CA2135335A1 - Method of manufacturing closure panels using thermosetting hot melt adhesives - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Methods for forming components through the use of hot melt adhesives are disclosed. Hot melt adhesive are applied to one or more panels and the panels are assembled.
Upon curing of the hot melt adhesive the panels become bonded thereby forming the component. Under at least one method the panels are first secured together mechanically then the hot melt adhesive is applied.

Description

3 ~; 3 Attorney Docket No. 2872-00202/CPA ~-M~T~OD oF n~lF~cs~RlNG CLo8UR~ PANBL~
~IN~ lN08Fq!TIN~ ~IIOT ME~LT AD}D~8IVB8 ',` ,'; .''}: ~,"', ` : ,, .:,:
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ACRGROF~D OF ~B INV~NTIoN
I. Technical ~ d The present invention relates to techniques for -S manufacturin~ closure panels, and more particularly, to methods for manufacturing such as doors, hoods, trunk-lids ~ : .. -.. .
and body panels for using thermosetting hot melt adhesives.
II. Discuæsion In recent years there has been an increase demand ~ ~;
on the manufacturing industry to develop manufactured parts `~
at increased rates while reducing production coæts. In an ; ~
effort to meet this demand, manufacturers have turned to - ```
. - ,:,, the use of robotic manufacturing. It is therefore highly `~ `~
desirable to further develop robotic manufacturing `~
techniques to increase manufacturing rates and reduce ~ `
manufacturing costs.
One manufacturing method curren~ly being employed `;
by those skilled in the art uses mechanical fastener~ to ~
attach first and second panels together to form a ~; ;
~0 component. A major problem with this technique is that too often blemishes appear in the exposed ~urface of the panel . .

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Attorney Docket No. 2872-00202/CPA
near were ~he fasteners hold the first and second panels together. Thi~ i~ commonly referred to as "show throughH
in the manufacturing industry.
To alleviate ~he sh~w through problems manufactures have increasingly turned to the use o~
adhesives in manufacturing. Component panels are ;~ positioned for receiving the adhesive application and the ; component panels are brought together. The adhesive material i5 then cured using infrared heat or various solvents thus bonding the panels together.
Among the shortcomings associated with these techniques are difficulties in achieving the desired location, bead size and quality of adhesive. To address these difficulties, ti~e and labor intensive procedures are reguired to ensure that the adhesive bead is applied to the proper surface location and is of sufficient size to effect a secure bonding of the panels, while preventing the use of excess quantities which may areate beads of wasted adhesive around the edges of the bonded panels, collect within non~
contacting channels of the panels or escap~ from the panels to~adjacent surfaces. For adhesives which cure at ambient temperatures, the open ti~e (the time available to position the second panel on the first panel before the adhesive cures) places time limitations on bonding techniques that can be ~uccessfully used. For example, a power failure on the assembly line after adhesive beads have been applied to ( J
^ ` 2 :~ 3 ~ 3 3 Attorney Docket No. 2872-00202/CPA
~everal o~ the panelfi would result in adhesive curing be~ore ~he placement of the other panel or panel6 onto the adhesive-laden panels. thu~ the defect rate when applying an adhesive bead with a robot may be high as a result of these and other manufacturing problems. Because robotic device are frequently used in these procedures, manufacturing the device becomes more costly.
Expensive sophisticated equipment capable of the detail re~uired for the adhesive application procedure is usually utilized to ensure that the proper amount of adhesive is dispensed and that no excess adhesive is squeezed onto exterior visible surfaces of the panels.
Because excess adhesive on these exterior surfaces could cause mechanical malfunctions and aesthetic defects, the robotic device generally leaves skips and voids in its application of the adhesive to avoid adhesive ~queeze-out.
Robots occasionally encounter problems going around aorners o~ the panels when applying adhesive beads in this manner, ; ' . ! , ' . .
however, and the additional programming required to achieve desirable results creates further expenses, both ~n labor and in time. The need therefore exists for new methods for bonding multi~panel devices.
The present invention is particularly directed to techniques for manufacturing components such as auto-body panels using hot melt adhesives having exceptionally good bond strength. While the present invention relates to both "'~ ''''-'''`'''' ~ :l 3 ~ 3 3 S
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Attorney Docket NOr 2872-00202/CPA
hand made and robotic manufacturing processes, the ~ethods are particularly useful ~or robotic manufacturing techniques.
In general, hot ~elt adhesive~ are adhesives whi~h are appli~d in a liquid state and rOrm a bond upon cool~ng by trans~orming to a ~olid ~tate. In contrast, standard reactive adhesives achieve a bond through evaporation o~ ~olvents or chemical cure. With standard reactive adhesive ~y#tems high cohesion and high tempPrature resistance can be achieved after cure by chemical reaction or radiation. However, standard .
adhesives do not rapidly provide what is know in the art as "green strength". Green strength essentially is the ability of an adhesive to solidi~y or cure in a relatively -short perlod of time. ~hus, components which are formed using standard adhesives must often be clamped together and maintained in a clamped position until a high degree of cohesion is obtained.
Hot melt adhesives are generally classified as being either thermoplastic or reactiva. Thermoplastic hot melt adhesives are those which are heated to a molten state and solidi~y upon cool1ng to form the bond between adherents. Examples of thermoplastic hot melt adhesives include the UNI-RE~6 line of adhesives which are available from the Union Camp Corporation of Savannah, Georgia. UNI- ;
REZ is a polyamlde based thermoplastic adhesive resin. ~
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Attorney Docket No. 2872-00202/CPA
Reactive hot melt adhesives somewhat conversely reguire a catalyst to e~ectuate a rapid cure. ~ost o~ten, the catalyst ~nvolves the lntroduction of ~oisture to begin the cro s-linking reaction common to hot ~elt adhesives.
Still other catalyst ~uch as the introduction of convection . ~ -or in~rareA heat ~ay be employed ~or certain hot melt ,~
adhesives. ~ne reactive hot melt adhesive which has been formed to be particularly use~ul for carrying out the `
various methods of the present invention is known as . .. " .;
DYNACOLL which is available from Huls ~ntiengesellschaft ,~
of Munich, Germany. DYNACOLL~ is a polyester based moisture curing hot melt adhesive. `
While standard reactive adhes~ves may in general offer slightly better cohesion than thermoplastic hot melt adhesives there is a drastic difference in the amount of . . .
t~me required to achieve the maximum bond strength between ~ ~
thermoplastic hot melt adhesives and standard reactive ~ ~`
adhesives. ~;
For manufacturing operations where ~aximum `;` ~
~20 cohesion is a greater concern than green strength, reactive ~ ;`
hot melt adhesives can be utilized according to the ~
teachings of the present invention. Reactive hot melt ~ `
adheslves essentially combine the advantages of both thermoplastic hot melt adhesives and ~tandard reactive ~
~25 adhesives. Reactive hot melt adhesives generally enjoy a I``
green strength similar to thermoplastic hot melt adhesives ` " ` `::

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~ut with the additional advantage of bond strengths similar to ~tandard reactive adhesives.

~M~A~Y OF ~2 ~v~NTIoM
~;;5~ : In ~ocordance with the teachings of the present invention, methods and processes are disclosed for ~:~ manufacturing various components,.including but not limited ;~ to clo~ure panels such as door, hood, trunk and other body panel~ for vehioles.
A first preferred method according ~o the teachings of the present invention includes the steps of assembling a closure panel from at least two separate panel6 auch that an adhesive flow channel is provided:
securing the closure panel and in~ecting hot melt adhesives ~15 through opening~ in the closure panel and into the flow channel; allowing the adhesive to solidi~y; and removing the assemblQd part from the securing apparatus.
: According to the present invention a second method for ~orming a component having at least two different panels include the steps of loading the panels on a~transfer system and activating the transfer sys'tem ~o transport the panels to an assembly station; applying a hot melt adhesive to at least one of the panel~; aligning the panels and bring them together until the hot melt adhesive 25~ solidifies; and removing the component from the assembly station.
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A third preferred method iB al60 provided for manufacturing a component made from at least two di~ferent panel~. Th~s third ~ethod includes the ~teps of applying : a hot melt adhesive to at least one panel and allowing the hot melt adhesive to skin over; loading each panel on a transfer system and activating the transfer systsm to transport the panels to an assembly station; aligning the panels and assembling them together; introducing heat to melt the adhesive: and removing the assembled component from the assembly station.
The components produced under the above described methods generally have improved surface quality as compared with components which are formed using machanical fasteners or include mechanically attached reinforcement members.
Accordingly, one of the advantages of the present invention is that the components produced tend to have high surface quality, since no mechanical fasteners or welding is rQquired to ~orm the component and there is no risk Of show through or weld distortion.
Another advantage of the present invention i8 the ~ .
improvement in manufacturing time since fewer parts are needed to form the component.
Yet ~nother advantage of the present invention is ; that hot melt adhesives give rise to non-pollutin~
applications and have the benefit of rapidly increasing 'green strength'l shortly after application. Thus, due to r~
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this so called green strength clamping o~ the panels is not re~uired during formation of ~he component.
Yet another advantage of the present invention is no~olvents are required to chemically cure the adhesive or :~S to clean o~ purge the manufacturing equipment.
Still another advantage o~ the present invention i8 that the hot melt adhesive can be formulated to cure over a wide range of times to suit the manufacturers needs.

RI~F DE~8CRIPTION O}~ T~ DRA~ING~
; Still other advantages of the present invention will become apparent to one skilled in the art ~y reading the ~ollowing specification and by reference to the drawings ln which~
Figure 1 is a perspective view illustrating the positional relationship between first and second panels to be adhesively connected;
Figure 2 is a partial cross-sectional view of the first panel edge portion folded over the second panel edge portion, taken along line 2-2 of Figure 3:
Figure 3 is a perspective view of the first panel folded over the second panel edge portion; and Figure 4 i8 a partial cross-sectional view of the , ~
resulting bond edge region of a multi-panel device, taken .
along line 4 4 of Figure 3.
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Figure S i8 a ~low diagram depicting the steps of ~`-manufacturing the closure panel according to the teachings `~
of the ~irst preferred ~ethod; and Figure 6 is a flow diagram depicting the steps o~ ;~
manufacturin~ a closure panel according to the teachings of a ~çcond preferred method.
Flgure 7 is a flow diagram depicting the ~teps o~
manufacturing a closure panel according to the teachings of a third preferred method. `
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D131!AII~E~D DE~BCRIPq!ION OF TB . PRl~FBRRE:D_E:21BOI)IM}~I! ~ `~ " :
-. ` :: .~;, The methods of the present invention relate to the manu~acture of various components. More particularly, the present invention relates to methods for manufacturing closure components such as hoods, trunks, deck lids, body-panels and doors, among others. In general such components are useful in the produotion o~ automotive vehicles.
The closure components may ba made from various materials including but not limited to steel, aluminum and : - -, ` 20 magnesium based metals and metal alloys, ceramics and `
various plastics such as fiber reinforced plastics (FRP) and thermosetting sheet molding compounds (SMC) to name a few. These components can be ~ormed by any suitable process such as stamping, casting, and extrusion and injection molding to name a ~ew.

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Attorney Docket No. 2872-00202/CPA
Generally, the components formed under any of the ~ethod~ of the present invention will include at least two panels and optionally one or more reinforcement members which provide structural ~upport to ~he finished component.
The invent~on i8 described in detail ~elow with reference to the manufacture or an automotive hood panel including a first inner panel and a second outer panel. It should be appreciated however by those sXilled in the art that, the present lnvention, as defined by the appended claims, is clearly not limited to this particular manufacturing application.
FIG. 1 is a perspective view illustrating the positional relationship between an outer panel 10 and an inner panel 12 to be positioned together for bonding.
According to a first method of the present invention, thc -:,., . ~
outer panel 10 typically forms the aesthetic skin for the `;` "
vehicle part such as the rear trunk lid shown herein, while the inner panel 12 has ribs and the like to reinforce the . :.~ ..:.;
outer panel 10. The techniques can also be used, of - ~-course, for a variety of other parts. The inner panel 12 ncludesjonejor more edge portions, generally indicated by "`
re~erence numeral 14. The inner panel edge port~ons 14 ;~ contain a plurality of adhesive injection notches 16, which `-` -are created at regular intervals along the perimeter of the inner panel 12.

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~he outer panel 10 contain~ a plurality of edge -portions, generaily shown at 18, which extends outwardly from the outer panel 10 to a greater distance than, but ~,:
substantially parallel to, the corresponding edge portions 14 located on the inner panel 12. ~he outer panel edge portions 18 contain a plurali~y of adhes~ve injection holes 20, which are aligned with ~he corresponding adhesive injection notches 16 located along the inner panel edge portions 14.
Optionally, but preferably, the edge portions 14 and 18 of the inner and outer panels 10 and 12, respectively, can be pxetreated to enhance the bonding capabilities of the desired hot malt adhesive. Depending upon whether the surface is metallic or non-~etallic, known preparation techniques which are used for standard reactive adhesives can also be utilized under the pre~ent invention.
Examples of such known techniques include solvent wiping to remove oils and greases, surface abrasion, chemical etching, ~olvent rinsing and drying, and preheating of metallic surface to improve wetting or flame treatment of non-metallic surfaces.
" I I ~ ' ~
After bringing the outer panel 10 and inner panel ~
: , , 12 into an aligned close-contact position with each other, the outer panel edge portions 18 are folded around the inner panel edge portions 14 along lines 22 in FIG~ 1. The outer panel edge portions 18 are folded over so to form a -Attorney Docket No. 2872-00202/CPA
hem flange as indicated by re~erence numeral 26 in FIG. 2, and also 80 that the adhesive injection holes 20 align with the adhesive in;ection notches 16 to create an inlet passageway through which a liguid adhesive material can be in~ected. In the pre~erred em~odiment of a multi-panel device being secured around all edges, the hem flange 26 i5 created along the entire perimet.er of the outer panel 10 and inner panel 12 by standard hem flanging equipment. A
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flow channel 28, shown ~n FIG~ 2 and designated by the ;~
10 phantom lines in FIG. 3, is formed around the perimeter of ~:........ :
the two panels as a result of the hem flange 26.
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once the panels 10 and 12 are hem flanged to form a component 40, the component 40 is transferred to a .~
fixturing apparatus ~not shown) or some other mechanism for ` `.-.
retaining the component during the applica~ion of hot melt ~ ` .`
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adhesive. The fixturing apparatus (not shown) ideally .
would be similar to those described in United States Patent .
No. 5,026,033 which issued June 25, 1991 to Roxy and United States Patent Application Serial No. 08/049,774 i ``
which was filed on April 9, 1993, both of which are expressly incorporated herein ~y reference. After . ..... .... `~`
positioning and retalning the component 40 on the fixturing `.~
,, . .:
apparatus (not shown) hot melt adhesive 32 ~s injected .~
through the adhesive injection holes 20 and adhesive ` ; `
in~ection notches 16 and into the flow ~hannel 28 through "~
the ~se of an adhesive dispensing device 34, such the gun ~`

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Attorney Docket No. 2872-00202/CPA
or nozzle positioned in contact wlth the adhesive injection holes 20 as ~hown in Figure 2. The arrows 30 located within the flow channel 28 in~icates the direction in which ~he liquid adhesive material 32 travels wlthin the flow channel 28. ~hen a series of cuts or notches 24, as shown in FIG. 1, are made in the outer panel edge portions 18, the folding of the outer panel edge portions 18 over the inner panel edge portions 14 will result in a flow channel that is continuous around all corners and bends of the multi-panel device. Preferably the hot melt adhesive material 32 is injected through the adhesive in~ection holes 20 and into the flow channel 28 until the entire distance of the flow channel has become filled with the hot melt adhesive material 32.
The adhesive dispensing apparatus is then withdrawn and the component is maintained over the fixture for a sufficient amount of time to allow the hot melt adhesive to at least partially solidify when a thermoplastic hot melt adhesive is employed. However, when a reactive hot melt adhesive is employed a curing catalyst such as the aforementioned chemical solvents, moisture or radiant heat is introduced to begin the curing process.
once the adhesive has solidified suf~iciently to allow the component to be removed from the fixturing apparatus the component 40 is removed. It should be noted that complete solidification of the hot melt adhasive is not required.

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Only suffiçient solidification ~o as to allow safe removal o~ the component from the fixturing apparatus without effecting the bond between the inner and outer panels i8 required. Of course, if desired, the component can remain S on the fixturing apparatus until ~he hot melt adhesive has completely solidified.
Referring to FIG. 4 a cross-sectional view of the ~esulting bonded edge region of the multi-panel device, taken through a section not correspondin~ to an adhesive injection hole and notch is illustrated. The cured . . ~ . . . ,- - .
adhesive 36 generally fills the flow channel 2i~i formed between the corresponding edge regions of panels. i `
In addition to the aforementioned hot melt adhesives still other suitable hot melt adhesives are available. Polyester and polyamide based thermoplastic hot ` ;
melt adhesive~ can be purchased from Adhesive Products .
Corp., Adhesive Technologies Corp., Allied Adhesive, American Chemical Corp., Bostik, Inc., H.B. Fuller, Inc., ~ ``
Henkel Corp., and 3M among others. Likewise, other `~
suitable reactive hot melt adhesives (i.e. moistura cured) are available from Adhesive Products Corp., H.B. Fuller, .: . . ": .~
Inc., Henkel Corp., Loctite Inc., Morton International and National Starch and Chemical Company, amony others. -Virtually all hot melt adhesives such as ~
polycarbonate, polyolefin and polyvinyl acetate based hot ` ~;

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Attorney Docket No. 2872-00202/CPA
melt adhesive systems are contemplated as being useful under the present invention.
With reference to the chematic diagram of Figure 6, a ~econd ~ethod according to the teachings of the present invention will now be described. Under this method ~irst and sacond preformed panels, ~uch as those ~hown in Figures 1 at reference numerals 10 and 12, are loaded onto a transfer system such as a conveyor, either manually or robotically, and are transferred to an assembly station (not shown) which yenerally includes an adhesive dispensing device such as that shown in Figure 2 at reference numeral 34. Optionally, a pos~tioning apparatus such as a fixture (not shown) may be employed to position the panel to receive the hot melt adhesive. Once the panel or panels are positioned for reaeipt of the hot melt adhesive, the hot melt adhesive is applied to the desired bonding surfaces of the panel or panels. Typically, the hot melt adhesive need only be applied to a single panel when forming a two panel component. It should be understood however by those skilled in the art that multiple panel components can be manufactured according to the teachings of the present methcd. Therefore hot melt adhesive may be required on ~ore than one panel.
After the hot melt adhesive has been applied to one or more panels the panels are brought together until the hot melt adhesive solidif1es sufficiently to remo~e the 3 ~ 3 3 ~
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Attorney Docket No. 2872-00202/CPA
component. In the event that the hot melt adhesive i8 one which ~alls into the category o~ a reactive hot melt adhesive a curing catalyst is ~ntroduced to activate the - hot melt adhesiv- curing. Once partial curing has occurred the assembled component ~ay now be transferred along the assembly line or ~et aside ~or subsequent use.
Turn~ng now to Figure 7 a schematic diagram illustrating a third method o~ manufacturing closure panels ~-according to the teachings of the present invention is provided. Under this method a suitable hot melt adhesive is applied to one or more panels and ~he hot melt adhesive is partially cured or "skinned over". After the hot melt adhesive has skinned over the panels can be set aside and stored ~or specified periods of time prior to carrying out the assembly step. The partial cure or "skin" which forms on the adhesive occurs as outer surfaces of the dispensed bead cool such that partial solidification occurs.
At some later point the panels are loaded onto a transfer system. The panels are then transported to an a~sembly ~tation where the panels are brought together to form the component.
Next, the component is introduced into an atmosphere having sufficient heat to cause the adhesive -skin to melt and become liquified. Such an atmosphere would occur in ovens such as con~ection, induction or radiant ovens which are known in the industry. To ~ ~

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Attorney Docket No. 2872-00202/CPA
transform a hot melt adhesive ~rom a partial solid or completely sGlid ~tate temperatures in the range of from about lOO-C to about 250-C depending upon the degree of - solidification of the hot melt adhesive and the type o~
5adhesive, i.e. polye~ter, polyamide, polycarbonate or polyvinyl acetate based.
once the skinned ovex hot melt adhesive has been melted ~he panels are brought together to form the component~ As previously noted a curing catalyst may be 10employed to activate the curing process under a reactive hot melt adhesive system.
The present invention overcomes several problems encountered by the prior art. The methods utilized circumvent the need for much of the costly and time-15consuming programming procedures associated with 6kips and voids used in previous methods of adhesive application.
Alsol because the adhesive is injected into a sealed flow channel according to at least one method, the presently disclosed invention eliminates the need for extra quality ~. . i, -;, 20control equipment and/or inspection procedures to ensure ~hat the correct amount of adhiesive ~8 applied and that ~
excess adhesive is not squeezed out of the bond onto the `;
panel surfaces.
:: ~ '' Typically, because hot melt adhesives are ~`
25generally fast curing adhesives, the amount of time reguired to carry out the steps of assembling the panels ~ `
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into a component and removing the component from the assembly station i8 only a ~ew 6econds.
While the above detailed descr~ption describes a pre~erred e~bodiment of the present inven~ion, it will be ~ S underctood that the description i8 exemplary in nature and : ~ is not intended to limit khe scope of the invention. The present invention uill therefor~ be understood as susceptible to modification, altèration and variation by those skilled in the art without deviating from the scope and me~ning o~ the following claims.

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Claims (10)

1. A method of forming a component, comprising:
providing a first panel having a bonding surface;
providing a second panel having a bonding surface;
applying a hot melt adhesive to at least one of said panels along said bonding surface;
combining the panels together; and curing the adhesive to bond the panels together, thereby forming a component.

2. The method of Claim 1, wherein the bonding surface of at least one said panels is pretreated to enhance bonding.

3. A method of forming a component, comprising;
providing a first panel having a bonding surface disposed along an edge;
providing a second panel shorter in length in at least one direction than the first panel, said second panel including a bonding surface disposed along an edge;
placing the second panel adjacent to the first panel;
folding said edge portion of the first panel onto said second panel so that the edge portion engages the edge of the second panel, thereby creating a sealed flow channel along a substantial length of the panels;
thereafter injecting a hot melt adhesive into the flow channel; and curing the adhesive to bond the two panels together to form the component.

4. The method of Claim 3, wherein the bonding surface of at least one of said panels is pretreated to enhance bonding.

5. A method of forming a component, comprising:
providing an inner panel with a notch in an edge portion, said edge portion including a bonding surface;
providing an outer panel with a hole near a mating edge portion, said mating edge portion including a bonding surface;
placing the inner panel adjacent to the outer panel;
bending the edge of the outer panel around the edge of the inner panel to come in firm contact with the inner panel in order to create a sealed longitudinal flow channel and to align the hole over the notch thereby defining an inlet passageway into the flow channel;
thereafter, injecting a hot melt adhesive into the longitudinal flow channel through the inlet passageway such that the hot melt adhesive is in contact with said bonding surfaces; and curing the adhesive to bond the two panels together to form the component.

6. The method of Claim 5, wherein the bonding surface of at least one of said panels is pretreated to enhance bonding.

7. A method of forming a component, comprising:
providing a first panel having a bonding surface;
providing a second panel having a mating bonding surface;
loading said first and second panels on separate transfer systems and transporting said panels to an assembly station:
applying a hot melt adhesive to at least one of said bonding surfaces;
assembling said first and second panels together and securing them until the hot melt adhesive at least partially solidifies; and removing the assembled component from the assembly station.

8. The method of Claim 7, wherein the bonding surface of at least one of said panels is pretreated to enhance bonding.

9. A method of forming a component, comprising:
providing a first panel having a bonding surface;
providing a second panel having a bonding surface;
applying a hot melt adhesive to at least one of said panels along the bonding surface and allowing the hot melt adhesive to at least partially solidify;
load said first and second panels onto a transfer system;
position the first and second panels at an assembly station and assemble the panels together;
introduce heat to melt the hot melt adhesive;
allow the hot melt adhesive to at least partially solidify to form the component; and remove the component from the assembly station.

10. The method of Claim 9, wherein the bonding surface of at least one of said panels is pretreated to enhance bonding.