FR2754482A1 - Wire feed controller for electro-erosion machine - Google Patents

Abstract

The system comprises wire reel rotating on a shaft with differing longitudinal sections, connected at one end to a traction plate and at the other to a cone which can slide or lock on the shaft. The cone is positioned against the wire reel, sending the wire to a wire accumulator consisting of fixed pulleys and a pulley on a tilting arm, and then to the working zone of the machine. A sensor of the arm position supplies information to a programmed microprocessor which controls the driving motor for the traction plate.

Description

CUTTING AND THREADING METHOD AND DEVICE
AUTOMATIC FOR ELECTROEROSION MACHINE
One of the biggest problems in EDM machines is threading.

 The machine can be equipped with an automatic threading system, but if this fails, for example, as a result of repeated unsuccessful threading attempts, the thread, which is very delicate, is damaged.

 At other times there are involuntary wire breaks or you have to start working with a new spool of wire or start another job, the previous one being finished, etc.

The area of the wire in which the deterioration has occurred is unusable, which puts the manufacturers of EDM machines in front of the following problems
a) how to separate the unusable wire area from the rest of the intact wire
b) how to eliminate the unusable wire zone
c) how to facilitate the passage of the intact wire through the holes and the guides for its threading
d) presentation of the thread for threading under optimal conditions of hardness, straightness and section.

 The solutions to these problems are described in so many documents, most of them recent, that they constitute the best proof of their ineffectiveness in solving them.

 The applicant has developed a method and a corresponding device which overcomes the problems mentioned in a simple manner.

The essence of the invention consists in providing wheels with versatile traction and braking functions, increasing the temperature by effect
Joule at the point where it is desired that the wire is cut, by concentrating on said point the passage of electrical energy, to automate the recovery of the cut wire, unusable and to improve the guiding of the wire.

 In order to better understand the object of the present invention, there is shown in the drawings a preferred practical embodiment, capable of accessory modifications without departing from the scope of the present invention.

 Figure 1 is a schematic representation of the arrangement of the elements that make up the system according to the invention.

 An example of a practical, non-limiting embodiment of the present invention is described below.

 All electronic and actuation elements are under the control of a programmed microprocessor (not shown).

 The system consists of a servo motor (ml) on which is placed a coil (b) of wire feed (1), the wire (1) being routed by means of conventional feed devices to a wheel d 'supply (3) disposed between two pressure rollers (2), (2) each exerting pressure under the action of springs (S1).

 The feed wheel (3) is actuated by a servo motor (m2) with progressive clutch (ce), so that when the servo motor (m2) is running and engaged, the feed wheel (3 ) or in drive mode, and when the servo motor (m2) is stopped and engaged, the feed wheel (3) acts as a brake. And this, depending on the desired progression, by using the CPU on the progressive clutch (ce).

 The feed wheel (3) has a coating (31) of elastic material capable of degrading with heat. This is the reason why a small tube (33) for air cooling of the area of contact of said coating (31) with the wire is provided, near the outlet of the wire (1) from the feed wheel. (1).

 The feed wheel (3) also has an encoder (32) which measures the rotation of the wheel (3) because, as will be seen later, the feed wheel (3) must turn a determined number of times to each type of wire (1) used.

 At the outlet of the feed wheel (3) are arranged a first guide (gl) and a tube (13) whose lateral surface is removable to gain access to the wire (1) from the outside.

 At the outlet of the tube (13) are successively arranged a second guide (g2), two electrodes (e2) which, under the action of conventional means, for example pneumatic cylinders, and under the control of the CPU, are / are not in contact with the wire (1), and a third guide (g3).

 The wire (1) then passes between the two stretching wheels (8) which are electrically conductive and which are actuated by a motor (m3) with reducer (rl) and which can approach / move apart. one another under the control of the UC.

 I1 is then provided with a wire presence detector (6) and a deflector (7) with a vertical guide cone (tl) for guiding the wire (1), under normal working conditions, and a guide cone (t2 ) of used wire, to conduct the used wire (11).

 The deflector (7) moves under the action of the pneumatic cylinder (9).

 The operation is described below.

 The wire (1) can be presented in two ways.

 I. The thread is in poor condition due to accidental breakage or failure to thread repeatedly, etc. Thread in abnormal situation.

 II. The thread is in good condition and correctly threaded, but one job is finished and another must be started.

Both possibilities have two basic phases
- wire preparation
- thread cutting and threading
Possibility I - Wire (1) in abnormal situation.

 Wire preparation phase.

 I1 must remove the part of the wire (1) in poor condition.

 When the wire (1) is in poor condition (in the event of a break, for example), a conventional break detector sends a corresponding signal which the CPU transforms into an order transmitted to the servo motor (m2) so that the wheel d 'feed (3) of wire (1) reverses its direction of rotation to recover the wire instead of routing it to the machine.

When the detector (6), inductive for example, detects that there is no wire (1), the following main actions occur
a) The feed wheel (3) is free or slightly braked, depending on the CPU program, and the stretching wheels (8) approach each other and drive the wire (1) downwards.

 b) the deflector (7) places the cone-guide (t2) of used wire under the detector (6) in the director of the wire and, by means of the tube (12), routes the used wire (11) towards blades ( 11) which cut it into pieces and deposit it in the storage tank (10) of used wire.

After a predetermined period of time or a number of turns of the feed wheel (3) measured by the encoder (32), according to the quantity of wire which it is desired to reject, the CPU commands the following operations
c) maintaining the approximation of the stretching wheels (8), but acting as a brake, without letting the wire pass (1), and driving the wire (1) upwards through the feed wheel (3), which , with its encoder (32), rotates by a predetermined angle (a), producing a predetermined stretch of the wire (1), programmed in the CPU for each type of wire used
d) at the same time, the closing of the first electrical circuit formed by: a first power source regulated in intensity (P1), which can be varied by program, a pressure roller (2), a wire ( 1) and stretching wheels (8), by means, for example, of contact electrodes (el), closure by which the wire (1) heats up producing a stretching and a reduction in its section, for example from 250 p to 230>.

 Once the feed wheel (3) rotated by the predetermined angle (a) for each type of wire mentioned above, we enter the next phase.

 Wire cutting and threading phase.

a) The feed wheel (3) remains immobilized, fully braked, the stretching wheels (8) remain close together by exerting a pull down on the wire
b) at the same time, the first electrical circuit opens and the second circuit, formed by the following elements, connects: second power source regulated in intensity (P2), which provides a significant intensity, greater than that of the first electrical circuit, cutting electrodes (e2) (opposite to avoid producing a curvature of the wire (1) upon contact), stretching wheels (8)
c) by supplying the wire (1) with high caloric energy, in a reduced cutting zone (e2) (8), and by maintaining the mechanical tension, the wire (1) is broken
d) the stretching wheels (8) convey the lower section towards the used thread guide cone (t2) and towards the storage tank (10)
e) the automatic jack (9) positions the deflector (7) with its vertical guide cone (tl) under the detector (6), the cutting electrodes (e2) separate, the stretching wheels (8) separate , the feed wheel (3) drives the wire (1) down, passing it, as in a conventional threading, through the outlet guide (A) of the upper head (c) of the machine.

Possibility II
Wire preparation phase.

It is carried out in the same way as for possibility I, but without operations (a) and (b)
Wire cutting and threading phase
a) the stretching wheels (8) come together and, acting as a brake, prevent the passage of the wire (1), while the feed wheel (3) drives the wire (1) upwards
b), c) as explained for possibility I
d) the stretching wheels (8) separate and the drive elements of the lower head (not shown) convey the lower part of the wire
e) the cutting electrodes (e2) separate, the feed wheel (3) drives the wire (1) (upper part) downwards and the operation continues as in conventional threading.

Claims (6)

 1. - Automatic cutting and threading device for EDM machine, comprising an upper guide head and a lower wire guide head, characterized in that it comprises  a) a supply coil (b) of wire (1) which routes it to  b) a feed wheel (3) which can act as a motor or brake and, downstream,  c) electrically conductive stretching wheels (8) which can separate / approach the wire (1) and act as a drive or brake, and  d) a wire presence detector (6), then  e) a deflector (7) with a used wire guide cone (t2) communicating with a storage tank (10) with means for actuating the deflector and placing the used wire guide cone (t2) on the director wire (1) or remove it  f) a first source (P1) of electrical energy which feeds at will the wire (1) between the feed wheel (3) and the stretching wheels (8)  g) a second source (P2) of electrical energy which feeds at will the wire (1) between the stretching wheels (8) and cutting electrodes (e2) which, under the action of controlled actuation means by the CPU, are / are not in contact with the wire (1), said cutting electrodes (e2) being arranged near the stretching wheels  h) electrical and electronic means for actuating all the above elements under the control of a programmable microprocessor.  2. - Automatic cutting and threading device for an EDM machine according to claim 1, characterized in that between the feed wheel (3) and the stretching wheels (8) are successively a first guide (gl), a tube (13) with lateral access from the outside, a second guide (g2) and a third guide (g3) framing the cutting electrodes (e2).  3. - Automatic cutting and threading device for EDM machine according to claim 1, characterized in that the deflector (7) is actuated by a pneumatic cylinder (9) and comprises a vertical guide cone (tl) and a used thread guide cone (t2) connected to a tube (12), the outlet opening of which opens into the used thread tank (10).  4. - Automatic cutting and threading device for EDM machine according to claim 1, characterized in that the feed wheel (3) comprises an outer coating (31) of flexible material and an encoder (32) for measure its angle of rotation.  5. - Method of automatic cutting and threading for EDM machine, carried out with the device according to claim 1, characterized in that it comprises wire detectors in abnormal situation, the signals of which are received by a programmed microprocessor which starts the process, comprising  a) a wire preparation phase in which the feed wheel (3) reverses its direction of rotation and recovers the wire (1) by driving it until the detector (6) indicates that it has there is more wire (1), the CPU then controlling the following operations  Aa) release of the feed wheel (3) and driving of the wire (1) downwards by the stretching wheels (8) during a predetermined number of turns, at the same time as,  Ab) the deflector (7) places the guide cone (t2) of used wire in the director of the wire (1)  Ac) the stretching wheels (8) act as a brake, preventing the passage of the wire (1) and the feed wheel (3) drives the wire (1) upwards, at a predetermined angle (a), at the same time as  Ad) connects the first electrical circuit which is closed by the wire (1) between the pressure roller (2) and the stretching wheels (8), during the time when the feed wheel (3) rotates a predetermined angle (a), then the CPU intervenes  b) a cutting and threading phase in which the CPU successively controls the following operations  Ba) braking of the feed wheel (3), preventing the passage of the wire and entrainment of the wire (1) downwards by the stretching wheels (8), at the same time as,  Bb) opens the first electrical circuit and closes the second electrical circuit, which provides a higher intensity than that of the first electrical circuit and which is closed by the wire in a small area between cutting electrodes (e2) and the wheels stretching (8),  Bc) the connection lasts until the wire breaks (1), leaving a section of used lower wire,  Bd) the stretching wheels (8) continue to drive the used lower section of wire by pulling it towards the storage tank (10).  Be) the vertical guide cone (tl) is placed on the wire director (1), the stretching wheels (8) separate and the feed wheel (3) drives the wire (1) downwards to put it on.  6. - A method of automatic cutting and threading for an EDM machine according to claim 5, characterized in that the wire being threaded and a new work having to be started, the microprocessor controls the following successive phases  a) a wire preparation phase in which  Aa) the stretching wheels (8) act as a brake, preventing the passage of the wire (1) and the feed wheel (3) drives the wire (1) upwards, at a predetermined angle, at the same time than  Ab) connects the first electrical circuit which is closed by the wire (1) between the pressure roller (2) and the stretching wheels (8)  b) a cutting and threading phase in which the CPU successively controls the following operations  Ba) the stretching wheels (8) act as a brake, preventing the passage of the wire (1) and the feed wheel drives the wire (1) upwards,  Bb) opening of the first electric circuit and closing of a second electric circuit, which provides a higher intensity than that of the first electric circuit and which is closed by the wire in a small area between cutting electrodes (e2) and the wheels d 'stretching (8),  Bc) the connection lasts until the wire breaks (1), leaving a lower wire and an upper wire,  Bd) the stretching wheels (8) separate and the drive elements of a lower head of the machine convey the lower thread,  Be) the stretching wheels (8) separate and the feed wheel (3) drives the upper thread which threads.