JPH068051A - Electric discharge machining method and device therefor - Google Patents

Abstract

PURPOSE:To improve the chamfer of a tool electrode to a workpiece at the time of starting machining so as to maintain stable machining even at the beginning of machining by obtaining the evaluation value from the weight value and an evaluation relational expression, and controlling the machining condition on the basis of this evaluation value. CONSTITUTION:One out of plural evaluation relational expressions provided previously is selected according to the distributed state of weighted sampling value, and evaluation is obtained by an evaluation value computing means 110 according to the weight value and the evaluation relational expression. The reference machining progress speed computed on the basis of the interpole state detected by a detecting means 102 and stored machining conditions and machining elements is compared for judgment with the present machining progress speed recognized through a driving control means 104, and a moving command is sent to the driving control means 104 on the basis of this judgment value, or the machining condition is changed one after another by a machining condition control means 105 on the basis of the compared judgment value to control the machining condition on the basis of the obtained evaluation value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the state of a gap between a tool electrode and a workpiece, and changes and controls the machining conditions based on the detection result to enable stable electric discharge machining. The present invention relates to a processing method and an apparatus thereof.

[0002]

2. Description of the Related Art In order to perform stable machining by maintaining a state (a state of a discharge gap) between both electrodes of a tool electrode and a work piece in a predetermined state, a voltage between the electrodes is conventionally used. Alternatively, the electric current is detected, and the detected value is compared with a preset reference value, and based on the comparison result, electrical processing conditions such as the gate on time, the gate off time, and the average machining current value are changed at any time. It has been modified to maintain the desired electromachining conditions set by the operator.

Further, the entire machining process is divided into several stages, and a suitable machining condition is automatically or manually selected by a worker from a data group of machining conditions stored in advance at each stage. And set this,
The processing speed is made faster, and moreover, stable processing can be maintained.

By the way, in the above conventional control method,
When the machining is sufficiently advanced or the tool electrode has a simple shape, the machining state is not greatly impaired, but the change in the facing area between the tool electrode and the workpiece in the machining part is complicated. In this case, the condition of the machining gap changes remarkably, and in this case it is not possible to take sufficient measures, and it is difficult to realize stable machining. In particular, immediately after the start of electric discharge when the workpiece is completely unmachined, if the operator performs machining under the final desired electrical machining conditions set by the operator, the average machining current value is too large, etc. The machining state is extremely unstable. Therefore, simply detecting the voltage or current between the poles and controlling it so that it matches the reference value will result in accurate changes to subtle changes. I can't respond.

In addition, if the electric machining conditions are set in advance at each machining stage such as rough, medium, and finishing, and machining is performed by simply changing the stage, it takes time to select and set an appropriate machining condition. Not only that, but if the above setting is incorrect, it will seriously hinder machining.

FIG. 5 is a block diagram of a conventional electric discharge machine proposed in Japanese Patent Application No. 2-214146 in order to solve the above problems.

In this conventional apparatus, the tool electrode 1 and the workpiece 2 are connected to a machining power source 9 and relatively moved by an X-axis drive motor 4, a Y-axis drive motor 5 and a Z-axis drive motor 6. It Prior to electrical discharge machining, machining conditions suitable for the intended machining, such as gate on time, off time, power supply voltage, servo reference voltage, etc., as well as the material of the tool electrode 1 and the workpiece 2, etc. Is set via the setting means 101.

The machining gap state detecting means 102 detects machining voltage or machining current during machining, and the detected value is compared with a predetermined reference value by the machining gap state comparing means 103, and this comparison value is driven. It is sent to the control means 104 and the processing condition control means 105a. The drive control means 104 converts the input comparison value into a drive control value, and rotates the Z-axis drive motor 6 to move the machining head unit 3 forward or backward by a predetermined amount. At this time, the tool electrode 1 after being moved by a predetermined amount is jumped according to the measurement value by the position detection device 7. Since the position of the tool electrode 1 after this movement is recognized, the gap between the tool electrode 1 and the workpiece 2 is maintained at an appropriate distance, and the machining progress distance, which is the distance at which machining has progressed in a predetermined time Is measured.

Further, the machining condition control means 105a changes the electrical machining conditions based on the comparison value output from the machining gap state comparison means 103, and issues a new machining condition setting command to the machining condition change setting means 107. Alternatively, the changed value is sent to the machining pulse generator 106 so as to maintain a good state of the gap. Processing condition change setting means 10
7 is provided separately from the control system so that an operator can set or change desired electrical processing conditions before or during processing, and the processing control means 105 is provided.
A new processing condition is set according to the command a. The storage unit 111 stores a combination of a plurality of processing conditions and a table of processing element data.

In this conventional apparatus, the operator uses the setting means 101 to turn on the gate TON, turn off the gate TOFF, maximum average machining current value ImMAX, minimum average machining current value ImMIN, current peak value IP, Maximum current density Id, machining condition change rate α representing the change rate of processing conditions,
The value of the safety factor β determined by the processing form and the method of using the processing liquid is set. The NC device extracts a combination of machining conditions corresponding to the minimum average machining current value ImMIN set in accordance with the machining conditions and machining element data table in the storage means 111 on the basis of the settings of these workers, and extracts this first. Set as the processing condition of. After finishing the above settings, the processing under the first processing conditions is started.

In this case, the standard machining progress speed Fr is calculated from the above calculation result. The standard machining progress rate Fr
Indicates a basic machining progress distance per unit time for which safe machining can be performed.

Im (i + 1) = Im · α (ampere) ... (1) Im (i + 1) represents the average machining current of the next stage of the currently used average machining current Im. The current average machining current Im is multiplied by the change rate α set by the operator. Then, the average machining current Im (i + 1) of the next stage obtained by the equation (1), the material of the tool electrode 1 that has been set, and the material of the workpiece 2 that has already been set are determined as parameters. Based on the maximum current density Id, the minimum area SMIN of the cross section of the next tool electrode 1 that can be stably processed is obtained as follows.

SMIN = Im (i + 1) / Id (square centimeter) (2) Further, the volume machining speed Vf corresponding to the average machining current value Im (i + 1) at the next stage is stored in the storage means 111. Based on the minimum machining area SMIN obtained from the table of machining conditions and machining element data, the volume machining speed Vf and the equation (2), and the preset safety factor β, the standard machining progress speed Fr is calculated as follows. Ask for.

Fr = β · Vf / SMIN (mm / mim) (3) The average machining current Im (i + 1) in the next step, the minimum area SMIN that can be stably machined, and the standard machining progress speed Fr are calculated as follows. , Collectively referred to as control variables. The standard machining progress speed Fr is compared with the current machining progress speed F, and when the value of the current machining progress speed F becomes smaller than the value of the standard machining progress speed Fr, it is judged that one step has finished, The average machining current Im (i + 1) of the next stage is obtained by the equation (1), and the combination of the machining conditions corresponding to the average machining current Im (i + 1) of the next stage is the machining condition, It is extracted from the table of processing element data, and the processing conditions are changed to the extracted processing conditions, and the process proceeds to the next stage.

The average machining current value is increased stepwise by executing the above operation until the set maximum average machining current ImMAX is reached.

[0016]

In the above-mentioned conventional device, the detected inter-electrode voltage or inter-current is data obtained in an extremely short period of time, and the voltage value or current detected in such an extremely short period of time is as described above. The value often shows a value different from the actual state between the poles due to the influence of disturbance or the like. Therefore, the processing state that is not actually unstable as a whole processing state, and the processing state that does not affect the processing accuracy etc. is erroneously determined to be an unstable state, There is a problem that the processing conditions are unnecessarily changed.

Further, since the machining conditions are immediately changed only by the result of comparison between the standard machining progress rate and the current machining progress rate, it is not necessary to actually change the machining conditions, or rather the machining conditions are not changed. Even if the condition is good, the processing conditions are changed, so that there is a problem that the efficiency of the work is reduced and it may be difficult to maintain the processed state in some cases.

Further, since the machining conditions are rapidly changed, when the machining conditions are changed, the good machining state is impaired, the machining progress speed, the average machining voltage, and the average machining current are changed, and the control is accurately performed. However, there is a problem that the electric discharge machining is interrupted or fails.

According to the present invention, the so-called tool electrode is well attached to the workpiece at the start of machining, stable machining can be maintained even in the initial stage of machining, and machining conditions can be changed according to the actual machining state. It is an object of the present invention to provide an electric discharge machining method and a device therefor capable of performing safe and high-speed machining easily even if machining is performed by automatic operation.

[0020]

According to the present invention, a detected value of a gap state is sampled for a certain period of time, and one of a plurality of predetermined evaluation function formulas is based on the result of the sampling.
One of them is selected, and the machining state is judged based on the machining evaluation value.Also, an appropriate machining speed is calculated based on the judgment of the appropriate machining state, and the electrical machining conditions are changed based on this. Along with the determination, the tool electrode is either raised or lowered. Further, according to the present invention, the amount of change in one step is further subdivided, and the processing conditions are changed extremely gently.

[0021]

According to the present invention, the detected value of the machining gap state is sampled for a certain period of time, and based on the result of this sampling, the deviation state value from the reference state is obtained to judge the machining state, so that the proper machining state is recognized. It becomes possible to do. In addition, an appropriate machining speed is calculated based on the judgment of an appropriate machining state, and based on this, the change of electrical machining conditions is decided, and by raising or lowering the tool electrode together, unnecessary electrical Avoid changing the mechanical processing conditions. Furthermore, by further subdividing the amount of change in one step and changing the processing conditions extremely gradually, an appropriate control state can be maintained.

[0022]

FIG. 1 is a basic configuration diagram of an electric discharge machine showing an embodiment of the present invention. In this example,
The same members as those in the conventional example shown in FIG. 5 are designated by the same reference numerals.

In this embodiment, the tool electrode 1 and the work piece 2 are relatively moved by the motors 4, 5 and 6, and a discharge voltage is generated between the tool power supply 9 and the tool electrode 1 and the work piece 2. It is applied, and the workpiece 2 is processed into a desired shape. The setting unit 101 has an input unit and a storage unit (not shown), and an operator can set the gate on time, off time, peak current value (average machining current value), power supply voltage, servo reference voltage via the setting unit 101. Etc., electrical processing conditions, material of the tool electrode 1, material of the workpiece 2, processing conditions such as presence / absence of a machining fluid jet, processing elements such as desired volume processing speed, maximum current density, rate of change of processing conditions, etc. The parameters necessary for performing the control calculation of are input and stored. Of course, the processing conditions may be set in advance by using a medium such as an NC program instead of the setting means 101.

Further, for example, the maximum current density is a current value per unit area mainly determined by the material of the tool electrode 1 and the workpiece 2, and is necessary for calculating the maximum current density and the processing condition conversion rate. A plurality of corresponding data are stored in the storage device in advance regardless of the operator's input, and the material of the tool electrode 1 and the material of the workpiece 2 are input, and the storage corresponding to the material is performed. The value may be automatically selected and determined. Other set values may be input and set as described above.

Based on the values set as described above, the processing control means 105 selects and sets the processing conditions at the first stage at the start of processing from the processing conditions and the processing element data table in the storage means 111. At the same time, the control variable is calculated. The gap state detecting means 102 detects a gap voltage or a gap current, and the gap detection value is sent to the sampling means 108. The sampling unit 108 includes storage units 201 to 202, and each address is connected to the arithmetic processing unit 203. The arithmetic processing unit 203 temporarily stores the detected value of the voltage between contacts or the current between contacts in the storage unit 202. In addition, the arithmetic processing unit 203 determines, based on the detected value between the poles, as the number of times among the addresses in the storage unit 201,
Allocate to one address and add the corresponding addresses.

That is, the arithmetic processing unit 203 appropriately reads the stored value from the corresponding address of the storage unit 201 and adds the number of detections according to the detected value between the poles, and adds the detection number to the stored value. Send to the read address and store again. That is, the detection count data is added to create a histogram of the detection values between the poles.

FIG. 6 is a diagram showing an example of the above-mentioned histogram, in which A to H indicate addresses in the storage means 201. Further, the total number of detections during a predetermined period is added and stored in an address other than the above-mentioned predetermined address of the storage means 201 (the sampling time is, for example, 500 ms).
ec is enough). After the elapse of a predetermined time, the arithmetic processing unit 20
3 transfers the number of detections and the total number of detections corresponding to each address to the evaluation value calculation means 110. Storage device 202
The detected values are stored in and can be used when obtaining the average value of the detected values. The sampling period is measured by a timer circuit (not shown) or the like.

The storage means 201, 202 need only have the necessary addresses, and the number of storage means is not limited. Further, instead of the sampling means of the above aspect, for example, another configuration such as a counter for adding the obtained values may be adopted.

The evaluation value calculation means 110 obtains an evaluation value for judging the processing state by using a predetermined calculation expression based on the result of the sampling, and the evaluation value is sent to the processing control means 105. It is determined whether the jump operation of the electrode 1 is necessary or whether the processing conditions are changed. The processing condition control means 105 sends a command signal for jump control to the drive control means 104 in order to cause the tool electrode 1 to perform a jump operation according to the above determination. Drive control means 104
Causes the jump operation to be performed at predetermined intervals until the jump control command is changed.

On the other hand, when the machining conditions are changed, appropriate machining condition values and machining element values are called from the table of machining conditions and machining element data stored in the storage means 111 in advance, and the above values are used as command values. The value is converted and a new processing condition is set in the processing condition changing means 107, and the command value is sent to the processing pulse generating means 106 to change the processing condition. In the present embodiment, the processing condition control unit 105, the sampling unit 108, and the calculation unit of the evaluation value calculation unit 110 are described separately, but these may be performed by one calculation device.

In the above table, the gate on-time, gate off-time, peak current value (or average machining current value), volume machining speed, etc. are stored in ascending order. The combination of these conditions is created as needed, using the various processing conditions or processing elements already described,
Various tables other than the above can be created. In this case, the data obtained from the drive control means 104 and the sampling means 108 is the processing state storage means 1
It is stored in No. 12 and can be used again as data for evaluation judgment.

The above control is repeatedly performed at a predetermined interval. Therefore, in the above embodiment, for example, a timer interrupt (not shown) is provided in the machining control means 105 to preset a predetermined time. Keep it. This predetermined time is the minimum indispensable calculation time for the evaluation value calculation of the discharge state or the calculation of the standard machining progress speed by the sampling, and the time during which the change of the machining conditions effectively acts is taken into consideration. For example, 0.5 seconds may be set.

FIG. 2 is a flow chart for explaining the outline of the method of the present invention, and FIGS. 3 and 4 are flow charts for explaining a part of the flow chart shown in FIG. 2 in detail.

First of all, the worker is required to turn on the gate on time TO.
N, gate off time TOFF, servo reference voltage, power supply voltage, current peak value IP, tool electrode material, workpiece material, tool electrode diameter, presence or absence of machining fluid jet, presence or absence of machining fluid suction, machining mode, The processing conditions and processing elements such as the maximum average processing current ImMAX, the maximum current density Id, the volume processing speed, the surface roughness, and the tool electrode wear degree are set via the setting means 101. At the same time, the machining condition change rate α, which indicates the degree of change when gradually changing the machining conditions, and the machining safety factor β, which is a calculation coefficient for obtaining the standard machining progress rate at which there is no machining failure, are calculated. Set (M1).

The maximum average machining current ImMAX, the maximum current density Id, the rate of change α, and the safety factor β are based on the machining conditions such as the set current peak value and the material of the tool electrode, and the like. Store the corresponding value in advance,
You may comprise so that it may be automatically selected and set according to the setting of the said processing conditions.

The rate of change α determines the degree of change in the processing conditions. The smaller the rate of change α is,
As the rate of change α becomes slower and the rate of change α is smaller, stable machining can be generally performed. However, when the rate of change α is extremely small, machining time is longer than necessary. Therefore, the rate of change α is determined with reference to the material of the tool electrode, the material of the workpiece, the machining shape, and the like. In addition, as described above, the safety factor β is a calculation coefficient used when calculating the reference machining progress speed Fr, and it is determined whether the machining form such as punching, bottoming, contouring, or the like, and the use of the machining fluid jet. Judgment is made according to the type of liquid treatment such as the presence or absence or the presence or absence of use of the processing liquid suction treatment. Safety factor β
Is 0.3 depending on the processing mode and the processing liquid processing mode.
It is desirable to be determined within the range of about 0.8.

After the work is completed, in the NC device, based on the set machining conditions or machining element data, the first machining condition including the initial machining current Im0 is preliminarily created and stored. Select an appropriate value from the element data table and decide. It should be noted that as the average machining current Im0, a smaller value is selected as the machining area immediately after the start of machining is smaller (M2).

After that, the average machining current Im (i + 1) of the next stage in the current machining, the machining area SMIN that enables safe machining,
The calculation of the standard machining progress speed Fr is calculated as follows (M3), almost in the same manner as the conventional method.

Im (i + 1) = Im · α (ampere) ... (4) Im (i + 1) = Im + α (ampere) ... (4) ′ Rough machining performed within a range of high average machining current value, especially When using a water-based non-combustible electric discharge machining fluid, it may be possible to improve the final overall machining speed by using equation (4) ′ and adding the rate of change α without using it as a magnification. The equation (4) is the same as the equation (1).

SMIN = Im (i + 1) / Id (square centimeter) (5) Fr = β · Vf / SMIN (mm / m) (6) Average machining current Im (i + 1) at the next stage , The minimum area SMIN that enables stable machining and the standard machining progress speed Fr are collectively referred to as control variables. The expression (6) is the same as the expression (3).

When the above setting is completed, the processing is started. After the start of processing, first, it is determined whether or not a predetermined control interval time stored in advance has elapsed, and the present control system is on standby until the predetermined time has elapsed (M4). The waiting time is set in consideration of the calculation time of the evaluation value K to be described later by sampling and the recalculation time of the control variable which is changed along with the change of the machining condition and the time when the change of the machining condition works effectively. . Therefore, the evaluation calculation is already performed during the waiting for the predetermined time, and the evaluation value K is obtained immediately after the waiting time elapses, and the evaluation value K thus obtained allows the tool electrode 1 and the workpiece 2 to be separated. The discharge state in the gap is determined.

The evaluation value K is an index showing the state of processing,
A large value (K = 1 in the embodiment) is set when the processing energy is excessive (too strong) and immediately before the arc, or when the energy is diffused and the processing is unstable and the processing state is bad and hunting is likely to occur. When the processing state is normal, it takes a small value (0 <K <1 in the embodiment).
Further, when the processing energy is too small (too weak) and is extremely close to the no-load discharge state, the value is smaller than that in the normal state (K = 0 in the embodiment). Therefore, it is necessary to increase the processing energy when the value is close to the normal processing when K = 0, and it is necessary to increase the processing energy when the value is close to the normal processing K = 1. Therefore, the lower limit of the evaluation value K that can be judged as a normal state is set to 0.1
0.3 and the upper limit may be set to about 0.7 to 0.9 (M5).

When it is determined that the machining state is normal, the machining condition is not changed and the jumping operation of the tool electrode 1 is not performed, and the new machining gap state information is obtained after waiting for the predetermined time. obtain. On the other hand, when it is determined that the machining state is abnormal, if the machining energy is weak, it is highly possible that stable machining can be performed even if the electrical machining condition is increased by one step and further machining is performed. If it is too strong or if the machining gap is poor, it is judged that the electrical machining state must be lowered by one step and the machining state must be recovered.

When it is determined that the machining energy is too weak, the machining conditions are not immediately changed, but it is first determined whether or not the jump operation of the tool electrode 1 can be performed (M6). This is because a change in machining conditions, particularly electrical machining conditions, has a great influence on machining, and therefore a jump operation with less influence is attempted first.

The jump operation of the tool electrode 1 is to repeatedly move the tool electrode 1 up and down at a predetermined distance and at a predetermined cycle, and the interval of the jump is set in advance in a plurality of steps depending on the length. There is. If the cycle can be further lengthened or the jump distance can be shortened at the present determination time point, there is a high possibility that the machining efficiency can be substantially increased and the machining state can be made normal by only the jump operation of the tool electrode 1. Only the control of the tool electrode 1 is performed and the machining conditions are not changed (M12).

Therefore, the above interval is changed stepwise,
When the limit value is reached, recovery of the machining state can no longer be expected even if the jump operation is changed, and while the jump control of the tool electrode 1 is maintained, it is calculated and stored separately from the drive pulse of the motor and the servo value. The present machining progress speed and the previously calculated standard machining progress speed Fr are read (M7), and both are compared (M8). When the machining progress speed F at the present stage is slower than the reference machining progress speed Fr, it can be determined that the machining energy is insufficient under the machining conditions at the present stage, and therefore the machining condition is increased by one stage. After the machining conditions are changed, the current average machining current Im is 1
Since it changes in stages, the average machining current I of the next stage
m (i + 1), the minimum area SMIN that allows stable machining, and the standard machining progress speed Fr are recalculated (M9).

When the machining progress speed F is equal to or higher than the standard machining progress speed Fr, it can be determined that the machining state is normal and the machining is performed at a sufficient machining progress speed. It can be said that it is desirable to maintain the current state as it is. Therefore, if the machining is continued without changing the machining conditions, the process waits for a predetermined time to obtain new detection information of the machining gap state (M1).
0).

On the other hand, when it is determined that the machining energy is too strong in M5 (M5), it is not immediately changed the machining conditions as described above, but whether the jump operation of the tool electrode 1 is performed or not is determined. Judgment is made based on the control state of the electrode 1 (M6B).

In step M6B, when the tool electrode 1 does not perform the jump operation but needs the jump,
Alternatively, when the jump operation is performed but the jump cycle can be further shortened or the jump distance can be changed to a longer value, the jumping operation of the tool electrode 1 is performed to promote the removal of machining scraps and recover the gap state. It is highly possible that the tool electrode 1 can be used without changing the machining conditions.
Only the jump operation of is executed (M12B).

On the other hand, if the interval is changed stepwise and the limit value is reached, recovery of the gap state by the jump control cannot be expected, so the current machining can be performed while maintaining the jump control of the tool electrode 1. Progress rate F and standard machining progress rate Fr
And are compared (M7B, M8B). When the machining progress speed F is faster than the reference machining progress speed Fr, the machining state is deteriorated, but the machining energy is not inconvenient for performing electric discharge machining, and therefore the machining condition is not in a state where the machining condition must be changed immediately. Therefore, it is determined whether or not the processing is completed without changing the processing conditions (M10).

When the current machining progress speed F is equal to the standard machining progress speed Fr or is slower than the standard machining progress speed Fr, the discharge state is extremely deteriorated, and machining is continued with the current energy. If so, there is a risk of generating an arc or the like, and therefore the processing condition is immediately lowered by one step to weaken the processing energy (M9B). Since the machining conditions have been changed, the average machining current Im (i + 1) at the next stage, the minimum area SMIN that can be stably machined, and the standard machining progress speed Fr are recalculated.

FIG. 3 is a flow chart showing an example of a method of calculating the evaluation value K of the discharge state in the above embodiment.

In the above embodiment, the voltage value is used as a material for determining the gap state, but the current value may be used instead of this voltage value. That is, the arithmetic expression of the evaluation value K of the discharge state may be changed to match the current value.

The voltage value Vg detected by the gap state detecting means 102 is compared with the reference voltage value Vr stored in advance in the gap state processing means 103 (P1). As the reference voltage value Vr, the servo reference voltage value SV may be used as it is, or a value set on the basis of the current peak value IP or the like may be used. This comparison value represents a deviation from the reference voltage value Vr, and is added and stored as a detection count value to a storage value corresponding to the deviation of the storage unit 201 (P2).

The total number of detections during the sampling period is added to a predetermined storage value of the storage means 201 and stored (P3). The address 201A in this case
And 201H correspond to the respective addresses in the storage means 201, and the stored values indicate the distribution of the deviation state with respect to the reference voltage value Vr. Therefore, here, each inter-electrode voltage data is weighted, and the distribution state of sampling data within a predetermined time is represented. Here, the address 201
A is a comparison voltage value that is smaller than the reference voltage value Vr, and is an address that stores the comparison voltage value that is classified into the most distant stage. Address 201H is the reference voltage value Vr.
This is an address for storing the comparative voltage value that is larger than the comparative voltage value and is classified into the most distant stage. In addition,
The total number of detections is additionally stored in the address 201W. After that, the sampling data is output to the evaluation value calculation means 110 (P4).

Next, the count values stored in the addresses 201A to 201H are set to A to H, respectively, and the total detection count value stored in the detection count address 201W is set to W. Then, in the evaluation calculation means 110,
First, the A / W is calculated. The value of A / W indicates the ratio to the total number of detections when a plurality of detected values of the voltage between contacts during a predetermined time are considerably smaller than the reference voltage value Vr. If the value is more than the specified value (P
5), the evaluation value K is set to 1 (P8). The predetermined value is set to a value within the range of 70 to 100%,
An appropriate value may be determined according to the sampling time, the total number of detections, and the like.

On the other hand, when the value of A / W is less than or equal to the predetermined value (P5), H / W is calculated. The H / W value indicates a ratio to the total number of times of detection when the voltage detection value between the plurality of electrodes during a predetermined time is considerably larger than the reference voltage value Vr. If is greater than or equal to the predetermined value (P6), the evaluation value K is set to 0 (P9). The above-mentioned predetermined value is predetermined as in the case of calculating A / W. If the H / W value is less than or equal to the above predetermined value,
Calculate (A + H) / W. The value of (A + H) / W is a state in which many extreme values are detected, and indicates a ratio in which a value close to the reference voltage value Vr is not detected. In other words, when the value of (A + H) / W is large, the vertical movement is repeated in the state where the voltage value between the electrodes is diverging, and the state is not stable. Therefore, when the value of (A + H) / W is not less than the predetermined value (P7), the evaluation value K is set to 1 (P8). The predetermined value is set to about 50 to 80% depending on the sampling time, the total number of detections, and the like.

When the value of (A + H) / W is not more than the predetermined value, the evaluation value K is A / (A + B + C) or A / (A +
B + C + D) is calculated. Since the values extremely separated from the reference voltage Vr have already been removed by the above A / W and H / W equations, the above A / (A + B + C)
It is possible to judge how much the remaining state is biased to the reference voltage Vr and detected (P10). As described above, the evaluation value K is sent to the machining control means 105, and the machining state between the gaps is judged.

FIG. 4 is a flow chart showing an example of a method of changing the processing conditions in the above embodiment.

When the machining conditions shown in FIG. 2 are changed (M9 and M9B), first, it is determined whether the change of the machining conditions is high or low. As described above, this is determined depending on whether the discharge state is good or bad, that is, the machining energy is excessive or excessive and the gap between the electrodes is deteriorated, and it is judged based on this result (Q
1). Next, it is determined whether or not the processing conditions can be changed (Q2 or Q15). If it is out of the changeable range, further change is impossible, so that even if the change of the processing condition is requested, the processing condition is not changed as a result. In other words, no matter how abnormal the discharge state is, it is impossible to perform machining if the maximum machining conditions including the maximum average machining current ImMAX desired by the operator are exceeded.
Alternatively, it cannot fall below the minimum machining condition including the initial average machining current value Im0 immediately after the start of machining set in step M2. Of course, it is possible to notify the operator by issuing an alarm or the like.

If the processing condition is within the changeable range (Q2 or Q15), the processing control means 105 selects the next step (previous step) from the table of the processing condition and the processing element data stored in the storage means 111. Including returning to)
The processing conditions of are extracted (Q3). Here, the determination is made based on the average machining current Im (i + 1) of the next stage. After that, the difference between the processing condition before the change that has been performed up to now and the processing condition of the next stage extracted in step Q3 is calculated,
The amount of change in the processing conditions is calculated (Q4). Further, the number of divisions (that is, the number of divisions for slightly changing the machining conditions) is determined so that the above conditions can be divided into several and the machining conditions can be gradually changed (Q5).

After that, a work table of the processing condition data for changing the processing condition minute step is created by the processing condition change amount and the processing condition minute change division number and stored in the storage means 113 (Q6). In this way, the change is made for each minute step based on the work table created above (Q7). In this case, since the change of the minute steps is actually performed in an extremely short time, unless a fixed time interval is set for each of the above changes, there is not much difference from the state of not dividing the minute steps. Each change is made to wait for a predetermined time (Q8). The predetermined time may be, for example, 4 to 5 seconds when the number of divisions is 10.

When the work table is created, the range of the number of steps is determined in advance according to the difference between the changed values, and the steps are distributed so as to be substantially equal. For example, if the difference is 1 to 5, the number is the same as the difference, if the difference is 5 to 9, it is 7 steps, and if the difference is 10 or more, it is 10 steps. Further, a change step may be provided depending on the size of the set value. That is, in the above embodiment, for example, when the setting value "IP16" is changed to "IP30", there is a difference between the two values, so that the value is divided into 10, 16 and 1.
7, 18, 20, 22, 24, 25, 27, 28, 30
Allocate as. If you divide it into minute steps like this, 1
It is not suddenly changed from 6 to 30 (IP16 represents a setting step, not a current value). In addition,
The dividing method may be a method other than the above.

As described above, a very unexpected change in the machining progress speed F or the average machining voltage Vg can be prevented by changing the machining condition extremely gently without making a sudden change in the machining condition. Therefore, it is possible to prevent the processing state from becoming unstable. Every time the machining condition is changed in small steps, all the steps of the work table of the machining condition data created in step Q6 are sequentially ended, and it is judged whether or not the required machining condition change is completed (Q9). If the change is completed by repeating the minute step change, the current average machining current Im is calculated (Q10). Then, using the calculated average machining current Im and the preset change rate α, the average machining current Im (i + 1) of the next stage is calculated by the equation (4) or the equation (4) ′. Calculate (Q1
1).

Next, the next stage average machining current Im (i + 1) calculated in step Q11 and the preset maximum current density I
The minimum area SMIN that allows stable machining is calculated from d and (Q12). Further, the volume processing speed Vf is extracted from the data previously stored in the storage means 108 (Q1
3). A new standard machining progress speed Fr is calculated from the minimum area SMIN capable of stable machining and the volume machining speed Vf calculated in step Q12 (Q14). By these calculations, the control variables necessary for the next control are calculated, and the machining condition changing work is completed.

After completing the series of processes as described above,
Returning to FIG. 2, it is determined whether or not the processing is completed (M1
0). If the machining is not completed, the above operation is repeatedly executed, and the machining conditions are always changed gently or the tool electrode 1 is gently jumped to perform the electric discharge machining while stabilizing the machining state.

Needless to say, the positional relationship between the tool electrode 1 and the workpiece 2 is not limited to that shown in the above embodiment. Further, in the embodiment, as the processing conditions are changed, the pulse generating circuit is controlled to change the average processing current value, but the applied voltage value may be changed by changing the resistance value, for example. Further, although the jump conditions are changed, the conditions for the machining fluid jet and the rocking machining can be changed.

[0068]

According to the present invention, when the machining conditions desired by the operator are set, the machining is gradually performed while judging the electric discharge state according to the progress of the electric discharge machining based on the machining conditions desired by the worker. By changing the conditions to reach the final machining conditions desired by the operator, stable electrical discharge machining can be performed, and especially when changing the machining conditions, one step of machining conditions can be changed in several steps. Since it is divided and can be changed very gently, there is an effect that the tool electrode sticks well to the so-called workpiece at the start of processing, and stable processing can be maintained even in the initial stage of processing.

Further, according to the present invention, the gap detection value is sampled for a predetermined time, the deviation of the actual gap state from the reference value is obtained based on the result of this sampling, and the evaluation obtained based on this deviation Since the discharge status is checked based on the value and it is judged whether or not the machining conditions can be changed, the jump operation of the tool electrode is appropriately performed to prevent unnecessary changes to the machining conditions. The processing conditions can be changed, stable processing with less errors can be performed, and safe and high-speed processing can be easily performed even when processing is performed automatically.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of an electric discharge machine showing an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an outline of the method of the present invention.

FIG. 3 is a flowchart illustrating a part of the flowchart shown in FIG. 2 in detail.

FIG. 4 is a flowchart illustrating a part of the flowchart shown in FIG. 2 in detail.

FIG. 5 is a configuration diagram showing an example of a conventional electric discharge machine.

FIG. 6 is a diagram showing a histogram showing the number of detections with respect to an average processing voltage in the above-mentioned embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tool electrode, 2 ... Work piece, 3, 4, 5 ... Motor, 9 ... Power supply, 101 ... Setting means, 102 ... 105 ... Machining condition control means, 106 ... Machining pulse generator, 107 ... Machining condition change setting means, 108 ... Sampling means, 110 ... Evaluation value computing means, 203 ... Computing processing device.

Claims (4)

[Claims] 1. A tool electrode and a workpiece are arranged to face each other, an electric discharge machining voltage is applied to a gap between the tool electrode and the workpiece, and a voltage or current in the gap is detected. The detection result and a predetermined reference value are compared to obtain a comparison result, and the reference machining progress speed and the current machining progress speed calculated based on the comparison result and the machining condition and machining element data stored in advance are calculated. Compare to find the comparison value,
While moving the tool electrode and the workpiece relative to each other based on this comparison value, in the electric discharge machining method for changing the machining conditions based on the comparison value, the voltage or current in the gap is sampled for a predetermined time, The sampling value is weighted, and one of a plurality of predetermined evaluation function formulas is selected according to the distribution state of the weighted sampling value, and the evaluation value is calculated by the weight value and the evaluation function formula. Is obtained and the machining conditions are controlled based on this evaluation value. 2. A tool electrode and a workpiece are arranged so as to face each other, an electric discharge machining voltage is applied to a gap between the tool electrode and the workpiece, and the voltage or current in the gap is detected. The detection result is compared with a predetermined reference value to obtain a comparison result, and the reference machining progress speed calculated based on the comparison result and the machining conditions and machining elements stored in advance is compared with the current machining progress speed. Then, the comparative value is obtained, and the tool electrode and the workpiece are relatively moved based on the comparative value, and in the electrical discharge machining method in which the machining condition is changed based on the comparative value, the machining condition is changed. An electric discharge machining method characterized in that the machining conditions are gradually changed by performing the machining stepwise and dividing one stage of the machining conditions into minute stages by a predetermined number of divisions. 3. A tool electrode and a work piece are arranged to face each other, an electric discharge machining voltage is applied to a gap between the tool electrode and the work piece, and the voltage or current in the gap is detected. The detection result is compared with a predetermined reference value to obtain a comparison result, and the reference machining progress speed calculated based on the comparison result and the machining conditions and machining elements stored in advance is compared with the current machining progress speed. In the electrical discharge machining method, in which the tool electrode and the workpiece are moved relative to each other based on the comparison value and the machining conditions are changed based on the comparison value, the jump operation and the machining are performed. In addition to selectively changing the conditions, the changing of the processing conditions is performed stepwise, and one step of the processing conditions is divided into minute steps by a predetermined number of divisions. Discharge machining method characterized by gradually changing the factory conditions. 4. A machining power supply means for supplying discharge energy to a gap between a tool electrode and a workpiece, a machining pulse generating means for controlling the supplied discharge energy, the tool electrode and the workpiece. Drive means for moving the relative position to the object, drive control means for controlling the drive means and obtaining current position information of the drive means, storage means for storing a plurality of processing conditions and processing elements, and the gap. Of electric discharge machining which detects the voltage value or current value of the electric field and electric discharge state comparing means which compares the detection value detected by the electric gap state detecting means with a preset reference value. In the apparatus, sampling means for sampling a plurality of comparison values compared by the gap state comparing means for a predetermined time and weighting the sampling values; An evaluation value calculation means for selecting one from a plurality of pre-evaluation formulas according to the distribution state of the sampled values, and for obtaining an evaluation according to the value of the weight and the evaluation function formula; The reference machining progress speed calculated based on the machining gap state, the stored machining conditions and machining elements, and the current machining progress speed recognized through the drive control means are compared and judged, and the comparison is made. Based on the determined value, a movement command is sent to the drive control means, or the machining conditions are sequentially changed based on the compared determined value,
An electric discharge machining apparatus comprising: machining condition control means for controlling machining conditions based on the obtained evaluation value.