GB2248032A

GB2248032A - An electric discharge machine for simultaneously machining a plurality of workpieces

Info

Publication number: GB2248032A
Application number: GB9115329A
Authority: GB
Inventors: Wen-Chen Cheng
Original assignee: SHAN IU IND Inc
Current assignee: SHAN IU IND Inc
Priority date: 1990-09-19
Filing date: 1991-07-16
Publication date: 1992-03-25
Also published as: DE9013255U1; CH683971A5; GB9115329D0; CA2051093A1

Abstract

A main machine assembly (91) has a movable ram member (11'), an electrode clamping assembly (12') carried by the movable ram member (11'), a plurality of tool electrodes (131-134) secured to the electrode clamping assembly (12'), and a workbench (15'). Each of the workpieces (141-144) is secured on the workbench (15') immediately below one of the tool electrodes (131-134). A power supply box supplies discharge current independently to each of the tool electrodes (131-134). <IMAGE>

Description

ELECTRIC DISCHARGE MACHINE WITH MULTIPLE TOOL ELECTRODES The invention relates to an electric discharge machine, more particularly to an electric discharge machine incorporating multiple tool electrodes.

Electric discharge (or electric-spark) machining is a metal removal process in which materials that conduct electricity are removed by electric sparks. Machining of a stationary workpiece is accomplished without any grinding or cutting operation so that the workpiece is not subjected to external forces which may cause undesired deformation thereto. Electric discharge machines possess a high degree of precision and can be used for relatively long periods. These machines are preferred if accurate machining is desired.

Figure 1 is an illustration of a conventional electric discharge machine. The electric discharge machine comprises two major parts: a main machine assembly 90 and a power supply box 80. Normally, the main machine assembly 90 is fitted with a movable ram 11, an electrode clamping tool 12 carried by the movable ram 11, and a tool electrode 13 coaxially secured to the electrode clamping tool 12. The metal workpiece 14 is provided immediately below the tool electrode 13 and is held in a stationary position by a magnetic base 15 of a workbench on the main machine assembly 90. The movable ram 11 is drivingly coupled to a servomechanism (not shown). As material removal progresses, the movable ram 11 advances the tool electrode 13 toward the workpiece 14 to maintain a constant spark gap. The discharge current can be controlled via the power supply box 80.

During use, the desired depth of material removal is first set. When machining has reached the set depth, current to the servomechanism is cut-off and machining of the workpiece 14 is stopped. An alarm signal is then generated to indicate that machining has been accomplished. The workpiece 14 is then removed and replaced with a new workpiece.

The main machine assembly 90 also includes various operating circuits and control keys, and a lighting and dielectric fluid supply system. The power supply box 80 contains the necessary power supply control and detector circuits, and several control keys.

Figure 2 illustrates the electrical connection between the power supply box 80 and the main machine assembly 90. Electrical wires 801 transmit power and control signals from the power supply box 80 to the main machine assembly 90. Electrical wires 802 transmit the required discharge current from the power supply box 80 to the tool electrode 13 and to the workpiece 14. The power supply box 80 has an electrical plug 803 for connection with a primary AC electrical outlet.

The conventional electric discharge machine has the following characteristics and limitations: 1. The tool electrode and the workpiece are spaced by a small spark gap. The spark generated melts the small point on the surface of the workpiece that it strikes and forms a crater thereat. This is how the electric discharge machine achieves its machining objective.

2. The surface of the workpiece is gradually eroded through the use of this method and excessive amounts of current tend to roughen the surface of the workpiece.

Therefore, in order to obtain a high degree of accuracy, machining of the workpiece must be accomplished at a very slow pace.

3. Since the desired depth of material removal is set beforehand, manual supervision is unnecessary during machining. When machining has been accomplished, the electric discharge machine automatically stops and an alarm signal is then generated to indicate that the machined workpiece can be removed and replaced with a new workpiece.

4. The conventional electric discharge machine can machine only a single workpiece at a time. Machining a batch of workpieces thus requires a long total machining time. To reduce the total machining time, additional electric discharge machines must be provided. This solution is, however, quite costly.

The main objective of the present invention is to provide an electric discharge machine having multiple tool electrodes to permit simultaneous machining of a plurality of workpieces, thereby reducing total machining time without entailing high equipment costs.

Accordingly, the preferred embodiment of an electric discharge machine of the present invention comprises: a main machine assembly including a movable ram member, an electrode clamping assembly carried by the movable ram member, a plurality of tool electrodes secured to the electrode clamping assembly, and a workbench, each of the workpieces being secured on the workbench immediately below one of the tool electrodes; and a power supply box including a discharge current supplying means to supply discharge current independently to each of the tool electrodes. The discharge current supplying means can be formed as a plurality of electrode sockets provided on the power supply box or as , plurality of independent power supply devices.The present invention thus provides an electric discharge machine having a plurality of tool electrodes in a single main machine assembly to permit simultaneous machining of a plurality of similar or different workpieces to reduce the total machining time without incurring huge equipment costs.

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which: Figure 1 is an illustration of a conventional electric discharge machine; Figure 2 illustrates the electrical connection between a main machine assembly and a power supply box of the conventional electric discharge machine shown in Figure 1; Figure 3 is an illustration of the preferred embodiment of an electric discharge machine with multiple tool electrodes according to the present invention; Figure 4 is a first example of electrical connection between a main machine assembly and a power supply box of the electric discharge machine shown in Figure 3; and Figure 5 is a second example of electrical connection between the main machine assembly and a power supply box of the electric discharge machine shown in Figure 3.

Referring to Figures 3 and 4, the first preferred embodiment of an electric discharge machine with multiple tool electrodes according to the present invention is shown to comprise a main machine assembly 91 and a power supply box 81. The main machine assembly 91 is fitted with a movable ram 11', an electrode clamping assembly 12' carried by the movable ram 11' and tool electrodes, 131-134, secured to the electrode clamping assembly 12'. (Figure 3 shows four tool electrodes 131-134 secured to the electrode clamping assembly 12', although more may be provided thereon depending upon the construction of the electrode clamping assembly 12'). Metal workpieces 141-144 are each disposed immediately below a respective one of the tool electrodes 131-134 and are provided on a workbench 15' of the main machine assembly 91.The movable ram 11' is drivingly coupled to a servomechanism (not shown).

Electrical wires 801' transmit power and control signals from the power supply box 81 to the main machine assembly 91. The power supply box 81 is provided with a plurality of electrode discharge current supply sockets 811-818. Four of the sockets, 811-814, are electrically connected to the tool electrodes 131-134. (The remaining sockets 815-818 are provided to supply discharge current to additional tool electrodes). The electrode sockets 811-814 supply the required discharge current from the power supply box 81 to the tool electrodes 131-134 and to the workpieces 141-144. The power supply box 81 further has an electrical plug 803' for connection with a primary AC electrical outlet.

The spark gaps between the tool electrodes 131-134 and the respective workpieces 141-144 are preferably equal, so that machining of the workpieces 141-144 can be accomplished at an equal pace. Equal machining pace is desirable especially if the workpieces are of the same type, and the desired machining is the same for all workpieces.

The preferred embodiment can also be used even if the specifications of the workpieces are different, such as different machining depths are required.

Assuming that depths of 0.05 mm and 0.03 mm are required, those workpieces which require a machining depth of 0.05 mm are first machined up to a depth of 0.02 mm. Machining of all the workpieces is then performed at an equal pace for the remaining depth of 0.03 mm. Machining of all the workpieces thus ends at roughly the same time, and the electric discharge machine generates an alarm signal to indicate that the machined workpieces can be removed and replaced with a new set of workpieces.

Figure 5 is a second preferred embodiment of an electric discharge machine with multiple tool electrodes according to the present invention.

Electrical wires 801" are provided to transmit power and control signals from a power supply box 82 to the main machine assembly 91 of the electric discharge machine. The operation of the second preferred embodiment is substantially similar to that of the first preferred embodiment and will not be detailed further. The main difference between the first and second preferred embodiments lies in the construction of the power supply boxes 81 and 82. The power supply box 82 comprises a plurality of independent power supplies 821-826. Each of the independent power supplies 821-826 has an electrical plug 804-809 for connection with a primary AC electrical outlet. Four of the power supplies, 821-824, are electrically connected to the tool electrodes 131-134 and the workpieces 141144, supplying the required discharge current. The remaining power supplies 825-826 are not connected to the tool electrodes 131-134 but instead supply the required power to drive the servomechanism and other parts of the main machine assembly 91.

The present invention thus provides an electric discharge machine which has a plurality of tool electrodes in a single main machine assembly. This permits simultaneous machining of a plurality of similar or different workpieces. This is in contrast with conventional electric discharge machines which permit machining of only one workpiece at a time.

Claims

I CLAIM:

1. An electric discharge machine for simultaneously machining a plurality of workpieces, comprising: a main machine assembly including a movable ram member, an electrode clamping assembly carried by said movable ram member, a plurality of tool electrodes secured to said electrode clamping assembly, and a workbench, each of said workpieces being secured on said workbench immediately below one of said tool electrodes; and a power supply box including a discharge current supplying means to supply discharge current independently to each of said tool electrodes.

2. The electric discharge machine as claimed in claim 1, wherein said discharge current supplying means comprises a plurality of electrode sockets provided on said power supply box, each of said tool electrodes being electrically connected to one of said electrode sockets.

3. The electric discharge machine as claimed in claim 1, wherein said discharge current supplying means comprises a plurality of independent power supply devices, each of said tool electrodes being connected to one of said power supply devices.

4. The electric discharge machine as claimed in claim 2, wherein said power supply box includes an electrical plug for connection with a primary AC electrical outlet.

5. The electrical discharge machine as claimed in Claim 3, wherein each of said independent power supply devices has an electrical plug for connection with a primary AC electrical outlet.

6. The electric discharge machine as substantially described hereinbefore with reference to the accompanying Figures 3-5.

7. An electric discharge machine for simultaneously machining a plurality of workpieces, comprising: a main machine assembly including an electrode clamping assembly, a plurality of tool electrodes secured to said electrode clamping assembly, and a workbench positioned to receive, each of sasid workpieces immediately below one of said tool electrodes; and a power supply including a discharge current supplying means to supply discharge current independently to each of said tool electrodes.