Electric heating – Metal heating – By arc
Reexamination Certificate
1999-05-17
2001-03-20
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
By arc
C372S038060
Reexamination Certificate
active
06204470
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber transmission-type laser processing apparatus.
2. Description of the Related Arts
In case of performing a laser processing at a site remote from the body using a laser processing apparatus such as a YAG laser, an input unit within the apparatus body is linked via an optical fiber with an output unit at remote site (processing site). A laser beam generated in the apparatus body is transmitted from the input unit through the optical fiber to the output unit, where the laser beam is projected onto a workpiece.
Recently prevailing is a multi-position processing in which a laser beam oscillated within the apparatus body is branched into a plurality of laser beams, which are then directed via optical fibers toward different positions.
A laser processing apparatus generating a pulsed laser beam to perform the laser processing has hitherto used a technique for variably controlling waveforms of a laser output of the pulsed laser beam or of predetermined electric parameters corresponding thereto, so as to be adaptable to a diversity of processing demands.
According to such a waveform control system, a desired reference waveform for waveform control is previously set and entered into the laser processing apparatus. In the laser processing apparatus, a laser oscillation unit is supplied with a power from a laser power supply unit to oscillatorily output a laser beam, and a laser control part controls the laser power supply unit with an open loop control system or a closed loop (feedback) control system so as to allow waveforms, that is, variations with time of the laser output of the laser beam oscillatorily output from the laser oscillation unit or of predetermined electric parameters of the laser power supply unit to conform to that reference waveform.
In case of the laser processing using the pulsed laser beam, typically a series of pulsed laser beams are irradiated to the workpiece at a preset repetition frequency.
In the optical fiber transmission-type laser processing apparatus as described above, the laser beam must impinge correctly on one end surface of the optical fiber (in other words, it must be concentrated onto the central portion of the end surface) in the input unit of the apparatus body. Inaccurate incidence of the laser beam on the optical fiber results in a greater loss of laser output or in burning of the end surface of the optical fiber. Thus, in the input unit, upon the assembling or setting of the apparatus or upon the exchange of the optical fibers, the position of a condenser lens is adjusted (focused) in the optical axis direction (Z direction) while simultaneously the attachment position of the optical fiber is adjusted (optical axis aligned) in the direction (XY direction) orthogonal to the optical axis direction.
In this type of laser processing apparatus, however, if the laser output exceeds a certain value, the thermal lens effect or the like of the laser medium (YAG rod) may possibly cause as shown in
FIG. 22
an enlarged beam diameter or output angle as indicated by a dotted line LB′ of the laser beam LB oscillated from the laser oscillation unit
200
, with the result that the laser beam overfill the incidence end surface of the optical fiber
204
even though it is condensed by the condenser lens
202
in the input unit, consequently bringing about a possible burning of the optical fiber
204
or defective processing. The limit value of the laser output causing such a deficiency depends on the type and diameter of the optical fiber.
For this reason, in the multi-position processing system, any change in the type or diameter of the fibers due to the replacement of the optical fibers may result in a change of upper limit of the laser output for the optical fibers. Therefore, even though it has been normal so far, the upper limit may be exceeded after the exchange, resulting in a damage of the optical fibers.
Furthermore, in the waveform-controlled laser processing apparatus, the user (operator) can set the pulse waveform and the pulse repetition frequency of the pulsed laser beam to any values. As a result, there may possibly be made such a setting as to exceed the laser output limit value for the optical fiber.
SUMMARY OF THE INVENTION
The present invention was conceived in view of the above problems involved in the prior art. It is therefore the object to provide a laser processing apparatus capable of automatically managing an incident (injecting) power of a laser beam on the optical fiber without any user's labor and burden, thereby achieving improvements in the protection of the optical fiber, the laser processing efficiency and process quality.
In order to attain the above object, according to a first aspect of the present invention, there is provided a laser processing apparatus in which a laser beam oscillatorily output from a laser oscillation unit is transmitted through an optical fiber to a remote laser processing site, the laser processing apparatus comprising optical fiber setting means for setting the type and diameter of the optical fiber; laser output upper limit finding means for finding a laser output upper limit of the laser beam depending on the type and diameter of the optical fiber which have been set by the optical fiber setting means; laser output setting means for setting a laser output of the laser beam; and judgment means for comparing the laser output value which has been set by the laser output setting means with the laser output upper limit which has been found by the laser output upper limit finding means, to judge whether the laser output set value exceeds the laser output upper limit.
The laser output upper limit finding means may include storage means for storing in a table format the type and diameter of a plurality of optical fibers usable for the apparatus, and laser output upper limits corresponding to each type and diameter.
The laser output setting means preferably include reference waveform setting means for setting a reference waveform for laser output reference waveform with respect to the laser beam generated as a pulsed laser beam; repetition frequency setting means for setting a repetition frequency with respect to the laser beam; and laser output mean value arithmetic means for figuring out as the laser output set value a laser output mean value of the pulsed laser beam per a certain time on the basis of the reference waveform which has been set and of the repetition frequency which has been set.
The laser output setting means may include laser output set value arithmetic means for figuring out the laser output set value on the basis of a pulse width, a peak power value and a repetition frequency of the laser beam which has been generated as a pulsed laser beam.
Preferably the laser processing apparatus further comprises warning means for generating a warning when the judgment means judge that the laser output set value exceeds the laser output upper limit.
Preferably the laser processing apparatus further comprises means which prohibit the setting in the laser output setting means when the judgment means judge that the laser output set value exceeds the laser output upper limit.
According to a second aspect of the present invention there is provided a laser processing apparatus in which a laser beam oscillatorily output from a laser oscillation unit is transmitted through an optical fiber to a remote laser processing site, the laser processing apparatus comprising laser output upper limit finding means for finding a laser output upper limit of the laser beam depending on the type and diameter of the optical fiber; laser output mean value arithmetic means for detecting a laser output of the laser beam oscillatorily output from the laser oscillation unit to figure out a laser output mean value at a certain interval; and interruption means for interrupting an impingement of the laser beam onto the optical fiber when the laser output average value exceeds the laser output upper limit.
According to a
Kawamura Kouji
Sasaki Haruki
Evans Geoffrey S.
Miyachi Technos Corporation
Wenderoth Lind & Ponack, LLP.
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