JPS6240123B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to tools that are used by rotating them, such as drills, reamers, milling cutters, end mills, grinding wheels, and lapping rods in lapping processing using free abrasive grains. The present invention relates to a rotary cutting/grinding method and apparatus for performing cutting/grinding while vibrating by superimposing low frequency vibration and ultrasonic vibration in the circumferential direction of the machine.

(Prior Art) Vibration cutting is a process in which a cutting tool is vibrated in the cutting direction at a frequency f and a single amplitude a, and a pulsed cutting force waveform is applied at a cutting speed where υ is less than 2πaf. If this cutting condition of υ<2πaf is satisfied, the vibration frequency can be as low as about 100 Hz, or as high as 20 KHz or higher in the ultrasonic range.

Below, vibration cutting at a low frequency of about 100Hz is performed for 100 seconds.
Hz vibration cutting, vibration cutting with a high frequency of about 20KHz is called 20KHz vibration cutting and will be explained. In this vibration cutting, if the cutting length in one cycle of vibration of the tool is l _T , it is expressed as l _T =υ/f. In vibration cutting, the size of this l _T affects the cutting mechanism,
Affects the cutting effect. When l _T is shortened, the chip thickness becomes a flow-type chip, which improves the vibration cutting effect. When l _T is made long, the chip thickness becomes thicker, and the vibration cutting effect decreases.

Due to the high frequency of 20KHz vibration cutting,
It has the advantage of shortening l _T , improving machinability, and smoothing the finished surface roughness. However, in order to convert electrical vibration energy into mechanical vibration energy, an ultrasonic vibrator is used, and its minute amplitude is expanded with an amplitude amplifying horn, and a cutting tool is attached to the tip of the ultrasonic vibrator. The cutting tool vibration system is manufactured so that the vibration frequency is f, so that the vibration direction of the tool tip is in the same direction as the cutting direction, and the vibration cutting is performed by attaching it to the tool rest. For example, heavy cutting where the cutting area is large and the cutting load resistance increases due to the low output, or heavy cutting where the cutting load resistance is large due to the strong mechanical properties of the workpiece, such as hardened steel or ceramics. In some cases, the vibration amplitude may be drastically reduced or the vibration may stop, resulting in the disadvantage that the expected vibration cutting mechanism may not be achieved.

For this 20KHz vibration cutting, 100
Hz vibration cutting has the advantage that even during heavy cutting that can withstand cutting load resistance of several hundred kilograms, the regular vibration state of the tool edge is not disturbed and the tool vibrates to form a vibration cutting mechanism. be.

However, on the other hand, since the vibration frequency is low, l _T becomes long, and it is not possible to generate thin chips as can be obtained with 20KHz vibration cutting. In addition, its surface roughness exhibits a slightly uneven surface in the form of an "amida pattern" with long intervals of l _T , and has the disadvantage of resulting in a rough finished surface that is inferior in surface roughness compared to a 20KHz vibration-cut surface. Ta.

(Purpose) The purpose of the present invention is to combine 20KHz vibration cutting and 100Hz vibration cutting to create a vibration cutting/grinding mechanism that utilizes the strengths of both to further improve the vibration cutting/grinding effect. .

(Embodiment) FIG. 1 shows a first embodiment of the apparatus of the present invention when the method of the present invention is implemented for reaming. Reference numeral 1 denotes a reamer, which is provided at the tip of an amplitude enlarging horn 3 for enlarging the amplitude of the torsional ultrasonic transducer 2 . This is called a torsional ultrasonic vibration reamer. Flange portions 4 and 5 are provided at vibration nodes generated in this vibration system, and are fitted and fixed to the inner surface of the sleeve 6 without play.

This sleeve 6 is supported by rolling bearings 8 and 9 provided at both ends of the headstock 7 so that it can rotate smoothly and with high precision. The tail end of the sleeve 6 is provided with a flange 10. Spindle mount 1
A stepping motor fixing column 12 is provided at the tail end of the stepping motor 15, and the stepping motor is mounted so that the central axis of rotation of the stepping motor 15 coincides with the central axis of the torsional ultrasonic vibration system reamer. The flange 11 attached to the rotating shaft and the flange 10 provided on the sleeve 6 are screwed together. The sleeve 6 is further provided with slip rings 16 and 17,
The slip ring contacts brushes 18 and 19 with little friction, allows the slip ring to rotate smoothly, and enables excitation current from an ultrasonic oscillator 20 to be supplied to the rotating torsional vibrator 2 without loss. This device causes torsional vibration in the direction of arrow 23 at a high frequency in the ultrasonic range of 20 KHz or higher. If a longitudinal vibrator is used instead of a torsional vibrator, the reamer will vibrate longitudinally in the axial direction. By adjusting the clearance angle of the reamer cutting edge, this vertical vibrator can also be used and the present invention can be carried out.

The stepping motor 15 is driven by a control device 22 and a driving unit 21.
By repeatedly applying 11 forward pulses, 1 resting pulse, 1 backward pulse, and 2 resting pulses by the control device 22, the reamer vibrates at a frequency of 140 Hz in the direction of the arrow 24. It rotates in the direction of 25 at a rotation speed of 150 rpm.

The apparatus described above is fixed on the lathe carriage 14 by tightening screws, the workpiece 27 is attached to the chuck 26 of the lathe main shaft, and the carriage 14 is automatically fed to perform superimposed vibration reaming.

Further, in order to improve the machining shape accuracy, the workpiece 27 may be rotated at an extremely low speed in the direction of the arrow 28, and a center reamer may be used instead of a straight reamer.
By attaching a drill or an end mill to the tip of the amplitude-enlarging horn 3, superimposed vibration reaming, superimposed vibration drilling, and superimposed vibration milling can be performed.

At this time, if the feed rate becomes large, the cutting direction cannot be approximated as the circumferential direction, so instead of supporting the sleeve 6 with rolling bearings 8 and 9, threads are provided on the outer periphery of the sleeve 6 and screws are provided on the headstock. The flanges 10 and 11 are connected with a pin so that they can slide in the axial direction.
The vibration direction of No. 4 is set as the lead angle direction of the screw, and is made to coincide with the cutting direction by the feed of the carriage. Also, a vibrator 2, a vibration amplifying horn 3, and a tool 1.
The ultrasonic vibration system is also implemented by combining longitudinal vibration and torsional vibration so that the direction of the ultrasonic vibration is the same as the cutting direction.

By attaching a cutting tool to the tip of the amplitude-enlarging horn 3, superimposed vibration boring can be performed. In addition, the device allows for outer circumferential turning, by rotating the workpiece in the direction of arrow 28, and using the cutting tool at arrows 23 and 24.
It is possible to perform ultra-precision turning of difficult-to-cut materials by vibrating in the direction of .

FIG. 2 shows a second embodiment of the apparatus of the present invention for carrying out the method of the present invention for lapping. 29 is a lap and is made of brass or cast iron depending on the material of the workpiece. The length of the shape is such that it resonates at 1/2 wavelength with the natural frequency of the torsional oscillator. The tip has the same shape as the center, and a tapered portion is provided at the tail portion of the other end to facilitate attachment and detachment of the lap that wears out, and is tapered and coupled to the tip of the torsional vibration system horn 3.

A specific device for applying ultrasonic vibrations and low frequency vibrations as indicated by arrows 23 and 24 to this lap can be implemented by a device similar to that shown in FIG.

The spindle mount 13 to which the headstock 7 is attached is fixed on a roller guide 34 provided on a lathe bed guide surface 35 so that it can slide in the axial direction of the lathe spindle with little friction. A steel wire 32 is attached to the main shaft mount 13, and a dead load 33 is applied to one end of the steel wire via a pulley 31. By applying the pressing force 36 to the lap 29 in this manner, a lapping process using the abrasive grains 30 using a constant load method is performed. Workpiece 2
7 is attached to the chuck 26 provided on the main shaft of the lathe. Further, in order to improve the accuracy of the processed shape, the present invention may be implemented by applying rotational motion in the direction shown by the arrow 28.

Note that arrow 2 is moved by the stepping motor 15.
Although it has been described that vibration is made in the direction of arrow 25 and rotational movement is made in the direction of arrow 25, the present invention uses an AC or DC motor in addition to this stepping motor and controls it to move in the direction of arrow 24. This can be carried out by vibrating it and rotating it in the direction of the arrow 25.

(Effects) In the present invention, a cutting tool or a grinding tool is subjected to torsional ultrasonic vibration in the circumferential direction at a high frequency in the ultrasonic vibration range, and at the same time, a stepping motor, AC or DC motor is used to simultaneously vibrate the cutting tool or grinding tool in the circumferential direction. Since the cutting/grinding process is performed by rotating the tool while vibrating, it is possible to shorten the cutting length in one cycle of tool vibration, which would be long with a 100Hz vibration cutting mechanism alone, by using a 20KHz vibration cutting mechanism. This reduces tool rake face friction, tool flank friction, and other frictional resistance, reduces chip thickness, reduces cutting and grinding resistance, reduces dynamic behavior of the workpiece, and improves machining accuracy. can be improved. On the other hand, the surface roughness is reduced to 100Hz, which has a large vibration amplitude, because the cutting length in one cycle of tool vibration, which would be long with only a 100Hz vibration cutting mechanism, is divided into shorter lengths using a 20KHz vibration cutting mechanism.
Tool vibration 1, which is one of the characteristics of vibration cutting
In addition, the longer the distance between the chips and the tool rake face during the cycle, the greater the lubrication and cooling effect of the cutting fluid on the cutting edge. It exhibits geometric roughness and enables precision machining.

In addition, the cutting edge of a rotary cutting/grinding tool, which vibrates by adding low-frequency vibration energy of about 100 Hz to high-frequency ultrasonic vibration energy of about 20 KHz, is not regular when only ultrasonic vibration energy is used. Vibration cutting and grinding processes have the drawback that precision machining is difficult because the ultrasonic vibration state is disturbed by the cutting/grinding resistance load and excessive cutting/grinding resistance is applied, but by implementing the present invention, powerful 100Hz By adding low-frequency vibration energy with a low frequency, the problems of the past have been eliminated, cutting and grinding resistance on the workpiece has been reduced to almost zero, its dynamic behavior has been completely eliminated, and machining accuracy has been significantly improved. can be improved.

The present invention can perform precision machining using rotary cutting/grinding tools such as drills, reamers, milling cutters, end mills, grinding wheels, and laps using loose abrasive grains as described above.

Next, an example of the effect of implementing the present invention will be specifically explained. A center hole was drilled in the center of an S45C workpiece with a diameter of 13 mm and a length of 40 mm using a center drill with a diameter of 2 x 60. A lap pressure of 2 Kg/cm ² was used, abrasive grain WA#800 was used, and light oil was used as the lap liquid with a concentration of 70. %wt, the lap is cast iron FC20, forward pulse; 2 pulses,
Rest pulse; 1 pulse, backward pulse; 1 pulse,
Rest pulse: 100Hz vibration and 1 pulse
This paper compares the superimposed vibration wrapping effect of the present invention by superimposing a rotational motion of 100 rpm with a torsional vibration frequency of 30.2 KHz and an amplitude of 3 μm in the ultrasonic range with conventional vibration wrapping in which the ultrasonic vibration is stopped. The features of the invention will be explained. Comparison will be made based on the roundness and surface roughness of the machined center hole. Roundness of center hole machined with center drill 10
With conventional vibration wrapping, the roundness remains at about 8 μm even after 5 minutes, and the roundness does not tend to improve much even if wrapped more than that. A highly accurate center hole with a roundness of 4 μm can be precisely machined in just about 1 minute.

As for surface roughness, center drill 15
With conventional vibration wrapping, the surface roughness of μmRmax remains at around 8 μmRmax even after processing for 5 minutes.
In contrast to the tendency of not being able to achieve a center hole surface of 8 μmRmax or more even after 5 minutes of machining, by implementing the present invention, it is possible to achieve a center hole surface of about 3 μmRmax in just 1 minute, and a smooth center hole surface of 2 μmRmax after 2 minutes of machining. Precision processing is possible.

This is because the cutting resistance of the abrasive grains stuck to the lapping is drastically reduced by the cutting mechanism using the superimposed vibration cutting mentioned above.For this reason, when lapping is pressurized with a constant load, the amount of processing per unit time increases. Shape accuracy and surface roughness from pre-processing can be corrected in a short time, making precision processing possible. In addition, by adding ultrasonic vibration, the friction coefficient of the contact surface is about 0.02 to 0.03, which is the dynamic friction coefficient, so the friction resistance of each contact surface in conventional wrapping can be uniformly reduced, improving machining efficiency and machining accuracy. It is helping to improve the Furthermore, the addition of ultrasonic vibration makes use of the chip-collecting effect in which chips move quickly from the vibration antinode toward the vibration node.

By implementing the present invention during machining using a constant load method using free abrasive grains and rotating laps, it is possible to achieve the effect of dramatically improving machining efficiency and making ultra-precision machining possible. It will be done.

Further, similar effects can be obtained even in the case of machining with a grinding tool using fixed abrasive grains.

[Brief explanation of the drawing]

FIG. 1 is a cutaway front view of a main part of an apparatus for carrying out the method of the present invention for reaming, and FIG. 2 is a cutaway front view of a main part of an apparatus for carrying out the method of the present invention for wrapping. 1...Reamer, 2...Torsional vibrator, 15...
Electric stepping motor, 20... Ultrasonic oscillator, 23... Ultrasonic vibration direction, 24... Low frequency vibration direction, 29... Lap, 30... Abrasive grain.

Claims (1)

[Claims] 1. Applying low-frequency circumferential vibration and rotational motion generated by a stepping motor or AC or DC motor to a rotating spindle to which a tool is attached, and further applying torsional ultrasonic vibration to the tool. A superimposed vibration rotary cutting/grinding method for cutting and grinding. 2. Cutting in which an electric or electro-hydraulic stepping motor is used to give a low-frequency vibration and rotational motion of the tool in the cutting direction, and the main shaft is driven by an ultrasonic vibrator in the cutting direction of the tool tip. A tool or a grinding tool vibration system is fixed using the vibration nodes generated in the vibration system, and a low-frequency vibration waveform generated by a stepping motor at the tool cutting edge provided near the tip vibration antinode of the vibration system. A superimposed vibration rotary cutting/grinding device which gives a vibration of a vibration waveform superimposed with a vibration waveform of a high frequency in the ultrasonic range.