Laser machining apparatus

Details Laser machining apparatus Laser machining apparatus

2001-11-30

2003-12-16

Shaw, Clifford C. (Department: 1725)

Electric heating

Metal heating

By arc

C219S121630

Reexamination Certificate

active

06664507

ABSTRACT:

TECHNICAL FIELD
This invention relates to a laser beam machining apparatus.
BACKGROUND ART
Among welding techniques for joining metals together are laser beam welding and arc welding. Laser beam welding is performed using a CO
2
laser oscillator or a YAG laser oscillator. CO
2
laser light has to be mirror transmitted, and thus its adjustment is laborious, while YAG laser light can be transmitted by an optical fiber. Under these circumstances, expectations are rising for laser beam welding using a YAG laser oscillator. Arc welding comes in types, including gas shielded consumable electrode arc welding (GMA welding) such as MIG welding, and gas shielded non-consumable electrode arc welding such as TIG welding.
Laser light is concentrated by an optical instrument to give a high energy density. Laser beam welding with such laser light achieves deep weld penetration in a narrow range of melting. With arc welding such as GMA welding (MIG welding, etc.) or TIG welding, on the other hand, the arc spreads in a relatively broad range, thus performing welding of a wide bead range, and enabling welding with a high groove tolerance.
In recent years, methods for simultaneously performing laser beam welding and arc welding have been studied in attempts to carry out welding with a wide welding range and a deep weld penetration.
A laser beam machining head, which performs laser welding and arc welding simultaneously, has a configuration, for example, disclosed in Japanese Unexamined Patent Publication No. 1998-216972. As shown in
FIG. 14
, this laser beam machining head performs laser beam welding and arc welding by applying laser light
103
from a laser beam welding head
102
to a portion
101
a
, to be welded, of a base metal
101
, and simultaneously applying an arc discharge from an electrode
105
of a GMA welding head
104
, while jetting a shielding gas at the portion
101
a
from a gas jet nozzle
106
.
However, this laser beam machining head is large in size as a whole, since the laser beam welding head
102
and the GMA welding head
104
are independent in the laser beam machining head. Moreover, it is tiresome to keep the relative positional relationship between the laser beam welding head
102
and the GMA welding head
104
always constant in response to a change in the welding position or the welding posture. Thus, the laser beam machining head is not suitable, particularly, for three-dimensional machining by a robot.
The inventors of the present invention proposed in Japanese Unexamined Patent Publication No. 1999-156573 a laser beam machining head capable of solving the above-described problems. In this laser beam machining head, as shown in
FIG. 15
, laser light
112
transmitted by an optical fiber
111
is reflected by a convex roof mirror
113
and a concave roof mirror
114
, and divided thereby into two divisional beams, a first divisional laser beam
112
a
and a second divisional laser beam
112
b
, with a space portion
117
being formed therebetween. These divisional laser beams
112
a
and
112
b
are focused by a focusing lens array
115
onto a portion to be welded.
The concave roof mirror
114
and the focusing lens array
115
are perforated, at the center thereof, with through-holes
114
a
and
115
a
, respectively. An electrode holding pipe
116
for holding an arc electrode, such as a TIG electrode or a GMA electrode, is inserted through the through-holes
114
a
,
115
a
, whereby the arc electrode held by the electrode holding pipe
116
is located in the space portion
117
between the divisional laser beams
112
a
and
112
b
and rendered coaxial with these laser beams.
When laser beam welding and arc welding are performed simultaneously, irradiation with laser light evaporates a metal (base metal) to ionize the metal partially (into Fe ions, Cr ions, Ni ions, etc.), and an arc discharge is induced thereby. Thus, the arc can be stabilized, so that a marked improvement in welding performance can be achieved.
To stabilize the arc reliably with laser light, however, it is necessary to control, without fail, the timing of oscillating (projecting) laser light and the timing of performing arc discharge. However, no proposal has been made for an apparatus for such control.
To carry out laser beam welding and arc welding at the same time, it is desirable to use a coaxial laser beam machining head. With the above-mentioned conventional coaxial laser beam machining head, the through-holes
114
a
and
115
b
are provided in the concave roof mirror
114
and the focusing lens array
115
. Processing of these members takes much time and effort, and the through-hole portions are easily damaged. Furthermore, the convex roof mirror
113
and the concave roof mirror
114
are used to divide the laser light
112
into two beams, but these concave and convex roof mirrors
113
and
114
are very expensive.
Accordingly, the present invention has been accomplished to solve the above problems, and its challenge is to provide a laser beam machining apparatus capable of reliably stabilizing an arc when performing laser beam welding and arc welding at the same time, and having a coaxial laser beam machining head which is small in size, free from the risk of damage to optical equipment, and inexpensive.
DISCLOSURE OF THE INVENTION
A laser beam machining apparatus, as a first invention for solving the above challenge, is a laser beam machining apparatus adapted to perform, simultaneously, laser beam welding for welding a portion, to be welded, by transmitting and condensing laser light oscillated by a laser oscillator, and applying the laser light to the portion to be welded, and arc welding or filler wire welding for welding the portion, to be welded, by an arc discharge from an arc electrode, characterized by including
control means for exercising control such that the arc discharge from the arc electrode is performed after or simultaneously with start of oscillation of the laser light from the laser oscillator, and an output of the laser light from the laser oscillator is stopped after or simultaneously with termination of the arc discharge from the arc electrode.
According to the laser beam machining apparatus of the first invention, therefore, arc discharge can be reliably induced by laser light, and the arc can be stabilized thereby, from the start to the end of welding.
A laser beam machining apparatus of a second invention is the laser beam machining apparatus of the first invention, characterized by including
a coaxial laser beam machining head comprising the arc electrode disposed coaxially with the laser light.
According to the laser beam machining apparatus of the second invention, therefore, the laser light and the arc electrode are coaxial. Thus, the relative position of the laser light and the arc electrode is stable, and the induction of arc discharge by laser light can be performed easily.
A laser beam machining apparatus of a third invention is the laser beam machining apparatus of the second invention, characterized in that
the coaxial laser beam machining head comprises:
one collimating optical system for making the laser light into a parallel beam;
a first reflecting mirror for reflecting part of the laser light made into the parallel beam by the collimating optical system to divide the laser light into a first divisional laser beam and a second divisional laser beam;
a second reflecting mirror for further reflecting the first divisional laser beam reflected by the first reflecting mirror to form a space portion between the first divisional laser beam and the second divisional laser beam;
one focusing optical system for focusing the first divisional laser beam and the second divisional laser beam onto a portion to be machined; and
an arc electrode disposed in the space portion between the first divisional laser beam and the second divisional laser beam coaxially with the laser beams.
According to the laser beam machining apparatus of the third invention, therefore, the laser beam machining head is very small in size, inexpensive, and free from the risk

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