JPH0451300B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vibration grinding machine using an ultrasonic vibration grinding wheel that can easily precisely grind rubber, ceramics, etc., which are difficult to grind using conventional grinding methods.

(Prior Art) In order to perform precision machining using cutting and grinding tools, it is necessary to perform the machining using a method that reduces the force applied to the workpiece as much as possible. The cutting force can be reduced by rotating a finite number of cutting edges on a rotating disk, such as a slice, at high speed. By rotating a grinding wheel with a countless number of abrasive grains distributed on a rotating disk at high speed for grinding, the cutting depth per abrasive grain becomes even smaller, and the force acting on the workpiece is drastically reduced, resulting in precision. It becomes possible to process. However, on the other hand, it is already well known that due to high-speed grinding of about 2000 m/min, the average grinding temperature increases significantly to the extent that the workpiece and the grinding wheel must be cooled due to the large amount of grinding material. Grinding using a grinding wheel is currently widely used, as it has a tremendous effect of drastically reducing the force acting on the workpiece, despite the fact that the grinding wheel generates significant heat due to the high-speed rotation of the grinding wheel. . The material of conventional workpieces is mainly metal, which has good heat transfer efficiency and good cooling effect even when it generates heat, so precision grinding has been made possible by using a large amount of appropriate grinding material.

(The problem that the invention aims to solve) However, today, new materials are being developed regardless of the presence or absence of precision processing theory and technology, and some of these materials have poor heat transfer efficiency, such as rubber, FRP, and ceramics. Contains many materials. These materials are also required to have extremely high machining accuracy.

In order to meet these expectations for precision machining, there is a need for a grinding method that can further reduce the average grinding temperature rise and sharply reduce the grinding force. There is a problem in that there is no grinding machine for soft and sticky materials such as rubber, which is common to hard and brittle materials such as metals and ceramics.

(Means for Solving the Problems) The present invention aims to provide a grinding machine that can reduce the average grinding temperature rise, further reduce the grinding force, and perform precision grinding on any material under the same pressure conditions. The object has a length of 1/2 wavelength,
In the radial direction, the vibration node occurs in the center of a round bar with a diameter d that resonates in a vertical ultrasonic vibration state with a natural frequency f, and the hole surface with an inner diameter d is the vibration node, and the outer peripheral surface with an outer diameter D is the antinode. A circular plate with a uniform thickness or thicker near the outer circumferential surface that resonates at the natural frequency f is provided, and a group of abrasive grains is provided on the outer circumferential surface and side surfaces of the disk. The grinding wheel is a vibrating grinding wheel, which has vibration nodes in at least two places and has a longitudinal ultrasonic vibration with a natural frequency f.The grinding wheel has a vertical ultrasonic vibrator with a natural frequency f attached to the tail, and the tip of the rotating main shaft. It is characterized in that it is fixed to a vibrating abdomen and rotated to generate a pulsed grinding force waveform to make chips fine.

(Example) FIG. 1 shows a grinding mechanism and a grinding force waveform in a conventional grinding method. In the grinding mechanism when the grinding wheel 1, which rotates at high speed in the direction of the arrow 3 at a grinding speed V, applies a depth of cut t to the workpiece 2, one abrasive grain in the grinding wheel cuts an area ABC shown by diagonal lines. do. Since the abrasive grains are rotating at high speed, even if the cutting depth of the grinding wheel is t, the apparent true cutting depth gc of one abrasive grain blade is extremely small. The waveform of the grinding force at this time changes periodically due to the high speed rotation of the abrasive grains distributed at intervals on the cylindrical surface and the elastic vibration of the abrasive grains. When expressed as a model, both the principal force Pc and the thrust force Pt are expressed in the form Pmean+Psinωt, as shown in the figure. If the spring constant in the direction of the back force of the workpiece is k and the angular natural frequency is ω _o , then grinding is generally performed with the relationship ω _o ≪ω, so the back of the workpiece is related to machining accuracy. The amount of elastic displacement X of the workpiece in the component force direction is X=Pmean/k. In order to improve machining accuracy, it is necessary to reduce this displacement amount X. For this purpose, it is necessary to reduce the force pressing the grinding wheel against the workpiece. That is,
It is necessary to reduce the value of Pmean to improve sharpness.

To date, the inventor has developed a method of vibratory grinding at a grinding speed of V<2πaf by ultrasonic torsional vibration of the grinding wheel in the grinding direction, that is, the direction of arrows f and a in 5 of the grinding wheel in FIG. Invented it. With this method, the grinding force waveform becomes a pulsed grinding force waveform 6 as shown in the figure, and if the absolute value of the pulsed grinding force is P', then the displacement X in the direction of the thrust force is X≒tc/T・P'/k becomes. Here, tc is the net grinding time in one cycle of vibration of the grinding wheel, and T is the vibration period. At this time, P′<
It becomes P. In other words, the grinding force at the contact surface of the grinding wheel
P′ also decreases, and the displacement X of the workpiece in the direction of thrust force, which is related to machining accuracy, becomes tc/T (1/3 to 1/10) compared to the displacement at the same grinding speed in the conventional grinding method. Decrease. However, at this time, the grinding speed V is set to be low, so if you try to grind it by making it equal to gc at a grinding speed of 2000 m/min, the feed speed V9 of the workpiece will be slow, resulting in a decrease in grinding efficiency. occurs.

Therefore, we considered a grinding method that takes advantage of the above-mentioned characteristics and does not reduce grinding efficiency.

In Fig. 3, regular fine grooves with a fine pitch lp and a height Rmax are formed on the surface of the workpiece, and the grinding wheel is machined with a grinding wheel rotating at high speed at a circumferential speed of V3 as a cutting depth of T<<Rmax. Grind the object by applying the feed rate V shown in Figure 1.

By doing this, it is possible to obtain the ideal pulse cutting force waveform in the mechanical process of grinding as shown in Figure 4 without slowing down the feed rate of the workpiece using a high-speed rotating grinding wheel. Grinding can be done more efficiently with less heat generated. As shown in Fig. 2, the cutting depth t > Rmax, and the curve AC on the grinding surface where the grinding wheel and workpiece contact.
When grinding into a smooth circular arc, the grinding wheel is vibrated in the grinding direction and the conditions of V<2πaf are applied to perform low-speed grinding to generate a pulsed cutting force waveform. This grinding mechanism is characterized by a grinding method in which the area near the top of the mountain is ground with a grinding wheel rotating at high speed, and the chips are shredded to generate a pulsed cutting force waveform.

Next, a description will be given of how to continuously generate this fine uneven groove shape on the ground surface.

FIG. 4 is a diagram showing the grinding area 10 per abrasive grain blade in conventional grinding, which will be explained to facilitate understanding of the features of the present invention. The tip of one abrasive grain 8 on the circumference of the grinding wheel 1 rotates on an approximate arc AB⌒,
Abrasive grain 9 located at the next point of abrasive grain 8 is an approximate arc AC⌒
rotate above. Then, the abrasive grains 9 grind the portion corresponding to the black area ABC to generate chips. At this time, the depth of cut gc per abrasive grain is
gc≪t.

Figure 5 shows the grinding force waveform 1 due to the abrasive grains 9 at that time.
2 is shown. The maximum grinding force is P ₅ Kgf at point B, which indicates the maximum depth of cut per tooth gc14.
Consider dividing the area 12 of this grinding force waveform into pulses without reducing the grinding speed of the grindstone. The only concrete way to achieve this is to shred the chips. One of the methods is the method of the present invention in which ultrasonic waves are applied to a high-speed rotating grinding wheel in the radial direction for grinding. That is, as shown in FIG. 6, a method of high-speed grinding at a grinding speed V3 using a radial ultrasonic vibration grinding wheel 14 that vibrates ultrasonically at a frequency f and an amplitude ar in the direction of an arrow 13, which is the radial direction of the grinding wheel. done by. At this time, the motion trajectory of the abrasive grains 8 of the grinding wheel is a sine wave motion trajectory 15,
The motion locus of the abrasive grains 9 shows a sinusoidal motion locus 16, and the intermittent black portions therebetween are the grinding area to be ground in one cycle of vibration. This grinding area is intermittent with a period of T/2 (T=1/f) seconds. Therefore, the chips are shredded and form a pulsed grinding force waveform. For example, as shown in FIG. 7, three pulse cutting force waveforms 20 can be provided. Because the depth of cut varies, the individual pulse forces are not uniform and vary in height as shown. The grinding force shows the maximum value at point B where gc is maximum. If this is P ₇ Kgf, this P ₇ becomes P ₅ > P ₇ with respect to P ₅ .

According to the present invention, the grinding force can be reduced compared to the conventional method in which continuous chips are generated.

The above is based on the assumption that the abrasive grains are distributed regularly on the circumference by modeling the addition of abrasive grains, and the three minute areas 18, 19, and 20 shown with diagonal lines in FIG.
Although the case where fine division is performed has been described, the number of fine divisions and the area shape thereof change depending on the grinding conditions. For example, as the frequency f increases, the number of divisions increases, and as the grinding speed V increases, the number of divisions decreases. However, since the distribution of abrasive grains on the circumference of an actual grinding wheel is irregular, in actual grinding, the abrasive grains 9 are Minute area drawn with diagonal lines 21,2
Intermittent grinding of 2 and 23, followed by micro areas 24, 25, 26 where the abrasive grains 27 are painted black and have irregular shapes.
Grinding is often done by irregularly intermittent grinding and applying a pulsed grinding force waveform. The actual grinding operation according to the present invention is performed by a combination of both the grinding mechanisms shown in FIGS. 8 and 9.

Cylindrical grinding, surface grinding, and internal grinding are performed by each abrasive grain group of abrasive grains 8, 9, 27, . . . that generate chips in the grinding mechanism as explained above.
Precision grinding becomes possible with the continuous pulse grinding force waveform shown in . At the same time that the grinding force becomes pulsed, the grinding heat also becomes pulsed, and the grinding temperature does not become too high. Also, clogging can be prevented.

The ground surface according to the present invention has an uneven chevron shape as shown in FIGS. 8 and 9. When an impact force with a short duration is applied to these fine uneven ridges, stress is concentrated, and in the case of ceramics, it promotes the generation of cracks and makes it easier to generate chips. The crack also effectively acts on only one of the minute mountains and does not affect the other mountains. That is, the present invention has solved the conventional problem that cracks remaining during cutting and grinding have been said to deteriorate the quality of the product, and has made precision grinding of ceramics possible. This grinding mechanism is effective even on soft and highly elastic rubber, making precision grinding possible.

The shape of the grinding wheel used for grinding by such a grinding mechanism is shown in FIGS. 10, 11, and 12.

In FIG. 10, a round rod having a diameter d and a length L vibrates ultra-longitudinal ultrasonic waves in the direction of an arrow 29 in a vibration mode 34 with a frequency f, a tip amplitude a _s and a 1/2 wavelength. A disc-shaped grindstone base metal with a narrow width b and a diameter D is provided at the central vibration node. This base metal and the round bar 28 are cut and molded as an integral part. A grindstone 33 is provided on the outer periphery of the grindstone base metal. In the central cross-sectional shape of the grinding wheel base metal
The length of ld = 1/2 (D-d) is the vibration mode 37 in which the outer periphery of the round bar 28 is the vibration node and the tip is the vibration antinode.
For example, as shown in the figure, it is designed based on the equation of vibration motion so that ultrasonic longitudinal vibration occurs in a 1/4-in vibration state. For example, using carbon steel S45C, the frequency f = 20
When it is Hz, when width b=10mm, ld=65mm.

The length l of the round bar can be designed using an artificial relational expression d = 50
When mm, l = 65 mm, therefore, L = 130 mm is determined, and the overall shape and dimensions are determined. Then, a radial ultrasonic vibration grinding wheel 32 is completed by providing tapered surfaces 30 on both ends of the round bar for attachment to the main shaft of a grinding machine. By taper-coupling this grinding wheel 32 to the main shaft of a grinding machine that vibrates vertically ultrasonically as shown in FIG.
Ultrasonic vibration with AR. The width b of the grindstone base metal at the vibration node where it contacts the round bar 28 must be made thin. When this width b increases, the disc base metal no longer vibrates ultrasonically. Actual grinding operations often require a wide grinding wheel. FIGS. 11 and 12 show radial ultrasonic vibration grinding wheels 38 and 39 that can handle such cases. In Fig. 11, the width b of the base metal at the vibration node is the 10th
Similarly to the figure, the width b' of the tip is set so that b'>b, and l'd is set based on the equation of motion so that the vibration state 36 shown in the figure is obtained according to the cross-sectional shape of b' x a'. This is a designed radial ultrasonic vibration grinding wheel. At this time, the whetstone width b′>b was used for 37.
l′d＜ld. Also, as shown in Figure 12, grinding wheel B
If B>b′>b, then l″d>l′d and the diameter becomes smaller.In this case, if we lengthen it to the length of (1/4λ+n1/2λ) wavelength (where n is an integer) Therefore, it has the characteristic that the width of the grinding wheel can be increased to compensate for the smaller diameter.In this way, a radial ultrasonic vibration grinding wheel of any shape can be manufactured.

Next, a cylindrical grinder that is an embodiment of the present invention is
This will be explained with reference to FIGS. 3 and 14.

Insert a sleeve 42 that spans two vibration nodes generated on a main shaft 41 with a 20KHz vertical ultrasonic electric distortion vibrator 40 attached to the tail and a radial ultrasonic vibration diamond grinding wheel 39 having the shape shown in FIG. 11 at the tip. The sleeve is fixed at a predetermined vibration node position by silver soldering, and the sleeve is supported by two high-precision rolling bearings 43 so that the main shaft can rotate with less friction. The rolling bearing 43 is fixed within the housing 44 and constitutes a headstock 53 for the grinding machine. A pulley 45 is attached to the sleeve 42, and a slip ring 46 is attached to this pulley 45. A brush 47 is brought into contact with a slip ring 46 with little friction. The brush 47 and the output terminal of the ultrasonic transmitter 48 are connected. The other end of this radial direction ultrasonic vibration diamond grinding wheel 35 has the same structure as the main shaft 56 for the grinding machine,
It is supported by the tapered surface of a main shaft 56 which is driven by a 20 KHz vertical ultrasonic electric distortion vibrator 55 and vibrates vertically with ultrasonic waves, having the same shape as the main shaft No. 57 for the grinding machine. Ultrasonic vibration energy is supplied to the vibrator 55 from the ultrasonic transmitter 51 through a brush and a slip ring. In this way, the grindstone can be driven by two vibrators, making it possible to perform heavy-duty grinding with higher precision.

As shown in Fig. 13, the end face of the grinding wheel vehicle is a flat surface, and the wheel is inserted between the main shafts of the headstocks 56 and 57 and fixed to the main shafts by pressing them against each other.As shown in Fig. 12, both main shafts are coaxial. There is a method of fixing by making only one side a tapered surface and providing a flat surface or a center hole at the other end in consideration of the degree of stability.

A three-phase induction motor 49 for rotating the main spindle is attached to the headstock 53, and the main spindle 41 is moved by the arrow 3 with a belt 51.
Rotate the grinding wheel 39 in the direction of
The speed should be 500 to 1000m/min. This headstock is attached to the grinding machine carriage 51. Attach the workpiece 2 to the chuck 56 of the grinding machine, indicate the other end with the sensor 58,
By rotating this in the direction of arrow 9 at a rotational speed V and sending the carriage 51 in the direction of arrow 57 at a feed speed S, the vibration frequency is 20KHz to 60KHz and the single amplitude is 6 to 60KHz.
Precision vibratory cylindrical grinding is performed using a diamond grinding wheel that vibrates ultrasonically in the radial direction at 15 μm.

Alternatively, as shown in FIG. 15, the grinding wheel may be fixed to the vibrating abdomen at the tip of one of the rotating main shafts.

The present invention enables precision cylindrical grinding of rubber products as well as ceramics. Other embodiments of the present invention include, in addition to cylindrical grinders, surface grinders, screw grinders, and cutting machines.

(Effects) An example of the effects of implementing the present invention will be described. Diameter 256 of SDC100 R85B with shape shown in Figure 13
mm, width 30mm diamond grinding wheel using a 20KHz vertical ultrasonic electric training vibrator 300W, frequency f = 20KHz,
Ultrasonic vibration in the radial direction with a radial amplitude ar = 12 μm, rotation at a grinding speed of V = 800 m/min, and pressureless sintered silicon nitride with a diameter of 20 mm and a length of 80 mm was applied at a workpiece speed of V = 5 m/min. Rotate it with
When grinding 0.5 mm in the radial direction to a finished diameter of 19 mm, we succeeded in reducing the processing time to 1/3 to 1/5 compared to conventional grinding methods that do not implement the present invention. For example, by grinding with a depth of cut of 0.3 mm, the accuracy of diameter machining can be kept within ±2 μm, which is an effect of improving accuracy. The effect of drastically reducing grinding noise was obtained.

In conventional conventional grinding, the grinding wheel surface strongly presses against the ceramic surface, emitting a strong grinding sound that proves that the grinding is being performed forcibly.In addition, the chips often catch fire and scatter sparks. However, according to the present invention, an epoch-making result can be obtained in that grinding can be carried out without stress and without generating heat.

Therefore, the effect of lengthening the life of the grinding wheel can be obtained. It causes less damage to the ceramic surface and can be precisely ground to within 2 to 3 μm, which is about the same as surface roughness.

[Brief explanation of the drawing]

Figure 1 is a model diagram explaining the conventional grinding mechanism.
Figure 2 is a model diagram explaining the vibration grinding mechanism, Figure 3
The figure is a model diagram explaining the superimposed vibration grinding mechanism.
The figure is a model diagram illustrating a grinding mechanism that applies a pulsed cutting force waveform by grinding only the area near the top of the uneven surface roughness. Figure 5 shows a conventional grinding mechanism in which one abrasive grain grinds. Area and depth of cut
GC is modeled, FIG. 6 is a diagram showing the grinding force waveform at that time, and FIG. 7 is 1 in the present invention.
FIG. 8 is an explanatory diagram showing the pulsed grinding force waveform at that time. FIG.
10 to 12 are partially cutaway front views of each grinding wheel used in the present invention, and FIG. 13 is an embodiment of the present invention. FIG. 14 is a side view of FIG. 13, and FIG. 15 is a front view of a grinding wheel fixed to the tip of one of the rotating main shafts. 3... Grinding speed, 6, 10, 20... Pulse grinding force waveform, 8... Intermittent pulse grinding force waveform, 13... Abrasive grain 1
Depth of cut per blade, 16... Radial ultrasonic vibration of grindstone, 21, 22, 23, 27, 28, 29
...Intermittent fine grinding area, 35,41,42...Radial ultrasonic vibration grinding wheel, 45,46...Ultrasonic vibration main shaft, 51...Ultrasonic oscillator, 43,55...Ultrasonic longitudinal vibrator, 56,57...Super Headstock for sonic vibration grinding machine.

Claims (1)

[Claims] 1. The hole surface with inner diameter d is used as a vibration node at the vibration node that occurs in the center of a round bar with a diameter d that resonates in a vertical ultrasonic vibration state with a natural frequency f and a length of 1 1/2 wavelength. Natural frequency f with the outer peripheral surface of diameter D as an antinode
A radial ultrasonic vibrating grindstone with a round bar is created by providing a disk with a uniform thickness or thicker near the outer circumferential surface that resonates only in the radial direction, and providing groups of abrasive grains on the outer circumferential surface and side surfaces of the disk. wheel, and the grinding wheel is at least two
A vertical ultrasonic vibrator with a natural frequency f is attached to the tail, which has vibration nodes at various points and vibrates vertically with a natural frequency f.It is fixed to the vibrating abdomen at the tip of the rotating main shaft and rotated, and pulse grinding is performed. A vibration grinding machine using an ultrasonic vibration grinding wheel that generates a force waveform to make chips finer.