DE112014006624B4 - PROCESS FOR FORMING AN ALUMINUM VEHICLE SIDE MEMBER - Google Patents

Abstract

A method for forming an aluminum vehicle side rail (200), comprising the following sequential steps: - extruding an aluminum tube; - longitudinally bending the extruded aluminum tube (T) to form a bend (B); - post-preforming the extruded and longitudinally bent aluminum tube longitudinal bending;- hydroforming of the extruded, longitudinally bent and preformed aluminum tube to form the vehicle side member (200), characterized in that during hydroforming an inner radius of the bend (B) is formed with a cross-sectional length of a line reduction of less than 1%.

Description

This document relates to a method for forming a vehicle side rail from aluminum tubing.

Vehicle manufacturers are implementing lighter, stronger materials, such as aluminum alloys, to meet emission reduction goals, meet fuel economy goals, reduce manufacturing costs, and reduce vehicle weight. In addition, ever more demanding safety standards must be met while reducing vehicle weight at the same time. One approach to meeting these competing interests and objectives is to hydroform high strength aluminum alloy tube blanks into strong, lightweight hydroformed parts such as vehicle roof rails and front rails.

From the KR 10 2005 0 011 285 A discloses a method of forming an aluminum side member, in which an aluminum tube is extruded, bent longitudinally, preformed, and subjected to a hydroforming process. Furthermore, be on the documents KR 10 2006 0 013 889 A and DE 103 12 028 A1 referenced, which also form relevant prior art.

It is therefore an object of the present invention to provide an improved, more efficient and more effective method for forming a vehicle side rail from aluminum.

• - Extrudieren eines Aluminiumrohrs;
• - Längs-Biegen des extrudierten Aluminiumrohrs zur Ausbildung einer Biegung;
• - Vorformen des extrudierten und längsgebogenen Aluminiumrohrs nach dem Längs-Biegen;
• - Innenhochdruckumformen des extrudierten, längsgebogenen und vorgeformten Aluminiumrohrs zu dem Fahrzeuglängsträger,

This object is achieved with a method according to patent claim 1. A method for forming a vehicle side member made of aluminum is thus proposed, comprising the following steps carried out in succession:

• - Extruding an aluminum tube;
• - longitudinally bending the extruded aluminum tube to form a bend;
• - preforming the extruded and longitudinally bent aluminum tube after longitudinal bending;
• - hydroforming of the extruded, longitudinally bent and preformed aluminum tube to form the vehicle side member,

In contrast to the prior art, in particular the KR 10 2005 0 011 285 A the method according to the invention is characterized in that during hydroforming an inner radius of the bend is formed with a cross-sectional length of a line reduction of less than 1%.

Bending can be accomplished in a rotary draw bender and preforming can be completed in a forming tool. In another possible embodiment, the bending can be accomplished in a push-pull bending tool and the preforming can be completed in a forming tool.

In another aspect, the method includes induction annealing the extruded aluminum tube prior to hydroforming to restore formability. In one possible embodiment, this induction annealing is performed after bending and before preforming the extruded aluminum tube. In a further possible embodiment, this induction annealing is carried out after the preforming and before the hydroforming of the extruded aluminum tube. In yet another embodiment, the induction annealing is complete after both bending and preforming of the extruded aluminum tube.

To describe the method more specifically, hydroforming the extruded aluminum tube into a vehicle side rail comprises positioning the bent and preformed extruded aluminum tube into a hydroforming die, wherein the hydroforming die is partially closed and the bent, preformed, extruded aluminum tube in the hydroforming die is subjected to a liquid under a first pressure level is exposed. This is followed by engaging an inside radius of a bend in the preformed, extruded aluminum tube with the hydroforming die before fully closing the hydroforming die. This serves to reduce the amount of marginal fiber stretch on the inside radius of the bend. Further, it allows forming a cross-section of non-constant radius along the inner radius of the bend, where that cross-section includes a first transition segment, a second transition segment, and an intermediate segment between the first and second transition segments. The first and second transition segments are provided with a tighter radius of curvature than the intermediate segment.

This is followed by the step of fully closing the hydroforming tool and increasing the fluid pressure level to a second level to hydroform and hydroform a portion or vehicle side rail from the bent and preformed extruded aluminum tube. In another aspect, the method includes maintaining a spacing between the hydroforming tool and the ers th and the second transition segment during hydroforming.

After hydroforming, the vehicle side member is trimmed to a specified length. This is followed by loading a plurality of hydroformed parts/singers onto a rack and heat treating a plurality of parts together to artificially age the parts and provide target strength characteristics. Thereafter, the plurality of parts are subjected to a chemical pre-treatment on the rack to provide a chemical pre-treatment to the parts after the heat treatment.

In an alternative embodiment, the parts are initially loaded onto a rack and chemically pretreated together before being subjected to a heat treatment. In each of these embodiments, the parts are held on the same rack for the heat treatment and chemical pretreatment processes.

The above aspects of this disclosure and other aspects are described in detail below with reference to the attached drawing figures.

• 1a ein Flussdiagramm, das eine mögliche Ausführungsform des aktuellen Wertstromverfahrens für das Formen eines Fahrzeuglängsträgers aus Aluminium veranschaulicht.
• 1b ein Flussdiagramm, das eine zweite mögliche Ausführungsform eines Wertstromverfahrens für das Formen eines Fahrzeuglängsträgers aus Aluminium veranschaulicht.
• 2 eine Explosionsperspektivenansicht eines Austrittsöffnungsformwerkzeugs, durch welches das Aluminiummaterial zur Ausbildung eines extrudierten Aluminiumrohrs extrudiert wird.
• 3a eine Draufsicht eines Endes einer beispielhaften Dorn-Kugel-Anordnung.
• 3b eine Querschnittsansicht der Dorn-Kugel-Anordnung von 3a , die in eine Richtung von Pfeilen 3B-3B betrachtet wird.
• 4 eine Explosionsansicht einer beispielhaften Kugel-Dorn-Anordnung.
• 5a eine Dorn-Schaft-Anordnung.
• 5b eine Explosionsansicht der in 5a gezeigten Dorn-Schaft-Anordnung.
• 6 eine Dorn-Anordnung, die eine Dorn-Schaft-Anordnung und eine Vielzahl von verbundenen Dorn-Schaft-Anordnungen umfasst.
• 7 eine Draufsicht eines Rotationszugbiegemechanismus, der ein Nachführelement, eine Klemmvorrichtung, ein Biegeformwerkzeug, einen Abstreifer und eine Dorn-Anordnung aufweist, die zum Biegen des extrudierten Aluminiumrohrs vor dem Innenhochdruckumformen verwendet werden.
• 8 eine perspektivische Ansicht, die ein extrudiertes Aluminiumrohrwerkstück veranschaulicht, das in einer Kanalwindung zu Zwecken des Induktionsglühens aufgenommen ist.
• 9 eine obere Draufsicht des extrudierten Aluminiumrohrwerkstücks, das einen A-Rahmen-Dachlängsträger veranschaulicht, wobei der A-Säulenabschnitt des A-Säulendachlängsträgers einem Induktionsglühen unterzogen wird.
• 10 eine graphische Darstellung einer T4-Gesamtausdehnung vor und nach dem Induktionsglühen von dehnbaren Probestücken, die aus dem extrudierten Rohr geschnitten und einer Vor-Dehnbeanspruchung ausgesetzt werden. Derartige Probestücke verhalten sich ähnlich wie eine A-Säulen-Dachlängsträgerreaktion und stellen eine solche dar.
• 11 eine graphische Darstellung einer T6-Härte-Überprüfung, die bestätigt, dass die A-Säulen-Dachlängsträger, die einem Induktionsglühen ausgesetzt werden, trotzdem ihre Soll-Dehngrenze nach einer T6-Wärmebehandlung erreichen.
• 12a und 12b entsprechende perspektivische und obere Draufsichten, die das Zwischensegment des Innenradius einer Biegung in dem durch Innenhochdruck umgeformten Längsträger veranschaulichen, der zur Reduzierung von Dehnbeanspruchung und zu einem Hintanhalten von Rissbildung bearbeitet worden ist.
• 13a - 13e veranschaulichen ein Drucksequenzinnenhochdruckumformen des extrudierten Aluminiumrohrs.
• 14 eine ausführliche schematische Darstellung der Querschnittslänge von Linienreduktion, die dem Längsträger während des Innenhochdruckumformens bereitgestellt wird.
• 15 eine ausführliche schematische Darstellung eines nicht-konstanten Radius des Flachansatzübergangsabschnitts.
• 16 eine perspektivische Ansicht, die ein leeres Gestell veranschaulicht, das zum Halten und chargenweise Wärmebehandeln und chemischen Vorbehandeln einer Vielzahl von Längsträgern mit den Haltearmen und Verriegelungsstangen in der die Teile aufladenden Position verwendet wird.
• 17 eine perspektivische Ansicht, die 16 ähnlich ist, jedoch die erste Reihe von Teilen/Längsträgern, die auf das Gestell geladen werden, zeigt.
• 18 eine ausführliche Ansicht, die veranschaulicht, wie die offenen Enden einer Gruppe von Teilen, in der veranschaulichten Ausführungsform Säulen- und Dachlängsträgern, in den Nasen aufgenommen sind, die auf einem Teil, der die Endplatte des Gestells verortet, bereitgestellt sind.
• 19 eine ausführliche Ansicht, die veranschaulicht, wie die Teile in den Schlitzen, Kerben oder Nuten auf dem Stützarm ruhen.
• 20 eine perspektivische Ansicht, die ähnlich 17 ist, die das Positionieren der zwei untersten Schwenk-Halte-Arme in der die Teile befestigenden Position zeigt, so dass diese direkt über den Stützarmen, welche die erste Reihe von Teilen stützen, liegen.
• 21 eine perspektivische Ansicht ähnlich zu 17 ist, die das mit 24 Teilen (Dachlängsträgern) beladene, halbe Gestell zeigt, wobei jeder Teil von (a) den zwei Stützarmen, (b) den zwei untersten Halte-Armen, (c) den nächstgelegenen zwei Halte-Armen über den untersten Halte-Armen und (d) den nächstgelegenen zwei Schwenk-Armen über diesen aufgenommen und gehalten wird. Die oberen zwei Schwenk-Halte-Arme sind über der oberen Reihe von Dachlängsträgern liegend gezeigt. Die gestuften Verriegelungsstangen sind in der untersten, der die Teile aufladenden Position gezeigt.
• 22 eine Ansicht, die 21 sehr ähnlich ist, jedoch die gestuften Verriegelungsstangen in der die Teile befestigenden Position hinein angehoben zeigt, so dass die gestuften Verriegelungsstangen das Ende von jedem Schwenk-Halte-Arm in Eingriff bringen und schließen, wodurch die Teile fest auf dem Gestell verriegelt werden.
• 23 eine detaillierte Seitenansicht, welche die unterschiedlichen Längen der Halte-Arme eindeutig zeigt, und auch wie die gestufte Verriegelungsstange mit dem Ende von jedem Arm in Eingriff ist und dieses ergreift, wenn dieser in die befestigende Position angehoben wird.
• 24 eine detaillierte perspektivische Ansicht, welche die Opfer-Sicherungslasche veranschaulicht, die in einem der unverlierbaren Lastösenbolzen aufgenommen ist, der eine Verriegelungsstange in der die Teile befestigenden Position verriegelt.
• 25 eine perspektivische Ansicht ist, die eine alternative Gestellausführungsform veranschaulicht, die mit einer Gruppe von Teilen in Form von Vorderlängsträgern beladen ist.
• 26 die Verriegelungsstange der alternativen Ausführungsform, die den Lastösenbolzen und die Sicherungslasche umfasst, veranschaulicht.
• 27 eine Endansicht der voll beladenen alternativen Ausführungsform des in 25 und 26 veranschaulichten Gestells ist.
• 28 ein schematisches Blockschaltbild einer Herstellungsanlagenproduktionsebene ist.

The accompanying drawing figures, which are incorporated herein and form a part of the specification, illustrate various aspects of the method and together with the specification serve to explain certain principles thereof. In the drawings is/are:

• 1a Figure 12 is a flow chart illustrating one possible embodiment of the current value stream method for forming an aluminum vehicle side rail.
• 1b 14 is a flowchart illustrating a second possible embodiment of a value stream method for forming an aluminum vehicle side rail.
• 2 Figure 14 is an exploded perspective view of an orifice die through which the aluminum stock is extruded to form an extruded aluminum tube.
• 3a Figure 12 is a plan view of one end of an exemplary mandrel and ball assembly.
• 3b FIG. 12 is a cross-sectional view of the mandrel and ball assembly of FIG 3a , viewed in a direction of arrows 3B-3B.
• 4 Figure 14 is an exploded view of an exemplary ball and spike assembly.
• 5a a mandrel-shank arrangement.
• 5b an exploded view of the in 5a shown mandrel-shank arrangement.
• 6 a mandrel assembly comprising a mandrel-shank assembly and a plurality of connected mandrel-shank assemblies.
• 7 Figure 14 is a plan view of a rotary draw bender mechanism including a follower, clamp, bend former, stripper and mandrel assembly used to bend the extruded aluminum tube prior to hydroforming.
• 8th 12 is a perspective view illustrating an extruded aluminum tube workpiece received in a duct coil for induction annealing purposes.
• 9 12 is a top plan view of the extruded aluminum tubing workpiece illustrating an A-frame roof rail wherein the A-pillar portion of the A-pillar roof rail is induction annealed.
• 10 Figure 12 is a plot of total T4 strain before and after induction annealing of ductile specimens cut from extruded tubing and subjected to pre-strain stress. Such specimens behave in a manner similar to and represent an A-pillar roof rail reaction.
• 11 Figure 14 is a graphical representation of a T6 hardness test confirming that A-pillar roof rails subjected to induction annealing will still achieve their target yield strength after a T6 heat treatment.
• 12a and 12b 12 are corresponding perspective and top plan views illustrating the intermediate segment of the inner radius of a bend in the hydroformed side rail that has been machined to reduce tensile stress and inhibit cracking.
• 13a - 13e illustrate a pressure sequence hydroforming of the extruded aluminum tube.
• 14 Figure 12 shows a detailed schematic of the cross-sectional length of line reduction provided to the side rail during hydroforming.
• 15 Figure 12 shows a detailed schematic of a non-constant radius of the flat neck transition section.
• 16 12 is a perspective view illustrating an empty rack used to hold and batch heat treat and chemically pretreat a plurality of side rails with the support arms and locking bars in the parts loading position.
• 17 a perspective view that 16 is similar but shows the first row of parts/singers being loaded onto the rack.
• 18 Figure 12 is a detailed view illustrating how the open ends of a group of parts, pillar and roof rails in the illustrated embodiment, are received in the lugs provided on a part locating the end plate of the frame.
• 19 a detailed view illustrating how the parts rest in the slots, notches or grooves on the support arm.
• 20 a perspective view that is similar 17 12 showing the positioning of the two lowermost pivoting support arms in the parts mounting position so that they overlie the support arms supporting the first row of parts.
• 21 a perspective view similar to 17 Figure 12 showing the half rack loaded with 24 pieces (roof rails), each piece of (a) the two support arms, (b) the two lowest support arms, (c) the nearest two support arms over the lowest supports -arms and (d) the nearest two swivel arms are picked up and held by them. The top two pivoting support arms are shown overlying the top row of roof rails. The stepped locking bars are shown in the lowest, part-loading position.
• 22 a view that 21 is very similar but showing the stepped locking bars raised in the parts mounting position so that the stepped locking bars engage and close the end of each pivoting support arm, locking the parts firmly onto the rack.
• 23 Figure 12 is a detailed side view clearly showing the different lengths of the support arms, and also how the stepped locking bar engages and grips the end of each arm as it is raised to the mounting position.
• 24 Figure 12 is a detailed perspective view illustrating the sacrificial securing tab received in one of the captive clevis pins locking a locking bar in the parts attaching position.
• 25 Figure 12 is a perspective view illustrating an alternative frame embodiment loaded with a group of parts in the form of front rails.
• 26 illustrates the latch bar of the alternative embodiment including the clevis pin and securing tab.
• 27 an end view of the fully loaded alternative embodiment of FIG 25 and 26 illustrated frame is.
• 28 Figure 12 is a schematic block diagram of a manufacturing facility production level.

Reference will now be made to 1a 1, which illustrates a first embodiment of the value stream method 10 for forming an aluminum vehicle side rail. This method includes the initial step of extruding a round section aluminum tube. Typically, the extruded aluminum tube is made from AA6xxx aluminum alloy stock. Next comes the bending of the extruded aluminum tube (see block 14). The bending may be accomplished by any means including, in a rotary draw bender, a pressure roll bender, or by means of a servo drive bender, such as will be described in detail below.

As in 1a 1, the bending step is followed by localized induction annealing (see step 16). This is done to restore some formability for future forming operations. The localized induction anneal 16 is then followed by a step of preforming the extruded aluminum tube (see box 18). This is done in a mold in accordance with methods well known in the art.

As also in 1a As illustrated, the preforming step is followed by another localized induction anneal (see box 20). It is noted here that localized induction annealing to restore formability may be performed subsequent to both bending and preforming, as illustrated in boxes 16 and 20, or only after bending, as illustrated in box 16, or only after preforming, as illustrated in box 20.

Next comes the hydroforming of the extruded, bent, and preformed aluminum tubing (see Box 22). After hydroforming the extruded aluminum tube that is to form the part or stringers, the part is trimmed to the required length (see box 24). in the in 1b In the illustrated embodiment, this is followed by artificial aging (see box 26) and then by batch chemical treatment (see box 28). As in the alternative value stream method of 1b As illustrated, the batch chemical pretreatment 28 is completed prior to the artificial aging 26. Thus, these final two steps can be performed in any order.

In each of the 1a and 1b In the illustrated value stream method embodiments, artificial aging 26 is completed to provide target yield strength to the final part or vehicle side rails. The chemical pre-treatment is completed to prepare the part to receive and hold adhesives, paints or other chemicals required for the downstream vehicle assembly process.

Reference is now made to the following subsections of this document which provide more detailed descriptions and explanations regarding the extrusion 12, bending 14, induction annealing 16 and/or 20, hydroforming 22, artificial aging 26 and batch chemical pretreatment steps 28 of the overall process 10 . It should be noted that the prebending 14, induction annealing 16 and/or 20, preforming 18, hydroforming 22, and trimming 24 steps involve the individual machining of extruded aluminum tubing, while the artificial aging 26 and chemical pretreatment 28 steps involve a variety of Include parts or vehicle side members that are processed together in common frames.

extrusion process

With reference to 2 an example of a method for hydroforming an extruded structural tube is illustrated. The process begins by forming an extruded structural tube in an orifice die. With reference to 2 An example of an orifice extrusion die 50 is illustrated. The orifice extrusion die 50 includes a mandrel plate 52 and a cap portion 54. An aluminum billet 56 is heated and extruded through the orifice extrusion die 50 at high temperature and pressure. The extruded aluminum is separated in the mandrel plate 52 and reunited at a point in the cap section 54 . The point at which the aluminum rejoins creates welds 58 in the extruded tube T. The extruded tube T can be referred to as a structural extruded tube. The extruded tube T is formed in a continuous rolling process. After extrusion, the tube T is cut to a desired length by laser trimming or other suitable operation. As noted, for the manufacture of vehicle side rails, tube T may be extruded with a round cross-section having a diameter of approximately 5.08 cm, a thickness of either 2.8 mm or 3.5 mm and a T4 hardness . Tolerances are maintained up to ½ of those specified by the Aluminum Association.

This in 2 The method illustrated relates to the manufacture of an extruded aluminum structural tube. Although an extruded aluminum structural tube may be employed in the present value stream method 10, the method is not limited to the listing of this tube. Another extruded aluminum tube can be used in the process, if necessary, in which a seam-welded tube and an extruded seamless tube are involved.

rotary draw bending process

In one possible embodiment, the extruded aluminum tube T is subjected to a rotary draw bending process using equipment comprising a mandrel with surface wear resistant inserts.

With now reference to 3a A portion of a mandrel and ball assembly 100 is illustrated in an end perspective view. 3b Figure 12 depicts a cross-sectional view looking in the direction of arrows 3B-3B. In general, the mandrel and ball assembly 100 includes a ball body 112 and a surface wear resistant insert 120 that is held in place by a fastening mechanism 122 .

The illustrated embodiment includes spherical body 112 that is generally symmetrical about centerline axis 114 . The outer surface 116 of ball body 112 includes a recess 118 and insert 120 is positioned at least partially within recess 118 .

In the figures, insert 120 comprises a ring of material generally symmetrical about centerline axis 114 and itself Extends 360° around outer surface 116 of spherical body 112 . Fastening mechanism 122 is positioned adjacent insert 120 and retains insert 120 within recess 118 . Attachment mechanism 122 also includes a plurality of separate fasteners 126A-E that attach retaining ring 124 to ball body 112 . Separate fasteners 126A-E may be threaded or unthreaded, or may be of any type known to those skilled in the art. 4 Figure 12 shows an exploded view of the mandrel and ball assembly of Figure 12 3a and 3b ab, comprising ball body 112, insert 120, retaining ring 124 and separate fasteners 126A-E.

Other attachment mechanisms could also be used to hold the insert 120 in place. For example, retaining ring 124 may be attached to ball body 112 by mating a threaded surface (male or female) on retaining ring 124 with a complementary threaded surface (female or male threads) on ball body 112 . That is, both the ball body 112 and the attachment mechanism 122 could both be threaded and screwed together. Additionally, retaining ring 124 may be integrally formed with insert 120, creating a separate subassembly that is then attached to sphere 112 using any of the methods described. Other attachment mechanisms, such as welding, adhesion, an interference fit, or a transition fit, may also be used for embodiments encompassed within the scope of the disclosed invention.

Insert 120 is positioned on the part or parts of a mandrel and ball assembly 100 that are subjected to relatively high normal contact forces with an inner surface of the tubular blank during a bending operation. In one embodiment, insert 120 comprises a single, contiguously disposed piece of material at least partially circumscribing outer surface 116 . In an alternative embodiment, the insert 120 comprises a discrete number of non-contiguously arranged pieces of material shaped as incomplete arcs or triangles that are spaced from one another and arranged about the outer surface 116 . Insert 120 may include a uniform or non-uniform cross-sectional shape.

Insert 120 includes a surface wear resistant material, which may be a plastic material, a low-stacking-fault energy material, or a metal alloy (e.g., a copper, bronze, or cobalt-based alloy), a material that is metallurgically incompatible with the tubular blank (ie, insoluble solids). a low friction material and any combination thereof. Suitable plastic material includes, but is not limited to, nylon, polytetrafluoroethylene, polyoxymethylene, polyurethane, and polyethylene, or any combination thereof. In general, the hardness of the surface wear resistant material should be less than the hardness of the tubular blank in which the mandrel and ball assembly will be used during bending.

With now reference to 5a and 5b A side view of a mandrel and shank assembly 130 is depicted. The illustrated embodiment generally includes a cylindrical shank body 132 having a circular cross-sectional area and an outer surface 134 defined by a length. Boss 136 of cylinder body 132 is the leading end of the mandrel and shank assembly as it is loaded into a tubular blank for bending.

In general, lug 136 experiences relatively high contact forces with an inner surface of a tubular blank during a bending operation. Similar to the spike and ball arrangement described above, outer surface 134 of stem body 132 includes indentation 138. Insert 140 is at least partially positioned within indentation 138. Insert 140 includes a ring of material that extends around outer surface 134 of stem body 132 . Fastening mechanism 142 is positioned adjacent to insert 140 and retains the insert in recess 138. Fastening mechanism 142 includes retaining ring 144 which retains insert 140 in recess 138.

As described above in a similar manner for attachment mechanism 122, attachment mechanism 142 may retain insert 140 in recess 138 by threading retaining ring 144 onto shank body 132 using complementary male-female threaded surfaces, or may comprise a plurality of separate fasteners that attach the retaining ring to the stem body. Separate fasteners may be threaded or unthreaded, or any fastener known to those skilled in the art. Additionally, retaining ring 144 may also be integrally formed with insert 140, creating a separate subassembly that is then attached to stem body 132 using any of the methods described herein.

Insert 140 is positioned on a portion of lug 136 of stem body 132 . Similar to insert 120 described above, insert 140 comprises a surface wear resistant material that may be a plastic material (e.g., nylon, polytetrafluoroethylene, polyoxymethylene, polyurethane, polyethylene, etc.), a low-stacking-fault energy metal, or metal alloy (e.g., a copper, bronze, or cobalt based alloy), a material that is metallurgically incompatible with the tubular blank (ie, soluble solids), a low friction material, and any combination thereof. In general, the hardness of the surface wear resistant material should be less than the hardness of the tubular blank in which the mandrel and ball assembly will be used during bending. Additionally, insert 140 may comprise a single contiguously disposed piece of material or may be formed from a discrete number of non-contiguous pieces of material and may comprise a uniform or non-uniform cross-sectional shape.

With now reference to 6 An exemplary mandrel assembly 150 including a mandrel-shaft assembly 130 and a plurality of connected mandrel-ball assemblies 100A-C is depicted. At least one mandrel and ball assembly 100A is connected to hub 136 of mandrel and shaft assembly 130 by a hinge connection 154A. Additional mandrel-ball assemblies (e.g., 100B and 100C) may be serially connected to mandrel-ball assembly 100A by means of additional hinge connections (e.g., 154B and 154C). Articulated joints 154A-C may be of any type known to those skilled in the art (e.g., ball joint, H-type joint, poppit joint, end joint, etc.). Alternatively, mandrel-ball assemblies 100A-C may be connected to mandrel-ball assembly 130 by a cable on which mandrel-ball assemblies 100A-C are strung.

Insert 140 and inserts 120A-C may comprise the same surface wear resistant material or combination of materials consistent with embodiments described herein. Alternatively, insert 140 and one or more of inserts 120A, 120B, and 120C may each comprise a different surface wear resistant material or combination of materials consistent with embodiments described herein.

With now reference to 7 1 is a top view of an exemplary rotary draw bender mechanism 160 including a follower 162, a clamp 164, a bend die 166, a stripper 168, and a mandrel assembly 150 connected to rod 174. FIG. The leading edge of an extruded aluminum tube/workpiece W is clamped to bending die 166 (using clamp 164). Mandrel assembly 150 is placed within workpiece W . An outer surface 116 of ball body 112 and an outer surface 134 of stem body 132 are generally shaped to fit within the workpiece W such that outer surface 116 and outer surface 134 contact an inner surface 172 of workpiece W during the bending process while allowing for easy insertion of the mandrel assembly 150 into the workpiece/tube (ie, a small clearance fit). Bending tool 166 rotates pulling the workpiece/tube W around bending tool 166 . Inner surface 172 is supported by mandrel assembly 150 while workpiece W is drawn about bending tool 166 . The workpiece W is externally supported by follower 162 and stripper 168 . Mandrel assembly 150 helps prevent tube buckling, wrinkling and collapse of the workpiece/tube W during the bending process.

Although bending with a mandrel has been described, it is understood that "empty bending" without a mandrel in the overall process can also be used.

induction annealing process

As previously described, the workpiece W may be subjected to an induction anneal 16 , 20 following the bending 14 and/or following the preforming 18 . For this purpose, the workpiece W is placed in a water-cooled copper "channel" coil C, which has the same shape as the workpiece W (see Fig 8th ). In particular, alternating current flows through the channel winding C (transformer primary winding) to generate an alternating electromagnetic field. The workpiece W forms the transformer secondary winding. Heating efficiency and uniformity is achieved through the coil design and the contouring of the coil relative to the workpiece shape.

9 Figure 12 illustrates the workpiece W including the A-pillar portion P where the induction annealing from point A to point B is completed. Portion T indicates the portion of the workpiece W that will be trimmed during the process, as will be described in detail below. It is noted that the roof rail portion R of the work W can have various lengths depending on the body configuration of the vehicle (at for example regular driver's cab, extended driver's cab, crew cab) may have.

In one embodiment, induction annealing is completed at a temperature of between 120-160°C using a 10-30 second ramp time. In another preferred embodiment, induction annealing is completed at a temperature of 130-150°C using a ramp time of 20-30 seconds. In another preferred embodiment, induction annealing is completed at a temperature of 135-145°C using a ramp time of 20-30 seconds. In yet another preferred embodiment, induction annealing is completed at a temperature of about 140°C using a ramp time of 25-30 seconds.

in the in 1a and 1b In the illustrated embodiments of a process method for hydroforming a workpiece W, the workpiece W comprises an extruded aluminum tube, however, it is understood that the workpiece may have other shapes or be formed from other materials. The process method involves bending the workpiece W into a first preliminary shape (see step 14). This is followed by induction annealing of the workpiece W in the manner previously described (see step 16). The induction annealing process 16 uses current to locally heat the workpiece W to counteract excessive hardening within the workpiece, thereby allowing for increased formability during subsequent steps of the hydroforming process method.

This is then followed by preforming the workpiece W into a second preliminary shape (note step 18). This is then followed by a second induction annealing step 20. Next is the hydroforming of the workpiece W to a target final shape (note step 22). Subsequent to the hydroforming, the workpiece W is subjected to trimming to a target length (see step 24). After trimming, the workpiece W, in which in 1a embodiment is subjected to a heat treatment to impart desired strength properties to the workpiece W (note step 26). In the illustrated embodiment, the heat treatment is a 6 hour T6 treatment at 180°C to induce or impart to the workpiece W an average yield strength of typically 290 MPa. In alternative embodiments, the heat treatment can be completed in 4 to 10 hours at temperatures between 160-200°C. The workpiece W is then subjected to a batch chemical pre-treatment in step 28.

In an alternative embodiment of the 1b In the illustrated processing method, the artificial aging step 26 and the batch chemical pretreatment step are carried out in the reverse order.

Although two steps of increasing induction annealing 16, 20 in 1a and 1b are illustrated, it is noted that in a possible alternative embodiment only the induction annealing step 16 following the pre-bending is completed. However, the second induction annealing step 20 does not. In yet another alternative embodiment, only the induction annealing step 20 is completed. However, the first induction annealing step 16 does not.

Each of the manufacturing method embodiments is of particular use in the manufacture of light truck roof rails that will undergo significant bending of approximately 45° at the A-pillar portion P (see FIG 9 ) to support the transition of the workpiece W from the A-pillar to the hinge pillar.

In the 10 and 11 Data presented shows that the induction annealing step or stage 16, 20 allows for an increase in overall material elongation (elongation) in use (note "IA" parts and also note that "weld" and "no weld" denote where the ductile specimen was cut from the structural tube). And indeed, upward extensibility is provided in high elongation regions by the dual stock material. Furthermore, and surprisingly, no deterioration in T6 hardness or heat treatment properties is observed when induction annealing is completed at temperatures between 120-160°C for 10-30 seconds. Thus, overall elongation increases while not affecting the yield strength of the final workpiece product. Such a combination of beneficial results could not have been anticipated.

Advantageously, the induction annealing 16, 20 supports the automotive industry on a large scale. Both structural and seamless tubes benefit from this process method. Indeed, structural tubing can now be used directly in the manufacture of difficult-to-form A-pillar roof rails. Thus, the process method enables the use of a higher tolerance and a higher production-efficient material for the hydroforming of roof rails.

It should be noted that the induction annealing process 16, 20 is limited only to the heated region of interest: that is, the bending area where plastic elongation is reduced by the bending and/or preforming steps of stages 14, 18 of the manufacturing process has been. Heating of the tube or workpiece W is localized to the induction annealing region and therefore there is no special equipment required for material handling of the workpiece in the unheated regions. Furthermore, the induction annealing parameters required to restore formability to the workpiece W do not result in post-hydroforming material heat treatment reaction damage, and the formed workpieces (A-pillar roof rails in the illustrated embodiment) are still able to exhibit the target yield strengths .

hydroforming process

Reference is now made to 12a and 12b 10 are taken illustrating a vehicle side rail 200 formed by hydroforming in accordance with the specific concepts described herein. The side rail 200 includes a bend B. The inner radius or flat shoulder radius R of bend B is formed by a non-constant radius cross-section that includes a first transition segment 212, a second transition segment 214, and an intermediate segment 216 between the first and second transition segments. See also 14 , showing a design of side rail 200 at bend B.

As previously noted, the side rail 200 forming process may begin by extruding a structural aluminum alloy tube in an orifice die 50 that includes a mandrel plate 52 and a cap portion 54 . In particular, an aluminum billet 56 is heated by the orifice extrusion die 50 at high temperature and high pressure. The extruded aluminum is separated in the mandrel plate 52 and reunited at a point in the cap section 54 . The aluminum extruded tube can be referred to as a structural extruded tube. The tube is formed in a continuous rolling operation and is cut to a desired length after extrusion.

Next, the extruded aluminum tube can be bent in a desired manner using any bending method (rotational drawing, pressure rolling, etc.). This may be followed by an intermediate forming (i.e. preforming) operation. Further, the extruded tube or workpiece may be subjected to induction annealing after bending, after preforming, or both, to restore some formability to the extruded tube or workpiece.

After the preliminary operations and processes of extrusion, bending, preforming and annealing discussed above, the bent and preformed extruded aluminum tube or workpiece W is loaded into a hydroforming tool located in 13a - 13e is schematically illustrated as a two-part mold D1, D2.

Subsequent to the loading of the workpiece or tube W into the mold D1, D2, the mold is closed (see 13a and 13b) . Upon reaching the in 13c In the partially closed position illustrated, a liquid L is introduced into the interior of the workpiece W at a first pressure level. The first pressure level is in the range of about 0 to 200 bar. In another embodiment, the second pressure level is in the range of 50 to 150 bar. In yet another possible embodiment, the first pressure level is about 100 bar. The hydroforming liquid L can be water or another suitable material.

When viewing from 13c it is noted that the upper portion of the die D1 includes a flat shoulder wall portion S specifically shaped to contact the die W at the time of the hydroforming process when the die D1, D2 is only partially closed, and the first pressure head at Used to prevent buckling of the pipe during the closing phase. This point of contact forms the intermediate portion 216 of the flat shoulder angle radius R of the stringer 200. This reduces the circumferential edge fiber stretch and deformability required to mold the workpiece W into the portion or stringer 200 along the interior of the bend where the material becomes thicker.

The next step in the hydroforming process is to fully close the hydroforming die D1, D2. 13d Figure 12 illustrates the forming tool D1, D2 being closed around the workpiece W. FIG. After the forming tool D1, D2 is fully closed around the workpiece W, the pressure of the liquid L filling the workpiece W is increased to a second pressure level to mold the workpiece W and permeate it by hydrostatic pressure. The second pressure level is in the range of 500 to 1500 bar. In a Another possible embodiment is the second pressure level in the range from 750 to 1250 bar. In yet another possible embodiment, the second pressure level is approximately 1000 bar.

When the pressure is increased, the workpiece W is pushed outward toward the die D1, D2. Essentially, the intermediate portion 216 of the shoulder angle radius R is already engaged with the shoulder wall portion S of the mold D1 before the pressure of the liquid L is increased to the second level. This prevents unrestrained/unsupported section bending during the final phase. In contrast, in a typical conventional scenario, the workpiece does not make contact with the mold wall until the mold is fully closed and a calibration pressure is applied. The actual radius of curvature of the angle formed at the apex of the plastic hinge is typically smaller than the corresponding radius of the molding tool in this case. Thus, the resulting r-t ratio is also smaller than in the design, and the edge fiber elongation is higher. In the present method of processing, the flat shoulder wall section S engages the workpiece W early in the finishing phase and prevents additional unrestrained bending that substantially reduces edge fiber strain and increases the r-t ratio. At the same time, the strain in this area is almost unchanged during the calibration phase.

Further, the engagement of the workpiece W with the wall portion S results in a slight clearance G being maintained between the die D1, D2 and the workpiece W, thereby forming the first and second transition segments 212, 214 of the side rail 200. Therefore, it should be understood that the in-mold formed workpiece W and ultimately the side rail 200 will have tool marks from the mold D1 along the intermediate segment 216, but will be entirely free of tool marks along the first and second transition segments 212,214. As in 15 As illustrated, the first and second transition segments 212, 214 of the side rail 200 include a bend B angle where the middle 40% is expanded with a transition to a conventional angle shape on the remaining 30% of the angle at each end.

Subsequent to the hydroforming, the workpiece W is trimmed to a final target length by means of laser trimming or other suitable trimming processes. Subsequent to the laser trimming operation, the workpiece, now in the shape of the roof rail 200, may be heat treated to artificially age the aluminum alloy to a target strength in a manner known in the art. The side rail 200 may then subsequently be subjected to a chemical pre-treatment to prepare it to receive adhesives, paint and/or other coating and chemicals applied in a subsequent vehicle assembly process. In an alternative embodiment, the side rail 200 is subjected to a chemical pre-treatment prior to the heat treatment rather than after the heat treatment. Both approaches can be used.

The following example further illustrates the process method of hydroforming an extruded aluminum tube.

example

An extruded structural tube or seamless tube formed from AA6082-T4 material has an outside diameter of 5.08 cm and a wall thickness of either 2.8 mm or 3.5 mm. The tube is positioned in the hydroforming tool and the forming tool is partially closed. The tube is then charged with a hydroforming fluid at a pressure of 100 bar to prevent the tube from buckling. Continued closing of the upper mold causes the tube to engage the flat shoulder wall portion of the mold which reduces the strain on the rim fiber and the required ductility of the aluminum alloy in the face of the intermediate segment. The mold is then fully closed and the pressure of the hydroforming fluid is increased to 1000 bar to complete the hydroforming process.

Briefly, from the disclosed in this document and in 13a - 13e Schematically illustrated pressure sequence hydroforming process method results in numerous benefits. As noted above, by engaging the workpiece W with the flat shoulder portion S of the die D1 when the die D1, D2 is partially closed and the liquid is at a first lower pressure head, it is possible to reduce the minimum radius of curvature formed in the tube which restricts strain on the marginal fiber and discourages cracking along the intermediate segment 216. This also serves to reduce or eliminate part failure and material waste resulting from the hydroforming process. To After the hydroforming process has been completed by fully closing the die D1, D2 and increasing the pressure of the liquid L to the second level, the internal or flattened angle radius R of the bend B in the workpiece is provided with a cross-sectional length of a line reduction of less than 1%. In essence, this reduces the geometry of the workpiece W along the rake angle radius R by about 2 mm in width. Please refer 14 .

Batch heat treatment and chemical pre-treatment process

Reference will now be made to 16 - 24 are taken which illustrate a multi-purpose rack 300 for processing a plurality of parts P simultaneously. The cradle 300 includes a frame 312, a plurality of defined locations 314 on the frame for receiving and holding individual parts P for processing, and a latch assembly 316 for locking the parts to the frame at the defined locations. In a preferred embodiment, the frame 300 is formed of stainless steel, such as 316L stainless steel, and the frame 312 employs open channel materials rather than closed boxed sections to enhance drainage. The frame 300 can accommodate parts P of different lengths, for example A-pillar roof rails, which have a length depending on the type of cab: a regular, an extended and a crew cab. Reviewing the following description, the rack 300 is flipped down about its centerline (defined by center beam 328 and center beam 348) to provide balance through improved weight distribution and ergonomics for manually loading parts into the rack to support a minimized range. As further noted, there is a large open channel along the centerline to enhance air and fluid flow, which in turn reduces the flow path length to those portions located in the center of the frame.

As illustrated, the frame 312 includes a base, indicated generally by reference numeral 320, and two side supports 322, two slide members 324 connected to the side supports, two end supports 326, and a center support 328. A "pallet" is formed by four crossbeams 330, each of which has a t-shaped cross-section. The "pallet" causes the rack to be engaged by the forks of a forklift (not shown) and lifted.

The frame 312 further includes two opposite end assemblies 332. Each end assembly 332 includes two corner posts 334, a center post 336, an upper cross member 338 and a lower cross member 340. A sub-support 342 is between the center post 336 and one of the corner posts 334 at each end of the frame 300 is provided. Each part support 342 includes two slide rails 344 and four offset end plates 346 for receiving and holding ends of the parts P in a manner to be described in detail below.

A center beam 348 aligned with the center posts 336 and extending between the center posts and the top cross members 338 overlies the center post 328. Four center posts 350 extend between the center post 328 and the center beam 348. The center posts 350 are on centered on the frame 300 and overlying the "pallet" formed by the crossbeams 330.

As also in 16 As illustrated, the frame 312 also includes four uprights 352. A upright 352 is provided in alignment with each mullion 350, with two of the uprights overlying each of the two side beams 322. FIG. A support arm 354 extends between each center post 350 and its cooperating, aligned post 352. Thus, each support arm 354 is attached to a center post 350 at one end and to a post 352 at the other end.

As noted, each support arm 354 includes a plurality of sub-assembly features 356. In the illustrated embodiment, the sub-assembly features 356 are in the form of a plurality of spaced retaining grooves or scalloped cutouts. Similarly, each panel 346 of the parts supports 342 includes a plurality of part assembly elements 358 . In the illustrated embodiment, the sub-assembly elements 358 include spaced tabs.

Reference will now be made to 17 - 19 are taken which illustrate how a part P is loaded into the rack 300. FIG. As illustrated, an opened end of the panel or roof rail P is positioned over one of the tabs 358 of the lowermost innermost panel support panel 346 . The body of part P is then placed in the two aligned and cooperating part locating features/grooves 356 in the first and second support arms 354 . As will be noted, there are six tabs 358 on the lowermost innermost parts support plate 346, each tab having part assembly elements/ spaced retaining grooves 356 in the two support arms 354 are aligned. Thus, the support arms 354 and the lowermost innermost part support plate 346 hold individual parts P at six defined locations 314 on one side of the frame 300. It should be noted that six additional parts P are used in these structures on the opposite side of the frame 300 (ie, other side of center beam 348) to provide balance.

Basically, the tabs 358 receive and hold the open ends of the parts P so that they face downward. This contributes to a good efficient drainage of the parts P during the chemical pretreatment when they are removed from the treatment tanks 422 (see Fig 28 and the following description) are removed. As a result, less processing solution is advantageously transferred between tanks 422 .

With renewed reference to 16 and 17 For example, the frame 300 also includes four support arms 360, 362, 364, 366 pivotally connected to each center post 350. As shown in FIG. As noted, each support arm is between an in 16 illustrated the parts charging position and one in 21 illustrated the parts attaching position selectively slidable.

As illustrated, the bottom arm 360 is slightly shorter than the next taller arm 362, which is slightly shorter than the next taller arm 364, which is slightly shorter than the longest uppermost arm 366. Further, each of the three lowermost arms 360, 362, 364 includes a plurality of sub-assembly features in the form of grooves or notches 368.

Is the first layer of six parts P on the support arms 354 and on the bottom innermost part support plate 346 (as in 17 illustrated) positioned and arranged, the lowermost support arms 360 of the, in 17 illustrated, the parts charging position in which, in 20 illustrated, the parts mounting position pivoted. In the parts mounting position, the retaining arms 360 overlie the support arms 354 and effectively retain the first row of parts P in the retaining grooves 356, effectively locking those parts in their defined locations 314 on the rack. As pointed out, not a single part P in the first row comes into contact with any other part. Thus, the parts P are fully subjected to any processing while being held in the stand 300. FIG.

The next row of parts P is now added to the rack 300. This is accomplished by positioning the open ends of the next six parts on the six tabs 358 of the next highest, next innermost part support plate 346 and leaving each part in aligned retaining grooves 368 formed in the upper surface of the lowermost support arm 360 are provided. With the six pieces P of the nearest layer positioned in this manner, the support arms 362 are pivoted from the piece-loading position to the piece-fixing position. In the part-attaching position, the retaining arms 362 function to retain the second row of parts P in the retaining features, grooves or notches 368 of the retaining arms 360 .

A third row of parts P is now added to each side of the frame 300. This is accomplished by positioning the open ends of six parts P on the third part support plate 346 and leaving the ends of the parts in the aligned, cooperating part retaining features/grooves 368 in the support arms 362. When all six parts P are properly positioned, the support arms 364 are pivoted from the part receiving position to the part holding position. As will be noted, in the part-retaining position, the retainer arms 364 overlie the parts in the third row, thereby retaining the parts in the grooves 368 of the retainer arms 362. Thus, the parts in the third row are maintained at defined locations on the frame 312 so that each individual part does not come into contact with any other part.

Now the last row of parts P is added to each side of the frame 300. To do this, the open ends of six additional parts P are positioned over the tabs 358 in the top part support plate 346 with the bodies of the parts being received and resting in the aligned grooves 368 of the arms 364 . With all six parts P of the fourth row of parts properly positioned in their defined locations 314, the uppermost support arms 366 are pivoted from the part-loading position to the part-fastening position. It should be noted that when the rack 300 is fully loaded and the support arms 360, 362, 364, 366 are all in the parts holding position, all of the support arms overlie the associated support arm 354 which is located between the mullion 350 to the cooperating upright 352 aligned in alignment. Please refer 21 .

As in 16 , 17 , 20 and 21 best illustrated includes the lock ment assembly 316 includes a plurality of locking bars or slide rails 374 . The locking bars 374 have a U-shaped cross-section that defines a longitudinal channel that receives and retains the ends of the retaining arms 360, 362, 364, 366 in the locked position.

A locking bar 374 is slidably received on each post 352 and is shiftable between the parts loading position and the parts locking position. The parts loading position is in 16 , 17 , 20 and 21 illustrated. In this position, the latch rods 374 are fully retracted over the posts 352. In contrast, if the locking bars 374 are used as in 22 and 23 1, with the parts in the closed position, are lifted and extend completely away from the uprights 352. FIG. It is noted that each locking bar 374 includes a stepped configuration such that each locking bar will receive and retain the end of each support arm 360, 362, 364, 366 when in the locked position. See in particular 23 , in which parts P have been removed for better understanding. A clevis pin 376 is provided to secure each locking bar 374 in the locked position. Clevis pin 376 is captured in bearing hub 87 welded to one side of each locking bar 374 . See also 24 . In particular, the latch pin 376 is inserted through a cooperating aperture in the post 352 which supports the latch bar. It is noted that the end 378 of the latch pin extends fully through the latch bar 374 . A securing tab 380 extends through an opening 382 into the end 378 of the clevis pin 376 and is held in place (ie, connected into a closed loop). In one possible embodiment, the securing tabs 380 have a predetermined breaking point and must break in order to be pulled out of the clevis pin 376 to cause the clevis pin to release, so that the locking rods 374 and the retaining arms 366, 364, 362, 360 for removing parts P from the rack 300. In one possible embodiment, the securing tab 380 is a permanently lockable sacrificial cable tie.

It is noted that the retaining grooves 356, 368 and the tabs 358 provide a defined location 314 for each P part. The overlying support arms 360, 362, 364, 366 ensure that each part P is held at these defined locations 314 where no part comes into contact with another part.

During chemical pretreatment, rack 300 is immersed in a tank containing a chemical solution. Air often becomes trapped in individual parts P during immersion, creating a buoyancy force that tends to lift the parts P out of the grooves 356, 368 and tabs 358. The overlying support arms 360, 362, 364, 366 function to hold the parts P at the defined locations 314 within the grooves 356, 368 and on the lugs 358 so that the parts can take full advantage of the treatment.

An alternative method of snapping such parts would be in a vertical orientation to facilitate drainage; however, such a configuration requires deeper chemical tanks, a larger furnace, and a more extensive pretreatment system. Another alternative is to rotate the rack as it is immersed and raised, i.e. horizontally within the tank to reduce tank size and chemical volume, but pivot vertically on entry and exit to aid drainage. Such a line is more complex, more expensive and slower to operate. Horizontal with an enclosed air pocket is also beneficial as the inner surface requires no pre-treatment, reducing chemical consumption and minimizing "drag".

Reference is now made to 25 - 27 10 are taken illustrating an alternative embodiment of rack 382 for holding a plurality of parts, illustrated as front rails F at defined locations. As in 25 As illustrated, the cradle 382 includes a frame 384 supporting a first series of front rails F on either side of a centerline defined between the two upper side rails 386 . As in 26 and 27 1, a second outer layer of front rails F is then loaded onto each side of the frame 384. FIG. Once loaded, the locking bars 388 are released from the rack loading position shown in FIG 25 is illustrated to the parts locking position shown in FIG 26 and 27 is illustrated, shifted. Clevis pins 390 and locking tabs 392 act to lock the locking bar 388 in the parts locking position in the same manner as the locking bars 374 of the first embodiment described above. The parts are positioned to maximize packing density but aligned to maximize drainage efficiency. This front rail requires the parts to be rotated to eliminate horizontal "dead spots".

Reference is now made to 28 which is a schematic block diagram of the production floor 400 of the manufacturing facility. Block 402 in the drawing figure represents the rack loading area where the rack 400 is loaded with parts P in the manner described above. The loaded rack 300 is then conveyed from the rack loading area 402 to the heat treatment area indicated generally by reference numeral 404 by a forklift or other means. Specifically, the rack 300 is loaded onto a conveyor belt 406 which transports the rack 300 and the parts P locked therein through the heat treatment furnace 408 . Subsequent to the heat treatment, this conveyor transfers the rack 300 and the parts P locked thereon to the conveyor 410. Conveyor 410 transports the rack 300 and the parts P locked therein through the cooling chamber 412, thereby completing the heat treatment process.

A forklift or other means then transfers the rack 300 and the parts P latched therein to the chemical pretreatment area indicated generally by reference numeral 414 . In particular, the forklift transfers the rack 300 and the parts P latched therein to the loading area 416 where the racks are loaded onto a conveyor which, in the illustrated embodiment, takes the form of a monorail conveyor 418 . The racks 300 and the parts P latched therein are then transferred or transported through the chemical pre-treatment facility 420 by the monorail conveyor 118 . There, the rack 300 and the parts P latched therein are immersed in the various treatment tanks 422 to complete the chemical pre-treatment of the parts. The monorail conveyor 418 then transfers the racks 300 and the parts P held therein to the drying oven where the parts P and rack 300 are dried before being transferred to the unloading station 426 . A forklift or other means is then used to transport the racks 300 and the parts P locked therein to the assembly area 428 where the parts are removed from the rack and made ready for vehicle assembly.

It is noted that the parts P are locked in the frame 300 by means of the support arms 360, 362, 364, 366 and the locking assembly 316, which includes the locking rods 374 and clevis pins 376 on the frame loading surface. The processing integrity of the parts P in the rack 300 through the heat treatment and chemical pre-treatment process is secured by the securing tabs 380 . Specifically, these locking tabs 380 are inserted into the ends 378 of the clevis pins 376 and locked to the rack loading area 402 (prior to heat treating). When the rack 300 reaches the assembly area 428, intact, unbroken securing tabs 380 indicate that all parts P in the rack 300 have been properly subjected to heat treatment and chemical pre-treatment. On the other hand, if one of the breakaway securing tabs 380 breaks, this raises the possibility that one or more parts P in the rack 300 have not been subjected to proper heat treatment or chemical pre-treatment, and accordingly the parts in that rack may be submitted for inspection proper heat treatment and chemical pre-treatment processing, if necessary, can be temporarily separated from the processing. Thereby, the securing tab 380 ensures the integrity of the parts P machining. It is noted that not all parts require the heat treating step. For example, the roof rails, which require high strength, are heat treated after forming to artificially age the alloy and increase the yield strength. Front sills are required to have lower yield strength and greater ductility and therefore front sills are not heat treated and are therefore removed from the skid loading area 402 and transported to the pretreated loading area 416 by a forklift. Such a configuration allows different alloys with different heat treatment requirements to be processed through the same line.

In a particularly useful embodiment, each rack 300 includes a plate 315 carrying a unique ID code for identifying the particular rack 300 (see FIG 16 and 27 ). This could be a barcode or any other scannable image, if any. Furthermore, monitors 430, 432, 434, 436, 438, 440 are provided at various locations on the production floor 400 of the plant. Each monitor 430, 432, 434, 436, 438, 440 may include a video camera and/or scanner. As in 28 As illustrated, a monitor 1330 is provided at the rack loading area 402 . Each part P loaded in rack 300 may also have a specific scannable ID number. Accordingly, the monitor 430 enables each and every part P loaded into a particular rack 300 to be recorded. The monitor 432 records the time at which the particular rack enters the heat treatment furnace 408 upon entering the heat treatment furnace 408 . Monitor 434 records the time at which each particular rack exits cooling chamber 412 300 exits the cooling chamber 412. Monitor 436 records the time that each particular rack 300 reaches the loading area 416 of the chemical pretreatment facility 414 , while monitor 438 records the time that each particular rack is discharged from the chemical pretreatment facility monorail 418 . Ultimately, monitor 440 records the time each rack 300 reaches assembly area 428 and is unloaded. Because each rack 300 has its own unique ID code, and each part P held in each rack 300 is identified by its own ID number, the integrity of the heat treatment and chemical pretreatment process up to that Length of time required for the parts to move from the rack loading area 402 to the assembly area 428 can be monitored, also including the specific length of time required for the heat treatment and chemical pretreatment. Of course, the heat treatment and chemical pre-treatment processes are also monitored to ensure that each rack 300 of parts P is properly completed. One such process monitoring system at the production level of a manufacturing facility is disclosed in co-pending US patent application Ser. 13/768,326, filed February 15, 2013, entitled "Process Control For Post-Form Heat Treating Parts For An Assembly Operation," the entire disclosure of which is incorporated herein by reference.

The foregoing has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the precise form disclosed. Obvious modifications and variations are possible in light of the above concepts. For example, artificial aging or hardening and establishment of a flat neck part geometry are not required for all applications. All such modifications and variations are included within the scope of the appended claims when construed in accordance with the breadth to which they are fairly, lawfully and equitably entitled.

Claims (18)

A method for forming a vehicle side rail (200) from aluminum, comprising the following sequential steps: - extruding an aluminum tube; - longitudinally bending the extruded aluminum tube (T) to form a bend (B); - preforming the extruded and longitudinally bent aluminum tube after longitudinal bending; - Internal high-pressure forming of the extruded, longitudinally bent and preformed aluminum tube to form the vehicle side member (200), characterized in that an inner radius of the bend (B) is formed during internal high-pressure forming with a cross-sectional length of a line reduction of less than 1%. procedure after claim 1 comprising completing the longitudinal bending in a rotary draw bender and completing the preforming in a forming tool. procedure after claim 1 comprising completing longitudinal bending in a press roll bending tool and completing preforming in a forming tool. procedure after claim 1 , further comprising induction annealing the extruded aluminum tube (T) prior to hydroforming. procedure after claim 4 comprising completing the induction annealing after longitudinal bending and before preforming. procedure after claim 4 comprising completing induction annealing after preforming. procedure after claim 4 comprising completing the induction annealing after longitudinal bending and after preforming. procedure after claim 4 , comprising positioning the longitudinally bent and preformed extruded aluminum tube in a hydroforming tool (D1, D2), wherein the hydroforming tool (D1, D2) is partially closed and the longitudinally bent and preformed extruded aluminum tube in the hydroforming tool (D1, D2) under a liquid is subjected to a first pressure level. procedure after claim 8 comprising engaging an inner radius of a bend in the longitudinally bent and preformed extruded aluminum tube with the hydroforming die (D1, D2) before the hydroforming die (D1, D2) is fully closed, thereby increasing the amount of marginal fiber strain on the inner radius of the bend (B) is reduced. procedure after claim 9 comprising forming a cross section with a non-constant radius having a first transition segment (212), a second transition segment (214) and an intermediate segment (216) between the first and second transition segments (212, 214), and providing the first and second transition segments (212, 214) with a tighter radius of curvature than the intermediate segment (216). procedure after claim 10 comprising fully closing the hydroforming die (D1,D2) around the extruded aluminum tube (T) and raising the fluid pressure level to a second level to form and hydroform a part of the longitudinally bent and preformed extruded aluminum tube. procedure after claim 11 comprising maintaining a spacing between the hydroforming tool (D1, D2) and the first and second transition segments (212, 214) during hydroforming. procedure after claim 12 , comprising trimming the part to a target length. procedure after Claim 13 comprising loading a plurality of the parts onto a rack (300) and heat treating a plurality of the parts together to artificially age the parts and provide target strength characteristics. procedure after Claim 14 comprising chemically pre-treating a plurality of the parts on the rack (300) together to provide a chemical pre-treatment to the parts after the heat treatment. procedure after Claim 13 comprising loading a plurality of the parts onto a rack (300) and chemically pre-treating a plurality of the parts together to provide a post-trimming chemical pre-treatment to the parts. procedure after Claim 16 comprising heat treating a plurality of the parts together on a rack (300) to artificially age the parts and provide target strength characteristics after a chemical pretreatment. procedure after claim 1 comprising extruding the aluminum tube into a round cross-section from 6xxx aluminum alloy stock.

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