Patent Application
20080083308
The present invention provides, in an embodiment, a method of net trimming or cutting a composite layup at an oblique angle. The composite layup or preform cut by this method include, at least, composite materials such as unidirectional tapes, fabrics, foils, and/or films that have been pre-impregnated with a resin “prepreg” and/or composite materials that have been otherwise bound or tacked together. In this embodiment, a sequence of cuts is performed that reduces drag upon a cutting blade. That is, resistance and adherence of the layup to the blade is reduced. By reducing drag, movement of the plies relative to other plies in the layup is reduced and bending force or deflection of the blade is reduced. In this manner, the sequence of cuts performed according to an embodiment of the invention increases accuracy of the final cut and minimizes disturbance of the layup, thereby, increasing production, reducing production cost, and decreasing waste associated with unacceptable movement of the layup during cutting.
The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. As shown in
The stylus 16 includes any suitable cutting, scoring, and marking device. Depending upon the material to be cut and/or the particular application, the ultrasonic transducer 18 is optionally included to facilitate cutting the layup 14. For example, some composite material utilized to fabricate the layup 14 may be difficult to cut without vibrational energy supplied by the ultrasonic transducer 18. When cutting such materials, the ultrasonic transducer 18 is preferably included. When utilized, the ultrasonic transducer 18 is configured to impart vibrational energy upon the stylus 16. The stylus 16, when thusly energized, may generate a crack front in the layup 14 that proceeds the stylus 16 and facilitates cutting.
The positioning device 20 moves or positions the stylus 16 relative to the layup 14. In various embodiments, the positioning device 20 includes a head or stylus orientation assembly to rotate the stylus 16 about one or more axes. The positioning device 20 may also include a gantry, robotic armature, X-Y table, or the like to move the stylus 16 relative to the layup 14. Movement of the stylus 16 relative to the layup 14 may be controlled in any suitable manner.
An embodiment of the present invention pertains to a method of cutting an uncured layup of up to about 20 composite plies. In a specific example of this method, a periphery of the composite layup is cut with the stylus 16 (e.g., an ultrasonic knife, or the like) oriented vertically relative to the layup 14. The stylus 16 is controlled to penetrate up to 0.05 inches (1.27 mm) into the tool 12 or other such supporting substrate on which the layup 14 is supported. In addition, as shown in
According to an embodiment, while performing the periphery cut 32 the stylus 16 is controlled to penetrate or cut slightly below a bottom surface of the layup 14 to generate an overcut 34. The overcut 34 facilitates separation of a scrap 36 from the layup 14. In general, the depth of the overcut 34 may be about 0.0 inch (0.0 mm) to about 0.1 inches (2.54 mm). In a particular example, the depth of the overcut 34 is about 0.05 inches (1.27 mm). In another example, the actual depth of the overcut 34 is about 0.03 inches (0.76 mm) given a Z offset of about 0.02 inches (0.50 mm) and setting for the 90° cut of about 0.05 inches (1.27 mm). To reduce wear or damage to the stylus 16, the tool 12 may include a resilient material such as, for example, ultra high molecular weight (UHMW) polyethylene polymers, Delrin®, Vyon® nylon, acetal; and the like. These and other materials may sustain many hundreds or thousands of cuts without undue wear.
In some applications, one or more uncured parts are affixed and co-cured to fabricate a unitary or one piece item. In a particular example, the layup 14 includes a stringer that is a component of an aircraft fuselage. To improve material properties of the completed fuselage, the stringer and barrel are co-cured. To increase an amount of contact area between the stringer and the barrel, the EOP 30 of the layup 14 may be cut at a bevel 38.
Unfortunately, bevel cutting the EOP 30 has several disadvantages. For example, as the cutting angle departs from perpendicular (90°), the length of a cutting edge of the layup 14 in contact with the stylus 16 increases. As this cutting edge length increases, resistance increases. The increased resistance may result in stylus deflection, out of tolerance trimming, layup movement, increased wear of the cutting system, slower feed rates, and the like.
The stylus deflection may be exacerbated by bending forces experienced by the stylus 16. In this regard, cutting at about 90° tends to balance resistance encountered by each side of the stylus 16 and thus, reduce torquing forces experienced by the stylus 16. As the incident angle of the stylus 16 deviates from 90°, the torquing forces may increase. In addition, cuts made into upper surface of the tool 12 at oblique angles may induce premature degradation of the tool 12. This condition may be exacerbated due to the incident angle of the stylus 14. That is, to generate the overcut 34 at a predetermined depth, a greater length of the stylus 16 will penetrate the tool 12 when the stylus 16 is at an oblique angle. In a particular example, to generate the overcut 34 at a depth of 0.05 inches (1.27 mm) and a stylus angle of 22°, about 0.14 inches (˜3.49 mm) of the stylus 16 may cut into the tool 12. Furthermore, this oblique cut may generate a flap in the surface of the tool 12 that may tend to raise an edge and/or break off.
Preferably, the stylus 16 is controlled to essentially cut at or slightly above an intersection of the EOP 30 and the tool 12 and substantially on or parallel to the bevel 38. If the stylus 16 cuts relatively below the intersection of the EOP 30 and the tool 12, a loss in continuity of the EOP 30 may result as the bevel cut may proceed relatively to the inside of the EOP 30. To avoid potential loss in continuity of the EOP 30, the stylus 16 may be controlled to cut relatively above the intersection of the EOP 30 and the tool 12. In a particular example, the stylus 16 may be controlled to cut about 0.01 inches (0.25 mm) above the intersection of the EOP 30 and the tool 12. In another example, the stylus 16 may be controlled to cut essentially at the intersection of the EOP 30 and the tool 12. In actual practice, given a Z offset above the tool 12 of 0.02 inches (0.50 mm) and assuming an approximate downward blade deflection of 0.0005 inches (0.13 mm), the tip of the stylus 16 may, in fact, be about 0.015 inches (0.37 mm) above the surface of the tool 12.
As shown in
As shown in
An embodiment of the present invention relates to a method of cutting a relatively thick uncured layup of more than about 20 composite plies. In a specific example of this method, a periphery of the layup 14 is cut with the stylus 16 oriented vertically. The stylus 16 is controlled to penetrate up to 0.05 inches below the tool 12 or other such supporting substrate on which the layup 14 is supported. In addition, as shown in
In the particular example shown, two intermediate cuts 50a and 50b are shown. However, any suitable number of intermediate cuts 50a to 50n are included in embodiments of the invention. To perform the intermediate cuts 50a and 50b, the stylus 16 is controlled to cut at or just above the bevel 38 (e.g., a nominal bevel surface). Cutting slightly above the nominal bevel surface reduces the likelihood that the intermediate cuts 50a to 50n may score the nominal bevel surface. In a particular example, the stylus 16 is controlled to cut about 0.01 inches (0.25 mm) above the nominal bevel surface. To perform the periphery cut 32, the stylus 16 is controlled to cut essentially at the EOP 30. Preferably, the stylus 16 is further controlled to generate the overcut 34.
In various embodiments, the perpendicular cuts may be performed in any suitable order. For example, the periphery cut 32 may be performed first, followed be intermediate cut 50b, then 50a. Alternatively, intermediate cut 50a may be performed first, followed by 50b, and then followed by the periphery cut 32. In addition, some or all of the cuts 50a, 50b, and 32 may be performed at essentially the same time.
To generate the bevel 38, the stylus 16 may be controlled to perform the bevel cut 40 as shown in
At step 62, it is determined whether one or more of the intermediate cuts 50a to 50n is to be performed. For example, if the layup 14 is relatively thick, the bevel relatively shallow, and/or the composite materials relatively difficult to cut, it may be determined that one or more intermediate cuts 50a to 50n may be performed at step 64. If it is determined that the intermediate cuts 50a to 50n may be omitted, the periphery cut 32 may be performed at step 66.
At step 64, the one or more intermediate cuts 50a to 50n may be performed. For example, as shown in
At step 66, the periphery cut 32 may be performed. For example, as shown in
At step 68, the bevel cut 40 may be performed. For example, the positioning device 20 is controlled to position the stylus 16 to cut along the bevel 38. In various embodiments, the bevel cut 40 may be performed as a single cut that generates the bevel 38 or as two or more bevel cuts 40a to 40n that may be performed along with or alternating with the step 64 and/or step 66. The bevel cut 40 may be performed at any suitable angle. Suitable angles include, for example, about 15° to about 85° relative to an upper surface of the layup 14. More particularly, the bevel cut is performed at about 16° to about 25° relative to an upper surface of the layup 14. More particularly yet, the bevel cut is performed at about 18° to about 21° relative to an upper surface of the layup 14.
At step 70, the scrap 36, 42, and/or 42a to 42n may be removed. For example, the scrap 36, 42, and/or 42a to 42n may be blown, drawn, or swept away. In various embodiments, the scrap may be removed as it is generated or at the completion of the cuts. Following the step 70, the cutting system 10 may idle or stop until another cutting operation is performed.
The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
