WO2020160848A1

WO2020160848A1 - A method of cold forming an outer arm of a rocker arm assembly

Info

Publication number: WO2020160848A1
Application number: PCT/EP2020/025055
Authority: WO
Inventors: Michael HALSMER; Vinod Kumar MANNARU; Matthew Vance
Original assignee: Eaton Intelligent Power Limited
Priority date: 2019-02-07
Filing date: 2020-02-07
Publication date: 2020-08-13
Also published as: EP3921098A1; CN113438991A; US20210362214A1

Abstract

A method of cold forming an outer arm of a rocker arm assembly in a cold forming machine includes providing a slug having a first end and a second end, extruding the slug at the first end to establish two different widths of the slug, compressing the slug to form an upper angled surface and a lower angled surface at the second end, and compressing the slug to form an inner arm window defined by a pair of side walls and a pair of end walls.

Description

A METHOD OF COLD FORMING AN OUTER ARM

OF A ROCKER ARM ASSEMBLY

FIELD

[0001] The present disclosure relates generally to rocker arms for internal combustion engines and, more particularly, to cold, warm, and hot forming outer arms for rocker arm assemblies.

BACKGROUND

[0002] Switching rocker arms have been used to alter the operation and performance of internal combustion engines. For example, specialized rocker arms may be used to provide variable valve actuation (VVA) such as variable valve lift (WL) and cylinder deactivation (CDA). Such mechanisms are developed to improve performance, fuel economy, and/or reduce emissions of the engine. Several types of the VVA rocker arm assemblies include an inner rocker arm within an outer rocker arm that are biased together with torsion springs.

[0003] Switching rocker arms allow for control of valve actuation by alternating between latched and unlatched states. A latch, when in a latched position causes both the inner and outer rocker arms to move as a single unit. When unlatched, the rocker arms are allowed to move independent of each other. In some circumstances, these arms can engage different valve lift profiles, such as low-lift, high-lift, and no-lift (or lost motion). Mechanisms are required for switching rocker arm modes in a manner suited for operation of internal combustion engines.

[0004] The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. SUMMARY

[0005] In one aspect, a method of cold forming an outer arm of a rocker arm assembly in a cold forming machine is provided. The method includes providing a slug having a first end and a second end, extruding the slug at the first end to establish two different widths of the slug, compressing the slug to form an upper angled surface and a lower angled surface at the second end, and compressing the slug to form an inner arm window defined by a pair of side walls and a pair of end walls.

[0006] In addition to the foregoing, the described method may include one or more of the following features: rotating the slug approximately 90° between extruding the slug and compressing the slug to form the upper and lower angled surfaces; wherein the step of extruding the slug at the first end includes providing a punch force substantially along a longitudinal axis of the slug; and wherein the step of compressing the slug to form the upper and lower angled surfaces includes providing a punch force substantially orthogonal to the longitudinal axis.

[0007] In addition to the foregoing, the described method may include one or more of the following features: compressing the slug to form the second end with a pivot body including an interfacing seat configured to engage a hydraulic lash adjuster, wherein the first end is configured to engage an engine valve; punching the slug to remove a bottom wall of the slug to further form the inner arm window; forming at least one pair of axle holes in the pair of side walls; wherein the slug is heated and warm or hot formed prior to cold forming; and wherein the providing a slug includes shearing wire to a desired length to form the slug.

[0008] In one aspect, method of cold forming an outer arm of a rocker arm assembly using a cold forming machine having six forming stations is provided. The method includes shearing wire to a desired length to form a slug having first and second ends, at the first forming station, extruding the slug and flattening the first end, and at the second forming station, compressing the slug to form the second end with an upper angled surface and a lowered angled surface. The method further includes at the third forming station, compressing the slug to form an inner arm window defined by a pair of side walls, a pair of end walls, and a bottom wall, at the fourth forming station, compressing the slug to form the second end with a pivot body including an interfacing seat configured to interface with a hydraulic lash adjuster, at the fifth forming station, punching the slug to remove the bottom wall, and at the sixth forming station, forming the slug to final workpiece dimensions.

[0009] In addition to the foregoing, the described method may include one or more of the following features: wherein the forming the slug to final workpiece dimensions includes forming a first pair of axle holes in the pair of side walls; wherein the forming the slug to final workpiece dimensions further includes forming a second pair of axle holes in the of side walls; heating the slug prior to the first forming station; warm or hot forming the slug in the first, second, third, and fourth forming stations, and cold forming the slug in the remaining forming stations; and a seventh forming station where the slug is cooled and coined after the fourth forming station and before the fifth forming station.

[0010] In addition to the foregoing, the described method may include one or more of the following features: rotating the slug approximately 90° between the first forming station and the second forming station; wherein the first forming station provides a punch force substantially along a longitudinal axis of the slug; wherein the second forming station provides a compressing force substantially orthogonal to the longitudinal axis; wherein the third forming station provides a compressing force substantially orthogonal to the longitudinal axis; and wherein the second forming station, the third forming station, the fifth forming station, and the sixth forming station each provide a compressive force substantially orthogonal to the longitudinal axis.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0012] FIG. 1 is a perspective view of a switching roller finger follower assembly in accordance to one example of the present disclosure;

[0013] FIG. 2 is a flow diagram illustrating an example method of forming an outer arm of the switching roller finger follower assembly shown in FIG. 1 ;

[0014] FIG. 3 is a perspective view of an example outer arm blank utilized to form the outer arm shown in FIG. 1 ;

[0015] FIGS. 4A-4F illustrate an example six-station cold forming slug progression sequence that can be used to form the cold formed outer arm blank shown in FIG. 3;

[0016] FIG. 5 is a perspective view of an example outer arm formed from the outer arm blank shown in FIG. 3 and after undergoing machining;

[0017] FIG. 6A is a top perspective view of another example outer arm blank;

[0018] FIG. 6B is a bottom perspective view of the outer arm blank shown in FIG. 6A; and [0019] FIGS. 7A-7G illustrate an example seven-station forming slug progression sequence that can be used to form the cold formed outer arm blank shown in FIG. 6A.

DETAILED DESCRIPTION

[0020] Described herein are systems and methods for forming a component of a rocker arm assembly such as, for example, an outer arm. In one example, the described components are cold formed/forged to near net shape as an alternative manufacturing process to conventional high-cost casting, thereby enabling complex metal forming with reduced overall cost. In another example, the described components are first warm or hot formed/forged and then subsequently cold formed/forged.

[0021] With reference to the figures, various methods and processes are described for forming the component (e.g., an outer arm) of a rocker arm assembly such as, for example, a switching roller finger follower (SRFF) assembly 10. In the example embodiment shown in FIG. 1 , SRFF assembly 10 generally includes an inner arm 12 and an outer arm 14. While the various methods and processes described herein are for forming the outer arm 14, it will be appreciated that such methods may be utilized to form various other parts of the rocker arm assembly such as, for example, inner arm 12.

[0022] With continued reference to FIG. 1 , SRFF assembly 10 is shown by way of example only and it will be appreciated that the outer arm employed therein may be used in various configurations of rocker arm assemblies. The default configuration is in a normal-lift (latched) position where the inner arm 12 and the outer arm 14 are locked together, causing an engine valve (not shown) to open and allowing the cylinder to operate as it would in a standard valvetrain. When a latch assembly 16 is engaged (e.g., oil from an oil control valve feeds a hydraulic lash adjuster (not shown) to engage latch assembly 16), the inner arm 12 and the outer arm 14 operate together like a standard rocker arm to open the engine valve. In a low-lift (unlatched) position, the inner arm 12 and the outer arm 14 can move independently to enable variable valve lift.

[0023] In the example embodiment, the inner arm 12 and the outer arm 14 are both mounted to a pivot axle 20, which secures the inner arm 12 to the outer arm 14 while also allowing a rotational degree of freedom pivoting about the pivot axle 20 when the SRFF assembly 10 is in a deactivated state. A lost motion torsion spring 22 is secured to the pivot axle 20 and is configured to bias the position of the inner arm 12 so that it always maintains continuous contact with a camshaft lobe (not shown).

[0024] As shown in FIG. 1 , the outer arm 14 includes a first outer side arm 30 and a second outer side arm 32. The first and second outer side arms 30, 32 each include an aperture (not shown) configured to receive a bearing axle 36 therethrough. An outer roller 38 is mounted on each end of the bearing axle 36 outboard of the first and second outer side arms 30, 32.

[0025] As illustrated, the inner arm 12 is disposed between the first outer side arm 30 and the second outer side arm 32. The inner arm 12 includes a first inner side arm 40 and a second inner side arm 42. The first and second inner side arms 40, 42 each include an aperture 44 configured to receive the bearing axle 36 therethrough. An inner roller 48 is supported by the bearing axle 36.

[0026] FIG. 2 illustrates an example method 100 of producing an outer arm for a rocker arm assembly, such as, for example, outer arm 14 described above and illustrated in FIG. 1 . In the example embodiment, the outer arm is cold formed or cold forged from a blank as a starting point to manufacture a cold-formed outer arm blank 50 (FIG. 3) or 60 (FIGS. 5 and 6) instead of a cast or metal injection molded part. As shown in FIG. 2, the method 100 includes the general steps of 1 10 cold forming the outer arm blank 50, 60 to near net shape, 120 machining the cold formed outer arm blank 50, 60, and 130 applying finishing processes such as, for example, tumble finishing, heat treatment, deburring, vibratory finishing, etc.

[0027] As used herein, the term“cold forming” is intended to encompass what is known in the art as, for example,“cold forging,”“cold heading,” and“deep drawing.” As used herein, the term“machining” means the use of a chucking machine, drilling machine, turning machine, grinding machine, broaching machine or other such machine to remove material. In other examples, one or more portions of the manufacturing methods or processes described herein include warm forming or warm forging and/or hot forming or hot forging. In one example, cold forming is a metal forming process carried out at or near room temperature, warm forming is a metal forming process carried out above the cold forming temperature but below a recrystallization temperature or transition temperature of the metal, and hot forming is a metal forming process carried out above the recrystallization temperature of transition temperature of the metal.

[0028] FIG. 3 illustrates cold formed outer arm blank 50, which may be formed in a variety of cold forming machines. Cold formed outer arm blank 50 may be utilized in a rocker arm assembly similar to that shown in FIG. 1 . Generally, cold forming machines include a cut-off station for cutting metal wire to a desired length to provide an initial workpiece (also knowns as a“slug”) and multiple progressive forming stations that include multiple spaced-apart die sections and a reciprocating gate having multiple punch sections, each of which cooperates with a respective die section to form a die cavity where the slug is punched or compressed. A conventional transfer mechanism moves the slug in successive steps from the cut-off station to each of the forming stations in a synchronized fashion and is also capable of rotating the slug (e.g., 90°) as it is being transferred from one station to another. In one embodiment shown in FIGS. 4A-4F, the cold formed outer arm blank 50 is formed in a six station cold forming machine (not shown). It will, however, be appreciated that the cold formed outer arm blank 50 can be produced in a different number of forming stations without departing from the scope of the disclosure. In another embodiment shown in FIGS. 6A-7G, a cold formed outer arm blank 60 is formed in a seven-station cold forming machine (not shown).

[0029] Illustrated in FIGS. 4A-4F is an example six-station cold forming slug progression sequence that can be used to form the cold formed outer arm blank 50. Each figure represents the state of the slug at an end-of-stroke tool position. It will be appreciated that this slug progression sequence is merely one example of a cold forming slug progression sequence and that other slug progression sequences are possible.

[0030] With reference to FIG. 4, the example progressions sequence beings with shearing wire to a desired length at a cut-off station (not shown) to provide an initial slug or workpiece 200 that generally includes a first end 202, a second end 204, and a cylindrical surface 206 extending therebetween. The workpiece 200 is then transferred to the first forming station 210 (FIG. 4A) where the first end 202 faces a die section 212 and the second end 204 faces a punch section 214. At the first forming station 210, the workpiece 200 is squared or flattened at the first end 202. In this way, the workpiece 200 is extruded to lower the forming load and eliminate folds in subsequent operations, while also initially establishing two different widths for the workpiece 200. In the example embodiment, the punch force of the first forming station 210 is driven along the centerline or longitudinal axis 216 of the workpiece 200 or substantially along the longitudinal axis 216. The workpiece 200 is then rotated 90° or approximately 90° and transferred to the second forming station (FIG. 4B) where the longitudinal axis 216 is orthogonal to or substantially orthogonal to the punch force.

[0031] At the second forming station 220 (FIG. 4B), an upper angled surface 222 and a lower angled surface 224 are formed at the second end 204. As illustrated, upper angled surface 222 is formed at an angle‘a’ relative to the longitudinal axis 216, and lower angled surface 224 is formed at an angle‘b’ relative to longitudinal axis 216. In one example, angle‘a’ parallel to or substantially parallel to a machined features such as, for example, a latch pin bore, and can be adjusted in earlier stations to ensure correct fill. Angle‘b’ is perpendicular or substantially perpendicular to a centerline of a machined feature such as, for example, an interfacing seat that mates with an FILA (not shown) and can be adjusted in earlier stations to ensure correct fill.

[0032] At the third forming station 230 (FIG. 4C), major material filling occurs and key features of outer arm 14 are incorporated therein including an inner arm window 232 defined by side walls 234, end wall 236, end wall 238, and bottom wall 240. As illustrated, end wall 236 is formed with a recess or clearance 242 defined therein.

[0033] At the fourth forming station 250 (FIG. 4D), a spring loaded tool 252 can regulate the material flow to facilitate avoiding folds, and a pivot body 254 including an interfacing seat 256 (e.g., to receive a hydraulic lash adjuster, not shown) and an upper wall 258 is further formed in the workpiece 200. At the fifth forming station 260 (FIG. 4E), the bottom wall 240 is punched or pierced and thereby removed from the workpiece 200. At the sixth forming station 270 (FIG. 4F), workpiece 200 is formed to its final dimensions including axle holes 272 formed in the side walls 234. Additionally, any potential sharp corners may be formed to create chamfers smoothing such breaks. The overall length of the workpiece 200 may be formed to the length of the outer arm blank 50. At the conclusion of the sixth forming station, the cold formed outer arm blank 50 is completed and includes all of the structural features shown in FIG. 3.

[0034] Accordingly, the cold formed outer arm blank 50 includes all of the structural features of the finished outer arm 14 described above and shown in FIG. 3, with the exception of the structural features that must be machined. To complete the method 100 of producing the finished outer arm 14, the cold formed outer arm blank 50 is machined after the cold forming to thereby form the remaining structural features as shown in FIG. 5.

[0035] With reference now to FIG. 5, the machining step 120 is performed on the completed outer arm blank 50 and features are formed therein such as, for example, axial holes 272, pivot holes 274, squirt hole 276, stop pin hole 278, back face 280, cage bore 282, latch bore 284, biasing mechanism (e.g., spring) posts 286, and an oil feed hole (not shown) extending from interfacing seat 256 to latch bore 284. It will be appreciated that these machining operations can be performed one at a time, in combination with one or more other machining operations, or all together in any sequence. As such, the outer arm 14 described above is cold formed to near net shape, including cold forming to final dimensions inner arm window 232, side walls 234, end walls 236, 238, and pivot body 254. Cold forming these features to final dimensions reduces the amount of machining otherwise required to complete a finished outer arm and thus reduces manufacturing cost of the outer arm.

[0036] In one example, the punch force produced at the first forming station 210 is between 15 tons and 35 tons or between approximately 15 tons and approximately 35 tons. In another example, the punch force produced at the first forming station 210 is 25 tons or approximately 25 tons. In one example, the punch force produced at the second forming station 220 is between 200 tons and 225 tons or between approximately 200 tons and approximately 225 tons. In another example, the punch force produced at the second forming station 220 is 212 tons or approximately 212 tons. In one example, the punch force produced at the third forming station 230 is between 650 tons and 750 tons or between approximately 650 tons and 750 tons. In another example, the punch force produced at the third forming station 230 is 679 tons or approximately 679 tons.

[0037] In one example, the punch force produced at the fourth forming station 250 is between 200 tons and 230 tons or between approximately 200 tons and 230 tons. In another example, the punch force produced at the fourth forming station 250 is 214 tons or approximately 214 tons. In one example, the punch force produced at the fifth forming station 260 is between 0.5 tons and 1 .5 tons or between approximately 0.5 tons and 1 .5 tons. In another example, the punch force produced at the fifth forming station 260 is 0.8 tons or approximately 0.8 tons. In one example, the punch force produced at the sixth forming station 270 is between 0.1 tons and 0.5 tons or between approximately 0.1 tons and 0.5 tons. In another example, the punch force produced at the sixth forming station 270 is 0.3 tons or approximately 0.3 tons.

[0038] In an alternative method of manufacture, outer arm blank 50 is formed in a seven station process (e.g., similar to FIGS. 7A-7G). In some examples, the warm or hot forging is configured to reduce load on tooling, which can reduce wear and result in longer tool life. In the example method, workpiece 200 is initially heated and warm formed or hot formed in the first forming station 210, the second forming station 220, the third forming station 230, and the fourth forming station 250. The workpiece 200 is then cooled and cold formed (coined) in a fifth forming station that is the same or similar to station 250. The workpiece is then cold formed in a sixth forming station that is the same or similar to station 260, and subsequently in a seventh forming station that is the same or similar to station 270 described above.

[0039] With reference now to FIGS. 6A-7G, in the example embodiment, warm/cold formed outer arm blank 60 is formed in a seven-station warm/cold forming machine (not shown). Warm/cold formed outer arm blank 60 may be utilized, for example, in the SRFF assembly 10 shown in FIG. 1 . It will, however, be appreciated that the formed outer arm blank 60 can be produced in a different number of forming stations without departing from the scope of the disclosure.

[0040] Illustrated in FIG. 7A-7G is an example seven-station cold forming slug progression sequence that can be used to form the warm/cold formed outer arm blank 60. Each figure represents the state of the slug at an end-of-stroke tool position. It will be appreciated that this slug progression sequence is merely one example of a warm/cold forming slug progression sequence and that other slug progression sequences are possible. For example, outer arm blank 60 may be cold formed in all stations. Further still, outer arm blank 60 may be exclusively cold formed in a six- station cold forming machine similar to that described above and shown in FIGS. 4A- 4F.

[0041] With continued reference to FIGS. 7A-7G, the example progressions sequence beings with shearing wire to a desired length at a cut-off station (not shown) and heated to provide an initial slug or workpiece 300 that generally includes a first end 302, a second end 304, and a cylindrical surface 306 extending therebetween. The workpiece 300 is then transferred to the first forming station 310 (FIG. 7A) where the first end 302 faces a die section 312 and the second end 304 faces a punch section 314. At the first forming station 310, the workpiece 300 is squared or flattened at the first end 302. In this way, the workpiece 300 is extruded to lower the forming load and eliminate folds in subsequent operations, while also initially establishing two different widths for the workpiece 300. In the example embodiment, the punch force of the first forming station 310 is driven along the centerline or longitudinal axis 316 of the workpiece 300. The workpiece 300 is then rotated 90° or approximately 90° and transferred to the second forming station 320 where the longitudinal axis 316 is orthogonal to or substantially orthogonal to the punch force.

[0042] At the second forming station 320 (FIG. 7B), an upper angled surface 322 and a lower angled surface 324 are formed at the second end 304. As illustrated, upper angled surface 322 is formed at an angle y relative to the longitudinal axis 316, and lower angled surface 324 is formed at an angle‘d’ relative to longitudinal axis 316. In one example, angle y is parallel to or substantially parallel to a machined features such as, for example, a latch pin bore, and can be adjusted in earlier stations to ensure correct fill. Angle‘d’ is perpendicular to or substantially perpendicular to an interfacing seat that mates to an HLA (not shown) and can be adjusted in earlier stations to ensure correct fill.

[0043] At the third forming station 330 (FIG. 7C), major material filling occurs and key features of the outer arm are incorporated therein including an inner arm window 332 defined by side walls 334, end wall 336, end wall 338, and bottom wall 340.

[0044] At the fourth forming station 350 (FIG. 7D), a spring loaded tool 352 can regulate the material flow to facilitate avoiding folds, and a pivot body 354 including an interfacing seat 356 (e.g., to receive a hydraulic lash adjuster, not shown) and an upper wall 358 is further formed in the workpiece 300. On the first side 302, an indentation 360 is formed configured to interface with an engine valve (not shown). At the fifth forming station 360 (FIG. 7E), the workpiece 300 is cooled and coined. At the sixth forming station 370 (FIG. 7F), the bottom wall 340 is punched or pierced and thereby removed from the workpiece 300. At the seventh forming station 380 (FIG. 7G), workpiece 300 is formed to its final dimensions including forward axle holes 372 and rearward axle holes 374 formed in the side walls 334. Additionally, any potential sharp corners may be formed to create chamfers smoothing such breaks. The overall length of the workpiece 300 may be formed to the length of the outer arm blank 60. At the conclusion of the seventh forming station, the warm/cold formed outer arm blank 60 is completed and includes all of the structural features shown in FIG. 1. The outer arm blank 60 may then machined to includes features such as a an oil feed hole in interfacing seat 356, a back face, a cage bore, and a latch bore.

[0045] The foregoing description of the examples has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular example are generally not limited to that particular example, but, where applicable, are interchangeable and can be used in a selected example, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

CLAIMS What is claimed is:

1 . A method of cold forming an outer arm of a rocker arm assembly in a cold forming machine, the method comprising:

providing a slug having a first end and a second end;

extruding the slug at the first end to establish two different widths of the slug; compressing the slug to form an upper angled surface and a lower angled surface at the second end; and

compressing the slug to form an inner arm window defined by a pair of side walls and a pair of end walls.

2. The method of claim 1 , further comprising rotating the slug approximately 90° between extruding the slug and compressing the slug to form the upper and lower angled surfaces.

3. The method of claim 1 , wherein the step of extruding the slug at the first end includes providing a punch force substantially along a longitudinal axis of the slug.

4. The method of claim 3, wherein the step of compressing the slug to form the upper and lower angled surfaces includes providing a punch force substantially orthogonal to the longitudinal axis.

5. The method of claim 1 , further comprising compressing the slug to form the second end with a pivot body including an interfacing seat configured to engage a hydraulic lash adjuster, wherein the first end is configured to engage an engine valve.

6. The method of claim 1 , further comprising punching the slug to remove a bottom wall of the slug to further form the inner arm window.

7. The method of claim 1 , further comprising forming at least one pair of axle holes in the pair of side walls.

8. The method of claim 1 , wherein the slug is heated and warm or hot formed prior to cold forming.

9. The method of claim 1 , wherein the providing a slug includes shearing wire to a desired length to form the slug.

10. A method of cold forming an outer arm of a rocker arm assembly using a cold forming machine having six forming stations, the method comprising:

shearing wire to a desired length to form a slug having first and second ends; at the first forming station, extruding the slug and flattening the first end;

at the second forming station, compressing the slug to form the second end with an upper angled surface and a lowered angled surface;

at the third forming station, compressing the slug to form an inner arm window defined by a pair of side walls, a pair of end walls, and a bottom wall;

at the fourth forming station, compressing the slug to form the second end with a pivot body including an interfacing seat configured to interface with a hydraulic lash adjuster;

at the fifth forming station, punching the slug to remove the bottom wall; and at the sixth forming station, forming the slug to final workpiece dimensions.

1 1 . The method of claim 10, wherein the forming the slug to final workpiece dimensions includes forming a first pair of axle holes in the pair of side walls.

12. The method of claim 1 1 , wherein the forming the slug to final workpiece dimensions further includes forming a second pair of axle holes in the of side walls.

13. The method of claim 10, further comprising heating the slug prior to the first forming station.

14. The method of claim 13, further comprising warm or hot forming the slug in the first, second, third, and fourth forming stations, and cold forming the slug in the remaining forming stations.

15. The method of claim 14, further comprising a seventh forming station where the slug is cooled and coined after the fourth forming station and before the fifth forming station.

16. The method of claim 10, further comprising rotating the slug approximately 90° between the first forming station and the second forming station.

17. The method of claim 10, wherein the first forming station provides a punch force substantially along a longitudinal axis of the slug.

18. The method of claim 17, wherein the second forming station provides a compressing force substantially orthogonal to the longitudinal axis.

19. The method of claim 17, wherein the third forming station provides a compressing force substantially orthogonal to the longitudinal axis.

20. The method of claim 17, wherein the second forming station, the third forming station, the fifth forming station, and the sixth forming station each provide a compressive force substantially orthogonal to the longitudinal axis.