WO2005107988A1

WO2005107988A1 - One-piece co-injection housing for a co-injection apparatus

Info

Publication number: WO2005107988A1
Application number: PCT/US2004/011090
Authority: WO
Inventors: Peter F. Bemis; Brett E. Weavers; Daniel Cykana; Brian D. Hemb
Original assignee: Bemis Manufacturing Company
Priority date: 2004-04-09
Filing date: 2004-04-09
Publication date: 2005-11-17

Abstract

A one-piece co-injection housing for use with a co-injection molding apparatus includes a first channel through which material may flow and a second channel through which material may flow. The second channel includes a first portion radially offset from a longitudinal axis of the housing and substantially parallel with the longitudinal axis, an oblique second portion in communication with the first channel, and an elbow-shaped portion communicating the first portion and the oblique second portion. The elbow-shaped portion provides a transition from the first portion to the oblique second portion.

Description

ONE-PIECE CO-INJECTION HOUSING FOR A CO-INJECTION APPARATUS

Field of the Invention The invention relates to an injection molding apparatus, and more particularly, a co- injection apparatus.

Background of the Invention A co-injection apparatus injects two different materials, typically an inner-core material and an outer-skin material, into a mold cavity. A co-injection manifold receives material, usually plastic, from two different injection units and combines or merges the two materials into a single stream that flows into a mold cavity of a die. The co-injection manifold, and the co-injection nozzle housed therein, are located between injection units and the single or multi-cavity mold cavity. A typical co-injection manifold is fixed to the injection units. In order to produce end-products having high structural integrity, it is desirable that a uniform, even flow of each material be distributed into the mold cavity. To achieve such a distribution into the mold cavity, an even flow of each material through the co-injection manifold is also desirable. When using more conventional apparatus and methods, irregularities (e.g., discoloration, etc.) maybe introduced into the end products by uneven flow of the materials through the co-inj ection manifold or by material burning in the manifold. As a result, a large number of end products may need to be scrapped.

Summary of the Invention The present invention may provide, in one aspect, a one-piece co-injection housing for use with a co-injection molding apparatus. The housing may include a first channel through which material may flow and a second channel through which material may flow. The second channel may includes a first portion radially offset from a longitudinal axis of the housing and substantially parallel with the longitudinal axis, an oblique second portion in communication with the first channel, and an elbow-shaped portion communicating the first portion and the oblique second portion. The elbow-shaped portion may provide a transition from the first portion to the oblique second portion. The present invention may provide, in another aspect, a method of manufacturing a one-piece co-injection housing for use with a co-injection molding apparatus. The method may include positioning an elbow-shaped end portion of a first electrode into a first passageway of the housing and at least partially into a second passageway of the housing. The first passageway is substantially parallel with a longitudinal axis of the housing. The method may also include applying an electrical current through the first electrode and the housing to erode an elbow shape into at least a portion of the first passageway and at least a portion of the second passageway, positioning a tapered end portion of a second electrode into the second passageway, and applying an electrical current through the second electrode and the housing to erode a tapered shape into the second passageway. The present invention may provide, in yet another aspect, a method of improving flow through a co-injection molding apparatus. The method may include providing a one-piece co-injection housing for receiving at least two separate streams of material and discharging a single stream of material, forming a first passageway into a first end of the housing along a first axis substantially parallel with a longitudinal axis of the housing, forming a second passageway into a second end of the housing along an oblique axis relative to the longitudinal axis, and forming an elbow shape into at least a portion of the first passageway and the second passageway for communication therebetween. The elbow shape may provide a transition from the first passageway to the second passageway. Other features and aspects of the present invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings.

Brief Description of the Drawings In the drawings, wherein like reference numerals indicate like parts: FIG. 1 is a schematic of a co-injection apparatus incorporating a one-piece co- injection housing of the present invention. FIG. 2 is an enlarged cross-sectional view of a portion of the one-piece co-injection housing of FIG. 1. FIG. 3 is a cross-sectional view of a co-injection housing similar to that of FIG. 1, illustrating rough-cut passageways formed in the housing. FIG. 4a is a side view of a first electrode having an elbow-shaped end portion. FIG. 4b is an enlarged side view of a portion of the elbow-shaped end portion of the first electrode of FIG. 4a. FIG. 5 is a side view of a second electrode having a tapered end portion. FIG. 6 is a cross-sectional view of the housing of FIG. 3, illustrating the elbow- shaped end portion of the first electrode being positioned in a first passageway of the housing to modify the first passageway. FIG. 7 is a cross-sectional view of the housing of FIG. 1, illustrating the tapered end portion of the second electrode positioned in a second passageway of the housing, after the second electrode has modified the second passageway. Before any features of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including", "having", and "comprising" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of letters to identify elements of a method or process is simply for identification and is not meant to indicate that the elements should be performed in a particular order.

Detailed Description FIG. 1 illustrates a co-injection apparatus 10 including first and second injection units 14, 18, a co-injection manifold 22, and a co-injection housing 26. The first and second injection units 14, 18 are operable to inject respective first and second channels 30, 34 in the co-injection manifold 22 with flowable material (e.g., plastic) for transport to the co-injection housing 26, in which the separate streams of material (e.g., A material and B material) are consecutively or concurrently injected. More particularly, the A material and B material may be injected together. Alternatively, the A material may be injected followed by the B material, and, optionally, followed by the A material. FIG. 1 also illustrates a die 38 containing a mold cavity 42 in fluid communication with the co-injection housing 26. A single stream of material is discharged from the co-injection housing 26 into the mold cavity 42 to form an end product. In the illustrated construction, the co-injection housing 26 includes a first or "core" channel 46 for transporting core material to the mold cavity 42 and a second or "skin" channel 50 for transporting skin material to the mold cavity 42. Other variations will be understood in the art. The skin channel 50 is in communication with the core channel 46 toward an outlet end of the co-injection housing 26, such that the skin material is allowed to combine or merge with the core material upon exiting the co-injection housing 26. As such, the housing 26 may be defined as the portion of the co-injection apparatus 10 in which the skin channel 50 merges or combines with the core channel 46. FIG. 1 further illustrates an optional end cap 54 including a diverging passageway 58 for transporting the materials to the mold cavity 42. The illustrated co-injection housing 26 does not utilize a nozzle member, like the co- injection housing disclosed in U.S. Patent No. 5,650,178 and U.S. Patent No. 5,891,381, the entire contents of both of which are incorporated herein by reference. Also, the illustrated co-injection housing 26 does not utilize a pin to regulate the flow of material into the mold cavity 42, like the co-injection housing disclosed in PCT Patent Application Publication No. WO 01/64418, the entire contents of which are incorporated herein by reference.

Alternatively, the co-injection housing 26 of the present invention may be configured to include a nozzle member and/or a pin, and therefore, to be utilized with the co-injection apparatuses shown in U.S. Patent No. 5,650,178, U.S. Patent No. 5,891,381 and PCT Patent Application Publication No. WO 01/64418. The core channel 46 is formed in the housing 26 substantially co-axial with a longitudinal axis 62 of the housing 26, and may or may not include a tapered portion 66. The skin channel 50, however, generally includes a first portion or a first passageway 70 defining a first axis 74 radially offset from and substantially parallel to the longitudinal axis 62, and a second portion or a second passageway 78 defining an oblique axis 82 relative to the longitudinal axis 62. In the illustrated co-injection housing 26, the oblique axis 82 and the longitudinal axis 62 define therebetween an angle A of about 35 degrees. However, in alternate constructions of the co-injection housing 26, the oblique axis 82 and the longitudinal axis 62 may define therebetween an angle A less than 35 degrees or an angle A greater than 35 degrees. With reference to FIGS. 1 and 2, the second passageway 78 may include a tapered shape, such that the second passageway 78 tapers or converges as the second passageway 78 approaches and merges with the core channel 46. In the illustrated construction of the co- injection housing 26, the second passageway 78 includes a taper angle or a draft angle B of about 5 degrees. However, in alternate constructions of the co-injection housing 26, the second passageway 78 may include a draft angle B less than 5 degrees or a draft angle B greater than 5 degrees. With reference to FIG. 2, the skin channel 50 further includes an elbow-shaped portion 86 communicating the first and second passageways 70, 78. In the illustrated construction, the elbow-shaped portion 86 defines an outer radius R_oU of about 0.7 inches and an inner radius R_m of about 0.17 inches. However, in alternate constructions of the co- injection housing 26, the elbow-shaped portion 86 may define an outer radius R_oUt less than 0.7 inches or an outer radius R_oU greater than 0.7 inches. Also, in alternate constructions of the co-injection housing 26, the elbow-shaped portion 86 may define an inner radius R_m less than 0.17 inches or an inner radius Rj_n greater than 0.17 inches. Further, the elbow-shaped portion 86 may be defined by compound curves, second order curves, third order curves, and so forth. The elbow-shaped portion 86 provides a smooth transition for the skin material as it is transported from the first passageway 70 to the second passageway 78. Such a smooth transition, for example, may decrease, and even substantially decrease, turbulence in the skin channel 50 compared to a co-injection housing (not shown) not having the elbow-shaped portion (e.g., the co-injection housing disclosed in PCT Patent Application Publication No. WO 01/64418). Increased turbulence in the skin channel may lead to non-uniform temperatures throughout the flow of the skin material in the skin channel. Non-uniform temperatures can cause material to burn, which results in irregularities in the end product. This affects the aesthetics of the end product. Alleviating the turbulence may decrease irregularities in the end products formed in the mold cavity. Thus, less end products may need to be scrapped due to the irregularities. The co-injection housing 26 of the present invention is formed as one piece by a method of the present invention, which will be discussed in more detail below. Forming the co-injection housing 26 as one piece alleviates seams in the core and skin channels 46, 50. In other words, channels 46, 50 may be formed without splitting the co-injection housing 26 into multiple sections or pieces that are later connected. Conventional co-injection housings are formed by splitting the co-injection housing into multiple pieces and later re-connecting the pieces, thereby forming internal channels having seams. Seal rings corresponding with the internal channels are also positioned between adjacent pieces to help prevent leakage of material through the seams. During operation of a conventional co-injection apparatus having a co-injection housing, however, material flowing through the internal channels of the housing can sometimes accumulate in the seams. As a result, the accumulated material may be exposed to high temperatures for a relatively long period of time, which may burn or degrade the accumulated material. Such burned or degraded material may become jarred from the seam in which it had accumulated, and discharged from the co-injection housing into the mold cavity. The resulting end product may need to be scrapped because of the irregularity caused by the burned or degraded material. The methods of the present invention form core and skin channels 46, 50 in the housing 26 without seams, thereby substantially eliminating regions in the channels 46, 50 in which material may accumulate. FIG. 3 shows the one-piece co-injection housing 26 with the finished core channel 46 and a rough-cut or unfinished skin channel 90. The finished core channel 46 may be provided in the co-injection housing 26 using conventional methods. However, the core channel 46 may also be provided in the housing 26 using the method of the present invention as applied to the unfinished skin channel 90. As shown in FIG. 3, the unfinished skin channel 90 is initially formed in the housing 26 by multiple boring or drilling processes. For example, a conventional drill bit may be used to form a rough-cut or unfinished first passageway 94 by boring a blind hole in one end of the housing 26. Then, a conventional drill bit may be used to form a rough-cut or unfinished second passageway 98 by boring a hole in an opposite end of the housing 26. The unfinished second passageway 98, as previously discussed, may be bored at an oblique angle with respect to the longitudinal axis 62 such that the unfinished second passageway 98, at one end, communicates with the core channel 46 and, at the other end, communicates with the unfinished first passageway 94. At the intersection of the unfinished first and second passageways 94, 98, the drilling processes yield one or more sharp edges 102 or burrs in the unfinished skin channel 90. Such sharp edges 102 or burrs may provide a region in which material can accumulate and burn. FIG. 4a shows a first electrode 106 having a body 110 and an elbow-shaped end portion 114. The first electrode 106 may be used in combination with a 3-axis CNC EDM machine (not shown), such as aROBOFORM 54/55 manufactured by Charmilles Technologies of Lincolnshire, IL, to erode an elbow shape into at least a portion of the unfinished first passageway 94 and at least a portion of the unfinished second passageway 98, thereby substantially removing the sharp edges 102 or burrs left over from the drilling processes. As understood by those of ordinary skill in the art, the EDM machine generates a current through the first electrode 106 and the housing 26 to erode material in the path of the first electrode 106. FIG. 4b shows the elbow-shaped end portion 114 of the first electrode 106. During the erosion process, as understood by those of ordinary skill in the art, the shape of the electrode 106 dictates the shape of the eroded surface. As such, the elbow-shaped end portion 114 of the first electrode 106 defines an outer radius Ro_ut of about 0.7 inches to erode an outer radius R_oUt of about 0.7 inches into at least a portion of the unfinished first and second passageways 94, 98. The elbow-shaped end portion 114 also defines an inner radius R;_n of about 0.17 inches to erode an inner radius Rj_n of about 0.17 inches into at least a portion of the unfinished first and second passageways 94, 98. Alternatively, the elbow- shaped end portion 114 may define an outer radius R_out less than 0.7 inches or an outer radius R_out greater than 0.7 inches to erode an outer radius of a corresponding dimension into at least a portion of the unfinished first and second passageways 94, 98. The elbow-shaped end portion 114 may also define an inner radius R_m less than 0.17 inches or an inner radius R_ra greater than 0.17 inches to erode an inner radius of a corresponding dimension into at least a portion of the unfinished first and second passageways 94, 98. Further, the elbow-shaped end portion 114 of the first electrode 106 may be defined, in whole or in part, by compound curves, second order curves, third order curves, and so forth to erode a corresponding shape into at least a portion of the unfinished first and second passageways 94, 98. Alternatively, the elbow-shaped end portion 114 may erode an elbow shape substantially in either of the first passageway 94 or the second passageway 98. To form the elbow shape into at least a portion of the unfinished first and second passageways 94, 98, the co-injection housing 26 is secured on the EDM machine and the first electrode 106 is tooled on the EDM machine for movement with respect to the housing 26. Alternatively, other EDM machines may be configured such that the first electrode 106 is fixed, and the co-injection housing 26 is tooled on the EDM machine for movement with respect to the first electrode 106. The elbow-shaped end portion 114 may initially be inserted into the unfinished first passageway 94 along the first axis 74 to a predetermined depth into the housing 26. While the first electrode 106 is inserted along the first axis 74, the first electrode 106 may erode a small amount of material from the unfinished first passageway 94 or substantially no material from the unfinished first passageway 94. This may occur if the diameter of the first electrode 106 is undersized with respect to the diameter of the unfinished first passageway 94. Alternatively, the diameter of the first electrode 106 may be oversized with respect to the diameter of the unfinished first passageway 94 such that substantially more material is eroded. As shown in FIG. 6, the elbow-shaped end portion 114 is positioned in the proximity of the intersection of the unfinished first and second passageways 94, 98, or adjacent the sharp edges 102. The EDM machine may then cycle the first electrode 106 through a three- dimensional orbital cycle, in which the elbow-shaped end portion 114 is cycled simultaneously in a first direction along the first axis 74, in a second direction along a second axis 118 contained within a plane 122 substantially perpendicular to the first axis 74, and in a third direction along a third axis (going into the page, indicated by arrow flag or "x" 126) contained within the plane 122. The first axis 74, second axis 118, and third axis 126 may be substantially perpendicular to each other, thus correlating with an x-axis, y-axis, and a z-axis, respectively, utilized by the EDM machine. Such a three-dimensional orbital cycling of the elbow-shaped end portion 114 sufficiently erodes the sharp edges 102 or burrs left over from the drilling processes, and forms the elbow-shaped end portion 114 into at least a portion of the unfinished first passageway 94 and at least a portion of the unfinished second passageway 98. The three- dimensional orbital cycle of the elbow-shaped end portion 114 may continue until a radial clearance Ri of about 0.040 inches is eroded between the elbow-shaped end portion 114 of the first electrode 106 (when the first electrode 106 is aligned with the first axis 74) and the finished elbow-shaped portion 86 of the skin channel 50. Alternatively, the three- dimensional orbital cycle of the elbow-shaped end portion 114 may continue until a radial clearance R less than 0.040 inches or a radial clearance R₁ greater than 0.040 inches is eroded between the elbow-shaped end portion 114 of the first electrode 106 (when the first electrode 106 is aligned with the first axis 74) and the finished elbow-shaped portion 86 of the skin channel 50. FIG. 5 shows a second electrode 130 having a tapered end portion 134. Like the first electrode 106, the second electrode 130 may be used in combination with the EDM machine to erode a tapered shape into the unfinished second passageway 98. During the erosion process, as previously discussed, the shape of the electrode dictates the shape of the eroded surface. As such, the tapered end portion 134 of the second electrode 130 defines a tapered shape or draft angle B of about 5 degrees to erode a tapered shape or draft angle B of about 5 degrees into the unfinished second passageway 98. Alternatively, the tapered end portion may define a tapered shape or draft angle B less than 5 degrees or a draft angle B greater than 5 degrees to erode a tapered shape or draft angle of a corresponding dimension into the unfinished second passageway 98. Further, the tapered end portion 134 of the second electrode 130 may be defined, in whole or in part, by compound curves, second order curves, third order curves, and so forth to erode a corresponding shape into the unfinished second passageway 98. To form the tapered shape into the unfinished second passageway 98, the co-injection housing 26 is secured on the EDM machine and the second electrode 130 is tooled on the EDM machine for movement with respect to the housing 26. Alternatively, other EDM machines may be configured such that the second electrode 130 is fixed, and the co-injection housing 26 is tooled on the EDM machine for movement with respect to the second electrode 130. The tapered end portion 134 may initially be inserted into the unfinished second passageway 98 along the oblique axis 82 to a predetermined depth into the housing 26. While the second electrode 130 is inserted along the oblique axis 82, the second electrode 130 may erode a small amount of material from the unfinished second passageway 98 or substantially no material from the unfinished second passageway 98. This may occur if the diameter of the second electrode 130 is undersized with respect to the diameter of the unfinished second passageway 98. Alternatively, the diameter of the second electrode 130 may be oversized with respect to the diameter of the unfinished second passageway 98 such that substantially more material is eroded. FIG. 7 shows the tapered end portion 134 being positioned in the unfinished second passageway 98. The EDM machine may then cycle the second electrode 130 through a two- dimensional orbital cycle, in which the tapered end portion 134 is cycled simultaneously in a second direction along a second axis 138 contained within a plane 142 substantially perpendicular to the oblique axis 82, and in a third direction along a third axis (going into the page, indicated by arrow flag or "x" 146) contained within the plane 142. However, the EDM machine does not cycle the tapered end portion 134 in a first direction along the oblique axis 82. The oblique axis 82, second axis 138, and third axis 146 maybe substantially perpendicular to each other, thus correlating with an x-axis, y-axis, and a z-axis, respectively, utilized by the EDM machine. Such a two-dimensional orbital cycling of the tapered end portion 134 sufficiently erodes the tapered shape into the unfinished second passageway 98. The two-dimensional orbital cycle of the tapered end portion 130 may continue until a radial clearance R₂ of about 0.120 inches is eroded between the widest portion of the tapered end portion 134 of the second electrode 130 (when the second electrode 130 is aligned with the oblique axis 82) and the finished second passageway 78. Alternatively, the two-dimensional orbital cycle of the tapered end portion 134 may continue until a radial clearance R₂ less than 0.120 inches or a radial clearance R₂ greater than 0.120 inches is eroded between the widest portion of the tapered end portion 134 of the second electrode 130 (when the second electrode 130 is aligned with the oblique axis 82) and the finished second passageway 78.

Claims

Claims 1. A one-piece co-injection housing for use with a co-injection molding apparatus, the housing comprising: a first channel through which material may flow; a second channel through which material may flow, the second channel comprising a first portion radially offset from a longitudinal axis of the housing and substantially parallel with the longitudinal axis; an oblique second portion in communication with the first channel; and an elbow-shaped portion communicating the first portion and the oblique second portion, the elbow-shaped portion providing a transition from the first portion to the oblique second portion, the housing being one-piece.

2. The one-piece co-injection housing of claim 1, wherein at least one of the first and second channels are formed without seams and without seal rings.

3. The one-piece co-injection housing of claim 1, wherein the elbow-shaped portion substantially prevents burning of material flowing through the second channel compared to a co-injection housing not having the elbow-shaped portion.

4. The one-piece co-injection housing of claim 1, wherein the oblique second portion is substantially tapered.

5. A method of manufacturing a one-piece co-injection housing for use with a co-injection molding apparatus, the method comprising: applying an electrical current through a one-piece housing to erode an elbow shape into a first passageway and at least a portion of a second passageway in the housing; and

6. The method of claim 5, further comprising positioning an elbow-shaped end portion of a first electrode into the first passageway and at least partially into the second passageway to erode the elbow shape.

7. The method of claim 6, wherein positioning the elbow-shaped end portion of the first electrode includes cycling the elbow-shaped end portion in a first direction along a first axis defined by the first passageway; cycling the elbow-shaped end portion in a second direction along a second axis contained within a plane substantially perpendicular to the first axis; and cycling the elbow-shaped end portion in a third direction along a third axis contained within the plane.

8. The method of claim 7, wherein the first axis, the second axis, and the third axis are substantially perpendicular to each other, and wherein cycling the elbow-shaped end portion in the first direction, the second direction, and the third direction occurs substantially simultaneously. y . i ne metnod. ot claim o, rurther comprising: moving the elbow-shaped end portion in a first direction along a first axis defined by the first passageway; and applying an electric current through the first electrode to erode at least a portion of the first passageway while moving the elbow-shaped end portion in the first direction.

10. The method of claim 5, further comprising: positioning a tapered end portion of a second electrode into the second passageway; and applying an electrical current through the housing to erode a tapered shape into the second passageway.

11. The method of claim 10, wherein positioning the tapered end portion of the second electrode includes cycling the tapered end portion in a second direction along a second axis contained within a plane substantially perpendicular to an oblique axis defining the second passageway; and cycling the tapered end portion in a third direction along a third axis contained within the plane.

12. The method of claim 11, wherein the second axis and the third axis are substantially perpendicular to each other, and wherein cycling the tapered end portion in the second direction and the third direction occurs substantially simultaneously. 1 i . 1 he method of claim 1 υ, further comprising: moving the tapered end portion in a direction along an oblique axis defining the second passageway; and applying an electric current through the second electrode to erode at least a portion of the second passageway while moving the tapered end portion along the oblique axis.

14. The method of claim 5, further comprising: drilling the first passageway into the housing; and drilling the second passageway into the housing along an oblique axis relative to a longitudinal axis of the housing to intersect the first passageway.

15. A method of improving flow through a co-injection molding apparatus, the method comprising: providing a one-piece co-injection housing for receiving at least two separate streams of material and discharging a single stream of material; forming a first passageway in the housing along a first axis substantially parallel with a longitudinal axis of the housing; forming a second passageway in the housing along an oblique axis relative to the longitudinal axis; and forming a smooth transition from the first passageway to the second passageway.

16. The method of claim 15, wherein forming a first passageway includes drilling the first passageway, and wherein forming the second passageway includes drilling the second passageway.

17. The method of claim 15, wherein the smooth transition includes an elbow shape and forming the smooth transition includes positioning an elbow-shaped end portion of a first electrode into the first passageway and at least partially into the second passageway; and applying an electrical current through the first electrode to erode the elbow shape into at least a portion of the first passageway and at least a portion of the second passageway.

18. The method of claim 17, wherein positioning the elbow-shaped end portion of the first electrode includes cycling the elbow-shaped end portion in a first direction along the first axis; cycling the elbow-shaped end portion in a second direction along a second axis contained within a plane substantially perpendicular to the first axis; and cycling the elbow-shaped end portion in a third direction along a third axis contained within the plane.

19. The method of claim 15, further comprising forming a tapered shape into the second passageway.

20. The method of claim 19, wherein forming the tapered shape includes positioning a tapered end portion of a second electrode into the second passageway; and applying an electric current through the second electrode to erode the tapered shape into the second passageway.

21. The method of claim 20, wherein positioning the tapered end portion of the second electrode includes cycling the tapered end portion in a second direction along a second axis contained within a plane substantially perpendicular to the oblique axis; and cycling the tapered end portion in a third direction along a third axis contained within the plane.

22. The method of claim 15, wherein the smooth transition substantially prevents burning of material flowing through the first and second passageways.

23. The method of claim 22, wherein the smooth transition enhances the aesthetics of parts made by the method.

24. The method of claim 18, wherein forming the first and second passageways occurs without seams and without seal rings.