Short course fiber placement head

A composite automation method and apparatus for the generation of short path course application of a composite lamina is realized by reconfiguring the functional mechanisms of the fiber placement head. Separating the fiber advance and retract functions, nesting the activation cylinders, and making use of push only activation results in a simplified, compact AFP delivery head. Uniform cutting is provided by a circular configuration fiber cutting blade, were at activation the blade both provides a progressive cutting force and rotates to providing a new cutting edge, and requires limited cutting edge guidance as all orientations cut equally well. The mechanism nested in functions and placed in close proximity to the compaction roller reduces the overall fiber course to the application point.

BACKGROUND

This application generally relates to automated methods and equipment for laying up plies of composite material, and deals more particularly with a method and apparatus for placing short courses of composite tape on a substrate during the layup process.

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 components and skins by placing relatively narrow strips of composite, slit fiber tape or “tows” on a manufacturing tool. The tape may be placed on the tool in parallel courses that may be in substantially edge-to-edge contact to form a ply.

Known AFP machines employ a tape placement head that dispenses, cuts and compacts courses of tape onto the tool surface as a tape placement head is moved by a robotic device over the tool surface. These tape placement heads typically include a supply spool of tape, and a dispensing mechanism that draws the tape from the spool and guides the tape into a nip between a compaction roller and the tool surface. A cutter blade within the dispensing mechanism located upstream from the compaction roller cuts the tape to a desired course length. The minimum length of a tape course that can be placed by the tape placement head may therefore be governed by the distance between the point where the tape is compacted onto the tool surface and the point where the tape is cut by the blade.

In some applications, relatively short courses may be required which have a length less than the minimum course length that can be cut by known tape heads. In other words, a desired course length may be less than the distance from the compaction point to the point where the cut is made. Under these circumstances, it may be necessary to place courses that are longer than optimum course lengths, thereby adding weight and/or cost to the part, or prompting the need to trim the plies of excess tape, or to manually lay the short courses by hand, thereby adding undesired labor and expense to the manufacturing process.

SUMMARY

Accordingly, there is a need for a tape placement head and method for cutting courses of tape which allow placement of courses of shorter length.

The present application discloses various systems and methods to address the aforementioned challenges with existing tape heads.

In one example, an automated fiber placement (AFP) machine is disclosed for placing composite material on a substrate. The AFP machine comprises a first low-profile tow control module comprising one or more circular cutter blades, and a second low-profile tow control module comprising one or more circular cutter blades. The AFP machine further comprises a vee block coupled to the first and second low-profile tow control modules and located between the first and second low-profile tow control modules, the vee block comprising a plurality of air passages located therein. The AFP machine further comprises a plurality of air cylinders coupled to the vee block and nested between the first low-profile tow control module and the second low-profile tow control module, the plurality of air cylinders being aligned with the air passages located within the vee block.

The first and second low-profile tow control modules may have a height no greater than about ¾ inch. The circular cutter blades may have a height no greater than about ¾ inch. The AFP machine may further comprise a compaction roller having a diameter no greater than about ¾ inch. The circular cutter blades may be removably coupled to a cutter rocker arm configured to be rotated about an axle by a first, cutter extend piston and second, cutter retract piston. The substrate may comprise a flat or nearly-flat charge. The AFP machine may further comprise a control unit configured to access a file that includes computer readable instructions for fabricating a composite item. The AFP machine may further comprise one or more positioning devices configured to maneuver the substrate relative to a delivery head while the composite material is placed on the substrate. The positioning device(s) may comprise one or more NC machines, robotic arms, or mandrels.

In another example, a delivery head of an automated fiber placement (AFP) machine comprises a vee block having a plurality of air passages located therein, and a first tow control module coupled to the vee block. The first tow control module comprises a tow guide tray, a support frame, a cutter rocker arm with an attached cutter blade, and a pinch/feed rocker with an attached pinch roller. The cutter rocker arm is coupled to the support frame by a cutter rocker axle. The pinch/feed rocker is nested within the cutter rocker arm and is coupled to the support frame by a pinch/feed rocker axle. A plurality of pistons are positioned in cavities located within the vee block and coupled to the air passages, the pistons being aligned with the cutter rocker arm and the pinch/feed rocker.

The attached cutter blade may comprise a circular cutter blade. The pistons may comprise a first, cutter extend piston and second, cutter retract piston, which are configured to rotate the cutter rocker arm about the cutter rocker axle. The tow guide tray may define a plurality of tow guide paths, and the first tow control module may comprise a corresponding plurality of cutter rocker arms and pinch/feed rockers. The delivery head may be configured to place composite material on a flat or nearly-flat charge. The delivery head may further comprise a second tow control module coupled to the vee block, the second tow control module comprising substantially identical components as the first tow control module, located in complementary positions.

In another example, a method of placing a course of composite material on a substrate is disclosed using an AFP machine with a low-profile delivery head and a circular cutter blade. The method comprises feeding one or more tows of composite material through the delivery head by extending a feed piston to bring a pinch roller into contact with a feed roller, thereby causing the tow(s) of composite material to be pulled between the pinch roller and the feed roller along a tow guide channel. The method further comprises cutting the tow(s) of composite material to a desired length by extending a cutter extend piston and retracting a cutter retract piston, thereby causing a cutter rocker arm to rotate about an axis and lower the circular cutter blade through the tow guide channel. The method further comprises retracting the circular cutter blade by extending a cutter retract piston and retracting a cutter extend piston, thereby causing a cutter rocker arm to rotate about an axis and raise the circular cutter blade out of the tow guide channel.

The method may further comprise rotating the circular cutter blade to provide a new cutting edge. The method may further comprise clamping the tow(s) of composite material in place in the tow guide channel by extending a clamp piston at substantially the same time as the circular cutting blade is lowered. Extending the pistons may comprise supplying air pressure to the pistons through passages formed within a vee block. The substrate may comprise a flat or nearly-flat charge.

DETAILED DESCRIPTION

The present application discloses a system for placing composite lamina plies to fabricate a composite item and a method of using this system. Specifically, the system provides for the short path course application of a composite lamina by reconfiguring the functional mechanisms of a fiber placement head. In some examples, the system includes an automated lamination device such as, for example, an automated fiber placement (AFP) machine. This lamination device includes one or more dispensing heads to place plies of composite material upon a mandrel, layup mold or tool. In addition, the lamination device includes a cutting device to cut the composite material. Additional details and variations regarding the configuration and operation of the system will be apparent to those of ordinary skill in the art, having the benefit of this disclosure.

FIG. 1is a block diagram of one example of an automated fiber placement (AFP) machine100in accordance with the present application. In the example shown inFIG. 1, the AFP machine100includes a placement head105that is positioned by a corresponding positioning device110. The placement head105is configured to place115composite material upon a substrate120. The substrate120includes the surface of a workpiece125, such as, for example, a mandrel, tool, layup model, or any other suitable surface on which composite material is placed. In addition, the substrate120may include any previously applied composite material, tackifier, and the like that is previously laid down on the workpiece125. The workpiece125is rotated or otherwise positioned by a drive apparatus130. The drive apparatus130and/or the positioning device110are controlled by a control unit135. The control unit135accesses a file140that includes computer readable instructions for fabricating a composite item.

FIG. 2Ais a schematic diagram illustrating one example of an automated fiber placement (AFP) machine200in accordance with the present application. In general, the AFP machine200is configured to maneuver a substrate210, such as a tool or a flat charge layup mold, relative to a fiber placement head assembly, or delivery head215, while tows of composite material are placed on the substrate210. For instance, in the specific example illustrated inFIG. 2A, the AFP machine200comprises a numerical control (NC) machine205, such as a robotic arm, which is configured to manipulate the substrate210while the delivery head215remains stationary. In other cases, the AFP machine200may comprise an NC machine205that is configured to move the delivery head215while the substrate210either remains fixed or moves in one or more additional axes of motion. Beyond these examples, other alternative mechanisms may be utilized for moving the substrate210relative to the delivery head215, as will be appreciated by those of ordinary skill in the art.

The delivery head215is shown in greater detail inFIG. 2B. The AFP machine200further comprises a tow supply system220including a set of storage spools225, or creels, as well as a series of tow guides, e.g., redirect rollers230and redirect pulleys235, as well as a tension brake system250. For simplicity, the complete roller support framework for the AFP machine200is not shown in its entirety inFIGS. 2A and 2B. The AFP machine200may also comprise various standard control components, such as pneumatic cylinders, electro-servo actuators, control wires, hoses, etc. (not shown) that control the operation of the AFP machine200under the direction of a suitable control module, such as the control unit135shown inFIG. 1.

In operation, the AFP machine200pulls tows240of a composite material, such as carbon fiber-epoxy, from the storage spools225around redirect rollers230, which function to maintain a predetermined tension onto the each fiber or tow240, and through redirect pulleys235to the delivery head215. Each tow240, in turn, is cut to the correct length by a cutting blade in response to a command from a control unit135, as the material course, also called a tow band, is laid over the substrate210. Each tow240has a corresponding cutting blade, however the number of blades may vary depending upon the number of tows240and the width of each tow240. As the tows240emerge from the delivery head215, they pass over a compaction roller245which applies and compresses the tows240onto the surface of the substrate210as it moves relative to the delivery head215. Heat may be applied to the tows240immediately before they are placed on the substrate210in order to increase the surface tackiness of the resin impregnated tow. Tension can be maintained on the tows210to assist in pulling them through the AFP machine200as sensed by redirect rollers230controlling the tension brake system250.

FIGS. 3 and 4illustrate a partial cross-sectional view and an exploded view, respectively, of one example of a delivery head215. In the example shown inFIGS. 3 and 4, the delivery head215comprises a “vee block”350having a plurality of air fittings384coupled to passages352located within the vee block350, through which air pressure can be ducted during operation. The air fittings384are compatible with conventional pneumatic valves configured to control the operation of the delivery head215per predetermined instructions from the control unit135. The delivery head215is comprised of a first, upper tow control module354A and a second, lower tow control module354B, which contain substantially identical components located in complementary positions. The tow control modules354A,354B guide the tows240through the delivery head215during operation, as described above. For simplicity, only the components of the upper tow control module354A are separated in the exploded view ofFIG. 4.

Each tow control module354comprises a tow guide tray356coupled to the vee block350, which establishes the configuration of the tow feed path as set by the tow channel dimensions358within the tow guide tray356. The total bandwidth output is defined by a plurality of tow guide channels358corresponding to the number of tows240for which the delivery head215is designed. For example, in the specific case illustrated inFIGS. 3 and 4, both the upper tow control module354A and the lower tow control module354B include a tow guide tray356having three tow guide channels358each, meaning that the delivery head215is configured to place up to six tows240of composite material (three tows240from the upper tow control module354A and three tows240from the lower tow control module354B) simultaneously on the substrate210during each course in an aligned edge on edge pattern.

The delivery head215further comprises a plurality of pushrod/piston subassemblies360, corresponding to the selected number of tow guide channels358. Each pushrod/piston subassembly360comprises a first, cutter retract piston360A, a second, clamp piston360B, a third, feed piston360C, and a fourth, cutter extend piston360D. In the illustrated example, the cutter retract piston360A, clamp piston360B, feed piston360C, and cutter extend piston360D all include bias springs362. Each pushrod/piston subassembly360is located in a series of cavities364in the vee block350, which are aligned with a corresponding tow guide channel358.

Each tow control module354also comprises a support frame366coupled to the tow guide tray356, as well as a cutter rocker arm368with an attached cutter blade370and a pinch/feed rocker372with an attached pinch roller374for each tow guide channel358. Each cutter rocker arm368is coupled to the support frame366by a first, cutter rocker axle376A, on which the cutter rocker arm368pivots during operation. Similarly, each pinch/feed rocker372is coupled to the support frame366by a second, pinch/feed rocker axle376B, on which the pinch/feed rocker372pivots during operation. Although the first, cutter rocker axle376A is illustrated as a single, unitary member for all three cutter rocker arms368shown inFIG. 4, in some cases, the first, cutter rocker axle376A may be subdivided into multiple members, each one corresponding to an individual cutter rocker arm368. Each tow control module354also comprises one or more blade covers378coupled to the support frame366, which are configured to cover the cutter blades370during operation.

The cutter rocker arms368and pinch/feed rockers372of the delivery head215are substantially symmetric, which may advantageously reduce twist and binding distortions in some instances. Each pinch/feed rocker372nests in a pocket of a corresponding cutter rocker arm368, except near the back end, where tabs extend for engagement by a feed piston360C. At the locations of the tabs in each pinch/feed rocker372, the corresponding cutter rocker arm368steps up to allow adequate rotation of the pinch/feed rocker372. Each cutter rocker axle376A is located high enough to allow the corresponding pinch/feed rocker372to rotate, and the tow control module354is preferably designed to substantially minimize the amount of overall rotation required.

The delivery head215further comprises a compaction roller245coupled to the vee block350configured to contact the substrate210where the vee block350forms a nip point at the intersection of the vee pattern fiber feed to a contact intersection point under the compaction roller245. In addition, the delivery head215comprises a first, upper feed roller382A and a second, lower feed roller382B coupled to one or more suitable drive mechanisms, such as a servo actuator. The feed rollers382A,382B form a nip compaction pull force when pinch roller374is activated by pistion360C acting on pinch/feed rocker372to contact feed roller382. The force acts to pull the tows240of composite material through the upper and lower tow control modules354A,354B, respectively, at a desired speed and for a desired time duration, under the direction of a suitable control module, such as the control unit135shown inFIG. 1.

Unlike conventional AFP delivery heads, the delivery head215of the present application includes various distinctive features that optimize the delivery head215for short courses and flat or nearly-flat charges. For example, the total distance from the tow drop off or cutting point to the roller nip area is reduced by compaction roller245, which is substantially smaller in diameter than a conventional compaction roller, and additionally by the compact design of the tow cut add mechanism which places the cut off point to the nip point closer. Specifically, in some cases, the compaction roller245has a diameter of no more than about ¾ inch.

In addition, the delivery head215includes cutter blades370with a unique circular cutter geometry, rather than the traditional rectangular shape utilized in conventional cutter blades. The circular cutter blade design advantageously allows the delivery head215to utilize cutter blades370that are substantially shorter than conventional AFP cutters. Specifically, in some cases, the cutter blades370have a maximum length of no more than about ¾ inch. The circular cutter blade design also advantageously eliminates the need for blade guides, because the cutter blades370can cut equally well in every orientation. Additionally cutter life is extended by cutter rotation during use about the center cutter mounting point. The circular cutter blades370are also easily accessible, removable, and replaceable.

In conventional AFP machines, the pneumatic conduits and other equipment used to actuate the pushrods and pistons are typically coupled to the exterior of the tow control modules and the vee block. As a result, conventional AFP delivery heads can be bulky and cumbersome, making it difficult fabricate small composite parts with short course lengths. The delivery head215of the present application, by contrast, employs a unique design in which the air fittings384are nested between the upper and lower tow control modules354A,354B, and air pressure is ducted through passages352located within the vee block350to control the operation of the pushrod/piston subassemblies360. This compact configuration advantageously enables the delivery head215to utilize a low-profile design for the tow control modules354. Specifically, in some cases, the tow control modules354have a maximum height of no more than about ¾ inch.

FIGS. 5A through 5Dillustrate the positions of a pushrod/piston subassembly360A-360D during various operational stages of the AFP process. In general, the pistons360A-360D are spring biased in a retracted position, and can be extended by supplying air pressure to the desired cylinder bore cavities364of the associated activation pistons360A-360D through the corresponding air fittings384and passages352. This can be accomplished with various control valves and other control equipment (not shown) using conventional techniques and control methods processed within control unit135that are well-known to those of ordinary skill in the art.

FIG. 5Aillustrates the “tow feed” stage of the AFP process, during which a tow240of composite material is pulled through the delivery head215by the feed roller382. During this tow feed stage, as shown inFIG. 5A, the cutter retract piston360A is extended and the cutter extend piston360D is retracted, to prevent the front end of the cutter rocker arm368from lowering to engage the cutter blade370. In addition, the feed piston360C is extended, which lowers the front end of the pinch/feed rocker372and brings the pinch roller374into contact with the feed roller382in contact with pinch roller374as activated by feed piston360C. The clamp piston360B is retracted to ensure that the tow240of composite material can be pulled through the corresponding tow guide channel358under the control of the feed roller382, at the desired speed and for the desired duration.

FIG. 5Billustrates the “free run” stage of the AFP process, during which a tow240of composite material passes through the delivery head215as the desired material course is placed on the substrate210. During this free run stage, as shown inFIG. 5B, the feed piston360C is retracted, while all the other pistons remain in the same position as during the tow feed stage shown inFIG. 5A. The retraction of the feed piston360causes the pinch/feed rocker372to pivot around the pinch/feed rocker axle376B, lowering the back end and raising the front end of the pinch/feed rocker372. This rotation, in turn, causes the pinch roller374to disengage from the feed roller382, thereby allowing the tow240of composite material to pass freely through the tow guide channel358due to the movement of the substrate210and/or the delivery head215during the placement of the material course on the substrate210.

FIG. 5Cillustrates the “tow cut” stage of the AFP process, during which a tow240of composite material is cut to a desired length by the cutter blade370. During this tow cut stage, as shown inFIG. 5C, the cutter retract piston360A is retracted and the cutter extend piston360D is extended, while all the other pistons remain in the same position as during the free run stage shown inFIG. 5B. The retraction of the cutter retract piston360A and extension of the cutter extend piston360D cause the cutter rocker arm368to pivot around the cutter rocker axle376A, thereby lowering the front end of the cutter rocker arm368and causing the cutter blade370to pass through the tow guide channel358and cut the tow240of composite material to the desired length.

FIG. 5Dillustrates the “tow clamped” stage of the AFP process, during which a tow240of composite material is held in place in the delivery head215after being cut by the cutter blade370. During this tow clamped stage, as shown inFIG. 5D, the cutter retract piston360A is extended and the cutter extend piston360D is retracted to disengage the cutter blade370. During this step, the circular cutter blade370may rotate due to vibrations or other forces, thus advantageously providing a new cutting edge on the same cutter blade370for the next tow cut. At substantially the same time, the clamp piston360B is extended to exert a force on the tow240and hold it stationary in the tow guide channel358. Without this clamping step, the tow240may have a tendency to recoil after being cut due to the tension caused by the remaining length of tow material stored on the corresponding storage spool225. By holding the tow240stationary, however, the AFP machine200can accurately determine the location of the end of the tow240, and can thus accurately position the delivery head215for placement of the subsequent course of composite material on the substrate210.

In conventional AFP machines, the cutter blade is normally actuated by a single, dual-acting air cylinder, i.e., a single air cylinder that “pushes” the cutter blade to engage the cutter and “pulls” the cutter blade to disengage the cutter. In the AFP machine200of the present application, by contrast, the advance and retract functions of the cutter blade370are separated into two pistons (e.g., the cutter retract piston360A and the cutter extend piston360D). This configuration advantageously eliminates the need for at least one rod seal and simplifies the mechanism by using only pushrods with no “pull” requirement.

As a result of the features described above, the AFP machine200of the present application advantageously has a minimum cut length that is substantially shorter than the minimum cut length of a conventional AFP machine. For example, in some cases, the AFP machine200of the present application can cut tows240of composite material to lengths as short as about 1½ inches. As a result, the AFP machine200of the present application advantageously allows economical application of the AFP process to small composite parts, especially flat or nearly-flat charges. This may include certain composite parts (e.g., spars, etc.) in which an area being compacted by the AFP machine200is flat or nearly-flat locally, while the composite part(s) may have curved portions, e.g., a tight convex curvature at a radius from a web to a flange.

Referring toFIGS. 6-7, the systems and methods of the present application may be implemented in the context of an aircraft manufacturing and service method600as shown inFIG. 6and an aircraft700as shown inFIG. 7. During pre-production, exemplary method600may include specification and design602of the aircraft700and material procurement604. During production, component and subassembly manufacturing606and system integration608of the aircraft700takes place. Thereafter, the aircraft700may go through certification and delivery610in order to be placed in service612. While in service612by a customer, the aircraft700is scheduled for routine maintenance and service614(which may also include modification, reconfiguration, refurbishment, and so on).

As shown inFIG. 7, the aircraft700produced by exemplary method600may include an airframe720with a plurality of systems722and an interior724. Examples of high-level systems722include one or more of a propulsion system726, an electrical system728, a hydraulic system726, and an environmental system728. Any number of other systems may be included. Although an aerospace example is shown, the principles of the disclosed embodiments may be applied to other industries, such as the automotive industry.

Apparatus and methods embodied herein may be employed during any one or more of the stages of the production and service method600. For example, components or subassemblies corresponding to production process606may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft700is in service612. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the production stages606and608, for example, by substantially expediting assembly of or reducing the cost of an aircraft700. Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft700is in service612, for example and without limitation, to maintenance and service614.

Although this disclosure has been described in terms of certain preferred configurations, other configurations that are apparent to those of ordinary skill in the art, including configurations that do not provide all of the features and advantages set forth herein, are also within the scope of this disclosure. Accordingly, the scope of the present disclosure is defined only by reference to the appended claims and equivalents thereof.