WO2014207751A2 - Method and device for selective laser sintering (sls) rapid prototype - Google Patents

Method and device for selective laser sintering (sls) rapid prototype Download PDF

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Publication number
WO2014207751A2
WO2014207751A2 PCT/IN2013/000392 IN2013000392W WO2014207751A2 WO 2014207751 A2 WO2014207751 A2 WO 2014207751A2 IN 2013000392 W IN2013000392 W IN 2013000392W WO 2014207751 A2 WO2014207751 A2 WO 2014207751A2
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Prior art keywords
rapid prototyping
selective laser
laser sintering
mirror
axis
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PCT/IN2013/000392
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French (fr)
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WO2014207751A3 (en
Inventor
Bala Anand JELDI
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Jeldi Bala Anand
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Priority to PCT/IN2013/000392 priority Critical patent/WO2014207751A2/en
Publication of WO2014207751A2 publication Critical patent/WO2014207751A2/en
Publication of WO2014207751A3 publication Critical patent/WO2014207751A3/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10—Processes of additive manufacturing
    • B29C64/141—Processes of additive manufacturing using only solid materials
    • B29C64/153—Processes of additive manufacturing using only solid materials using layers of powder being selectively joined, e.g. by selective laser sintering or melting

Definitions

  • the present invention relates to selective laser sintering (SLS).
  • SLS selective laser sintering
  • the present invention discloses a selective laser sintering (SLS) rapid prototyping device for producing prototype of larger size at faster rate.
  • Selective laser sintering is a method that uses a high power laser (e.g. a carbon dioxide laser, nd yag laser, fiber laser etc..) to fuse small particles of plastic, resin coated ceramics/silica, particles, metal (direct metal laser sintering), ceramic, or glass powders into a desired 3- dimensional prototype.
  • a high power laser e.g. a carbon dioxide laser, nd yag laser, fiber laser etc..
  • Rapid Prototyping is intended to mean a method for rapidly producing prototype components from design data. Typical rapid prototyping methods are stereo lithography (STL or STA) and selective laser sintering (SLS).
  • Stereo lithography is a method in which a prototype is built Up layer-by- layer by materializing points. The fabrication of a part or a plurality of parts is typically carried out fully automatically from computer-generated CAD data.
  • Selective laser sintering is a method in which geometrical prototype are produced from a sintering of powder form material. It is likewise a generative layer by layer construction method.
  • the physical process can be full melting, partial melting, or liquid-phase sintering. Depending on the form of material, up to 100% density can be achieved with material properties comparable to those from conventional manufacturing methods. In many cases large numbers of parts can be packed within the powder bed which allowing very high productivity by this method.
  • the SLS does not require support structures due to the fact that the part being constructed is surrounded by unsintered powder at all times.
  • thermoplastics in particular e.g. polycarbonates, polyamides, polyvinyl chloride.
  • the conventional method for manufacturing large prototype proposes a technique whereby the entire three-dimensional prototype data obtained by scanning the reference object which is simply divided into data segments reflecting parts of the object. These parts of the object then prototyped separately and the complete prototype is created by assembling the parts.
  • the conventional SLS device has biggest field size is 500 X 500 square millimeters.
  • the conventional SLS device use 'F-theta' lens as a correction lens.
  • the f-theta lens is placed before the laser beam post scanner that provides bigger circular or near circular laser spot to the maximum extends of 500 X 500 square millimeter field size.
  • For making 3d objects of bigger size multiple laser beams are used in which each laser beam coming from a device sinters only an assigned portion of the mold.
  • the prototypes beyond the 500 X 500 square millimeters are made in parts that increase the time and cost to make the prototype.
  • the conventional method use two or more laser sources to make larger field size than possible field size.
  • the prototype is divided into number of parts and then each part is sintered by a SLS device individually and finally the parts are joined to give the shape to the complete prototype
  • the principle object of this invention is to provide the invention of a precise and efficient method and device for manufacturing three-dimensional objects.
  • Another object of this invention is to manufacture 3-dimensional objects in a bigger size than the conventional prototype machine size limit.
  • Yet another object of this invention is manufacturing the 3d objects at faster rate than the conventional prototype manufacturing methods-
  • Yet another object of this invention is that the device has overcome the problem of the drift in mirror orientation.
  • Yet another object of this invention is that the device can manufacture bigger 3d objects using a single laser source.
  • the present invention makes the 3d objects of any size ranging between 10 X 10 square millimeters to 5000 X 5000 square millimeters by dynamic beam expender component, where as in the conventional method the ranging size of the 3d object maximum size upto 500 X 500 square millimeters by using the 'F-theta' lens.
  • the present invention produce prototype by faster and precise sintering which is achieved by using mirrors made of Beryllium material. .
  • the Beryllium mirrors increase the angular velocity ( ⁇ ) that irv effect increases the number of layers sintered in a specific time period.
  • the Beryllium mirrors helps in building larger aperture scanner for maintaining the circular laser beam spot of the consistent size for broader field area.
  • the other feature of the disclosed device is that the mirror system of the invented device has mechanical water based cooling system.
  • the present invention particularly advantageous as the problem of drift is control by the using correcting sensor.
  • the present invention possessed of Beryllium mirrors, water based cooling system and field correction sensors for every layer to be sintered.
  • the field correction sensor gives the values of position and temperature of mirror to the controller.
  • the controller in turn gives instructions to the motor to auto correct the position of the mirrors.
  • the present disclosed SLS device does selective laser sintering at a faster rate with higher precision and can make bigger 3d objects using a single laser source compare to the conventional SLS device.
  • FIGS. 1 illustrate the method of the present invention for rapid prototyping by SLS
  • FIGS. 2 illustrate a method of prototyping by conventional SLS
  • FIGS. 3 is summary illustrations of a process for prototyping by using F theta lens
  • FIGS. 4 illustrate a method of prototyping by Dynamic Beam Expander
  • FIGS. 5 depicts a side view of an embodiment of Dynamic Beam Expander
  • FIG. 1 A preferred embodiment of an apparatus for performing SLS is illustrated in FIG. 1.
  • the apparatus comprises a computerized controlled laser 1 , Static beam expander 2 consisting of lens 3, Mirror 4, Dynamic beam expander 5, Motor 6, Sensors 7, x- axis galvo with mirror & y- axis galvo with mirror 8, Scanner 9, Powder laying hopper 10, Field(x-y) 11, Powder collector tray 12, z- axis motor 13, Controller 14.
  • controller (14) which is regulated and organize all components of the apparatus. Controller (14) regulates the motors (6), sensors (7) and laser source (1).
  • the computerized controlled laser beam (1) passes through the static beam expander (2).
  • This static beam expander contains the lenses (3) for expansion of the laser beam. After the expansion of this beam the beam oriented through the mirrors (4), and enters in the dynamic beam expander (5) and then this laser beam fall on the surface of the field (11), after passes through the x- axis mirror mounted on galvo motor and y- axis mirror mounted on galvo motor (8) the laser beam get orientation.
  • These mirrors move with the help of galvo motors (6), these motors are galvo motors which drive with angular sensors (7) and the 2 axis movement is control by the Z axis motor (13).
  • the laser beam fall on the field (x, y) (1 ) sinter the power which is collected in the powder collector tray (12) which is leveling by powder laying hopper (10) and form the 3d object by sintering.
  • FIGS. 2 there is shown the method used in the conventional SLS process.
  • the laser beam (1) enters in the mirror (8) and by the orientation through the mirrors (8) it falls on the field (11).
  • laser beam (1) touches the field at Point 'C is the distance away from center radially.
  • the beam form the parabolic curve as the beam deflects from the center.
  • the parabolic curve which has drawn is a constant spot size curve which laser beam will form when a constant beam is falling on a X Y mirror.
  • parabolic surface (15) the center of the field touches the surface and other surface is on air.
  • the laser spot remains circular at the center of the field and gradually becomes elliptical as the laser spot moves away from the center.
  • the elliptical spot also grows with the distance from the center therefore the power density of the laser spot is much lower away from the parabolic surface (15) and therefore it is not possible to sintering the flat field (16).
  • FIGS. 3 there is shown the method used in the SLS process with overcoming the problem shows in fig 2.
  • the laser beam (1) enters in mirrors (8). After the orientation through the mirrors (8) and before it falls on the field (11) the laser passed through the (17) F theta lens>
  • the (17) F theta lens is a field correction lens, this field correction lens make the parabolic surface (15) to a flat field and exchange the constant spot size of the beam across the field.
  • the F theta lens (17) is introduce after the XY mirrors (8) to make the spot fall on the flat field other than in the air.
  • laser beam (1) touches the field at Point 'C Even by introducing the field correction lens F theta, the size limit of the 3d object is limited up to 500 X 500 square millimeters.
  • FIGS. 4 there is shown the method of present invention for the rapid prototyping by SLS, Where the teser beam (1) introduced in the dynamic beam expansion (5) and then guided by the X-axis scanning galvo mirror and Y-axis scanning galvo mirror (8). Where the one mirror is vertical mirror and another is horizontal mirror. These mirrors are set as one is horizontal and other is perpendicular to it. The movements of the mirrors are control with the help of motors (6). This motors are galvo motors, they drive it with an angular sensors (7). Mirror x and y orient the spot of the beam and also control the direction of the beam. The beam layer goes on increase as it moves away from the center, the diameter of the beam slightly expand to make the spot constant again the field to make the spot fall on the flat field other than forming the parabolic surface (15).
  • FIG 5 depicjs a dynamic beam expander (5) which consist a set of 2 lenses, one is called objective lens (18) and other is called expander lens (19).
  • objective lens (18) is fixed and expander lens (19) can dynamically move, the movement of the expanders lens is like the spot move away from the center of the field then it move to the certain extend to expand beam as the beam expand and fall then it is corrected automatically,
  • the bottleneck in the heretofore known SLS devices is overcome by the disclosed invention with the help of a dynamic beam expander (5) that dynamically does focus correction.
  • the dynamic beam expender holds three-axis head similar to two-axis scan head with the dynamic focus lens and objective lens in z-axis.
  • the x, y mirrors orient the beam away from the center in the way that the beam spot remain consistently on the field and accordingly dynamic beam expand. Thus without divergence the beam consistently and precisely form the flat field instead of the parabolic field.
  • the f-theta lens provides the desired results up to the field size of 5Q0X 500 square millimeters.
  • the dynamic beam expander breaks this field boundary size by extending the laser sintering field size to 5000 X 5000 square millimeters.
  • the focal diameter of the spot is directly proportion to the wave length of the laser, focal length of the x, y scan system, quality of the laser beam and inversely proportion to the diameter of the laser beam prior to focusing with respect to the correction factor. This is explaining with the equation as;
  • F focal length of the x, y scan system
  • the mirrors are made of material Beryllium (Be).
  • the Beryllium material has specific gravity of 1.85 that makes it 45% lighter to the Aluminum (Al) that is used as a medium for making mirrors.
  • the specific heat of Be is 1925 J/Kg that is 50% higher to Al.
  • Beryllium holds properties to be a natural heat sink and provides stable dimensions in Beryllium mirrors for higher temperature operations.
  • Beryllium mirrors are used in the device.
  • the Beryllium mirrors increase the angular velocity ⁇ that in effect increases the number of layers sintered in a specific time period.
  • the Beryllium mirrors helps in building larger aperture scanner for maintaining the circular laser beam spot of the consistent size for broader field area.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Powder Metallurgy (AREA)

Abstract

Method And Device for rapid prototyping by selective laser sintering where the computerized controlled Co2 laser beam passes through the static beam expander. The expanded beam oriented through the mirrors and enters in the dynamic beam expander. This laser beam fall on the surface of the field, after passes through the x- axis mirror mounted on galvo motor and y- axis mirror mounted on galvo motor. The beam layeY goes on increase as it moves away from the center, the diameter of the beam slightly expand to make the spot constant again the field to make the spot fall on the flat field other than forming the parabolic surface. The laser beam fall on the field (x, y) sinter the power which is collected in the powder collector tray and form the scanning cross-sections generated from a 3-D digital description object by sintering.

Description

TITLE
METHOD AND DEVICE FOR SELECTIVE LASER SINTERING (SLS) RAPID PROTOTYPE
DESCRIPTION:
1. Field of invention:
The present invention relates to selective laser sintering (SLS). In particular the present invention discloses a selective laser sintering (SLS) rapid prototyping device for producing prototype of larger size at faster rate.
Selective laser sintering (SLS) is a method that uses a high power laser (e.g. a carbon dioxide laser, nd yag laser, fiber laser etc..) to fuse small particles of plastic, resin coated ceramics/silica, particles, metal (direct metal laser sintering), ceramic, or glass powders into a desired 3- dimensional prototype.
The term "Rapid Prototyping" is intended to mean a method for rapidly producing prototype components from design data. Typical rapid prototyping methods are stereo lithography (STL or STA) and selective laser sintering (SLS).
Stereo lithography is a method in which a prototype is built Up layer-by- layer by materializing points. The fabrication of a part or a plurality of parts is typically carried out fully automatically from computer-generated CAD data. 2. Background of the invention
Selective laser sintering is a method in which geometrical prototype are produced from a sintering of powder form material. It is likewise a generative layer by layer construction method.
The physical process can be full melting, partial melting, or liquid-phase sintering. Depending on the form of material, up to 100% density can be achieved with material properties comparable to those from conventional manufacturing methods. In many cases large numbers of parts can be packed within the powder bed which allowing very high productivity by this method.
Unlike some other additive manufacturing processes, such as stereo lithography (SLA) and fused deposition modeling (FDM), the SLS does not require support structures due to the fact that the part being constructed is surrounded by unsintered powder at all times.
SLS technique even manufacture prototype which cannot be produced by conventional casting techniques like thermoplastics in particular e.g. polycarbonates, polyamides, polyvinyl chloride.
The conventional method for manufacturing large prototype proposes a technique whereby the entire three-dimensional prototype data obtained by scanning the reference object which is simply divided into data segments reflecting parts of the object. These parts of the object then prototyped separately and the complete prototype is created by assembling the parts.
The conventional SLS device has biggest field size is 500 X 500 square millimeters. The conventional SLS device use 'F-theta' lens as a correction lens. The f-theta lens is placed before the laser beam post scanner that provides bigger circular or near circular laser spot to the maximum extends of 500 X 500 square millimeter field size. For making 3d objects of bigger size multiple laser beams are used in which each laser beam coming from a device sinters only an assigned portion of the mold. The prototypes beyond the 500 X 500 square millimeters are made in parts that increase the time and cost to make the prototype.
The conventional method use two or more laser sources to make larger field size than possible field size. The prototype is divided into number of parts and then each part is sintered by a SLS device individually and finally the parts are joined to give the shape to the complete prototype
The bigger the size of the field, the longer the duration of scanner mirrors exposure to the laser beam. This makes the scanner mirrors hot that gives drift in mirror orientation. The drift badly affects the positioning accuracy of the mirrors. Therefore the making of bigger size 3d objects is beyond the limits of conventional SLS device.
In conventional SLS device contain mirrors and the mirror size is directly proportional to the field size. Therefore the increase in the size of the mirror, the weight of the mirror also increases. The heavy weight mirrors adversely affects the operation of the beam steering. This further affects the accuracy of the laser beam spot which results low quality prototype.
Hence to meet this challenge and overcoming these significant drawbacks there is provide the invention of a precise and efficient method and device for manufacturing large three-dimensional objects 3. Object of the invention:
The principle object of this invention is to provide the invention of a precise and efficient method and device for manufacturing three-dimensional objects.
Another object of this invention is to manufacture 3-dimensional objects in a bigger size than the conventional prototype machine size limit.
Yet another object of this invention is manufacturing the 3d objects at faster rate than the conventional prototype manufacturing methods-
Yet another object of this invention is that the device has overcome the problem of the drift in mirror orientation.
Yet another object of this invention is that the device can manufacture bigger 3d objects using a single laser source.
4. Summary of the Invention
The above problems arid insufficiency can be eliminated in the present invention which provides an improved method and device for manufacturing three-dimensionaf prototypes.
Accordingly, it is therefore a primary object of the present invention to provide a method and device of SLS rapid prototype having improved process of manufacturing prototype with novel features that help in overcoming bottleneck in the heretofore devices used for the prototype arid the method thereof. The present invention makes the 3d objects of any size ranging between 10 X 10 square millimeters to 5000 X 5000 square millimeters by dynamic beam expender component, where as in the conventional method the ranging size of the 3d object maximum size upto 500 X 500 square millimeters by using the 'F-theta' lens.
The present invention produce prototype by faster and precise sintering which is achieved by using mirrors made of Beryllium material. . The Beryllium mirrors increase the angular velocity (ω) that irv effect increases the number of layers sintered in a specific time period. The Beryllium mirrors helps in building larger aperture scanner for maintaining the circular laser beam spot of the consistent size for broader field area.
The other feature of the disclosed device is that the mirror system of the invented device has mechanical water based cooling system.
Another bottleneck in the heretofore known SLS devices is of drifting. The drift problem increases with the field area size and is a serious problem in making 3d objects. The laser expose to the mirrors for longer duration increases with the field area that gives drift in mirror orientation. This adversely affects the position accuracy of the mirrors. The heat developed because of longer exposure of laser radiation on mirrors leads to deviation in dimensionality of the mirrors.
The present invention particularly advantageous as the problem of drift is control by the using correcting sensor. The present invention possessed of Beryllium mirrors, water based cooling system and field correction sensors for every layer to be sintered. The field correction sensor gives the values of position and temperature of mirror to the controller. The controller in turn gives instructions to the motor to auto correct the position of the mirrors. These three measures solve the drifting problem in larger size fields
The present disclosed SLS device does selective laser sintering at a faster rate with higher precision and can make bigger 3d objects using a single laser source compare to the conventional SLS device.
5. A brief description of the accompanying drawing
The invention will now be described, with reference to the accompanying drawings in which:
FIGS. 1 illustrate the method of the present invention for rapid prototyping by SLS
FIGS. 2 illustrate a method of prototyping by conventional SLS
FIGS. 3 is summary illustrations of a process for prototyping by using F theta lens
FIGS. 4 illustrate a method of prototyping by Dynamic Beam Expander
FIGS. 5 depicts a side view of an embodiment of Dynamic Beam Expander
6. Detailed description of the invention with reference to drawing
This invention is illustrated in the accompanying drawing throughout which like reference letters indicate corresponding parts in the various figures. The invention is illustrated now be described with respect of the non- limiting figures in the accompanying drawing in hich the computer controlled laser selectively fuses powdered material by scanning cross- sections generated from a 3-D digital description of the part (for example from a CAD file or scan data) on ihe surface of a powder bed. After each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied on top, and the process is repeated until the 3 D Object is completely formed.
A preferred embodiment of an apparatus for performing SLS is illustrated in FIG. 1. The apparatus comprises a computerized controlled laser 1 , Static beam expander 2 consisting of lens 3, Mirror 4, Dynamic beam expander 5, Motor 6, Sensors 7, x- axis galvo with mirror & y- axis galvo with mirror 8, Scanner 9, Powder laying hopper 10, Field(x-y) 11, Powder collector tray 12, z- axis motor 13, Controller 14.
The fabrication of a part or a plurality of parts is typically carried out fully automatically from computer-generated CAD data. This data commanded the controller (14) which is regulated and organize all components of the apparatus. Controller (14) regulates the motors (6), sensors (7) and laser source (1).
The computerized controlled laser beam (1) passes through the static beam expander (2). This static beam expander contains the lenses (3) for expansion of the laser beam. After the expansion of this beam the beam oriented through the mirrors (4), and enters in the dynamic beam expander (5) and then this laser beam fall on the surface of the field (11), after passes through the x- axis mirror mounted on galvo motor and y- axis mirror mounted on galvo motor (8) the laser beam get orientation. These mirrors move with the help of galvo motors (6), these motors are galvo motors which drive with angular sensors (7) and the 2 axis movement is control by the Z axis motor (13). The laser beam fall on the field (x, y) (1 ) sinter the power which is collected in the powder collector tray (12) which is leveling by powder laying hopper (10) and form the 3d object by sintering.
Referring to FIGS. 2, there is shown the method used in the conventional SLS process. Where the laser beam (1) enters in the mirror (8) and by the orientation through the mirrors (8) it falls on the field (11). Then laser beam (1) touches the field at Point 'C is the distance away from center radially. The beam form the parabolic curve as the beam deflects from the center. The parabolic curve which has drawn is a constant spot size curve which laser beam will form when a constant beam is falling on a X Y mirror. And it does not create a flat field, it called parabolic surface (15), the center of the field touches the surface and other surface is on air. The laser spot remains circular at the center of the field and gradually becomes elliptical as the laser spot moves away from the center. The elliptical spot also grows with the distance from the center therefore the power density of the laser spot is much lower away from the parabolic surface (15) and therefore it is not possible to sintering the flat field (16).
Referring first to FIGS. 3, there is shown the method used in the SLS process with overcoming the problem shows in fig 2. Where the laser beam (1) enters in mirrors (8). After the orientation through the mirrors (8) and before it falls on the field (11) the laser passed through the (17) F theta lens> The (17) F theta lens is a field correction lens, this field correction lens make the parabolic surface (15) to a flat field and exchange the constant spot size of the beam across the field. The F theta lens (17) is introduce after the XY mirrors (8) to make the spot fall on the flat field other than in the air. Then laser beam (1) touches the field at Point 'C Even by introducing the field correction lens F theta, the size limit of the 3d object is limited up to 500 X 500 square millimeters.
Referring first to FIGS. 4, there is shown the method of present invention for the rapid prototyping by SLS, Where the teser beam (1) introduced in the dynamic beam expansion (5) and then guided by the X-axis scanning galvo mirror and Y-axis scanning galvo mirror (8). Where the one mirror is vertical mirror and another is horizontal mirror. These mirrors are set as one is horizontal and other is perpendicular to it. The movements of the mirrors are control with the help of motors (6). This motors are galvo motors, they drive it with an angular sensors (7). Mirror x and y orient the spot of the beam and also control the direction of the beam. The beam layer goes on increase as it moves away from the center, the diameter of the beam slightly expand to make the spot constant again the field to make the spot fall on the flat field other than forming the parabolic surface (15).
FIG 5 depicjs a dynamic beam expander (5) which consist a set of 2 lenses, one is called objective lens (18) and other is called expander lens (19). objective lens (18) is fixed and expander lens (19) can dynamically move, the movement of the expanders lens is like the spot move away from the center of the field then it move to the certain extend to expand beam as the beam expand and fall then it is corrected automatically,
To make the beam converge to a defined place with a consistent laser beam spot size all over the field the input diameter of the laser beam has to be slightly increased with respect to the distance C from center of the field. The bottleneck in the heretofore known SLS devices is overcome by the disclosed invention with the help of a dynamic beam expander (5) that dynamically does focus correction. The dynamic beam expender holds three-axis head similar to two-axis scan head with the dynamic focus lens and objective lens in z-axis.
The x, y mirrors orient the beam away from the center in the way that the beam spot remain consistently on the field and accordingly dynamic beam expand. Thus without divergence the beam consistently and precisely form the flat field instead of the parabolic field.
The f-theta lens provides the desired results up to the field size of 5Q0X 500 square millimeters.
The dynamic beam expander breaks this field boundary size by extending the laser sintering field size to 5000 X 5000 square millimeters.
The precise and consistent laser beam spot can be achieved without making the adjustment in the input beam diameter. The same has been shown in figure (4). This is explaining with the equation as; dp = P/A (1)
Where dp = power density of laser at a spot
P = laser power,
Figure imgf000011_0001
Where A- area of spot
d = diameter of spot
D = f (B(x, y) C) (2) Where, D = Working distance between center of the beam and field B(x, y)= Position of the spot at (x, y)
C = diameter input beam with respect to position of the spot on x, y field
The focal diameter of the spot is directly proportion to the wave length of the laser, focal length of the x, y scan system, quality of the laser beam and inversely proportion to the diameter of the laser beam prior to focusing with respect to the correction factor. This is explaining with the equation as;
Fs=A x F x 2 x C/D (3)
Where, Fs=focal diameter of the spot
A-wave length of the laser
F=focal length of the x, y scan system
M2=quality of the laser beam
C=correction factor
D=diameter of the laser beam prior to focusing
As the size of the mirrors increases the weight of the mirrors also increases that reduce the speed to operate the laser beam steering. Therefore; ω = ί(Μ) (4)
Where, ω = angular velocity
M * mass of mirror
M= f (B(x,y), s) (5)
Where M = mass of mirror
B(x, y)- Position of the spot at (x, y)
s= Geometric size of mirror The equations (4) & (5) explain that heavier the mirror mass, the slower the angular velocity to position the mirror at a precise position; therefore the equations indicate that it is desirable to make mirrors lighter in weight for achieving the higher precision in laser positioning.
In the invented device, the mirrors are made of material Beryllium (Be). The Beryllium material has specific gravity of 1.85 that makes it 45% lighter to the Aluminum (Al) that is used as a medium for making mirrors. The specific heat of Be is 1925 J/Kg that is 50% higher to Al. Beryllium with thermal conductivity of 216 W/mk and thermal expansion co-efficient Of 6.3 micfon/m-k, holds physical and thermal properties better to Aluminum as a better medium to build mirrors. Beryllium holds properties to be a natural heat sink and provides stable dimensions in Beryllium mirrors for higher temperature operations.
In the preferred embodiment Beryllium mirrors are used in the device. The Beryllium mirrors increase the angular velocity ω that in effect increases the number of layers sintered in a specific time period. The Beryllium mirrors helps in building larger aperture scanner for maintaining the circular laser beam spot of the consistent size for broader field area.

Claims

Claim,
1. Method And Device For Rapid Prototyping By Selective Laser Sintering comprising a computerized controlled laser source; Static beam expander consisting of lens; Mirror configured to orient the beam, Dynamic beam expander configured to x- axis galvo motor with mirror & y- axis galvo motor with mirror to make the beam spot constant again the field and make the spot fall on the flat field other than forming the parabolic surface; Powder collector tray consisting of powder laying hopper, z- axis motor configured to powder tray; Controller configured to regulates the function of device. Control station for inputting the 3D CAD in *.STL file format.
2. Device for Rapid Prototyping by Selective Laser Sintering of claim
1 wherein said computer controlled laser source selectively fuses powdered form materials (metals, polymers, polymer coated particles, ceramics).
3. Device for Rapid Prototyping by Selective Laser Sintering of claim
2 wherein computer controlled laser source fuse powder material to cross Section of sliced 3D CAD data of the part on the surface of a powder bed. Device for Rapid Prototyping by Selective Laser Sintering of claim 1 wherein Static beam expander consisting of lenses for expansion of the laser beam diameter which is circular in cross-section.
Device for Rapid Prototyping by Selective Laser Sintering of claim 1 wherein expanded Static beam oriented through the mirror made of copper or molybdenum.
Device for Rapid Prototyping by Selective Laser Sintering of claim 1 wherein Dynamic beam expander consist a set of 2 lenses.
Device for Rapid Prototyping by Selective Laser Sintering of claim 6 wherein one fixed lens is objective lens and other is dynamically moving expander lens.
Device for Rapid Prototyping by Selective Laser Sintering of claim 6 wherein the dynamic beam expender holds three-axis head similar to two-axis scan head with the dynamic focus lens and objective lens in z-axis.
Device for Rapid Prototyping by Selective Laser Sintering of claim 1 wherein x- axis mirror mounted on galvo motor and y- axis mirror mounted on galvo motor moves in X & Y - Axis to orient beam on the flat field.
10. Device for Rapid Prototyping by Selective Laser Sintering of claim 9 mirrors are set as one is horizontal and other is perpendicular to it.
11. Device for Rapid Prototyping by Selective Laser Sintering of claim 9 wherein including auto drift correction sensors configured along with angular sensors to provide precise angular movement.
12. Device for Rapid Prototyping by Selective Laser Sintering of claim 1 wherein mirrors of x- axis mirror mounted on galvo motor and y- axis mirror mounted on galvo motor are made of material Beryllium.
13. Device for Rapid Prototyping by Selective Laser Sintering of claim 1 wherein powder collector tray which consist of powder laying hopper for leveling & laying powder and form field for sintering the layer.
14. Device for Rapid Prototyping by Selective Laser Sintering of claim 1 wherein and the Z axis movement of powder bed is control by the Z axis motor.
15. Device for Rapid Prototyping by Selective Laser Sintering of claim 1 wherein Controller regulates the motors, sensors and laser source.
16. Method For Rapid Prototyping By Selective Laser Sintering comprising the steps of; a) Computer controlled laser beam introduced in the dynamic beam expansion and then guided by the X-axis scanning mirror and Y-axis scanning galvo mirror. b) Mirror x and y orient the spot of the beam and also control the direction of the beam. The one mirror is vertical mirror and another is horizontal mirror. These mirrors are set as one is horizontal and other is perpendicular to it. c) The beam layer goes on increase as it moves away from the center, the diameter of the beam slightly expand to make the spot constant over the field to make the spot constant fall on the flat field other than forming the parabolic surface. d) Laser Beam fuse powder material to cross section scanned 3D digital description of the part on the surface of a powder bed in laminates. e) The laser source, scan system with auto drift correction sensors are water cooled to maintain and regulate all heating parts at a very precise temperature of operations which helps to avoid drift and maintain consistency in 3d part manufacturing process.
17. Method for Rapid Prototyping by Selective Laser Sintering of claim 16 wherein each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied on top of powder collector tray which consist of powder laying hopper for leveling powder and the process is repeated until the 3 D Object is completely formed.
18. Method and Device for Rapid Prototyping by Selective Laser Sintering substantially as herein described and exemplified with reference to accompanying drawing.
PCT/IN2013/000392 2013-06-26 2013-06-26 Method and device for selective laser sintering (sls) rapid prototype WO2014207751A2 (en)

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FR3041278A1 (en) * 2015-09-23 2017-03-24 Manutech-Usd SYSTEM AND METHOD FOR ADDITIVE FABRICATION BY LASER FUSION OF A BED OF POWDER
WO2020148580A1 (en) * 2019-01-18 2020-07-23 Alcon Inc. Controlling the position of the focal point of a laser beam
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US4863538A (en) * 1986-10-17 1989-09-05 Board Of Regents, The University Of Texas System Method and apparatus for producing parts by selective sintering
US6391251B1 (en) * 1999-07-07 2002-05-21 Optomec Design Company Forming structures from CAD solid models
JP5293993B2 (en) * 2008-01-09 2013-09-18 ソニー株式会社 Stereolithography apparatus and stereolithography method
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FR3041278A1 (en) * 2015-09-23 2017-03-24 Manutech-Usd SYSTEM AND METHOD FOR ADDITIVE FABRICATION BY LASER FUSION OF A BED OF POWDER
WO2017051123A1 (en) * 2015-09-23 2017-03-30 Manutech-Usd System and method for additively manufacturing by laser melting of a powder bed
US11045907B2 (en) 2015-09-23 2021-06-29 Manutech-Usd System and method for additively manufacturing by laser melting of a powder bed
WO2020148580A1 (en) * 2019-01-18 2020-07-23 Alcon Inc. Controlling the position of the focal point of a laser beam
US11166851B2 (en) 2019-01-18 2021-11-09 Alcon Inc. Controlling the position of the focal point of a laser beam
CN113900459A (en) * 2021-10-28 2022-01-07 南京机电职业技术学院 High power light-gathering flash burning device
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