Radial incremental forming

A method of radial incremental forming a component having a component inner mold line (IML) includes providing a mandrel having geometry configured to mate with the IML. The method also includes inserting the mandrel into a tubular workpiece composed of a formable material, to thereby sleeve the workpiece over the mandrel. The method additionally includes mounting the workpiece sleeved over the mandrel onto a drive mechanism configured to rotate the mandrel and having a forming tool configured to shift relative to the workpiece. The method further includes regulating, according to provided toolpath instructions, the drive mechanism to rotate the workpiece sleeved over the mandrel in concert with shifting the forming tool relative to the workpiece to incrementally deform the workpiece therewith over the mandrel and thereby form the component. A tool system having an electronic controller may employ the subject method to radially incrementally form a component.

INTRODUCTION

The present disclosure relates to a system and a method for radial incremental forming of a component.

Forming is a process of fashioning parts and objects through mechanical deformation. During such a forming process, a workpiece is generally reshaped without adding or removing material, such that its mass remains unchanged. Forming operates via elastoplastic deformation, whereby the workpiece experiences both elastic and plastic strain. The plastic strains contribute to permanent changes in workpiece shape, while the elastic strain is experienced only when the workpiece is being loaded. Through the cumulative action of plastic strains, a part is physically shaped to achieve a component having a desired inner mold line (IML).

Forming is frequently used in metalworking to fashion parts and objects from appropriate metal workpieces or blanks. Forming processes may employ specialty equipment such as machine presses and dies to apply high loads thereby generating the plastic strain required to produce the requisite shape. The metalworking process may be a single stage operation, where every stroke of the equipment produces the desired form on the workpiece, or the process may occur through a series of steps or stages.

Many forming processes start with a sheet metal blank which is planar, i.e., flat, however such planar sheets are not ideal for producing parts which are tubular in shape. For example, deep drawing of a tall cylindrical shape is prone to splitting on the walls of the cylinder. Some forming processes exist which begin operation on a metal tube in lieu of a flat sheet. Such processes include flow forming and metal spinning. These processes, which are similar in nature, are generally limited to producing axisymmetric parts. Thus, a need exists for a process to produce non-axisymmetric tubular parts from metal (or other formable material) tubing.

SUMMARY

A method of radial incremental forming a component having a component inner mold line (IML) includes providing a mandrel having geometry configured to match the IML. The method also includes inserting the mandrel along an axis into a tubular workpiece from a formable material, to thereby sleeve the tubular workpiece over the mandrel. The method additionally includes mounting the tubular workpiece sleeved over the mandrel onto a drive mechanism configured to rotate the mandrel about the axis. The drive mechanism includes a forming tool, such as a stylus, configured to shift relative to the tubular workpiece and apply a forming force to the tubular workpiece. The method also includes providing toolpath instructions configured to regulate operation of the drive mechanism. The method further includes regulating, according to the toolpath instructions, the drive mechanism to rotate the tubular workpiece sleeved over the mandrel in concert with shifting the forming tool relative to the workpiece to incrementally deform the tubular workpiece therewith over the mandrel and thereby form the component.

Providing the mandrel may include constructing the mandrel from multiple individual sections. In such an embodiment, the method may additionally include removing the multiple individual sections of the mandrel from the formed component without disturbing the component IML. Such mandrel sections may include provisions for enabling retraction thereof.

Providing the mandrel may also include constructing the mandrel from a material configured to be dissolved in a fluid, such as water. For example, the dissolvable mandrel may be constructed from Aquacore™ or SOLCORE™ material. In such an embodiment, the method may additionally include dissolving the mandrel to remove the mandrel from the formed component without disturbing the component IML.

Alternatively, the mandrel material may be any combination of one or more of polymer, timber, fiber board, metal, fiberglass, carbon fiber reinforced plastic (CFRP).

The mandrel geometry, which matches the IML of the component geometry, may have an axisymmetric or non-axisymmetric shape.

The toolpath instructions may include a radial level toolpath and a lace toolpath. In such an embodiment, the method may further include applying to the tubular workpiece, via the forming tool, the radial level toolpath followed by the lace toolpath to thereby minimize localized springback (due to an oil canning phenomenon) of the tubular workpiece and achieve a desired component IML.

According to the method, shifting the forming tool may be accomplished in a radial and/or axial direction relative to the tubular workpiece in concert with a rotation of the mandrel.

The tubular workpiece material may be a formable metal, such as an aluminum alloy, mild steel, stainless steel, titanium, and titanium-based alloys, nickel-based alloys such as Inconel, copper, bronze, brass, tin, or the like. As a non-limiting example, the initial sheet metal tubing may be a 2024-0 aluminum alloy tube with a 1.0-inch outer diameter and a wall thickness of 0.049 inches. In alternative embodiments, the workpiece material may be non-metallic, such as carbon fiber, and a have different wall thickness and/or outer diameter.

The drive mechanism may be a multi-axis drive mechanism controlled via an electronic controller programmed with the toolpath instructions. Such a multi-axis drive mechanism may, for example, be a computer numerical control (CNC) 4-axis lathe, a 5-axis CNC machine, or a multi-axis robot. The toolpath instructions may specifically include a plurality or sets of coordinates. According to the method, each set of the subject coordinates may identify a mandrel rotation, an axial shift of the forming tool, and a radial shift of the forming tool at a predetermined time relative to commencement of the forming of the component. In such an embodiment, the method may further include regulating the drive mechanism, via the electronic controller, to form the component.

According to the method, providing the toolpath instructions may include providing a digital definition of a surface geometry defining the component IML. Providing the toolpath instructions may also include generating a tool offset surface geometry based on the component IML surface geometry and transforming, via inverse cylindrical mapping, the tool offset surface geometry from a first topological space into a second topological space. Providing the toolpath instructions may additionally include intersecting the tool offset surface geometry in the second topological space with a plurality of parallel planes defined in the second topological space, to thereby obtain a plurality of toolpath contours connected to form a toolpath in the second topological space. Providing the toolpath instructions may also include transforming, via cylindrical mapping, the toolpath from the second topological space to the first topological space. Providing the toolpath instructions may further include selecting a plurality of points spaced along the toolpath. In such an embodiment, each of the plurality of points may be defined by one of the sets of coordinates (defining the mandrel rotation, the axial shift of the forming tool, and the radial shift of the forming tool at the corresponding predetermined time). Each mandrel rotation, axial shift of the forming tool, and radial shift of the forming tool may be identified relative to a predefined reference point on the forming tool.

An additional embodiment of the present disclosure is a tool system for radial incremental forming a component having a component IML.

DETAILED DESCRIPTION

Embodiments of the present disclosure as described herein are intended to serve as examples. Other embodiments can take various and alternative forms. Additionally, the drawings are generally schematic and not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

Referring to the drawings in which like elements are identified with identical numerals throughout,FIGS.1-13illustrate manufacturing of a component10having an inner mold line (IML)10A from a tube-shaped or tubular workpiece12(shown inFIGS.4A and4Bin a cutaway form) having a longitudinal axis15. The tubular workpiece12is generally a pre-cut piece of a tube, e.g., a pipe segment, made from a formable material. The tubular workpiece12may, for example, be composed of formable metal such as aluminum alloy, mild steel, stainless steel, titanium and titanium-based alloys, nickel-based alloys such as Inconel, copper, bronze, brass, tin, or the like. As a non-limiting example, the initial sheet metal tubing may be a 2024-0 aluminum alloy tube with a 1.0-inch outer diameter and a wall thickness of 0.049 inches. In alternative embodiments the workpiece material may be non-metallic, such as carbon fiber, and a have different wall thickness and/or outer diameter. The component IML10A may have a non-axisymmetric shape, i.e., a shape which varies asymmetrically with respect to rotation about the axis15(shown inFIGS.4A and4B). Alternatively, the component contour10A may have an axisymmetric shape, i.e., a shape which is symmetrical with respect to rotation about the axis15(not shown).

The system and method disclosed in detail below are specifically established to manufacture a component via radial incremental forming. As disclosed herein, radial incremental forming is capable of progressively deforming a tube-shaped or tubular workpiece, such as the workpiece12, to generate therein various features and shapes, such as pockets and grooves. Moreover, while radial incremental forming may be used to generate axisymmetric shapes, i.e., having rotational symmetry with respect to a central axis, the process is particularly useful for generating non-axisymmetric features and shapes, i.e., where the component IMLs are devoid of rotational symmetry with respect to a central axis of the component.

A tool system14for radial incremental forming of the component10having the IML10A is shown inFIGS.1and1A. As shown inFIGS.3A and3B, the system14includes a mandrel or die16having a mandrel outer mold line (OML)16A. The mandrel OML16A may be additively manufactured or alternatively may be lathed, machined, or otherwise fashioned from a bar stock of suitable material to produce one or more components that collectively comprise a mandrel. The OML16A of the mandrel16has a surface geometry which mates with the IML10A of the component10in one or more locations. The mandrel16is generally configured, i.e., sized and shaped, to be inserted into the tubular workpiece12, such that the tubular workpiece becomes sleeved over the mandrel, as shown inFIGS.4A and4Bin a cutaway form.

With resumed reference toFIG.1, the tool system14also includes a drive mechanism20configured to mount, hold, and rotate the workpiece12sleeved over the mandrel16about the axis15. While the drive mechanism20is specifically depicted inFIG.1as a computer numerical control (CNC) lathe, such as a 4-axis machine, it is understood that other embodiments may have different drive mechanisms which can be configured to perform the same task. Alternative embodiments of the drive mechanism20may, for example, include a multi-axis robot or a 5-axis CNC machine. The CNC lathe drive mechanism20may employ a rotatable spindle22with chucks24A,24B, and24C centered on the axis15and fixed relative to the spindle22. While in the present embodiment the rotatable spindle22has three chucks, other spindle embodiments may have fewer or greater number of chucks. In many embodiments, the drive mechanism20is configured to actuate the chucks24A,24B, and24C radially inwards towards axis15so that they may firmly grip the workpiece12sleeved over the mandrel16.

The CNC lathe drive mechanism20may also include an adjustable tailstock26for supporting the opposite end of the mandrel16. For example, the tailstock may26be configured to move horizontally, such as along a guide rail28. The CNC lathe drive mechanism20may additionally include an electric motor (not shown) operatively connected to the spindle22and thereby configured to rotate the workpiece12sleeved over the mandrel16about the axis15. The CNC lathe drive mechanism20additionally employs an electronic processor and servomechanism(s) (not shown) to regulate the rate of movement of the spindle22. Furthermore, the CNC lathe drive mechanism20may include a control panel and display30configured to permit monitoring and/or manual control of the forming process.

With continued reference toFIG.1, the system14also includes a forming tool, such as a stylus,32having a centerline33and mounted into, e.g., inserted and secured within, a collet34A. As will be described in greater detail below, the forming tool32is specifically configured to shift relative to the tubular workpiece12and apply a forming force F (shown inFIG.1A) to the tubular workpiece. In at least one embodiment of the drive mechanism20, the collet34A and other collets, such as collets34B,34C,34D, are mounted along the circumference of a tool change carousel36. This tool carousel36may hold multiple forming and/or cutting tools (not shown) and may be connected to a servomechanism (not shown), such that the subject tools may be interchanged automatically. The tool carousel36forms part of a lathe turret assembly38which is moveable both horizontally and vertically using, for example, guide rails40and42respectively via servomechanism(s). In at least one alternative embodiment, the drive mechanism20may be characterized by an absence of a tool change carousel, such that the collet is directly connected to the moveable lathe turret assembly38.

As shown inFIG.1A, the forming tool32has an operative tool tip32A. The tool tip32A may be hemispherical (as shown) or have another profile which is axisymmetric with respect to the centerline33of the forming tool32. For example, the forming tool32may be a solid metal cylinder having a round fillet at the intersection of its flat base and side walls, i.e., the forming tool may have a bullnose shape. As previously mentioned, the forming tool32is mounted into a collet34A which is either connected to the tool change carousel36which is in turn part of the lathe turret assembly38or, alternatively, directly connected to the lathe turret assembly.

The servomechanism (not shown) which drives the lathe turret assembly38is configured to impart at least two degrees of freedom of movement to the forming tool32. One degree of freedom allows translation of the forming tool32in a direction parallel to the axis15. The other degree of freedom describes movement of the forming tool32in a direction which is orthogonal to the axis15. For example, the axis15may be horizontal, i.e., level with ground, and the first degree of freedom may therefore be a horizontal translation of the forming tool32. Correspondingly, the second degree of freedom in this non limiting example may be configured as a vertical translation of the forming tool32.

With reference toFIG.1, the system14additionally includes an electronic controller44, which is in operative communication with the drive mechanism20and the lathe turret assembly38. The electronic controller44may be a central processing unit (CPU) of the CNC lathe or a dedicated separate electronic control unit (ECU) having a microprocessor. For example, the ECU may be a FANUC or SIMENS controller, or the like. To support manufacturing the component10, the electronic controller44specifically includes a processor and tangible, non-transitory memory, which includes instructions programmed therein for processing data signals and executing commands. The memory may be an appropriate recordable medium that participates in providing computer-readable data or process instructions. Such a recordable medium may take many forms, including but not limited to non-volatile media and volatile media. Non-volatile media for the electronic controller44may include, for example, optical or magnetic disks and other persistent memory. Volatile media may include, for example, dynamic random-access memory (DRAM), which may constitute a main memory.

The instructions programmed into the electronic controller44may be transmitted by one or more transmission medium, including coaxial cables, copper wire and fiber optics, including the wires that comprise a system bus coupled to a processor of a computer, or via a wireless connection. Memory of the electronic controller44may also be transmitted and/or stored by means of a Universal Serial Bus (USB) device, flexible disk, hard disk, magnetic tape, another magnetic medium, a CD-ROM, DVD, another optical medium, etc. The electronic controller44may be configured or equipped with other required computer hardware, such as a high-speed clock, requisite Analog-to-Digital (A/D) and/or Digital-to-Analog (D/A) circuitry, input/output circuitry and devices (I/O), as well as appropriate signal conditioning and/or buffer circuitry. Subsystems and algorithm(s), indicated inFIG.1generally via numeral46, required by the electronic controller44or accessible thereby may be stored in the memory of the controller and automatically executed to facilitate operation of the system14.

The electronic controller44is configured, via input from toolpath instructions48(generated using method100to be described in detail below, or otherwise supplied) to regulate the drive mechanism20, and specifically the rotation of spindle22in concert with the movement of lathe turret assembly38. In particular, the electronic controller44regulates electric motors, e.g., servomotors, such that the rotation of the workpiece12about the axis15, as well as the translations in two orthogonal directions of the lathe turret assembly38, match the information given by the toolpath48for a given time value. At least in some instances, the resulting movement, i.e., magnitude of shift, of the forming tool32is intended to cause interference of the forming tool with the workpiece12, and as a result the forming force F, depicted inFIG.1A, is applied to the workpiece12to thereby generate elastoplastic strain in the workpiece12. The plastic component of the elastoplastic strain generated via application of the force F causes permanent deformation in the workpiece12. Accordingly, the workpiece12is deformed incrementally, via the described synchronized movements of the mandrel16and the forming tool32, into the desired component10having the IML10A. Although the force F is depicted in1A as a downwards acting load, it is understood that the angle of force will change depending on the contact between the forming tool32and the workpiece12, and, correspondingly, there may exist a horizontal component of the force F which is not represented inFIG.1A.

Specifically in the embodiment of the component10defined by a non-tapered IML10A, the formed component may interlock with the mandrel16once the forming operations are complete. An example of such an embodiment of the component10is shown inFIG.2. In the embodiment ofFIG.2, a pocket50is to be formed into the initial tubular workpiece12. Once forming operations are completed, due to the pocket50, removal of the mandrel16from the formed component10may pose a challenge. To address such an eventuality, the mandrel16may be constructed from a material52configured to be dissolved in a fluid, such as water. For example, the mandrel16may be machined from a block of Aquacore™ or SOLCORE™.FIG.3Ashows an embodiment where the mandrel16, designed to form the basis for the component10, is to be constructed with the subject dissolvable material52. The dissolvable material52is intended to enable the mandrel16to be removed from the formed component10without disturbing the component IML10A. To dissolve the mandrel16, the formed component10with the mandrel maintained therein would be soaked in the fluid for a predetermined amount of time.

Alternatively, the mandrel16may be constructed from multiple individual sections, such as sections16-1,16-2,16-3, and16-4as shown inFIG.3B. Sections16-1,16-2,16-3, and16-4are specifically configured to be removed from the formed component10without disturbing the component IML10A. For example, sections16-3and16-4may be removed from either end of the formed component first, thereby freeing up space to allow the removal of remaining sections16-1and16-2. The sections16-1and16-2may then be removed from the formed component10in any desired order. In a multi-part mandrel16configuration, such as that disclosed inFIG.3B, the material may be any combination of one or more of polymer, timber, fiber board, metal, fiber, glass, or carbon fiber reinforced plastic (CFRP).

The electronic controller44may be programmed with an ASCII text file having toolpath instructions48, such as GCODE, to command the tool system14to drive the forming tool32and the spindle22, such that the forming tool is in its requisite position relative to the workpiece12for each instance of time values specified in the file. Such a file is generally referred to as a “toolpath”, and is typically, but not necessarily, generated by a software program external to the electronic controller44and stored among the previously noted algorithm(s)46(shown inFIG.1). The subject program may also be referred to as a toolpath generation program or Computer Aided Manufacturing (CAM) software.FIG.15depicts an exemplary method100, that describes, in simplified form, a toolpath generation program for creating a useable toolpath (e.g., the toolpath instructions48) for radial incremental forming of the component10, constructed as set forth herein. The created toolpath is then executed as code or instructions by an electronic control unit, such as the electronic controller44of the exemplary tool system14shown inFIG.1. Specifically, the toolpath instructions48may include multiple sets of coordinates, wherein each set of subject coordinates identifies a mandrel16rotation, an axial shift of the forming tool32, and a radial shift of the forming tool at a predetermined time instance relative to commencement, i.e., time zero, of the component10forming process.

The method100initiates in Block102, where a part geometry for the component10is input into a toolpath generation program, e.g., by uploading a corresponding CAD file into Block102. The subject CAD file includes at least a digital definition of a surface geometry of the component10which defines the IML10A. Such a CAD file may describe a set of trimmed parametric surface entities and their related entities, such as edges and vertices, for example with STEP, Parasolids, ACIS, or IGES files. Alternatively, the file may describe a set of vertices and connecting polygons, such as is the case with STL, PLY, VRML files, or the like. Furthermore, the CAD data in Block102may be in the form of a native file format to CAD software, such as 3DEXPERIENCE®, CATIA®, SOLIDWORKS®, CREO®, SOLIDEDGE®, Siemens NX®, or the like. Specifically, at Block104, the geometry of the forming tool32is defined by providing an outer diameter and a cross section for the tool tip32A. For example, a circular cross section shape and an outer diameter of 30 mm would be selected if a 30 mm diameter hemispherical forming tool is to be used. Other diameters and cross sections shapes are possible.

At Block106, the method100includes determining a sheet offset surface of the component10(shown inFIG.5). The subject approach includes initially determining a sheet offset surface of the workpiece12via offsetting the geometry of the component10by a prescribed distance normal to the surface of the workpiece12(which may be the workpiece material thickness) to allow space for the deformed workpiece to lie between the tool tip32A and the mandrel16. Block106may be excluded from the method100, if the workpiece material thickness variable is properly accounted for in Block104. The method then proceeds to generate a further offset surface based on the sheet offset surface, which accounts for the forming tool32shape. The subject further offset surface, defined as the tool offset surface10-1, satisfies the property that when a specified reference point on the forming tool32is coincident with a point on the tool offset surface10-1, the forming tool will contact the sheet offset surface without intersecting. In other words, if the forming tool32is positioned with its reference point anywhere on the tool offset surface10-1, it will just touch the sheet offset surface.FIG.5illustrates one possible tool offset surface10-1corresponding to forming the component10shown inFIG.2.

The tubular initial shape of the workpiece12means that it is often desirable to incrementally deform the workpiece along contours which are a constant distance away from the axis15, about which the mandrel16is rotated. To facilitate a toolpath with the subject property, the method100proceeds, at Block108, to transform or map the tool offset surface10-1from its existing topological space, i.e., a first topological space, into a second topological space via inverse cylindrical mapping. Such a transformation may be visualized as a map which unrolls the surface geometry so that it is flat in regions which are a constant distance away from axis15in the first topological space. Specifically, the coordinates of in the subject map are translated from a solid cylinder into a Euclidean space. The inverse cylindrical map ϕ−1:3→3referred to herein takes in three coordinates x, y, z and returns three coordinates u, v, w as follows:

u=yv=r0⁢tan-1(zx)w=x2+z2
The above relationships refer to a tube having the axis15coincident with the y axis in a first topological space transforming to a second topological space, where subject cylinders are mapped into w planes. The variable r0may be chosen as any positive real number and is solely used for the purposes of scaling the transformed shape to aid in visualization. For example, a value of r0=1 may be used. Thus, the subject transformation permits the circular wall of a cylinder, such as characterizing the workpiece12, to be mapped into a flat and level plane.

At Block110the tool offset surface10-1geometry defining the IML10A in the second topological space is intersected with a plurality of parallel planes, defined in the second topological space, to obtain a plurality of toolpath contours connected to form a toolpath in the second topological space. At Block112the contours obtained in Block110are then combined to form toolpath instructions48for the forming tool32in the second topological space.FIG.6Aillustrates an exemplary toolpath generated by planes of constant value w which are equally spaced apart in the second topological space and parallel to the flat portions of the tool offset surface10-1in the second topological space (i.e., equally spaced level planes in the second topological space). Toolpaths thus produced by level planes will herein be referred to as “radial level” toolpaths48A. Alternatively, a plurality of equally spaced planes in a direction orthogonal to the flat portions of the tool offset surface10-1are illustrated inFIG.6B. Toolpaths thus produced by orthogonal planes (i.e., planes of constant u value or planes of constant v value or any linear combination thereof) will herein be referred to as “lace” toolpaths48B.

At Block114the method100proceeds to transform the toolpath from the second topological space back into the first topological space using cylindrical mapping. Such a transformation may be visualized as wrapping the toolpath around the mandrel16. The cylindrical map ϕ:3→3referred to herein takes in three coordinates u, v, w and

returns three coordinates x, y, z as follows:
x=wcos(v/r0)
y=u
z=wsin(v/r0)
The above relationships refer to a second topological space where w planes are mapped back into cylinders which have centerlines which are coincident with the y axis in a first topological space. The value of r0but should be consistent with the value chosen for the inverse map.

At Block116a plurality of points is selected from among the points spaced along the toolpath48in the first topological space. As described above, each of the plurality of points may be defined by one of the sets of coordinates representing the mandrel16rotation, the axial shift of the forming tool32, and the radial shift of the forming tool32at the predetermined time instance relative to commencement of forming the component10. The selected points may therefore represent, for a given value of time relative to the start of the operation, the required position of the forming tool32together with the required mandrel16rotation, where each required position(s) and rotation(s) is relative to a given reference point on the forming tool. At Block118the coordinates of the selected points are then saved to a file together with a timestamp which corresponds to the appropriate time value at which the subject rotation of the mandrel16and the attendant translational position of forming tool32are required. In other words, the resultant file provides a time value for each rotation of the mandrel16and the corresponding position of the forming tool32. The subject saved file may be in an ASCII text file format such as G-code or Aptsource instructions, readable by the electronic controller44.

For several reasons, application of the force F along the radial level toolpath may generate significant springback of the tubular workpiece12material. Firstly, curling of the workpiece12typically occurs along the toolpath in a direction orthogonal to both the motion of the forming tool32and the forming tool centerline33. Secondly, as the radial levels increase in depth, the workpiece12material is being compressed into an increasingly smaller space, thereby risking localized buckling of the sheet. Combined, the above noted effects create a strong likelihood of a phenomena referred to as oil canning, whereby a pillow shaped portion of workpiece12material is observed at the base of the pocket50type feature. This oil canning phenomenon is well known to those skilled in the art of Incremental Sheet Forming (ISF).FIG.8illustrates a finite element simulation result showing the deformed workpiece12after the radial level toolpath shown inFIG.7Ahas been completed.FIG.8depicts a pillow of localized springback54that is due to the aforementioned oil canning phenomenon.

It has been observed that the issue of oil canning may be effectively mitigated by performing the lace toolpath48B. The lace toolpath48B, as detailed previously and illustrated inFIG.7B, includes connected ring-shaped contours which follow along the component IML10A.FIG.9is an illustration of a finite element simulation result showing the deformed workpiece12after both the radial level toolpath48A ofFIG.7Aand the lace toolpath48B ofFIG.7Bhave been completed. As depicted inFIG.7B, the pillow of localized springback54has been mostly eliminated through the action of the lace toolpath48B following the radial level toolpath48A, leaving the IML of the workpiece12in the vicinity of the pocket50much closer to the desired component IML10A.

FIG.10shows the component10with alternative geometry, having a more complex IML as compared to the embodiment of the component10shown inFIG.2, with corresponding IML10A and axis15for the purpose of illustrating capabilities of the radial incremental forming process.FIG.11Ashows a possible embodiment of the dissolvable mandrel16, whileFIG.11Bshows a possible embodiment of a multi-part mandrel16, each suitable for radial incremental forming of the component10shown inFIG.10. With reference toFIG.11B, the mandrel assembly16includes a section16-1having an inner hub, an outer hub, and connecting plates arranged therebetween in the forms of spokes. The mandrel assembly16ofFIG.11Balso includes sections16-2to16-9. Mandrel sections16-2through16-9are designed to come into contact with the workpiece12during forming of the corresponding component10. Following the forming operations, section16-1may be slid out of the mandrel assembly16, thereby providing sufficient clearance for parts16-2to16-9to be removed in any desired order.

FIG.12illustrates a finite element simulation result of the deformed workpiece12after the radial level toolpath48A (not shown) has been completed.FIG.12contains multiple pillows of localized springback54due to the aforementioned oil canning phenomenon.FIG.13illustrates a finite element simulation result showing the deformed workpiece12after the radial level toolpath48A (not shown) and the lace toolpath48B (also not shown) have been completed. As discussed with respect to the previous embodiment of the workpiece12, the lace toolpath48B may be employed to significantly reduce the oil canning effect produced by the radial level toolpath48A. Accordingly, as may be seen inFIG.13, the previously shown pillows of localized springback54have been greatly reduced, leaving the contour of the formed workpiece12much closer to the desired IML10A of the component shown inFIG.10.

FIG.14depicts a method200of radial incremental forming a component, such as the component10having the IML10A, and employing the tool system14, as described above with respect toFIGS.1-13. The method200is particularly adapted to generate a component IML10A which has a non-axisymmetric shape, as shown inFIG.2andFIG.10. The method200commences in Block202, where it includes providing the mandrel16. The mandrel16may be fashioned by using additive manufacturing or alternatively from lathing, machining, or otherwise generated from a bar stock of suitable material to produce one or more components that collectively comprise the subject mandrel. The mandrel16has a surface geometry which mates with the IML10A of the component10. As disclosed above, the mandrel16may be constructed from dissolvable material52, such as shown inFIG.3Aor from multiple individual sections, such as sections16-1,16-2,16-3,16-4shown in inFIG.3B. Following Block202, the method proceeds to Block204. In Block204, the method200includes inserting the mandrel16into the tubular workpiece12, to thereby sleeve the workpiece over the mandrel16. Examples of the sleeved tubular workpiece12and mandrel16are shown in a cutaway style inFIGS.4A and4B. After Block204, the method200advances to Block206. In Block206, the method200includes mounting the workpiece12sleeved over the mandrel16onto the drive mechanism20and mounting the forming tool32into the collet34. In Block206, the method may further include applying a suitable lubricant to the outer mold line (OML) of the workpiece12.

Following mounting the workpiece12sleeved over the mandrel16, the method200proceeds to Block208. In Block208, the method200includes supplying the radial level toolpath48A to the electronic controller44, such as in the form of G-code or Aptsource instructions provided via an ASCII text file. The method200then advances to Block210, where the toolpath is used to regulate operation of the drive mechanism20. Specifically, the toolpath is read by the electronic control unit44of the tool system14, which commands, via regulation of the corresponding servomechanism, angular movement between discrete rotational positions of the spindle22driving the sleeved mandrel16in concert with commanding translation, i.e., the magnitudes of shift, of the forming tool32via regulation of the respective servomechanism driving the lathe turret assembly38. As described above, the commanded respective translations, i.e., the magnitudes of shift, of the forming tool32and the attendant rotational positions of the spindle22drive mechanism20are in accordance with the angular, axial, and radial coordinates and corresponding time values given in the radial level toolpath48A.

Following execution of the radial level toolpath48A by the tool system14, the method200then proceeds to Block212where the deformed workpiece12is inspected to determine the difference between the deformed geometry of the workpiece12and the requisite geometry of the component10. The subject difference is then assessed in Block214to determine if the deformed workpiece12is within the specified component tolerances. This inspection step may be informal and qualitative, such as using visual judgment to determine if springback has caused the deformed workpiece to exceed the specified tolerances or, alternatively, the process may include formal and quantitative approaches such as metrology. For example, this step may include laser scanning the deformed workpiece12to generate a point cloud data set, registering this point cloud such that it is in alignment with the component10geometry and then computing the minimum distance between each point and the component10geometry. Such calculations may then be used to generate a map of deviation of the workpiece12geometry from the component10geometry for the purposes of assessing if the workpiece geometry matches the component geometry to within the required tolerances.

Depending on the outcome at Block214, the method200then proceeds to either Block216or Block220. In the event the formed component10does not meet the specified tolerances, the method200proceeds to Block216. In Block216the method200includes supplying the lace toolpath48B to the electronic controller44, such as in the form of G-code or Aptsource instructions given via an ASCII text file. The method200then advances to Block218, where the lace toolpath48B is used to operate the drive mechanism20. Specifically, the lace toolpath48B is read by the electronic controller44of the tool system14, which commands, via regulation of the rotational movement of the spindle22driving the sleeved mandrel16in concert with commanding translation of the forming tool32. The commanded rotations and translations are in accordance with the coordinates and corresponding times given in the lace toolpath48B. Accordingly, over the course of Blocks210-218, the method200includes applying to the tubular workpiece12, via the forming tool32, the radial level toolpath48A followed by the lace toolpath48B to thereby minimize localized springback of the tubular workpiece and achieve the desired component IML10A. The method200then continues to Block220. In the event the formed workpiece12does meet the specified tolerances at Block214, the method200proceeds directly from Block212to Block220.

Following Block220, the method200proceeds to either Block222or Block224, depending on which type of mandrel16has been used. If the mandrel16is composed of a dissolvable material, such as Aquacore™, the method200proceeds to Block222. In Block222, the sleeved mandrel16is soaked in a suitable fluid for a predetermined amount of time to extract the deformed workpiece12. Alternatively, if the mandrel16is constructed from one or more parts which are made of a non-dissolvable material, such as the sections16-1to16-4, the method200proceeds to Block224. In Block224, the mandrel16is separated from workpiece12. Where required, this step may include disassembly of the mandrel sections in a particular order. For example, with reference toFIG.3B, sections16-3and16-4may be removed from the mandrel assembly first. Once the end parts of the mandrel assembly (i.e., sections16-3and16-4) have been removed, sections16-1and16-2will have additional space to move toward axis15, and therefore be free to separate from the component10(i.e., the formed workpiece12) in an unstructured fashion.