Electric heating – Metal heating – By arc
Reexamination Certificate
2001-12-19
2003-10-21
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121700
Reexamination Certificate
active
06635849
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a laser beam machine, and relates in particular to a laser beam machine used, for example, for high-speed micro-hole machining.
BACKGROUND ART
A common, conventional laser beam machine for micro-hole machining is shown in FIG.
11
. The machine in
FIG. 11
, as provided, emits a pulse laser beam
2
to impinge on object
1
that is horizontally arranged on an XII table
14
, and comprises: a laser oscillator
3
, for generating the pulse laser beam
2
; several bend mirrors
4
, for reflecting the laser beam
2
and guiding the beam
2
along a light path; galvano mirrors
5
(two galvano mirrors
5
a
and
5
b
in FIG.
11
), for reflecting the laser beam
2
at an arbitrary angle as instructed by a controller
10
; a galvano scanner
6
, for driving the galvano mirrors
5
; an f&thgr; lens
7
, for correcting the angle of the laser beam
2
received from the galvano mirrors
5
so it is be parallel to the axial direction of the light path, and for guiding the laser beam
2
so it is perpendicular to the object
1
; a CCD camera
8
, used for the display of the results obtained; a Z axis table
9
, on which the galvano scanner
6
, the f&thgr; lens
7
and the CCD camera
8
are mounted and which is moved in direction Z in order to adjust the distance from the object
1
; and the controller
10
, for controlling this driving system. Compared with the laser beam machining of sheet metal performed at a rate of 500 holes per second, the laser beam machine provides higher speed machining by using the galvano scanner
6
, which quickly positions the laser beam
2
perpendicular to the object
1
, the galvano mirrors
5
, the f&thgr; lens
7
and the pulse laser oscillator
3
, which oscillates a laser beam for an extremely short period of time.
An explanation will now be given for the micro-hole machining performed using this machine. The pulse laser beam
2
, which is output by the laser oscillator
3
in accordance with a frequency and an output value that are set by the controller
10
, is guided by the several bend mirrors
4
to the galvano mirrors
5
a
and
5
b
, which are attached to the galvano scanner
6
. Then, the laser beam
2
is reflected by the galvano mirrors
5
a
and
5
b
, which are secured at arbitrary angles by the galvano scanner
6
, and transmitted to the f&thgr; lens
7
. The laser beam
2
, incident to the f&thgr; lens
7
, is focused on the object
1
. Since the laser beam
2
traverses various incident angles immediately before entering the f&thgr; lens
7
, at the f&thgr; lens
7
the angular direction of the laser beam Z is corrected so that it is perpendicular to the object
1
.
The controller
10
, to control the machining for a shape that is input to it in advance, adjusts the timing whereat the laser beam
2
is output by the laser oscillator
3
, and the angles of the galvano mirrors
5
a
and
5
b
. During the machining, normally, a hole is produced each time the laser pulse irradiates the object
1
; however, if the strength of the laser beam
2
is inadequate for the material of which the object
1
is composed, to open a deep hole a method is employed whereby several pulses are emitted for each irradiated point. Further, since the galvano mirrors
5
a
and
5
b
that are used can provide only a limited scanning range for the laser beam
2
, when the machining of a portion of a predetermined shape is completed, the object
1
is moved to a succeeding scan area by shifting the XY table
14
, and the galvano scanner
6
is again driven to continue the machining of the shape. This procedure is used to guide the laser beam
2
to arbitrary locations to perform micro-hole machining.
To improve the above described processing, three methods can be used to perform higher speed machining: a method used for an individual machine to improve unit hour productivity by increasing the galvano scanner driving speed; a method used for the generation by the pulse laser oscillator of a higher power laser beam at a higher oscillation frequency; and a method used to increase the speed at which the XY table is moved.
As a consequence of the recent dramatic growth of the micro-hole machining market, requested machining speeds have been increased by several to several tens of times within a short period. Therefore, it is anticipated that a galvano scanner that can be driven at high speed and a laser oscillator that can generate a high power pulse laser beam will be developed shortly, and that there is an urgent necessity for the development without delay of a technique for drastically improving machining speed and for applying it for the manufacture of products. However, while taking into account the present situation wherein the capabilities of the XY table have neared their limits, it is very difficult to devise a method for increasing the positioning speed of a laser beam machine that can reduce the machining time to ⅕, {fraction (1/10)} or less that which is presently available, as is requested by the market.
Further, were a method devised whereby multiple machine heads were prepared for one oscillator and a laser beam emitted by the oscillator would be branched at several steps by using translucent mirrors, a huge light path system would have to be designed and light path adjustments would become complicated.
A diffractive optical element (hereinafter referred to as a DOE, as needed) is an optical element that can subdivide into a designated number of beams or patterns, a beam that is received from a diffractive grid provided on a surface. While generally only one portion can be machined by one oscillation of a laser beam, a DOE that is designed to subdivide a laser beam to obtain, for example, three beams, need only be inserted into the above described laser beam machine to perform micro-hole machining for three portions that could be processed at the same time using the one oscillation. A DOE is also called a holographic optical element (HOE).
A DOE that subdivides a laser beam to obtain a desired number of beams and patterns can be designed, and can be used to increase the machining speed comparatively easily. In this fashion, the above problem presented by the need to increase the machining speed can be resolved.
However, when a DOE is inserted into a light path system, depending on the insertion location, the design specifications can not be demonstrated. In such a case, for example, a mask must be employed for an image transfer optical system in order for the power of a laser beam to be efficiently employed. However, when the DOE is inserted in front of the mask, the mask adversely affects the spectral pattern. And when, for example, the DOE is inserted immediately behind the galvano mirror and immediately in front of the f&thgr; lens, the laser beam will enter the DOE obliquely, and the spectral pattern will be affected by a change in the refractive index. Thus, a complicated DOE design and a complicated galvano scanner control means are required when the incident angle and the incident area are taken into account. And were a DOE inserted, for example, immediately behind an f&thgr; lens, the DOE would have to be large enough to adequately cover the scan area provided by a galvano mirror, and the manufacturing costs would be enormous. In addition, means for protecting the surface of a DOE surface from dust and the sputter that is generated during machining would be required, increasing the manufacturing costs even further.
For a laser beam that passes through a galvano mirror and an f&thgr; lens, an instructed value does not match a machining position due to differences in the distance between the galvano mirror and the f&thgr; lens. Thus, to correct this shift, a position correction must be provided by a program. Further, since the reflection angle of a galvano mirror is changed slightly by the ambient temperature, it is preferable that a machine be used in an air conditioned room. For if the location whereat the laser beam machine is used is not air conditioned, or if the air conditioning is turne
Iwai Yasuhiko
Kurosawa Miki
Mizuno Masanori
Okawa Tatsuki
Evans Geoffrey S.
Mitsubishi Denki & Kabushiki Kaisha
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