JPH04240011A - Perforating method - Google Patents

Abstract

PURPOSE:To provide a perforating method capable of executing a fine deep hole work smoothly, by preventing an excessive load torque from applying on a drill. CONSTITUTION:The load torque of a drill 1 is detected, at perforating time. In the case of the load torque thereof being less than the specified torque, the drill 1 feed is continued, and the drill is once retreated, at the time when the drill notches the specified quantity from the notching start position of a work 2. Also, the drill is once retreated by stopping the feed of the drill, in the case of the load torque becoming >= the specified torque. The working conditions of the perforating are changed in the state of the drill 1 being retreated, thereafter, the drill 1 is fed in again, and the perforating is re-opened under the changed working conditions. The perforating is completed when the work hole reaches the specified depth q0.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling method used in an NC processing machine, and more particularly to a drilling method for making fine deep holes in a workpiece.

0002

2. Description of the Related Art Conventionally, holes in workpieces have been drilled using NC machining machines, and deep hole drilling is usually performed in the following manner. FIG. 6 is a diagram for explaining a conventional deep hole drilling method. The drill 1 starts cutting at point R1, cuts through points R2 and R3 to point R4, and drills a hole with a depth of 3q in the workpiece 2. For the sake of explanation, points R3 and R4 are drawn shifted in the horizontal direction. In this case, the drill 1 moves in the order of arrows a, b, and c, and when it reaches a predetermined cutting depth q at point R2, it temporarily retreats to point R1 along arrow d. Thereafter, it moves again along arrow e to point R3. Thereafter, in the same manner, the machine moves in the order of arrows f, g, and h to complete the drilling process. In addition, in the figure, a broken line indicates rapid forward movement of the drill 1, and a solid line indicates cutting at a commanded feed rate. In this way, conventional deep hole machining is performed by repeating the cycle of cutting by the drill 1 and retracting the drill 1 as one cycle.

0003

However, in this conventional deep hole drilling method, the feed rate of the drill 1 during cutting is set constant regardless of the depth of the drilled hole. For this reason, when the depth of cut becomes deeper and the load torque of the drill 1 increases, the diameter of the drill 1 expands due to the load torque, and a so-called drill 1 eating phenomenon occurs, causing the drill 1 to break. Furthermore, since the supply of cutting oil tends to be insufficient at deep positions compared to shallow positions, it is desirable to lower the rotational speed of the drill 1. However, the rotation speed of the drill 1 is set to be constant regardless of the depth of the drilled hole. In this respect as well, the drill 1 may be eaten away due to an increase in the load torque of the drill 1, and the drill 1 may break.

[0004] As described above, with conventional deep hole drilling methods, it is extremely difficult to drill fine (for example, 2 mm or less in diameter) deep holes. The present invention has been made in view of these points, and it is an object of the present invention to provide a drilling method that can prevent excessive load torque from being applied to the drill and can smoothly perform fine deep hole drilling. purpose.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention detects the load torque of the drill in the drilling method of an NC processing machine that makes minute deep holes in a workpiece, and If the load torque is less than or equal to the predetermined torque, continue to feed the drill, and when the drill has cut into the workpiece by a predetermined amount from the cutting start position, the drill is temporarily retracted and the When the load torque exceeds a predetermined torque, the feeding of the drill is stopped and the drill is temporarily retracted, and when the drill is retracted, the machining conditions of the hole drilling process are changed, and the machining conditions of the hole drilling process are changed under the changed machining conditions. Provided is a drilling method characterized in that the drilling process is restarted and the drilling process is ended when the drilled hole reaches a predetermined depth.

[0006]

[Operation] Detects the load torque of the drill during drilling. If the load torque is less than a predetermined torque, the drill continues to be fed, and when the drill has cut into the workpiece by a predetermined amount from the cutting start position, the drill is temporarily retracted. Further, when the load torque exceeds a predetermined torque, feeding of the drill is stopped at that point and the drill is temporarily evacuated. The processing conditions for drilling are changed with the drill retracted, and then the drill is sent in again to resume drilling under the changed processing conditions. The drilling process ends when the machined hole reaches a predetermined depth. Therefore, it is possible to prevent excessive load torque from being applied to the drill. Further, fine deep hole machining can be performed under appropriate machining conditions depending on the depth of the machined hole.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining the drilling method of the present invention. Drill 1 starts cutting at point P1 and cuts at point P2.
, P3, and P4 to point P5, and a hole of depth q0 is made in the workpiece 2. For illustration purposes, points P3, P
4. Draw P5 by shifting it horizontally. Drill 1 is arrow L1
-Move sequentially along L8. One cycle of machining is performed with arrows L1 and L2, and similarly, L3 and L4, L5 and L6
, L7 and L8 each constitute one cycle. The broken line portion of each arrow indicates rapid forwarding of the drill 1, and the solid line portion indicates cutting under the commanded machining conditions.

First, the drill 1 moves in the order of arrows A and B, starts cutting the workpiece 2 at point P1, and when it reaches position P2 at a predetermined depth of cut q along arrow L1, cuts along arrow L2. It is temporarily evacuated (returned) to the position of point P1. At this point, the processing conditions are changed. That is, the feed speed F and rotation speed S of the drill 1 are reduced by predetermined ratios β2 and θ2 based on the following equation (1). Feed speed F = Feed speed in previous cycle F x β2 Number of revolutions S = Number of revolutions in previous cycle S x θ2 ──── (
1) Here, the correction coefficient β2 is set to, for example, 0.97, and the correction coefficient θ2 is set to 0.98.

After changing the machining conditions, the machine moves along the arrow L3 and performs cutting under the changed machining conditions. Cutting in this case starts from a point P21, which takes into account the clearance α with respect to the bottom P2 of the machined hole machined in the previous cycle. If the load torque applied to the drill 1 becomes excessive at point P3 before reaching the position of the predetermined depth of cut q from point P2, the feed of the drill 1 is stopped and the drill returns to the position of point P1 (arrow L4).
). This load torque is detected by a load torque sensor 36a (FIG. 5) built into the holder (spindle head) 36 (FIG. 5) of the drill 1. At this point, the machining conditions are changed again, but this time, since overload torque is being detected, they are changed based on the following equation (2). Feed speed F = Feed speed in previous cycle F x β1 Number of revolutions S = Number of revolutions in previous cycle S x θ1 ──── (
2) Here, the correction coefficient β1 is set to a value smaller than β2 (for example, 0.95), and the correction coefficient θ1 is similarly set to a value smaller than θ2 (for example, 0.97), and when overload torque is detected, the feed rate F , the reduction rate of the rotational speed S is increased. Further, in consideration of the influence of the feed rate F and the rotation speed S on the load torque, they are set so that β1<θ1 and β2<θ2. With this processing condition, from point P3 to point P
4, cutting is performed with a predetermined depth of cut q (arrow L5
, L6). In this way, the point P at depth q0
After cutting to 5 (arrow L7), the drill 1 returns along the arrow 8 and completes the drilling process.

FIG. 2, FIG. 3, and FIG. 4 are diagrams showing flowcharts for carrying out the present invention, and FIG. 2 shows steps 1 to 4.
4, 9, 10 and 15, FIG. 3 shows steps 5-8, and FIG. 4 shows steps 11-14, respectively. In the figure,
The number following S indicates the step number. [S1] Initial feed rate F and initial rotation speed S of drill 1,
Read the machining hole depth q0 and the depth of cut per cycle q. [S2] Move the drill 1 to the cutting start position P1. [S3] Start cutting. [S4] Determine whether the load torque of the drill 1 is excessive. If it is excessive, proceed to S5, otherwise proceed to S9. [S5] Stop feeding the drill 1, and read the current drill position (bottom position of the machined hole). [S6] Return the drill 1 to the cutting start position P1. [S7] The processing conditions are changed based on equation (2). [S8] Move the drill 1 to the bottom position of the machined hole to restart cutting. [S9] Determine whether the machined hole depth q0 has been reached. When it has been reached, the process proceeds to S15; when it has not been reached, the process proceeds to S10. [S10] It is determined whether the cutting depth q for one cycle has been reached. When the time limit has been reached, the process proceeds to S11, and when the time limit has not been reached, the program is terminated. [S11] Stop feeding the drill 1, and read the current drill position (bottom position of the machined hole). [S12] Return the drill to the cutting start position P1. [S13] The processing conditions are changed based on equation (1). [S14] Move the drill 1 to the bottom position of the machined hole to restart cutting. [S15] Since the drilling process has been completed, the drill is returned to its original position.

[0011] In this way, when performing fine deep hole machining,
When an excessive load torque is applied to the drill 1, the machining conditions are changed to sequentially reduce the feed rate F and the rotation speed S. Therefore, breakage of the drill 1 due to overload torque can be prevented, and fine deep hole drilling can be smoothly performed. Moreover, since the machining conditions are sequentially changed according to the depth of the machined hole, deep hole machining can be performed while appropriately responding to the shortage of cutting oil supply at a deep position. Furthermore, since the machining conditions can be changed simply by changing the correction coefficient, it is possible to easily set appropriate machining conditions according to the depth of the machined hole. Furthermore, in the past, the feed rate F and rotation speed S were set low in order to prevent the occurrence of breakage of the drill 1, etc., but in this embodiment, since the conditions are changed sequentially, the feed rate F at a shallow position is set low. , the rotation speed S can be set relatively high. Therefore, drilling can be performed with high efficiency.

FIG. 5 is a block diagram of the hardware of an NC processing machine for implementing the present invention. The processor 11 follows the system program stored in the ROM 12.
Controls the entire NC processing machine. ROM12 has EPROM
Alternatively, EEPROM is used. RAM13 has S
RAM is used to store various data. The nonvolatile memory 14 stores a machining program 14a of the present invention and the like. Since this non-volatile memory 14 uses a battery-backed CMOS or the like, its contents are retained even after the numerical control device is powered off. The PMC (programmable machine controller) 15 receives commands from the M function, S function, T function, etc., and executes the sequence program 1.
5a decodes and processes this command and outputs an output signal for controlling the machine tool. It also receives a limit switch signal from the machine side control circuit or a switch signal from the machine operation panel, processes it in the sequence program 15a, and outputs an output signal for controlling the machine side. In addition, signals necessary for the numerical control device are sent to the RAM 13 via the bus 27.
and read by the processor 11.

The graphic control circuit 16 causes the display screen data to be displayed graphically on the display device 16a. Display device 16a
CRT, liquid crystal display, etc. are used. keyboard 1
7 is used to input various data. The axis control circuit 18 receives a position command from the processor 11 and outputs a speed command signal for controlling the servo motor 20 to the servo amplifier 19. The servo amplifier 19 amplifies this speed command signal and drives the servo motor 20. A pulse coder 21 that outputs a position feedback signal is coupled to the servo motor 20. The pulse coder 21 feeds back position feedback pulses to the axis control circuit 18. pulse coder 2
In addition to 1, a position detector such as a linear scale may be used. These elements are required for the number of axes, but since the configuration of each element is the same, only one axis is shown here. The spindle control circuit 22 is a spindle amplifier 23
A command signal for driving the spindle motor 24 at a command rotational speed is output. The input/output circuit 25 exchanges input/output signals with the machine 26 . That is, the PMC 15 receives limit switch signals from the machine control circuit 39 and switch signals from the machine operation panel 40 and reads them. Also, P
It receives an output signal from the MC 15 that controls the pneumatic actuator, etc. on the machine side, and outputs it to the machine side. The manual pulse generator 41 outputs a pulse train for precisely moving each axis in response to a rotation angle command, and is used to precisely position the machine. Manual pulse generator 41 is mounted on machine operation panel 40 . The servo motor 20 is a ball screw 31
The movable part 32 is positioned by rotating. Movable part 32
moves the table 33 in a predetermined axial direction. On the other hand, the spindle motor 24 controls the rotation of the spindle head 36 at a predetermined speed via gear mechanisms 34 and 35. The drill 1 is fixed to the spindle head 36, and the table 3
Processing is performed on the workpiece 2 fixed on the top of the workpiece 3. Further, the spindle head 36 has a built-in torque sensor 36a that detects the load torque of the drill 1. Torque sensor 3
6a detects the load torque of the drill 1, and the detection signal is converted into radio waves and received by the input/output circuit 25 via a receiving section (not shown).

[0014]

As explained above, in the present invention, the machining conditions are changed in accordance with the load torque of the drill and the machining depth when drilling fine deep holes. Therefore, breakage of the drill due to overload torque can be prevented, and fine deep hole drilling can be smoothly performed. Furthermore, deep hole machining can be performed appropriately in response to insufficient supply of cutting oil at deep positions.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a drilling method of the present invention.

FIG. 2 shows a flowchart for carrying out the invention, showing steps 1-4, 9, 10 and 15;

FIG. 3 shows a flowchart for carrying out the invention, showing steps 5-8.

FIG. 4 shows a flowchart for carrying out the invention, FIG. 4 showing steps 11-14.

FIG. 5 is a block diagram of the hardware of an NC processing machine for implementing the present invention.

FIG. 6 is a diagram for explaining a conventional deep hole drilling method.

[Explanation of symbols]

1 Drill 2 Work 11 Processor 14a Machining program 36a Torque sensor

Claims (5)

[Claims] 1. In a drilling method of an NC processing machine that drills minute deep holes in a workpiece, the load torque of the drill is detected, and when the load torque is less than a predetermined torque during drilling, the feed of the drill is adjusted. When the drill continues to cut into the workpiece by a predetermined amount from the cutting start position, the drill is temporarily retracted, and during the hole drilling process,
When the load torque exceeds a predetermined torque, stopping the feeding of the drill, temporarily retracting the drill, and changing the processing conditions of the hole drilling process when retracting the drill,
The drilling method is characterized in that the drilling is restarted under the changed processing conditions, and the drilling is ended when the drilled hole reaches a predetermined depth. 2. The drilling method according to claim 1, wherein the processing conditions for the drilling are a feed rate and a rotational speed of the drill. 3. The drilling method according to claim 2, wherein the change in the processing conditions for the drilling process is a reduction in the feed rate and rotational speed of the drill. 4. Changing the machining conditions when the load torque exceeds a predetermined torque increases the feed rate of the drill at a larger rate than changing the machining conditions when the drill cuts into the workpiece by a predetermined amount from the cutting start position. 4. The drilling method according to claim 3, wherein the speed and rotational speed are reduced. 5. The drilling method according to claim 1, wherein the load torque is detected by a torque sensor provided in a drill holder of the NC processing machine.