Abstract:
A system for manufacturing a tool within a laser sintering system includes a chamber enclosing a sinter material. The laser sintering system grows or sinters a section of the tool from the sinter material in response to signals from a controller. The controller generates the signals as a function of a predetermined tool design. The predetermined tool design includes defining a slot in the section of the tool, wherein the slot receives a weld-nut after sintering is complete for strengthening a portion of the section of the tool.

Description:
FEDERAL RESEARCH STATEMENT  
       [0001]     [Federal Research Statement Paragraph]This invention was made with government support on contract N00019-01-C-0012. The Government has certain rights in this invention. 
     
    
     BACKGROUND OF INVENTION  
       [0002]     The present invention relates generally to tooling systems and processes and is more specifically related to the fabrication of tools through selective laser sintering.  
         [0003]     Traditional fabrication methods for tools having areas of contour have included fiberglass lay-ups on numerically controlled machined master models or facility details.  
         [0004]     A manufacturing master model tool, or “master model”, is a three-dimensional representation of a part or assembly. The master model controls physical features and shapes during the manufacture or “build” of assembly tools, thereby ensuring that parts and assemblies created using the master model fit together.  
         [0005]     Traditional tool fabrication methods rely on a physical master model. These master models may be made from many different materials including: steel, aluminum, plaster, clay, and composites; and the selection of a specific material has been application dependent. Master models are usually hand-made and require skilled craftsmen to accurately capture the design intent. Once the master model exists, it may be used to duplicate tools.  
         [0006]     The master model becomes the master definition for the contours and edges of a part pattern that the master model represents. The engineering and tool model definitions of those features become reference only.  
         [0007]     Root cause analysis of issues within tool families associated with the master has required tool removal from production for tool fabrication coordination with the master. Tools must also be removed from production for master model coordination when repairing or replacing tool details. Further, the master must be stored and maintained for the life of the tool.  
         [0008]     Master models are costly in that they require design, modeling and surfacing, programming, machine time, hand work, secondary fabrication operations, and inspection prior to use in tool fabrication.  
         [0009]     In summary, although used for years, physical master models have inherent inefficiencies, including: they are costly and difficult to create, use, and maintain; there is a constant risk of damage or loss of the master model; and large master models are difficult and costly to store.  
         [0010]     By way of further background, the field of rapid prototyping of parts has, in recent years, made significant improvements in providing high strength, high density parts for use in the design and pilot production of many useful objects. “Rapid prototyping” generally refers to the manufacture of objects directly from computer-aided-design (CAD) databases in an automated fashion, rather than from conventional machining of prototype objects following engineering drawings. As a result, time required to produce prototype parts from engineering designs has been reduced from several weeks to a matter of a few hours.  
         [0011]     An example of a rapid prototyping technology is the selective laser sintering process (SLS) in which objects are fabricated from a laser-fusible powder. According to this process, a thin layer of powder is dispensed and then fused, melted, or sintered, by a laser beam directed to those portions of the powder corresponding to a cross-section of the object.  
         [0012]     Conventional selective laser sintering systems position the laser beam by way of galvanometer-driven mirrors that deflect the laser beam. The deflection of the laser beam is controlled, in combination with modulation of the laser itself, for directing laser energy to those locations of the fusible powder layer corresponding to the cross-section of the object to be formed in that layer. The laser may be scanned across the powder in a raster fashion or a vector fashion.  
         [0013]     In a number of applications, cross-sections of objects are formed in a powder layer by fusing powder along the outline of the cross-section in vector fashion either before or after a raster scan that fills the area within the vector-drawn outline. After the selective fusing of powder in a given layer, an additional layer of powder is then dispensed and the process repeated, with fused portions of later layers fusing to fused portions of previous layers (as appropriate for the object), until the object is completed.  
         [0014]     Selective laser sintering has enabled the direct manufacture of three-dimensional objects of high resolution and dimensional accuracy from a variety of materials including polystyrene, NYLON, other plastics, and composite materials, such as polymer coated metals and ceramics. In addition, selective laser sintering may be used for the direct fabrication of molds from a CAD database representation of the object in the fabricated molds. Selective Laser Sintering has, however, not been generally applicable for tool manufacture because of SLS part size limitations, lack if robustness of SLS objects, and inherent limitations in the SLS process.  
         [0015]     Further, the SLS material typically does not have sufficient strength or durability to support threaded features. A traditional tooling solution includes adding a metal threaded insert; however, this adds unwanted secondary fabrication operations beyond the primary SLS fabrication and will not prevent stripping of threads in high torque applications.  
         [0016]     The disadvantages associated with current tool manufacturing systems have made it apparent that a new and improved tooling system is needed. The new tooling system should reduce need for master models and should reduce time requirements and costs associated with tool manufacture. The new system should also apply SLS technology to tooling applications and strengthen SLS material such that bolts may couple sections of SLS tools together with minimal thread stripping. The present invention is directed to these ends.  
       SUMMARY OF INVENTION  
       [0017]     In accordance with one aspect of the present invention, a system for manufacturing a tool within a laser sintering system includes a chamber enclosing a sinter material. The laser sintering system grows or sinters a section of the tool from the sinter material in response to signals from a controller. The controller generates the signals as a function of a predetermined tool design. The predetermined tool design includes defining a slot in the section of the tool, wherein the slot receives a weld-nut after sintering is complete for strengthening a portion of the section of the tool.  
         [0018]     In accordance with another aspect of the present invention, a method for laser sintering a tool includes predetermining a position of a contoured detail feature. The method further includes predetermining a configuration for the contoured detail feature such that the contoured detail feature includes securing features for coupling strengthening components thereto. The contoured detail is sintered, and a strengthening component is coupled thereto, thereby reducing stress on the contoured detail feature.  
         [0019]     One advantage of the present invention is that use of Selective Laser Sintering can significantly reduce costs and cycle time associated with the tool fabrication process. An additional advantage is that tool features can be “grown” as represented by the three-dimensional computer model, thus eliminating the requirement for a master model or facility detail. The subsequent maintenance or storage of the master/facility is thereby also eliminated.  
         [0020]     Still another advantage of the present invention is that the model remains the master definition of the tool, therefore root cause analysis or detail replacement may be done directly from the model definition. Secondary fabrication operations are further eliminated where features are “grown” per the three-dimensional solid model definition.  
         [0021]     Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0022]     In order that the invention may be well understood, there will now be described some embodiments thereof, given by way of example, reference being made to the accompanying drawings, in which:  
         [0023]      FIG. 1  illustrates a sintering system in accordance with one embodiment of the present invention;  
         [0024]      FIG. 2  illustrates a perspective view of a tool, fabricated in the system of  FIG. 1 , in accordance with another embodiment of the present invention;  
         [0025]      FIG. 3  illustrates an enlarged partial view of  FIG. 2 ;  
         [0026]      FIG. 4  illustrates a cutaway view of a section of the tool of  FIG. 2 , looking in the direction of  4 - 4 , in accordance with another embodiment of the present invention;  
         [0027]      FIG. 5  illustrates the cutaway view of  FIG. 4  including a weld-nut accordance with another embodiment of the present invention;  
         [0028]      FIG. 6  illustrates the cutaway view of  FIG. 5  including a threaded feature and coupling features in accordance with another embodiment of the present invention; and  
         [0029]      FIG. 7  illustrates a logic flow diagram of a method for operating a sintering system in accordance with another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0030]     The present invention is illustrated with respect to a sintering system particularly suited to the aerospace field. The present invention is, however, applicable to various other uses that may require tooling or parts manufacture, as will be understood by one skilled in the art.  
         [0031]      FIG. 1  illustrates a selective laser sintering system  100  having a chamber  102  (the front doors and top of chamber  102  not shown in  FIG. 1 , for purposes of clarity). The chamber  102  maintains the appropriate temperature and atmospheric composition (typically an inert atmosphere such as nitrogen) for the fabrication of a tool section  104 . The system  100  typically operates in response to signals from a controller  105  controlling, for example, motors  106  and  108 , pistons  114  and  107 , roller  118 , laser  120 , and mirrors  124 , all of which are discussed below. The controller  105  is typically controlled by a computer  125  or processor running, for example, a computer-aided design program (CAD) defining a cross-section of the tool section  102 .  
         [0032]     The system  100  is further adjusted and controlled through various control features, such as the addition of heat sinks  126 , optimal objection orientations, and feature placements, which are detailed herein.  
         [0033]     The chamber  102  encloses a powder sinter material that is delivered therein through a powder delivery system. The powder delivery system in system  100  includes feed piston  114 , controlled by motor  106 , moving upwardly and lifting a volume of powder into the chamber  102 . Two powder feed and collection pistons  114  may be provided on either side of part piston  107 , for purposes of efficient and flexible powder delivery. Part piston  107  is controlled by motor  108  for moving downwardly below the floor of chamber  102  (part cylinder or part chamber) by small amounts, for example 0.125 mm, thereby defining the thickness of each layer of powder undergoing processing.  
         [0034]     The roller  118  is a counter-rotating roller that translates powder from feed piston  114  to target surface  115 . Target surface  115 , for purposes of the description herein, refers to the top surface of heat-fusible powder (including portions previously sintered, if present) disposed above part piston  107 ; the sintered and unsintered powder disposed on part piston  107  and enclosed by the chamber  102  will be referred to herein as the part bed  117 . Another known powder delivery system feeds powder from above part piston  107 , in front of a delivery apparatus such as a roller or scraper.  
         [0035]     In the selective laser sintering system  100  of  FIG. 1 , a laser beam is generated by the laser  120 , and aimed at target surface  115  by way of a scanning system  122 , generally including galvanometer-driven mirrors  124  deflecting the laser beam  126 . The deflection of the laser beam  126  is controlled, in combination with modulation of laser  120 , for directing laser energy to those locations of the fusible powder layer corresponding to the cross-section of the tool section  104  formed in that layer. The scanning system  122  may scan the laser beam across the powder in a raster-scan or vector-scan fashion. Alternately, cross-sections of tool sections  104  are also formed in a powder layer by scanning the laser beam  126  in a vector fashion along the outline of the cross-section in combination with a raster scan that “fills” the area within the vector-drawn outline.  
         [0036]     Referring to  FIGS. 1, 2 , and  3 , a sample tool  150  formed through the SLS system  100  is illustrated. The tool  150  includes a plurality of large sections (first  152 , second  154 , and third  156 ) or alternately one large section. The sections  152  (alternate embodiment of  104  in  FIG. 1 ),  154 ,  156  may be sintered simultaneously or consecutively.  
         [0037]     During the sintering process, various features are molded into the large tool section or sections. Such features include steps and thickness variations  158 , gussets  160 , stiffeners  162 , interfaces and coordination features for making interfaces  164 , construction ball interfaces and coordination holes  170 , trim of pocket and drill inserts  166 , hole patterns  172 , and holes  168  included in multiple details for interfacing hardware, such as detail  180 . Important to note is that a first plurality of features, including a combination of the aforementioned features, may be sintered into the first section  152  and a second plurality of features, including a combination of the aforementioned features, may be sintered into the second section  154 .  
         [0038]     Individually contoured details, such as detail  180 , which may also be considered sections of the tool for the purposes of the present invention, may be sintered separately from the main body of the tool  150 , such that they may be easily replaced or replaceable or easily redesigned and incorporated in the tool  150 . Alternate embodiments include a plurality of individual contoured details, such as  180 ,  182 ,  184 , and  186 . Each of the contoured details includes holes, e.g.  168 , such that a bolt  190  may bolt the detail  180  to a section  152 ,  154 , or  156  of the tool  150 . The contoured details  180  further define holes or openings  198  strengthened by bushings  200 . The openings  198  reduce friction acting on and strengthen the contoured detail  180  such that other tools, tool components, or devices may be coupled thereto. The contoured detail  180  and the bushings  200  will be discussed further regarding  FIGS. 4, 5 , and  6 .  
         [0039]     The features, such as the gusset  160  and the stiffener  162  are, in one embodiment of the present invention, grown on the same side of the SLS tool  150 . Growing (i.e. sintering) these features on the same side of the tool takes advantage of the sintering process because a feature grown at the beginning of a sintering operation has different properties than the same feature would when grown at the end of a sintering operation. Therefore, the first side  200  undergoing sintering includes all the tool features.  
         [0040]     Alternate embodiments of the present invention include various tool features grown on either side of the tool  150  through various other methods developed in accordance with the present invention. One such method includes adding a heat sink  202 , or a plurality of heat sinks  202 ,  204 ,  206  to various portions of the bed  117  such that different tool features may be cooled subsequent to sintering on the first section  152  or second section  154 , thereby avoiding warping that is otherwise inherent in the sintering process. Alternately, a single large heat sink may be placed on one side such that all features cool at the same rate and immediately following the sintering operation.  
         [0041]     A further aspect of the present invention includes separating contoured details and various tool aspects by a proximate amount such that warping between the features is limited and structural integrity of the features is maximized.  
         [0042]     An alternate embodiment of the present invention includes designing in access features or buffer features  179  in areas where warping will occur during sintering such that these features may be removed when the sintering process is concluded. These buffer features  179  may be predetermined such that connection between them and the main body of the part facilitates detachment through a twisting off or breaking off procedure for the buffer feature  179 .  
         [0043]      FIGS. 4, 5 , and  6  illustrate a partial cutaway view of a section  152  of the tool  150  of  FIG. 2 , looking in the direction of  4 - 4 , in accordance with another embodiment of the present invention.  FIG. 4  illustrates a cutaway view of the section  152  of  FIG. 3  looking in the direction of  4 - 4 . The section  152  defines a bolt hole  230  for receiving a bolt, a slot  232 , and a retaining detent  234 .  FIG. 5  illustrates a weld-nut  236  (strengthening feature) inserted in the slot  232  and secured by the retaining detent  234 .  FIG. 6  illustrates the contoured detail  180  coupled to the section  152  through a bolt  190  secured through the hole  230  and bolted to the weld-nut  236 .  
         [0044]     The bolt hole  230  is defined in the section  152 , such that a bolt  190  extending there through intersects the slot  232 . The bolt hole  230  may extend fully through the slot  232  or alternately partially through the slot  232  provided the bolt hole extends at least through a ceiling portion  233  of the slot  232 .  
         [0045]     The slot  232  is defined in the sintered section  152  such that the slot  232  includes a base portion  238 , a ceiling portion  233  and a common sidewall  240  and defines a receiving area  242 , i.e. slot parameters. The bolt hole  230  may extend through both the base portion  238  and the ceiling portion  233 .  
         [0046]     The retaining detent  234  is defined in the receiving area  242  coupled to the base portion  238 ; however, the retaining detent may be coupled to any area within the slot  232 . The retaining detent  234  is embodied as a ramp, such that the weld nut  236  may be received in the slot  232  by sliding the weld nut  236  over the retaining detent  234 , which may recede into the base portion  238 . The retaining detent  234  my recede through a spring mechanism or other mechanical mechanisms know in the art. The detent  234  springs outwardly to its initial position following the sliding of the weld nut  236  over the retaining detent. The weld nut  236  is then securely held between the retaining detent  234  and the slot parameters. The weld nut  236  may be removed through a disengaging operation including depressing of the retaining detent  234  with a screwdriver or through other mechanical means know in the art. The retaining detent  234  may include a notch  250  such that a screwdriver or depressing device may catch on the notch  250  to depress the retaining detent.  
         [0047]     Referring to  FIG. 7 , logic flow diagram  300  of the method for operating a SLS system is illustrated. Logic starts in operation block  302  where the size of the tool needed is predetermined and attachments required to generate that size of tool are also predetermined. In other words, if the tool requires several sections due to the limitations of the part cylinder  102 , the tool is manufactured in a plurality of parts that are joined together through predetermined connectors that are sintered into the sections within the parts cylinder  102 .  
         [0048]     In operation block  304 , the features, such as thickness variations  158 , gussets  160 , stiffeners  162 , interfaces and coordination features  164 , construction ball interface and coordination holes  170 , trim of pockets and drill inserts  166  and holes  168  provided in details for interface hardware, such as screws, are all predetermined for the tool.  
         [0049]     In operation block  306 , optimal orientation of the SLS tool design within the parts cylinder is predetermined. In one embodiment of the present invention, this predetermination involves including all features of the tool  150  on the same side of the tool, thereby limiting warping on tool features in accordance with the present invention.  
         [0050]     In operation block  308  heat sinks, such as  202 ,  204 , or  206 , are positioned in various parts of the parts cylinder  102  such that tool features may be cooled immediately following the sintering process and while the rest of the tool or tool components are being sintered, thereby minimizing warping of the tool features. Alternate embodiments include activating the heat sinks  202 ,  204 ,  206  or alternately inputting them into the parts cylinder  102  prior to sintering. Further alternate embodiments include a single heat sink, or a heat sink activating in various regions corresponding to tool features on the tool being sintered.  
         [0051]     In operation block  310  the sintering process is activated, and the controller  105  activates the pistons  114 ,  117 , the roller  118 , the laser  120 , and the mirrors  124 . The pistons force sinter material upwards or in a direction of the powder leveling roller  118 , which rolls the sinter powder such that it is evenly distributed as a top layer on the parts cylinder  102 . The laser  120  is activated and a beam  126  is directed towards scanning gears, which may be controlled as a function of predetermined requirements made in operation block  302 . During the sintering operations, the heat sinks  202 ,  204 ,  206  are activated for cooling various sintered portions of the tool  150  as they are sintered, and as other parts of the tool are being sintered such that warping is minimized. In alternate embodiments wherein a plurality of tool sections, such as a first and second tool section, are sintered collectively or successively, heat sinks may be included to cool various features of the second tool section as well.  
         [0052]     In operation block  312 , post-sintering process adjustments are conducted. These adjustments include removing warped portions that were deliberately warped such that tool features would not undergo typical warping associated with the sintering process. Further, post-process adjustments involve fitting together components or sections of the tool  150 .  
         [0053]     In operation, a method for laser sintering a tool includes predetermining a position and a configuration for a slot on a first section of the tool and predetermining an orientation of the first section of the tool within the part chamber as a function of minimizing warping of parameters of the slot during sintering. The method further includes laser sintering the first section of the tool within the part chamber. A strengthening component is coupled within the slot for reducing stress on the first tool section.  
         [0054]     Further, a position for a second tool feature on a contoured detail is predetermined, and an orientation of the contoured detail within the part chamber as a function of minimizing warping of the second tool feature during sintering is also predetermined. The contoured detail is laser sintered; and the contoured detail is coupled to the first section through bolting a bolt through a hole in the first tool section, such that the bolt intersects the slot in an area of the strengthening component and bolts to the strengthening component.  
         [0055]     From the foregoing, it can be seen that there has been brought to the art a new and improved tooling system and method. It is to be understood that the preceding description of the preferred embodiment is merely illustrative of some of the many specific embodiments that represent applications of the principles of the present invention. Numerous and other arrangements would be evident to those skilled in the art without departing from the scope of the invention as defined by the following claims.