JPH07124821A - Main spindle loading force reducing device of electric discharge machine - Google Patents

Abstract

PURPOSE:To eliminate a bad influence given to an interval control or a damage given to a main shaft in an electric discharge machining, by making the force loaded to the main spindle in a jumping operation of a die sinking electric discharge machine approach an allowable value. CONSTITUTION:The torque of the feed motor 16 of a main shaft 5 in a jumping stroke is detected by a detector 15, the then maximum peak value is stored in a memory 16, and the torque standard value stored beforehand and the peak value are compared in a comparator 18. And a corresponding correcting value is read by a jump adjustable speed data stored beforehand in a correcting value selecting and reading member 21, the correcting value is added to or subtarcted from the present jump adjestable speed so as to find a next adjustable speed, the next one stroke is carried out by the found adjustable speed, and such an operation is repeated in order, so as to approach the loading torque to the standard value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for reducing the force applied to a spindle when a die-sinking EDM machine jumps.

[0002]

2. Description of the Related Art Conventionally, in a die-sinking electric discharge machine as shown in FIG. 1, a jumping operation for moving an electrode up and down in order to discharge machining scraps generated during electric discharge machining between an electrode 9 and a work W machining surface. I do. The speed and cycle of this jump operation can be set manually and are constant after setting.

[0003]

In the manually set jump operation described in the prior art, the relationship between speed, torque and distance at the time of jump is shown in the graph of FIG. The torque of the spindle feed motor suddenly increases due to the viscosity of the machining fluid at the moment of leaving and at the moment of approaching the work most. The value of this torque is not constant and increases as the machining progresses and the size of the electrode inserted into the workpiece machining hole increases. Therefore, at the proper jump acceleration / deceleration at the start of machining, the torque increases as the machining progresses, and if it exceeds a certain design standard value, the spindle will tilt or vibration will occur at the end of the jump, adversely affecting the clearance control, and driving the spindle. There is a problem that the system such as a bearing member or a feed screw member is damaged.

Although this torque can be reduced as shown in FIG. 10 by manually setting a low jump acceleration / deceleration, it is impossible to maintain the optimum jump acceleration / deceleration corresponding to the fluctuating torque by manual setting. ,
If the safety is set to a low value, the processing time becomes long and the efficiency is lowered. The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to reduce the force applied to the spindle during a jump to a reference value or less stored in advance to adversely affect the clearance control. It is an object of the present invention to provide a device capable of maintaining high efficiency without affecting the mechanical system or damaging the mechanical system.

[0005]

In order to achieve the above-mentioned object, in a spindle load reducing apparatus for an electric discharge machine according to the present invention, during a jump of a die-sinking electric discharge machine for machining by electric discharge between an electrode and a work. Is a device for reducing the force applied to the spindle, and means for detecting the force applied to the spindle during the jump 1 stroke by the torque value of the spindle feed motor,
A means for comparing at least one reference value stored in advance with the detected torque value to select a corresponding correction value from the jump acceleration / deceleration correction data stored in advance, and a jump acceleration / deceleration at the time of detecting the torque. It comprises a calculating means for obtaining the next jump acceleration / deceleration execution value by adding or subtracting the correction value and a means for controlling the spindle feed speed by the jump acceleration / deceleration execution value.

[0006]

The peak value of the spindle feed motor torque during the jump 1 stroke is detected and compared with one or more reference values stored in advance. Based on the result, the corresponding correction is made from the jump acceleration / deceleration correction data stored in advance. The value is read, the read correction value is added to or subtracted from the current jump acceleration / deceleration to obtain the next jump acceleration / deceleration, and the next jump is executed according to the obtained acceleration / deceleration.

[0007]

【Example】

Example 1 In the die-sinking electric discharge machine of FIG. 1, a work W is placed on a table 2 of a machine base 1, and a spindle head 4 is mounted on a column 3 standing upright on the machine base 1 in the Z-axis direction. Is fixed to the main shaft head 4 so that the main shaft 5 can move only in the axial direction and is vertically provided. The main shaft 5 is moved and positioned by a servomotor 6 fixed to the column 3 via a ball screw 7.
An electrode 9 is detachably attached to the lower end of the main shaft 5 via a chuck 8.

The servo motor 6 is driven by the NC device 10, and the control system shown in the block diagram of FIG. 2 is built in the NC device 10. The spindle feed control unit 12 controls the spindle feed so that the output signal of the detector 13 approaches the feed command value, and the motor drive unit 11 includes the servo motor 6
Is a part that supplies electric power to the two, and these two are not different from the conventional NC servo system. The motor torque detection unit 15 of the jump control circuit 14 according to the present invention detects the torque of the servomotor 6 by the current value, and the torque peak value storage unit 16 stores the maximum torque peak value _MAX T _n during the jump 1 stroke. It is a part.

The load torque reference value storage unit 17 is a portion for storing the load torque reference value T ₁ input in advance. The load torque comparison unit 18 is a unit that compares _MAX T _n and T ₁ and outputs respective signals. The jump acceleration / deceleration correction data storage unit 19 is a unit for storing the correction values + α ₀ and −α ₀ input in advance. The correction value selection read unit 21 is a comparison unit 18.
Is a portion for reading and storing + α ₀ or −α ₀ based on the output signal of The jump acceleration / deceleration initial set value storage unit 22 is a portion that stores the jump acceleration / deceleration initial value α ₁ manually set during the start preparation operation.

The jump acceleration / deceleration calculation section 23 adds the correction value α ₀ to the current jump acceleration / deceleration α _n to obtain the next jump acceleration / deceleration α _N , and the obtained α _N is the maximum jump acceleration / deceleration α _MAX . If it is larger, α _N = α _MAX is set, and the part for calculating the next jump degree that does not exceed the maximum value. The jump acceleration / deceleration execution value storage unit 24 stores the obtained next jump acceleration / deceleration and outputs an acceleration / deceleration command to the spindle feed control unit 11. Jump acceleration / deceleration maximum value storage unit 2
Reference numeral 5 is a portion for storing the maximum value α _MAX of jump acceleration / deceleration.

Next, the first operation of this embodiment will be described with reference to the flowchart of FIG. In step S1, one jump stroke is performed, and in step S2,
The torque T _n of the servo motor 6 during this jump 1 stroke is detected by the current, and in step S3, the maximum peak value _MAX T _n of the load torque is compared with the load torque reference value T ₁ stored in advance, and in step S4. , _MAX T _n is greater than T ₁ .

If YES, in step S5, the correction value -α ₀ is read out from the jump correction data stored in advance, and in step S6, the acceleration / deceleration α _n of the jump 1 stroke just performed (at the time of starting). One stroke is calculated from the initial value α ₁ ) and the read correction value −α ₀ (α _N =
α _n −α ₀ ) acceleration / deceleration α _N of the next jump 1 stroke
Then, in step S7, the obtained α _N is stored as the next jump acceleration / deceleration execution value. In step S8, it is confirmed whether a machine stop command is issued. If NO, the process returns to step S1.

If NO in step S4, the correction value + α ₀ is read in step S9, the next jump acceleration / deceleration α _N is obtained by calculation (α _N = α _n + α ₀ ) in step S10, and step S11 In step S12, the maximum jump acceleration / deceleration rate α _MAX is compared with the obtained α _N, and in step S12 it is confirmed whether α _N is larger than α _MAX . If NO, step S
7, the obtained α _N is stored as the next jump acceleration / deceleration execution value. If YES for some reason, α _N = α _MAX is set in step S13 and α _{N is set.}
Is restricted so as not to exceed the maximum value, and the process is returned to step S7. When YES is determined in step S8, the process ends.

FIG. 4 is a graph showing changes in the load torque when the above operation is repeated. The torque peak value at the first stroke when the jump operation is started at the initial value α ₁ is t ₁
Then, since it exceeds the reference value T ₁ , the second acceleration / deceleration α ₂ becomes a value obtained by adding the correction value −α ₀ to the initial value α ₁ and, as a result, t ₂ becomes T ₁ or less. The third acceleration / deceleration α ₃ is the same as the previous acceleration / deceleration α ₂ and the correction value + α ₀
Peak torque t ₃ is a value obtained by adding more than T _1. In this manner, the jump is repeated with the torque having the correction value α ₀ sandwiching the reference value T ₁ as the vertical width, the electric discharge machining progresses, and the torque increases, so that t _n is not less than the correction value α _{0 and is} more than T ₁ . Only at this time, −α ₀ correction is performed twice and the vertical movement with the reference value T ₁ sandwiched is repeated.

Second Embodiment The second embodiment is different from the first embodiment in that the load torque reference value storage unit 17 of FIG. 2 stores two values, a reference value upper limit T ₁ and a reference value lower limit T _2. The load torque comparison unit 1
At 8, the T ₁ and T ₂ are sequentially compared with the torque peak value _MAX T _n . Therefore, the description of the structure of the same portion is omitted, and the second operation of the embodiment will be described according to the flowchart of FIG. In step S14, one jump stroke is performed, and in step S15,
The motor torque T _n during one stroke is detected, and step S16
It is confirmed whether the peak value _MAX T _n of the torque detected in _{1 is} larger than the reference value upper limit T ₁ .

If YES, step S18
In step S19, the jump acceleration / deceleration correction value −α ₀ is read out, and in step S19, the next jump acceleration / deceleration rate α _N is calculated by calculation (α _N = α _n −α ₀ ). However, α _n is the current jump acceleration / deceleration, and the initial value α ₁ is used at the start of the jump. Next, in step S20, the obtained α _N is stored as the next jump acceleration / deceleration execution value,
Check if the machine stop command is issued at 21, and NO
If so, the process returns to step S14. Step S17
In the case of NO in step S22,
_It is confirmed whether _MAX T _n is smaller than the reference value lower limit T ₂ , and Y
In the case of ES, the correction value + α ₀ is read in step S23, and the calculation (α _N = α _n is read in step S24.
The next jump acceleration / deceleration α _N is calculated by + α ₀ ).

Then, in step S25, the obtained α
_The maximum value α _MAX is compared with _N, and α is set in step S26.
_N is stored as the next jump acceleration / deceleration execution value. If the answer is YES for some reason, step S2
In step 7, α _N = α _MAX is set so that α _N does not exceed the maximum value, and the process returns to step S20 to set α _MAX to α _MAX .
Remember as _N. If NO in step S22, α _N = α _n is set in step S28. However, in the case of the first stroke at the start of the jump, α _N = α ₁ is set and the process returns to step S20. Then, if YES in step S21, the process ends.

FIG. 6 is a graph showing changes in the load torque when the above jump operation is repeated. For example, the load torque when the jump operation is started at the initial value α ₁ is t ₁
Then, since it is considerably lower than the lower limit T _{2 of} the reference value, + α ₀ correction is performed twice, and the torque becomes t _{3 at the third} stroke, and the lower limit T ₂ of the reference value is exceeded for the first time. Then, the correction from the fourth stroke is not performed, the jump is continued with the acceleration / deceleration execution value α ₄ at this time being kept, and when the torque becomes t _n and exceeds the upper limit T ₁ after several strokes, −α ₀ The correction is performed and the torque falls within the allowable value at the next stroke, and the jump is continued with the jump acceleration / deceleration execution value at this time again. For this reason, the upper limit of the reference value is not frequently exceeded, and safety is increased.

Third Embodiment The third embodiment is different from the second embodiment in that the load torque reference value storage unit 17 in FIG. 2 has a reference value upper limit T ₁ above the reference value upper limit T ₁ and a reference value lower limit. Below T ₂ , the reference value lower limit T ₃
Stores the reference value of 4 stages T ₀ through T ₃ provided with the jump deceleration correction data storage unit 19 in the example -2α _0, -
The torque peak value detected by the load current comparison unit 18 is stored by storing the four-level correction values α ₀ , + α ₀ , and + 2α _0.
MAX T _{n and} the four-step reference values of T _{0 to} T ₃ are sequentially compared, and in the correction value selection reading unit 21, when _MAX T _n ≧ T ₀ , −2α _0, and when _MAX T _n ≧ T ₁ , − α ₀ to _MAX
+ Α ₀ when T _n ≧ T ₂ and +2 when _MAX T _n ≦ T ₃
We have just read out α ₀ .

Therefore, the description of the structure of the same portion is omitted, and FIG.
The third operation of the third embodiment will be described with reference to the flowchart of FIG. In step S29, one jump stroke is performed, and in step S30 the motor torque T _n during this one stroke is detected. In step S31, the peak value _MAX T _n of the load torque and the reference values T _{0 to} T ₃ are determined. Compare sequentially. Then, in step S32, _MAX T _n is T ₀
Is determined to be equal to or larger than, and if YES, the correction value −2α ₀ is read in step S34. Next, in step S35, the current jump acceleration / deceleration α _n
The reference value -2Arufa ₀ read and added to, and calculates the following acceleration alpha _N, stores alpha _N obtained in step S36 as the next jump deceleration running value, step S3
It is confirmed whether or not the machine stop command is issued at 7, and if NO, the process returns to step S29, and if YES, the process ends.

If NO in step S32,
In step S38,_MAXT_nIs T₁Equal to or
Check if it is larger, and if YES, go to step S39.
Correction value-α₀Read out. Then step S4
At 0, the current jump acceleration / deceleration α_nRead to
α₀Next acceleration / deceleration α_NAnd step S3
Returned to 6. If NO in step S38
In step S41,_MAXT _nIs T₂Greater than
Check if it is, and if YES, go to step S42.
The current jump acceleration / deceleration rate α_nThe next jump acceleration / deceleration
α_NIs returned to step S36.

If NO in step S41, it is confirmed in step S43 whether _MAX T _n is equal to or smaller than T _3, and in step S44, the correction value + 2α ₀ is read. Then, in step S45,
+ 2α ₀ is added to the current jump acceleration / deceleration α _n to obtain the next jump acceleration / deceleration α _N , and in step S46, it is confirmed whether or not the obtained α _N is larger than the maximum value α _MAX .
If NO, the next acceleration / deceleration is set to α _N in step S3.
Returned to 6. If YES for some reason, α _N = α _MAX is set and α _N is restricted so as not to exceed the maximum value, and the process returns to step S36. In addition, step S43
In the case of NO, the correction value + α ₀ is read out, and in step S49 the current jump acceleration / deceleration α _n is added to the read + α ₀ to obtain the next jump acceleration / deceleration α _N , and the process returns to step S46.

FIG. 8 is a graph showing changes in the load torque when the above jump operation is repeated. For example, when the initial value α ₁ is set small, several steps are required until the acceleration / deceleration that provides the optimum torque is reached. It takes longer and the processing becomes slower. Therefore, when the torque t ₁ of the first stroke performed with the initial setting value α ₁ is equal to or less than the allowable value lower limit T ₃ , twice the value α ₀ +2.
α ₀ correction is performed to quickly raise the load torque to the appropriate load torque, and no correction is performed in the appropriate torque region that exceeds the reference value lower limit T ₂ . Eventually, when the electrode 9 comes into the work W deeply and the torque gradually increases and exceeds the reference value upper limit T ₁ , -α ₀ correction is performed and the electrode 9 is pulled down within the proper torque range.

Further, for example, when the initial value α ₁ is set large, the load torque abruptly increases such as when the electrode is worn during machining or when the electrodes are replaced, and it takes several strokes to reach the proper torque range. This will shorten the life of the mechanical system. Therefore, even when the torque exceeds the maximum allowable upper limit T ₀ , -2α ₀ correction that is twice α ₀ is performed to quickly reduce the torque to the appropriate load torque. The correction values −2α ₀ and + 2α ₀ do not necessarily have to be twice α ₀ , and can be set to arbitrary values.

[0025]

Since the present invention is configured as described above, it has the following effects. Since the force applied to the spindle during the jump is made to approach a preset reference value, there is no adverse effect on the gap control during electrical discharge machining or damage to the mechanical system such as the spindle and the spindle feed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a die-sinking electric discharge machine of this embodiment.

FIG. 2 is a block diagram of an NC servo system according to the present embodiment.

FIG. 3 is a flowchart of the first operation of the embodiment.

FIG. 4 is a graph showing a change in load torque when the first jump operation of the embodiment is repeated.

FIG. 5 is a flowchart of a second operation of the embodiment.

FIG. 6 is a graph showing a change in load torque when the second jump operation of the embodiment is repeated.

FIG. 7 is a flowchart of the third operation of the embodiment.

FIG. 8 is a graph showing a change in load torque when the third jump operation of the embodiment is repeated.

FIG. 9 is a graph showing changes in speed / torque / distance during a jump used in the description of the conventional technique.

FIG. 10 is a graph used for explaining the conventional technique, and FIG.
FIG. 9 is a graph showing a state in which the jump acceleration / deceleration is further reduced and the torque peak value is kept low.

[Explanation of symbols]

5 Spindle 6 Spindle feed motor 9 Electrode 10 NC device 14 Jump control circuit 15 Torque detection unit 18 Load torque comparison unit 21 Correction value selection readout unit 23 Jump acceleration / deceleration calculation unit W work

Claims (1)

[Claims] 1. A device for reducing a force applied to a spindle during a jump of a die-sinking electric discharge machine that performs machining by an electric discharge between an electrode and a work, the force being applied to the spindle during a jump 1 stroke. Means for detecting the torque value of the spindle feed motor, means for comparing at least one reference value stored in advance with the detected torque value, and selecting a corresponding correction value from jump acceleration / deceleration correction data stored in advance. Calculating means for obtaining the next jump acceleration / deceleration execution value by adding or subtracting the correction value selected as the jump acceleration / deceleration at the time of torque detection, and means for controlling the spindle feed speed by the jump acceleration / deceleration execution value. A spindle load reducing device for an electric discharge machine, comprising: