JPH0575560B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention applies ultrasonic vibration or low frequency vibration to a tool, and further applies ultrasonic vibration to a ceramic workpiece to machine a precision hole in ceramics. This article relates to a vibration cutting drilling machine for precision hole machining in ceramics.

(Prior Art) Nowadays, there is a strong desire for anyone to be able to easily and easily drill holes in ceramics in a short time with the same feeling as drilling holes with a conventional ferrous metal head drill. On the other hand, as the quality of ceramic materials improves and their mechanical strength increases day by day, ceramics are becoming increasingly difficult to cut. Therefore, the current state of the art is that the conventional high-speed cutting and grinding methods alone are no longer suitable for precision hole machining technology. As a technique to deal with this, the present inventor focused on the fact that ceramics are weak in tensile strength, and applied ultrasonic vibrations to the ceramics to generate vibrational stress within the ceramics that cannot be ignored relative to the tensile strength. We proposed a precision machining technology that improves the machinability of ceramics by reducing the It is primarily suitable for threading, grooving and flat machining of cylinders and their cylindrical surfaces. After that, it remained unclear whether it could be applied to the core drill machining mechanism, which is one of the basic drilling tools for cylindrical, flat, and hole drilling.

On the other hand, the present inventor has already proposed a technique for drilling a hole by rotating a tool at high speed and subjecting it to twisting or longitudinal ultrasonic vibration. Furthermore, the inventor has also developed a hole machining method in which low frequency vibration is superimposed, and the technology and effects thereof have been announced.

(Problems to be Solved by the Invention) However, the above-mentioned prior art has a problem in that precision hole machining in ceramics cannot be performed in the same way as conventional hole machining in metal.

(Means for Solving the Problems) The present invention aims to solve the above problems.

Today, the main tool used for drilling holes in ceramics is the so-called core drill, which has a pipe-shaped tool tip with a group of diamond abrasive grains. Drilling machines involve diamond abrasive grains on the end face of the pipe.

For precision machining of ceramics, rubber, and metals, especially ceramics, it is important to make the cutting length of each diamond abrasive grain ultra-fine and to make the chips ultra-fine. We will consider how the diamond abrasive grains at the tip of the pipe-shaped core drill can miniaturize the cutting length to enable cutting. The first thing to realize is to increase the rotational speed of the core drill, as is done in the prior art. That is, the core drill is rotated at high speed.

Next, the core drill is vibrated ultrasonically to subdivide the cutting length. One method is to cause a core drill to vibrate torsionally with ultrasonic waves, and give the relationship v<2πaf between the frequency f, amplitude a, and cutting speed v to cut the cutting length. There are two methods: the cutting surface is rotated by vertical ultrasonic vibration, the cutting surface is made into a finely uneven surface, and the slope is cut into small pieces to cut the cutting length. Both methods involve drilling a hole by rotating a core drill while applying ultrasonic vibrations.

Furthermore, by making this headstock vibrate at a low frequency in the axial direction of its rotating spindle and creating an intermittent pulse waveform that greatly shreds the cutting length, we ensure that the ultrasonic vibration produces a microscopic shredding effect on the cutting length. There is a method using a superimposed vibration cutting mechanism to achieve this. Furthermore, there is a method of applying ultrasonic vibration to ceramics to apply vibration stress to reduce the apparent mechanical strength and improve the machinability of ceramics.

Precise drilling of fine ceramics is made possible by superimposing and combining the above methods for drilling. However, for ceramics with low hardness, the application of low frequency vibration may be omitted in some cases. In this way, rotational kinetic energy is applied to the tool, ultrasonic vibration energy is applied to the tool and workpiece, and low-frequency vibration energy is further superimposed, giving all the energy to cut the cutting length and drill holes. Therefore, it becomes possible to perform precision drilling in fine ceramics, which has a hardness close to that of diamond, which cannot be processed using rotational kinetic energy alone. That is, the core drill is vibrated ultrasonically using an electric or magnetic oscillator, rotated at high speed, and its headstock is vibrated at low frequency in the direction of the spindle, and the feed mechanism is such that it can feed at a constant speed. The drilling machine is equipped with a vertical vibration system vise for ceramic machining, in which a ceramic workpiece is attached to the tip of a horn that vibrates vertically ultrasonically using an electric or magnetic oscillator, on the drilling machine table. By drilling with such a drill press, precision hole machining in fine ceramics can be realized.

Next, a detailed description will be given based on the illustrated embodiment. A core drill 1 is taper-coupled to the tip of a vibrating main shaft 3 driven by a vertical electric strain vibrator 2 attached to the tail, and fixed so as to be freely attachable and detachable. A bearing 5 is attached using a sleeve 4 spanning two vibrating lines generated on a vibrating main shaft 3, so that the vibrating main shaft can rotate within a head stock 6 with less friction and less shaking without affecting its vibration state.

An electric motor 7 is attached to the headstock 6, and a pulley fixed to the sleeve by a belt 8 is used to rotate the vibrating main shaft in the direction of an arrow 20. A slip ring 9 is attached to the pulley, and the excitation voltage from the opposing brush 10 is supplied to the rotating electric oscillator 2. Then, the tip of the core drill is subjected to ultrasonic longitudinal vibration in the direction of arrow 11 at frequency f and amplitude a. The headstock 6 is fixed on a guide roller 12 guided by steel balls provided on a drilling machine column 21. It is then coupled to an electro-hydraulic vibration drive device 16 via a connecting rod 13. Using this electro-hydraulic vibration device 16, the oil pressure from the hydraulic device 14 is alternately switched by the control device 17 using the servo valve 15, and the core drill is vibrated in the direction of the arrow 18 at a frequency of about 2 to 200 Hz. vibrate at frequency F and amplitude A. Drilling is performed by giving commands to the control device to apply vibration and feed at the same time. A ceramic workpiece 22 is attached to the tip of the amplitude enlarging horn 23. A vertical electric strain vibrator 28 is attached to the lower end of the tail. A sleeve 24 is attached to the vibration node of the horn and fixed to a bypass 25 on a drilling machine table 26. The workpiece ultrasonic oscillator 27 causes the ceramics workpiece 22 to ultrasonically vibrate in the direction of the arrow 26 with an ultrasonic frequency f _w and an amplitude a _w .

In this way, the ultrasonic oscillator 19, the ultrasonic oscillator 27, the hydraulic device 14, and the control device 17 are operated, the core drill is rotated while being vibrated ultrasonically, and the core drill is vibrated at low frequency to move the feed S at the arrow 29.
Precision hole machining according to the present invention can be carried out by applying the force in the direction of . At this time, a device for rotating the workpiece can also be added. A torsional vibration system that vibrates the core drill in the circumferential direction by converting the vertical vibrator 2 into a torsional vibrator, designing and manufacturing the vibration system into a vibration system that resonates at the natural frequency of the torsional vibrator, and assembling it. It can be done. At this time, the rotational speed is set to v<2πaf, and the longitudinal vibration core drill is used for rough finishing, whereas the torsional vibration core drill is used for finishing.

Furthermore, when performing ultra-precision machining by reducing the depth of cut and feed, the machining resistance will also be reduced, so the low frequency vibrations F and A are stopped and finishing machining is performed using only the ultrasonic vibrations f, a, f _w and a _w . Implement. Other conditions for adding vibration are selected depending on the machining accuracy and mechanical properties of the ceramics.

The drilling machine of the present invention is capable of applying longitudinal or torsional ultrasonic vibrations and low-frequency vibrations singly or in combination to the core drill, and is also able to apply longitudinal ultrasonic vibrations to ceramics, thereby improving machining efficiency and machining accuracy. The present invention is characterized in that it is a drilling machine exclusively for ceramics that is configured with all the functions that allow precision hole drilling in ceramics by selecting each vibration mode according to the processing purpose.

The present invention is a cutting machine with fixed diamond abrasive grains.
In addition to grinding tools, it is applicable to free diamond abrasive tools and similar tools.

(Effects) Next, specific implementation effects obtained by implementing the present invention will be described. The effect of implementing the present invention when drilling into a square piece of zirconia with a thickness of 5 mm and a side length of 5 mm using a core drill with a diameter of 4 mm will be described.

#100/120 diamond core drill ultrasonic frequency f = 20.7 KHz, amplitude a = 18 μm, low frequency dynamic frequency F = 50 Hz, amplitude A = 15 μm, feed S = 3 μm/
rev, rotation speed = 1000 rpm, zirconia ultrasonic frequency f _w = 20 KHz, amplitude a _w = 17 μm, by implementing the present invention as dry cutting, machining efficiency can be improved by ultrasonically vibrating zirconia and This is about 1.5 times as much as when vibrating, about 2.4 times as much as when zirconia is ultrasonically vibrated and only low frequency vibrations are applied to the core drill, and about 4.5 times as much as when only ultrasonic vibrations are applied to zirconia.

If the core drill is simply rotated and fed into a stationary zirconia workpiece, the core drill will wear out and wear out severely, and the cutting edge will become dull, making it impossible to drill the hole. Compared to this phenomenon, the effects of the present invention are epoch-making, as can be seen from the above numerical values.

In addition, the elastic vibration of the cutting edge of the core drill when biting is eliminated, the edge surface sagging and chipping are reduced when biting, the roundness is less than 10 μm, the straightness is less than 2 μm, the surface roughness is less than 15 μm, and the diameter of the hole is increased. We succeeded in keeping the margin within ±0.01mm, reducing droop and chipping at the end of the cut, and successfully drilling holes efficiently.

Since the chips are shredded, they can be discharged smoothly, preventing abnormal friction phenomena in the core drill, extending the life of the core drill, and contributing to reducing machining costs.

As a technique for efficiently drilling holes in ceramic materials, a core drill is vibrated ultrasonically (vertical ultrasonic vibration or torsional ultrasonic vibration), rotated, and then vibrated at low frequency in the axial direction, thereby applying ultrasonic waves to the ceramic workpiece. A method for rough machining by vibrating and cutting into pieces and a drilling machine for the same were devised and explained as above.

In the case of drilling holes in ceramics, a cutting mechanism that efficiently discharges chips and cuts burrs inevitably produces microscopic cracks that remain on the machined surface. In order to remove these minute cracks, the low-frequency vibration is stopped, only ultrasonic vibration is applied, the depth of cut is made small, and the amount of feed is also made small to finish the ultrasonically vibrating ceramic. Since the depth of cut and feed are small, the resistance is also small, so low frequency vibration energy is not required. This also enables precision hole machining. for example,
In this case, the margin for expansion of the hole diameter is minimized, and the effect of making it almost equal to the diameter of the core drill used can be obtained.

When smoothing the surface roughness, only low-frequency vibrations are applied to ultrasonically vibrating ceramics.
Finishing is performed by applying fast feed. When you want to finish the ceramic with minimal cracks remaining on the surface of the ceramic, ultrasonic vibration and low-frequency vibration are combined and superimposed on the core drill to vibrate only the core drill.
Ceramics are finished without applying ultrasonic vibrations.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view of essential parts of a first embodiment of the present invention. 1...Core drill, 2...Vertical electric distortion vibrator, 3
...Vibration spindle, 6... Headstock, 19, 27... Ultrasonic oscillator, 22... Ceramics workpiece.

Claims (1)

[Claims] 1. A headstock that provides high-speed rotation and feed while applying ultrasonic vibrations at high frequencies in the ultrasonic range and/or low-frequency vibrations at lower frequencies in the axial direction of a tool for drilling holes in ceramics, and A vibration cutting drilling machine for precision hole machining in ceramics, which is equipped with a table that applies ultrasonic vibrations at a high frequency in the ultrasonic range in the axial direction of a workpiece.