JPH07214416A - Turn broaching method and device therefor - Google Patents

Abstract

PURPOSE:To eliminate chatter of tip so as to stabilize cutting by computing the cutting conditions which reduce cutting resistance when occurrence of chatter is distinguished and executing according to the NC program in which cutting by the next cutter is restored. CONSTITUTION:The effect that cutting conditions affect on cutting resistance measured by a sensor 51a for a workpiece which is being machined currently is analyzed. Whether chatter occurred during machining by means of a cutter used immediately before the current cutting or not is distinguished by a chatter judgement computing unit 52b. If chatter occurred, the cutting conditions which reduce cutting resistance are computed by a cutting condition determining computing unit 52c. The computed cutting conditions are restored in an NC program. Cutting by the next cutter is done by the NC program which is restored in an NC section 53.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turn broaching method and apparatus, and more particularly to a turn broaching method and apparatus capable of preventing chattering during cutting.

[0002]

2. Description of the Related Art Conventionally, turn broaching has been performed in which the outer shape of a shaft-shaped work is cut while rotating the shaft-shaped work around its axis. FIG. 1 shows a cutting model in this case. This model is expressed by the following equation of motion i.e. ^{m (d 2 x / dt 2} ) + c (dx / dt) + kx = R (t) ── (1). Where R (t) is the cutting resistance, k is the spring constant (the rigidity of the part of the turn broaching machine and the work 12 that is involved in vibration), and c is the part of the turn broaching machine and the work 12 that is involved in the vibration. , M is a mass of a portion of the turn broaching machine and the work 12 that is involved in vibration, and x is, for example, the x coordinate of the center position of the work 12. In addition, 11 is a broach blade of a turn broaching machine. Here, the “chatter” is a state in which the position x that adversely affects cutting is increased, and the value of x at that time is regarded as the amount of chatter (chatter amount).

Therefore, when the cutting resistance R (t) becomes large and the rigidity k of the turn broaching machine and the work 12 that contributes to vibration cannot withstand the cutting resistance R (t),
Chattering will occur. Therefore, in order to suppress chatter, that is, in order to reduce x, it is understood that k may be increased or R (t) may be decreased according to the equation (1). Therefore, conventionally, as a method of increasing k, the mechanical rigidity is increased and the rigidity of the work 12 is increased by adopting a work rest. Further, when chattering occurs, either the machining is finished to the end for the time being, or the machining conditions are interrupted and the cutting conditions are reexamined and reset so that R (t) becomes smaller, and then recutting is performed.

[0004]

However, in the above-mentioned method of increasing k, there is a problem in that the cost is increased due to the increase in size and complexity of the equipment. Further, when the processing is interrupted or the cutting conditions are set again after the processing is finished and the processing is performed again, the method of reducing R (t) described above has a problem that the processing time becomes long. The present invention provides a processing method and a processing apparatus that do not require enlargement of equipment and increase the processing time. In the case of turn broaching, cutting is performed intermittently by using a plurality of blades one by one. Therefore, if chattering occurs during the processing of one blade, it should be possible to learn it and perform the processing under the processing conditions that will not cause chattering when processing with the next blade. The present invention aims to achieve the above-mentioned object by focusing on this point.

[0005]

In order to solve the above-mentioned problems, the structure of the first invention of the present application is to control a broach having a plurality of blades and a work based on an NC program, thereby In the turn broaching method of cutting the work by using one by one one by one, before the start of the cutting step by the next blade, (1) the step of measuring the cutting resistance, and (2) the measured cutting resistance and its From the cutting conditions at the time, a step of analyzing the relationship between the cutting conditions and the cutting resistance, and (3) a step of determining whether chatter has occurred during cutting by the blade used immediately before, (4) A step of calculating a cutting condition for reducing the cutting resistance based on the analysis result of the step (2) when the occurrence of chatter is discriminated in the step (3), and re-storing it in the NC program. And perform the cutting with the next blade as described above ( It is to be executed according to the NC program re-stored in the step 4).

Further, the structure of the second invention is to increase the cutting speed in the step (4) in the structure of the first invention. Further, the structure of the third invention is to reduce the cutting width in the step (4) in the structure of the first invention. Furthermore, the configuration of the fourth invention is
In the configuration of the first invention, in the step (4),
To reduce the depth of cut. Furthermore, the structure of the fifth invention is to increase the rake angle of the blade in the step (4) in the structure of the first invention.

Further, the structure of the sixth invention is a turn broaching machine comprising a broach having a plurality of blades and an NC controller for controlling the broach and the work based on an NC program. Cutting resistance measuring means, b. Means for analyzing the relationship between the cutting conditions and the cutting resistance based on the measured cutting resistance and the cutting conditions at that time; and c. Means for determining the presence or absence of chatter; d. Means for detecting the completion timing of cutting by one blade; e. When the detection means of d detects the completion timing, it is determined whether the occurrence of chatter is determined by the determination means of c during processing by the blade cut immediately before, and the occurrence of chatter is determined. This is to add NC program correcting means for calculating a cutting condition for reducing the cutting resistance based on the analysis result of the analyzing means in the above-mentioned b and re-storing the cutting condition in the NC program.

[0008]

According to the structure of the first aspect of the present invention, the influence of the cutting conditions on the cutting resistance for the workpiece currently being processed is analyzed by the steps (1) and (2). Here, the cutting conditions are parameters such as cutting speed, cutting width, cutting depth, and rake angle. For example, there is a qualitative relationship in which the cutting resistance increases as the cutting width increases, but the quantitative relationship established under the actual machining conditions can be analyzed in the steps (1) and (2). In addition, in the step (3), it is determined whether or not chatter has occurred during processing by the blade used immediately before. Then, in the step (4), if chatter has occurred, the cutting condition for reducing the cutting resistance is calculated. At this time, the analysis result is used. For example, in the case of a method of correcting the cutting width, a cutting resistance that does not cause chatter is obtained by using the relationship of how small the cutting width is and how much the cutting resistance is reduced. The width is calculated. Then, the calculated cutting conditions are stored again in the NC program.

The cutting condition thus calculated is NC
Since it is stored again in the program, the cutting with the next blade will be cut under the cutting resistance that does not cause chattering, and the occurrence of chattering can be prevented. If chatter does not occur during processing with the blade used immediately before,
The cutting conditions at that time are maintained. Further, as shown in the configurations of the second to fifth inventions, the cutting resistance is to increase the cutting speed, decrease the cutting width, decrease the depth of cut, or increase the rake angle. The cutting conditions to be reduced can be calculated from this relationship.

Since increasing the cutting speed can be dealt with by simply changing the processing condition software, new hardware is not required. Further, if the cutting width is reduced, the amount of cutting chips is reduced and the chips are easily broken. Therefore, it is possible to prevent the chips from being caught in the work or the like, and the chips are further reduced, which facilitates handling. Further, when the cutting amount is reduced, the chips are thinned and easily broken, so that the chips can be prevented from being caught in the work or the like. Further, when the rake angle of the blade is increased, the chips are easily curled and easily broken, so that the chips can be prevented from being caught in the work or the like, and the chips are further reduced, which facilitates the handling. Furthermore, according to the turn broaching device having the configuration of the sixth aspect of the present invention, the above-mentioned turn broaching method is automatically carried out, and the processing can be continued without causing chattering.

[0011]

Embodiments of the present invention will now be described with reference to FIGS. FIG. 1 shows a cutting model of turn broaching according to the present invention. Therefore, the above formula (1) is applied to the turn broaching process of the present invention. FIG. 2 is a schematic front view of the turn broaching machine according to the first embodiment of the present invention,
FIG. 3 schematically shows the right side surface of the turn broaching machine.
2 and 3, a broach holder / Z-axis table 21, an X-axis table 22 and a Y-axis table 23 are disposed on a bed 29 so as to be movable in their respective directions.
The broach holder / Z-axis table 21 holds the broach 20, and holds the Z-axis servomotor 21a and the Z-axis ball screw 2
It can be moved in the Z-axis direction by 1b, and reciprocates once for each cutting of the work 26. The X-axis table 22
It can be moved in the X-axis direction by the X-axis servo motor 22a and the X-axis ball screw 22b, and the cutting place of the work 26 can be changed.

Further, the Y-axis table 23 can be moved in the Y-axis direction (cutting direction) by a Y-axis servomotor 23a and a Y-axis ball screw 23b. The work (camshaft, crankshaft, etc.) 26 is rotatably fixed by a chuck 24b and a tailstock 24c. The rotational force of the spindle motor 24 is reduced by the speed reducer 24a to rotate the work 26 supported by the chuck 24b and the tail stock 24c. The sensor output of the broach holder / Z-axis table 21 is applied to the control circuit 27, and the control circuit 27 controls the NC controller 28. Furthermore,
The NC controller 28 uses the Z-axis servomotors 21a, X
The axis servo motor 22a, the Y axis servo motor 23a, and the spindle motor 24 are numerically controlled (NC control).

With the above construction, when the spindle motor 24 rotates the workpiece 26, the NC controller 28 controls the X-axis servo motor 22a and the Y-axis servo motor 23a to move the X-axis table 22 and the Y-axis table 23. By doing so, the work 26 is moved to a predetermined position. After that, the NC controller 28 controls the Z-axis servomotor 21a to lower the broach holder / Z-axis table 21 to lower the broach 20 and start cutting the workpiece 26. When the broach 20 finishes passing the workpiece 26 while cutting it, the cutting is finished. At this time, when chatter occurs in the broach (having a tip as a blade) 20, the output of the chatter sensor (not shown) (see FIG. 7) is applied to the control circuit 27.

FIG. 4 shows a schematic front view of a rotary cut type turn broaching machine according to a second embodiment of the present invention.
Shows an outline of the right side surface of this rotary cut type turn broaching machine. 4 and 5, a broach holder 31, a Y-axis table 32, and an X-axis table 33 are rotatably or movably arranged on a bed 38. The broach holder 31 holds the broach 30 and is rotated by the C-axis electric motor 31a in the C-axis rotation direction via the C-axis 31b. The Y-axis table 32 can be moved in the Y-axis direction by a Y-axis servo motor 32a and a Y-axis ball screw 32b. The X-axis table 33 can be moved in the X-axis direction by an X-axis servomotor 33a and an X-axis ball screw 33b. The rotation output of the spindle motor 34 is decelerated by the speed reducer 34a to rotate the work 35 supported by the chuck 34b and the tail stock 34c. The output of the chatter sensor (not shown) of the broach 30 is applied to the control circuit 36, and the control circuit 36 controls the NC controller 37.
Furthermore, the NC controller 37 uses the C-axis electric motor 31.
a, Y-axis servo motor 32a, X-axis servo motor 33a
Also, the spindle motor 34 is numerically controlled.

With the above configuration, when the spindle motor 34 rotates the work 35, the NC controller 37 controls the Y-axis servo motor 32a and the X-axis servo motor 33a so that the Y-axis table 32 and the X-axis table 33 are moved. Since it moves, the broach 30 moves to a predetermined cutting position. After that, the NC controller 37 controls the C-axis electric motor 31a to rotate the broach 30 and cut the work 35. At this time, when chatter occurs, the chatter sensor detects the chatter and applies the detection result to the control circuit 36.

FIG. 6 illustrates the cutting resistance and the like of each of the above embodiments. FIG. 6A schematically shows generation of chips in cutting, and FIG. 6B shows a two-dimensional cutting model. Figure 6
In (a), the chip 41 cuts the work 42 along the AB shear plane. Incidentally, 41a is a cutting edge of the chip 41, and 42a is a chip. In FIG. 6B, the chip 43 cuts the work 44, and chips 44a are generated. Incidentally, 43a is a cutting edge of the tip 43. Also, h
Is a cut, φ is a shear angle, γ is a rake angle, R is a vector indicating cutting resistance, and ω is an angle formed by the direction of cutting resistance and a shear plane. The cutting resistance R in this case is R = (bhτ _S ) / (sin φ · cos ω) ── (2) However, φ = φ ₀ + K ₂ γ-A / (Vh) ^1/2 ── (3) Known (mechanical engineering system 36, cutting theory, S53, 11, 20 first edition). In addition, b is the cutting width,
V is a cutting speed, and τ _S , φ ₀ , K ₂ , and A are constants.

To reduce the cutting resistance R according to the equations (2) and (3), V or γ may be increased or b or h may be decreased. In this case, increasing V can be dealt with by simply changing the software of the processing conditions, so that new hardware is not required. Further, if b is decreased, the cutting chips are reduced and the chips are easily broken, so that the chips can be prevented from being caught in the work or the like. Further, since the chips are smaller, it becomes easier to handle. Further, when h is reduced, the chips are thinned and easily broken, so that the chips can be prevented from being caught in the work or the like. Further, when γ is increased, the chips are easily curled and easily broken, so that the chips can be prevented from being caught in the work or the like, and the chips are further reduced, so that the chips can be easily handled.

FIG. 7 shows a specific control method for suppressing chatter. In FIG. 7, the cutting resistance detection unit 51 includes a sensor 51a and an amplifier 51b. The sensor 51a constantly detects cutting resistance during cutting of the work by the chip. It should be noted that this sensor 51 is shown in FIGS.
The attachment method of a is shown. The control circuit unit 52 includes a filter 52a, a chatter determination calculator 52b, a cutting condition determination calculator 52c, and a gate 52d. The filter 52a is
It consists of a low pass filter and a high pass filter. The low-pass filter allows the static component R _S (almost average cutting resistance) of the cutting resistance output from the amplifier 51b to pass through, while the high-pass filter uses the dynamic component R _{V of the} cutting resistance (cutting resistance generated by machine vibration or the like). High frequency component of) is passed. The chatter determination calculator 52b receives the dynamic component R _V and determines whether it is equal to or higher than a predetermined level (predetermined chatter level). When the dynamic component R _V exceeds the predetermined level, chatter occurs. It is determined that

The cutting condition determination calculator 52c stores the static component R _S as an actual measurement value of the cutting resistance for an appropriate time during cutting by one chip. At the same time, the chip passing completion (processing completion) signal and the cutting condition at that time are received from the NC unit 53 and stored. After that, the storage completion signal is sent to the NC unit 5
Send to 3. Next, a constant K as a function of the cutting conditions for the static component R _S , that is, the cutting conditions (V, b, h, γ) in the above equations (2) and (3) and the static component R. To calculate. That is, K is K = f (R _S , V, b, h, γ)-(4). Note that this analysis method will be described in detail later. Next, when a chattering determination result is received from the chatter determining calculator 52b, a cutting condition for reducing the static component R _S is calculated using the calculated constant K in order to suppress chattering. The calculated cutting conditions are replaced with the previously stored cutting conditions and stored. The gate 52d receives the calculated cutting conditions and N
Send to C section 53.

The NC section 53 performs general positioning control of the work and the broach according to the NC program and cuts the work according to the received cutting conditions. Further, when the cutting condition is received from the gate 52d, the cutting condition is changed to the sequentially received value. At this time, after the change of the cutting conditions is completed, the next NC command is output to the turn broaching machine. Also, the NC unit 53 outputs a chip passage completion signal and a cutting condition by the chip to the cutting condition determination calculator 52c every time one chip has completed passage, and receives a storage completion signal from the cutting condition determination calculator 52c. To do. In addition,
At the time of creating the NC program, since the mounting position of the tip of the machining tool and the size of the work are known, it is possible to calculate at which position or when the passage of the tip is completed. Therefore, when the NC program is devised such as a command for instructing the completion of passing the chip, it is possible to recognize when the passing of the chip is completed. In this way, the NC unit 53 checks whether or not the cutting conditions are transmitted from the gate 52d, and if the cutting conditions are transmitted, the cutting conditions are received and stored, and the stored cutting conditions are retrieved to NC. The cutting conditions in the program are changed to the stored values, and the turn broaching machine is controlled again.

When the cutting condition is not transmitted from the gate 52d, the transmission waits. Therefore, the processing conditions can be set before the start of the next chip cutting process. FIG. 8 shows a method of attaching a sensor (load cell, tool dynamometer, see FIG. 38) to the linear cut broach.
FIG. 8A shows the case where the sensor is attached to each chip, and FIG. 8B shows the case where the sensor is attached to the broach holder. In the broach 61 shown in FIG. 8A, the chips 61a to 61d are attached to the holder 61e via the sensors 62a to 62h. That is, the feed direction sensors 62a to 62d are attached between the illustrated upper ends of the chips 61a to 61d and the holder 61e, and the cutting direction sensors 62e to 62h are attached between the illustrated right ends of the chips 61a to 61d and the holder 61e. ing. Therefore, the cutting resistance can be detected for each chip from the combined output of the outputs of the feed direction sensors 62a to 62d and the outputs of the cut direction sensors 62e to 62h.

In the broach 63 shown in FIG. 8B, the chips 63a to 63d are attached to a holder 63e. Furthermore, the illustrated upper end of the holder 63e is fixed to the frame 63f via the feed direction sensor 64a, and the holder 6e
The right end of 3e in the figure is fixed to the frame 63f via a cutting direction sensor 64b. In this way, the cutting resistance applied to the broach 63 can be calculated from the combined output of the output of the feed direction sensor 64a and the output of the cutting direction sensor 64b.

FIG. 9 shows the front of the sensor (load cell, tool dynamometer) mounted on the rotary cut broach, and FIG. 10 shows the side of this mounted state. Figure 9
Further, in the rotary cut type broach 65 shown in FIG. 10, the tips 65a to 65d are the feed direction sensors 66a to 66d.
The holders 65e are attached to the holder 65e at predetermined intervals via 66d and cutting direction sensors 66e to 66h. The holder 65e has an arrow 65 around the rotation shaft 65f as a rotation center.
It rotates in the rotation direction indicated by g. The feed direction sensor 6
6a to 66d are arranged so as to detect the pressure in the rotating direction of the chips 65a to 65d, and the cutting direction sensor 66
e to 66h are arranged to detect the pressure acting on each of the chips 65a to 65d in the radial direction (the radial direction of the holder 65e). The work 67 is arranged so as to rotate in the direction of the arrow 67b around the rotation center 67a, and is intermittently cut by the chips 65a to 65d.

The sensors 62a to 62h and 66 are used.
Accelerometer (accelerometer,
The cutting resistance can be detected using (see FIG. 39). FIG. 11 shows the front in the case of a linear cut broach, and FIG. 12 shows the side in this case. 11 and 12
In the linear cut type brooch 68 shown in FIG.
8a to 68f are attached to the holder 68g at regular intervals. Further, an acceleration pickup 68h is attached to the upper end of the holder 68g. Note that arrow 68i
Is the feeding direction of the brooch 68. The workpiece 69 rotates in the rotation direction indicated by the arrow 69b at the rotation center 69a and is intermittently cut by the tips 68a to 68f.

FIG. 13 shows the front face in the case of a rotary cut broach, and FIG. 14 shows the side face in this case. Figure 1
In the rotary cut type broach 70 shown in FIG. 3 and FIG. 14, the chips 70a to 70d are arranged in the holder 7 at regular intervals.
0e is attached. Further, the biaxial acceleration pickup 70f is fixed to the rotation center of the holder 70e. The arrow 70g indicates the c-axis rotation direction of the holder 70e, and the arrow 70h indicates the Y-axis direction. The work 71 rotates about the rotation center 71a in the rotation direction indicated by the arrow 71b,
It is intermittently cut by the chips 70a to 70d.

FIG. 15 shows a cutting resistance detector 51 (see FIG. 7).
The flowchart of is shown. In FIG. 15, step S
At 1, the cutting resistance is detected. Next, in step S2, the detected cutting resistance is sent to the control circuit unit 52 (see FIG. 7). Further, when the cutting resistance is detected for each chip, the process returns to step S1 and the cutting resistance of the next chip is detected.

FIG. 16 shows a flow chart of the control circuit section 52. In FIG. 16, first in step S3,
A cutting resistance input is received from the cutting resistance detector 52. Then, it progresses to step S4. In step S4, the cutting resistance is separated into a static component R _S and a dynamic component R _V. Then, it progresses to step S5. In step S5, the static component R _S and the moving component R _V are stored. Then, it progresses to step S6. In step S6, YES or NO is determined regarding the presence of the machining completion signal of the workpiece by the chip. If the determination result is YES, the process proceeds to step S7. on the other hand,
If the determination result is NO, it means that the process is in process and steps S7 to 9 to be described later are unnecessary, so step S10
Go to.

In step S7, the cutting conditions for the machining-completed chip are stored. Then, it progresses to step S8. In step S8, a storage completion signal is sent to NC. afterwards,
Go to step S9. In step S9, the constant K (see FIG.
See). Then, it progresses to step S10.
In step S10, it is determined whether chatter has occurred. If the determination result is YES, the process proceeds to step S11. on the other hand,
If the determination result is NO, the process proceeds to step S13. In step S11, the cutting conditions are calculated based on the constant K. Then, it progresses to step S12. Step S1
In step 2, the recalculated cutting conditions are stored. afterwards,
Go to step S13. In step S13, the cutting conditions are sent to NC. Then, it returns to step S3 and receives the next cutting resistance input.

FIG. 17 shows a flowchart of the NC unit 53. In FIG. 17, first, in step S14, the processing machine (turn broaching machine) is controlled. Then, it progresses to step S15. In step S15, it is determined whether or not the machining of the work by the chip is completed. If the determination result is YES, the process proceeds to step S16. On the other hand, if the determination result is NO, the process returns to step S14. In step S16, a chip processing completion signal is sent to the control circuit unit 52. Then, it progresses to step S17. In step S17, the cutting conditions for the processed chip are sent to the control circuit unit 52. Then, it progresses to step S18.

In step S18, the control circuit section 52 is
The determination of YES or NO is made for the presence of the storage completion signal from. If the determination result is YES, the process proceeds to step S19. On the other hand, if the determination result is NO, step S18 is repeated. In step S19, the gate 5
Whether or not the cutting condition is input from 2d (see FIG. 7) is determined as YES or NO. The determination result is YES
If so, the process proceeds to step S20. On the other hand, the determination result is N
If it is O, step S19 is repeated. Step S2
At 0, the cutting condition is received. After that, step S2
Go to 1. In step S21, the cutting conditions are stored again. Then, it progresses to step S22. Step S22
Then, the cutting conditions of the NC program are changed to the values stored in step S12. After that, the process returns to step S14 and the next processing machine control is performed.

It is understood that when the cutting resistance R is reduced in order to suppress chatter, the cutting speed V should be increased by the equations (2) and (3) as described above. Φ ₀ , k
₂ , A, τ _S are constants determined by the work,
b, h, and γ are determined by the operator. Further, V is initially set as a cutting condition, and these are stored in advance in the cutting condition determination calculator 52c (see FIG. 7). ω (see FIG. 6) can be obtained from the static component R _s of the cutting resistance during the machining of the first chip and other constants stored in advance. Thus, it determines all constants, the relationship between the R _S and V are determined.

FIG. 18 shows a quantitative relationship between the static component R _s of the cutting resistance thus analyzed and the cutting speed V. In FIG. 18, when chatter occurs during machining at a cutting speed V _O such that the cutting resistance of a certain chip becomes R _SO , the cutting condition determination calculator 52c determines in advance based on the relationship of FIG. The cutting speed V ₁ is calculated so that the cutting resistance becomes a value R _S1 that is reduced by the reduced amount and sent to the NC unit 53 via the gate 52d (see FIG. 7). The NC unit 53 resets the NC program to V ₁ and restarts machining. In the processing machine, specifically, the feed speed v of the chip and the rotation speed r of the work are increased in the direction in which the relative speed between the chip and the work increases. Both the linear cut type and the rotary cut type can be performed in the same manner.

Further, in order to reduce the cutting resistance R in order to suppress the chatter, it is understood that the cutting width b should be reduced by the equations (1) and (2) as described above. The constants of the equations (2) and (3) at this time are obtained from the static component R _S of the cutting resistance during machining of the first chip and a predetermined constant as in the case of obtaining the cutting speed V. Figure 1
9 shows an example of a quantitative relationship between the R _S and the cutting width b thus obtained.

One method of changing the cutting width b is as follows. FIG. 20 shows a brooch in this case. Figure 2
In the brooch 72 shown in FIG.
Are attached to the holder 72g at regular intervals. The arrow 72h indicates the feeding direction of the brooch 72. FIG. 21 shows how the cutting width changes in this case. This method can be used when the width of the workpiece in the longitudinal direction to be cut is twice or more the cutting width of one chip. 20 and 21, for example, if chatter does not occur during cutting of the work 73 (rotation center 73a, rotation direction 73b) with the tip 72a, the cutting width of the tip 72b remains unchanged at b ₀ . Similarly, if chatter does not occur during cutting of 72b, the cutting width of 72c is set to b ₀ . Next, if chattering occurs while cutting the work with the tip 72c,
The cutting width b ₁ such that the cutting resistance becomes a value R _S1 reduced by a decrease Δb ₀ predetermined according to the graph of FIG.
Is sent to the NC unit 53 via the gate 52d (see FIG. 7). Next, when cutting the work with the tip 72d,
The position of the broach 72 is determined on the X axis so that the cutting width becomes b ₁ . The linear cut method and the rotary cut method can be performed in the same manner.

Next, a second method for changing the cutting method will be described. This method changes the plan angle. FIG. 22 shows a method of changing the plan angle in the linear cut broach. In FIG. 22, the angle of the tip 75 with respect to the rotation direction 74b of the workpiece 74 (rotation center 74a) (plan angle α
_{When 1} ) is set, it is cut into strips from the cutting start edge like peeling apples. In addition, 74c is a band-shaped chip. FIG. 23 shows a case where the plan angle (α2) is smaller than the plan angle (α1) in FIG. In FIG. 23, the width of the band-shaped chips 74d is the band-shaped chips 74c.
Will be wider than. In this way, the cutting width can be changed by adjusting the plan angle. FIG. 24 shows a state in which the plan angle is changed. In the linear cut type broach 76 shown in FIG. 24, the tips 76a to 76f have holders 76a to 76f.
It is attached to e so that the plan angle can be adjusted. Arrow 7
6g is for each tip 76a-7 when adjusting the plan angle.
The direction in which 6f rotates is shown. The work 77 can rotate in the direction of the arrow 77b around the rotation center 77a.

FIG. 25 shows the front of an actual linear cut broach, FIG. 26 shows the side of the broach shown in FIG. 25, and FIG. 27 shows the bottom of the broach shown in FIG. Figure 2
In the linear cut broach 80 shown in FIGS. 5 to 27, a pair of racks 82a and 82b are attached to a frame 81 so as to be movable in the longitudinal direction. Rotating shaft 83
The a to 83g are rotatably attached to the frame 81 by bearings 84a to 84g. Pinion 85
a to 85g are fixed to the side surfaces of the rotating shafts 83a to 83g,
It meshes with the pair of racks 82a and 82b. The tips 86a to 86f are fixed to the rotating shafts 83a to 83f by set screws 87a to 87f. The encoder-servo motor 88 is fixed to the frame 81, and its rotation output shaft 88a is fixed to the rotation shaft 83g.

Therefore, when the rotation output shaft 88a of the servomotor 88 is rotated by a predetermined input signal (a value obtained by converting the cutting width into a plan angle by the NC control device), the rotation shaft 8a is rotated.
3g rotates, the pinion 85g rotates simultaneously, and a pair of racks 82a and 82b move to the longitudinal direction. Therefore, since the pinions 85a to 85f rotate at the same time,
The rotating shafts 83a to 83f rotate, and the rotating shafts 83a to 8f
The chips 86a to 86f fixed to 3f rotate,
The plan angle changes. In order to change the plan angle, the main shaft to which the broach is fixed may be tilted, and the X-axis and the Z-axis may be simultaneously controlled in two axes so that each chip of the broach passes through the same place of the work. The plan angle can be adjusted by controlling the rotary cut broach in the same manner.

Further, in order to reduce the cutting resistance in order to control chatter, it is understood that the maximum cutting amount h of one chip should be reduced by the above equations (2) and (3). At this time, the constants of the equations (2) and (3) are obtained from the static component R _S of the cutting resistance during cutting by the first tip and a constant determined in advance, as in the case of the cutting speed V. FIG. 28 shows the static component R of the cutting resistance analyzed in this way.
An example of a quantitative relationship between _S and the maximum cutting depth h will be shown. Here, when chattering occurs during cutting with the maximum cutting amount h ₀ of one chip so that the static component of the cutting resistance of a certain chip becomes R _S0 , the cutting condition determination calculator 52c (see FIG. 7). )
Is based on the R-h relationship in FIG. 28, the notch h ₁ is determined so that the static component R _S1 of the cutting resistance is reduced by a predetermined reduction amount. Further, this cut h ₁ is sent to the NC unit 53 via the gate 52d, and the position of the broach is determined by the Y-axis so that the maximum cut amount of one chip becomes h ₁ . This method can be performed in both the linear cut type and the rotary cut type.

FIG. 30 shows the actual cut amount h when the Y-axis feed amount is constant. Further, FIG. 31 shows the actual cut amount h when the Y-axis feed amount is gradually reduced.
32 and 33 show the case where the Y-axis feed amount is changed as necessary. By doing so, it is possible to prevent a sudden change in the cutting depth h and stabilize the cutting process.

FIG. 34 shows the actual cut amount h when the chip feed speed (broach feed speed) v is constant. FIG. 35 shows the actual cut amount h when the feed speed v of the chip is gradually reduced. When the chip feed speed v is reduced, the work rotates a lot during the passage of one chip, and the cutting amount per one rotation of the work decreases. When the tip edge of the tip comes closest to the center of the work (the cutting depth is maximum at this time), the cutting depth becomes smaller as the feed speed v becomes smaller. Since the cutting speed V is the vector sum of the feed speed v of the tip and the rotation speed (rotational speed r) of the work, the cutting speed V decreases as the feed speed v of the tip decreases. The cutting resistance tends to increase as the cutting speed decreases. However, in the normal cutting region, the factor that the cutting resistance decreases due to the decrease in the cutting depth exceeds the factor that the cutting resistance increases due to the decrease in the cutting speed, and eventually the feed speed v of the chip is reduced, The cutting resistance R can be reduced.

FIG. 29 shows an example of a quantitative relationship between the actually analyzed cutting resistance and the feed rate of the tip, and it is confirmed that the cutting resistance R also decreases as the feed rate v decreases. Here, when chatter occurs during cutting at a chip feed speed v ₀ such that the cutting resistance of a certain chip becomes R _SO , the cutting condition setting calculator 52c (see FIG. 7)
Based on the R-v relationship in FIG. 29, v ₁ is calculated so that the cutting resistance becomes a value R _S1 that is reduced by a predetermined reduction amount, and is sent to the NC unit 53 via the gate 52d and the chip feed speed is obtained. Be v ₁ . This method can be applied to both linear cut type and rotary cut type.

FIGS. 36 and 37 show the actual cut amount h when the feed rate v of the tip is changed as required. By doing so, it is possible to prevent a sudden change in the depth of cut h and stabilize the cutting process. Instead of changing the chip feed speed v, a change in the chip feed acceleration may be used.

Next, a third method for increasing or decreasing the maximum depth of cut will be described. If the other conditions are constant, the cutting depth h per rotation of the work is reduced by increasing the rotation speed r of the work. Therefore, the cutting depth h can be reduced by increasing the rotation speed r of the work instead of decreasing the chip feed speed v. If the rotation speed r of the work is increased, the cutting speed V is also increased, and this influence also reduces the cutting resistance R. Further, instead of the rotation speed r of the work, the rotation acceleration of the work may be used. Further, this method can be applied to both the linear cut type and the rotary cut type. Furthermore, the above-mentioned v and r
May be changed in the direction of suppressing chatter at the same time. In addition to the above, the cutting resistance can be reduced even if the rake angle γ is increased by the above equations (2) and (3). To increase the rake angle γ, the curvature of the cutting edge of the blade (chip) may be reduced or the inclination of the blade (chip) may be increased. To increase the inclination of the blade, for example, in FIG. 12, the brooch 68 may be inclined in the YZ plane. in this case,
By synchronously driving the Y and Z axis motors, the blades can pass through the same position.

FIG. 38 shows a sectional structure of the above tool dynamometer. In the tool dynamometer 85 shown in FIG. 38, the ring-shaped force converter 85a is arranged so as to be sandwiched between the base plate 85b and the top plate 85c. Connector 8
5d guides the electric output of the force converter 85a to the outside. When the force converter 85a is a stack of a crystal plate cut in the X-axis direction, a crystal plate cut in the Y-axis direction, and a crystal plate cut in the Z-axis direction, the electric power of each of these crystal plates is increased. The output can be detected. Therefore, when the force converter 85a detects the pressure, the force converter 8a
The electrical output of 5a is guided to the outside from the connector 85d.

FIG. 39 shows the structure and principle of the accelerometer.
39A shows the structure of the accelerometer 86, and FIG. 39B shows the one-mass system model of the accelerometer 86. FIG. 39 (a),
In (b), the piezoelectric element (crystal such as barium titanate or quartz) 86a is arranged so as to be sandwiched between the base 86d and the weight 86e. Also, the weight 86e
Is a base 86 with a mounting bolt 86f and a spring 86g.
It is connected to d. Therefore, the weight 86e is the spring 8
It is urged toward the piezoelectric element 86a by 6g. The preamplifier 86b is connected so as to amplify the output of the piezoelectric element 86a, and the connector 86c is a terminal for guiding the output of the preamplifier 86b to the outside. 86h is a cover. Therefore, when acceleration is applied to the weight 86e, a pressure proportional to this acceleration is applied to the piezoelectric element 86a.
The piezoelectric element 86a can output a voltage proportional to the acceleration.

[0046]

As described in detail above, according to the turn broaching method and apparatus of the present invention, since the cutting resistance is adjusted to an appropriate value, it is possible to prevent an increase in equipment size and an increase in processing time. It is possible to eliminate chatter of the broach blade (chip) during cutting of the work. Therefore, it is possible to stabilize the cutting process and prevent damage due to chatter of the blade of the broach. Further, if the cutting speed is increased in order to reduce the cutting resistance, the processing time is further shortened, while if the cutting width or the cutting depth is increased or the rake angle of the blade is increased, the chips on the work etc. Prevents entrapment of chips and facilitates chip handling.

[Brief description of drawings]

FIG. 1 is a cutting model diagram of turn broaching according to the present invention and a conventional example.

FIG. 2 is a schematic front view of the turn broaching machine according to the first embodiment of the present invention.

FIG. 3 is a schematic view of a right side surface of the turn broaching machine according to the first embodiment.

FIG. 4 is a schematic front view of a turn broaching machine according to a second embodiment of the present invention.

FIG. 5 is a schematic view of the right side surface of the turn broaching machine of the second embodiment.

FIG. 6 is an explanatory diagram of cutting resistance and the like in each of the embodiments.

FIG. 7 is a control block diagram of each of the embodiments.

FIG. 8 is a side view of the broach of the first embodiment.

FIG. 9 is a front view of the broach of the second embodiment.

FIG. 10 is a side view of the broach of the second embodiment.

FIG. 11 is a side view showing a method of mounting the acceleration pickup of the first embodiment.

FIG. 12 is a front view showing a method of mounting the acceleration pickup of the first embodiment.

FIG. 13 is a front view showing a method of mounting the acceleration pickup of the second embodiment.

FIG. 14 is a side view showing a method of mounting the acceleration pickup of the second embodiment.

FIG. 15 is a flow chart of a cutting resistance detection unit of each of the embodiments.

FIG. 16 is a flow chart of a control circuit unit of each of the embodiments.

FIG. 17 is a flow chart of NC control of each of the embodiments.

FIG. 18 is a graph showing the relationship between cutting speed and cutting resistance in each of the examples.

FIG. 19 is a graph showing the relationship between cutting width and cutting resistance in each of the examples.

FIG. 20 is a front view of a part of the broach of the first embodiment.

FIG. 21 is a diagram showing a changing state of a cutting width in the first embodiment.

FIG. 22 is an explanatory diagram of a large plan angle in the first embodiment.

FIG. 23 is an explanatory diagram of a small plan angle in the first embodiment.

FIG. 24 is a detailed front view of the broach in the first embodiment.

FIG. 25 is a structural explanatory view of the brooch shown in FIG. 24.

26 is a sectional view for explaining the structure of the broach shown in FIG.

27 is a detailed bottom view of the brooch shown in FIG. 24. FIG.

FIG. 28 is a graph showing the relationship between cutting depth and cutting resistance in each of the examples.

FIG. 29 is a graph showing the relationship between the feed rate and cutting resistance of the chips of each of the examples.

FIG. 30 is a diagram showing the relationship between the Y-axis feed amount and the cutting amount of the chips of the respective examples.

FIG. 31 is a diagram showing the relationship between the Y-axis feed amount and the cut amount of the chips of the respective examples.

FIG. 32 is a diagram showing the relationship between the Y-axis feed amount and the cut amount of the chips of the respective examples.

FIG. 33 is a diagram showing the relationship between the Y-axis feed amount and the cut amount of the chips of the respective examples.

FIG. 34 is a diagram showing the relationship between the feed rate and the depth of cut of the chips of each of the examples.

FIG. 35 is a diagram showing the relationship between the feed rate and the cut amount of the chips of each of the examples.

FIG. 36 is a diagram showing the relationship between the feed rate and the depth of cut of each of the examples.

FIG. 37 is a diagram showing the relationship between the feed rate and the depth of cut of the chips of each of the examples.

FIG. 38 is a diagram showing the principle of a tool dynamometer.

FIG. 39 is a diagram showing the structure and principle of the accelerometer.

[Explanation of symbols]

20, 30, 61, 63, 65, 68, 70, 72, 7
6,80 Brooch 11, 41, 43, 61a-61d, 63a-63d,
65a-65d, 68a-68f, 70a-70d, 7
2a to 72f, 75, 76a to 76f, 86a to 86f
Chips 12, 26, 35, 42, 44, 67, 69, 71, 7
4, 77 Work piece 51 Cutting resistance detection section 51a Sensor 52 Control circuit section 52a Filter 52b Chatter judgment calculator 52c Cutting condition determination calculator 53 NC section R Cutting resistance V Cutting speed b Cutting width h Cutting γ Rake angle

Claims (6)

[Claims] 1. A broach having a plurality of blades and a workpiece
In the turn broaching method for cutting the work by using the plurality of blades one by one by controlling based on the C program, (1) before the start of the cutting process by the next blade, A step of measuring, (2) a step of analyzing the relationship between the cutting conditions and the cutting resistance from the measured cutting resistance and the cutting conditions at that time, and (3) chattering during cutting by the blade used immediately before. And (4) reduce the cutting resistance based on the analysis result of the process of (2) when the occurrence of chatter is determined in the process of (3) above. The step of calculating the cutting conditions and re-storing them in the NC program is carried out.
A turn broaching method characterized by being executed according to the NC program re-stored in the step (4). 2. The turn broaching method according to claim 1, wherein the cutting speed is increased in the step (4). 3. The turn broaching method according to claim 1, wherein the cutting width is reduced in the step (4). 4. The turn broaching method according to claim 1, wherein the depth of cut is reduced in the step (4). 5. The turn broaching method according to claim 1, wherein the rake angle of the blade is increased in the step (4). 6. A turn broaching apparatus comprising a broach having a plurality of blades and an NC controller for controlling the broach and the work based on an NC program, comprising: a. Cutting resistance measuring means, b. Means for analyzing the relationship between the cutting conditions and the cutting resistance based on the measured cutting resistance and the cutting conditions at that time; and c. Means for determining the presence or absence of chatter; d. Means for detecting the completion timing of cutting by one blade; e. When the detection means of d detects the completion timing, it is determined whether the occurrence of chatter is determined by the determination means of c during processing by the blade cut immediately before, and the occurrence of chatter is determined. A turn broaching device, further comprising NC program correcting means for calculating a cutting condition for reducing cutting resistance based on the analysis result of the analyzing means of b and re-storing the cutting condition in an NC program.