DE102012011418A1 - Stereolithography system - Google Patents

Abstract

The invention relates to a device for producing three-dimensional components by means of stereolithography. The stereolithography system comprising a receiving block (12 for receiving the y-and x-axis movable linear drives (3, 4) as a crossed arrangement and for receiving a construction vessel (1) with integrated, movable in the z-axis construction platform ( 2), wherein the crossed arrangement of the linear drives for the y-axis (3) and for the x-axis (4) are arranged vertically above the building vessel (2) in the vertical direction A laser source (6) is perpendicular to the beam exit directed downwards in the direction of the resin-filled construction vessel (1), via a fastening means (5) on the linear drive for the x-axis (4), and directly on the laser source (6) can be integrated via a holder (9) integrated focusing optics (7 ).

Description

The invention relates to a stereolithography system for the production of three-dimensional components.

The DE 10 2009 009 503 B3 relates to an apparatus and a method for producing a workpiece according to a rapid prototyping method with a laser for generating a laser beam for the curing of a material and a workpiece carrier, which can be directly irradiated by the laser from a predetermined solid angle range. The device consists of a laser for generating a laser beam for the curing of the material and a workpiece carrier which can be directly irradiated by the laser. In addition, the device has an optical device, in particular a mirror, with which the laser beam is deflected, so that the workpiece carrier with the laser is also indirectly irradiated.

In the DE 10 2004 057 527 B4 For example, a method for producing an electrode body for electrochemical machining (ECM) for workpieces is described, wherein the stamp is produced by the stereolithography method. In the rapid prototyping process (RP), the electrode body is built up layer by layer in a liquid plastic bath. For this purpose, the desired cross section of a layer of the electrode body is generated by means of a laser, which is movable both in the horizontal plane and adjustable in height. For this purpose, the laser is moved according to the desired contour in the horizontal plane and exposed by appropriate exposure, a portion of the plastic layer of the liquid plastic and cured.

The invention according to US 2003 001313 A discloses a method and apparatus for making ceramic shaped bodies by sintering selected locations of a ceramic material with a laser beam to form the shaped body. To produce the shaped body, the liquid suspension or plastic mass is applied in layers and the respective layer of the material is sintered with the laser beam at selected locations. In this case, the laser beam is preferably controlled by means of the layered design data. The device for producing ceramic shaped bodies has a support surface, an application unit for applying layers of a ceramic material, a drying unit for the applied layers and a laser unit for generating a laser beam with means for the controlled alignment of the laser beam on selected locations of a respective layer of the ceramic material to sinter the irradiated material and to form the shaped body. The means for controlled alignment of the laser beam are preferably designed as laser scanners, wherein the control of the laser scanner is performed by means of digital design data for the molded part. Thus, a production of a prototype can be done directly from the design data. The laser unit is moved by a robot arm over the surface of the applied layer and the corresponding layer of the shaped article to be produced is imaged on the applied layer.

The US 2002 185 782 (A1) describes a method for producing a three-dimensional object by stereolithography. Solid reinforcing materials are mixed with the liquid medium such that at least a portion of the solid reinforcing agent is disposed in the layer of liquid medium between the upper surface of the last formed layer and the upper surface of the liquid medium. An acoustic field is then generated in the liquid medium such that the acoustic field is present in at least a portion of the layer of liquid medium between the top surface of the last formed layer and the top surface of the liquid medium, thereby curing the liquid medium.

In the US 2004 094 728 A a device for sintering and optionally ablation and / or labeling and for subsequent reworking of the finished workpiece by means of electromagnetic radiation is described. The device consists of a machine housing, in which a space is housed. In the upper area of the installation space, a scanner is arranged, in which the beam of a sintered laser is coupled. In the lower region of the construction space, a height-adjustable workpiece platform and a material supply device are provided, with which powdery or also pasty or liquid sintered material can be transported from a storage container into the process area via the workpiece platform. The scanner is movable in the upper region of the installation space, movable in one axis, arranged on a scanner support bridge moveable over the workpiece platform, wherein the scanner support bridge on two mutually parallel, in a width of the construction vessel corresponding distance from each other, carriers in the second axis runs movable. Motorized drive elements of the scanner carrier are connected to a control computer, which is responsible for the entire process sequence. During the construction process, this control computer controls both the movement of the scanner over the workpiece platform and the movement of the scanner mirror in the housing of the scanner. In addition to a possible displacement of the scanner along the x-axis and the y-axis also a displacement of the scanner along the z-axis is possible, whereby the scanner on the workpiece platform or height-displaceable in adjacent areas. For this purpose, the two mutually parallel carriers run in turn as a bridge to two vertically arranged carrier in the form of linear axes on the right and left wall of the building vessel. The irradiation of the beam of the sintered laser into the area of the scanner carrier takes place parallel to the axes of the suspension of the scanner carrier and via deflection mirrors to the optical input of the scanner.

In addition to the high cost due to the arrangement of the three linear axes in the two-axis mobility or the seven linear axes in the three-axis mobility and the use of four mirrors problems arise in the synchronization of the motors of the linear axes, up to the total failure of stereolithography System.

The invention according to DE 100 53 741 C1 relates to a device for sintering, ablating and / or inscribing by means of electromagnetic bundled radiation, in particular laser sintering machine and / or laser surface processing machine with an accommodated in a machine housing space, in or above which a light guide, in particular by means of a cross slide assembly in all directions movable Scanner, in which the beam is coupled to a sintered energy source, a height-adjustable workpiece platform and a material supply device are arranged with a for supplying sintered material from a reservoir in the process area above the workpiece platform coater, wherein the workpiece platform as a removable element from the space removable is, wherein the height-movable workpiece platform, the reservoir and the coater are formed as a contiguous removable from the space process platform exchange unit and the D urchführung same or other machining processes further process platform changing units of the same or different configurations in the space can be introduced.

The cross slide for the movable in all directions scanner is designed as a movable in the y-direction carrier bridge on which a linear actuator for the z-axis is arranged with a laser scanner. This support bridge runs on two parallel to each other, arranged in a width of the construction vessel corresponding distance from each other, movable in x-axis carriers. The laser beam is guided through a large number of mirrors along the carrier and the carrier bridge and the linear drive for the z-axis to the laser scanner. The parallel arranged carrier and the carrier bridge are designed as linear drives.

As in the invention according to US 2004 094 728 A arise in addition to the high cost of the arrangement of the four linear actuators and the use of five mirrors problem in the synchronization of the motors of the linear drives, which can lead to the total failure of the stereolithography system. Furthermore, this solution requires the use of powerful lasers with high energy and cost to compensate for the loss of energy through the mirrors

In the US 2002 171 178 (A1) The method employs a stereolithography apparatus wherein, by means of a three-dimensional CAD image, chains of one or more photopolymer groups and a photoinitiator form a layered, polymeric polymerizate form prosthetic implant. As a photocurable, bioerodible polymer, the solution of poly (propylene) fumarate (PPF) and a solvent for adjusting the viscosity of the solution will be described. During the manufacturing process, the solution is placed in a container in the stereolithography apparatus (a commercially available SLA 250 stereolithography unit). The container includes a z-axis movable structural panel for supporting each of the covalently bonded layers of the polymeric prosthetic implant exposed to the UV light energy in successive layers of the solution. The UV light energy is generated by means of a commercially available UV laser, wherein the beam of the laser is arranged on the vector-based scanner mirror in the x- and y-axis movable above the container ( www.klartext-pr.de/..../artikel/The culture of prototyping.pdf ).

In the US 45.753.30B1 A system with external laser source, optical beam conditioning (expander, shutter, etc.), laser scanner for beam deflection and F-theta lens for offset compensation of the laser focus is described. The laser beam is guided over two rotating mirrors to reach the entire construction field. If you need a high resolution very exact motors are needed. In addition, the focus must be constantly corrected by the F-theta lens, so that the working distance varies depending on the laser beam / surface angle. An additional disadvantage is that the laser beam penetrates very obliquely into the polymer in the edge region. The scanner, the F-theta lens and the sufficiently powerful beam source are very expensive to buy. Due to the constantly changing angle substrate / laser beam, no teleoptics or replaceable optics can be positioned above the bath.

The in the US 55 95 703 A Apparatus for fabricating an object by stereolithography is of a per se known construction.

This device mainly comprises a container filled with a liquid photopolymerizable prepolymer, a plateau attached therein which can be moved up and down in the liquid prepolymer by a mechanism, not shown, and a laser beam source which is actuated by a mechanism, also not shown can be moved over the surface of the liquid prepolymer according to a specific pattern.

A 2D opto-mechanical laser scanner is a solution in which the laser beam is not controlled by a scanner with rotating mirrors, but by means of several parallel displaceable deflecting mirrors (US Pat. Gandhi, PS et. al. Micromech. Microeng., No 20, pp 1-11, 2010 ). Due to the guidance over right angles, the laser focus can always be positioned vertically above the construction field. The decisive disadvantages are the number of deflection mirrors required. Since the deflecting mirrors are guided dynamically, a high degree of precision is required in each mirror drive and also in the flatness of the mirror. Furthermore, a loss of the laser power of approx. 10% is to be expected on every reflecting surface. Therefore, a powerful beam source is needed here as well. Both factors, precision at several points and laser power, drive up the costs of the system technology.

A further development with regard to the production of several identical components parallel to one another is provided by the design with several parallel-guided glass fibers on an XY plotter. The laser is controlled via shutters and beam guiding optics. A fiber optic bundle then multiplies the beam source and via an XY plotter system the contour is processed line by line or via vectors. The multiplication achieves the construction of several identical components in parallel with normal incidence of the laser radiation. The use of glass fibers to multiply the beam source allows the parallel production of components ( K. Ikuta et. al. "New micro stereo lithography for flexible 3D micro structure", IEEE, pp. 290-295, 1998 ). The processing speed compared to a scanner optics will hardly increase. The components cause the splitting of the laser beam from the beam source (the collimator) as well as the exact uniform distribution of the laser power on the individual fiber strands. If not every fiber delivers identical parameters, the quality / dimensional accuracy of the components suffers. In addition, the use of fibers with UV lasers often leads to an aging process of the fiber. To distribute enough light into all fibers, enough power must be available. Due to the large number of expensive individual components such as laser, collimator, fibers and drive axes for the fibers, the system technology is very cost-intensive.

The Colamm procedure ( Maruo, S. et. al. Sensors and Actuators, vol A 100, pp. 70-76, 2002 ) bypasses the problems of re-coating with a wiper. For this purpose, the resin is exposed through a window at the bottom of the vessel. The component is "glued" to the construction platform and then lifted in layers. It is important here that the cured resin does not adhere to the glass pane. The supply of the laser beam via scanner or glass fiber and there are also in this method, the disadvantages described above.

Other technical solutions for stereolithography offer so-called mask methods. These variants are referred to as surface processing. Here, no laser, but a UV lamp is used. A switchable LCD mask or prefabricated masks can then be used to create the contours for the respective layer in one operation ( Ikuta, K. IEEE, pp. 290-295, 1998 ). This technique can be applied from above (as well as from above) as well as from the Colamm-method ( Schuster, M. et. al. Journal of Polymer Science: Part A: Polymer Chemistry, vol. 47, pp. 7070-7089, 2009 )

Digital Light Processing (DLP) is another modification of stereolithography. The polymerization of the resin takes place here by visible, non-coherent light. The required pattern is imaged directly onto the resin either through micromirrors or through a dynamic LCD mask. The entire layer is cured at the same time. The disadvantage of this method is that the size of the construction field or the number of pixels (pixels) are fixed. The higher the resolution of the structures to be built, the smaller are these structures. Common systems achieve within the x y-plane resolutions of 1 to 5 microns with a layer thickness of 10 microns ( Maier, Ch. Diploma Thesis "Production of Biometric Materials with Rapid-Protoyping-Processes" University of Vienna 2005 ).

Since no laser source is used in these two methods, these methods do not directly affect the invention.

All devices described in the prior art for stereolithography have devices for optical beam conditioning, such as expander and shutter, systems for beam deflection, such as laser scanners, rotating or parallel sliding deflecting mirrors, systems for Offset compensation of the beam, such as F-theta lenses or devices for beam guidance, such as glass fibers, on. Thus, the equipment for stereolithography, especially micro-stereolithography costly and expensive and limit the applications of stereolithography. In addition, high-performance lasers must be used, which in turn are also very expensive due to the losses occurring in the jet preparation.

All known from the prior art solutions for vertically above the building vessel arranged suspensions of laser scanner require a lot of effort because the suspension either in the form of a movable in the z-axis linear drive on a support bridge or directly to this support bridge, which in turn to two parallel is running trained, trained. In addition, these solutions are used to increase the construction field, since the scanner can only irradiate a limited area of the construction field. For this reason, the construction field in these solutions is divided into squares, the scanner is moved after irradiation of a square by means of the cross slide to the next square and irradiated this square of the construction field. Here, the problems described above remain despite over the construction field vertical arrangement of the scanner.

In addition, these solutions can cause significant problems in the synchronization of the motors of the linear axes, especially for longer maturities, which then leads to the failure of stereolithography equipment.

The object of the invention is to provide a new suspension of the radiation source and a much simplified beam shaping and deflection for stereolithography equipment, with significant cost savings by reducing components and sensitive components while increasing the processing options and the -qualification and reliability, even at longer maturities, the stereolithography systems, especially the micro-stereolithography systems are to be achieved.

According to the invention, the object is achieved by a stereolithography system that consists of a recording block ( 12 ) for y-and x-axis movable linear drives ( 3 . 4 ) as a crossed arrangement and for a construction vessel ( 1 ) with an integrated, z-axis movable build platform ( 2 ), wherein the crossed arrangement of the linear drives for the y-axis ( 3 ) and for the x-axis ( 4 ) in the vertical direction vertically above the construction vessel ( 2 ) are arranged. A laser source ( 6 ) is, with the jet exit vertically downwards in the direction of the resin-filled building vessel ( 1 ), via a fastener ( 5 ) on the linear drive for the x-axis ( 4 ), fastened. Directly at the laser source ( 6 ) is the holder with the integrated focusing optics ( 7 ), which emits the emerging laser light ( 8th ) focused directly in the required plane. Thus, the layered structure of the component ( 9 ) either by line by line or vectorial method of the laser head. During the process, the laser hardens the liquid photopolymer. By a practicable arrangement of the electrical connections ( 11 ) of the laser source ( 6 ), the supply can be easily ensured via trailing cable. In a further embodiment of the invention, the focusing optics ( 7 ) as interchangeable focusing optics ( 7 ) be formed. This makes it possible to produce different line widths in the photopolymerization and to optimize the resolution and the processing speed. In the case of a static optics, only one resolution is fixed per job. However, it is also possible to replace this static optics by a motor-driven telescope or by a driven nosepiece and thus dynamically adjust the stroke width of the laser beam while modulating the laser power during the construction process. As a result, the processing speed is greatly increased.

The invention will now be explained in more detail using an exemplary embodiment, wherein the 1 is a schematic representation of the stereolithography system, with

LIST OF REFERENCE NUMBERS

1

Baugefäß

2

building platform

3

Linear drive for the y-axis

4

Linear drive for the x-axis

5

Fixing element for the laser head

6

laser source

7

focusing optics

8th

laser beam

9

component

10

resin

11

electrical connections

12

receiving block

The 1 shows a schematic representation of the essential components for the stereolithography of the invention. Directly above the construction vessel ( 1 ), with the integrated, lowerable building platform ( 2 ), is a linear axis system on a receiving block ( 12 ) made of granite. At the crossed arrangement from the y-axis ( 3 ) and the x-axis ( 4 ) is connected via a suitable fastening element ( 5 ) the laser source ( 6 ) is mounted so that the beam exit of the laser beam is perpendicular to the bottom with the resin ( 10 ) filled construction vessel ( 1 ) shows. As a laser source ( 6 ) a diode laser is used. Directly at the laser source ( 6 ) is the holder with the integrated focusing optics ( 7 ), which blocks the emerging laser light ( 8th ) focused directly in the required plane. Thus, the layered structure of the component ( 9 ) either by linewise or vectorial method of the laser source ( 6 ) respectively. During the process, the laser beam hardens the liquid photopolymer. By a practicable arrangement of the electrical connections ( 11 ) of the laser source, the supply can be easily ensured by trailing cable. Liquid photopolymer is cured by a laser beam in thin layers with a standard layer thickness in the range 0.05-0.25 mm, in micro stereolithography also up to 1 μm. The process takes place in the construction vessel ( 1 ) which is filled with the photopolymer, in this example with epoxy resin. In the construction vessel ( 1 ), the z-axis movable construction platform ( 2 ) in the epoxy resin by the construction platform ( 2 ) dipped in the z-axis, then moved up to the amount of layer thickness in the z-axis up and applied with a wiper, the epoxy resin. After applying the epoxy resin, the laser source ( 6 ) by means of the x and y axes ( 4 . 3 ) over the build platform ( 2 ) and cured the epoxy resin by the laser beam. The laser source ( 6 ) is moved line by line over the construction site and modulated position-dependent via its digital input.

After each step, the workpiece is lowered a few millimeters into the liquid and returned to a position which is lower than the previous one by the amount of a layer thickness. The epoxy over the component is then evenly distributed by a wiper. Then the laser source ( 6 ) by means of the crossed arrangement of the x and y axes ( 4 . 3 ), controlled by a computer, on the new layer over the surfaces that are to be cured. After curing, the next step takes place so that gradually a three-dimensional part is created.

In the stereolithography process, support structures are typically also included in the fabrication because the laser-cured resin is still relatively soft and certain features (eg, overhangs) are to be securely fixed during the build process. After the construction process, the build platform ( 2 ) with the part (s) of the construction vessel ( 1 ) moved out. After the non-cured resin drips, the model is removed from the build platform, stripped of support structures, washed with solvents, and fully cured in a cabinet under UV light.

In the stereolithography system according to the invention, the laser source ( 6 ) and the focusing optics ( 7 ) directly over the construction vessel ( 1 ) and so over the entire construction field by means of linear axes, the beam exit and thus the laser beam always remains vertically above the building vessel. Compared to laser-based stereolithography systems described in the prior art, the system according to the invention does not require deflecting mirrors, glass fibers or similar beam-influencing components. The stereolithography system according to the invention is thus significantly simpler with otherwise the same performance and requires laser sources with significantly low performance (diode laser). This creates a significant cost advantage over all previous laser-based stereolithography systems. Furthermore, there are no problems in the synchronization of the motors for the linear drives and the susceptibility of the stereolithography system is significantly reduced by the use of only two linear actuators, which are still moved independently.

Further advantages of the stereolithography system according to the invention can be seen in the lower losses of the laser power in the optical system due to component reduction and the always vertical arrangement of the laser source and the vertical exit of the laser beam relative to the construction vessel. The vertical angle of incidence of the laser radiation avoids the usual laser scanner procedure exposure with a non-perpendicular angle of incidence in the edge region of the construction field and thus ensures a consistently high manufacturing precision over the entire construction field. Furthermore, there are no signs of aging in the case of functional components (eg optical fibers) and the system has a high level of serviceability since an exchanged laser does not have to be adjusted into the optical system.

The stereolithography system is further characterized by low energy consumption and associated lower operating costs.

The system according to the invention can likewise be used in laser sintering and in laser cutting and labeling by means of laser sources.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009009503 B3 [0002]
• DE 102004057527 B4 [0003]
• US 2003001313 A [0004]
• US 2002185782 A1 [0005]
• US 2004094728 A [0006, 0010]
• DE 10053741 C1 [0008]
• US 2002171178 A1 [0011]
• US 4575330 B1 [0012]
• US 5595703 A [0013]

Cited non-patent literature

• www.klartext-pr.de/..../artikel/The culture of prototyping.pdf [0011]
• Gandhi, PS et. al. Micromech. Microeng., No. 20, pp 1-11, 2010 [0015]
• K. Ikuta et. al. "New micro stereo lithography for flexible 3D micro structure", IEEE, pp. 290-295, 1998 [0016]
• Maruo, S. et. al. Sensors and Actuators, vol A 100, pp. 70-76, 2002 [0017]
• Ikuta, K. IEEE, pp. 290-295, 1998 [0018]
• Schuster, M. et. al. Journal of Polymer Science: Part A: Polymer Chemistry, vol. 47, pp. 7070-7089, 2009 [0018]
• Maier, Ch. Diploma Thesis "Production of Biometric Materials with Rapid-Protoyping-Processes" University of Vienna 2005 [0019]

Claims (7)

Stereolithography system consisting of a recording block ( 12 ) for the reception of the y-and x-axis movable linear drives ( 3 . 4 ) as a crossed arrangement and for receiving a construction vessel ( 1 ) with an integrated, z-axis movable build platform ( 2 ), wherein the crossed arrangement of the linear drives for the y-axis ( 3 ) and for the x-axis ( 4 ) in the vertical direction vertically above the construction vessel ( 2 ), characterized in that a laser source ( 6 ), with the jet exit vertically downwards in the direction of the resin-filled construction vessel ( 1 ) and via a fastener ( 5 ) on the linear drive for the x-axis ( 4 ), is attached. Stereolithography system according to claim 1, characterized in that at the laser source ( 6 ) a focusing optics ( 7 ) is integrated. Stereolithography system according to claim 2, characterized in that the focusing optics ( 7 ) is designed interchangeable. Stereolithography system according to claim 2 and 3, characterized in that the focusing optics ( 7 ) is designed as a static optics. Stereolithography system according to claim 2 to 4, characterized in that the focusing optics ( 7 ) is designed as a driven nosepiece. Stereolithography system according to claim 1 to 5, characterized in that the laser source ( 6 ) is electrically supplied via trailing cable. Stereolithography system according to claim 1, characterized in that as a laser source ( 6 ) a diode laser is used.

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