JP3531629B2 - Laser beam deflection control method in stereolithography system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam deflection control method in a stereolithography system.

[0002]

2. Description of the Related Art A stereolithography system irradiates a solidifying agent with a laser beam through a deflecting means to solidify a specific portion of the solidifying agent to form a solidified layer, and a new layer is formed on the solidified layer. By repeating the formation of various solidified layers, a desired three-dimensional model is formed as a stack of a plurality of solidified layers, and the shape accuracy of the three-dimensional model to be created is determined by scanning a laser beam based on CAD data. It is greatly affected by the scanning accuracy at the time of.

In particular, even if the irradiation position of the laser beam is calibrated just before the start of the model forming work, the deviation of the oscillation point of the light source of the laser beam and the deflection for scanning the laser light source or the laser beam due to the change of the environmental temperature are caused. The irradiation position is displaced due to the deflection of the supporting member that supports the means, the temperature drift of the deflecting means itself, and the like.
As described in Japanese Patent No. 8574, it is possible to obtain a highly accurate three-dimensional model by correcting the positional deviation during the model forming work.

[0004]

By the way, the deflecting means for deflecting the laser beam for scanning is generally shown in FIG.
As shown in FIG. 2, a galvano scanner including two scan mirrors 21 and 22 that rotate about two orthogonal axes is used. The scan mirror 21 is used for X-axis scanning and the scan mirror 22 is used for Y-axis scanning. , Θx is the optical angle of the scan mirror 21, θy is the optical angle of the scan mirror 22, and the laser beam irradiation position on the laser beam irradiation surface is (X, Y), the two scan mirrors 21,
The relationship between the movement (θx, θy) of 22 and the laser beam irradiation position is Δθx ≠ k1 * ΔX, Δθy≈k2 * ΔY where k1 and k2 are coefficients and are independent and non-linear. As shown in FIG. 10, it is difficult to simply determine the correction amount because the correction angle with respect to the deviation amount differs depending on the irradiation position.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laser beam deflection control method in a stereolithography system capable of correcting a laser beam irradiation position with high accuracy. To provide.

[0006]

The method for controlling the deflection of the laser beam in the stereolithography system according to the present invention is as follows.
In order to form a desired three-dimensional shape model by stacking a plurality of solidified layers that have been solidified by irradiating a solidifying agent with a laser beam through a deflection means, a laser beam irradiation position on a processed surface by a predetermined method in advance Performing the calibration work of the above, irradiating the laser beam onto the irradiation target immediately before the start of the three-dimensional model formation in that state, measuring the irradiation positions on the irradiation target at multiple points, and acquiring the irradiation position information at the start. During the three-dimensional model forming operation, a step of irradiating the irradiation target with a laser beam and measuring the irradiation positions at multiple points to obtain irradiation position information during model formation, and irradiation position information during start and model formation Difference data acquisition step of obtaining the difference data by comparing the time irradiation position information, and for deflecting the laser beam irradiation position and the laser beam from the difference data Acquisition of irradiation position information during model formation, having a deflection control step of determining a correction angle of the mirror based on the relationship with the rotation angle of the mirror and correcting the deflection control of the laser beam based on this correction angle. One of the scan mirrors in the deflecting means, which is composed of two scan mirrors that sequentially reflects the laser beam in the midway correction operation, is repeated during the model formation, and the midway correction operation including the step, the difference data acquisition step, and the deflection control step It is characterized in that the measurement and correction are performed in the scanning direction by, and then the measurement and correction are performed in the scanning direction by the other scan mirror.

At this time, in the midway correction operation, a relational coefficient between the irradiation position and the rotation amount of the mirror in the deflecting means with respect to the measurement point in the irradiation area of the laser beam is obtained in advance, and correction is performed using the relational coefficient. Good to do.

Further, the execution timing of the intermediate correction operation is determined in advance based on the shape data of the three-dimensional model to be formed, or the integrated irradiation heat quantity of the laser beam is calculated based on the shape data of the three-dimensional model to be formed. It is preferable to calculate in advance and determine the execution timing of the midway correction operation based on the integrated value in advance. Also, based on the shape data of the three-dimensional model to be formed, the irradiation position information during model formation in the midway correction operation. It is also preferable to change the number of irradiation position measurement points with respect to the irradiation target in the acquisition step of.

In addition, when measuring the irradiation position of the laser beam, it is possible to use a camera for measuring the irradiation position, which is installed on a high-precision positioning movable table that can traverse the irradiation region of the laser beam.

Further, as the irradiation target, one which can be positioned on the processing surface is used, and the irradiation target positioned on the processing surface may be irradiated with the laser beam. In this case, It is advisable to position the irradiation target on the machined surface in parallel with the machined surface by means of a movable table capable of precise positioning.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to an example of an embodiment. FIG. 2 shows an example of a stereolithography system including a laser beam deflection control device according to the present invention. In order to move the movable table 4 provided with the squeegee 40 for scraping off the solidified agent on the modeling stage 1, around the modeling stage 1 in which the layer of the solidifying agent is formed on the upper surface and which moves up and down according to the modeling. Drive mechanism 41
And a drive mechanism 51 for moving the movable table 5 equipped with a camera 50 for imaging. Also,
Above the modeling stage 1, a deflection unit 2 for scanning the laser beam output from the laser light source 20 onto the modeling stage 1 is arranged. The deflecting means 2 is composed of a galvano scanner provided with two scan mirrors 21 and 22 which are respectively driven to rotate about two orthogonal axes. Further, between the deflecting means 2 and the laser light source 20, there is provided an adjusting unit 23 having a lens for focus adjustment and change of the focused diameter.

The deflection means 2, the adjusting section 23 and the laser light source 20 are connected to a control computer 9 via a deflection control device 24 for deflection control, focus control and oscillation control, and the movable table 4 is also provided. , 5 are also connected to the control computer 9 so that the control computer 9 controls the squeegeeing operation and the imaging area by the camera 50, and the camera 50 is connected to the control computer 9 via the image processing device 55. Has been done.

In the present invention, the irradiation position of the laser beam is measured by using the camera 50. At this time, the irradiation target 3 provided on the movable table 4 is measured.
Is used to measure. Here, as the irradiation target 3, a roll supply type thermal paper is used.

The irradiation position measurement of the laser beam by the irradiation target 3 and the camera 50 is performed as follows. That is, by driving the movable table 4, the irradiation target 3 is moved onto the modeling stage 1 which is a processing surface, and in this state, a marking pattern (for example, a grid as shown in FIG. 8) that can confirm the positions of a predetermined plurality of points. A pattern) is drawn on the irradiation target 3 by the laser beam. At this time, it is necessary that the predetermined plurality of points are present at a grid-like interval in the laser beam scanning area and have an interval determined by a required scanning area and scanning accuracy (this interval may be obtained by an experiment or the like). Shall be met. Then, after the marking pattern is drawn on the irradiation target 3, the movable table 5 is moved onto the irradiation target 3, and the camera 50 captures an image of the vicinity of the lattice point, and the image processing and the position of the camera 50 at the time of capturing are performed. The position of the lattice point center cc is obtained.

The above-mentioned irradiation position measurement and correction will be described according to the three-dimensional model forming procedure. First, the laser beam irradiation position on the forming stage 1 is calibrated by a predetermined method. Immediately before the start of the formation of the three-dimensional model, the above measurement operation is performed to store the laser beam irradiation position information on a plurality of predetermined measurement points as the start irradiation position information. At this time, each grid-shaped measurement point and its center position are stored in a data format such as measurement point (1, 1) and grid point center position (X, Y) = (XXX, YYY).

When the measurement of the irradiation position of the laser beam with respect to the predetermined measurement point in the initial state is completed in this way,
A layer of the agent to be solidified is formed on the modeling stage 1, a predetermined area of the agent to be solidified is solidified by irradiation with a laser beam to form a solidified layer, and the modeling stage 1 is lowered by one step, and then the solidified layer is coated on the solidified layer. Forming a new layer of the solidifying agent, solidifying a predetermined area of the solidifying agent by irradiation of a laser beam, and providing a solidified layer combined with the lower solidified layer, stacking the solidified layers repeatedly. Then, a desired three-dimensional shape model is formed.

During this period, the irradiation target 3 is moved on the modeling stage 1 at an appropriate timing to perform the laser beam irradiation position measuring operation as described above, and the measurement result is compared with the irradiation position information at the start time. Difference data, that is, data regarding the deviation amount and the deviation direction is obtained. Further, the shift amount and the shift direction at points other than the measurement points are estimated from the difference data for each measurement point.

Then, the correction angles of the mirrors 21 and 22 are determined from the difference data based on the relationship between the laser beam irradiation position and the rotation angle of the laser beam deflection mirror, and the next solidification agent is determined based on this correction angle. The deflection control of the laser beam is corrected when the laser beam is radiated to the laser beam. This correction angle is maintained until the next laser beam irradiation position measuring operation is performed.

Here, in the operation of measuring the laser beam irradiation position and the determination of the correction angle, of the two scan mirrors 21 and 22 which are the deflection means 2, for example, as shown in FIG. The correction angle of the scan mirror 22 is obtained based on the deviation amount in the scan mirror 22, and the laser beam irradiation position measurement operation is performed again with the correction angle for the scan mirror 22 added. Based on this, the correction angle of the scan mirror 21 is obtained. First, the Y coordinate of the scanning system is determined, and then the X coordinate is determined by measuring again in this state. When the distance between the scan mirrors 21 and 22 is e and the distance between the scan mirror 22 and the laser beam irradiation surface is Z, Y, Z,
Since the rotation angle θx of the scan mirror 21 is determined by the value of e, accurate correction can be performed.

By the way, in determining the correction angle based on the shift amount, the rotation angle θ of the scan mirrors 21 and 22.
If the values of Z and e are constant between x and θy and the irradiation positions X and Y,

[0021]

[Equation 1]

Since there is a relation of (2), the correction angle may be calculated based on these two equations.
It can be applied only when the positional relationship between 22 and the laser irradiation surface is ideal, and it is practically difficult to maintain this ideal positional relationship. For this reason, here, with respect to all the measurement points in the laser beam irradiation region, the relation coefficient (conversion coefficient) between the irradiation position and the rotation amount of the scan mirrors 21 and 22 is obtained in advance for each measurement point, and this numerical value is used. It is good to correct it.

At the measurement point (i, j) in the scanning direction X,
When there is a deviation ΔX (i, j), the conversion coefficient Kx (i, j) obtained in advance is multiplied by the deviation ΔX (i, j) to obtain the rotation correction angle Δθx (i at the measurement point (i, j). , J), and similarly the rotation correction angle Δθ for the measurement point (i, j)
As for y (i, j), the conversion coefficient Ky (i, j) obtained by the experiment at the measurement point (i, j) is set to the measurement point (i, j).
It is calculated by multiplying the deviation ΔY (i, j) actually observed at.

As described above, the coefficient of relation (conversion coefficient) Kx (i, j), Ky (i, j) between the amount of deviation (length) and the rotation angle.
The scanner mirror 2
Even if the parallelism and the verticality between the laser irradiation surfaces 1 and 22 are slightly different from each other, appropriate correction can be performed.

It should be noted that the more the number of measurement points, the more accurate the correction can be made. However, the more the measurement points, the more time is required. It is desirable to be able to process in a short time even if it is slightly dropped, and the number of measurement points will be reduced accordingly. Then, when the number of measurement points is reduced in this way, the problem is how to perform the correction corresponding to the amount of positional deviation at a location distant from each measurement point. For all areas within the specified area, the amount of positional deviation and the relation coefficient obtained for a certain measuring point are all applied, or the amount of positional deviation for both measuring points with respect to the intermediate point between two adjacent measuring points. It is possible to use a linear approximation method that applies the intermediate value of and the intermediate value of the relationship coefficient. FIG. 5 shows an example in which the number of measurement points is 9, and the other points (internal points) are corrected by applying the linear approximation method to obtain the positional deviation amount and the conversion coefficient.

By the way, the timing of the laser beam irradiation position measuring operation during the model preparation is based on the outputs of the temperature sensors 25, 25 such as thermocouples attached to the mirrors 21, 22 of the deflection means 2. You can The temperature of the mirrors 21 and 22 is constantly monitored by the temperature sensors 25 and 25, and when the temperature change within a predetermined time exceeds a predetermined value ΔT,
The laser beam irradiation position measuring operation and the irradiation position correcting operation subsequent thereto may be performed when it is determined that the correction is necessary, but the intermediate correcting operation may be performed at a timing determined in advance.

For example, based on the three-dimensional model data,
The total length of the line segment is calculated for each layer of the scanning line data of the laser beam, and when the total length of the line segments for each layer is added, the value becomes almost equal to the predetermined value as the timing of the midway correction operation. Of. As shown in FIG. 6, even when the length and the number of lines (the number of scans) are different due to the different cross-sectional areas,
The midway correction operation can be performed at almost the same irradiation time of the laser beam. FIG. 6 shows the case where there are m line segments of length Li in the section A and the length Lj in the section B.
Shows the case where there are n line segments, and each total extension is

[0028]

[Equation 2]

It becomes

When the power of the laser beam is changed depending on the layer, the integrated irradiation heat quantity of the laser beam is pre-calculated in consideration of the power in addition to the total length of the line segment, and the intermediate correction operation is performed based on the integrated value. The execution timing of may be determined in advance. In FIG. 7, the laser beam powers of the line segments Li1 to Lim are Pi1 to Pim, and the laser beam powers of the line segments Lj1 to Ljn are Pj1 to Pj.
jn and the cumulative irradiation heat amount Ai,
Aj is

[0031]

[Equation 3]

It becomes

In addition, it is not necessary to perform the laser beam irradiation position measuring operation in the midway correction operation in the entire laser beam irradiation possible area, and when the processing area is only a part as shown by the hatched portion in FIG. For the above, it is preferable that the cell C is formed with a square composed of four measurement points as a correction area unit, and measurement and correction are performed with the minimum cell configuration including the processing area.

[0034]

As described above, in the present invention, the midway correction operation including the model formation irradiation position information acquisition step, the difference data acquisition step, and the deflection control step is repeated during model formation, and the midpoint correction is performed. In operation, in the deflecting means composed of two scan mirrors for sequentially reflecting the laser beam, measurement and correction are performed in the scanning direction by one scan mirror, and thereafter, measurement and correction are performed in the scanning direction by the other scan mirror. Even if the optical system is complicated, the measurement and correction can be accurately performed, and the reliability is high.

At this time, in the midway correction operation, a relational coefficient between the irradiation position and the rotation amount of the mirror in the deflecting means with respect to the measurement point in the irradiation area of the laser beam is obtained in advance, and the relational coefficient is used for correction. By performing, it is possible to perform accurate correction.

Further, if the execution timing of the intermediate correction operation is determined in advance based on the shape data of the three-dimensional model to be formed, even if the total extension of the scanning line segment for each layer is different, it is possible for each predetermined layer. Compared to the case where the midway correction operation is performed, the difference in laser beam irradiation time can be eliminated, and the execution timing can be assigned to an appropriate state in advance.

If the integrated irradiation heat quantity of the laser beam is calculated in advance based on the shape data of the three-dimensional model to be formed and the execution timing of the intermediate correction operation is determined in advance based on the integrated value, the laser beam power It is possible to perform the midway correction operation at an appropriate time even when changing the midpoint.

Further, when the number of irradiation position measurement points for the irradiation target at the stage of acquiring irradiation position information during model formation in the mid-correction operation is changed based on the shape data of the three-dimensional model to be formed, the time required for measurement is changed. Can be kept to a necessary minimum, and unnecessary movements can be reduced, so that the speed can be increased as a whole.

In addition, when measuring the irradiation position of the laser beam, if a camera for irradiation position measurement installed on a highly accurate positioning movable table that can traverse the irradiation region of the laser beam is used, it is possible to change the measuring point or the measuring region. Can respond quickly.

If an irradiation target that can be positioned on the processing surface is used and the irradiation target positioned on the processing surface is irradiated with the laser beam, the actual processing area is reduced. Since the measurement point can be brought to the position, accurate correction can be performed, and the size of the target can be set regardless of the irradiation area. Will also be easier.

Further, when the irradiation target is positioned on the machined surface in parallel with the machined surface by the movable table capable of precise positioning, the measurement error can be reduced and the calculation for the correction can be simplified.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a deflection control method according to the present invention.

FIG. 2 is a perspective view of the above apparatus.

FIG. 3 is an explanatory diagram of measurement points of the above.

FIG. 4 is an explanatory diagram of main steps of the above change control method.

FIG. 5 is an explanatory diagram of a deflection control method that includes a process of estimating a positional deviation amount of a portion other than a measurement point.

FIG. 6 is an explanatory diagram regarding execution timing of an intermediate correction operation.

FIG. 7 is an explanatory diagram of another example of the execution timing of the midway correction operation.

FIG. 8 is an explanatory diagram of a processing area and a measurement area.

FIG. 9 is a perspective view of an example of a deflection unit.

FIG. 10 is an operation explanatory diagram of the above.

[Explanation of symbols]

2 Change means 21 scan mirror 22 Scan mirror

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Yoshida 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd. (56) References JP-A-8-318574 (JP, A) JP-A-2000-326416 (JP) , A) JP 2001-96381 (JP, A) JP-A 9-511854 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 67/00

Claims (8)

(57) [Claims] 1. When a desired three-dimensional shape model is formed by stacking a plurality of solidified layers obtained by irradiating a solidifying agent with a laser beam through a deflecting means and solidifying the solidified layers, a surface to be processed is prepared in advance by a predetermined method. The laser beam irradiation position is calibrated, and the laser beam is irradiated onto the irradiation target immediately before the start of the three-dimensional model formation in that state, and the irradiation position on the irradiation target is measured at multiple points. During the operation of forming the three-dimensional model, the step of irradiating the irradiation target with a laser beam, measuring the irradiation positions at multiple points, and acquiring the irradiation position information during model formation, and the irradiation at the start The difference data acquisition step of obtaining the difference data by comparing the position information with the irradiation position information during model formation, and the laser beam irradiation position and the laser beam from the difference data. And a deflection control step for determining the correction angle of the mirror based on the relationship with the rotation angle of the mirror for deflecting the beam and correcting the deflection control of the laser beam based on this correction angle. During the model formation, an intermediate correction operation consisting of a step of acquiring the temporal irradiation position information, a step of acquiring the difference data, and a deflection control step is repeated during the model formation, and a deflection consisting of two scan mirrors for sequentially reflecting the laser beam during the intermediate correction operation. A method of controlling deflection of a laser beam in a stereolithography system, comprising: measuring and correcting in a scanning direction by one of the scan mirrors in the means, and then measuring and correcting in a scanning direction by the other scan mirror. 2. In the midway correction operation, a relational coefficient between the irradiation position and the rotation amount of the mirror in the deflecting means is obtained in advance with respect to a measurement point in the irradiation area of the laser beam, and the relational coefficient is used in the midway correction operation. The method for controlling deflection of a laser beam in a stereolithography system according to claim 1, wherein the correction is performed by the correction. 3. The deflection control of the laser beam in the stereolithography system according to claim 1, wherein the execution timing of the midway correction operation is determined in advance based on the shape data of the three-dimensional model to be formed. Method. 4. The integrated irradiation heat quantity of the laser beam is calculated in advance based on the shape data of the three-dimensional model to be formed, and the execution timing of the midway correction operation is determined in advance based on the integrated value. The method for controlling deflection of a laser beam in the stereolithography system according to claim 1 or 2. 5. The number of irradiation position measurement points for an irradiation target is changed based on the shape data of a three-dimensional model to be formed, in the step of acquiring irradiation position information during model formation in the midway correction operation. Item 1 or 2
A method for controlling deflection of a laser beam in the stereolithography system according to claim 1. 6. A camera for irradiation position measurement, which is installed on a high-precision positioning movable table that can traverse an irradiation region of the laser beam, is used for measuring the irradiation position of the laser beam. 5. A deflection control method of a laser beam in the stereolithography system according to any one of items 5. 7. The irradiation target that can be positioned on the processing surface is used, and the irradiation target positioned on the processing surface is irradiated with a laser beam. 7. A deflection control method of a laser beam in the stereolithography system according to any one of items 6. 8. The deflection control method of a laser beam in an optical modeling system according to claim 7, wherein the irradiation target is positioned on the processing surface in parallel with the processing surface by a movable table capable of precise positioning.