Patent Publication Number: US-2021187792-A1

Title: Mold Made from an Additive Manufacturing Technology

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Canadian Patent Application No. 3065462 filed Dec. 18, 2019, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention generally relates to the field of molds for the production of molded parts which can be made of composite materials for example. More specifically, the invention relates to a mold made using an additive manufacturing technology and to a method of producing such a mold. 
     Description of Related Art 
     Molds used in the production of components made from composite materials using a reinforcing fabric in a matrix are typically themselves made out of composite materials. Current mold technology first requires the production of a plug, which is an intermediate component representing the surface of the composite material component that is to be ultimately molded in the mold. The plug is then polished to a smooth finish. The mold, itself made from layered composite materials, is then molded over the plug. Only then can the mold be used to produce components made from layered composite materials. The mold manufacturing process is rather long, tedious, and expensive. 
     Recent years have seen the advent of additive manufacturing technologies, also known as 3D printing techniques, which may directly produce finished components, thereby saving time and money. Such additive manufacturing technologies have been used to produce molds for the production of components made of layered composite materials. These printed molds are however limited to the size of the additive manufacturing machine used to print them. This is a problem when the production of large composite components requires a mold exceeding the capacity of the additive manufacturing machine. 
     For molds larger than the build chamber of the additive manufacturing machine, Stratasys™, a manufacturer of additive manufacturing machines, published in its Design Guide that molds may be segmented. The different segments of the mold may then by joined with secondary operations, such as thermal welding or structural bonding. To assist in assembly, Stratasys™ suggests using joint features incorporated into the mold design to ensure proper fit and alignment. Common assembly joining techniques such as tongue and groove, dovetails, and saw-tooth patterns are recommended. 
     These guidelines however fall short of teaching how to precisely locate molding surfaces of each segment with respect to one another, which is very important in order to produce a seamless surface finish on the composite component molded therein. 
     There is therefore a need for a mold made from an additive manufacturing technology capable of producing large components made from layered composite materials. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a mold for manufacturing layered composite materials and a method of manufacturing such a mold that overcomes or mitigates one or more disadvantages of known molds and methods of making them, or at least provides a useful alternative. 
     The invention provides the advantages of precisely locating the surfaces of adjacent mold segments so as to create a continuous molding surface from one segment to another. Moreover, the bonding area between segments is improved and the sealing of the molding surface is also improved. 
     In accordance with an embodiment of the present invention, there is provided an open mold for producing components made of a moldable material such as layered composite materials. The mold comprises a first mold segment and a second mold segment both made from an additive manufacturing technology. The first mold segment comprises:
         a first support structure defining a support plane underneath;   a first molding surface operative to receive the moldable material. The first molding surface is supported by the first support structure. The first molding surface has a first edge;   a first overlapping interface located between the support plane and the first edge at a first predetermined distance from the first edge. The first overlapping interface extends behind the first edge;   a first interlocking element located in the first overlapping interface.
 
The second mold segment comprises:
   a second support structure having the support plane underneath;   a second molding surface operative to receive the moldable material. The second molding surface is supported by the second support structure. The second molding surface has a second edge;   a second overlapping interface located between the support plane and the second edge at the first predetermined distance from the second edge. The second overlapping interface extends beyond the second molding surface; and   a second interlocking element located in the second overlapping interface. The second interlocking element is compatible with the first interlocking element and interlocks in an interlocking plane the first mold segment with the second mold segment. The first predetermined distance is measured in a direction normal to the interlocking plane.       

     The first overlapping interface overlaps the second overlapping interface. The second overlapping interface abuts against the first overlapping interface in a direction normal to the interlocking plane so that the first edge is juxtaposed with the second edge and so that the first molding surface is juxtaposed with the second molding surface. The term “juxtaposed” here is understood to mean “placed side by side” and not “contrasted” or “compared”. 
     The first interlocking element may be a male interlocking element. In this case the second interlocking element is a female interlocking element and vice-versa. 
     Preferably, the first interlocking element is located remotely from the first edge and at a second predetermined distance from the first edge while the second interlocking element is also located remotely from the second edge and at the same second predetermined distance from the second edge. In this case, the predetermined distance is measured in the interlocking plane which, preferably, is parallel to the support plane. 
     Optionally, the first mold segment may further comprise a sealing zone in the first overlapping interface. The sealing zone is located between the first edge and the first interlocking element. The second mold segment then comprises a depression in the second overlapping interface. The depression contains an adhesive contacting the sealing zone. 
     Alternatively, the second mold segment may be the one comprising the sealing zone which is then located in the second overlapping interface. The sealing zone is located between the second edge and the second interlocking element. The first mold segment then comprises a depression in the first overlapping interface. The depression contains the adhesive which contacts the sealing zone. 
     The first edge and the second edge may be parallel. The first molding surface and the second molding surface may be tangent to each other in a plane that is normal to the first edge. 
     Preferably, the second mold segment is welded to the first mold segment along the first edge and a finishing layer is applied on the first molding surface and on the second molding surface. 
     More preferably, the first support structure and the second support structure partially overlap each other in a second overlapping interface. An adhesive may also be applied in this second overlapping interface. 
     In accordance with another embodiment of the present invention, there is provided a method for manufacturing an open mold adapted to produce components made of a moldable material such as layered composite materials. The method comprises:
     a) manufacturing a first mold segment using an additive manufacturing technology. The manufacturing the first mold segment further comprises:
       building a first support;   building a first molding surface having a first edge. The first molding surface is connected to the first support;   building a first overlapping interface at a predetermined distance from the first edge. The first overlapping interface is located between the support plane and the first edge. The first overlapping interface extends behind the first edge;   building a first interlocking element in the first overlapping interface;   
       b) manufacturing a second mold segment using an additive manufacturing technology. The manufacturing the second mold segment further comprises:
       building a second support;   building a second molding surface having a second edge. The second molding surface is connected to the second support;   building a second overlapping interface at the predetermined distance from the second edge. The second overlapping interface is located between the support plane and the second edge. The second overlapping interface extends beyond the second edge;   building a second interlocking element in the second overlapping interface;   
       c) interlocking the second interlocking element with the first interlocking element so as to compatibly interlock the first mold segment with the second mold segment in an interlocking plane, said predetermined distance being measured in a direction normal to said interlocking plane; and   d) abutting the second overlapping interface against the first overlapping interface in a direction normal to the interlocking plane so as to juxtapose the second edge with the first edge and the second molding surface with the first molding surface.   

     Preferably, the molding surface may be tangent to the first molding surface in a plane normal to the first edge. 
     The interlocking may further comprise interlocking in a plane parallel to a support plane defined by the first support and the second support. 
     Optionally, the method may further comprise applying an adhesive in a depression of one of the first and the second overlapping interfaces and then pressing the first and the second mold components against each other so as to wet a sealing zone of the other one of the first and the second overlapping interfaces with the adhesive. 
     The method may also comprise welding the second mold segment to the first mold segment along the first edge. 
     Optionally, the method may further comprise polishing the first molding surface and the second molding surface. It may also include applying a finishing layer on the first molding surface and on the second molding surface. 
     Optionally, the method may further comprise overlapping the first support structure with the second support structure, thereby defining a second overlapping interface. It may also include applying an adhesive on the second overlapping interface. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       These and other features of the present invention will become more apparent from the following description in which reference is made to the appended drawings wherein: 
         FIG. 1  is an isometric view from above of a mold in accordance with an embodiment of the present invention; 
         FIG. 2  is an isometric view from below showing the underside of the mold of  FIG. 1 ; 
         FIG. 3  is an isometric exploded view from above of two adjacent segments of the mold of  FIG. 1 ; 
         FIG. 4  is an isometric exploded view from below of the two adjacent mold segments of  FIG. 3 ; 
         FIG. 5  is an isometric view of one of the mold segments of the mold of  FIG. 1  as it is built on a printing bed of an additive manufacturing machine; and 
         FIG. 6  is a schematic of a method of manufacturing a mold made using an additive manufacturing technology in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates to an open mold for layered composite materials and a method for manufacturing such a mold where the mold is made of segments which interlock and abut precisely with each other to generate a continuous molding surface. 
       FIG. 1 , now referred to, shows a mold  10  and its molding surface  12 . The mold  10  as shown only stretches to the limits of a part to be molded and does not include trimming extensions to the molding surface  12  which are typically added to provide a neat cutting surface. The mold  10  is of the open type and is adapted to receive a moldable material, such as reinforced layered composite materials, in order to produce components made of this moldable material. The mold  10  is made from an additive manufacturing technology, such as VAT Photopolymerization, Material Jetting, Binder Jetting, Material Extrusion (commonly known as Fuse Deposition Modelling (FDM) or 3D Printing), Powder Bed Fusion, Sheet Lamination or Directed Energy Deposition or any other adequate additive manufacturing technology. Guidelines for to the selection of the right process as well as for the selection of a suitable mold material are already documented in reference documents such as Stratasys® Design Guide for composite tooling. These will therefore not be further described here. 
     In order to build a mold  10  that exceeds the size limits of the manufacturing machines using these additive manufacturing technologies, the mold  10  is split in at least two segments  14 . In the present example, the mold  10  is split in four segments  14   a ,  14   b ,  14   c  and  14   d , although in a more general case, the mold  10  may be made of any number of segments  14  greater or equal to two. These segments  14  may be manufactured sequentially on the same machine and then assembled together. The mold  10  also comprises a support  16  made to rest on a horizontal surface, and which thereby defines a supporting plane  18 . The supporting plane  18  is here defined as being in the X-Y plane. A Z axis is therefore normal to the supporting plane  18 . The molding surface  12  rests on the support  16 . 
     The support  16  is best shown in  FIG. 2 , now concurrently referred to. The supporting plane  18  corresponds to the underside of the support  16  and is coplanar for all segments  14 . The support  16  of a given segment  14  is made to overlap that of an adjacent segment  14  at a support overlapping interface  20 . The segments  14  may be detachably or permanently attached to one another by attaching together adjacent supports  16  at their common support overlapping interface  20  using an adhesive, plastic welding, fasteners, or any other adequate joining technique. 
     For convenience, the manufacturing and assembly of the mold  10  will now be described with reference to  FIG. 3  where only the two mold segments  14   a  and  14   b  will be considered. It should be understood that manufacturing and assembling mold segments  14   c  and  14   d , or any other number of mold segments  14  must be done by following the same principles as for manufacturing and assembling mold segments  14   a  and  14   b . In the following description, the suffix “a” or “b” added to an element&#39;s reference number means that it respectively belongs to either mold segment  14   a  or  14   b.    
     Each mold segment  14  comprises its own portion of molding surface  12  bordered by at least one edge  22 , at least one overlapping interface  24  and at least one interlocking element  26 . Preferably, each mold segment  14  comprises at least one edge  22 , at least one overlapping interface  24  and at least one interlocking element  26  for each other adjacent mold segment  14  to which it is connected. Note that edge  22  and overlapping interface  24  may each be continuous so that only a portion of them interfaces with an adjacent segment  14 . Also note that edge  22  and the overlapping interface  24  do not have necessarily to be rectilinear. For example, they could be curved. 
     The edges  22   a ,  22   b  of the two adjacent mold segments  14   a ,  14   b  are designed to match closely together once assembled since a minimum gap between each adjacent molding surface  12   a ,  12   b  is desired. Hence, edges  22   a  and  22   b , respectively of mold segments  14   a  and  14   b , are designed to end up parallel and as close as possible once the segments  14   a ,  14   b  are assembled together, while still providing sufficient fit tolerance to easily assemble the adjacent segments  14   a ,  14   b . Molding surfaces  12   a ,  12   b  may be designed to end up being tangent to each other in a plane that is normal to the edge  22  (either  22   a  or  22   b ) once assembled. Although such tangency between adjacent surfaces  12  is usual, it may not be absolutely required if, for example, there is a discontinuity in the molding surface  12 . It is however the case when the component to be molded has a continuous surface but requires a mold that is too large for the capacity of the additive manufacturing machine. 
     The overlapping interface  24  is located at a predetermined distance D from the edge  22 , anywhere between the support plane  18 , best shown in  FIG. 4 , now concurrently referred to, and edge  22 . The predetermined distance D is measured in the Z direction, that is normal to the supporting plane  18 . In other words, a point Pa on the overlapping interface  24   a  is located at the same predetermined distance D as a corresponding point Pb located on the overlapping interface  24   b . It is however preferable that the overlapping interface  24  be located in close proximity to the molding surface  12  so as to minimize dimensional variance caused by manufacturing tolerances. The overlapping interface  24  may be parallel to the supporting plane  18  while always remaining below the molding surface  12 , or it may follow the molding surface  12  by being offset underneath the molding surface  12  by the predetermined distance D. When the molding surfaces  12  of two adjacent mold segments  14  are designed to be tangent to each other, the predetermined distance D of corresponding points on each overlapping interface  24  must be the same for both mold segments  14 . This is the case in the example illustrated with points Pa and Pb of mold segments  14   a  and  14   b.    
     When two adjacent mold segments  14  must be assembled together, such as mold segments  14   a  and  14   b , overlapping interface  24   a  of mold segment  14   a  is designed to extend beyond its edge  22   a  by a predetermined distance W while the overlapping interface  24   b  of adjacent mold segment  14   b  is made to extend behind, or is set back from, its edge  22   b , by at least an equivalent predetermined distance W. 
     The overlapping interface  24  is designed to be sufficiently wide (width being understood as extending in the direction of the adjacent mold segment) so as to provide a large overlapping area to attach together adjacent mold segments  14   a ,  14   b , preferably using an adhesive. In order to prevent the adhesive from creating an additional thickness which would offset molding surfaces  12   a ,  12   b , depressions  28  in which the adhesive is contained may be located in either one or both of the overlapping interfaces  24   a  and  24   b . These depressions  28  may take different shapes. In fact, depressions  28  may be so broad so as to occupy most of the surface of the overlapping interface  24 , only leaving small abutting areas, or posts, scattered on the overlapping interface  24 , and with which the predetermined distance D is controlled. Alternatively, a single depression  28  could be used, defined by a ridge all around the overlapping interface  24 . 
     In order to provide better stability of the support  16 , supports  16   a  and  16   b  are provided with their own support overlapping interface  20   a ,  20   b . An adhesive may also be applied to the support overlapping interfaces  20   a ,  20   b  to further rigidify mold  10 . 
     In order to lock together and to precisely locate both mold segments  14   a ,  14   b  in an interlocking plane, at least one set of compatible interlocking elements  26  is provided. The compatible interlocking elements  26  are located in or proximate the overlapping interfaces  24  of each mold segment  14   a ,  14   b  intended to overlap one another. The interlocking elements  26  are positioned at a predetermined distance L from the respective edge  22  of their mold segment  14 . In other words, the point Pa on interlocking element  26   a  is located at the same predetermined distance L as the corresponding point Pb on the interlocking element  26   b  of mold segment  14   b.    
     The interlocking plane is parallel to the supporting plane  18 . This means that the locking of compatible interlocking elements  26  occurs in interlocking direction  30  which is normal to the supporting plane  18  and along the Z axis. This also means that the predetermined distance D is measured in the same interlocking direction  30 , or normal to the interlocking plane. 
     Because the interlocking elements  26  are located both remotely underneath the molding surface  12  and remotely from the edges  22 , the edges  22  on the mold surfaces  12  may adopt a shape that is different from the shape of both the overlapping interface  24  and of the interlocking element  26 . The interlocking elements  26  are offset both laterally from edge  22  and vertically underneath the molding surface  12 , thereby creating a sealing zone  29 . This sealing zone  29  provides a space between the top molding surface  12  and an underside  32  of the mold segment  14  which can be filled with adhesive. The sealing zone  29  is located between the edge  22  and the interlocking elements  26 . This space contributes to sealing the top molding surface  12  from air infiltrations through joints and interstices on the underside  32 , especially around the interlocking elements  26  which may have discontinuous shapes that are difficult to seal. This sealing is important when a molded component requires vacuum forming and when air must be prevented from reaching the molding surface  12 . The sealing zone  29  of one mold segment  14 , for example mold segment  14   b  is preferably flat so as to be easily sealed by the adhesive contained in the one or more depressions  28  located in an area of the overlapping interface  24   a  of the interlocked mold segment  14   a  which ends up being directly in contact with the sealing zone  29 . 
     In the set of compatible interlocking elements  26   a ,  26   b , a first interlocking element in mold segment  14   a  may be of a female type while a second interlocking element in mold segment  14   b  may be of a male type, or vice-versa. This is the solution depicted in  FIGS. 3 and 4 . For example, the set of compatible interlocking elements  26   a ,  26   b  of the two adjacent mold segments  14   a ,  14   b  may define a dovetail assembly. Note that the compatibility of each male-female interlocking elements  26  between each adjacent mold segment  14  is independent. For example a first mold segment  14   a  could have a male set of interlocking elements  26  for interlocking with a second mold segment  14   b  and a female set of interlocking elements  26  for interlocking with a third mold segment  14   c.    
     The mold segments  14   a ,  14   b  are assembled by aligning the corresponding compatible interlocking elements  26   a ,  26   b  and bringing together both mold segments  14   a ,  14   b  along the Z axis until the overlapping interfaces  24   a ,  24   b  abut against each other. By engaging each other, the compatible interlocking elements  26   a ,  26   b  precisely locate edges  22   a  and  22   b  beside each other, and most importantly precisely juxtapose molding surfaces  12   a ,  12   b  with respect to each other so as to create, when required, a continuous molding surface  12 . Moreover, combining the compatible interlocking elements  26   a ,  26   b  with the overlapping interfaces  24   a ,  24   b  allows holding captive in 5 directions both mold segments  14   a ,  14   b  with respect to each other. The compatible interlocking elements  26   a ,  26   b  hold captive the mold segments  14   a ,  14   b  in the X-Y plane while the overlapping interfaces  24   a ,  24   b  prevent both mold segments  14   a ,  14   b  from moving in one of Z+ or Z− direction, depending which mold segment is used as a reference. The adhesive applied to the overlapping interfaces  24   a ,  24   b  prevents the mold segments  14   a ,  14   b  from moving with respect to each other in the opposite Z− or Z+ direction, thereby completely securing both mold segments  14   a ,  14   b  together. 
     Once assembled, the mold segments  14   a ,  14   b  may be welded together along their parallel edges  22   a ,  22   b . Although not absolutely necessary when the mold segments  14   a ,  14   b  are already bonded together at their overlapping interface  24 , welding along edges  22  allow filling an eventual small assembly gap. Filler material made of either plastic or metal (depending as to whether the mold  10  has been manufactured respectively out of plastic or metal) may therefore be used during welding to better fill this assembly gap. Following the optional welding step, the molding surface  12  may be abraded to smooth out perceptible build lines, and then sealed. The molding surface  12  may then undergo a final polish, resulting in surface finishes consistent with typical industry requirements. Sealing can be performed using a range of materials depending on specific application. The most common materials used are high-temperature, two-part epoxy adhesives. Epoxy film adhesives, adhesive-backed FEP films and similar products have also been used. Once the molding surface  12  is sealed, common mold-release agents may be applied in preparation for laying up the molded part. 
       FIG. 5  is now concurrently referred to. As per recommended practices, the mold segment  14  may be manufactured by gradually building the molding surface  12  in a cross-flow direction  35 , that is a direction normal to a printing bed  34  of the additive manufacturing machine. A first portion  36  of the support  16  is printed in a flow direction, that is in a plan parallel to the printing bed  34  while a second portion  38  of the support  16  is printed in the cross-flow direction. The second portion  38  of the support  16  may have openings  40 . The openings  40  may have sides printed at substantially 45 degrees from the cross-flow direction. Similarly, sides of the interlocking elements  26  may be printed at angles ranging from 1 to 45 degrees from the printing bed  34  to provide interlocking faces  42  of the interlocking element  26 , while using the capacity of the additive manufacturing machine to print at such angles without recourse to a detachable printed supporting structure. 
       FIG. 6  is now concurrently referred to. The method of manufacturing the mold  10  comprises manufacturing at least a first and a second mold segments  14  using an additive manufacturing technology. Manufacturing the first mold segment  14  comprises:
         building a first support  100 ;   building a first molding surface  102  with a first edge  22   a  connected to the first support  16   a;      building a first overlapping interface  104  at a predetermined distance D from the first edge  22   a;      building a first interlocking element  106  in the first overlapping interface  24   a.          

     Then, the method comprises manufacturing a second mold segment  14   b  also using the additive manufacturing technology. The manufacturing the second mold segment  14   b  comprises:
         building a second support  200 ;   building a second molding surface  202  having a second edge  22   b  connected to the second support  16   b;      building a second overlapping interface  204  at the predetermined distance D from the second edge  22   b;      building a second interlocking element  206  in the second overlapping interface  24   b  where the second interlocking element  26   b  is compatible with the first interlocking element  26   a;          

     Once at least the first and the second mold segments  14   a ,  14   b  are manufactured, they can be assembled by interlocking the second interlocking element  26   b  with the first interlocking element  26   a  at  300 . This compatibly interlocks the first mold segment  14   a  with the second mold segment  14   b  in the interlocking plane parallel to the supporting plane  18 . Finally, a step of abutting or pressing the second overlapping interface  24   b  against the first overlapping interface  24   a  in a direction normal to the interlocking plane so as to juxtapose the second edge  22   b  with the first edge  22   a , the second molding surface  12   b  with the first molding surface  12   a  and the first overlapping interface  24   a  with the second overlapping interface  24   b . Preferably, the adhesive may be applied in one of the overlapping interfaces  24   a ,  24   b , preferably in the depressions  28 , prior to the step of abutting, so as to permanently bond both mold segments  14   a ,  14   b  together. Surfaces  12   a ,  12   b  may be welded together. 
     The present invention has been described with regard to preferred embodiments. The description as much as the drawings were intended to help the understanding of the invention, rather than to limit its scope. It will be apparent to one skilled in the art that various modifications may be made to the invention without departing from the scope of the invention as described herein, and such modifications are intended to be covered by the present description. The invention is defined by the claims that follow.