Laser machining apparatus

A laser machining apparatus comprises a first, a second and a third mirror for turning the direction of a laser beam, which are provided in between a machining head for irradiating a workpiece with the laser beam and a vertical Z-axis drive for moving the machining head in the vertical direction. The laser machining apparatus further comprises first drive means for varying the relative position between the first mirror, and the second and third mirrors by moving the relative position in the direction in which the laser beam proceeds from the first mirror to the second mirror, and second drive means for varying the relative position between the second and third mirrors by moving the relative position in the direction in which the laser beam proceeds from the second mirror to the third mirror.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a laser machining apparatus for cutting 
and holing a workpiece by means of a laser beam. 
2. Prior Art 
FIG. 9 is a block diagram illustrating a conventional laser machining 
apparatus introduced in a publication (Catalog of Carbon Dioxide Gas Laser 
Machining Apparatus, Mitsubishi Denki Kabushiki Kaisha). In FIG. 9, 
numeral reference 1 denotes a workpiece secured to a table 2 as what is to 
be processed; 3, a machining head for irradiating the workpiece 1 with a 
laser beam 4 in a direction substantially perpendicular to the workpiece 
1; 5, an X-axis drive mechanism for driving the table 2 in the horizontal 
X-axis direction; 6, a Y-axis drive mechanism for driving a Z-axis drive 
mechanism, which will be described later, in the horizontal Y-axis 
direction perpendicular to the horizontal X-axis direction; and 7, a 
Z-axis drive mechanism for driving the machining head 3 thus held in the 
Z-axis direction perpendicular to the surface of the workpiece 1, the 
Z-axis drive mechanism 7 being driven by the Y-axis drive mechanism 6 in 
the horizontal Y-axis direction. 
FIG. 10 illustrates the movement of the workpiece 1 and the laser beam 4. 
In FIG. 10, there are shown mirrors 33 and 34 for turning the direction in 
which the laser beam 4 has been emitted from a laser oscillator (not 
shown). 
The operation of the laser machining apparatus will subsequently be 
described. The workpiece 1 is set on the table 2 and moved by the 
horizontal X-axis drive mechanism in the X-axis direction as shown in FIG. 
9. As shown in FIG. 10, moreover, the mirror 34 and the machining head 3 
are moved by the Y-axis drive mechanism 6 to a desired position in the 
Y-axis direction, whereas the machining head 3 is moved by the vertical 
Z-axis drive mechanism 7 to a desired position in the Z-axis direction to 
vary the height. With the combination of these 3-axis drive mechanisms in 
operation, the relative position between the workpiece 1 and the machining 
head 3 is varied so that the workpiece 1 is processed by the laser beam 
irradiation 4 from the machining head 3. 
As the conventional laser machining apparatus is thus constructed, the 
heavy table 2 and the like need moving even when machining is carried out 
in conformity with a microminiature configuration. When it is attempted to 
increase or decrease the machining speed sharply, the drive mechanism 
tends to run short of drive force or cause vibration, thus deteriorating 
machining precision. For this reason, machining is compelled to be carried 
out at low speed without increasing or decreasing the machining speed 
sharply in order to secure machining precision; the problem is that 
machining efficiency becomes extremely low. 
SUMMARY OF THE INVENTION 
An object of the present invention made to solve the foregoing problems is 
to provide a laser machining apparatus capable of following microminiature 
configurations, curved lines of such as small diameter holes and the like 
with precision at high speed. 
A laser machining apparatus according to the present invention comprises a 
first, a second and a third mirror for turning the direction of a laser 
beam, these mirrors being provided between a machining head for 
irradiating a workpiece with the laser beam and a vertical Z-axis drive 
for moving the machining head in the vertical direction (a vertical Z-axis 
drive mechanism), a first drive means for varying the relative position 
between the first mirror, and the second and third mirrors by moving the 
second and third in the direction in which the laser beam proceeds from 
the first mirror to the second mirror, with the second and third mirrors 
as an integrated body, and a second drive means for varying the relative 
position between the second and third mirrors by moving the third mirror 
in the direction in which the laser beam proceeds from the second mirror 
to the third mirror. 
The laser machining apparatus according to the present invention is 
provided with the machining head which is movable in the horizontal 
two-axis directions perpendicular thereto with respect to the vertical 
Z-axis drive mechanism for holding and moving the machining head in the 
vertical Z-axis direction. As the machining head can be made light in 
weight and driven at quick variable speed, it becomes possible to process 
not only microminiature configurations but also small diameter holes with 
precision at high speed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An embodiment of the present invention will subsequently be described. FIG. 
1 is an explanatory diagram outlining a laser machining apparatus 
according to a first embodiment of the present invention, wherein like 
reference characters designate like or corresponding parts of the 
conventional laser machining apparatus shown in FIG. 10 with the omission 
of their repeated description. 
In FIG. 1, numerals 30, 31 and 32 denote mirrors, respectively. After being 
perpendicularly turned downward by a mirror 34, a laser beam on the move 
is horizontally turned by 90 degrees by the mirror 30, then horizontally 
turned by 90 degrees by the mirror 31 and further vertically turned by 90 
degrees by the mirror 32. The laser beam is thus introduced into a 
machining head 3. In this case, the mirror 30 is secured to a Z-axis drive 
mechanism 7 and the mirror 32 is secured to the machining head 3. 
Consequently, portions preceding the mirror 30 up to the machining head 3 
are synchronously moved by the Z-axis drive mechanism 7 in the Z-axis 
direction. 
FIG. 2 is a schematic diagram of a laser machining apparatus according to 
the first embodiment of the present invention, wherein like reference 
characters designate like or corresponding parts of the conventional laser 
machining apparatus shown in FIG. 9 with the omission of their repeated 
description. In FIG. 2, reference numeral 8 denotes a machining-head fine 
adjustment mechanism installed between the Z-axis drive mechanism 7 and 
the machining head 3. A first and a second drive means as well as the 
first, second and third mirrors 30, 31 and 32 are installed in the 
machining-head fine adjustment mechanism 8. The X-axis drive mechanism 5 
drives the table 2, to which the workpiece 1 is secured, in the horizontal 
X-axis direction. 
FIG. 3 is a detailed sectional elevational view of the machining-head fine 
adjustment mechanism shown in FIG. 2. In FIG. 3, reference numeral 9 
denotes a base plate secured to the Z-axis drive mechanism 7, 10 a first 
plate secured to the base plate 9, 11 a second plate movably provided in 
the horizontal Y-axis direction with respect to the first plate 10, 12 a 
third plate movably provided in the horizontal X-axis direction 
perpendicular to the horizontal Y-axis direction with respect to the 
second plate 11, 13 guides for movably coupling the second plate 11 to the 
first plate 10 in the horizontal Y-axis direction, 17 a table 
incorporating a ball screw movable in the horizontal X-axis direction, 18 
a servomotor for driving the table 17, 19 an encoder for detecting an 
angle of rotation of the servomotor 18, 15 a joint for coupling the third 
plate 12 and the table 17, 16 a cam follower, 25 a joint rail, 30 the 
mirror secured to the first plate 10, 31 the mirror secured to the second 
plate 11, 32 the mirror secured to the third plate 12, 20 a cover secured 
to the third plate 12, and 3 the machining head secured to the cover 20. 
FIG. 4 is a side view of the machining-head fine adjustment mechanism shown 
in FIG. 3, and FIG. 5 is a bottom view of the same. In FIGS. 4 and 5, 
numeral reference 14 denotes guides for movably coupling the third plate 
12 to the second plate 11 in the horizontal X-axis direction, 22 a table 
incorporating a ball screw movable in the horizontal Y-axis direction, 23 
a servomotor for driving the table 22, 24 an encoder for detecting an 
angle of rotation of the servomotor 23., and 21 a joint for coupling the 
second plate 11 and the table 22. 
The operation will subsequently be described. First, the way a laser beam 
proceeds will be described. While perpendicularly proceeding downward in 
the Z-axis drive mechanism 7, the laser beam passes through openings 9a, 
10a, 11a and 12a bored in the first to third plates 10, 11 and 12, and is 
then turned by the first mirror 30 in the horizontal Y-axis direction. 
Before being incident on the machining head 3, the laser beam is turned by 
90 degrees by the second mirror 31 in the horizontal X-axis direction and 
then perpendicularly turned downward by the third mirror 32. 
Subsequently, the movement of each mirror will be described. The first 
plate 10 is secured to the base plate 9 and as the first mirror 30 is also 
secured to the first plate 10, it is unmovable. The second plate 11 with 
the second mirror 31 secured thereto is movably coupled via the guides 13 
to the first plate 10 in the horizontal Y-axis direction. The table 22 is 
coupled via the joint 21 to the second plate 11 and moved by the 
servomotor 23 in the horizontal Y-axis direction. Consequently, the 
relative position between the first and second mirrors 30 and 31 can be 
varied in the horizontal Y-axis direction in which the laser beam 
proceeds. The variation of the relative position is detected by the 
encoder 24 fitted to the servomotor 23. 
The third plate 12 is coupled via the guides 14 to the second plate 11, the 
third plate being movable in the horizontal X-axis direction. Therefore, 
the third plate 12 is also moved in the Y-axis direction when the second 
plate 11 is moved in the horizontal Y-axis direction and the third mirror 
32 secured to the third plate 12 is moved likewise accordingly. 
With the third plate 12, the joint 15, the cam follower 16 and the joint 
rail 25, the table 17 is movably coupled in the horizontal Y-axis 
direction. When the second plate 11 moves in the horizontal Y-axis 
direction, the joint portion prevents the movement in the horizontal 
Y-axis direction from being transmitted to the table 17, which is moved by 
the servomotor 18 in the horizontal X-axis direction. 
As a result, the relative position between the second and third mirror 31 
and 32 can be varied in the horizontal X-axis direction in which the laser 
beam proceeds. The variation of the relative position is detected by the 
encoder 19 fitted to the servomotor 18. As the machining head 3 is secured 
via the cover 20 to the third plate 12, the relative position between the 
third mirror 32 and the machining head 3 remains invariable and locked. 
As shown in FIG. 5, the openings 11a and 12a are provided in the second and 
third plates 11 and 12 so that the second plate 11 is inhibited from 
interfering with the first mirror 30 when the second plate is moved in the 
horizontal Y-axis direction. Moreover, the opening 12a in the third plate 
12 is made larger than the opening 11a in the second plate 11 so that the 
third plate 12 is inhibited from interfering with the second mirror 31 
when the third plate is moved in the horizontal X-axis direction. When the 
Z-axis drive mechanism 7 moves up and down, every part including the 
machining head 3 is caused to move up and down. 
A description has been given of the laser machining apparatus according to 
the first embodiment of the present invention, in which the workpiece 1 is 
moved in the horizontal X-axis direction. The same type of operation is 
also anticipated in a laser machining apparatus according to a second 
embodiment of the present invention, in which the workpiece 1 is moved in 
both horizontal X- and Y-axis directions as shown in FIG. 6. In this case, 
the laser beam 4 proceeding out of the oscillator is perpendicularly 
turned downward by a mirror 35. 
Although a description has been given of the laser machining apparatus 
according to the second embodiment in which the workpiece 1 is moved in 
both horizontal X- and Y-axis directions, the same type of operation is 
also anticipated in a laser machining apparatus according to a third 
embodiment of the present invention, in which the workpiece 1 is not 
moved, whereas the parts covering the mirror 33 up to the machining head 3 
are moved in the horizontal X-axis direction, as shown in FIG. 7. Although 
the plates and the table have been arranged in series in the horizontal X- 
and Y-axis directions respectively in the first embodiment, the same type 
of operation is further anticipated in a laser machining apparatus 
according to a fourth embodiment of the present invention, in which the 
plates and the table are disposed in parallel with the joint used to 
couple them as shown in FIG. 8. As shown in FIG. 8, the total length of 
the apparatus can further be shortened. 
The same type of operation is still anticipated with the use of linear 
motors instead of using the tables 17 and 22 incorporating ball screws and 
the servomotors 18 and 23 in the first embodiment as drive means for 
varying the relative positions among the mirrors 30, 31 and 32. This is a 
fifth embodiment of the present invention. 
The encoders 19 and 24 fitted to the servomotors have been used to detect 
the relative positions in the first embodiment. However, as a sixth 
embodiment of the present invention, a linear scale may be installed 
between the first and second plates 10 and 11 to detect the relative 
position therebetween in the horizontal Y-axis direction, whereas a linear 
scale may be installed between the second and third plates 11 and 12 to 
detect the relative position therebetween in the horizontal X-axis 
direction. The relative position can thus be detected accurately without 
bothering to eliminate backlash that may develop in the ball bearing and 
the joint. 
As set forth above, the provision of the machining-head fine adjustment 
mechanism having the plurality of mirrors for turning the laser beam 
between the machining head for irradiating the workpiece with the laser 
beam and the Z-axis drive mechanism for driving the machining head in the 
vertical Z-axis direction according to the present invention has the 
effect of processing any workpiece precisely with a small drive force at 
high speed without causing vibration by operating the machining-head fine 
adjustment mechanism for following microminiature configurations, and 
curved lines such as small diameter holes and the like.