KR20070029813A - Gas permeable molds - Google Patents

Abstract

Gas permeable molds and mold segments having open porosity (60) are disclosed. Blind vents (56) in the mold wall's (54) outside surface (52) allow for an uninterrupted molding surface (62) while enhancing the gas permeability provided by the open porosity (60). Methods of making such gas permeable molds include forming them from sintered material. Methods also include the use of solid free-form fabrication followed by sintering. Also disclosed are unitary structures (150), for use in EPS bead molding, having a steam chest portion (152) with gas impermeable walls (156) and a mold section (154) having a gas permeable mold wall (172) having open porosity (176), and, optionally, open and/or blind vents (180, 178). Methods for making such unitary structures (150) include the use of solid free-form fabrication. ® KIPO & WIPO 2007

Description

Gas Permeable Mold {GAS PERMEABLE MOLDS}

The present invention relates to a gas permeable mold and a method of making such a gas permeable mold.

The mold consists of two or more opposing segments that together form a mold cavity from which the article is molded from the moldable material. A gas permeable mold is a mold that allows gas to flow into and out of the mold cavity during the molding process. Typically, the permeability of the mold to gas flow is achieved by providing the mold with a plurality of vents distributed over selected portions of the forming surface. For example, a mold for making an article from foamed polymer beads, such as foamed polystyrene (“EPS”), includes a plurality of vents that deliver vapor into the mold such that the polymer beads are further expanded to bond together. The injection molding mold includes a vent that can enclose air exiting the mold during the injection process. Vacuum forming tools, such as those used to thermoform plastic sheets, include vents formed on the surface of the tool to evacuate the vacuum between the tool and the plastic sheet.

The most common way of forming such vents in a gas permeable mold is to perform some type of drilling step on the forming surface, such as by punching or drilling by any mechanical, electrical, optical or chemical means. In the case of EPS bead molds, a conventional vent forming method consists of drilling shoulder holes with a major shaft diameter of about 0.16 cm to about 0.64 cm. After drilling these shoulder holes, the cylindrical hardware with slotted end face is forcibly fit into the hole, and then the forming surface is machined to ensure that the hardware is coplanar with the forming surface.

Conventional vent forming processes are expensive and time consuming. Furthermore, conventional vent forming processes restrict the placement of vents in areas accessible to the tool used to form the vents. If venting is required in other inaccessible areas, it is necessary to divide the article so that it is accessible to a given area, form vents or vents in separate sections, and then reassemble the separated sections back into the article. Another drawback is that the orientation of the vent to the forming surface is limited by the drilling technique employed and the accessibility of the portion of the surface on which the individual vent is placed. If the surface shape is curved or complex or access is restricted, the vent may have an orientation that is not optimal. When techniques such as laser or chemical drilling are used, the orientation of the small diameter fluid delivery vents is usually defined almost perpendicular to the surface of the article.

In recent developments in the art, solid free molding processes, as described in US Patent Applications Nos. 60 / 501,981 and 60 / 502,068, filed September 11, 2003, in the name of co-pending Rynerson et al. Solid free-form fabrication is employed to produce a gas permeable mold having vents formed in place when the mold itself is constructed in a layered fashion from particulate material. As used herein and in the appended claims, the term “solid free forming process” refers to any process that includes providing a useful three-dimensional article and shaping the shape of the article continuously, one layer at a time, from the powder. Solid free forming processes are also known in the art as " layered manufacturing process. &Quot; When a layer-by-layer building process is used to produce a small amount of a particular article, the solid free manufacturing process is also referred to in the art as "rapid prototyping process" or "rapid manufacturing." The solid free forming process may include one or more shape forming operations that enhance the physical and / or mechanical properties of the article. Preferred solid free forming processes include three-dimensional printing ("3DP") processes and selective laser sintering ("SLS") processes. An example of a 3DP process can be found in US Pat. No. 6 / 036,777 to Sachs, issued March 14, 2000. An example of an SLS process can be found in US Pat. No. 5,076,896 to Bourell et al., Issued December 31, 1991.

In other recent advances, techniques have been developed for producing gas permeable molds that eliminate the use of conventional vents. These molds are machined from blocks of open sintered material with open porosity. As used herein and in the appended claims, the term "open pore" refers to pores in a material that are interconnected to be in fluid communication through the material. Open pores in these molds allow gas to pass through the mold walls and into and out of the mold cavity. It is advantageous to remove the vent from the forming surface. One advantage is that no nubs or patterns resulting from the venting of the forming surface are formed in articles made from these molds. Another advantage is that in the process of molding the particulate material, such as forming EPS beads, particulates of any size may be used without considering the particulates flowing out of or blocking the vents.

A drawback to these prior art open pore molds is that the gas permeability of these molds depends primarily on the thickness of the mold walls, the amount of pores and the density. Because the pores weaken the mold, the thickness of the mold wall must be increased when a solid material is used, but this increased wall thickness reduces gas permeability. To compensate for the increased wall thickness, the amount and density of pores can be increased. In some applications, a balance of operable strength and transmittance can be achieved, but in other applications this is not possible. In addition, achieving an operable balance can result in loss of smoothness of the molding surface due to the density of the pores in the molding surface.

The present invention provides a mold segment and gas permeability that has a smooth, vent-free forming surface and overcomes the drawbacks of mold wall thickness, strict interdependent densities and amounts of open pores, and gas permeability, which burden the prior art methods. It includes a mold. These gas permeable molds and mold segments have a mold wall with open pores, and the gas permeability of the open pores is increased by the gas permeability provided by the blind vent. As used herein and in the appended claims, the term "blind vent" refers to a depression on the outer side of the mold wall, the depression causing a substantial increase in gas transmission through the mold wall in the region adjacent to the depression. It is called. The blind vent may be similar in size and shape to conventional vents, but need not necessarily be similar in size and shape to conventional vents. In all cases, however, the blind vents differ from conventional vents in that they do not extend through the forming surface.

The use of blind vents offers several advantages. One advantage is that the molding surface is continuous, thereby avoiding the problem of a nub or venting pattern being formed on the surface of the molded article that intersects the molding surface or mold segment of the mold. Another advantage is that the use of blind vents reduces the density of open pores, providing a smoother forming surface without lowering the gas permeability. The third advantage is that the use of blind vents allows the mold wall thickness to be increased without lowering the gas permeability of the mold or mold segment, thus making it more powerful and more robust than gas permeable molds and mold segments with open pores possible in the prior art. It is possible to provide a more rigid mold or mold segment.

The present invention also includes methods for making such gas permeable molds and mold segments. In a preferred embodiment of the invention, such a method utilizes a solid free forming process and sintering to construct a gas permeable mold segment and a gas permeable mold in which blind vents are formed in the mold or mold segment during the solid free molding process. Include. The invention also includes embodiments in which the mold or mold segment is made from a sintered block having open pores and one or more blind openings are formed in the outer surface of the mold or mold segment.

The invention also includes embodiments in which the gas permeable EPS mold segment is part of a unitary structure having a vapor chamber. The vapor chamber is a plenum surrounding the gas permeable EPS mold segment. The steam room includes one or more ports that selectively deliver gas into and out of the cavity of the steam room, and the walls of the steam room themselves are gas impermeable. However, the gas permeable EPS mold segment has open pores. The gas permeability of the gas permeable EPS mold segment may be increased by one or more vents, which may be open or blind vents, or a combination of both, but need not be so. As used in this specification and the appended claims, the phrase “open vent” refers to a vent that extends continuously through the mold wall from the outer side of the mold to the forming surface of the mold. The invention also includes a method of making a unitary structure formed by a solid free forming process. In such a method, the vapor chamber is made gas impermeable by infiltrating the coagulating liquid. Embodiments of the unitary structure of the present invention have the advantage of using a vapor chamber to reinforce the gas permeable mold against both outward and inward forces encountered during the molding process. Alternatively, the vapor chamber may reinforce the gas permeable mold segment only against outward forces when it is not integral with the gas permeable mold segment.

Reference will be made to the accompanying drawings in order to better understand the importance of the features and advantages of the present invention. It is to be understood, however, that the appended drawings are merely for illustrative purposes and do not limit the invention.

1 is a schematic cross-sectional view of a prior art EPS bead mold system.

2A is a plan view of a portion of a gas permeable mold in accordance with a preferred embodiment of the present invention.

FIG. 2B is a sectional view of a mold wall of the gas permeable mold shown in FIG. 2A.

3A is a plan view of a portion of a gas permeable mold having blind vents of various geometries in accordance with a preferred embodiment of the present invention.

3B is a cross-sectional view of the mold wall of the gas permeable mold shown in FIG. 3A, taken along planes 3B-3B.

3C is a cross-sectional view of the mold wall of the gas permeable mold shown in FIG. 3A, taken along planes 3C-3C.

 4 is a cross-sectional view of a unitary structure of a gas permeable mold segment and a vapor chamber in accordance with a preferred embodiment of the present invention.

In this section, some preferred embodiments of the present invention are described in sufficient detail to enable those skilled in the art to implement the present invention. However, it should be understood that the limited number of preferred embodiments described herein in no way limits the scope of the invention described in the appended claims.

The present invention includes, in its embodiment, a gas permeable mold for all applications where a gas permeable mold is used, such as EPS bead molding, injection molding, vacuum molding, and the like. Likewise, the present invention includes in its embodiment a method of making all such gas permeable molds. However, for the sake of clarity and accuracy, only preferred embodiments of gas permeable molds for EPS bead molding are described. Likewise, the method of the present invention employing a solid freeform process can be implemented by any solid freeform process, such as 3DP, SLS, etc., but for the sake of clarity and accuracy of description, a preferred embodiment employing a 3DP process Explain only.

Referring to FIG. 1, partially expanded EPS beads 4 in a conventional EPS bead forming system 2 are filled into a closed EPS bead mold 6 through an inlet (not shown). The mold 6 consists of a first mold segment 8 and a second mold segment 10. The outer surface 12 of the first mold segment wall 14 and the first vapor chamber 16 form a first vapor chamber cavity 18. Likewise, the outer surface 20 of the second mold segment wall 22 and the second vapor chamber 24 form a second vapor chamber cavity 26. In a flow-through method, steam 29 enters first steam chamber cavity 18 through first port 28. Steam 29 passes through a plurality of first vents 30 in the first mold segment wall 14 to convey the mass of EPS beads 4 in the mold cavity 32 and the second mold segment wall 22. After passing through the second chest cavity 26 via a plurality of second vents 34 in the outlet, it flows out through the second port 36. Steam 29 heats the EPS beads 4 such that the swelling agent in the EPS beads 4, such as pentane, further expands the EPS beads 4 to fuse together in a shape defined by the mold 6. After the steaming step is completed, the outer surface 12 of the mold 6 by applying vacuum to the first and second vapor chamber cavities 18, 26 and / or via a spray nozzle (not shown) 20) cools the molded article formed from the expanded EPS beads by spraying water. Thereafter, the mold 6 is opened to separate the molded article. The EPS bead forming process is described in more detail in US Pat. No. 5,454,704 to Bishop, issued October 3, 1995.

Referring to FIG. 2A, a portion 50 of an outer surface 52 of a mold wall 54 of a gas permeable EPS mold with a blind vent 56 is shown, in accordance with a preferred embodiment of the present invention. 2B shows a cross-sectional view of the portion 50 taken along planes 2B-2B. The mold wall 54 has open pores 60 (indicated by dots) capable of fluidly communicating the outer surface 52 and the forming surface 62, so that the molding surface 62 is partially defined in use. Allow steam to pass in and out. The blind vent 56 extends from the outer side 52 to a predetermined depth 64 of the mold wall thickness 66, so that the blind vent end wall is between the bottom 70 of the blind vent 56 and the forming surface 62. Leave thickness 68.

In embodiments of the present invention, the blind vents can have any geometry that substantially enhances the gas permeability of the mold walls, and a single gas permeable mold or mold segment can include vents of various geometries. 3A-3C illustrate a preferred embodiment of the present invention having blind vents of various geometries. Referring to FIG. 3A, a flat portion 80 is shown on the outer surface 82 of the gas permeable mold wall 84 having a plurality of blind vents (typically denoted by reference numeral 86). Among the plurality of blind vents 86, a portion where the first blind vent 88, the second blind vent 90, and the third blind vent 92 intersect the outer side surface 82 is circular, and the fourth blind vent is provided. The portion where 94 intersects the outer surface 82 forms an elongated ellipse, the portion where the fifth blind vent 96 intersects the outer surface 82 is triangular, and the sixth vent 98 is The portion that intersects the side surface 82 forms a square, and the portion where the seventh vent 100 intersects the outer surface 82 forms a rectangle. 3B shows a cross sectional view of the mold wall 84 taken along plane 3B-3B perpendicular to the outer face 82. 3B shows that the first blind vent 88 is a staff cylinder, the second blind vent 90 is hemispherical, and the third blind vent 92 is conical. FIG. 3B also shows sidewalls 102 and 104 with parallel fourth blind vents 94 and curved bottoms 106, with inclined walls 108 and 110 of fifth blind vents 96 having vertices 112. FIG. Meet at, the parallel walls 114, 116 of the sixth blind vent 98 terminate at a flat bottom 118, and the opposing walls 120, 122 of the seventh blind vent 100 are flat bottom 124. It is curved at the point where it meets.

In an embodiment of the invention, the end wall of the blind vent, ie the mold wall thickness between the inner end of the blind vent and the forming surface, is the mold wall between the inner end of the blind vent and the forming surface while using the porous mold or mold segment. The thickness can be any thickness that provides sufficient local structural integrity for the segment to remain intact and in a continuous state, or thickness range where the blind vent does not have a bottom that is completely parallel to the forming surface. The end wall thickness of the blind vent may be the same between all blind vents and may vary from blind vent for permeable mold or mold segment. For example, referring to FIG. 3A, an eighth blind vent 126, a ninth blind vent 128, and a tenth blind vent 130 are all staffed. 3C shows a cross section of the mold wall 84 taken along plane 3C-3C perpendicular to the outer face 82. Referring to FIG. 3C, the thicknesses of the mold walls 132 and 134 associated with the eighth blind vent 126 and the ninth blind vent 128 are equal to each other, and the thickness of the mold wall associated with the tenth blind vent 130. It can be seen that it is different from 136.

In an embodiment of the invention, the mold wall thickness of the gas permeable mold or mold segment, the amount and number of open pores, the number, distribution and geometry or shapes of the blind vents, and the end wall thickness or thicknesses of the blind vents It is determined by considering the strength and gas permeability required for a particular mold or mold segment. Typically, these parameters will be determined by applying the knowledge and principles of those skilled in the art applicable to the open pore molds and mold segments of the prior art. However, it should be borne in mind that in these embodiments the overall gas transmission rate of the gas permeable mold or mold segment is the sum of the contributions to the permeability of the open pores and the gas transmission of the blind vents. In embodiments where open vents are also present, the contribution of these open vents to gas permeability should also be taken into account. The mold wall material between the inner end of the blind vent and the forming surface provides some resistance to gas flow but is substantially less than the total mold wall thickness in the region opposite the blind vent. The optimum geometry of the blind vents and the optimal thickness of the end walls of the blind vents can be determined by taking into account the chemistry and basic dynamics of the flow through the porous medium. For example, in the field of fluid transport, it is well known that the efficiency of flow is influenced by the shape of the orifice, and at the orifice end, the porous material and the blind vents surrounding the orifice can be seen as a network of interconnecting orifices and interconnecting orifices. Known.

By measuring the gas permeability of a desired mold wall material having varying amounts of porosity and density levels as a function of thickness over a range of pressure differences expected during a molding process using a gas permeable mold or mold segment, It may be taught to implement embodiments of the invention. Similar teaching will be obtained by testing the mechanical strength of the desired mold wall material with varying amounts of density and density levels as a function of thickness. The four-point loading test of the Modulus Of Rupture (MOR) usefully measures such mechanical strength. The number, distribution and geometry of the blind vents is preferably selected to have a mechanical strength that is approximately equal to the level of the permeable mold or mold segment without the blind vents, but it is not necessary.

In all embodiments of the invention utilizing one or more blind vents, the end wall thickness of the blind vents is from about 10% to about 70% of the local thickness of the mold wall, ie the penetration thickness of the mold wall where the blind vents are located. It is preferable that it is a range. The end wall thickness of the blind vent is more preferably in the range of 20% to 40% of the local thickness of the mold wall, and most preferably about 30% of the local thickness of the mold wall.

The mold or mold segment may be composed of any material that is suitable for the mold to be manufactured for the application in which the mold or mold segment is used and known in the art. For example, the mold material may comprise a metal, ceramic, polymer or composite. Preferably, the mold material is a metal selected from the group consisting of aluminum, titanium, nickel or iron, or alloys containing one or more of these metals. Most preferably, the mold material is stainless steel powder, such as grade 316 or 420.

The invention also includes a method of manufacturing a gas permeable mold and mold segment comprising one or more blind vents. In some embodiments of such a method, a mold segment or gas permeable mold having a plurality of openings is machined from a block or other form of suitable material having openings in a manner of the prior art. The blind vent is formed on the outer side of such a gas permeable mold or mold segment during or after machining the mold or mold segment, for example by machining.

In an embodiment of such another method, the gas permeable mold or mold segment is pressed and sintered to a final shape or an almost final shape followed by machining by powder metallurgy. In these embodiments, some or all of the blind vents may be formed directly during the powder metallurgy process and after the powder metallurgy process, for example by machining.

The invention also includes an embodiment of a method of forming a gas permeable mold or mold segment having open pores by a solid free forming process followed by sintering. In some of these less preferred embodiments, one or more blind vents are formed before the sintering step or after the free forming manufacturing step following the sintering step, but in a more preferred embodiment one or more vents are formed in the solid free forming process step. In the mold or mold segment.

Preferably, the 3DP process is employed as the solid free forming process method. The 3DP process is conceptually similar to inkjet printing. However, the 3DP process deposits a binder on the top layer of the powder bed instead of ink. Such a binder is printed with a powder layer according to a two-dimensional slice of a three-dimensional electronic image of a mold or mold segment to be produced. The layers are printed in sequence until the entire mold or mold segment is molded. The powder can be made of metal, ceramic, polymer or composite. Preferably, the powder is a metal selected from the group consisting of aluminum, titanium, nickel, or iron or alloys containing one or more of these metals. Most preferably, the powder is a stainless steel powder, such as grade 316 or 420, and has a particle size of -140 mesh / + 325 mesh. The binder may comprise one or more of a polymer and a hydrous carbon. Examples of suitable binders are shown in US Pat. No. 5,076,869 to Bourell et al. Issued December 31, 1991 and US Pat. No. 6,585,930 to Liu et al. Issued July 1, 2003.

The gas permeable mold or mold segment after the printing step is typically a binder consisting of about 30 to 60 volume percent powder depending on the packing density of the powder and the remainder of the void space. The printed mold or mold segment is somewhat fragile. Next, the printed mold or mold segment is sintered at elevated temperature to improve its physical and / or mechanical properties. For example, the powder used may have a particle size of -140 U.S. Mesh (106 micron) / + 325 U.S. In the case of 316 stainless steel, which is a mesh (45 microns), the sintering can be carried out at a heating rate of about 5 ° C. per minute for about 1 hour at 815 torr at a temperature of 1235 ° C. in an atmosphere of 50% by volume hydrogen / 50% by volume argon. Can be.

The manufacture of a mold segment of a gas permeable EPS bead mold segment according to a preferred method embodiment of the present invention will now be described. First, a three-dimensional electronic image of a mold segment is formed into a CAD file, and then converted into an STL format file. Next, an array of blind vents included in the mold segment is formed into a CAD file of a three-dimensional electronic image. Next, the CAD file of the blind vent array is converted into an STL format file.

Those skilled in the art will understand that in forming each of the mold segment CAD file and the blind vent CAD file, it is necessary to adjust the CAD segment of the mold segment and the blind vent CAD file to account for dimensional changes such as shrinkage that may occur during subsequent sintering steps. will be. For example, to compensate for shrinkage, a cylindrical blind vent with a final diameter of 0.046 cm can be configured to print to a diameter of 0.071 cm. The two STL format files are compared to ensure that the individual blind vents are in the desired position in the mold segment. Any desired correction or correction can be made to the STL file. The two STL format files are then combined using an appropriate software program that performs a logical operation such as a binary subtraction operation that subtracts the three-dimensional image of the blind vent from the three-dimensional image of the mold segment. An example of such a program is Magics RP software, available from Materailise NV, Robben, Belgium. Desirable corrections and corrections can also be made to remove the blind vents in the final electronic image, such as unwanted areas.

The pile joining step provides a three-dimensional electronic pile of mold segments that includes an array of preferred blind vents. Conventional slicing programs can be used to convert this electronic file into another electronic file including mold segments represented by two-dimensional slices. Any errors or corrections can be made by checking the error in this electronic file, and then a 3DP processing apparatus is employed to form a printed version of the mold segment. An example of such a 3DP processing device is the ProMetal ^® Model RTS 300, commercially available from Extrude Hone Corporation, Arwin, 15642 Arn.

The method for producing an electronic image of a gas permeable mold segment available by the solid free molding process apparatus described in the previous paragraphs is only one of several methods for producing such an electronic image. The exact method used depends on the designer's judgment and includes factors such as the complexity and size of the mold segment, the size and number of blind vents, the computer processing equipment available, and the computing time available to process the electronic file or files. Will be influenced by For example, in some cases it may be quick to include a blind vent in the initial CAD file that is part of the three-dimensional electronic image of the gas permeable mold segment. In other cases, it may be desirable to eliminate the comparing step before combining the STL file of the blind vent array and the STL file of the mold segment.

The invention also includes embodiments in which the gas permeable EPS bead mold segment and the vapor chamber are of a single structure. The gas permeable mold segment portion of the unitary structure has open pores, and the gas permeability of the mold wall of the unitary structure may include one or more vents, which may be open vents or blind vents, or a combination thereof, but not necessarily It doesn't have to be that way. The vapor chamber portion of the unitary structure is impermeable to process gases used in EPS bead forming processes.

4 is a cross-sectional view of a single vapor chamber / gas permeable mold segment structure 150. The unitary structure 150 is composed of a vapor chamber portion 152 and a gas permeable mold segment portion 154. The vapor chamber portion 152 has a wall 156, which is penetrated by the coagulating liquid which makes these walls impermeable to the gases used during the EPS bead forming process. The vapor chamber portion 152 has a gas port 158 that introduces process gas into the vapor chamber cavity 160 or removes it from the vapor chamber cavity 160. The vapor chamber portion 152 also has a controllable water port 162 for injecting a water jet (not shown), which can be used to cool the gas permeable mold segment portion 154 during the molding process. A strut 164 extends between the outer side wall 159 of the vapor chamber portion and the outer side surface 166 of the mold wall 172 of the gas permeable mold segment portion. Due to the support 164, the vapor chamber 152 may reinforce the mold wall 172 against forces directed into and out of the cavity 168 during the molding process. The strut 164 is preferably an infiltrated like wall 156 for increasing strength.

The perimeter 170 of the mold wall 172 of the gas permeable mold segment portion 154 intersects the vapor chamber portion 152. Mold wall 172 proximate circumference 170 may include some infiltrate 174 (shown as sunscreen without stippled), but mold wall 172 typically has open pores 176 (indicated by dots) Has Preferably, the mold wall 172 also includes a plurality of blind vents 178 extending from the outer surface 166 to increase the gas transmission rate provided by the openings 176. Mold wall 172 may also have one or more open vents 180 that provide additional gas transmission. However, the open vent 180 is less desirable than the blind vent 178 because the open vent 180 interferes with the continuity of the forming surface 182, resulting in surface defects in the molded article.

The invention also includes a method embodiment for producing a single vapor chamber / gas permeable mold segment structure. In these embodiments, the unitary structure is constructed by a solid free forming process. Thereafter, the single structure is sintered to reinforce the gas permeable mold segment portion to the level required for a given application. Next, the unitary structure is heated in the presence of the coagulated infiltrate while the mold wall of the gas permeable mold segment part is normally kept free of the infiltrate so that the infiltrate penetrates into the vapor chamber portion. Thereafter, the unitary structure is cooled to solidify the infiltrate. Simple machining can be employed to clean the surface or to finish the construction of a unitary structure.

In a preferred embodiment, the powders used have a particle size range of about -140 U.S. Mesh (106 micron) / + 325 U.S. The mesh (45 microns) is 316 stainless steel or 420 stainless steel, and the infiltrate is bronze, more specifically bronze containing about 90% copper and about 10% tin. However, the powder may comprise any suitable metal, ceramic, polymer or composite. Preferably, the powder is a metal selected from the group consisting of aluminum, titanium, nickel or iron, or alloys containing one or more of these metals. The infiltration material is preferably a molten metal alloy or a molten metal powder soaked, the infiltration material is a liquid below the softening point of the powder, and solidifies at a temperature higher than the highest processing temperature expected to reach a single structure during EPS bead forming. .

While only a few embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that various changes and modifications can be made to these embodiments without departing from the spirit and scope of the invention as set forth in the claims below. All US patents and US patent applications mentioned herein are incorporated herein by reference.

Claims (55)

As an article for use as a mold or mold segment, A mold wall having a molding surface and an outer surface, An open porosity formed in the mold wall and providing fluid communication between the outer surface and the forming surface, and A plurality of blind vents extending from the outer side into the mold wall Article comprising a. The article of claim 1, wherein the article is an EPS bead mold or mold segment. The article of claim 1, wherein the article is an injection mold or a mold segment. The article of claim 1, wherein the article is a vacuum forming mold or mold segment. The article of claim 1, wherein at least one blind vent of the plurality of blind vents is cylindrical in shape. The article of claim 1, wherein the blind vent of at least one of the plurality of blind vents has an end wall thickness in the range of about 10% to about 70% of the local thickness of the mold wall. The article of claim 1, wherein the end wall thickness of the blind vents ranges from about 20% to about 40% of the local thickness of the mold wall. The article of claim 1, wherein the mold wall comprises at least one selected from the group consisting of metals, ceramics, polymers and composites. The article of claim 1, wherein the mold wall comprises a metal selected from the group consisting of aluminum, titanium, nickel, iron, and alloys thereof. The article of claim 1, wherein the mold wall comprises stainless steel. The article of claim 10, wherein the stainless steel is selected from the group consisting of 316 stainless steel and 420 stainless steel. An article for use in forming an EPS bead comprising a unitary structure having a vapor chamber portion and a mold section, comprising: The vapor chamber portion has an outer wall that is impermeable to the EPS bead forming process gas, the mold section has a mold wall, the mold wall has a molding surface, an outer surface and open pores, and the open pores are An article for use in forming an EPS bead that provides fluid communication between an outer side and the forming side. The article of claim 12, wherein the mold wall has a plurality of blind vents extending from the outer side of the mold wall into the mold wall. 13. The article of claim 12, wherein the mold wall has at least one open vent. 13. The article of claim 12, wherein the outer wall comprises a metal selected from the group consisting of aluminum, titanium, nickel, iron and alloys thereof. The article of claim 12, wherein the outer wall comprises stainless steel. The article of claim 16, wherein the stainless steel is selected from the group consisting of 316 stainless steel and 420 stainless steel. The article of claim 12, wherein the outer wall comprises a solidified infiltrant material. 19. The article of claim 18, wherein the solidifying infiltrate comprises bronze. 13. The article of claim 12, further comprising at least one strut extending between the outer wall and the mold wall. A method of making an article for use as a mold or mold segment, Forming a mold wall having open pores, wherein the open pores provide fluid communication between the outer surface of the mold wall and the forming surface of the mold wall; A blind vent forming step of forming a plurality of blind vents into the outer side How to include. 22. The method of claim 21, wherein forming the mold wall comprises machined the mold wall from a sintered material. 22. The method of claim 21, wherein forming the mold wall comprises producing the mold wall by powder metallurgy. 22. The method of claim 21, wherein forming the plurality of blind vents comprises machining at least one blind vent of the plurality of blind vents into the outer side. 22. The method of claim 21, wherein forming the mold wall comprises producing the mold wall using a solid free-form fabrication. 27. The method of claim 25, wherein the solid freeform process comprises a 3DP process. 27. The method of claim 25, wherein the solid free forming process comprises an SLS process. 27. The method of claim 25, wherein the solid free forming process produces a bonded mold wall and the method further comprises a sintering step of sintering the bonded mold wall at an elevated temperature. 27. The method of claim 25, wherein the solid free forming process comprises forming the mold wall using a metal powder selected from the group consisting of metals, ceramics, polymers and composites. 27. The method of claim 25, wherein the solid free forming process comprises forming the mold wall using a metal powder selected from the group consisting of aluminum, titanium, nickel, iron, and alloys thereof. The method of claim 25, wherein the solid free forming process comprises forming the mold wall using stainless steel powder. 32. The method of claim 31, wherein the stainless steel powder is selected from the group consisting of 316 stainless steel and 420 stainless steel. 27. The method of claim 25, wherein the solid free forming process comprises forming the mold wall using a powder having a particle size of about 45 microns to about 106 microns. 22. The method of claim 21, wherein at least one blind vent of the plurality of blind vents is cylindrical in shape. The method of claim 21, wherein the blind vent of at least one of the plurality of vents has an end wall thickness ranging from about 10% to about 70% of the local thickness of the mold wall. 22. The method of claim 21, wherein the end wall thickness of the blind vents ranges from about 20% to about 40% of the local thickness of the mold wall. A method of making an article for use in forming EPS beads, comprising a unitary structure having a vapor chamber portion and a mold section, the method comprising: Manufacturing a preform of the unitary structure by a solid freeform process. 38. The method of claim 37, further comprising sintering the preform at an elevated temperature. 39. The method of claim 38, further comprising a coagulation liquid penetrating step of permeating coagulant liquid to the outer wall of the vapor chamber portion. 40. The method of claim 39 further comprising a coagulation step of coagulating the infiltrated coagulation liquid. 40. The method of claim 39, wherein the coagulating solution comprises fused bronze. 38. The mold wall of claim 37, wherein the mold section includes a mold wall, the mold wall having an outer surface, a molding surface, and openings, wherein the openings are formed between an outer surface of the mold wall and the molding surface of the mold wall. Providing fluid communication. 43. The method of claim 42, wherein the step of manufacturing the preform includes forming a plurality of blind vents on the outer side of the mold wall. 44. The method of claim 43, wherein at least one blind vent of the plurality of blind vents is cylindrical in shape. 44. The method of claim 43, wherein at least one blind vent of the plurality of blind vents has an end wall thickness in the range of about 10% to about 70% of the local thickness of the mold wall. 44. The method of claim 43, wherein the end wall thickness of the blind vent is in the range of about 20% to about 40% of the local thickness of the mold wall. 43. The method of claim 42, wherein the step of manufacturing the preform includes forming at least one open vent through the mold wall. 43. The method of claim 42, wherein the article has at least one strut extending between the outer wall and the mold wall. 43. The method of claim 42, wherein the solid free forming process comprises fabricating the mold wall using at least one powder selected from the group consisting of metals, ceramics, polymers or composites. 43. The method of claim 42, wherein the solid free forming process comprises fabricating the mold wall using a metal powder selected from the group consisting of aluminum, titanium, nickel, iron and alloys thereof. 43. The method of claim 42, wherein the solid free forming process comprises producing the mold wall using stainless steel powder. The method of claim 51, wherein the stainless steel powder is selected from the group consisting of 316 stainless steel and 420 stainless steel. 43. The method of claim 42, wherein the solid free forming process comprises producing the mold wall using a powder having a particle size of about 45 microns to about 106 microns. 38. The method of claim 37, wherein the solid free forming process comprises a 3DP process. 38. The method of claim 37, wherein the solid free forming process comprises an SLS process.

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