Abstract:
The instant invention relates to a method for changing characteristics of a plastic component, wherein a medium is introduced into the plastic component, which encompasses a porosity and wherein the medium forms a homogenous compound with the plastic component by at least partially dissolving the plastic component.

Description:
CLAIM OF PRIORITY 
       [0001]    This application is a national phase of PCT application No. PCT/DE2008/001603, filed Oct. 6, 2008, which claims priority to German Application No. DE 10 2007 050 953.9, filed Oct. 23, 2007, all of which are incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a device for manufacturing patterns in layers, which encompasses a mounting plate, guides for moving a spreader device and a drop dispensing system, a vertically displaceable and exchangeable build platform as well as a material feeding device, wherein the main elements of the device are mounted to the mounting platform before it is introduced into a housing and is fixed therein. The present invention further relates to use of such a device. 
       BACKGROUND 
       [0003]    Today, the development of components represents new demands on the producing industry. The increasing time and cost pressure can be confronted in that new methods, such as rapid prototyping and rapid tooling are used. 
         [0004]    A method (Object) is thus known, for example, where a polymeric material, which can be hardened, is applied in the form of liquid droplets onto a vertically displaceable build platform or workpiece platform selectively within a contour of the corresponding cross section of the desired object by means of a displaceable dispensing device and is hardened by means of UV radiation. The desired component is created layer by layer by means of repeated application. The object is subsequently removed from the build platform. 
         [0005]    In the case of another method, a layer of a free-flowing particulate material is settled in an area on a build table. A binder material in the form of liquid droplets is then applied onto the layer of particulate material in a selected partial area by means of a displaceable dispensing device. Binder material and particulate material form a solidified structure. Further layers are in each case formed by repeating the afore-mentioned steps. The solidified structure is then separated from non-solidified portions of the particulate material. 
         [0006]    Different devices are known to carry out such so-called rapid prototyping methods, which are known from the state of the art. 
         [0007]    A typical embodiment of a device according to DE0010047614, e.g., consists of a welded tube frame supporting adapted guide tracks. Such frames are joined from a plurality of elements and are set up extensively. Due to the fact that the joining areas are located around the frame parts, the component parts must be fully machined all around. The casing is then hung on the completely mounted device and thereby does not have any supporting function. 
         [0008]    A very simple device, which substantially consists of profiled sheet metal parts, to which simple rod guides are screwed directly, is known from WO20030160667. At any rate, this embodiment has limitations with reference to the device accuracy and is thus only suitable for smaller device dimensions, because the guide deviations do not stand out so much in that case. However, it has proven to be disadvantageous in the case of all of the devices known from the state of the art and from practice that the mounting and adjusting of the system is time-intensive and expensive. 
       SUMMARY OF THE INVENTION 
       [0009]    According to the invention, this objective is solved in the case of a device for manufacturing patterns of the afore-mentioned type in layers by using a mounting plate, to which all of the process-relevant positioning units and conveying devices are mounted before the mounting plate together with the attached devices is introduced into a housing and is fixed therein. 
         [0010]    For this, the mounting plate encompasses cut-outs for the build platform, the powder supply and removal as well as for maintenance units for the drop dispensing apparatus, such as cleaning and capping station, e.g. 
         [0011]    In addition, the mounting plate encompasses fastening possibilities for the positioning axes of the drop dispensing unit and the spreader device as well as for the positioning unit of the build platform. 
         [0012]    The mounting plate is thereby dimensioned in such a manner that, when being fixed on only a few points, it does not deform or only within narrow margins, so as to ensure the accuracy in the case of the application mechanisms. 
         [0013]    This applies in particular for the stress caused by weight of the attached units and weight of the particulate material on the build platform during the layering process. 
         [0014]    The mounting platform is thereby embodied as a plane plate, e.g. of a fully machined aluminum plate. 
         [0015]    The build platform is located in a construction cylinder, which is advantageously embodied as an exchangeable container. The construction cylinder contains a build platform, which can be moved in the direction of the cylinder and which cannot slip out of the construction cylinder in its lower end position. On its lateral edge facing the wall of the construction cylinder, the build platform encompasses a seal, which keeps the applied particulate material from flowing by. To introduce the weight forces of the exchangeable container and the additional friction forces caused by the friction between build platform and exchangeable container wall into the mounting plate in the shortest possible way, a guide for the exchangeable container is located on the underside of the mounting plate. The exchangeable container in turn encompasses guide elements on the two opposite upper ends on the outsides of the construction cylinder. 
         [0016]    Via these guide elements, the exchangeable container can easily be introduced into the device and is thereby fixed in vertical direction. Roller guides, e.g., are suitable as guide elements. The rollers can be arranged on the underside of the mounting platform along the introduction path of the exchangeable container, e.g. The exchangeable container then again encompasses a matching guide rail, which engages with the rollers in a positive manner or encloses them in a positive manner. 
         [0017]    Advantageously, a stop, which defines an end position of the exchangeable container in the device, is located at the end of the introduction path. After introduction into the device, the exchangeable container is fixed by means of a holding device. 
         [0018]    The movement of the build platform takes place via a vertical hoisting mechanism, which is orthogonally attached to the mounting plate. The hoisting mechanism can consist of one or a plurality of threaded spindles, e.g., which are mounted in an intermediate platform so as to be pivot-mounted in spindle nuts, with said intermediate platform being located below the build platform. The threaded spindles can be actuated via a common belt drive and a servomotor. 
         [0019]    When using two or a plurality of simultaneously operating spindles, an additional guide of the hoisting mechanism can become unnecessary, because the build platform can be sufficiently fixed in its position with said spindles and all moments of tilt are sufficiently discharged. The intermediate platform can then be fastened to the mounting platform via spacer plates, e.g. In the alternative, the hoisting mechanism can also be affixed on the side of the exchangeable container and can then be equipped with guide elements, such as rails comprising guide carriages, e.g. The build platform in the exchangeable container is then connected to the hoisting system in a non-positive manner via a coupling element. This can be, e.g., a pneumatically actuated zero point clamping system, as it is known from tooling machines. All of the displacement movements are transferred onto the build platform via the coupling and all forces and moments acting on the build platform, such as, e.g., frictional forces of the seal between container wall and platform, densification forces in response to the layer application and gravitational forces are in turn guided into the hoisting system by means of the particulate material. The axes for the movement of the spreader unit and for the drop dispensing apparatus are mounted on the mounting plate. Axes refer to combinations of guide system and drive. The guide task can be fulfilled by rails and carriages, e.g., wherein the carriages comprising recirculating ball systems rolling on the rail. 
         [0020]    The drop dispensing apparatus is typically moved across the build field in a meander-style during the layering process. This movement is reached by means of a system of axes, which are aligned orthogonally to one another. Due to the dimension of the build field, a pair of axes to be arranged along the opposite sides of the build field is usually necessary to support a further axis as connection. 
         [0021]    The movement requires a most constant speed across the long displacement distance (X-axis) and accurate positioning across the short displacement distance (Y-axis). To minimize masses moved and wear of the axes, it proves to be advantageous for the individual axis to form the X-axis and for the pair of axes to serve as Y-axis. 
         [0022]    In the process, the drop dispensing apparatus preferably operates only in the area of constant speed in response to movement across the X-axis, so as to locally meter the drops accurately onto the build field. The drops are thus released here conform to impulses of a measuring unit system attached to the X-axis. A belt drive axis, providing an even run, can be used as movement system. Alternatively a threaded spindle axis be used. Due to the better positioning in this case, a linear measuring system is not necessary and can be replaced by an encoder mounted to the motor. Last but not least, a linear drive, as it is increasingly found in tooling machines, can also be used. The Y-axis, however, must position accurately, which requires a threaded spindle drive or a linear drive. 
         [0023]    The spreader apparatus, however, needs to be moved across the construction field at a speed, as constant as possible, while releasing particulate material onto the build platform. Belt drives as well as threaded spindle drives as well as linear drives are suitable for this kind of movement. 
         [0024]    The axes arrangement for the spreader apparatus may not collide with the axes for the drop dispensing apparatus. Due to the size of the build field and to reduce moment loading onto an axis, it is likely to use a pair of axes, which is arranged parallel to the Y-axis of the drop dispensing apparatus. 
         [0025]    To simplify the apparatus, it is possible to have no separate pair of axes for the spreader apparatus and using the Y-axis pair for the drop dispensing apparatus as well as for the spreader apparatus simultaneously instead. This takes place by mounting the spreader device onto the guide carriages of the Y-axis next to the X-axis. 
         [0026]    A feeder mechanism for refilling the spreader apparatus with particulate material is located at the end of the displacement distance. This material feed preferably takes place by means of a conveying system, which is operated from a particulate material reservoir below the mounting platform or outside of the device. In addition, a further particulate material reservoir is available below the mounting platform for excess particulate material, which is pushed above the edge of the build platform by means of the spreader unit. This particulate quantity is preferably discharged through an ejection slit in the mounting platform when the spreader unit moves across it. 
         [0027]    A further ejection slit is located on the opposite side of the construction field at the beginning of the travel of the spreader device. 
         [0028]    The device can be closed by means of a casing. For safety reasons, there is a need for a hood, which protects the user from particulate dusts and process vapors and which prevents accidental contact to moving parts, in particular in the processing room above the mounting platform. This hood should be movable in such a manner so as to allow the best possible access to the elements of the device during standstill. A flap mechanism, which makes it possible to open the hood, is suitable for this purpose. The flap mechanism can be affixed directly to the mounting platform. A seal introduced into the mounting platform further shields the processing room from the environment. 
         [0029]    To further shield the processing room from the underside of the mounting platform, the introduction path for the exchangeable container can be covered by a housing. A door arranged at the beginning of the introduction path closes the introduction path during the process. 
         [0030]    When the mounting platform is dimensioned to be sufficiently large so as to cover the outer edge of a casing located there below, the processing room can thus be sealed sufficiently towards the bottom. 
         [0031]    The casing below the mounting platform can be embodied in such a manner that it simultaneously functions as a rack and supports the mounting platform. In an advantageous embodiment, the casing consists of a single component, which encloses the device, e.g. of profiled and welded sheet metal parts, which accommodates the mounting platform. 
         [0032]    Component assemblies, such as control cabinet, fluid and compressed air supply, can be accommodated in a space-saving manner in the enclosed room below the mounting platform. 
         [0033]    Due to the embodiment of the mounting platform as a plane plate, the effort for orienting the pair of axes to one another is minimized. Only the parallelism of the axes must be checked. Simple stops of the axes can be introduced into the mounting plate by means of alignment pins and can provide for the correct position of the axes at least on one side. In response to a sufficient dimensioning of the mounting platform, the casing at the accommodation of the mounting platform must not be machined, which considerably reduces the production costs. To fasten the mounting plate, only vertically displaceable fastening elements must then be used at different locations, to adjust the distance of the mounting platform to the casing. 
         [0034]    To simplify the mounting of the device, all attachment parts can be mounted, adjusted and wired to the mounting plate while placed outside of the casing. Preferably, this takes place on a separate simple mounting rack. The accessibility is thereby better than in the fully assembled state in the casing. 
         [0035]    A preferred embodiment will be described below by means of the drawings. 
         [0036]    It is thus objective of the present invention to provide a device for manufacturing patterns in layers, which is as accurate as possible, easy to mount and yet cost-effective to make. 
         [0037]    Accordingly, pursuant to a first aspect of the present invention, there is contemplated a device for manufacturing patterns in layers, encompassing a vertically displaceable build platform, a dispensing device for applying binder material onto the build platform, wherein the device additionally encompasses a mounting platform, to which all displacement units for the dispensing device and for the build platform are affixed. 
         [0038]    The first aspect of the present invention may be further characterized by one or any combination of the features described herein, such as a spreader device for applying fluid is provided; all displacement units of the spreader device are further affixed to the mounting platform; the dispensing device and/or the spreader device are further affixed to the mounting plate. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0039]      FIG. 1  shows an embodiment of the device as a tube frame (state of the art). 
           [0040]      FIG. 2  shows a diagonal view onto the partially mounted mounting platform. 
           [0041]      FIG. 3  shows a front view of the mounting platform comprising attached axes. 
           [0042]      FIGS. 4 a -4 c    shows the introduction of the mounting platform into the casing. 
           [0043]      FIG. 5  shows the mounted device in the diagonal view. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0044]      FIG. 1  shows a device for three-dimensional printing according to the state of the art without an attached casing. The surrounding tube frame  101 , which supports the individual guides for the elements such as the spreader device  104 , X-axis  107 , Z-axis  105 , and the material feeder  110 . 
         [0045]      FIG. 2  shows the mounting platform  21  according to the present invention comprising the attachment parts. A pair of guide carriages  22  are fixed to the opposite sides of the construction field  23  and the mounting platform along a Y-axis  60 . The print head  28  is mounted to a carriage  8  that is attached to and spans between the pair of guide carriages  22  along the print head axis  7 . The spreader device  4  is also guided on the pair of guide carriages  22  along the Y-axis  60 . The material feeder  10  is located in the front part of the mounting platform  21 . The cleaning station  24  for the print head  28  can be seen in the front area. Next to it is the capping station  25 , which closes the print head  28  during standstill and which thus prevents a drying or soiling of the print head  28 . 
         [0046]    The build platform  62  is mounted below the mounting platform along a Z-axis  26 . The introduction room for the exchangeable container  2  (not shown) is shielded by means of the casing  27 . 
         [0047]      FIG. 3  shows the mounting platform  21  comprising the attachment parts in side view. In this position, the exchangeable container  2  can be seen, which is introduced via the guide  30  at the mounting platform underside so as to be displaceable only in horizontal direction up to the position below the construction field cut-out  23  and is then held in position via the catch  29 . In this embodiment, the build platform  62  consists of four simultaneously driven threaded spindles, which are supported in the intermediate platform  52  along the Z-axis  26 . It is fixed to the mounting platform  21  via the mounting plates  45  of the casing  27 . 
         [0048]      FIG. 4  shows the mounting process of the preassembled mounting platform  21  in the image sequence shown in  FIGS. 4 a  to 4 c    into the chamber  40 . The attachment parts such as a pair of guide carriages  22 , material feeder  10 , and a build platform  62  movable along the Z-axis  26 , e.g., are mounted to the mounting platform  21  ( FIG. 4 a   ), while said mounting platform  21  rests on an auxiliary frame  47 , which allows for the best possible accessibility. Subsequently ( FIG. 4 b   ), the preassembled mounting platform  21  is lifted into the provided chamber  40 , e.g. from the auxiliary frame  47  by means of crane splices  50 . Finally ( FIG. 4 c   ), the mounting platform  21  is connected to the chamber  40  by means of screwing and the cap  41  (not shown) is placed thereon. 
         [0049]      FIG. 5  then shows the completely mounted device comprising a chamber  40 , mounting platform  21  and cap  41 . Doors  42  to cover the introduction space for the exchangeable container  2  are located below the mounting platform  21 .