JPH0259239A - Numerically controlled machine tool with electro-discharge machine function - Google Patents

Abstract

PURPOSE:To perform machine work and electro-discharge machining both with one NC machine by impressing the specified voltage on a gap between a working electrode and a work held by a tool holding means, and controlling a feed rate of the electrode based on a detected electrical signal in accordance with the setting function. CONSTITUTION:A working electrode M5 is held by a tool holding means M1 of a numerically controlled machine tool, and the specified voltage is impressed on a gap between the electrode and the work M2 from an electro-discharge machining power supply means M6, thus electro-discharge machining is started. Then, an electric signal level between the electrode M5 and the work M2 is detected by a detecting means M7, making an override control means M4 intervene in a tool travel control means M3 based on this detected electric signal, and a feed rate of the electrode M5 is controlled by an electro-discharge machining control means M8 according to the preset function, thus electro-discharge machining for the work M2 is carried out. Thus, machine work and the electro-discharge machining both can be done with one NC machine tool by only making simple software intervene in NC machining software, so that any drop in accuracy of finishing due to work setting and vice versa can be eliminated.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is a numerically controlled machine 8! that performs cutting of a workpiece, etc.
In particular, the present invention relates to a numerically controlled machine tool that can perform electrical discharge machining as well as cutting.

(Prior art) -a. Most of the processing of molds with three-dimensional curved surfaces, such as plastic molds, die-casting molds, and forming molds, is performed by machining centers (hereinafter sometimes referred to as MC). . However, machining holes in irregular shapes, such as corners and ellipses, and creating ribbed shapes are impossible with cutting.
We have no choice but to rely on electrical discharge machining.

Therefore, in addition to the MC, a dedicated die-sinking electrical discharge machine was required to machine the molds and the like.

(Problems to be Solved by the Invention) However, using two processing machines to process one workpiece increases the number of processing steps, and there is a risk that processing accuracy may decrease as the workpiece is attached and detached. This problem is one of the obstacles to the recent trend towards automation of numerically controlled (hereinafter also referred to as NC) machine tools and the tendency to significantly improve machining accuracy.

Moreover, arranging two machines, the MC and the electric discharge machine, is not preferable from a safety standpoint since the scale does not require a large amount of installation space and the work is crowded.

On the other hand, in order to solve these problems, there has also been a proposal to carry out electrical discharge machining by attaching an attachment to the tool holder itself, in which a surf drive machine ellipse using a piezoelectric element or the like is attached to the main shaft. However, this proposal has the following disadvantages: the number of servo axes is limited to one axis, the weight and shape of the tool holder are large, making it unsuitable for automatic tool change (ATC), and the cost increases. The above problems have not yet been solved.

In order to solve the above-mentioned problems, the numerically controlled machine tool having an electrical discharge machining function of the present invention utilizes tool movement control means and override control means provided in numerically controlled machine tools such as machining centers to carry out cutting operations. The structure is such that electrical discharge machining can also be performed at the same time.

(Means for Solving the Problems) A numerically controlled machine tool having an electric discharge machining function according to the present invention has a tool gripping means (M
l) to move and feed the tool gripped by the workpiece (M2).
A numerically controlled machine tool that performs cutting of a workpiece, etc., and includes at least a tool movement control means (M3) that controls relative to the tool movement control means (M4), and an override control means (M4), the tool gripping means (Ml) electric discharge machining power supply means (M6) for applying a predetermined voltage between the electric discharge machining electrode (M5) gripped by the electric discharge machining electrode (M5) and the workpiece (M2);

electrical signal detection means (Ml) for detecting an electrical signal between the electrode (M5) and the workpiece (M2); and the override control based on the electrical signal detected by the electrical signal detection means (Ml). Electrical discharge machining control means (M8) that causes the means (M4) to intervene in the tool movement control means (M3) and controls the feed rate of the electrode (M5) according to a preset function to perform electric discharge machining of the workpiece. It is characterized by:

(Function) According to the above configuration, when electric discharge machining is started on the workpiece (M2) by the electric discharge machining electrode (M5) held by the tool gripping means (Ml) of the numerically controlled machine tool, The electrical signal detection means (Ml) is caused to detect the electrical signal level between the electrical discharge machining electrode (M5) and the workpiece (M2). The electric signal level detected by the electric signal detection means (Ml) is in a functional relationship with the interval between the electric discharge machining electrode (M5) and the workpiece (M2), so that Under machining conditions, an index electric signal level corresponding to an interval at which a certain degree of poor discharge condition is obtained is set in advance, and comparison calculations are made with this level to determine the electrical discharge machining electrode (M5) and workpiece (M2). ) is suitable for the electrical discharge machining conditions at that time.

For example, if the detected electric signal level is higher than the index electric signal level, it means that the distance between the electric discharge machining electrode (M5) and the workpiece (M2) is larger than the expected value, and the distance is reduced. To do this, the override control means (M4) is activated to change the set value of the axis feed speed program of the tool movement control means (M3) in accordance with the result of the comparison calculation, and the operation of the electric discharge machining electrode (M5) is controlled. Let it be controlled. In this way, a plurality of types of indicator electric signals suitable for the material, shape, machining mode, etc. of the workpiece to be subjected to electrical discharge machining are set in advance, and the electric signal detecting means (M7
), and according to the calculated value, the override control means (M4) intervenes in the tool movement control means (M3) to perform intermittent feeding of the feed axis, changing the feed speed, stopping, etc. to control the
If the calculated value for a certain index electric signal level value is, for example, zero or negative, the distance between the electric discharge machining electrode (M5) and the workpiece (2) is zero, in other words, they are in contact and electrically It is determined that there is a short circuit, that is, electric discharge machining is impossible, and the electric discharge machining control means (M8) temporarily interrupts the electric discharge machining, and the override control means (M4) intervenes in the tool movement control means (M3). Electrode for electric discharge machining (
M5) is moved back by the required distance along the opposite trajectory to adjust the discharge conditions, and then the discharge machining is restarted.

(Implementation @) The configuration of an embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a flowchart showing the configuration and operation of the numerical control system of the NC machine tool having the electric discharge machining function. 1 is an electric discharge machining start processing step, 2 is a process between the discharge tip of the electric discharge machining electrode and the workpiece point of the workpiece,
In other words, the finger speed voltage Et1 is set in the electrode voltage Es detection processing step 3, which measures the potential difference of the gap, and the gear judgment step A corresponding to a relatively large gap.
In addition, 4 is set to the reference voltage Et2 in the gear judgment B step corresponding to a relatively medium-sized gap, and 5
The finger speed voltage Et3 is set in the gap judgment C step corresponding to a relatively small cap. Reference numeral 6 denotes a shaft feed speed setting process A, 7 a shaft feed speed setting process B, and 8 a step of a shaft feed speed setting process C1, each of which sets a coefficient by which the basic shaft feed speed is multiplied.

9 is an overload control processing step in which interrupt operations are performed based on the information values from each step of 6.7°8.
Reference numeral 10 is a tool path program start processing step knob that executes the main block possessed by the NC machine tool incorporating the electric discharge machining function. 11 is a backward program start processing step in which a user macro associated with the main program is started. Reference numeral 12 denotes a backward program end processing step, which is linked to the tool path program start processing step 10. Reference numeral 13 indicates an end processing step of the main program, and this step constitutes a numerical control system for a series of electric discharge machining processes. Next, a simplified functional block diagram (Fig. 3) of an NC machine tool including the numerical control system shows the operation of the above configuration.
This will be explained using the following. Table 15 of NC machine tool 14
A workpiece 16 is placed on top with an insulating mat 17 interposed therebetween, and is waiting to complete a series of machining steps and move on to the next electrical discharge machining step. An electric discharge machining electrode 20 is installed at the tip of one main shaft on the head 18 of the NC machine tool 14.
The cutting tool 2 in the previous process is cut by a so-called ATC device 21.
It was replaced with 2 and put away. and head 18
The table 15 is moved vertically by the Z Shobara motor 23, and horizontally by the X Shobara motor 24, and furthermore, the table 15 is moved by the Y &
Since it is possible to drive and move an arbitrary distance in the front and rear directions by the a motor 25, the tip 26 of the electric discharge machining electrode 20, that is, the part corresponding to the cutting edge of a cutting tool in machining, can be moved within a predetermined range. It can be freely positioned in a three-dimensional space and can process and mold the workpiece 16 into a three-dimensional curved surface. The electric discharge machining power supply unit 27 supplies electric discharge power to the electric discharge machining electrode 20 and the workpiece 16 with positive and negative polarities, or negative and positive polarities, respectively. The voltage measurement circuit 28 measures the potential difference between the tip of the electric discharge machining electrode 20, that is, the electric discharge machining portion 26 and the portion to be machined of the workpiece 16. The two central control units are configured as logical operation circuits from well-known CPU, ROM, RAM, etc., and perform overall control of all operations such as movement, positioning, measurement, turning on, and turning off of each of the above-mentioned components.

When the processing by the two central controllers now moves to machining start processing step 1, the main program starts and electrical discharge is applied to the workpiece 16 from the power supply unit 27, which is a power supply means for electrical discharge machining, via the electrical discharge machining electrode 20. machining energy is inputted and predetermined electrical discharge machining is started on the workpiece 16. At the same time, the voltage measurement circuit 28 is commanded by the inter-electrode voltage Es detection processing step 2, and the tip 26 of the electrical discharge machining electrode 20 and the workpiece are The distance between the tip 26 of the electrical discharge machining electrode 20 and the machining point of the workpiece 16, which is separately set for a certain workpiece! (hereinafter referred to as a gap) is compared with the finger ring voltage Et1 corresponding to Et1, and if Es>Etl, it is affirmatively determined that the gap is relatively large, and the process moves to Step 6 of the shaft feed speed setting process.0 Next, the shaft feed speed is set. Process A step 6 multiplies the basic axis feed speed program setting value by a preset coefficient of 100% and moves to the next override control process step 9. In step 9 of the override control process, the main program, which is the tool path control means, is executed by multiplying the basic axis feed speed program setting value by 1°0%, that is, in order to advance the axis feed with the basic axis feed speed program setting value unchanged. Make it run.

On the other hand, if Es<Etl, the gap is determined to be relatively medium in step 3, and the process moves to gear determination B step 4. Gear Tsubu Judgment B Step 4:
Compared with the index voltage Et2, which is set corresponding to a relatively medium gap, if Es>Et2, the gap is determined to be relatively medium, and the process moves to step B of the axis feed speed setting process. 9 Next, axis feed speed setting process B step 7
Then, the basic axis feed speed program setting value is multiplied by a preset coefficient of 20% and the process moves to step 9 of the override $ control process. In step 9 of the override control process, the basic axis feed speed program setting value is multiplied by 20%.
That is, the main program, which is the tool path control means, is run in order to advance the axis feed at a speed of 20% of the basic axis feed speed.

On the other hand, if E s <E t2, it is determined that the gap is small, and the process moves to gap determination C step 5. In gap judgment C step 5, the ring voltage Et3 is compared with the ring voltage Et3, which is set corresponding to a relatively small gap, and if [E s > E t 3, the gap is judged to be small, and the shaft feed speed is set. The process moves to step C step 8. Axis feed speed setting fr! 1. In C step 8, the basic axial feed speed program setting value is multiplied by a preset coefficient of 0%, that is, a coefficient for stopping the axial feed, and the process moves to the next override control processing step 9. On the other hand, E s
If <E t3, the gap is zero, that is, a command to interrupt the gap between the tip 26 of the electric discharge machining electrode 20 and the machining point of the workpiece 16 is output, and at the same time, the process moves to step 11 of the backward program start process. and run the user macro regression program. Here, the index voltage Et1. Et
2. For each of Et and 3, the axis feed speed coefficient is 100%.
, 20%, and 0%, but it is also possible to correspond to any voltage between electrodes from 100% to 0%. Hereinafter, a more specific explanation will be given with reference to FIGS. 4 [A] and [B] to FIG. 5. As shown in FIG. 4 [A], in addition to the main program for tool movement control, there are user macros 30 for linear movement, user macros 31 for clockwise CW circular arc movement, and user macros 31 for counterclockwise CCW circular movement. A user macro 32 is prepared for this purpose, but in this embodiment, a macro for CW arc movement will be explained. At the current position P1 (Fig. 5) of the machining process ■ of the user macro 31, an interrupt signal lNTl corresponding to the negative judgment in step 5 is generated.
When is output, in step 34, the moving direction of the electric discharge machining electrode 20 is changed from CW to CCW, and the target point is changed to the target point P.
Parameters are changed from E to starting point Ps, and the axis feed rate is changed from machining feed rate to rapid feed rate, and at the same time, the timer is turned on. Then, the backward stroke (2) as step 35 runs the backward program toward the starting point PS of the machining stroke (2).

Then, when the interrupt signal INT2 is issued from the timer at the current position P2 of the backward stroke (■) according to a preset time period according to the machining conditions, in step 36, the direction of movement of the electrical discharge machining electrode 20 is changed to CC for the return stroke (■).
From W to CW, and the target point from the starting point PS to the target point PE
Then, the timer is turned off at the same time as each parameter is changed. When the starting point P2 is moved to the target point P1 for the return process ■, in step 38, the target point is moved from the current position P1 to the target point PE (end point) in order to continue the machining process ■ as step 33. The speed is changed from the rapid feed speed to the machining feed speed, and the parameters are changed, respectively, and the normal electric discharge machining is continued again from the current position P1 of the machining process (2).

Due to the structure and operation of the above-mentioned embodiment, -A, unlike the case where a machining function is added to an electric discharge machine which has poor rigidity for machining, an electric discharge machining function is added to a machine tool with high rigidity. This makes it possible to perform continuous machining from rough cutting, which requires heavy loads, to electrical discharge machining, which requires extremely light loads, with one machine, and eliminates the need for workpiece mounting and tool setup changes, which previously required double work. It is said that the processing process has been shortened and simplified by reducing the number of parts to one time.
The distance between the tip 26 of the electrical discharge machining electrode 20 and the machining point of the workpiece 16, that is, the gap, is an important condition for maintaining the required machined surface and machining accuracy. By setting three kinds of finger voltages such as Etl=Et2 and Et3 and comparing the magnitude with the actual gap voltage Es, more fine control was enabled. Furthermore, this finger speed voltage is as described above (
Since it is possible to carry out stepless comparison calculations with Es from Etl to Et3, it is possible to perform even more fine control if necessary.

In addition, if machining cannot be continued due to some reason during electrical discharge machining, such as contact between the electrode and the workpiece, a user macro, which is one of the existing software included in the numerical control machine tool, can be used. The electrode is temporarily stopped, moved back to the desired position, and then returned to the original position, during which the conditions for electrical discharge machining are adjusted, and the electrical discharge machining is restarted and continued as before. The effect was that tool handling, which is unique to electric discharge machining, can be performed easily.

(Effects of the Invention) As explained in detail above, the present invention provides a numerically controlled machine tool such as a normal machining center, which includes a tool holder for one electric discharge machining electrode, a power source for electric discharge machining, and an electric discharge machining machine. By simply adding a voltage measuring device between the working electrode and the workpiece and inserting simple software into existing NC machining software, two different types of machining, machining and electrical discharge machining, can be performed using one machine tool. I made it possible. This has the effect of reducing the number of machining steps and reducing wasted time, as well as eliminating the reduction in machining accuracy that accompanies the attachment and detachment of the workpiece.

In addition, since all processes can be performed with one machine tool, the installation space of one machine tool is sufficient, which is economical, and allows the work to be performed using two different types of machines. It also has the effect of improving worker safety by eliminating roadblocks in the area.

On the other hand, unlike the tool holder that has a built-in servo mechanism for electrical discharge machining, a tool holder of the same size as a normal machining tool holder can perform ATC, which is one of the important functions of MC. The electrodes that match the machining conditions can be used in ATC in the same way as cutting tools, without any effect on the tool or electrode exchange function, without incurring special costs, and without increasing the amount of machine balls.
This has the effect of allowing arbitrary electrical discharge machining to be performed on a workpiece by operation.

In addition, for electrical discharge machining, it is possible to use highly rigid NC machine tools, which further improves machining accuracy, and also makes it easier to drill diagonal holes by tilting the electrode, and to perform edge machining by swinging the table. This has the effect of making it possible to employ the company.

Furthermore, in electrical discharge machining, wear of the electrical discharge machining electrode occurs in the same way as cutting tools in machining, but according to this machining center, a cutting or polishing means is installed on the table, and the machining center For machining purposes, the electric discharge machining electrode that is stored in its original state can be regenerated or reshaped into any shape by cutting or polishing it under numerical control. Another benefit is that we were able to derive a means of supporting the propulsion of the electrical discharge machining process, which was not available even with dedicated machining machines.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of an NC machine tool having an electric discharge machining function according to the present invention, FIG. 2 is a functional flowchart of the NC machine tool, and FIG. 3 is a simulated functional block diagram of a machining center including the electric discharge machining function. Figure 4 is a functional block diagram of the software that retracts the electrode for electrical discharge machining, Figure 5
The figure is a concrete diagram of the stopping, retreating, and restoring sequence of the electric discharge machining electrode. Ml-tool gripping means M2. Workpiece M3-tool movement control means M4. Override control means M5. Electric discharge machining electrode M6゜M7゜1゜2゜3゜4゜5゜8゜9゜10゜11゜12゜13゜14゜16゜20゜Power supply means for electric discharge machining Electrical signal detection means Electric discharge machining control means Electric discharge machining start processing step Voltage between electrodes Es detection processing step Gear wheel judgment A step Gear wheel judgment B step Gap judgment C step Axis feed speed setting process A step Axis feed speed setting process B step Axis feed speed setting process C step Overclocking control Processing step Tool path program start processing Processing step Backward program start processing step Backward program end processing step Tool path program end processing step Machining center <MC') Workpiece electric discharge machining electrode ATC (automatic tool changer) 26° 27° 28° 29゜30゜31゜Electrode tip for electric discharge machining Unisito voltage measurement circuit central control unit for electric discharge machining electrode tip User macro (straight line) User macro (CW clockwise circular arc) User macro (CCW counterclockwise circular arc) Figure 5 Applicant Yamazaki Mazatuku Co., Ltd. Representative Teruyuki Yamazaki Ml. M2゜M3゜M7゜Tool gripping means Work tool movement control means Override control means Electrode for electric discharge machining Power supply means for electric discharge machining Electrical signal detection means Electric discharge machining control means Electric discharge machining start processing step Voltage between electrodes Es detection processing Step Gear Knob judgment A step Gap judgment B step Gap 1:11 cut C step Axis feed rate setting process A step Axis feed rate setting process B step Axis feed rate setting process C step Overdrive control process Step Tool path program start process Step Backward program start Processing step Backward program end processing step Tool path program end processing step ■4 16°20°21°26°28° Machining center (MC> Electrode ATC for work electrical discharge machining <Automatic tool changer> Electrode for electrical discharge machining Tip end for electrical discharge machining Power unit voltage measurement circuit central control device 30 User macro (straight line) 31, User macro (CW clockwise arc) 32, User macro (CCW counterclockwise arc) [A] Fig. 4 [B]

Claims (2)

[Claims] (1) A numerically controlled machine that performs cutting, etc. of a workpiece, comprising at least a tool movement control means that controls the movement and feed of the tool gripped by the tool gripping means relative to the workpiece, and an override control means. The machine includes: electric discharge machining power supply means for applying a predetermined voltage between the electric discharge machining electrode held by the tool gripping means and the workpiece; and electricity for detecting an electric signal between the electrode and the workpiece. a signal detection means; and the override control means intervenes in the tool movement control means based on the electric signal detected by the electric signal detection means, and the feed rate of the electrode is controlled according to a preset function to perform electrical discharge machining of the workpiece. A numerically controlled machine tool having an electrical discharge machining function, characterized by comprising: electrical discharge machining control means for performing the following; (2) The electric discharge machining control means interrupts the electric discharge machining and stops feeding the electrode when the electric signal detected by the electric signal detection means becomes a certain value or less; A numerically controlled machine having an electric discharge machining function according to claim 1, characterized in that the electrode is moved back to an arbitrary position by a tool movement control means, and then the electric discharge machining is restarted. machine.