阅读说明：本技术 立体光刻设备和用于调设立体光刻设备的方法 (Stereolithography apparatus and method for adjusting a stereolithography apparatus ) 是由 M·韦特斯登 S·盖斯布尔勒 于 2020-02-26 设计创作，主要内容包括：本发明涉及一种立体光刻设备(100),所述立体光刻设备包括：光源(101),所述光源用于发出用于固化光固化材料(121)的光；传感器(103),所述传感器用于确定所发出的光的光强度的实际值；和控制单元(105),所述控制单元用于适配通过所述光源(101)的电流,直至所述光强度的实际值达到预给定的额定值为止。(The invention relates to a stereolithography apparatus (100), comprising: a light source (101) for emitting light for curing a photo-curable material (121); a sensor (103) for determining an actual value of the light intensity of the emitted light; and a control unit (105) for adapting the current through the light source (101) until the actual value of the light intensity reaches a predefined setpoint value.)

1. Stereolithography apparatus (100), comprising:

a light source (101) for emitting light for curing a photo-curable material (121);

a sensor (103) for determining an actual value of the light intensity of the emitted light; and

a control unit (105) for adapting the current through the light source (101) until the actual value of the light intensity reaches a predefined setpoint value.

2. The stereolithography apparatus (100) according to claim 1, wherein said stereolithography apparatus (100) is configured for steering light from said light source (101) to said sensor (103) via a digital micro-mirror device (113) for projecting a light pattern (123) onto said light-curable material (121).

3. The stereolithography apparatus (100) according to claim 2, wherein said digital micromirror device (113) is arranged adjacent to the prism face.

4. The stereolithography apparatus (100) according to claim 2 or 3, wherein said stereolithography apparatus (100) is configured for projecting a predefined light pattern onto said sensor (103) by means of said digital micro-mirror device (113).

5. The stereolithography apparatus (100) according to any of the preceding claims, wherein said stereolithography apparatus (100) comprises a mirror (109) for diverting light onto said sensor (103).

6. The stereolithography apparatus (100) according to claim 5, wherein said mirror (109) is arranged adjacent to a prism stop (117).

7. The stereolithography apparatus (100) according to any of the preceding claims, wherein said sensor (103) is particularly configured for detecting a spectrum used in said stereolithography apparatus.

8. The stereolithography apparatus (100) according to claim 7, wherein said sensor (103) is constituted by a photodiode.

9. The stereolithography apparatus (100) according to any of the preceding claims, wherein said control unit (105) comprises a regulator (119) for regulating the current through said light source (101).

10. Method for adjusting a setup photolithography device (100), the method having the steps of:

-emitting (S101) light for curing the photo-curable material (121) by means of a light source (101);

-determining (S102) an actual value of the light intensity of the emitted light; and is

-adapting (S103) the current through the light source (101) until the actual value of the light intensity reaches a predefined nominal value.

11. The method of claim 10, wherein light is diverted from the light source (101) by a digital micro-mirror device (113) to a sensor (103) for projecting a light pattern (123) onto the light curable material (121).

12. The method according to claim 10 or 11, wherein a predetermined light pattern is projected onto the sensor (103) by means of said digital micro-mirror device (113).

13. The method according to any one of claims 10 to 12, wherein the light is diverted onto the sensor (103) via a mirror (109).

14. The method according to any one of claims 10 to 13, wherein the current is regulated to a nominal value by a regulator (119).

15. The method according to any one of claims 10 to 14, wherein the light is directed through a prism diaphragm (117).

Technical Field

The present invention relates to a stereolithography apparatus and a method for setting up a stereolithography apparatus.

Background

Stereolithography (SLA) is a three-dimensional printing method in which a liquid bath made of photopolymer builds up the workpiece step by step or the workpiece is manufactured in the liquid bath by means of a build platform. First, the build platform is introduced into a bath and after the formation of the distinct layers, the build platform is withdrawn from the bath. The build platform is then introduced into the bath again until the desired object is manufactured. A light pattern is projected onto the photopolymer in each step. At the locations where the light pattern impinges on the photopolymer, the photopolymer cures. In this way, the workpiece can be produced in the desired form layer by layer.

The uv light source (e.g. LED) of a stereolithography apparatus suffers from aging effects over the required lifetime, so that the light intensity is reduced with a constant current. Other components in the light path, such as prisms, lenses, mixing rods and electron micromirror devices, show degradation effects by high illumination with ultraviolet light, which show reduced radiation intensity on the build area. However, it is very important for the quality of the construction process: the light intensity remains constant over the lifetime of the stereolithography apparatus.

Document EP18190700.7 relates to a method for building shaped bodies layer by stereolithographically curing photopolymerizable material in successive layers by means of exposure by an exposure unit.

The problem is hitherto ignored or solved with aging compensation, wherein the exposure time and/or the current intensity of the light source with a fixed storage characteristic is adapted for this duration. However, the stored characteristics do not take into account sample variations of the components used. The control of the light intensity and the unpredictable aging behavior of the remaining light path via the aging characteristics of the light source is therefore inaccurate.

Disclosure of Invention

Therefore, the technical object of the present invention is to: the light intensity in the stereolithography apparatus is maintained over a lifetime with high accuracy.

This object is achieved by the content of independent claim 1. Advantageous embodiments are the subject matter of the dependent claims, the description and the figures.

According to a first aspect, the object is achieved by a stereolithography apparatus having: a light source for emitting light for curing a photo-curable material; a sensor for determining an actual value of the light intensity of the emitted light; and a control unit for adapting the current through the light source until the actual value of the light intensity reaches a predetermined target value. Since the sensor has no aging phenomena, the light intensity can be set precisely to a predefined target value of the light intensity by means of a closed control loop (closed loop). Thus, aging phenomena by means of gases released when plastic parts are irradiated or heated, general environmental influences or deposits during the production of the remaining components (such as prisms, lenses, light-mixing rods and digital micromirror devices) can also be compensated within the light path. A temporally constant light intensity and an improved lifetime of the stereolithography apparatus are achieved.

In a technically advantageous embodiment of the stereolithography apparatus, the stereolithography apparatus is configured for diverting light from the light source to the sensor via a digital micro-mirror device for projecting a light pattern onto the light-curable material. This results in technical advantages, for example: if necessary, the light can be diverted into the coupling-out light path and the service life of the sensor can be increased.

In another technically advantageous embodiment of the stereolithography apparatus, the digital micromirror device is arranged adjacent to the prism face. This results in technical advantages, for example: the structural form of the stereolithography apparatus can be reduced.

In a further technically advantageous embodiment of the stereolithography apparatus, the stereolithography apparatus is configured to project a predefined light pattern onto the sensor by means of the digital micromirror device. This results in technical advantages, for example: the amount of light on the sensor can be accurately metered.

In another technically advantageous embodiment of the stereolithography apparatus, the stereolithography apparatus comprises a mirror for diverting light onto the sensor. This results in technical advantages, for example: the sensors can be flexibly arranged at different positions in the interior of the stereolithography apparatus.

In a further technically advantageous embodiment of the stereolithography apparatus, the mirror is arranged adjacent to the prism diaphragm. This results in technical advantages, for example: the prism diaphragm defines a predetermined exit opening and reduces undesired scattered light.

In a further technically advantageous embodiment of the stereolithography apparatus, the sensor is configured in particular for detecting ultraviolet light. This results in technical advantages, for example: a high service life of the sensor is achieved.

In another technically advantageous embodiment of the stereolithography apparatus, the sensor is formed by a photodiode. This results in technical advantages, for example: the sensor is inexpensive and at the same time has little aging phenomena.

In another technically advantageous embodiment of the stereolithography apparatus, the control unit comprises a regulator, for example a PID regulator or a PI regulator, for regulating the current through the light source. This results in technical advantages, for example: a fast and efficient regulation of the regulating circuit is carried out.

According to a second aspect, the object is achieved by a method for setting up a stereolithography apparatus, having the steps of: emitting light for curing the light-curable material by means of a light source; determining an actual value of the light intensity of the emitted light; and adapting the current through the light source until the actual value of the light intensity reaches a predefined setpoint value. The same technical advantages are obtained by the method as by the stereolithography apparatus according to the first aspect.

In a technically advantageous embodiment of the method, light is diverted from the light source to the sensor by means of a digital micromirror device for projecting a light pattern onto the light-curable material. This also results in technical advantages, for example: if necessary, the light can be diverted into the coupling-out light path and the service life of the sensor can be increased.

In a technically advantageous embodiment of the method, a predefined light pattern is projected onto the sensor by the digital micromirror device. This also results in technical advantages, for example: light impinging on the sensor can be metered.

In a technically advantageous embodiment of the method, the light is deflected onto the sensor via a mirror. This also results in technical advantages, for example: the sensors can be flexibly arranged at different positions in the interior of the stereolithography apparatus.

In a technically advantageous embodiment of the method, the current is regulated to the target value by a regulator, for example a PID regulator. This also results in technical advantages, for example: a fast and efficient regulation of the regulating circuit is carried out.

In a technically advantageous embodiment of the method, the light is guided through a prism diaphragm. This also results in technical advantages, for example: the diaphragm defines a predefined exit opening and the determination of the actual value is carried out in a similar manner in the different measurements.

Drawings

Embodiments of the invention are illustrated in the drawings and are described in detail below.

In the drawings:

FIG. 1 shows a schematic view of a stereolithography apparatus; and is

Fig. 2 shows a block diagram of a method for setting up a stereolithography apparatus.

Detailed Description

Fig. 1 shows a schematic view of a stereolithography apparatus 100. The stereolithography apparatus 100 is used for manufacturing a workpiece by means of a three-dimensional printing method (3D printing). For this purpose, the workpiece is in a layer-by-layer liquid bath made of a photocurable material, for example a photopolymer. In each step, a specific light pattern 123 is projected onto the light curable material 121. At the location where the light pattern 123 impinges on the light curable material, the light curable material cures and becomes solid. In this way the workpiece can be manufactured layer by layer in the desired form.

The stereolithography apparatus 100 comprises a light source 101, such as an ultraviolet light LED (UV-LED), for generating light for curing a material. Furthermore, the stereolithography apparatus 100 comprises a closed control loop (closed loop), with which the light intensity is measured and compensation of the light intensity is carried out with the aid of the measurement data obtained. In this way, a closed control loop can be realized, which allows a precise setting of the light intensity over the entire service life of the stereolithography apparatus 100 by means of preset setpoint values and which can be compensated for by aging effects of the optical components. In addition, the resistance of the light-emitting diode can be measured by means of the temperature sensor and the current supply can be adapted accordingly, so that the service life of the light-emitting diode is additionally increased. If, for example, the measured temperature increases, the resistance of the light-emitting diode decreases. In which case too high a current will flow through the light emitting diode.

For this purpose, the light emitted by the light source 101 is diverted onto the coupling-out light path 107, for example by means of a Digital Micromirror Device (DMD) 113. The digital micromirror device 113 comprises a plurality of micromirror actuators arranged in a matrix, which can be manipulated individually by means of voltages and can be flipped. Thus, each individual micro-mirror actuator of the micro-mirror actuators can turn light onto the sensor 103 that is directed in the direction of the light curable material 121 or in the direction of the out-coupling optical path 107. In this way, a light pattern 123 may be created that solidifies the light curable material 121.

All light or only certain light patterns can thereby be transferred to the sensor 103. During the correction process, the light is coupled out only for a certain predefined time duration, so that the sensor 103 is exposed to illumination only during this time period. The correction process can be carried out, for example, after each layer (sheet) during a construction process, after a predetermined number of layers (iterations), after each component or after each maintenance process or repair.

The coupled-out light is directed onto the sensor 103 via the reflecting mirror 109 at the holding-down device 115 of the prism diaphragm 117. The prism diaphragm 117 defines a planar predefined exit opening on the surface of the prism 111, so that the coupling-out light path 107 is delimited laterally and thus reduces unwanted scattered light. The light is diverted onto the sensor 103 by the mirror 109 so that the sensor can be arranged directly above the prism 111. Thereby, the sensor 103 can also be arranged at a location inside the stereolithography apparatus 100 that is not in the initial propagation direction of the out-coupling optical path 107.

The sensor 103 is designed such that it is particularly suitable for light used in stereolithography methods and does not deteriorate the measurement over the service life. For this purpose, the sensor 103 is formed, for example, by a photodiode. However, other sensors 103 may also be used in general.

The measurement unreliability is compensated for by the fact that during the measurement the actual value of the measured light intensity is introduced as a reference variable, for example, into a PID controller (proportional integral derivative controller) 119, which is provided in the control unit 105. The PID controller is a combination of a proportional controller (P controller), an integral controller (I controller), and a differential controller (D controller).

The proportional regulator multiplies the regulation deviation by its amplification factor. The integral regulator sums the regulation deviation over time and multiplies the sum (i.e., the integral) by a coefficient. The differential adjuster weights (differentiates) the change in the adjustment deviation and thus calculates its speed of change. The PID control loop enables precise and rapid current setting of a predetermined setpoint value. However, other regulators may also be used for regulating the light intensity in general.

The nominal values are stored as digitized values in a non-volatile data memory 125, such as a flash memory, specific to the stereolithography apparatus 100 when it is manufactured. The actual value of the light intensity can likewise be detected digitally and compared with the stored setpoint value. Depending on the deviation between the actual value and the setpoint value, the current through the light source 101 can be increased or decreased until the actual value of the light intensity is equal to the stored setpoint value. The adaptation of the current value can be performed, for example, via pulse width modulation or amplitude modulation.

The light intensity is thus regulated to the desired target value by means of current regulation for the light source 101 by means of an electronic PID regulator or PI regulator 119. In this way, the aging compensation and correction process can be carried out quickly and efficiently via the PID controller 119. However, in general, other adjustment mechanisms with a closed loop can also adjust the light intensity of the stereolithography apparatus 100 to a predefined setpoint value.

During the measurement, the PID controller 119 controls the light intensity of the light source 101 until it reaches a predefined setpoint value. This nominal value is used as a reference value and is determined, for example, during production at the start of a correction of the stereolithography apparatus 100. The value of the current necessary to reach the nominal value is returned by the control unit 105 to the stereolithography apparatus 100 and used as a new reference value for the current.

Fig. 2 shows a block diagram of a method for setting up the stereolithography apparatus 100. Light for curing the photo-curing material 121 is emitted by means of the light source 101 in step S101. Next, the actual value of the light intensity of the emitted light is determined by the sensor 103 in step S102. In step S103, the current through the light source 101 is increased and decreased for such a long time until the actual value of the light intensity reaches a predefined target value. By which the light intensity for curing the photo-curing material 121 can be set to a desired magnitude accurately and constantly in time. Since the sensor 103 is subject to only a small degradation due to aging, the light intensity can be adjusted to a predetermined value with high accuracy.

All the features which are described and illustrated in connection with the individual embodiments of the invention can be provided in the solution according to the invention in different combinations in order to achieve their advantageous effects at the same time.

All method steps may be performed by a device adapted for performing the respective method step. All functions performed by a particular feature may be a method step of a method.

The scope of protection of the invention is given by the claims and is not limited by the features set forth in the description or shown in the drawings.

List of reference numerals

100 stereolithography apparatus

101 light source

103 sensor

105 control unit

107 coupled-out optical path

109 mirror

111 prism

113 Digital Micromirror Device/Digital Micromirror Device

115 pressing device

117 prism diaphragm

119 PID regulator

121 photo-curable material

123 light pattern

125 data memory