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Finding flexibility in automated assembly.

Remember when the admonition not to fold, spindle, or mutilate was the height of automated data processing? That day is far removed from the current world of fully integrated automated assembly. Assemblies which may range in size from miniature electronics to heavy automotive subassemblies are counted in cycles per minute, per shift, per day, and, ultimately, per year. Over a year, millions can be produced; over the life-cycle of a product, tens of millions may be produced for virtually every industrial and consumer market.

Machines can pick, place, rivet, weld, screw, convey, fasten, crimp, insert, inspect, punch, glue, measure, test, monitor, and correct their own functions, among other operations. Communications are more critical than ever as machines and systems are linked through networks of computers, sensors, programmable logic controllers, and software.

"There is a definite trend toward flexibility in systems, simultaneous or concurrent engineering, and more real-time diagnostic control of automated assembly lines, especially because of the emphasis on quality in manufacturing," says Robert Schaffner, vice president of sales for Giddings & Lewis Integrated Automation, Janesville, WI. One of the key areas of concern for manufacturers today in the area of quality is product traceability, says Mr Shaffner. "The manufacturer must literally know the history of every component through the life of the product due to SPC and even liability considerations,- he says. The result has been that great strides have been made in pallet identification with RF systems that can read and write and create a history that travels along with the pallet through the assembly process. There has been enough experience with concurrent engineering by now for just about everybody to know its benefits. What is certain is that closer cooperation between vendor and/or systems integrator and the customer is apparent today-whether these custom or standard assembly systems are concurrently engineered or sent out for bids in a more traditional manner. Belcan Engineering, Cincinnati, has developed its concept of a partnering relationship into long-term commitments to solving manufacturers' problems for such companies as GM's Delco Products Div, GE's Aircraft Engine Group, Eli Lilly, and DuPont. Partnering with GE's Lighting Div led to the formation of Belcan SEED, the Specialty Equipment Engineering Div, Solon, OH. In addition to providing manufacturing systems to all 25 GE Lamp plants worldwide, Belcan SEED is translating its technology into performance and quality improvements for other manufacturers. "Manufacturers are looking for step improvements today, not incremental gains," explains Wayne j LeBlanc, business development manager. One recent Belcan SEED proposal involving micro-welding technology could increase the throughput fifteen-fold for a potential customer, reducing labor and unit welding costs by 90%.

How automation works

Automated systems are synchronous (in step) or asynchronous requiring queueing) as assembly and process operations may proceed at different speeds. Continuous motion systems like light-bulb making machines perform assembly operations on the fly without indexing and stopping at a workstation. Systems may be thought of as -hard-, i.e. dedicated, when they are used to assemble one or more high-volume complex assemblies with only little variation within the family of products. Processes performed and the number of components involved are as important as cycle times in selecting the type of automated assembly systems. For shorter runs of less complex assemblies at slower cycle times, rotary or rectilinear systems where robots and manual workstations take their turns in assembling, testing, and measuring components and assemblies may be selected.

Getting flexible

Competition may be heating up, however, even for these applications. Bodine Corp, Bridgeport, CT, has announced significant price reductions on its smaller assembly chassis and control packages for its two-, three-, and four-bay versions of the Model 64 modular, in-line assembly chassis, long a standard for high-speed, synchronous assembly. "If an assembly has four parts or less, the traditional thinking has been to go with a 'dial' just on the basis of price," says Bodine vice president William Bodine. With Bodine's new pricing structure which has lopped literally tens of thousands of dollars off the price of both base chassis and the control system package, that's not true any longer, he says. Not included in the price reductions are tooling costs for stations, feeders, and the like which vary according to operations performed. Bodine systems typically achieve speeds as high as 70 cycles/min. Assembly may be the most critical and difficult operation in the manufacturing cycle, especially for the automotive industry. Assembly typically consists of many complex motions and many differing operations yet it requires the consistency, control, and verification of much simpler processes.

At Chrysler's Kokomo transmission plant, Ingersoll-Rand's Automated Production Systems Div has integrated innovative in-process measuring, inspection, and verification operations into two recently delivered systems. Most notable is the inclusion of press-force signature analysis, vision systems at strategic points, testing rolling drag torque, and upgrading to the latest digital linear encoder technology, thus replacing LVDT analogue gaging.

The two Ingersoll-Rand asynchronous lines consist of the low/reverse piston and retainer, bearings, several snap rings, and integral leak test and a preload line to assemble the output drive, transfer, and differential and have a total of 60 stations combining automated, semiautomatic, and manual operations.

Going modular

For a host of precision assembly applications, Schunk Automation has introduced its new modular Assembly Center concept consisting of one or more compact, selfsupporting, microprocessor controlled, fully enclosed units dedicated to specific assembly functions.

The Assembly Center is modular in all aspects- mechanical, electrical, and pneumatic. Work envelope is an 8" (200 mm) cube accommodating workpieces up to 4 lb. The environmentally controlled modules come in three standard sizes: 63" (1600 mm), 39.5" (1000 mm), and 31.5 " (800 mm). All units are 51 " (1300 mm) deep and 78.5" (2000 mm) high.

Fast industrial bus for input/output communication on the module level dramatically reduces cabling requirements. An Ethernet system connects modules.

The AC concept makes hybrid combinations or manual and automated workstations possible. While manual workstations generally have a cycle time of ten to thirty seconds, cycle times to one second are possible with a high-speed pickand-place operation. Upgrading to fully automated operation is simply a matter of inserting the required module. Typical module operations include robotic assembly, soldering, and gluing of complex components, welding, riveting, screwing, testing, and lifting. Additional module functions include such operations as palletizing, washing, cleaning, imprinting, labeling, and other special functions. A speedometer assembly line with 39 stations is currently being completed for Ford in the UK using the Assembly Center modular concept.

Pallet control

The name of the assembly game is still throughput. And logistics may well be the most important consideration in today's automation. Developments in products and systems that get components into the production cycle and out the door are the secret of effective just-in-time manufacturing. Bosch Automation Products has introduced a new computer-controlled material-transfer system that uses intelligent, self-powered, track-riding workpiece pallets to optimize manufacturing flexibility and production economies. Called the CTS 40 system, the self-propelled workpiece pallets ride on non-powered track and provide safe, smooth transport under precise control at unusually high speeds (up to 1.0 m/sec). CTS 40 pallets provide a usable workpiece area of 400 mm x 300 mm and carry a maximum load of 20 kg. The CTS 40 conveyor system can be used to link all areas of a plant (such as parts and material storage, tooling, assembly and process, test, clean room, inspection, finished goods). Parts can be placed directly on the pallets or in special fixtures or work holders as required.

Power requirements for the CTS 40 are said to be just a fraction of that required for a conventional conveyor system of comparable size. The CTS 40 utilizes a passive track and mobile, battery-powered pallets which are recharged when the pallet is stopped at a workstation or queue.

The Bosch ID 80/E control system provides a distributed database on the factory floor with interactive control using a personal computer. Based on RF (radio frequency) data transmission, the ID 80/E consists of mobile data tags (MDT), read-write units (SLS), and a programming package. In the CTS 40 system, an SLS is located at each workstation and communicates with MDTs on pallets routed to that station.

The ID 80/E programming package runs on the Bosch PG 4 programming device as well as the IBM-AT and compatible computers using MS-DOS. Typical tasks handled include part counting/production log, type and part numbers, pallet identification, process step verification, part recognition, sorting, and the like.

Ron Palmer says that Cox Automation is designing its own palletized conveyor system with a pallet size 3" x 3". "We're aiming at the smaller size pallet because it helps minimize travel time between stations and we feel that most manufacturers have standardized on the larger sizes."

A rather unusual approach to materials delivery is a monorail train "transorter" introduced by Amphion Inc's NovaSort Systems Div, Ann Arbor, MI. The NovaSort system resembles a big electric train of tilt-tray carrier cars that travel on a floor, wall, or ceiling-mounted monorail track. Each train is controlled by an on-board computer and is capable of independent "best path" movement.

Robots continue to make inroads in automated assembly, but there is a tradeoff between speed, payload, and reliability, says Scott Baldwin, sales and marketing manager, Kawasaki Robotics USA. And it is ridiculous to expect payback in time periods as short as one or two years. Kawasaki's articulated robots priced in the 50,000-$120,000 range are used for welding and painting, among others.

The potential for robots in certain kinds of applications can not be doubted. According to Donald Vincent, executive vice president and director, Robot Industry Association, Ann Arbor, MI, there are 70,000 potential new customers in the US, since 90% have yet to install their first robot. In hazardous jobs alone there are 200,000 potential applications for robot technology.

The invasion of the Japanese robots continues. Yamaha introduced its YK-8000 series SCARA (Selective Compliance Assembly Robot Arm) at the Assembly Technology Show, calling it the world's fastest SCARA robot. More important, it was priced at under $20,000-a definite breakthrough.

The YK-8085 is capable of completing a 1"-12"-1" cycle in just 0.78 seconds. Models in the YK-8000 series can handle loads up to 44 lb (20 kg) in an X, Y axis envelope of 10" to 31". A new software template translates an AutoCAD drawing directly into path commands for controlling Yamaha robots that cuts programming and set-up time 90% to 20 minutes.
COPYRIGHT 1991 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991 Gale, Cengage Learning. All rights reserved.

Article Details
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Author:Lorincz, James A.
Publication:Tooling & Production
Date:Dec 1, 1991
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Next Article:Combining hot and cold forging.

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