By Patrick WaurzyniakSenior Editor
To meet increasing demands for productivity gains, manufacturers continually ask factory workers to do more with less equipment, and in less factory floor space. The most automated assembly lines make factory floors as efficient as possible, boosting the bottom line in highly competitive manufacturing markets.
Adding the latest in robotics and assembly line conveyor systems can help manufacturers meet the stiff challenges they face. With smaller robotic cells, top-loading robots mounted on gantries, new vision-based robots, simulation software for visualizing robotic cells, and more efficient assembly line equipment, manufacturers can boost productivity and remain competitive.
The productivity argument for employing robotics is easy--doing more with less. But the best automation schemes not only include using the most efficient robots, often with vision or other high-tech features, but also deploying some of the most up-to-date conveyor systems on the factory floor. "Clearly, from the robotic aspect of it, the whole basis of robotics with regard to productivity improvement is pretty widely known," says Greg Fisher, director of product management and engineering, Bosch Rexroth Corp. (Buchanan, MI).
Several new automation products introduced last September at the ATExpo 2003 and earlier this month at the Medical Design & Manufacturing (MD&M) show in Los Angeles offer significant advantages for increasing manufacturing productivity. At ATExpo, Bosch Rexroth brought out several systems including a new line of six-axis articulated robots, a CMS Cartesian Motion System for pick-and-place applications, and its new state-of-the-art easyrobot programming software.
"Our program here is to have a number of physical constructions with a common control," adds Fisher. "We have a simple programming and user interface--that has an obvious benefit to training staff."
Key for customers seeking new automaton systems is to be careful to not buy more robotic or automation equipment than they need to do their job. "The fact that our product is modular from a hardware and a software point of view allows you to tailor your application to what best suits you at that time," notes Fisher.
Efficient conveyor systems also play a key role even as manufacturers seek to implement lean manufacturing strategies or more flexible, agile systems, as have many automotive manufacturers and suppliers in recent years. In Bosch Rexroth's case, its extensive conveyor systems line traces its lineage to bearing applications, and Fisher notes that the company continues to sell a substantial volume of its conveyor equipment line into automotive applications. Bosch recently added to the material-handling applications it services with the new VarioFlow chain conveyor system, which has increased payloads and offers features including overlapping aluminum or stainless steel conveyors that can be useful in even lean or agile plant layouts.
Saving space on the factory floor remains a key goal for most conveyor systems, particularly in a newer lean or agile systems environment. With Bosch's VarioFlow conveyors, its aluminum framing capabilities allow more efficient ways to handle part flow around corners, and the system's ability to use spiral alpine tiers enables manufacturers to save significant square footage on the factory floor, Fisher adds.
Vision-guided robots are increasing in popularity for material-handling duties with metalcutting applications, according to Dick Johnson, general manager, material-handling products, Fanuc Robotics America Inc. (Rochester Hills, MI), who estimates that in 2003 about 10% of robots in material handling included vision capabilities.
"We have certainly seen an increase," Johnson says. "Manufacturers typically want to save money. We have visual tracking where you put a part on a conveyor. You can strobe the part, taking a snapshot of the part, and the robot goes into a line-tracking mode. This means the part doesn't have to be precisely fixtured."
Adding vision and intelligence to the robot helps save manufacturers time and money in applications that previously required exact positioning of parts on the conveyors. "There is a reduced labor cost," says Johnson, "but more significant is a reduction in the tooling costs necessary to load and unload a part."
Last year, Fanuc introduced its new six-axis M-16iB series robots equipped with its latest vision system, the visLOCi vision software, aimed at a variety of medium-payload manufacturing processes for load/unload, palletizing, packing, material removal, welding, and other applications. The software, which Johnson says Fanuc developed in-house, runs on Windows-based PCs and costs considerably less than vision systems have in the past.
"Our company has made a conscious effort to build more intelligence into our robots," Johnson adds, while noting Fanuc's new I-21i robot, a six-axis, "intelligent" robot that is said to perform more skilled tasks due to its combination of 3-D vision and integrated force-sensing capabilities.
"The visLOCi vision software is a 2-D system, but this robot has two major thrusts. It's being used in real-world applications now, with automotive companies using it for anything that is stackable, like sheetmetal parts--an excellent application for a 3-D system. Another one is stacking hydroformed rails, which can be roughly stacked vertically in a bin, or flat transmission covers."
With 3-D visual sensors and bin-picking process software, Fanuc's I-21i robot can pick randomly oriented parts from storage bins. The system uses an overhead camera to locate the parts in the bin, and a robot-mounted camera and a laser sensor accurately determine the location and orientation of the parts. The software allows the robot to pick the parts and place them according to a taught sequence.
"We have two cameras to do the rough find, then the system directs the laser cross-hairs," adds Johnson. "This can certainly be used for sheetmetal and stacked parts, and we're looking at bin-picking for connecting rods. The second part of the system is the tactile feedback given by the six-degrees-of-freedom force sensor. The real-world applications are being developed; for instance, we're using it to put valves in a diesel engine, and also to assemble an automotive transmission clutch assembly. Once you have tactile capabilities, you can do close-hole fitting, like when you put in a valve stem that must fit exactly."
Top-loading robots also are probably the most significant development for loading on metalcutting machinery, Johnson adds. Instead of a single robot tending a single machine, a series of linear gantries equipped with robots can move overhead to load parts into machines. "One of the things gantries do is trace a plane overhead. A linear gantry gets you to a place in space and it doesn't take any space on the floor. We've been using some innovative moonroofs, an opening above the machine that can service the machine. We have systems at Ford, GM, DaimlerChrysler, and many of the Tier One suppliers."
Simulation software for addressing all robotic applications plays a key role in accurately determining a manufacturer's automation needs. Fanuc has its internally developed SimPro offline robot simulation software that helps cut costs and setup times.
"The major advantage, first of all, is cycle time," Johnson says. "When doing a multiple-robot cell, we have the ability to determine accurate cycle time. We had one case where we set it to music. Once you see it done, it becomes crystal clear how to apply robots."
The ease of system design and equipment selection are very important, says Bosch's Fisher. With Bosch's software tools, users can incorporate CAD geometry in designs that simplify the equipment's configuration definition. "That's a time saver on the front end, and the easyrobot software for offline programming gives the customer a PC-based, user-friendly desktop simulation to confirm that your program is going to meet your needs."
System ease-of-use and economics of automation rank at the top of what users look for in today's market, according to Charlie Duncheon, executive vice president, Adept Technology Inc. (Livermore, CA). "Given that there's been a shift of manufacturing to low-cost labor regions, what we really need is a shift toward more yield improvement," he says. "To that end, we attacked both ease-of-use and economics in the last two years. On the economics side, we've taken advantage of our distributed architecture with our high-speed networking."
With its high-speed, pick-and-place Cobra line of SCARA robots, Adept Technology systems feature internal high-speed networking within the robot arms using the ultra-fast Firewire IEEE-1394 networking protocol. The Cobra robots employ Adept's SmartServo architecture, which replaces hundreds of wires and cables with a single FireWire high-speed control bus.
"It's much more than using Firewire in our robots; it's a miniaturization of our control hardware into a much smaller form factor, with arm-controlled robots. Right now, our linear modules and tabletop SCARA robots have it in the arms, and that's an obvious cost reduction," Duncheon says. "Firewire really replaces the backplane--it's faster than the old VME backplanes--plus it was a cost reduction and a space improvement. It has higher performance and also represents a reliability improvement."
PLC-based robots from Adept developed in cooperation with Rockwell Automation (Milwaukee) address the ladder logic market and give the industry the first true PLC-driven robot, notes Duncheon. Introduced late last year, Adept's Cobra PLC robot is a high-performance four-axis SCARA robot with a PLC Server that includes all system configuration, initialization, and programming performed directly from the customer-supplied PLC.
Vision-based systems also remain an Adept strength as its technology recently was selected by Prodosyst Automation (San Diego, CA), a supplier of automated systems for medical device manufacturing, as its standard platform for robots, vision, and controls to be used in Prodosyst's TrueFlex automated medical device assembly system. "It continues to be a growth area, with an increase in robustness and a decrease in cost," says Duncheon of vision-based robotic systems. Prodosyst will use Adept's Cobra robots equipped with AdeptVision and the Adept ObjectFinder locator tool for vision-based part feeding and automated assembly operations.
In robotic welding, a new MIG Force push-pull wire-feed system from Panasonic Factory Automation Co. Ltd. (Elgin, IL) is said to offer high-speed MIG welding of aluminum aimed at high-volume automotive applications. Used with Panasonic's G-series robots, the system offers high-speed and high-reliability welding with speeds to 5 m/min in lap welds and 2 m/min for fillet-lap welds.
In designing the system, Panasonic engineers had to control wire feed speed, pulse waveform, and robot movement within a tightly integrated system. Arc stability and wire-feed speed were the key variables to be controlled. The new aluminum-wire push-pull system enables highly stable feeding of soft aluminum MIG wires using a push-assist motor. In addition to the control, the system has a planetary roller wire feed, a brushless DC servomotor drive, a compact design that can use robots as small as 6 kg, and a power source providing soft, hard, or hybrid control of arc transfer, including programming to manage high-speed welding.
This article was first published in the February 2004 edition of Manufacturing Engineering magazine.