Patent Publication Number: US-9884472-B2

Title: Reduced complexity automatic fiber placement apparatus and method

Description:
This application is a divisional of application Ser. No. 12/038,155 filed Feb. 27, 2008, status allowed. 
    
    
     TECHNICAL FIELD 
     This disclosure generally relates to automated fiber placement systems, especially those used to layup composite structures, and deals more particularly with a simplified apparatus for the placing fibers as well as a related method. 
     BACKGROUND 
     Composite structures such as those used in the automotive, marine and aerospace industries may be fabricated using automated composite material application machines, commonly referred to as automated fiber placement (AFP) machines. AFP machines may be used in the aircraft industry, for example to fabricate structural shapes and skin assemblies by wrapping relatively narrow strips of composite, slit tape or “tows”, collimated into a wider band, around a manufacturing tool. The AFP machine aligns and places a plurality of tape strips, typically six or more, in continuous, edge to edge contact forming a single wide, conformal bandwidth which is placed on and compacted against the tool. 
     In order to fabricate large, complex laminated composite assemblies, current AFP machines may use fiber placement heads having a relatively high degree of operational flexibility. For example, current placement heads may have the ability to add drop-off or cut any or all of the contiguous tape strips independently of all others by providing separate, independently controllable cutters for each tape strip. Current placement heads therefore may be relatively complex, large and heavy. 
     The size, weight and complexity of current placement heads may preclude their use in fabricating relatively small composite laminate assemblies, or in fabricating layups that require relatively high placement resolution. Moreover, because of their complexity, current placement heads are relatively expensive. 
     Accordingly, there is a need for automatic fiber placement apparatus that has reduced mechanical complexity and is both smaller in size and lighter in weight for those fiber applications requiring higher placement resolution and/or simplified tape application. Further, there is a need for a method of fiber placement using less complex placement machines that allows fiber placement forming ramped or contoured tape patterns. 
     SUMMARY 
     Automatic fiber placement apparatus and related methods are provided which are particularly useful in fabricating relatively small, laminated composite fiber structures, and as well as larger composite structures requiring a high degree tape placement resolution. The complexity, size and weight of the placement head is reduced by employing a single cutting mechanism to simultaneously cut the ends of all of the tape strips at the end of a course, thus eliminating the need for separate cutting mechanisms for each tape strip. In spite of this reduced mechanical complexity, contoured or ramped tape application patterns may be achieved by sequentially starting the placement of each tape strip as a band of strips are laid down. 
     According to one disclosed embodiment, a method is provided for forming a composite layup on a substrate, comprising: moving an automatic fiber placement head over the substrate; using the fiber placement head to lay down multiple, parallel strips of composite tape on the substrate, including staggering the start of at least certain of the tape strips so as to form a contour pattern; and, cutting the ends of all of the tape strips using a single cut. Cutting the ends of the tape strips may be performed by passing a single cutting blade through all the tape strip substantially simultaneously. 
     According to another method embodiment, placing composite fiber tape on a substrate using an automatic fiber placement head comprises: moving the fiber placement head across the substrate from a starting position to an ending position; sequentially starting the placement of individual fiber tape strips onto the substrate to form a band as the placement moves from the starting position to the ending position; and, cutting all of the tape strips in the band substantially simultaneously at the ending position. Sequentially starting the placement of the individual fiber tape strips may be performed by sequentially activating individual tape threading mechanisms on the fiber placement head. Cutting all the tape strips may be performed by activating a single cutting blade mechanism on the fiber placement head and using the single cutting blade mechanism to cut all the tape strips. 
     According to a further method embodiment, a composite fiber layup is formed on a substrate having a substrate feature, comprising: moving an automatic tape placement head across the substrate away from the substrate feature in a first direction; using the placement head to lay down a first band of composite tape strips as the placement head moves across the substrate in the first direction, including staggering the starting points of at least certain of the tape strips in the first group to form a ramp pattern on one side of the substrate feature; cutting all of the tape strips in the first band at an ending point of the tape strips in the first band; moving the automatic tape placement head across the substrate away from the substrate feature in a second direction; using the placement head to lay down a second band of composite tape strips as the placement head moves across the substrate in the second direction, including staggering the starting points of at least certain of the tape strips in the second band to form a second ramp pattern on another side of the substrate feature; and, cutting all of the tape strips in the second band at an ending point of the tape strips in the second band. Cutting the tape strips in the first and second bands is performed by passing a single cutting blade through all the tape strips in the group substantially simultaneously. Laying down the tape strips in each of the first and second bands may be performed during a single pass of the placement head. Movement of the placement head in each of the first and second directions is commenced from a centerline passing substantially through the substrate feature. Laying down the composite tape strips may be performed by sequentially activating individual tape threading mechanisms on the fiber placement head. 
     According to another disclosed embodiment, a fiber tape placement apparatus is provided for placing fiber tape on a substrate, comprising: a plurality of tape supply devices each holding a supply of fiber tape; a device for compacting the tape on the substrate; a plurality of threading mechanisms respectively associated with the tape supply devices and each operable for initiating tape feed from one of the tape supply devices to the compaction device; and, a cutting device including a single cutting blade for cutting the ends of all the tapes fed to the compaction device substantially simultaneously. The cutting blade includes a cutting edge extending transversely across the paths along which the tapes are fed to the compaction device. The cutting device may include an actuator for displacing the cutting blade toward and away from the tapes. The tapes may be arranged in side-by-side relationship as the tapes are fed to the compaction device, and the cutting blade may be positioned to cut the ends of the tapes while the tapes are in side-by-side relationship. 
     The disclosed embodiments satisfy a need for an automatic fiber placement apparatus having reduced complexity, and a related method that allows layups to be formed having contoured patterns. 
     Other features, benefits and advantages of the disclosed embodiments will become apparent from the following description of embodiments, when viewed in accordance with the attached drawings and appended claims 
    
    
     
       BRIEF DESCRIPTION OF THE ILLUSTRATIONS 
         FIG. 1  is a perspective view of a single part fabrication cell having a reduced complexity fiber placement machine. 
         FIG. 2  is a perspective view of a large scale fiber placement cell having a reduced complexity fiber placement machine. 
         FIG. 3  is a block diagram illustrating the basic components of the reduced complexity fiber placement machine. 
         FIG. 4  is a side view of the reduced complexity fiber placement machine. 
         FIG. 5  is a top view of the machine shown in  FIG. 4 . 
         FIG. 6  is a bottom view of the machine shown in  FIG. 4 . 
         FIG. 7  is an exploded, perspective view of a rethread assembly forming part of the machine shown in  FIGS. 4-6 . 
         FIG. 8  is a perspective view of the rethread assembly. 
         FIG. 9  is a perspective view of the machine shown in  FIGS. 4-6 , a cover having been removed to show additional details. 
         FIG. 10  is a simplified front elevational view of the tape cutting mechanism forming part of the machine shown in  FIGS. 4-9 . 
         FIG. 11  is a perspective view of a tool on which a band of tapes has been placed using the reduced complexity tape placement machine. 
         FIG. 12  is a plan view of one tape band illustrating the sequential, timed starting points of individual tape strips ending at a common cutting point. 
         FIG. 13  is a flow diagram illustrating the basic steps of one method for placing composite tape on a substrate using the reduced complexity automatic fiber placement machine. 
         FIG. 14  is a diagrammatic, plan view showing an alternate method for placing contiguous strips of tape on a substrate. 
         FIG. 15  is a flow diagram illustrating in more detail the alternate method for placing tape on a substrate shown in  FIG. 14 . 
         FIG. 16  is a plan view showing two bands of tape strips placed around a substrate feature. 
         FIG. 17  is a flow diagram illustrating a method for placing tape strips around the substrate feature shown in  FIG. 16 . 
         FIG. 18  is a flow diagram of aircraft production and service methodology. 
         FIG. 19  is a block diagram of an aircraft. 
     
    
    
     DETAILED DESCRIPTION 
     Referring first to  FIG. 1 , a single part fabrication cell generally indicated by the numeral  18  employs a reduced complexity composite fiber placement (AFP) machine  20  that may be used to layup relatively small, individual parts  26  over a tool  28 . The AFP machine  20  may be partially or fully automatically controlled by a suitable controller (not shown) which may comprise a NC, CNC or PLC controller. The AFP machine  20  may also be at least partially controlled by an operator  24 . 
     In the illustrated example, the AFP machine  20  is mounted for movement along orthogonal x,y,z axes shown at  25 . More particularly, a tape application head  40  is mounted on a guide  30  for sliding movement along the Z axis, and the guide  30 , in turn, is mounted on a gantry  32  for sliding movement along the x axis. The gantry  32  is mounted for sliding movement along the z axis by means of rails  34  that are supported on a table  22 . The AFP machine includes tape supply reels  38  which supply composite fiber tape  36  to the application head  40  which includes a compaction roller  42  for compacting the tape  36  against the tool  28 . As used herein, “composite fiber tape”, “fiber tape”, “tape” and “tape strips” are intended to include a wide range of tapes, “tows” and rovings, including those having standard widths such as, without limitation, three inches or six inches, and those having nonstandard widths such as one-eighth inch or one-quarter inch (“tows”). 
     As will be described later in more detail, the tape  36  is drawn from the reels  38  by a later discussed tape threading mechanism which feeds tape to a nip (not shown) between the compaction roller  42  and the surface of the tool  28 . Movement of the AFP machine  20  draws tape  36  from the reels  38 , and the tape  36  is cut to length by a later discussed, simplified tape cutting mechanism. 
     Referring now to  FIG. 2 , an alternate form of the AFP machine  20   a  may be used as an end effector installed on a robot  44  which is mounted for translation along rails  46 . A tool, such as a cylindrical mandrel  50  is mounted by spindles  42  for rotation on supports  54 . Rotation of the tool  50 , as well as the operation of the robot  44  and the placement head  20   a  may be controlled by a NC or CNC controller  48 . The placement head  20   a  may be used to layup bands  28  of the tape  36  on the mandrel  50  with high contour resolution. 
     Referring now to  FIG. 3 , the AFP machine  20  broadly includes a simplified tape supply system  56 , tape alignment and independent rethread modules  58 , and a single tape cutting mechanism  70  which is used to cut all of the tapes  36 . The simplified material supply system  56  may comprise a number of individual tape supply modules  57  that are respectively associated with and draw tape  36  from the pre-wound tape reels  38  ( FIG. 1 ). 
     Each of the tape supply modules  57  may include a simple tension drag brake (not shown) and an inertia limiting device such as a pneumatically operated disc brake (not shown), which together act to supply the tape  36  to the respectively associated tape alignment and rethread module  58 , in a uniform, aligned manner. The tape alignment and rethread modules  58  align the plurality of individual tapes  36  in parallel, edge-to-edge contact using a combination of slotted guides (not shown) which may be preset in a weave pattern to provide mechanism clearance. Packaged within each alignment and rethread module  58  is a tape rethread mechanism  90  ( FIG. 6 ). Although not specifically shown in the Figures, the tape rethread mechanism  90  uses frictional contact to drive and clamp the individual tapes  36 . Additional details of the tape supply modules  57 , the alignment and rethread modules  58  and the rethread mechanisms  90  may be found in U.S. Pat. No. 4,699,683, issued Oct. 13, 1987 and US Patent Publication No. 20070029030A1 published Feb. 8, 2007, the entire contents of both of which are incorporated by reference herein. 
     Referring now to  FIGS. 4-9 , the tape placement head  40  includes a frame assembly  41  having a top plate  62  adapted to be connected to a robot  44  ( FIG. 2 ) or other tool used for moving the placement head  40  across a substrate on which tape  36  is to be placed. The tape alignment and rethread modules  58  are mounted side-by-side on a central body  91  ( FIG. 7 ) held within the frame assembly  41 . Each of the modules  58  includes a mating set of flat rollers  72  and U-shaped rollers  74  that form an entrance channel  76  for one of the tapes  36 . The flat rollers  72  are mounted on a shaft  60  that is carried on a pivoting arm  66 . Springs  84  bias the pivoting arms  66  toward a normal closed position in which the flat rollers are spaced a preselected distance from the U-shaped rollers  74 , generally corresponding to the thickness of the tape  36 . The height or thickness of the entrance channel.  76  may be adjusted through a set screw  68 . The tapes  36  supplied from reels  38  ( FIG. 1 ) are respectively received into the entrance channels  76  and are maintained in side-by-side, registered relationship by slotted guides  80  ( FIG. 7 ) which are enclosed by a cover plate  93 . 
     Tapes  36  are fed though the slotted guides  80  to rethread mechanisms  90  which include tape engaging rollers  90   a  which are moved into engagement with the tapes  36  by pneumatic cylinders  86 . The rollers  90   a  are driven by a belt  97  powered by a motor  99 . Actuation of a particular rethread mechanism  90  initiates threading of the corresponding tape  36  which is then fed through one of the slotted guides  80  to a guide member  83  which then directs the tape  36  at a predetermined angle into the nip  74  where the tape  36  is applied and compacted on the substrate  28  by the compaction roller  42 . Fiber optic sensors  89  ( FIG. 9 ) sense the position of the tapes  36 , including passage of the ends of the tapes  36 , and produce position signals that may be used to control tape feed and placement. The fiber optic sensors  89  also may be used to sense the operation of the blade  92 , either to allow synchronization of its operation with other functions in the AFP machine  20 , or simply to verify that the blade  92  is operating properly, or both. 
     From the foregoing, it may be appreciated that the location on the substrate surface  82  ( FIG. 4 ) at which a particular tape  36  “starts” is dependent on the point in time when which the tape threading mechanism  90  is actuated to begin feeding tape  36  to the compaction roller  42 . Since the tape threading mechanisms  90  can be independently actuated by actuators  86 , the starting point of each tape  36  can be independently controlled so that these starting points may be staggered in any desired pattern, as will be described in more detail below. 
     As best seen in  FIG. 9 , in accordance with the disclosed embodiment, the tape placement head  40  further includes a tape cutting mechanism  70  comprising a pneumatic actuator  96  that reciprocates a single cutting blade  92 . The pneumatic actuator  96  receives air from an air manifold which is controlled by an electric valve control cylinder  87 . The cutting mechanism is also diagrammatically illustrated in  FIG. 10 . The single cutting blade  92  is connected to the pneumatic actuator  96  through a suitable drive linkage  98 . The blade  92  includes a cutting edge  92   a  that spans the entire band  106  of tapes laid down by the placement head  40 . Blade  92  reciprocates, as indicated by the arrow  100  in  FIG. 10 , so as to simultaneously sever the entire band  106  of tapes  36  in a single shear cut. As will be apparent from the description below, the ends of the tapes  36  are cut at the same point during the tape laydown process, regardless of the starting point of the tapes  36 . 
     As used herein, reference to cutting all of the tapes  36  in a band  106  “simultaneously” or “substantially simultaneously” means that the blade  92  or other cutting device severs all of the tapes  36  in the band  106  at substantially the same point at the end of a course. Thus, a cutter (not shown) could be drawn transversely across the band  106  in a single stroke to sequentially cut the tapes in a band  106  at the end of the course, instead of contacting and severing all of the tapes  36  in the band  106  at exactly the same time, as shown in the illustrated embodiment. Further, reference to cutting the tapes  36  in a band  106  in a “single cut” or “single blade stroke” likewise means that all of the tapes  36  in a band  106  are cut at substantially the same point at the end of a course through the motion of a single cutter which contacts and severs the tapes at this ending point either simultaneously or in rapid succession. 
     Reference is now made to  FIGS. 11-13  which illustrate one method embodiment for forming layups using the reduced complexity AFP machine  20 . In the example illustrated in  FIG. 11 , a contoured band  106  of parallel, contiguous tape strips  36  are laid up on a tool  102  supported on a base  104 . The tool  102  includes a contoured edge  108  to which a contoured portion  88  of the band  106  may substantially conform. As shown at step  114  in  FIG. 13 , the placement head  40  is first moved to a starting position which corresponds to the starting point “A” of tape number  1  in the band  106 . As shown at step  116  in  FIG. 13 , and in  FIG. 11 , the placement head  40  is translated in the direction of travel  112  from the starting position “A” to an ending position “G”. At step  118 , as the placement head  40  moves from the starting position “A” to the ending position “G”, the individual tape threading mechanisms  90  are actuated to start the placement of tapes  1 - 6  in a sequential manner so that they are respectively added at points A-F. 
     The sequential starting of tapes  1 - 6  described above staggers the beginnings of tapes  36  so that they form the edge contour or outer profile  88  ( FIG. 11 ) which generally matches the contoured edge  108  of the tool  102 . The sequential addition of the tapes  36  to the band  107  continues until the band  106  becomes uniform at point “F”. At a preselected point, as shown at step  120 , the cutting mechanism  70  is actuated so as to cut the entire band  106  at the ending or cut point “G”, in a single shear cut by the blade  92 . It may be appreciated that the resolution of the outer profile  88  may be determined by the number of tapes  36  present under the cutting mechanism  70  at the time the single cut is initiated. Hence, for higher resolution areas, a fewer number of tapes  36  may be included within the width of the band  106  for a particular course. 
     Attention is now directed to  FIGS. 14 and 15  which illustrate an alternate method embodiment for placing tape  36  using the reduced complexity AFP machine  20 . Beginning at step  124 , the placement head  40  is moved to a starting position  121 , in preparation for the placement of tape number  1 . As shown in steps  126  and  128 , as the placement head  40  is translated in the direction of travel  112 , a single tape threading mechanism  90  is activated, thereby causing tape number  1  to be placed on the tool substrate  82 . As shown at step  130 , tape number  1  is cut at the end of the course or cut point indicated by the numeral  122 . 
     Next, the placement head  40  is translated through a return path  123  to a starting position for tape number  2 , as shown at step  132 . At steps  134  and  136 , the placement head  40  is again translated in the direction of arrow  112 , while one of the tape threading mechanisms  90  is activated to begin laying tape number  2  parallel with and contiguous to tape number  1 . Tape number  2  is severed by the cutting mechanism  90  at the cut point  122 . Next, at step  140 , the process of translating the placement head  40  through a return path to the next tape starting position  129  is repeated for each of the subsequent individual course of tape  36 . 
     In the illustrated example, the tape head  40  is translated from the starting point  129  to the cut point  122  during which one of the tape threading mechanisms  90  is activated to lay down tape number  3 , which is then cut by the cutting mechanism  70  at the cut point  122 . As previously noted, the resolution of the cutting pattern or ramped profile  88  is determined by the number of tapes  36  that are present under the cutter  70  at the time the tapes  36  are cut. Thus, using the method illustrated in  FIGS. 14 and 15 , a fewer number of tapes  36  may be included within the total course band  106  in order to achieve higher profile resolution. While only a single tape  36  is placed and cut in the illustrated example during each pass of the tape placement head  40 , two or more tapes  36  may be simultaneously placed and cut to produce the desired resolution, depending upon the application. 
     Attention is now directed to  FIGS. 16 and 17  which illustrate a further method embodiment in which the reduced complexity AFP machine  20  is used to layup tape  36  around a substrate feature, which in the illustrated example, comprise future througholes to be formed in a substrate  145 . Beginning at step  150 , the placement head is moved to a starting position corresponding to the centerline  142  of the substrate features  148 . Next at  152 , the placement head  40  is translated in one direction of travel  112  from the centerline  142  to and ending position  144 . During translation of the placement head  40 , the tape threading mechanisms  90  are actuated, as shown at  154 , thereby laying down a first band of tapes  147  wherein the starting points of the individual tapes  36  form a ramped pattern which are stepped around the substrate features  148 . All of the tapes  36  in the first band  147  are simultaneously cut at  144 , as shown at step  156  in  FIGS. 16 and 17 . 
     Next, the placement head  40  is moved back to the centerline position  142 , as shown at step  158 , in preparation for placing a second course  149 . As shown at step  160 , the head  40  is translated from the centerline  142  to an ending position  146 , during which the tape threading mechanisms  90  are actuated in a predetermined time sequence so that the starting positions of the individual tapes  36  in the second band  149  form a ramp pattern that is stepped around the substrate features  148 . At step  164 , all of the tape strips  36  in the second band  149  are severed simultaneously at the end or cutting point  146 . 
     Embodiments of the disclosure may find use in a variety of potential applications, particularly in the transportation industry, including for example, aerospace, marine and automotive applications. Thus, referring now to  FIGS. 18 and 19 , embodiments of the disclosure may be used in the context of an aircraft manufacturing and service method  166  as shown in  FIG. 18  and an aircraft  167  as shown in  FIG. 19 . Aircraft applications of the disclosed embodiments may include, for example, without limitation, composite stiffened members such as fuselage skins, wing skins, control surfaces, hatches, floor panels, door panels, access panels and empennages, to name a few. During pre-production, exemplary method  166  may include specification and design  168  of the aircraft  167  and material procurement  170 . During production, component and subassembly manufacturing  172  and system integration  174  of the aircraft  167  takes place. Thereafter, the aircraft  167  may go through certification and delivery  176  in order to be placed in service  178 . While in service by a customer, the aircraft  167  is scheduled for routine maintenance and service  180  (which may also include modification, reconfiguration, refurbishment, and so on). 
     Each of the processes of method  90  may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of vendors, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on. 
     As shown in  FIG. 19 , the aircraft  167  produced by exemplary method  166  may include an airframe  182  with a plurality of systems  184  and an interior  186 . Examples of high-level systems  184  include one or more of a propulsion system  188 , an electrical system  190 , a hydraulic system  192 , and an environmental system  194 . Any number of other systems may be included. Although an aerospace example is shown, the principles of the disclosure may be applied to other industries, such as the marine and automotive industries. 
     Systems and methods embodied herein may be employed during any one or more of the stages of the production and service method  166 . For example, components or subassemblies corresponding to production process  166  may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft  167  is in service. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the production stages  172  and  174 , for example, by substantially expediting assembly of or reducing the cost of an aircraft  167 . Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft  167  is in service, for example and without limitation, to maintenance and service  180 . 
     Although the embodiments of this disclosure have been described with respect to certain exemplary embodiments, it is to be understood that the specific embodiments are for purposes of illustration and not limitation, as other variations will occur to those of skill in the art.