GB2455588A

GB2455588A - Laser processing control

Info

Publication number: GB2455588A
Application number: GB0802817A
Authority: GB
Inventors: Simon George Caiger
Original assignee: GSI Group Ltd
Current assignee: Novanta Technologies UK Ltd
Priority date: 2007-12-10
Filing date: 2008-02-15
Publication date: 2009-06-17
Also published as: WO2009074786A1; GB0802817D0; GB0724057D0

Abstract

A method and system of operating a laser 2 comprising providing a scan head controller 5 and a laser controller 3, loading related parameter sets/processes into the scan head controller 5 and laser controller 3 and, at time of operation, generating trigger signals and causing the scan head and laser controller to cycle through the parameter sets/processes, synchronized by each trigger signal.

Description

Laser Processin2 This invention relates to control and/or monitoring of laser processing using a scan head, such as a galvanometer scan head.

When lasers are used for material processing operations (such as cutting or welding) a scan head is often used and this may typically be a galvanometer scan head which scans the laser beam across the workpiece in a desired pattern. Figure 1 shows a typical previously proposed galvohead control system.

The laser beam output from a laser 2 operated by laser control software 3 is applied to a galvanometer scan head I and from there to a workpiece 4.

The laser controller 3 controls various parameters of the laser beam such as pulse rate, energy level, and so on, and can be used to precisely control the laser beam. The scan controller generates signals which control both the scan head (movement of the scan head) and also control the laser control card 3 and these are transmitted over a communications line 6 between the scan controller and the laser controller 3.

This is obviously quite complicated processing. Existing galvanometer scan head software such as SCAPSIM and WinLase1M are primarily focused on the programming of the actual scan head profile sent from the scan controller 5 to the scan head. Laser parameter control (changing complete parameter sets or laser output power adjustment) is normally a secondary function and this is achieved, as described, by means of analogue, digital or serial communications outputs (shown generally as communication line 6) from the scan controller 5 to the laser control electronics 3. Thus, during a laser processing operation, the scan controller 5 is continually generating control signals for the scan head and also control signals to control the parameters in the laser. This can limit the performance of the system. In addition, there is a risk that the scan controller 5 can send control signals to the laser which seek to request the laser to perform beyond its capabilities. For example, if a laser is performing at a particular pulse rate, then the same controller might demand that a pulse rate in excess of its functional pulse rate be achieved and this can cause malfunction.

The present invention arose in an attempt to provide an improved control and/or monitoring of systems for laser processing using a scan head.

According to the present invention in a first aspect, there is provided a method of operating a laser comprising; providing a scan head controller and a laser controller, loading related parameter sets/processes into the scan head controller and laser controller and, at time of operation, generating trigger signals and causing the scan head and laser controller to cycle through the parameter sets/processes, synchronized by each trigger signal.

The scan controller may generate each trigger signal.

Thus, the scan controller and laser controller each have a list of parameter sets (processes) and, as each trigger signal is generated by the scan controller, are controlled to run the next process on their list. These are synchronized with each other by the trigger signals.

The invention further provides a laser control system including any one or more of the novel features or combinations of features disclosed herein, or operating according to any of the novel methods or combinations of methods disclosed herein.

In a further aspect the invention provides a laser system comprising a laser control system, a scan control system, a scan head and a trigger generating means, wherein the scan controller and laser controller each include means for storing a plurality of predetermined steps and the trigger controller is adapted to provide trigger signals to cause the scan controller and laser controller to step through their lists, in synchronism with the trigger signal.

This invention provides a scan head software application designed specifically for laser processing. An integrated user interface is provided for the purpose of programming both the laser and the scan head. This same user interface is used for monitoring and controlling the laser whether using a scan head or not.

By using a common user interface, single process recipe is generated containing both scan head and laser parameters. This data is separated into two streams. The first stream, sent to the scan control card, contains the scan head positional data and number of shots to be fired at each position. The second data stream, sent to the laser control card, contains a sequential list of laser parameters required as each trigger pulse is applied to the laser (a process cycle). As a process runs, the scan control card need only generate a single laser trigger output when in position at each processing location. The laser control card takes care of the required laser parameters at each processing location.

In this way, the laser control card is aware of what processing parameters are required before the arrival of subsequent trigger pulses from the scan controller and can use scan head move and settling times to set up the laser parameters in readiness for the next incoming trigger pulse.

Another feature of this invention is that by having a common user interface for both laser and scan head, scan head delays may be optimised according to the laser parameter sets to be used. For example, a GSI Group plc JK series lamp pumped laser may not be externally triggered at a rate faster than that defined by the active parameter set. The external trigger signal is used by the scan controller to fire the laser when it has reached a processing location and any trigger signals arriving at a rate faster than that defined by the current parameter set will be ignored, resulting in missing welds. Using existing, commercially available, software such as SCAPST' and WinLase1M, it is possible for the user to easily make the mistake of programming the system to deliver trigger pulses at an illegal rate. With the system described in this invention, the pulse rate data for all parameter sets is shared, via a software interface, with the scan head profile programming module. The scan head profile programming module is then not only able to ensure that trigger pulses do not occur at a rate faster than the laser is capable of but also to ensure that delays are fully optimised so as to achieve the fastest possible processing speed of which the laser is capable.

Another feature of this invention is that by introducing a vision system and displaying the acquired image in the scan head programming canvas, further enhancements may be made to the speed of programming a process recipe by defining process locations and required parameters directly onto the part to be processed. This visual programming method is not restricted to live camera images and may be used by displaying an imported still image (bmp, jpeg, etc) and using that as the scan head profile programming template.

Amongst other benefits, the invention provides: 1. Fully integrated software application for the programming of both scan head and laser parameters.

2. Reduced analogue and digital 10 and serial communications requirements.

3. Laser controller knows what parameters are to be required before a trigger pulse arrives and is therefore able to set parameters for subsequent processing locations before they are reached.

4. Shared data between laser and scan head software modules allows optimisation of processing speed and eliminates possibility of scan head controller operating outside the allowable laser processing limits.

5. Background image display (live video or still image) speeds up the process development time.

Preferably, the trigger signal generator is part of the scan controller.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a previously proposed scan head control system; Figure 2 shows a scan head control system embodying the present invention; and Figure 3 shows schematically synchronized outputs from a scan control unit and laser unit.

As shown in Figure 2, a laser system comprises a laser 2 including laser control hardware/software 3. A laser beam is generated in known manner in the laser and applied to a scan head 1. This may be a galvanometer type scan head and the design of these is well known in the art. This is used to cause the laser beam to scan across a workpiece 4 to process the workpiece, typically by cutting, welding or other laser processing. A scan controller 5, which may typically be a portable computer (PC) or other means, includes a laser and scan head graphical user interface 10 and scan control hardware 11, in addition to other components not shown. The scan control hardware causes position control data P to be sent to the scan head to control the movements of the scan head. Between the PC 5 and laser 2 there is a serial communications link (or other data communications link) 6.

In embodiments of the invention, there is firstly a pre-processing set-up then a System Programming Using a graphical user interlace at PC 5, an operator enters a series of locations to which the scan head should visit. For each location the user defines the laser parameter set to be used (laser power) and the number of shots required.

Pre-Processing Set-Ui, Before running the process for the first time, the operator initiates a program load sequence from the graphical user interface software which runs as follows: (a) A laser parameter set data known by the laser control side of the graphical user (b) interface software is shared with the scan head control side of the graphical user interface software.

(c) Using a maximum laser pulse frequency (maximum laser recharge rate) parameter. the scan control side of the graphical user interface software calculates optimum delays required to ensure that the scan sequence runs as fast as possible but without missing shots due to trying to retrigger the laser before it has recharged.

(d) The scan control side of the graphical user interface software generates a program list of scan head locations to be visited and downloads this list to the scan control hardware.

(e) The scan control side of the graphical user interface software generates a laser program list of parameter set required for each shot to be fired. The order of this list exactly matches the order in which the scan controller will visit each location (I) The scan control side of the graphical user interface software passes the laser program list to the laser control side of the graphical user interface software which then downloads this list (process cycle) to the laser control hardware.

Process Run Once the System Programming and Pre-Processing Set-Up steps have been completed, the following Process Run sequence may be run as many times as required: (a) A start signal is applied to the laser control hardware. This may be via an external hardware signal applied to the laser digital machine interface or via a soft key on the laser control side of the graphical user interface.

(b) Laser control hardware starts running the process cycle, setting a digital output (sequence started) 20 to indicate this fact. The sequence started digital output is connected to the start sequence input on the scan control hardware which causes the scan head to start visiting the pre-programmed locations defined in its program list.

(c) As each location is visited by the scan head, a trigger signal, generated by the scan controller causes the laser to fire a shot. The timing of this trigger signal is exactly controlled by the scan controller to ensure that the laser is triggered as fast as it possibly can but without attempting to re-trigger the laser before it is available (recharged).

(d) After each trigger signal is received, the laser controller has advance knowledge of parameters required for the next location. It is therefore able to prepare itself (load parameters etc) for the next location before the next trigger signal arrives i.e. while the scan head is in motion. Effectively, the process runs as two separate program lists synchronised by the trigger signal.

ExamDle Program Lists Scan Controller List Trigger Signal # Laser Controller List Goto Position Xl, Yl and 1 Fire parameter set 1 generate 1 trigger pulse Goto Position X2, Y2 and 2 Fire parameter set 2 generate 2 trigger pulses Fire parameter set 2 Goto Position X3, Y3 and 4 Fire parameter set 7 generate I trigger pulse Gob Position X4, Y4 and 5 Fire parameter set 2 generate 3 trigger pulses 6 Fire parameter set 4 7 Fire parameter set 7 Goto Position X5, Y5 and 8 Fire parameter set 3 generate 1 trigger pulse As described, the separation of the trigger signals is preferably timed by the scan controller to ensure that the laser is not triggered too fast but is triggered as fast as possible.

In relation to the figure, note that: (1) Data is typically passed from the graphical user interface to scan control hardware via software interface.

(2) A serial communications interface to laser is only required under the following conditions. In all other cases, this interface may be omitted: a. For Pre-Processing set-up stage in order for the laser control side of the graphical user interface to obtain current laser parameter set data.

b. If process initiation is required to be carried out via a soft key as opposed to a Start button as shown.

c. if it is required to monitor other laser functions while processing is carried out.

Figure 3 shows an example in which, in response to a first trigger signal, the scan control sets position X, Y, and the laser operates with parameter set P set 1. A second trigger signal then triggers position X2, Y2 and parameter set P set 2, and so on.

There is also an optional Z axis which may be implemented in order to defocus the laser beam and achieve spot size variation. If the Z axis is implemented, the scan controller program list consists of three coordinates for each processing location (X, Y and Z).

Key Benefits of Invention Over Existing Systems 1. Existing systems have no prior knowledge of the laser parameter data, particularly the maximum laser trigger frequency. The onus is therefore on the operator to ensure that the scan head delays are set correctly such that the laser is not re-triggered too quickly resulting in missing pulses. It is also a particularly difficult task to ensure that the laser is triggered as fast as possible and so achieve fastest possible processing speed. The above system is self calibrating for the maximum possible processing speed.

2. Existing systems require additional, costly, digital, analogue or permanent (possibly slow) serial interfaces in order to achieve laser parameter set changes for different processing locations. The above system executes two program lists, one in the scan controller and the other in the laser. The laser is, therefore, able to manage itself in terms of parameter set changes required for different locations.

3. In existing systems, the laser has no prior knowledge of the parameters that will be required at subsequent processing locations. The laser will only know what is required of it when the scan control hardware tells it via a digital, analogue or serial interface. The present system is pre-emptive in that the laser knows what parameters are required for all processing locations before the scan head has reached position. The laser is therefore able to carry out parameter settings before a location is reached. Laser Processin2 This invention relates to control and/or monitoring of laser processing using a scan head, such as a galvanometer scan head.

The scan controller may generate each trigger signal.

2. Reduced analogue and digital 10 and serial communications requirements.

Preferably, the trigger signal generator is part of the scan controller.

3. In existing systems, the laser has no prior knowledge of the parameters that will be required at subsequent processing locations. The laser will only know what is required of it when the scan control hardware tells it via a digital, analogue or serial interface. The present system is pre-emptive in that the laser knows what parameters are required for all processing locations before the scan head has reached position. The laser is therefore able to carry out parameter settings before a location is reached.

Claims

Claims 1. A method of operating a laser comprising providing a scan head controller and a laser controller, loading related parameter sets/processes into the scan head controller and laser controller and, at time of operation, generating trigger signals and causing the scan head and laser controller to cycle through the parameter sets/processes, synchronized by the trigger signals.
2. A method as claimed in claim 1, wherein the trigger signals are generated by the scan controller.
3. A method as claimed in claim I or claim 2, wherein the laser controller has a list of parameter sets and, as each trigger signal is generated, is controlled to run the next process on its list.
4. A method as claimed in claim 3, wherein the scan controller has a list of parameter sets and generates one or more trigger signals as it performs each process list.
5. A method as claimed in any preceding claim, wherein the scan head controller generates one or more trigger signals after each of its processes and the laser control operates according to a particular predetermined parameter set in response to each trigger signal.
6. A method as claimed in any prcceding claim, including an initial step of loading related parameter sets into, respectively, the scan controller and laser controller.
7. A method as claimed in claim 6, wherein the laser process set is determined by determining suitable parameters dependent upon the scan parameters.
8. A method as claimed in claim 7, wherein a parameter is the maximum laser recharge rate.
9. A laser system comprising a laser controller, a scan control system, a scan head and a trigger generating means, wherein the scan controller and laser controller each include means for storing a plurality of predetermined processes and the trigger generating means provide trigger signals to cause the scan controller and laser controller to step through their process list, in synchronism with the trigger signals.
10. A system as claimed in claim 9, wherein the trigger generator is adapted to provide trigger signals to the scan controller and the laser controller.
II. A systems as claimed in claim 9 or claim 10, wherein the trigger generating means is at the scan controller side.
12. A system as claimed in any of claims 9 to 11, adapted such that as the scan controller steps through a process list, trigger signals are sent to the laser controller to cause the laser controller to step through its process list.
13. A laser scan control system substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.
14. A method of controlling a laser substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.

14. A method of controlling a laser substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.

Claims 1. A method of operating a laser comprising providing a scan head controller and a laser controller, loading related parameter sets/processes into the scan head controller and laser controller and, at time of operation, generating trigger signals and causing the scan head and laser controller to cycle through the parameter sets/processes, synchronized by the trigger signals.

2. A method as claimed in claim 1, wherein the trigger signals are generated by the scan controller.

3. A method as claimed in claim I or claim 2, wherein the laser controller has a list of parameter sets and, as each trigger signal is generated, is controlled to run the next process on its list.

4. A method as claimed in claim 3, wherein the scan controller has a list of parameter sets and generates one or more trigger signals as it performs each process list.

5. A method as claimed in any preceding claim, wherein the scan head controller generates one or more trigger signals after each of its processes and the laser control operates according to a particular predetermined parameter set in response to each trigger signal.

6. A method as claimed in any prcceding claim, including an initial step of loading related parameter sets into, respectively, the scan controller and laser controller.

7. A method as claimed in claim 6, wherein the laser process set is determined by determining suitable parameters dependent upon the scan parameters.

8. A method as claimed in claim 7, wherein a parameter is the maximum laser recharge rate.

9. A laser system comprising a laser controller, a scan control system, a scan head and a trigger generating means, wherein the scan controller and laser controller each include means for storing a plurality of predetermined processes and the trigger generating means provide trigger signals to cause the scan controller and laser controller to step through their process list, in synchronism with the trigger signals.

10. A system as claimed in claim 9, wherein the trigger generator is adapted to provide trigger signals to the scan controller and the laser controller.

II. A systems as claimed in claim 9 or claim 10, wherein the trigger generating means is at the scan controller side.

12. A system as claimed in any of claims 9 to 11, adapted such that as the scan controller steps through a process list, trigger signals are sent to the laser controller to cause the laser controller to step through its process list.

13. A laser scan control system substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.