JP4309666B2 - Laser output control method for laser marker and laser marker - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser marker that prints characters and the like on the surface of resin, wood, metal, and the like using laser light, and a laser oscillation starting method thereof.
[0002]
[Prior art]
This type of laser marker heats the surface of an object such as resin, wood, or metal with a laser beam emitted from a carbon dioxide laser or YAG laser, and locally discolors or deforms the surface to print characters or the like ( Marking or simply printing).
[0003]
As a method of deflecting the laser beam so that the beam spot of the laser beam moves along the surface of the object along the character to be printed, a method called vector scan is usually used. This is a method of moving an irradiation spot of a laser beam along a character or a line drawing by simultaneously controlling the deflection in the X direction and the Y direction of the laser beam using a galvanometer mirror. In order to perform printing efficiently and in a short time, a trajectory with a single stroke is selected as much as possible.
[0004]
The laser marker usually includes a head unit and a controller unit, and a laser oscillator and a laser deflection device (galvano mirror) are built in the head unit. The controller unit includes a control microcomputer and a memory for storing print data and font data. The print data includes information such as the type and size of characters and marks to be printed, the print position, and the print direction.
[0005]
The print data given to the controller unit from the console or an external computer is temporarily stored in the memory. The microcomputer of the controller unit reads out the print data and generates expanded data when executing the printing process. That is, development data including line segment data and laser control data for defining a locus that the laser beam should follow is generated from the print data relating to the print contents and the font data.
[0006]
The generated development data is transferred from the controller unit to the head unit. In the head unit, the galvanometer mirror is controlled based on the line segment data included in the received development data, and laser on / off control is performed based on the laser control data.
[0007]
Control of laser output (laser intensity) is usually performed by duty control. That is, the laser output (its effective value) is changed by repeating ON / OFF in a relatively fast cycle and changing the ratio of the ON period to this cycle (duty cycle) (this is called the duty factor). By such duty control, it is possible to perform printing with an appropriate laser output corresponding to the difference in the material of the object such as resin, wood, metal and the printing speed.
[0008]
The on / off control of the laser based on the laser control data described above is different from the on / off in duty control for output control of the laser oscillator. Laser on / off control based on laser control data, for example, turn on the laser for parts that are continuously processed, such as one stroke, and turn off the laser when moving from the end part of processing to the start end part of the next processing. It means the control to make. On the other hand, on / off in the duty control means that the laser oscillator is repeatedly turned on / off at a duty factor set to a short period when the laser is on.
[0009]
The information for printing given from the console or the external computer to the controller unit includes set values of the laser output and the printing speed in addition to the aforementioned printing data. The user needs to set an appropriate laser output and printing speed according to conditions such as the material of the printing object.
[0010]
By the way, when a gas laser such as a carbon dioxide laser is used as a laser oscillator, poor start-up response can be a problem in terms of print quality. In other words, there is a time lag from when the laser oscillator is turned on until the actual laser output reaches the set output, so that the start end portion of the printing is in an incompletely processed state. As a result, the start end portion of the printed character becomes blurred.
[0011]
As a method for improving the above-described phenomenon, a method of making the laser oscillation off state close to the excitation state by a preliminary oscillation signal, that is, a pulse with a small duty factor, has been conventionally performed (for example, a special feature). No. 2000-22250).
[0012]
[Problems to be solved by the invention]
However, it is difficult to make the rise of the laser output steep even with the above-described conventional method, and further improvement measures have been demanded.
[0013]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a laser oscillation starting method and a laser marker with improved laser output rising performance.
[0014]
[Means for Solving the Problems]
The method of the present invention is a laser oscillation starting method for improving the rising performance of laser output when laser output is controlled by duty control in a laser marker that performs printing on the surface of an object using laser light. When a laser output control signal that repeats on / off at a duty factor and a duty cycle corresponding to the set laser output is given to the laser oscillator drive device in accordance with the laser on signal instructing the start of laser oscillation. The laser output control signal is configured to output one or a plurality of stretch pulses having an ON period longer than a normal pulse having an ON period determined by a factor, and then repeatedly outputting the normal pulse at the duty period. .
[0015]
The laser marker according to the present invention controls a laser oscillator and a laser deflecting device according to setting information including a laser output that outputs laser light, a laser deflecting device that deflects laser light, and laser output, printing speed, and printing contents. A laser marker that collects laser light emitted from a laser oscillator on the surface of the object and performs printing on the surface of the object by moving the light spot. The laser output duty control is performed by supplying a laser output control signal that repeatedly turns on and off at a duty factor and duty cycle corresponding to the set laser output to the laser oscillator driving device. Has an on-period longer than a normal pulse with an on-period determined by Characterized in that it is configured to repeatedly output with a duty cycle normal pulse after one or a plurality outputs stretch pulse duty cycle.
[0016]
According to the laser oscillation starting method and the laser marker using the laser oscillation start method as described above, one or more stretch pulses having an ON period longer than the normal pulse are output immediately after the laser ON command is issued. stand up. That is, the rising performance of the laser output is improved, and the print quality at the start end of printing is improved.
[0017]
In a preferred embodiment, the laser output control signal outputs three stretch pulses having an on period longer than the normal pulse having an on period (pulse width) determined by the duty factor, and then repeatedly outputs the normal pulse at the duty period. The on-period of the three stretch pulses is configured to be shortened in the first, second, and third order. In this way, the stretch pulse with the longest on-period is output first, and it is connected to the normal pulse of the set on-period while narrowing the on-period in three stages. An increase in the size of the chute can be suppressed. If the overshoot becomes large, the start end portion of the print is excessively emphasized, contrary to the case where the rise of the laser output is slow, and the print quality is deteriorated. This overshoot is suppressed by the three-stage stretch pulse as described above, and the print quality at the start end of printing is improved.
[0018]
In a further preferred embodiment, when the duty cycle is T and the on period of the normal pulse is tn, the first, second and third stretch pulses are turned on using a coefficient p smaller than 1 and a coefficient q of 1 or more. The processing device executes a process of calculating the period from an expression of p × T + q × tn or obtaining the period by referring to a table calculated and stored in advance. In the above formula, the first term is a constant increase portion determined only by the duty cycle regardless of the set value (that is, the duty factor) of the laser output, and the second term is an increase portion that changes according to the set value of the laser output. . According to such a configuration, if the coefficients (parameters) p and q when the print quality is the best by experiment are obtained in advance for each of the first, second, and third stretch pulses, Even if the laser output set according to the difference in material and the printing speed changes, it is possible to easily obtain the optimum on-period (pulse width) for the first, second and third stretch pulses. In this way, it is possible to improve the print quality at the print start end portion by the optimum laser oscillation start control.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
FIG. 1 is a schematic configuration diagram of a laser marker according to an embodiment of the present invention. The laser marker includes a head unit 1 and a controller unit 2, both of which are connected by a cable 4. A console (display / operation console) 3 using a liquid crystal display and a touch panel is connected to the controller unit 2 by a cable 5. The head unit 1 includes a laser oscillator 11 and a laser deflection device 12.
[0021]
The laser oscillator 11 is a laser tube using a carbon dioxide gas laser. The laser deflection device 12 includes a two-dimensional galvanometer mirror 12a and a condenser lens (fθ lens) 12b. The laser beam LB emitted from the laser oscillator 11 is deflected in the X direction and the Y direction (two-dimensionally) by the galvano mirror 12a and is condensed on the surface of the work (workpiece) WK by the condenser lens 12b. In this way, desired characters and symbols can be printed on the surface of the workpiece WK.
[0022]
FIG. 2 is a block diagram showing a circuit configuration of the laser marker according to the embodiment of the present invention. The head unit 1 includes a line receiver 13, a data restoration / timing adjustment unit 14, a D / A converter 15, and a galvano control unit 16 in addition to the laser oscillator 11 and the laser deflection device 12.
[0023]
The controller unit 2 includes a processing unit (MPU) 21, a print setting memory (SRAM) 22, a font data memory (ROM) 23, a development data memory (DRAM) 24, and a line driver 25. The processing device 21 stores the print data received from the console 3 and the set values of the laser output and the print speed in the print setting memory 22, generates expansion data from the print data and font data, and stores it in the expansion data memory 24. The process to memorize is executed.
[0024]
The print setting memory 22 can hold the stored contents even when the power is turned off by battery backup, and stores the print data related to the print contents received from the console 3, the set values of the laser output and the print speed. The font data memory 23 stores font data of various characters used for printing. The development data memory 24 temporarily stores development data generated from the print data, and the stored contents disappear when the power is turned off. The development data is time-series data composed of a plurality of bits including line segment data defining a locus that the laser beam should follow for printing and laser control data for laser on / off control.
[0025]
The console 3 is provided with a slot in which a memory card can be attached and detached and a read / write interface. Print data relating to print contents input from the console 3 can be stored in a memory card, read out when necessary, and transmitted to the controller unit 2. Further, print data created by a personal computer or the like can be transferred from the console 3 to the controller unit 2 via a memory card.
[0026]
It is also possible to connect a personal computer to the controller unit 2. As the connection interface, an RS232C serial port, a parallel port, a USB port, or the like is used. With the dedicated software installed in the personal computer, various settings for the controller unit 2, creation of print data, and the like can be performed using a personal computer screen, a full keyboard, a mouse, and the like.
[0027]
The print data and the set values of the laser output and the print speed transferred from the console 3 (including the memory card) or the personal computer to the controller unit 2 are temporarily stored in the print setting memory 22. Then, by the expansion process executed by the processing device 21, expansion data is generated based on the print data read from the print setting memory 22 and the font data read from the font data memory 23. It is temporarily stored in the memory 24.
[0028]
FIG. 3 is a flowchart showing an outline of the expansion process executed by the processing device 21 of the controller unit 2. In step # 101, the processing device 21 reads print data from the print setting memory 22. In the subsequent step # 102, the font data read from the font data memory 23 is referred to, and the print characters and symbols included in the print data are decomposed into a plurality of continuous processing curves (including straight lines). Each continuous processing curve is a continuous curve that moves the laser beam spot while continuously outputting the laser beam as in a single stroke.
[0029]
One continuous processing curve is represented as a set of a plurality of coordinates (corresponding to line segment data) for controlling the two-dimensional galvanometer mirror 12a of the laser deflecting device 12 at regular intervals. That is, one continuous machining curve is approximated by a plurality of line segments connected at a plurality of coordinates (bending points). Further, the movement (deflection) from the end of one continuous processing curve to the start of the next continuous processing curve is performed in a state where the output of laser light is stopped (zero power).
[0030]
In the next step # 103, a plurality of continuous machining curves are rearranged. The processing order of the continuous processing curves is selected so that the movement of the laser light spot is most efficient, that is, the total moving distance including the zero power movement between the continuous processing curves is the shortest. In the subsequent step # 104, a movement path (line segment with a laser output of zero) from the end of one continuous processing curve to the start of the next continuous processing curve is generated and added.
[0031]
For example, the letter “B” can be drawn with one continuous processing curve like a single stroke. On the other hand, since the letter “A” cannot be drawn with a single stroke, it is decomposed into a first continuous machining curve (straight line) “∧” and a second continuous machining curve (straight line) “−”. In this case, a movement path from the end of the first continuous machining curve (straight line) “∧” to the beginning of the second continuous machining curve (straight line) “−” is generated and added. This movement path is also expressed as a set of a plurality of coordinate points (line segment data) for controlling the two-dimensional galvanometer mirror 12a of the laser deflecting device 12 at regular intervals.
[0032]
In the subsequent step # 105, the time series line segment data (X coordinate and Y coordinate) are determined based on the continuous machining curve and moving path obtained as described above and the print speed setting read from the print setting memory 22. Data) and laser control data (laser output on / off distinction) are generated. The expanded data thus generated is temporarily written in the expanded data memory 24 in the next step # 106, and the expansion process is completed.
[0033]
Thereafter, the processing device 21 transfers the decompressed data read from the decompressed data memory 24 to the head unit 1 via the line driver 25 in accordance with a print execution command. Further, in synchronization with the laser control data included in the development data (which constitutes a laser on signal), laser output control data (which constitutes a laser output control signal) to be described later is generated by the processing device 21 and transferred to the head unit 1. Is done.
[0034]
As shown in FIG. 2, in the head unit 1 that has received the development data and the laser output control data via the line receiver 13, a data restoration / timing adjustment unit (corresponding to a driving device) 14 includes a laser control included in the development data. On / off control of the laser oscillator 11 and laser output duty control are executed based on the data and the laser output control data. In addition, data corresponding to the moving amount of the laser beam obtained from the line segment data included in the development data is given to the D / A converter 15.
[0035]
The D / A converter 15 converts the data corresponding to the movement amount into an analog voltage and gives it to the galvano controller 16. The galvano controller 16 drives the two-dimensional galvanometer mirror 12a in accordance with the applied analog voltage, whereby the beam spot of the laser beam moves to a predetermined position. In this manner, the laser beam emitted from the laser oscillator 11 is sequentially deflected by the two-dimensional galvanometer mirror 12a, and the beam spot of the laser beam moves on the surface of the workpiece WK, so that desired characters and symbols are formed on the surface of the workpiece WK. Etc. are printed.
[0036]
FIG. 4 schematically shows a laser-on signal composed of laser control data and a laser output control signal composed of laser output control data. In FIG. 4, as the laser on signal changes from the L level (off) to the H level (on) and activation of laser oscillation is instructed, three stretch pulses SP1, SP2 and SP3 of the laser output control signal are indicated. Is output at the duty cycle T, and the normal pulse NP having a duty factor corresponding to the set laser output is repeatedly output at the duty cycle T.
[0037]
The normal pulse NP has an on period (pulse width) tn determined by a duty factor corresponding to the set laser output. That is, tn / T is the duty factor. The three stretch pulses SP1, SP2 and SP3 have on periods t1, t2 and t3 longer than the on period tn of the normal pulse NP. Thereby, the time delay until the actual laser output reaches the set laser output is shortened. That is, the rising performance of the laser output is improved. When the rising performance of the laser output is poor and it takes time to reach the set laser output, the starting end portion of the printing becomes incompletely processed and becomes blurred. Such deterioration in print quality is improved by the stretch pulses SP1, SP2 and SP3.
[0038]
Further, the ON periods t1, t2, and t3 of the three stretch pulses SP1, SP2, and SP3 are shortened in order. Thus, the first stretch pulse SP1 of the longest on period t1 is output first, and the on period is divided into the second stretch pulse SP2 (on period t2) and the third stretch pulse SP3 (on period t3) in three stages. While being narrowed, the normal pulse NP in the set ON period tn is connected. By doing so, it is possible to suppress an increase in overshoot while making the rise of the laser output steep. When the overshoot becomes large, the start end portion of the print is excessively processed, contrary to the case where the rise of the laser output is slow, and the print quality is deteriorated. The above-described overshoot is suppressed by the stretch pulse in which the ON period is narrowed in three steps as described above, and the print quality at the print start end portion is further improved.
[0039]
How large the on periods t1, t2, and t3 of the three stretch pulses SP1, SP2, and SP3 are set with respect to the on period tn of the normal pulse determined by the set value (duty factor) of the laser output will be described below. In advance, it is obtained by experiments.
[0040]
The laser output setting value (duty factor) is set to an appropriate value according to the difference in the material of the printing object and the printing speed. Therefore, first, the on periods t1, t2 and t3 of the three stretch pulses SP1, SP2 and SP3 are defined as a function of the duty factor (tn / T) or the on period tn of the normal pulse as follows.
t1 = p1 × T + q1 × tn
t2 = p2 × T + q2 × tn
t3 = p3 × T + q3 × tn
[0041]
However, p1, p2 and p3 are coefficients smaller than 1, and q1, q2 and q3 are coefficients of 1 or more. In each equation, the first term is a constant increase portion determined only by the duty cycle T regardless of the laser output setting value (duty factor), and the second term is the laser output setting value (duty factor, and hence the normal pulse). It is an increasing part that changes according to the on period tn).
[0042]
In this way, the on periods t1, t2, and t3 of the three stretch pulses SP1, SP2, and SP3 are expressed by equations, and the coefficients p1, p2, p3, q1, q2, and What is necessary is just to obtain | require the value of q3. However, since there are six coefficients (parameters) to be obtained, it is necessary to set a standard of values that are considered appropriate for each parameter to some extent and conduct experiments while changing each parameter efficiently in the vicinity of that value. .
[0043]
In one embodiment, as a result of various experiments, it was found that the print quality was best when t1, t2, and t3 were set as follows. However, the duty cycle T is constant at 40 microseconds (frequency is 25 kHz).
t1 = 6 + 1.25 × tn That is, p1 = 0.15 q1 = 1.25
t2 = 1 + 1.25 × tn That is, p2 = 0.025 q2 = 1.25
t3 = 2 + tn That is, p3 = 0.05 q3 = 1
[0044]
FIG. 5 shows the three stretch pulse on-periods t1, t1 obtained from the above equation when the duty factor corresponding to the set value of the laser output (and hence the normal pulse on-period tn) is changed at an appropriate interval. It is a table which shows the value which rounded t2 and t3 to the integer. In addition, values obtained by evaluating the printing results (results of the printing start end portion) at each duty factor in five stages are also shown. As shown in FIG. 6, the printing result indicates that the intermediate value 3 of the five-step numerical value is the optimum printing result. The larger the numerical value, the stronger the start end portion of the printing, and conversely, the printing becomes smaller as the numerical value becomes smaller. It shows that the start end portion of is blurred (blurred).
[0045]
For reference, the same experiment as FIG. 5 when the values of the coefficients q1 and q2 are changed in the decreasing direction and the increasing direction in the expressions representing the on periods t1, t2, and t3 of the above three stretch pulses. The results are shown in FIGS. In these examples, the coefficient q3 was not changed.
[0046]
FIG. 7 shows a case where the values of the coefficients q1 and q2 are reduced from 1.25 to 1.0, and the on periods t1, t2, and t3 of the three stretch pulses are expressed by the following equations. In this example, p2 is increased from 1 to 3.
t1 = 6 + tn
t2 = 3 + tn
t3 = 2 + tn
[0047]
FIG. 8 shows a case where the values of the coefficients q1 and q2 are increased from 1.25 to 1.5, and the on periods t1, t2, and t3 of the three stretch pulses are as follows. In this example, p2 is 1 as in FIG.
t1 = 6 + 1.5 × tn
t2 = 1 + 1.5 × tn
t3 = 2 + tn
[0048]
The following can be understood from the experimental results shown in FIGS. Under the conditions shown in FIG. 5, when the duty factor is 25% or less, the printing start end portion is processed slightly strongly, but when the duty factor is 30% or more, a good printing result is obtained. Under the conditions shown in FIG. 7, the print start end portion is processed slightly stronger when the duty factor is relatively small, and the print start end portion becomes slightly weak (blurred) when the duty factor is near the center of the practical range. Under the conditions shown in FIG. 8, the print start end portion is slightly too strong when the duty factor is near the center of the practical range. From the above comparative study results, it can be seen that the conditions of FIG. 5 are suitable.
[0049]
In the actual experiment, the print results were obtained while changing the values of the parameters (coefficients) p1, p2, p3, q1, q2, and q3 into a plurality of combinations including the above example using an FPGA (rewritable gate array). Evaluation was performed. As a result, parameters (coefficients) for obtaining the on periods t1, t2, and t3 as shown in FIG. 5 under the condition of the duty cycle T = 40 microseconds, that is, p1 = 0.15, p2 = 0.025, It was found that p3 = 0.05, q1 = 1.25, q2 = 1.25 and q3 = 1 were preferable. However, since these specific values vary depending on the duty cycle, the maximum output of the laser, and other conditions, the values of preferable parameters (coefficients) p1, p2, p3, q1, q2, and q3 are experimentally determined in advance according to each application. Need to ask.
[0050]
In the present embodiment, the processing device 21 calculates the on-periods t1, t2, and t3 of the three stretch pulses for each duty factor (laser output set value) by calculation based on the above-described equation. As another method, the ON periods t1, t2, and t3 corresponding to each duty factor are calculated in advance, and the results are stored as a lookup table as shown in FIG. The on periods t1, t2, and t3 may be obtained with reference to FIG.
[0051]
In the present embodiment, the on-periods t1, t2, and t3 of the three stretch pulses are calculated by the processing device (microprocessor) 21 provided in the controller unit 2, but a similar processing device is provided in the head unit 1, You may comprise so that the ON period t1, t2, and t3 of three stretch pulses may be calculated | required by the calculation or reference of a look-up table with the processing apparatus by the head part 1 side.
[0052]
The present invention is not limited to the above embodiment, and can be implemented in various forms. For example, the number of stretch pulses is not limited to three, but may be one or two, or four or more.
[0053]
【The invention's effect】
As described above, according to the laser oscillation starting method and the laser marker of the present invention, one or a plurality of stretch pulses having an ON period longer than the normal pulse are output immediately after the laser ON command is issued. Stand up steeply. That is, the rising performance of the laser output is improved, and the print quality at the start end of printing is improved. In addition, by providing three stretch pulses and reducing the on-period of each stretch pulse in steps to connect to normal pulses, a steep rise can be realized while suppressing overshoot of the laser output. The print quality at the start end is further improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a laser marker according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a circuit configuration of a laser marker according to an embodiment of the present invention.
FIG. 3 is a flowchart showing an outline of an expansion process executed by a processing device of a controller unit.
FIG. 4 is a diagram schematically showing a laser-on signal constituted by laser control data and a laser output control signal constituted by laser output control data.
FIG. 5 is a diagram illustrating printing of values obtained by calculating suitable on periods t1, t2, and t3 of three stretch pulses and rounding them to integers when a duty factor corresponding to a set value of laser output is changed at an appropriate interval. It is a table which shows evaluation of a result.
FIG. 6 is a table relating to an explanation of a printing result represented by a 5-step numerical value in FIG.
FIG. 7 is a table showing the results when the values of coefficients q1 and q2 are decreased in FIG.
FIG. 8 is a table showing the results when the values of the coefficients q1 and q2 are increased in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Head part 2 Controller part 11 Laser oscillator 12 Laser deflection | deviation apparatus 21 Processing apparatus 22 Memory for print setting

Claims (4)

In a laser marker comprising a head unit and a controller unit that performs printing on the surface of an object using laser light , the printing process is performed when laser output control is performed by duty control based on laser control data from the controller unit. a Relais chromatography the output control method to improve the rise performance of the laser output from the head portion,
A laser oscillator that configures the head unit with a laser output control signal that repeats on / off at a duty factor and a duty cycle corresponding to the set laser output in accordance with a laser on signal that indicates a laser output included in the laser control data When giving to the drive unit of
The laser output control signal is configured to repeatedly output the normal pulse at the duty cycle after outputting one or more stretch pulses having an on period longer than the normal pulse of the on period determined by the duty factor at the duty cycle. A method for controlling laser output in a laser marker . A laser oscillator for outputting laser light; a laser deflection apparatus for deflecting the laser light; and a processing apparatus for controlling the laser oscillator and the laser deflection apparatus in accordance with setting information including laser output, printing speed and printing contents. A laser marker that focuses laser light emitted from the laser oscillator on the surface of the object and performs printing on the surface of the object by moving the light spot;
The processing unit, control of the laser output at the time of executing the print processing by providing a laser output control signal repeatedly turned on and off by the duty factor and a duty cycle corresponding to the laser output set in the driving unit of the laser oscillator The laser output control signal repeats the normal pulse at the duty cycle after outputting one or more stretch pulses having an on period longer than the normal pulse of the on period determined by the duty factor at the duty cycle. A laser marker configured to output.   The laser output control signal is configured to repeatedly output the normal pulse at the duty cycle after outputting three stretch pulses having an on period longer than the normal pulse of the on period determined by the duty factor at the duty cycle. 3. The laser marker according to claim 2, wherein an ON period of the three stretch pulses is configured to be shortened in the first, second, and third order.   When the duty cycle is T and the on period of the normal pulse is tn, the on period of the first, second and third stretch pulses is set to p × using a coefficient p smaller than 1 and a coefficient q of 1 or more. 4. The laser marker according to claim 3, wherein the processing apparatus executes a process calculated from an expression of T + q × tn or obtained by referring to a table calculated and stored in advance.

Images