Flexible fabricating punches up productivity.
"A flexible manufacturing system can produce parts with almost no setup cost. That's where to look. When you eliminate time-consuming and labor-intensive setups, you begin to realize the vast potential for FMS productivity."
Onan, a subsidiary of McGraw-Edison, manufactures portable and stationary electric generator sets, diesel and gasoline engines, alternators...they're heavy-duty metalworkers and they practice what they preach. The firm recently purchased a $2.5-million FMS for fabricating from Trumpf America Inc, Farmington, CT. The turnkey system will automate Onan's entire sheet-metal part production, and might be the most comprehensive fabrication FMS installed in the US.
The entire FMS is comprised of many integrated subsystems, Figures 1 and 2. The automatic storage and retrieval subsystem (AS/RS), for example, has a rack consisting of 51 material bins, each capable of holding 6600 lb of sheet or plate stacked to a height of 6-1/2" and serviced by a stacker crane. A second rack can be added for future expansion.
Herehs how the FMS operates.
A guided transfer cart delivers pallets of raw material to an automatic sheet loader. A thickness sensor and double-sheet detector ensure correct single-sheet transfer.
A vacuum-cup lifter transports a sheet of work material to the machine tool, a Trumatic 180 Laserpress that combines punching and contouring with laser cutting (800 W Co.sub.2.; both pulsing and continuous wave). The machine handles up to 1/4"-thick sheets.
The press features X-axis stop-pin location and four clamps for Y-axis registration. Electronic sensors ensure overall material registration prior to processing.
Unlike conventional turret punch presses, the FMS is serviced by a robot toolchanger. The three-axis programmable robot has a double-ended, rotary, axial gripper. The end effector removes a preloaded tool cartridge from the press, rotates, and inserts a new cartridge. While the machine punches and laser cuts, the robot returns the used tool to its appropriate location in the storage towers, then selects the next tool.
the rotary tool towers are designed to allow many tools in a limited space, and minimize the locations programmed for the robot. Each of the 10 circular levels in a tower holds 10 tools.
Whiel three towers provide the necessary number of preloaded tool cartridges for continuous automated production, up to four towers may be specified. Using a new Multitool unit (i.e., a single cartridge carrying up to four tools), the system has capacity for 1600 tools.
Finished parts up to 8" X 16" enter a programmable drop chute adjacent to the laser cutting head and are directed to a small-parts sorter. A linear shuttle, with six bins, sorts part-size categories.
Larger parts are picked up by an unloading device that has 72 densely arranged suction cups individually programmed to conform to hole patterns and sheet size. Under program control, these parts are conveyed to one of nine sorting pallets in two shuttle carts. Long strips of offal are sorted into bins at the front of the carts and may be used in other progressive-die operations, thereby optimizing raw-material use.
Finally, forklifts remove filled pallets, transporting them either to storage or other manufacturing areas. According to Trumpf, wire-guided vehicles or other transport systems can be incorporated here to fully automate the FMS.
Onan's Iacoe emphasizes, "Delivery of the system culminated nearly two years of effort. Our manufacturing engineers surveyed leading equipment manufacturers on three continents, visiting numerous installations, before selecting Trumpf. In effect, we formed a partnership with them to do something in sheet-metal FMS that hasn't been done before in this country."
DNC synchronizes and controls all activity in the FMS, Figure 3. Production at Onan is being converted into a queuing process that automatically generates nested parts on sheets in two modes--one for ongoing production, the other for exceptions that need expediting. The DNC continuously monitors inventory, tooling (e.g., hit count and regrind status), and work in progress.
The DNC system is hardware-independent, which allows any compatible computer to be incorporated. In Onan's case, the brain is a DEC VAX-750, multitasking, multiuser, 32-bit speed demon.
DNC begins with input concerning tooling inventory in the towers and material in the storage and retrieval system, incoming order information, and part definition supplied by a Computervision CAD/CAM system. Tool-path information can be accepted in three formats: APT source code, an APT-CL document, or actual NC code. This data enters a System Planner software module, which performs nesting calculations that consider burden and penalties for breaking a lot run, and prepares both suspended and ready-to-execute job lists.
A System Schduler software module groups jobs according to priority and efficiency. For instance, when feasible, jobs calling for the same gage material are grouped sequentially, rather than separated by jobs requiring different material gages.
Jobs are run by an execution Controller software module that interfaces with a graphics monitor and an exception handler (one of the first implementations of a shop-floor expert system). The EC manipulates all operations of the AS/RS, the laser press, sheet loader and unloader, part sorter, and robot tool-changing system.
Initial production is scheduled this month. Over 1000 part numbers already are programmed for the system, with full production expected by the end of the first quarter (approximately 5000 total part numbers).
For more information about flexible-fabricating technology, circle E62.
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|Publication:||Tooling & Production|
|Date:||Jan 1, 1985|
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