Electric heating – Metal heating – By arc
Reexamination Certificate
2001-12-04
2003-09-02
Elve, M. Alexandra (Department: 1725)
Electric heating
Metal heating
By arc
C219S121830
Reexamination Certificate
active
06614002
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a laser machining head for the machining of a workpiece by means of a laser beam, in particular for the welding or cutting of workpieces by laser beams.
DESCRIPTION OF THE RELATED ART
In order to be able to monitor the machining operation, that is in particular the welding or cutting process, depending on the task in hand different sensors for measuring the radiation coming from a zone of work or interaction determined by the working focus are necessary. These sensors are usually flange-mounted laterally onto the laser machining head. In this case UV sensors for monitoring any plasma forming over the zone of interaction, a temperature sensor or infrared sensor for detecting the radiation coming from the region around what is known as the keyhole determined by the working focus by which peripheral fusion and the temperature profile during machining can be monitored and a back-reflection sensor which detects the back radiation of the laser from the keyhole are standardly provided.
In many tasks, however, it is only by means of statistical studies in prototype production that it is possible to find the right combination of sensors which allow as significant an analysis of the process parameters as possible. This results in a change in the external geometry of the head which plays an important role in numerous operational tasks. Since, for example, when burrowing into components collisions must be avoided, a change in the geometry of the head is often not possible.
From the
catalogue of the company precitec,
2000 issue, page 41, a laser welding monitor is already known which is flange-mounted laterally onto a laser machining head. Depending on which sensors are necessary for monitoring the process in laser welding, the known laser welding monitor must be correspondingly modified.
JP 2000 225 481 discloses a laser machining head on which various sensors for detecting the radiation coming from the zone of interaction are arranged one behind the other. In this case the radiation coming from the zone of interaction first of all passes through the focusing optics for the machining beam and then encounters beam splitters or deflecting mirrors which direct the radiation onto the corresponding sensors. Depending on which and how many sensors are necessary for the process monitoring appropriate sensor housings must be fitted on the side of the laser machining head facing away from the working focus.
BRIEF SUMMARY OF THE INVENTION
Proceeding from this the aim underlying the invention is to develop further a laser machining head of the type specified at the outset in such a way that with fixed and compact external dimensions, it allows simple adaptation of the sensors to the machining tasks in question. This aim is achieved by means of a laser machining head.
Thus, in a laser machining head for the machining of a workpiece by means of a laser beam having a housing which has an inlet opening and an outlet opening between which a passage for the laser beam is constructed through which a pathway for the working beam is led; focusing optics for focusing the laser beam into a working focus which is located outside the housing at a distance from the outlet opening; and a sensor arrangement, it is provided according to the invention that the sensor arrangement comprises a sensor module arranged in a side wall of the housing beside the laser beam passage and that a beam deflecting device directs radiation coming from a zone of interaction determined by the working focus onto sensors in the sensor arrangement so that at least a portion of the radiation can be detected for monitoring the machining of a workpiece.
Due to the use according to the invention of a sensor module arranged in a side wall of the laser machining head, it is a simple matter to achieve that the sensors needed for the machining task in question and the laser wavelength employed can be integrated into the laser machining head without the necessity of altering the external dimensions of the laser machining head.
In an advantageous development of the invention, it is provided that the beam deflection device comprises imaging optics which are arranged behind the focusing optics with respect to the radiation coming from the zone of interaction in order to image the zone of interaction onto the sensor module.
A further refinement of the invention is characterised in that the beam deflection device possesses a first beam splitter, which separates a portion of the radiation coming from the zone of interaction out of the optical path of the working beam, and a second beam splitter which directs a portion of the incident radiation to the sensor module while it allows a further portion through, the second beam splitter being arranged in a side wall of the housing ahead of a connecting aperture to which an observation device can be connected. By this means, it is made possible in the case of certain end uses which require sectional or close-up tracking during machining to attach an appropriate observation device, e.g. a video camera or the like, to the laser machining head without this having an adverse effect on the sensor arrangement.
The second beam splitter is suitably arranged in a side wall of the housing opposite the sensor module, the beam deflection device having first and second deflection mirrors in order to redirect the portion of the radiation coming from the zone of interaction separated out by the beam splitters transversely across the passage to the side of the sensor module or parallel to the side wall accommodating the sensor module.
In a preferred development of the laser machining head according to the invention, it is provided that the sensor module is constructed as a side wall module. By this means, the sensor arrangement can not only be changed in simple manner according to the requirements at the time of the planned machining task and the laser sources employed but also the servicing of the sensor arrangement is likewise simplified since the side wall module need merely be exchanged for another one having the same sensors. This means downtime for the laser machining system due to servicing of the sensor arrangement can be reduced to a minimum.
It is possible in principle to equip the sensor module with only one sensor when, for example, only the temperature of the zone of interaction or the laser light reflected back from the working focus need be measured integrally. The advantages of the arrangement according to the invention can, however, be especially well exploited when in particular the sensor module has two or more sensors to which the incident radiation can be delivered via a third beam splitter.
If two sensors are provided it is particularly advantageous for the third beam splitter, on which the zone of interaction is imaged by the imaging optics, to be constructed as a reflecting position filter aperture so that the sensors detect different regions of the zone of interaction.
It is advantageous if individual sensors in the sensor arrangement comprise a filtering device so that they detect a selected spectral range of the radiation coming from the zone of interaction.
In a particularly advantageous development of the invention, it is provided that in the sensor module a reference sensor is provided which detects a portion of the working laser radiation separated out by the first beam splitter.
Another useful development of the invention distinguishes itself in that the sensor arrangement encompasses at least one but preferably two or more sensors arranged in the region of the inlet opening in one or different side walls of the housing which is or are constructed for the detection of radiation, in particular plasma radiation, coming from the zone of interaction.
In order to permit a high quality and interference-free laser operation, it is provided that the sensor arrangement for monitoring a protective glass, which is arranged in the working beam path between the outlet opening and the focusing optics, comprises at least one further sensor which is arranged i
Birch & Stewart Kolasch & Birch, LLP
Elve M. Alexandra
Precitec KG
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