Method for reducing cycle time for flow-drill screw operations

Abstract

A method for assembling parts, comprising the following: Forming an impression on an insertion side of a first part and a projection on a contact side of the first part before the first part is assembled with a second part; Inserting a flow drill screw into the first part, with the protrusion in contact with the second part; and Turning the flow drill screw to advance the flow drill screw through the impression and to drive the second part in order to secure the first part to the second part.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a method for joining parts using flow-drill screws. BACKGROUND

[0002] Flow-drill screws are used to join parts in unidirectional joining operations. Flow-drill screws are threaded fasteners that have a special tip designed to penetrate a part by heating the part's material until it is softened in certain areas. The flow-drill screw rotates at a high speed (i.e., 5000 rpm) applying a substantially axial force (i.e., 1.5 kN) to the part. The material is heated and softened until it is plastically deformable. The speed and axial force are then substantially reduced to allow the material to form a threaded sleeve or collar around the flow-drill screw thread on the screw, which is positioned between the tip and the head of the fastener.The screw is then turned at a slower speed to screw the screw into the in situ formed threaded sleeve, thereby compressing the parts to be joined between the threaded connection and the head of the screw.

[0003] One of the advantages of flow-drill screws is that they save time and process steps, as there is usually no need to pre-drill a hole before inserting the screw, nor to cut a thread or connect a nut to a bolt. However, in complex products such as automobiles, aircraft, and off-road vehicles, where parts are joined by a large number of fasteners, the cycle time required to insert a large number of screws (i.e., 2–6 seconds) can exceed the time available in a single assembly operation.

[0004] In some assembly operations, parts can be secured together with adhesives in addition to flow-drill screws. When adhesive is applied between two panels being joined, the flow-drill screwing operation can be slowed down by the insulating effect of the adhesive, which reduces the heat transfer rate from the part on the entry side of the assembly to the part on the exit side. Furthermore, the heat generated during penetration of the parts can cause the adhesive to foam, resulting in deteriorated adhesion properties.

[0005] Some designs may include parts made from two different types of material. For example, a polymer part might need to be assembled with an aluminum part. Effective heat transfer from the polymer part to the second part can be challenging.

[0006] US patent 2013 / 0 195 579 A1 discloses a method for joining parts in which material flows into a cavity by screwing in a flow-drill screw. This creates a protrusion that penetrates the cavity. The cavity is created before the parts are joined.

[0007] DE 195 39 685 A1 discloses the joining of two parts, wherein in the case of an opening in the first part there is also an opening in the second part and the parts are joined by a rivet or a screw with a nut.

[0008] German patent DE 10 2014 204 292 A1 describes a method for joining parts, wherein a pilot hole is provided in the first part. A cover is inserted into the pilot hole. The flow-drill screw is then screwed through the cover and the pilot hole into the second part.

[0009] Further methods for joining parts, in particular with flow-drill screws, are known from US 2016 / 0 091 010 A1 and DE 103 48 427 A1.

[0010] The present disclosure is aimed at a solution to the above problems and further problems as outlined below. SUMMARY

[0011] According to one aspect of the present disclosure, a method for assembling parts using a flow-drill screw is disclosed. The method comprises the step of forming an indentation on an insertion face of a first part and a projection on a contact face of the first part. An indentation is defined as a depression or impression on a surface. The method continues with the step of driving a flow-drill screw into the first part, the projection being in contact with a second part. The flow-drill screw is driven through the first part and the second part to secure the first part to the second part.

[0012] According to further aspects of the above procedure, the indentation can be conically shaped. The sides of the indentation can be arranged at an angle between 30° and 60° with respect to a surface adjacent to the indentation on the insertion side of the first part. The flow-drill screw can have a convexly curved tip that engages the indentation at a point spaced upwards from a base region of the indentation. The indentation can be an elongated slot comprising tapered sides extending from the insertion side of the first part to a base region. The base region referred to here is the deepest part of the indentation and includes the pointed end of the indentation. The indentation has a feed surface between the sides and the insertion side.

[0013] According to further aspects of the present disclosure, an adhesive can be applied between the contact side of the first part and the second part. The projection penetrates the adhesive, thereby enabling heat transfer from the projection to the second part without the adhesive insulating the second part from the heat generated in the projection.

[0014] According to another aspect of the present disclosure, a method for assembling parts using a flow-drill screw is disclosed, comprising the steps of forming an opening in a first part and forming an indentation in a second part. The first part is then joined to the second part, with the opening aligned with the indentation. A flow-drill screw is then inserted through the opening and turned into the indentation to secure the first part to the second part.

[0015] According to another aspect of the present disclosure, a method for inserting a flow-drill screw into an arrangement is disclosed. The method comprises the step of forming an indentation on an insertion face of a part. The flow-drill screw is then rotated against a contacted area of ​​a side wall of the indentation to generate concentrated heat over a base area without initially contacting the base area of ​​the indentation. A contacted area in the indentation is softened, and the contacted area and the base area are formed into a threaded collar.

[0016] According to further aspects of the disclosure of the latter method, the method may include the step of rotating the flow-drill screw to secure it in the threaded collar. The flow-drill screw has a tip that includes an arcuate convex sidewall terminating in a point. The convex sidewall of the tip contacts the indentation at a location spaced from the base area.

[0017] The above aspects of the present revelation and further aspects are described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective partial view of two parts assembled with multiple flow-drill screws, assembled according to the disclosed method. Fig. Figure 2 is a partial top view of a conical indentation that can be used in the practical implementation of an embodiment of the disclosed method. Fig. Figure 3 is a partial top view of an elongated slot-shaped indentation that can be used in the practical implementation of an alternative embodiment of the disclosed method. Fig. Figure 4 is a schematic cross-sectional view of a flow-drill screw as it is first inserted and rotated into an indentation in a first part, which is to be attached to a second part by the flow-drill screw and an adhesive. Fig. 5 is a Fig. 4 similar view showing how the flow drill screw softens the first part, forms a sleeve with the material displaced from the first part, and penetrates the second part. Fig. 6 is a Fig. 4 similar views showing how the flow drill screw is fully inserted into the assembly, connecting the first and second parts through the threaded connection and head. Fig. Figure 7 is a schematic cross-sectional view of a flow-drill screw as it is first inserted through a previously formed hole in a first part and rotated in an indentation in a second part to attach the first part to a second part. Fig. 8 is a Fig. 7. Similar view showing how the flow drill screw softens the second part and forms a sleeve with the material displaced from the second part. Fig. 9 is a Fig. 7 similar view showing how the flow drill screw is fully inserted into the assembly, connecting the first and second parts through the threaded connection and head. DETAILED DESCRIPTION

[0018] The embodiments shown are disclosed with reference to the drawings. It is understood, however, that the disclosed embodiments are merely examples, which can be implemented in various and alternative forms. The figures are not necessarily to scale, and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed here should not be interpreted as limiting, but merely as a representative basis for teaching a person skilled in the art how to use the disclosed concepts.

[0019] With reference to Fig. Figure 1 shows a first part 10 and a second part 12, which are partially secured to each other by flow-drill screws 16. The flow-drill screws 16 are shown in a position for insertion into several indentations 18, which are conically shaped and recessed into the first part 10.

[0020] With reference to Fig. 2. The impressions 18 comprise a conical side wall 22 that extends to a base region 24. The base region 24 is pointed and is the deepest section of the depression forming the impressions 18. A feed surface 26 is provided on the impression 18, extending from the feed side 28, or feed surface, to the conical side wall 22.

[0021] With reference to Fig. In an alternative embodiment, a slot-shaped recess 30 can be provided, comprising arcuate side walls 32 extending from a feed surface 34 located between the side walls 32 and the insertion face 28. The elongated slot-shaped recess facilitates the installation of the flow-drill screws, as flow-drill screws 16 can be installed within a range of positions defined by the slot-shaped recess 30 and, for installation between the side walls 32, which extend in the longitudinal direction of the vehicle, only need to be precisely aligned in the lateral or transverse direction of the vehicle.

[0022] With reference to Fig. Figures 4-6 illustrate an embodiment of the method for reducing the cycle time for flow-drill screw operations, wherein an upper part 36 is arranged above a lower part 38. It is understood that reference to the upper part 36 and the lower part 38 refers to their position in the figures and does not restrict the spatial orientation of the two parts 36 and 38, which in actual use may be reversed or provided as an inner and an outer wall.

[0023] With reference to Fig. 4 The upper part 36 includes a projection 40 formed in the part 36 when the indentation 18 is formed in the upper part 36. The indentation 18 is preferably formed by a sheet metal forming operation as part of the process for forming the upper part or the outer cladding. The indentation 18 is preferably formed during the stamping / forming process. The indentation 18 provides a self-alignment point for the flow-drill screw or other thread-cutting fastener. The upper part 36 is assembled with the lower part 38 such that the projection 40 contacts the lower part 38. The tip 42 of the flow-drill screw 16 is spaced apart from the base region 24 of the indentation 18. The base region 24 of the indentation 18 is the pointed endpoint of the recess or indentation 18.

[0024] The flow-drill screws 16 are provided with several threads 44, which serve the purpose of forming threads in the sleeve formed by the flow-drill screws 16 and furthermore engage the formed threads to secure the flow-drill screws 16, as with reference to Fig. 5 and Fig. 6 will be explained below.

[0025] The tip 42 of the fastening element 16 has a convex side wall 43 that forms an arcuate curved outer surface. The convex side wall 43 contacts the conical side wall 22 of the indentation 18 at a point located a distance above the base region 24. The side wall 22 of the indentation 18 is preferably arranged at an angle between 30° and 60° to a central axis of the indentation 18. The curvature of the convex side wall 43 is selected such that the tip 42 contacts the side wall 22 at a contact band 46.

[0026] The tip 42 of the flow-drill screws 16 contact the indentation 18 on the contact band 46, which is located at a distance above the tip 42 of the flow-drill screws 16 and above the base region 24 of the indentation 18. The contact band 46 is the point where the convex side wall 43 of the tip 42 engages the conical side wall 22 of the indentation 18. Friction on the contact band 46 generates heat, which is directed into a heat concentration region 48, shown on the upper part 36.

[0027] An adhesive 50 is shown between the upper part 36 and the lower part 38. The projection 40 penetrates the adhesive 50 to minimize the thermal insulation of the lower part 38 from the upper part 36 in the area around the projection 40. Heat generated by the rotation of the flow-drill screws 16 softens the upper part 36 and is transferred directly to the lower part 38 via the projection 40.

[0028] As in Fig. As shown in Figure 5, the tip 42 of the flow-drill screw 16 penetrates the upper part 36 and enters the lower part 38. As the planking is heated by the tip 42 of the flow-drill screw 16, the displaced material 54 is softened by the upper part 36 and the lower part 38.

[0029] With reference to Fig. 6 forms the displaced material (in Fig. (5 shown) a threaded sleeve 56. Threads 60 in the threaded sleeve 56 are formed by the threads 44 of the flow-drill screws 16. A threaded bore 62 is also formed in the lower part 38. The cycle time required to form the threaded bore 62 is reduced because heat is readily transferred from the projection 40 to the lower part 38. The flow-drill screw 16 includes a head 64 that engages the insertion face 28 of the upper part 36 to secure the upper part 36 to the lower part 38. The threaded sleeve 56 acts as a cylindrical bushing that surrounds the installed flow-drill screw 16. The tip 42 of the flow-drill screw 16 protrudes below the lower part 38, as shown. The adhesive 50 does not isolate the lower part 38 from the upper part 36 in the area around the projection 40.The heat concentration area 48 is heated by the flow-drill screw 16 engaging the contact band 46 of the impression 18 in frictional engagement, resulting in faster heating and softening of other parts of the impression 18, e.g., the base area 24, which are formed in the upper part 36.

[0030] With reference to Fig. Figures 7-9 show an alternative embodiment of a method for reducing the cycle time for flow-drill screw operations.

[0031] With particular reference to Fig. Figure 7 defines an upper part 70, a hole 72, which is aligned with an indentation 78 formed in a lower part 76. Again, it is understood that reference is made to the upper part 70 and the lower part 76 as shown in the illustration, and that the alignment of the parts is not restricted to a specific angular orientation. A flow-drill screw 16 is inserted through the hole 72 in the upper part 70 and engages the indentation 78 formed in the lower part 76. A projection 80 is created on the reverse side of the lower part 76.

[0032] Impression 78 is made as before with reference to Fig. The upper part 70 is formed in a stamping / forming process, as described in Figures 4-6, before being joined to the lower part 76. The indentation 78 comprises a base region 82, which includes the pointed, recessed tip of the indentation 78. The tip 42 of the flow-drill screw 16 does not contact the base region 82, but instead contacts the indentation 78 in the area of ​​the contact band 86. Rapid rotation of the flow-drill screw 16 causes the tip 42 to engage the contact band 86 in frictional engagement, creating a heat concentration area 88.

[0033] With reference to Fig. 8 As the flow-drill screw process continues, the tip 42 heats the impression 78 and produces displaced material 90 that flows along the tip 42 of the flow-drill screw 16.

[0034] With reference to Fig. 9 is made from the displaced material 90 (in Fig. (8 shown) a threaded sleeve 92 is formed. The threaded sleeve 92 comprises several threads 94 formed by the threads 44 of the flow-drill screw 16. The head 64 of the flow-drill screw 16 engages the upper part 70 and is tightened in the threads 94 to secure the upper part 70 to the lower part 76. In the embodiment of Fig. Figure 9 shows no adhesive between the upper part 70 and the lower part 76; however, it is understood that adhesive could be provided between the upper part 70 and the lower part 76 if additional holding force is required. If adhesive is provided, it is preferably applied at a distance from the area joined by the flow-drill screw 16 to avoid interfering with the flow-drill screwing process or causing deterioration of the adhesive.

[0035] The embodiments described above are specific examples and do not represent all possible forms of disclosure. The features of the illustrated embodiments can be combined to form further embodiments of the disclosed concepts. The terms used in the description serve to describe rather than limit the scope. The scope of protection of the following claims is broader than that of the specific disclosed embodiments and also includes modifications of the illustrated embodiments.

Claims

[1] Method of assembling parts, comprising: Forming an indentation on an insertion side of a first part and a projection on a contact side of the first part before the first part is assembled with a second part; Inserting a flow drill screw into the first part with the projection in contact with the second part; and Turn the Flow-Drill screw to insert the Flow-Drill screw through the impression and drive the second part to secure the first part to the second part. [2] The method of claim 1, wherein the impression is conically shaped. [3] The method of claim 2, wherein the indentation has a side wall disposed at an angle of between 30° and 60° with respect to a surface adjacent to the indentation on the insertion side of the first part. [4] The method of claim 1, wherein the flow drill screw has a convexly curved tip that engages the impression at a location spaced upwardly from a base portion of the impression. [5] The method of claim 1, wherein the indentation is an elongated slot comprising tapered sides extending from the insertion side of the first part to a base region. [6] The method of claim 1, wherein an adhesive is applied between the contact side of the first part and the second part. [7] A method according to claim 6, wherein the projection penetrates into the adhesive and wherein heat is transferred directly from the projection to the second part, thereby minimizing the extent of thermal insulation of the second part from heat developed in the projection by the adhesive. [8] The method of claim 1, wherein the impression has sides extending at an angle between 30 and 60 degrees. [9] The method of claim 1, wherein the impression has a feed surface between the sides and the insertion side. [10] Method of assembly comprising: forming an opening in a first part; Forming an impression in a second part before the first part is assembled with the second part; Installing the first part with the second part, with the opening aligned with the impression; Inserting a flow drill screw through the opening; and Turning the Flow-Drill screw to drive the Flow-Dill screw into the impression, to secure the first part to the second part. [11] The method of claim 10, wherein the impression is conically shaped. [12] The method of claim 11, wherein the indentation comprises a side wall disposed at an angle of between 30° and 60° with respect to a surface adjacent to the indentation on an insertion side of the first part. [13] The method of claim 10, wherein the flow drill screw has a convexly curved tip that engages the impression at a location spaced upwardly from a base portion of the impression. [14] The method of claim 10, wherein the indentation is an elongated slot comprising a pair of tapered sides extending from an insertion surface of the first part to a base region. [15] The method of claim 14, wherein the pair of tapered sides extend at an angle of between 30 and 60 degrees. [16] The method of claim 15, wherein the impression has a feed surface between the tapered sides and an insertion surface. [17] A method of inserting a flow drill screw into an assembly, comprising: Forming an impression on an insertion side of a part; Rotating the flow drill screw against a contacted area of ​​a sidewall of the impression to generate concentrated heat over a base area without first contacting the base area of ​​the impression; Softening the contacted area in the impression; and Forming the contacted area and the base area into a threaded collar. [18] The method of claim 17, further comprising: Turn the flow drill screw to secure the flow drill screw in the threaded collar. [19] The method of claim 17, wherein the flow drill screw has a tip including an arcuate convex sidewall terminating in a point, the convex sidewall of the tip contacting the impression at a location spaced from the base region. [20] The method of claim 19, wherein the indentation comprises a feed surface between the side wall and the lead-in side of the part.

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