding force settings from the grinding force setting section 1. The difference between the value and the grinding force output from the grinding force detector 3 is taken in, and based on this difference output, a speed command is output to the cutting feed control motor 5 in order to control the rough grinding force and the finishing grinding force to a constant level. do. The grinding section 6 operates a grindstone or a cutting slide of the workpiece according to a command from the cutting feed control motor 5. In addition, the above-mentioned rough and finish grinding force setting values F, , F.

may change during the cycle.

The grinding machine shown in Figure 2 is equipped with a swivel angle adjustment function. A grindstone spindle device 20 is provided on a bed 26 of the grinding machine via a grindstone feeding table 21, and a grindstone 25 is supported by the tip of a grindstone spindle 23 and rotates. A swivel plate 29 is installed on the bed 26 so as to be able to rotate around a pivot 30, and a headstock 31 of the workpiece 24 is mounted on the swivel plate 29. Spindle motor 32 and headstock 31
A cutting feed motor 33 is provided. Furthermore, a swivel adjustment motor 34 is provided on the side of the vent, an output shaft of which is connected to a ball screw shaft 37, and an operating member 35 including a pole nut that is threadedly engaged with the screw shaft is connected to the swivel plate 29.
It is fixed to the 0 side.

By driving the swivel adjustment motor 34, the swivel plate 29 and the headstock 31 are rotated about the pivot 30 via the operating member 35, and the swivel angle of the workpiece 24 is adjusted. 36 is a drive motor for the grinding wheel feeder 21.

(Effects of the Invention) As already mentioned, the setting of the grinding force in constant grinding force control is changed depending on the processing conditions, and in this case, the present invention calculates the optimum amount of traction depending on the situation. By setting the amount of retraction, it is now possible to automate the setting of the amount of retraction, which was previously done manually, and also solves the problem of prolonging the finish grinding time due to insufficient or excessive retraction, which was the case with the conventional fixed amount of traction. Furthermore, great effects such as improved machining accuracy of the workpiece are brought about.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a control system for carrying out the method of grinding a glue machine according to the present invention, Fig. 2 is a plan view of a grinding machine suitable for applying the present invention, and Fig. 3 (Q~( C) is a diagram showing the grinding process by changing the grinding force when the retraction amount is fixed. 1...Grinding force setting section, 2... Grinding wheel diameter determination section, 3...
- Grinding force detection section, 4... Cutting control device, 5... Cutting feed control motor, 6... Grinding section, 7... Retraction machining amount determining section.

Claims (2)

[Claims] (1) In the retraction grinding method, in which the grinding wheel is returned in the opposite direction to the cutting direction when changing the grinding force during processing, and then grinding is performed again with a different grinding force, the retraction amount is calculated at the point of the grinding wheel immediately before the change in the grinding force. A retraction grinding method in grinding with controlled grinding force, characterized in that the grinding force is set to an amount equivalent to the bending of a grinding wheel spindle. (2) The bending equivalent amount R of the grinding wheel spindle is defined as R=(F_R-F_F)×k where F_R: rough grinding force setting value F_F: finishing grinding force setting value k: spring constant of the grinding wheel spindle, and this R 2. The retraction grinding method in grinding force controlled grinding according to claim 1, wherein the retraction amount is set as the retraction amount.