Abstract:
An end effector, and methods for constructing composite members, in which a compaction roller and redirect rollers translate synchronously along the compaction axis. Additionally, the end effector includes an advantageous arrangement of spools and rollers that directs tow to the redirect rollers at substantially a right angle. Movement of the compaction roller along the compaction axis induces little, if any, changes in tow tension. The substantially constant tow tension advantageously reduces rewinding of the tow supply spools, which can degrade the quality of the lay up and contribute to despooling problems.

Description:
BACKGROUND 
   1. Technical Field 
   The present disclosure relates to apparatus and methods for constructing composite members. 
   2. Description of Related Art 
   Composite items are typically constructed from layers of material that are laminated together. Some categories of materials used to fabricate composite items include fiber, fabric, tape, film and foil, and each of these categories includes a multitude of diverse materials. For example, typical fibers include glass, carbon, aramid, and quartz. When these fibers are arranged as woven sheets and unidirectional ribbons, they are referred to as fabric and tape, respectively. 
   Material placement is a process used to construct or fabricate composite items. These composite items include relatively simple planar sheets or panels to relatively large complex structures. Many composite items are built up from multiple layers or plies of composite materials. Some composite materials may be pre-impregnated with uncured resin (“prepreg”) or another binding agent. 
   In some applications an end effector of a machine for fabricating composite members arrays a group of prepreg tows into a continuous band and then presses them against the surface of a workpiece. Generally a compaction roller performs the task of pressing the tows against the workpiece. To accommodate misalignments between the end effector and the work-piece and elevation variations on the surface of the workpiece the compaction roller is generally movable toward and away from the end effector. Unfortunately, movement of the compaction roller tends to reduce tension in the tows., which can cause rewinding of the spools that supply the tow, can degrade the quality of the lay-up and can contribute to despooling problems. 
   SUMMARY 
   The preferred embodiments of the present end effector and methods for constructing composite members have several features, no single one of which is solely responsible for their desirable attributes. Without limiting the scope of this end effector and these methods as expressed by the claims that follow, their more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description of the Preferred Embodiments”, one will understand how the features of the preferred embodiments provide advantages, which include decreased complexity and cost as compared to prior art end effectors. 
   One embodiment of the present end effector for constructing composite members comprises an end effector that is configured to apply tow to a composite workpiece. The end effector comprises at least one tow supply spool for supplying tow; at least one redirect roller for changing a direction of travel of the tow; and at least one compaction roller configured to press the tow against the workpiece. The redirect roller and the compaction roller are configured to translate together along a compaction axis of the end effector, and are constrained from translating relative to one another. A direction of travel of the tow toward the redirect roller lies at substantially a right angle to the compaction axis. 
   One embodiment of the present methods for constructing composite members comprises the steps of: applying tow to a composite workpiece using an end effector; compacting the tow against the workpiece using a compaction roller; redirecting the tow toward the compaction roller using a redirect roller; translating the compaction roller and the redirect roller together along a compaction axis of the end effector; and feeding the tow toward the redirect roller at substantially a right angle to the compaction axis. The redirect roller and the compaction roller are constrained from translating relative to one another. 
   Another embodiment of the present end effector for constructing composite members comprises a method of manufacturing an aircraft, the method including at least a pre-production phase and a production phase. The method comprises the steps of: designing the aircraft, including subassemblies, and components therefor; specifying and procuring materials; fabricating the components from the materials; assembling the subassemblies by combining subsets of the components; and assembling the aircraft by combining subsets of the subassemblies. The step of assembling the subassemblies includes the step of fabricating a composite workpiece according to the method described in the paragraph above. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred embodiments of the present end effector and methods for constructing composite members will now be discussed in detail with an emphasis on highlighting the advantageous features. These embodiments depict the novel and non-obvious end effector and methods shown in the accompanying drawings, which are for illustrative purposes only. These drawings include the following figures, in which like numerals indicate like parts: 
       FIG. 1  is a flowchart illustrating steps in an integrated aircraft production process; 
       FIG. 2  is a front perspective view of one embodiment of the present end effector and positioning apparatus for the end effector, illustrating the end effector applying course material to a workpiece; 
       FIG. 3  is a front perspective view of one embodiment of the present end effector; 
       FIG. 4  is a detail front perspective view of the end effector of  FIG. 3 ; 
       FIG. 5  is a schematic representation of relative locations and movement capabilities of the spools and rollers of one embodiment of the present end effector; 
       FIG. 6  is a schematic representation of relative locations and movement capabilities of the spools and rollers of another embodiment of the present end effector; and 
       FIG. 7  is a flowchart illustrating one embodiment of the present methods for constructing a composite member. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates an integrated aircraft production process  100 , in accordance with embodiments of the present disclosure. As used herein, the integrated aircraft production process  100  also may include manufacturing support, or both. Typically, the process  100  includes a pre-production phase S 102 , a production phase S 104 , and a post-production phase S 106 . The pre-production phase S 102  may include aircraft design S 110 , including design of subassemblies and components, and material specification and procurement S  120 . Material specification and procurement S 120  may include selection and procurement of components fabricated, or subassemblies manufactured, by third parties. Examples of such third parties include, without limitation., vendors, subcontractors, and suppliers. The production phase S 104  may include component fabrication and/or subassembly manufacturing S 130 , and aircraft assembly S 140 . The pre-production phase S 102  and production phase S 104  can be elements of an integrated manufacturing process S 105 , including one or more of aircraft and component design, development, and simulation processes; material, component, and sub-assembly specification and procurement processes; automated production planning processes; fabrication and assembly processes; and quality control processes. 
   Frequently, aspects of a modern aircraft production process, such as the integrated process  100 , do not end with final assembly, but may extend over the service life of an aircraft. These aspects may involve iterative and interactive collaborations between manufacturer, governmental authorities, customers and aircraft operators. Accordingly, the integrated production process  100  can include a post-production phase S 106 . The post-production phase S 106  may include aircraft delivery and qualification S 150 , and/or aircraft maintenance and service S 160 . The aircraft delivery and qualification S 150  may include providing an aircraft to customer specifications, which may have changed from the time the aircraft was assembled. Thus, delivery and qualification can include repair, modification, and/or revision of one or more elements of the aircraft after delivery to a customer or operator. Also, it may be desirable to perform a modification, maintenance, a repair, and/or an upgrade to an aircraft in the service interval between aircraft delivery and retirement. Therefore, aircraft maintenance and service S 160  can include repair, maintenance, modification, and/or upgrade of a portion of an airframe, including an airframe manufactured or assembled using traditional, pre-existing materials, components, and/or subassemblies. 
     FIGS. 2-4  illustrate one embodiment of the present end effector  10  for constructing a composite member  12 , and positioning apparatus  14  for the end effector  10 . With reference to  FIG. 2 , the positioning apparatus  14  is configured to position and/or control the movement of the end effector  10  with respect to a composite workpiece  16 . In the illustrated embodiment, the positioning apparatus  14  is a robotic armature or gantry-type positioning apparatus that is movable along a track  18 . The positioning apparatus  14  may be configured to provide the end effector  10  with three to ten or more degrees of freedom. However, those of ordinary skill in the art will appreciate that the positioning apparatus  14  may embody virtually any configuration, and may provide the end effector  10  with any number of degrees of freedom. In fact, in some embodiments the end effector  10  may be stationary. The configuration of the positioning apparatus  14 , and in fact the provision of positioning apparatus  14 , is not critical to the present embodiments. 
   The end effector  10  is configured to fabricate a composite member  12  by applying course material  20  to a composite workpiece  16 . The course material  20  may comprise, for example, tow, prepreg tow, slit tape, slit tape tow, tape, fibers, fiber tows, films, foils. etc. Particular examples of fibers include glass, aramid, carbon, and various other fibers. The tow may include individual fibers, bundles, cords, plaits, ribbons in the form of unidirectional “tape”, woven fabric, biaxial cloth, etc. The material may be dry or wet or preimpregnated with resin or another binding substance. The tow may also include a backing or separator film that substantially prevents the tow from adhering to itself while it is on the spool or in roll form. Those of ordinary skill in the art will appreciate that in certain embodiments the tow may not include a backing. For simplicity, the description of the present embodiments will use the term “tow” to describe the material applied to the workpiece  16 . However, as used herein, including in the claims below, the term “tow” shall be understood to be synonymous with “course material”. Those of ordinary skill in the art will appreciate that the material used is not critical to the present embodiments. 
   Depending upon the material characteristics of the tow  20 , it may be advantageous to control environmental variables such as, for example, temperature and humidity. In addition, based on manufacturer&#39;s specifications and/or empirically derived data, the storage and/or application conditions for the tow  20  may differ from one application to another. Therefore, in some embodiments the end effector  10  may include a housing (not shown) that encloses the tow  20 . The end effector  10  may also include environmental control assemblies (not shown) such as a heater and/or chiller. 
   Typically, the composite member  12  is fabricated from multiple plies or layers of tow  20 , as illustrated in  FIG. 2 . Thus, the workpiece  16  includes the workpiece surface itself and/or any previously applied layers of tow  20 . As shown in  FIGS. 3 and 4 , the end effector  10  includes a cylindrical compaction roller  22  that presses the tow  20  against the workpiece  16 . The workpiece  16  is configured to provide a suitably stable and finished surface for ply placement. Characteristics of the workpiece  16 , such as size, shape, contour, and the like, are based upon design parameters of the composite member  12  to be fabricated. 
   As shown in  FIG. 2 , the workpiece  16  may be controlled to rotate about an axis C, and in such embodiments the workpiece  16  is typically referred to as a mandrel. In other embodiments, the workpiece  16  may be stationary or controlled to move along and/or about various axes. For example, the workpiece  16  may be secured to a sliding table, or X-Y table (not shown). The movement of the workpiece  16  and/or the positioning apparatus  14  acts to position the end effector  10  with respect to the workpieece  16 . Furthermore, the movement of the workpiece  16  and the positioning apparatus  14  may be coordinated to such a degree that the devices operate much like a single unit. However, those of ordinary skill in the art will appreciate that movement of the workpiece  16  is not critical to the present embodiments. 
     FIGS. 3 and 4  provide front perspective views of one embodiment of the present end effector  10 . With reference to  FIG. 3 , in the illustrated embodiment the end effector  10  comprises a support structure  24  including a substantially flat support panel  26 . A plurality of tow supply spools  28  are arranged radially about the support panel  26 . Although twelve tow supply spools  28  are shown, those of ordinary skill in the art will appreciate that fewer or more may be provided. In the illustrated embodiment, six tow supply spools  28  are provided in an upper portion  30  of the end effector  10  and six tow supply spools  28  are provided in a lower portion  32  of the end effector  10 . For simplicity, the discussion herein will focus on the six upper tow supply spools  28 . Those of ordinary skill in the art will appreciate, however, that characteristics of the upper tow supply spools described herein may also apply to the six lower tow supply spools. 
   Each cylindrical tow supply spool  28  is mounted to a spindle  34  and includes a helically wound supply of tow  20 . As tow  20  is drawn off each spool  28  to be supplied to the work-piece  16 , the tow supply spool  28  rotates about its spindle  34 . Each spindle  34  may include a tensioner (not shown), such as a brake, that assists in maintaining a desired tension in the tow  20 . For example, a suitable tensioning device may include a belt (not shown) that wraps around a portion of the circumference of the spindle  34  and generates friction that retards the rotation of the spindle  34 . The friction may be modulated by a solenoid or a servo acting upon the belt. Advantageously, the spindles  34  do not require bi-directional movement or complicated rewind apparatus in order to maintain tension, as explained in detail below. 
   With reference to  FIG. 3 , in the illustrated embodiment the end effector  10  further comprises a plurality of backing take-up spools  36 , a plurality of dancer rollers  38  and a plurality of redirect rollers  40 . Each of the backing take-up spools  36 , dancer rollers  38  and redirect rollers  40  spins freely on an axle or spindle (not shown). One backing take-up spool  36 , one dancer roller  38  and one redirect roller  40  is provided for each tow supply spool  28 . However, in  FIGS. 3 and 4  the lower redirect rollers  40  and associated support structures have been omitted for clarity. The backing take-up spools  36  and dancer rollers  38  are located closely adjacent their respective tow supply spools  28  and the redirect rollers  40  are located in a cluster near a center of the support panel  26 . Each length of tow  20  follows a set path about the spools and rollers as follows. Each path of tow travel begins as the tow  20  leaves its respective supply spool  28 , continues around its respective backing take-up spool  36 . then around its respective dancer roller  38  and then to its respective redirect roller  40 . 
   As each tow  20  travels around its respective backing take-up spool  36  the backing (not shown) separates from the tow  20  and winds onto the take-up spool  36 . As explained above, in certain embodiments the tow  20  may not include a backing. In such embodiments the backing take-up spools  36  may not be present, or they may be present but unused. Those of ordinary skill in the art will appreciate that alternative apparatus may be provided for separating the tow  20  from its backing. For example, one such apparatus includes a vacuum nozzle (not shown) in fluid communication with a vacuum source and configured to generate sufficient suction to draw off the tow backing. Such apparatus is disclosed in U.S. Patent Application Publication No. 2006/0180264 entitled “Modular Head Lamination Device and Method”, the entire contents of which are hereby incorporated by reference. 
   After the tow  20  and backing are separated, the tow  20  continues around its respective dancer roller  38 . The dancer roller  38  advantageously dampens any rapid changes in the feed rate of the tow  20 . The dancer roller  38  also facilitates a smooth removal of the tow  20  from the spool  28 , and directs the path of tow travel toward its respective redirect roller  40 . The tow  20  travels around its respective redirect roller  40  and toward the compaction roller  22 . The path of tow travel from the redirect rollers  40  to the compaction roller  22  extends along an axis X′, known as a compaction axis or compliance axis ( FIGS. 4 and 5 ). Along this axis the tow  20  may be directed past one or more optional components such as, for example, combs, cutting assemblies, clamps, dancers, idlers, etc. 
   With reference to  FIGS. 3 and 4 , the configuration of the end effector  10 , with the tow supply spools  28  arranged radially around the redirect rollers  40 , feeds each tow  20  to its respective redirect roller  40  at substantially a right angle to the compaction axis X′. Thus, one step in one embodiment of the present methods comprises feeding the tow  20  to the redirect roller(s)  40  at substantially a right angle to the compaction axis X′, as illustrated in step S 700  of  FIG. 7 . The right angle feed, which is illustrated schematically in  FIG. 5 , advantageously contributes to a substantially constant tension in each tow  20 , as described in detail below. The redirect roller(s)  40  redirect the tow  20  toward the compaction roller  22 , as illustrated in step S 702  of  FIG. 7 . 
   As tow  20  is dispensed from the end effector  10  and applied to the workpiece  16 , as illustrated in step S 704  of  FIG. 7 , the compaction roller  22  presses the tow  20  against the workpiece  16 , as illustrated in step S 706 . From time to time the workpiece  16  and the end effector  10  may become misaligned and/or the surface of the work-piece  16  may become uneven, such as through unanticipated tow buildup. In order to accommodate these misalignments and uneven surfaces, the compaction roller  22  is configured to be translatable along the compaction axis X′ ( FIG. 4 ) relative to the end effector  10 . For example, the compaction roller  22  may be translatable plus or minus 1 to 20 mm along the compaction axis X′, as indicated by the double-headed arrow in  FIG. 5 . Thus, as the compaction roller  22  travels over the surface of the workpiece  16  it may translate back and forth along the compaction axis X′ in response to misalignments and uneven surfaces. To accommodate this translation, the compaction roller  22  is mounted on a compaction roller subassembly  42  ( FIGS. 3-5 ) that is slidably secured to a pair of brackets  44  that are in turn secured to the support structure  24 . Only one of the brackets  44  is visible in  FIGS. 3 and 4 , and for clarity the structure that secures the brackets  44  to the support structure  24  has been omitted. The brackets  44  may be stationary with respect to the support structure  24 , or they may be capable of relative movement. The compaction roller subassembly  42  is urged toward the workpiece  16  by, for example, one or more pneumatic cylinders (not shown). Those of ordinary skill in the art will appreciate that alternative apparatus may be used to urge the compaction roller subassembly  42  toward the work-piece  16 . 
   As illustrated in  FIG. 4 , in the present embodiments the redirect rollers  40  are advantageously mounted to the compaction roller subassembly  42 . This configuration is also shown schematically in  FIG. 5 . In  FIG. 5  only one redirect roller  40  is shown, and represents the multiple redirect rollers shown in  FIG. 4 . As shown, the redirect rollers  40  are mounted at an upstream end of the compaction roller subassembly  42  and the compaction roller  22  is mounted at a downstream end of the subassembly  42 . Because the redirect rollers  40  and the compaction roller  22  are both mounted to the compaction roller subassembly  42 , they are constrained from moving relative to one another. They translate as a unit in both directions along the compaction axis X′, as illustrated by the double-headed arrow in  FIG. 5 . Thus, as the compaction roller  22  travels over the surface of the workpiece  16  and translates back and forth along the compaction axis X′ as described above, the redirect rollers  40  translate along the compaction axis X′ in sync with the compaction roller  22 , as illustrated in step S 708  of  FIG. 7 . This simultaneous movement of the compaction roller  22  and the redirect rollers  40 , coupled with the substantially ninety-degree feed angle of the tow  20  to the redirect rollers  40 , advantageously maintains a nearly constant tension within the tow  20 . 
   In prior art apparatus for constructing composite members, movement of the compaction roller along the compaction axis disadvantageously lowers tension in each tow. The present embodiments reduce or eliminate such tension losses by feeding the tow  20  to the redirect rollers  40  at a substantially ninety-degree feed angle to the compaction axis, coupled with synchronous movement of the compaction roller  22  and the redirect rollers  40  along the compaction axis X′. As the compaction roller  22  moves relative to the end effector  10 , the redirect rollers  40  move along with it. Thus, tension in the region of the tow path between the redirect rollers  40  and the compaction roller  22  remains substantially constant. And because the tow  20  is fed to the redirect rollers  40  at a substantially ninety-degree angle to the compaction axis, movement of the redirect rollers  40  with respect to the tow supply spools  28  does not generate any significant variations in tension in the region of the tow path between the tow supply spools  28  and the redirect rollers  40 . The reduction or elimination of these variations in tow tension enable the present embodiments to produce high-quality composite members  12  without the need for complex and expensive bi-directional tow supply spools and rewind apparatus. The overall cost and complexity of the end effector  10  are thus reduced. 
   Those of ordinary skill in the art will appreciate that the present embodiments are susceptible to many variations that are nevertheless within the scope of the claims below. For example, additional rollers may be added to the end effector  10  to suit particular applications.  FIG. 6  illustrates, schematically, one such alternative embodiment including a second redirect roller  46 . While only one second redirect roller  46  is shown in  FIG. 6 , those of ordinary skill in the art will appreciate that a plurality of second redirect rollers  46  may be provided. The second redirect roller  46  is located between the tow supply spool  28  and the first redirect roller  40 . Tow  20  is fed from the tow supply spool  28  around the second redirect roller  46  to the first redirect roller  40 . Advantageously, the configuration of  FIG. 6  maintains the substantially ninety-degree tow feed angle to the first redirect roller  40  and the synchronous movement of the first redirect roller  40  with the compaction roller  22 . 
   The above description presents the best mode contemplated for carrying out the present end effector for constructing composite members, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains to make and use this end effector. This end effector is, however, susceptible to modifications and alternate constructions from that discussed above that are fully equivalent. Consequently, this end effector is not limited to the particular embodiments disclosed. On the contrary, this end effector covers all modifications and alternate constructions coming within the spirit and scope of the end effector as generally expressed by the following claims, which particularly point out and distinctly claim the subject matter of the end effector.