Metal fusion bonding – Including means to provide heat by friction between...
Reexamination Certificate
1999-12-08
2001-01-16
Ryan, Patrick (Department: 1725)
Metal fusion bonding
Including means to provide heat by friction between...
C228S002300, C228S045000, C228S025000, C156S073500
Reexamination Certificate
active
06173880
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a friction stir welding apparatus comprising multiple sub-components which collectively perform as one integrated welding system allowing the apparatus to be operated and maintained in a variety of environments while permitting reduced size of the unit. The integrated nature of the sub-components gives the operator more flexibility in the type and size of workpiece that can be welded and effectively expands the utility of the friction stir welding process.
2. Description of Related Art
Friction stir welding is a method of welding based upon the principle of “rubbing” of articles to be joined together so as to generate a sufficient amount of heat. A probe of a harder material than the treated work pieces is typically applied in a welding process. The probe is subjected to cyclic movement relative to the work pieces. Merging the probe and work pieces together has been found to create a plasticized region in the work pieces due to generated frictional heat. When the relative cyclic movement of the probe stops, the plasticized material solidifies to create a weld joint.
The Friction Stir Weld (FSW) process, as it exists today, is believed to be limited to few manufacturing floors. Almost all known systems are restricted to laboratory/development environments. Development and laboratory equipment consists of large off-the-shelf machinery such as machining molds, modified to accommodate the FSW process. The large size of the laboratory equipment places size constraints upon manufacturing and tooling requirements, as a result, it is impractical and cost prohibitive to use machining mills for most manufacturing FSW applications. Additionally, the working envelope of the machining mills prohibits large pieces of hardware to be welded.
SUMMARY OF THE INVENTION
The present invention overcomes the disadvantages of the prior art devices in that large individual components may be replaced with sub-components attached or housed within a common base foundation unit to allow an operator to move the apparatus to the manufacturing floor where a greater range of devices can be operated on.
Accordingly, it is an object of this invention to provide a new and improved friction stir welding apparatus which permits the FSW procedure to be performed on the manufacturing floor, and in other environments that have traditionally been unavailable for use of FSW because of the size and lack of mobility of prior art FSW systems. This system may operate under loads exceeding 20,000 pounds. In addition to welding, the system can also operate as a precision controlled machining center by replacing the pin tool with an end mill/cutting tool.
An integrated welding system is taught herein which features multiple sub-components that are combined to create a self contained and mobile FSW apparatus. A base foundation unit (BFU) serves to either attach or house, or connect, other components. The BFU may be connected directly to a floor for a static welding environment or may be adopted to be mobile for dynamic weld environments. The BFU may accommodate significant axial and radial loads, estimated to be up to 20,000 lbs. or less axial and 2,000 lb. radial. An elevation platform (EP) may be movable in three dimensions and is connected to the BFU. An adjustable pin tool (APT) may be attached to the EP allowing the APT to be positioned in three dimensions . The APT may have movement independent of the EP such as rotational capabilities so it can be introduced into the weld joint at a pre-selected angle. A backplate tooling component may be attached to the exterior of the BFU to act as a backing bar during FSW weld operation. A fixturing component may be attached to the exterior of the BFU for holding and securing the workpiece during welding. A roller mechanism may be also attached to the exterior of the BFU and integrated with the APT to remove any bowing in the material before the joint is welded. Additionally, a real-time adaptive computer numerical control (CNC) and process control system (APCS) may be housed within the BFU. The APCS may be a digital computer system that incorporates common robotic position/motion control electronics and software. The APCS may also have electronics and software for monitoring the parameters of the FSW process. The APCS may analyze these parameters, and dynamically adapt the weld parameters to maintain weld performance.
In a preferred embodiment the integrated movement of the EP and the APT may be performed by hydraulics. The hydraulic system would preferably include a pump and fluid reservoir housed within the BFU. Hydraulic connections may be integrated with the EP and APT such that the operator can guide the pin tool to a desired position on the workpiece. Once the weld position is fixed, the APCS monitors the parameters of the FSW process, analyzes those parameters, and dynamically adapts the pin tool position to maintain weld performance.
Thus the friction stir weld (FSW) process as disclosed can be expanded to include a great variety of materials by integrating the individual components of large milling machines into a single integrated welding system. The process offers significant opportunities relative to costs, manufacturing, quality assurance, and health and safety standpoints for the welding of aluminum and other materials. Advantages of the process have been found to include: (1) a simple machine tool may be extremely energy efficient: a single pass 12.5 millimeter deep weld can be made in 6xxx series alloy using a gross power of less than 3 kW; (2) equipment maintenance has been found to be minimal; (3) the welding operation does not require consumable materials such as filler wire or shielding gas; (4) special pre-weld joint edge profiling may be eliminated; (5) the careful removal of oxide from the joint area immediately prior to the welding may not be required; (6) the equipment is suited for automation and integration with other machine tool operations; (7) good mechanical and metallurgical quality welds may be confidently made in aluminum alloys such as 2xxx, 5xxx and 7xx series which previously had problems such as solidification cracking and/or liquation cracking; (8) high joint strengths may be created in heat treatable alloys; (9) welds may be consistently made which are free of voids and porosity; (10) metallurgical properties in the weld material may be retained such that mechanical and fatigue properties are similar to those of the parent metal; (11) butt and lap seam welds may be created between wrought, cast and extruded materials; (12) weld repeatability is very good when weld energy input and mechanical mechanisms direct and control the working and forging of the weld metal; (13) the welding machine may be simplified to three controls: tool heel plunge depths, tool rotation speed, and welding speed; (14) health hazards such as welding fumes or radiation are severely reduced if not eliminated resulting in a clean process; and (15) alloys other than aluminum may be utilized.
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Ding R. Jeffrey
Oelgoetz Peter A.
Romine Peter L.
Cooke Colleen
McGroary James J.
Ryan Patrick
The United States of America as represented by the Administrator
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