Shop Solutions: Robots Automate Pipe Welding
Reinke Mfg. Co. Inc. employs nearly 400 people--about half the population of Deshler, NE, where the company manufactures center-pivot and lateral-move irrigation systems. Demand for skilled workers far outstrips the available supply: at one point, the company had more than 50 job openings. With production demands increasing and no end to the labor shortage in sight, Reinke recently implemented robotic automation.
The fully automated, 60' (18.3-m) long system includes 10 robots that weld flanges, brackets, and couplers onto irrigation pipes, and also perform plasma cutting of holes and material handling. Six of the 10 robots automatically change end-of-arm tooling to perform multiple processes--either material handling and arc welding or material handling and plasma arc cutting.
Supplied by Motoman (W. Carrollton, OH), the robot system processes multiple configurations of irrigation pipe with 6, 6 5/8, and 8 5/8" (152, 168, and 219-mm) diameters in 19, 24 and 38' (5.8, 7.3, and 11.6-m) lengths. Wall thickness of the carbon steel pipes is 0.100" (2.54 mm), and they weigh up to 380 lb (172 kg) each. Component tolerances allow a nominal fit-up clearance of 0.050" (1.3 mm) to accommodate automated assembly and welding processes. Because steel pipes grow and shrink with temperature variation, pipes are singulated and plasma-cut to length shortly before coming to the robot cell in order to maintain ±1/16" (1.6 mm) length tolerance.
For each pipe, two UP350-200 robots each pick up a pre-oriented pipe flange from one of two 180º indexing positioners located at opposite ends of the workcell. The robots place their respective flanges in the Station 1 flange welding station headstock/tailstock. A tube dispenser loads a pipe into the infeed conveyor, trims it to length, and moves it longitudinally into the weld system, positioning it up against a solid stop.
Moving with coordinated motion, the two robots grasp a pipe by both ends and transfer it from the staging area to roller steadyrests in Station 1. The robots are equipped with a parallel gripper for pipe handling and a three-jaw chuck that grabs flanges and also picks up a welding torch for flange-to-pipe welding.
"This is one area where we initially had some difficulty both in design and application," recalls Manufacturing Engineer Brian Schardt. "Reinke's flange-to-flange seal is unique in the irrigation industry. The pipe is inserted through a tapered flange to create a pocket for our V-Ring seal, which provides a positive seal with no water restriction."
Because the pipe had to insert through the flange on either end of a 38' pipe with a gap smaller than 0.050", Reinke made changes to the flange design based on a recommendation from Motoman engineers to aid in part fit-up and create a stronger weld joint. The design of the tapered knives in the headstock and tailstock of Station 1 made it possible to guide the pipe through the flange ID.
One of the robots is mounted on a 19' servo track, along with a bulk weld wire feeder, tailstock with fixture, and Station 1 steadyrest. This robot moves along the track to push the pipe into the flanges. Tapered knives center the pipe during pipe and flange assembly. Pins on the headstock positioners locate the flanges, and pneumatically actuated paddles clamp the flanges during welding.
Next, the same robots pick up two welding torches for simultaneous welding of the two flanges while the headstock/tailstock rotates the pipe. Automatic nozzle cleaning/torch reaming occurs at preset intervals.
The robots return the welding torches to their nests, then grip the welded pipe/flange assembly and transfer it from the flange welding station to the bracket/coupler welding station (Station 2). Pneumatic steadyrests automatically adjust 4" (100 mm) longitudinally, as necessary, to accommodate bracket and coupler placement on the different pipe configurations.
During flange welding, four Motoman UP20 robots equipped with two-jaw parallel grippers pick up plasma cutting torches and cut holes for anywhere from two to 15 couplers in a pipe/flange assembly. After cutting the requisite number of holes, the four robots set down their plasma cutting torches, pick up one bracket each from one of two vibratory feeders, and position the brackets on the pipe for welding. Four UP20-6 robots, equipped with welding torches, tack and then finish-weld the brackets.
While the latter four robots weld the brackets, the first four robots each pick up a coupler from one of two vibratory feeders and place the couplers in position for tack welding. The UP20-6 robots then tack and finish-weld the couplers.
All eight robots then move to a home position while the pipe ejects automatically onto an idle station. The two UP350-200 robots that started the process place a pipe/flange assembly into Station 2, then remove the finished assembly from the idle station and place it on gravity rails. Pipes transfer laterally to the next operation.
Multiple robot control technology facilitates the complex, coordinated motion required for production and automatically prevents collisions. One controller provides a single point of programming control for two UP350-200 (material handling and welding) robots and two of the four external axes (servo track and headstock) at Station 1. Two controllers control four robots each and the headstock at Station 2. An Allen-Bradley SLC/505 PLC provides overall cell control.
Cycle time for processing a 38', 6-5/8" diam pipe with four couplers, eight brackets, and two flanges is 122 seconds. Even more significant, the system reduces direct labor requirements per shift by 75%, while improving hourly production throughput by 93% (29 pipes welded robotically versus 15 welded manually). No jobs were eliminated; workers were shifted to other operations within the plant. The robot system also virtually eliminates weld spatter on pipe.
"The reduction of skilled welders required to produce water pipe was our major goal with this system," Schardt says. "To produce the same number of water pipes per shift as the automated robotic cell with two operators, Reinke would have to employ eight skilled welders. Now these talented welders can be dispersed into our other weld operations, improving efficiency and overall capacity."
Shop-Floor System Provides Tool Management
MetalQuest Unlimited (Hebron, NE) is a 40-person shop that serves customers in the oil field, energy distribution, hydraulics, agriculture, electronics, and automotive industries. The company uses CNC lathes, machining centers, and other automation on the shop floor, but what it needed was an improved way to manage its tooling inventory.
"We wanted a better way of gathering tool use information at point-of-use to better understand the consumption rate of metalcutting tools used for particular jobs," explains President and founder Scott Harms.
Harms, who started the company in 1996 with a single CNC lathe, found what he was looking for at a trade show when he became acquainted with the ToolBoss, a point-of-use tool management system from Kennametal (Latrobe, PA). MetalQuest purchased a one-bay ToolBoss unit, added another bay six months later, then added two more bays. The system now stores more than 2500 tools, and controls keys to other cabinets that contain hundreds more items.
Besides giving operators an orderly storage system for inserts, tools, tool parts, and other shop material, the system enables MetalQuest to save time and money by tracking tool inventory, raising operator accountability, and providing data on tool use. Multiple items can be stored in a single drawer in a more organized fashion than before, and MetalQuest has real-time tracking of inventory levels. Operators can now find the item they need in 30 seconds, compared with minutes of searching through drawers, toolboxes, and canisters on the shop floor.
The company integrated ToolBoss software with its setup sheets, which tell operators what tools they'll need for a job. "Employees were quick to accept ToolBoss on the shop floor," says Harms. "In a couple of days, they learned how the system works and integrated it with their routine. Lack of trust was never a factor in implementing the system."
Operation is straightforward. After swiping an ID card through the card reader, users select the item and quantity they need from an on-screen list customized for each machine operator. A green light on the front of ToolBoss tells the operator that the selected item can be taken from the drawer.
The system allows the drawer to open only as far as necessary to get the desired tools. The operator takes his items, shuts the drawer, and uses the light pen to sign off.
ToolBoss is powered by a Windows-based PC that runs Kennametal's Automated Tool Management Solutions (ATMS) software. The package includes a real-time ordering option; database maintenance for checking stock, inventory analysis, and order placing; and ability to control up to 10 bays in a single unit. LEDs and photocells sense a drawer's location, and a solenoid locks it into position so an operator can obtain the necessary tooling.
MetalQuest intends to use the system more extensively for job costing based on operator and materials costs. "The data ToolBoss provides can be extremely helpful in letting us know, with as much certainty as possible, that we are maximizing our productivity and profitability on each job," Harms explains.
Filtration Key To Untended Grinding
When Tom Pankratz launched Advanced Tooling Inc. (ATI; Mt. Calvary, WI), his vision was to build a business manufacturing the difficult carbide tooling that others couldn't or wouldn't take on. Pankratz's experience as a toolmaker taught him that his company's competitive advantage would be gained from employing skilled labor and providing them with all the technology available to their industry.
While many shops focus on machine capabilities and wheel performance, Pankratz quickly recognized that grinding oil filtration could be critical to overall productivity and efficiency. Installation of a centralized filtration system to service three grinders yielded immediate benefits. Unlike the cartridge filters previously used, the patented system from Transor Filter USA (Elk Grove Village, IL) delivers consistent 1-µm filtration while an attached chiller keeps grinding fluid at a constant temperature to further improve overall performance.
Pankratz enumerates many benefits of the filtration system, including overall cleanliness, eliminating disposal of messy cartridges, and reduced machine maintenance and downtime. On the consumable side, grinding wheels have been delivering a minimum of 25% longer life, and Pankratz estimates filtration will add several years of life to his capital equipment.
In addition to tackling customers' difficult tooling needs, ATI has found a niche manufacturing small tools. "The small tools market started as a natural extension to ATI's basic mission," Pankratz explains. "We found a need in the market for tools ranging from 3/8" [9.6 mm] diam all the way down to 0.005" [0.13 mm], with the vast majority of production being 1/8" [3.2 mm] or less."
To address this need, ATI purchased two Rollomatic GrindSmart 620XS grinders. The six-axis machines provided flexibility to profitably handle varying geometries and small batch requests, and could maintain concentricity of 0.0001" (0.03 mm). An additional Transor system was purchased to service these machines. Filtration is especially critical for production of small-diameter tools. Eliminating particles in the grinding fluid also eliminates them from the wheel, where any deflection impacts product finish and quality.
Using the integrated load/unload feature of the Rollomatic 620XS, ATI has been able to implement an untended third shift when production demands it. The company has run batches of up to 500 blanks by running smaller customer orders during the day, then setting up for a larger batch that will run through the night untended.
Pankratz notes that, even with a climate-controlled shop, temperature varies from daytime to nights and weekends. The accuracy of the Rollomatics, coupled with the chilled and filtered oil, minimizes thermal variances to allow ATI to run untended with confidence. "What it's enabled us to do is run lights-out on any size tool and hold 0.0002 - 0.0003" [5 - 7.5 µm] on diameter," Pankratz says. "That's pretty amazing."
Recently, ATI was able to supply bone drills to a medical equipment manufacturer. The titanium drills needed to be 6" (152 mm) long but only 1/16" (1.6 mm) diam.
The job, requiring production of 2000 pieces/month, might normally create a production bottleneck. Pankratz decided that this project would be ideal for untended production on the two Rollomatics. Now, because filtration allows accurate prediction of wheel wear, this job is scheduled to run one weekend a month.
Free-Machining Stainless Saves Time, Money
G.W. Lisk Co. Inc. (Clifton Springs, NY), a manufacturer of solenoids, valves, linear variable differential transducers (LVDTs), and other components, was having a hard time machining two stainless valve components for high-temperature applications.One part, a valve shaft, was Type 431 stainless steel, and the other was produced from 15-5 stainless. Type 431 provided the high strength, corrosion resistance, toughness and hardness required for the first part. The 15-5 alloy offered high strength, heat resistance, and corrosion resistance. But the machinability of both materials was unacceptable.
The Type 431 component was turned from bar on a Nakamura Tome TW-20 twin-spindle CNC machine. Operations included drilling, turning, boring, milling, slotting, deburring, and cutoff. Machining cycle time per part was 5 min, 6 sec--too slow for the plant to ship the required 1500 parts per week for four months.
Tools such as end mills, slot cutters, and drills broke frequently, or required excessive maintenance. Burrs created in milling the t-slot had to be cleaned off with an abrasive brush, at substantial cost in labor and productivity.
Unable to keep up with demand for the components, Lisk asked Carpenter Technology Corp. (Reading, PA) for ideas for improving machinability of the Type 431 stainless. The company recommended a custom powder metallurgy (P/M) version of the alloy with increased sulfur content.
Carpenter's Micro-Melt P/M process converts gas-atomized metal powders into 100%-dense finished products. This, plus the sulfur addition, gives the alloy the improved machinability compared with conventional Type 431.
As a substitute for the conventional stainless, the P/M alloy provided much improved machinability while retaining the essential properties demanded of the material. Lisk was able to reduce part cycle time to 3 min, 27 sec. The time needed to machine 1000 parts was 55 - 58 hr, down from the best previous experience of 93 hr. Tool life doubled, and deburring has been reduced to a minimum. Discounting the higher cost of the improved alloy, Lisk Purchasing Manager Steve Cheney estimates that it has helped the company reduce machining costs for this part by approximately 40%.
The contractor making the second part for Lisk machined it from 15-5 stainless bar on a CNC turning center. Bars received from the steel supplier normally had to be cut and sent to a commercial heat treater for aging and heat treatment before machining.
Still, machining operations including turning, drilling, boring, and tapping were slow. Carbide tools broke prematurely or required frequent maintenance. Downtime for tool sharpening was burdensome, labor costs escalated, and productivity suffered.
The alternative alloy, known as Carpenter Project 70+ 15-5 stainless, offers all the attributes of the original alloy while providing improved machinability. Lisk took delivery of the material in the pre-aged condition, eliminating the need for outsourcing aging and heat treatment.
CNC supervisor Dave Phillips estimates that the machinable alloy has resulted in more than doubled tool life, increased productivity by about 35%, and saved a similar percentage in costs for labor and machine downtime for maintenance and tool sharpening.Digital NDT Inspects Prosthetic Parts
A computed radiography (CR) system is helping Stryker Orthopedics (Limerick, Ireland) achieve considerable cost savings in the inspection of components for prosthetic joints, such as knees, hips, and shoulders. The digital system is also allowing significant savings in space over the original wet-film X-ray system while simplifying the archiving of results and improving traceability.
Stryker is a global provider of orthopedic implants with 2004 sales of more than $4 billion. Its Limerick factory manufactures standard and special implant systems used in trauma surgery and for cancer patients who have suffered bone degradation.
Metal components for the joints are investment-cast from a cobalt-based alloy, and undergo X-ray examination to ensure there is no porosity or shrinkage during casting. Porosity could harbor bacteria when the implants are fitted, while shrinkage causes structural weakness.
The plant had used conventional wet film X-radiography for casting inspection since it opened in 1971. However, film archiving and costs had become issues, and environmental concerns were increasing because of the silver content in the film developing tank effluent.
As a result, in 2003 the plant decided to investigate CR. Following a rigorous appraisal of available systems, managers asked GE Inspection Technologies (St. Albans, Hertsfordshire, UK) to provide a digital solution for casting inspection. The system, which had to be compatible with the plant's existing 350-kV Pantak X-ray unit, has allowed Stryker to contain its X-ray facility within a much smaller area while providing faster throughput, improved image definition, and reliable and repeatable operation.
Since installation, the digital X-ray system has provided cost savings of 11,000/month, in ease of use, simplification of archiving, and shareability. CR also impressed the company's quality audit body, which made special mention of the validation and process control associated with the system during a recent audit.
This article was first published in the September 2005 edition of Manufacturing Engineering magazine.