JPH03155B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to a laser processing machine that processes a workpiece by condensing laser light emitted from a laser oscillator with a condensing lens and irradiating it from the nozzle tip. The present invention relates to a nozzle equipped with an electrode for detecting the distance between a workpiece and a workpiece using electromagnetic capacitance such as eddy current, magnetism, and capacitance.

2. Description of the Related Art In general, in this type of laser processing machine, in order to maintain processing accuracy, it is necessary to keep the focus position of the workpiece and the laser beam constant.

For this reason, conventionally, for example, Japanese Patent Application Laid-Open No. 57-44487
As in the publication, a capacitive sensor using a ring-shaped electrode attached to the tip of the nozzle, or
As in Publication No. 59-54487, a capacitance sensor with a separate electrode embedded in the tip of the nozzle detects the capacitance with the surface of the work W without contact, and a servo mechanism detects the capacitance. The workpiece W is controlled by controlling the nozzle height so that the output of the capacitance sensor is constant.
The distance between the nozzle and the nozzle has been kept constant. According to this method, the distance between the nozzle and the workpiece W can be detected in a non-contact manner, and is an extremely effective means for processing flat workpieces.

However, when the surface of the workpiece W has a complex three-dimensional shape with unevenness, the nozzle equipped with the ring-shaped sensor has the disadvantage that it cannot enter into the narrow valleys of the workpiece W, resulting in parts that cannot be machined. Ta.

On the other hand, in the case of a nozzle equipped with a separate sensor at the nozzle tip, although the nozzle may be able to enter the valley of the workpiece W in terms of shape as shown in FIG. 8, when the nozzle approaches the wall of the workpiece W, The amount of capacitance change in _the capacitance _C This is added to the capacitance C _L between the end face of the electrode A and the workpiece W.
For this reason, a capacitance larger than the original capacitance C _L is detected, and as a result, the nozzle height is controlled to a position that is deviated from the set height, making it impossible to perform laser processing or resulting in poor processing quality. There was a problem with variations.

In other words, the _{capacitances C} The height could not be kept constant, making it difficult to maintain optimal processing conditions.

OBJECTS OF THE INVENTION AND SOLUTIONS THEREOF The object of the present invention is to always keep the electromagnetic capacitance detected from the side surface of the nozzle constant, so that even when machining a workpiece with a complex three-dimensional shape with an uneven surface, the electromagnetic capacitance detected from the nozzle tip surface By controlling the nozzle height so that the electromagnetic capacitance is always constant, it is possible to detect accurate changes in electromagnetic capacitance between the
The point is that the laser beam can always be focused at a fixed position from the workpiece surface.

Therefore, the present invention uses the tip of the nozzle itself as the first electrode, covers the side surface of the nozzle except for the tip with a second electrode via an insulating section, and electromagnetically connects the side surface of the first electrode and the workpiece. It was blocked off.

Configuration of the Invention Hereinafter, the configuration of the present invention will be explained based on specific embodiments shown in FIGS. 1 to 4.

Reference numeral 1 denotes a lens holder which is attached to a head body (not shown) of a laser processing machine so as to be movable and adjustable in the optical axis direction, and holds a condenser lens 2 inside.

Reference numeral 3 denotes a hollow cylindrical nozzle holder made of an insulating material, and is fixed to the lens holder 1 with screws 4 at its upper end flange portion 3a. Further, a connector attachment hole 5 is formed in one side of the nozzle holder 3, and a connector 7 for a coaxial cable 6, which will be described later, is attached thereto.

Further, a protruding small-diameter portion 3b with a reduced inner diameter is provided on the lower inner peripheral portion of the nozzle holder 3, and a nozzle fitting portion 3c is formed below the small-diameter portion 3b. A metal collar 8 made of copper, for example, is attached to the nozzle fitting portion 3c by adhesive or the like. The nozzle 9 is fixed to the nozzle holder 3 by bringing the upper end surface of the nozzle 9 into contact with this metal collar 8 and further tightening the nozzle nut 10 from below.

This nozzle nut 10 is made of a conductive material such as aluminum, and is screwed into a threaded portion 3d formed on the outer periphery of the lower part of the nozzle holder 3. Further, a tapered nozzle holding surface 10a is formed on the inner periphery of the nozzle insertion hole at the bottom of the nozzle nut 10, and a tapered engagement between this holding surface 10a and a tapered flange portion 9a formed on the outer periphery of the upper end of the nozzle 9. The nozzle 9 is firmly fastened to the nozzle holder 3 by fitting.

The nozzle 9 has an inverted hollow conical shape, and has an injection hole 9b formed at the center of its tip, that is, its lower end, through which the laser beam, assist gas, etc. pass.

This nozzle 9 connects, from the inside, a first electrode D for detecting electromagnetic capacitance (in this case, capacitance) with the workpiece W, an insulating part E, and a space between the side surface of the first electrode D and the workpiece W. It has a three-layer structure in the order of the second electrode F for electromagnetically (here, electrostatically) shielding.

The nozzle 9 is formed by coating a nozzle base 11 made of, for example, ceramic with metal films 12, 13 of, for example, copper or nickel. That is, the nozzle base 11 itself is the insulating part E, and the first electrode D made of the metal coating is provided continuously from the inner circumferential side surface (including the inner circumference of the injection hole 9b) to the tip surface. The second electrode F made of the metal coating 13 is provided on the outer peripheral side surface of the nozzle base 11 so as to be separated from the first electrode D and cover the outside of the side surface of the first electrode D.

In this case, by forming the first electrode D and the second electrode F with a metal coating made of the same material, they can be easily welded to the nozzle base 11 by plating or the like.

That is, a part of the upper outer peripheral surface of the nozzle base 11 is masked, and the entire nozzle base 11 is covered with a plating bath. At that time, as the tip of the nozzle 9 has continuous plating as shown in Fig. 2, the second
By chamfering the corners of the outer periphery as shown by the two-dot chain line in the figure, the plating between the tip end surface and the outer circumferential side surface is completely separated as shown in FIG. Therefore, the first electrode D and the second electrode F are electrically insulated via the nozzle base 11 serving as the insulating portion E.

In FIG. 1, the connector 7 is made of a conductive material, and a first electric wire 6a, which is the core wire of the coaxial cable 6, is inserted through the center thereof while being covered with vinyl, and a second electric wire 6b on the outer surface of the connector 7 is inserted into the center of the connector 7. It is connected to by soldering. The first electric wire 6a
is connected by soldering from the connector 7 through the inside of the nozzle holder 3 to the metal collar 8 which is electrically connected to the first electrode D of the nozzle 9.
The electric wire 6a is guided along the coaxial cable 6 to, for example, a capacitance detector 14 as an electromagnetic capacitance detector provided outside. This capacitance detector 14 is connected to a motor drive control device 15 consisting of a C/V converter, an amplifier, etc., and is connected to a servo motor for cap control based on the capacitance value detected from the first electrode D. 16, the lens holder 1, which integrally holds the nozzle 9, is moved and adjusted in the optical axis direction relative to the head body.

The outer peripheral surface of the nozzle holder 3 is also coated with a metal coating 18 made of copper or nickel, for example, and the connector 7 is connected via the metal nut 17 screwed onto the connector 7 and the metal coating 18. , is electrically connected to the nozzle nut 10 which is electrically connected to the second electrode F of the nozzle 9. The second electric wire 6b electrically connected to the connector 7 is connected along the coaxial cable 6 to, for example, a ground terminal on the laser processing machine main body side, and the second electric wire 6b is connected to the second electrode F.
is set at the same potential as the workpiece W.

Further, 19 is an insulating tube that protects the joint between the connector 7 and the coaxial cable 6, and 20 is an insulating tube that covers the end surface of the connector 7 and also covers the nozzle holder 3.
This is an elastic cap for attaching a connector to.

Effect of the Invention First, to explain how to attach the nozzle 9 to the nozzle holder 3, the upper end of the nozzle 9 is fitted into the nozzle fitting part 3C on the nozzle holder 3 to which the connector 7, metal nut 17 and metal collar 8 are attached in advance. Further, the nozzle nut 10 inserted into the nozzle 9 is screwed onto the threaded portion 3d of the nozzle holder 3. By tightening the nozzle nut 10 in this state, the centering of the nozzle 9 is corrected and its upper end surface is pressed against the metal collar 8 due to the wedge action between the tapered holding surface 10a and the tapered flange portion 9a of the nozzle 9. , nozzle holder 3
It is tightened and fixed.

Next, so-called gap control, which is an adjustment to keep the distance between the workpiece W and the tip of the nozzle 9 constant during processing, will be explained.

As shown in FIG. 1, the second electrode F of the nozzle 9 is connected to the workpiece W by being grounded from the tapered flange 9a through the nozzle nut 10, the metal coating 18 of the nozzle holder 3, the metal nut 17, the connector 7, and the second electric wire 6b. They are at the same potential. On the other hand, the first electric wire D is connected from the upper end surface of the nozzle 9 to the metal collar 8 and the first electric wire 6a.
It is connected to the capacitance detector 14 via.

When the capacitance detector 14 detects the capacitances C L and C A between the workpiece W and the second electrode F at the tip and circumferential surfaces of the first electrode D, the sum of these capacitances C _L and C _A is detected. The capacitance C _L +C _A is sent to the motor drive control device 15 as a signal corresponding to the distance between the tip of the nozzle 9 and the workpiece W, that is, the gap amount. The motor drive control device 15 drives and controls the servo motor 16 so as to keep the gap amount between the tip of the nozzle 9 and the workpiece W constant, and moves the lens holder 1, which holds the nozzle 9 integrally, in the optical axis direction with respect to the head body. Adjust movement.

As shown in FIG. 4, when the surface of the workpiece W has a three-dimensional shape, even if the nozzle 9 approaches the wall, the second electrode F is at the same potential as the workpiece W and the first electrode F is at the same potential as the workpiece W.
Since the circumferential side of the electrode D and the work W are completely shielded electrostatically, the side of the nozzle is close to the work W.
Despite being close to the wall, the capacitance C _A due to the peripheral side of the first electrode D is detected between it and the second electrode F, which is fixed to the nozzle 9, and is therefore always constant. Since a detected value is obtained, it does not affect the change in capacitance C _L that should be detected, and the capacitance detector 14 can obtain an accurate detected value corresponding to the gap amount.

Note that since the first electrode D is a very thin film, almost no capacitance is detected from the thickness of the first electrode D on the tip surface of the nozzle 9 to the sides, and it does not affect the gap amount at all. .

Modification Next, a modification of the present invention will be described based on FIGS. 5 and 6.

Components that are the same as those in FIG. 1 are designated by the same reference numerals and their explanations will be omitted.

As shown in FIGS. 5 and 6, this nozzle 9' has a nozzle base 11' formed of a conductive material such as copper or nickel as the first electrode D, and the outer periphery of the first electrode D. The insulating portion E is formed by coating the side surface with an insulating coating 21 formed by thermally spraying ceramic, for example, and
Further, the second electrode F is formed by coating its outer surface with a metal coating 22 formed by thermal spraying, for example, copper or nickel.
In this case, coating is not applied to the outer periphery and lower end surface of the upper end of the nozzle base 11', and as shown in FIG. is insulated.

When this nozzle 9' is attached to the nozzle holder 3 in the same manner as described above, the first electrode D has its upper end surface in contact with the metal collar 8 as shown in FIG. 5, and the capacitance is detected via the first electric wire 6a. connected to the device 14,
The second electrode F is grounded from the nozzle nut 10 through the metal coating 18 surface of the nozzle holder 3, the metal nut 17, the connector 7 and the second electric wire 6b.

Therefore, during machining, since the capacitance between the first electrode D and the second electrode F is always constant as in the previous embodiment, the capacitance changes between the lower end surface, that is, the tip of the nozzle 9', and the workpiece W. is detected as a change in gap amount. Therefore, accurate gap control can be performed even on a three-dimensional workpiece W.

Note that the nozzle 9' is not limited to the one in which the second electrode F is formed of the metal coating 22 by metal spraying as described above, and as shown in FIG. A metal cap 23 having the same shape as the first electrode D is formed on the nozzle base 11', and an insulating coating 2 as an insulating part E is formed on the nozzle base 11' as the first electrode D.
It can also be formed by fitting the metal cap 23 as the second electrode F onto the electrode 1 by thermal spraying.

In this case, since slippage is possible at the joint between the insulating part E and the second electrode F, the material of the insulating part E, such as ceramic, and the material of the second electrode F, such as copper, deform with different coefficients of thermal expansion. Also, there is no interference between the two, and peeling and cracking of the ceramic can be prevented. Furthermore, the insulation resistance value is more constant than when the second electrode is formed by metal spraying, and the quality is more stable. Furthermore, even if the outer surface of the nozzle 9' is damaged, the nozzle 9' can be removed by simply replacing the metal cap 23.
can be easily repaired.

Effects of the Invention As explained above, the nozzle is formed in three layers in the order of the first electrode for electromagnetic capacitance detection, the insulating part, and the second electrode from the inside, and the tip surface of the nozzle is Since the circumferential side surface except for the workpiece is electromagnetically shielded from the workpiece by the second electrode, the electromagnetic capacitance detected at the side surface portion of the first electrode is always constant. It is possible to accurately detect changes in electromagnetic capacitance between the nozzle tip and the workpiece when processing a workpiece. Therefore, by controlling the nozzle height so that this electromagnetic capacitance is always constant, the focus of the laser beam can be adjusted. It can always be tied to the surface of the workpiece, so optimal machining conditions can be maintained at all times, improving machining accuracy.

Further, the nozzle body is made of ceramic as the insulating part, the first electrode is formed with a metal coating on the inner circumferential side and the tip side of the nozzle body, and a second metal coating is formed on the outer circumferential side of the nozzle body. If the second electrode is formed, the nozzle will be extremely lightweight due to the nature of ceramic, and each electrode can be easily coated by plating without being embedded, thereby greatly improving productivity.

Furthermore, since the first electrode on the nozzle tip surface is a very thin film, there is almost no electromagnetic capacitance detected from the thick part, and the gap amount between the nozzle and the workpiece can always be accurately detected. Furthermore, since the inner surface of the nozzle is covered with a metal coating, it has very good light reflection and thermal conductivity, and can completely protect the nozzle from laser light.

Further, the nozzle body is formed as the first electrode, the insulating part is formed with an insulating coating made of ceramic, for example, on the outer circumferential surface of the nozzle body, and the second electrode is further formed with a metal coating on the outer circumferential surface of the nozzle body. For example, since the inner surface of the nozzle is made of metal such as copper material, it has a high light reflectance, and has good thermal conductivity, so that heat is not easily trapped in one part and there is little thermal deformation of the nozzle due to laser light. Furthermore, by simply manufacturing the nozzle base from a copper material, for example, and overlaying the above-mentioned insulating coating and metal coating on it by thermal spraying, an electromagnetic shielding wall can be easily formed on the side of the nozzle, resulting in extremely high productivity. .

Furthermore, the second electrode is a metal cap, and the first electrode is thermally sprayed with an insulating coating, and the metal cap is fitted to the first electrode to form the three-layer structure nozzle. Even if the two are deformed with different coefficients of thermal expansion, it is possible to slide at the joint between the two, so there is no interference between the two, and it is possible to prevent the insulation coating from peeling off or cracking. Furthermore, the insulation resistance value is more constant than when the second electrode is formed by metal spraying, and the quality is more stable.
Furthermore, even if a scratch or the like occurs on the outer surface of the nozzle, the nozzle can be repaired very easily by simply replacing the metal cap. .

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the nozzle of the present invention attached to a nozzle holder, and FIG. 2 is an enlarged sectional view showing the tip of the nozzle when plated with metal.
Figure 3 is an enlarged sectional view showing the nozzle tip after chamfering from the state shown in Figure 2, Figure 4 is a diagram to explain the capacitance between the workpiece and the nozzle during the same processing, and Figure 5 is , FIG. 6 is an enlarged sectional view of the tip of the same nozzle, FIG. 7 is an exploded sectional view of the nozzle showing another modification, and FIG. 8 is a cross-sectional view of a conventional nozzle. A sectional view shown. 9, 9'... Nozzle, 12... Metal coating, 13... Metal coating, 14... Capacitance detector as electromagnetic capacitance detector, 21... Insulating coating, 22... Metal coating, 2
3...Metal cap, D...First electrode, E...Insulating part,
F...Second electrode, W...Work.

Claims (1)

[Claims] 1. A laser processing machine that detects the electromagnetic capacitance between the nozzle tip and the workpiece to adjust the movement of the nozzle so that the distance between the two is always kept constant, A first electrode connected to the electromagnetic capacitance detector and provided continuously from the inner circumferential side of the nozzle to the nozzle tip face for detecting the electromagnetic capacitance between the workpiece and the outside of the side surface of the first electrode. a second electrode provided to cover the workpiece and electromagnetically shielding between the side surface of the first electrode and the workpiece;
A nozzle for a laser processing machine, characterized in that the nozzle is formed in three layers, including an insulating part interposed between an electrode and a second electrode for electromagnetically insulating the two electrodes. 2. Claim 1, wherein the first electrode and the second electrode are each made of a metal coating.
The nozzle of the laser processing machine described in section. 3. The nozzle for a laser processing machine according to claim 1, wherein the insulating part is made of an insulating film, and the second electrode is made of a metal film. 4. The nozzle for a laser processing machine according to claim 1, wherein the insulating part is made of an insulating film, and the second electrode is made of a metal cap. 5. A nozzle for a laser processing machine according to any one of claims 1 to 4, wherein the insulating portion is made of ceramic.