ENGINEERING PRODUCTIVITY KIT Fastening,joining,assembly
Coming: optimized robotics welding
Columbus, OH--1996 showed a 25% increase over 1995 in the number of arc welding robots ordered from robot manufacturers in the U.S., a sign that the use of robots in welding applications continues to increase, according to the Robotic Industries Association (Ann Arbor, MI). Most of these robots use gas metal arc welding (GMAW) and flux cored arc welding (FCAW). The reason: these processes have simple torches, good disposition rates, and tolerance to part fit-up. But they could work even better.
Robotic welding offers many advantages: repeatability, high productivity, and better quality. However, many robot welding technicians lack a thorough understanding of arc-welding fundamentals and, as a result, fail to fully optimize the robot's capabilities, according to Dennis Harwig, senior research engineer at the Edison Welding Institute (EWI). This, in turn, leads to inappropriate selection of consumables and non-optimized weld parameters. The result: higher defect rates, and lower production rates and quality.
Over the last few years, EWI has developed a way to rapidly characterize and optimize arc welding processes. Now, the Institute has undertaken a project to develop a comprehensive welding-parameter database for fillet welds designed to simplify the parameter-selection process and enable assessment of process robustness.
By 1999, the project will develop welding parameter relationships and productivity windows for selected process-consumable combinations over a range of fillet weld sizes. Processes such as GMAW and FCAW will be compared using several consumables for each fillet welding application.
By the project's end, some 50 process-consumable combinations will be evaulated. The yield: considerable cost savings through a minimized need for added parameter development and optimized deposition rates, says EMI's Harwig.
For more information about the high-productivity robotic arc welding project, contact Dennis Harwig, Edison Welding Institute, 1250 Arthur E. Adams Dr., Columbus, OH 43221; ph: (614) 688-5132; FAX: (614) 688-5001; e-mail: [email protected]
Coating conquers airframe rivet problems
Long Beach, CA--The U.S. Air Force touts a new kind of rivet--or, more precisely, a new rivet coating--as a "revolutionary change."
The coating, recently introduced by the Military Transport Aircraft division of McDonnell Douglas and suppliers Hi Shear Corp. (Torrance, CA) and Aerospace Rivet Manufacturing Corp. (Santa Fe Springs, CA), should cut costs, reduce rework dramatically, and prevent fatigue, while improving airframe quality, says Jeff Behnke, project manager at McDonnell Douglas.
The pre-coated dry sealant for titanium pins and aluminum rivets allows mechanics to work faster and cleaner--and do better work, say its developers. McDonnell Douglas C-17 program accountants predict it will save $2.2 million as each new Globemaster III comes down the assembly line.
Each C-17 military cargo jet has more than 1.4 million fasteners which, until now, had to be installed "wet" using a sealant that costs more to dispose of than purchase because of its hazardous waste condition. "The pre-coated fasteners improve the quality of work life for our mechanics," adds Nick Peralta, senior manager at McDonnell Douglas.
The fasteners also improve the quality of the product, according to Jose Jimenez, team leader in the Drivmatic area. "We get better squeeze on the fastener and avoid problems where the rivets don't fill the hole tightly. Also, if you have to remove a titanium pin, it won't seize up because there is more lubricity." Jimenez explains that the old wet sealant used to clog up the Drivmatic.
The patented technology, which uses an aluminum-pigmented resin with corrosion inhibitors, reduces the process variability factor in installing a C-17's 590,000 titanium pins and 733,000 rivets. And the sealant ensures corrosion protection at each hole.
"We expect a 1.1 million-hour savings in phase 2 of implementation," says Behnke. Phase 1, which began with aircraft P-33, and Phase 2 combined should save 2.3 million labor hours. Behnke expects other military and commercial programs will adopt the technology as well.
Self-tapping screws improve production, cut costs
Palm Coast, FL--When Pete Castellano joined ABB Ceag Power Supplies as principal mechanical design engineer, his primary objective was to create more cost-efficient designs. He quickly realized the process of fastening power supply parts offered such an opportunity.
ABB Ceag's power supply casting requires 50 fasteners to hold it together. Originally, the company used a nut in a three-step process--drilling, tapping, and fastening. Switching to Parker-Kalon(R) Swageform(R) thread-forming screws reduced costs significantly by combining the tapping and fastening steps into one procedure.
The Swageform screws have external threads that tap, or form, their own mating internal threads when driven into existing holes. The swaging of the screw thread does not remove material around the hole, but displaces it around the mating threads, making them stronger.
The result: the screws have a higher resistance to backout and vibration, and don't produce cutting chips of metal as they are driven into the casting.
"Our units are tested with high voltage to pass UL qualifications. If a metal chip has fallen into the unit, pc boards or semiconductors will burn and must be discarded. We can't tolerate a single metallic chip within the unit," explains Castellano. "We haven't had a problem since we started using Parker-Kalon fasteners," he adds.
The new fastening system has increased productivity, cut labor, enhanced quality, and cut costs on piece parts. The cost per hole on extrusions: five cents now, compared with 15 cents previously. For ABB Ceag, that adds up to a savings of $5.00 on every main power supply casting.
Fastener reduces cross threading
Dean Lamb, Mgr. of Mktg. Communications Camcar Textron; Rockford, IL
On the assembly line, cross threading can result in significant down time, poor productivity, scrap, and rework. Cross threading occurs when misalignment between the fastener and nut member due to off-center or off-angle driving causes a wedging action in the hole.
To help alleviate the problem, Camcar Textron has introduced the AcupointTM anti-cross-threading fastener. The Acupoint features a spherical point that enables the fastener to self-align from off-angle and off-center positions. The point design allows quick engagement into the hole, and thread engagement only when the fastener is properly aligned. When compared to other anti-cross-thread designs, the Acupoint has a shorter point length to minimize interference.
During lab testing under controlled conditions, the Acupoint showed a 97% starting rate at an off angle of 30 degrees. A machine screw showed only a 55% starting rate at a 7-degree off angle.
In the off-center position, the Acupoint design showed a good start 100% of the time at 2.40 mm off center, while a machine screw demonstrated a 73% starting rate at 2.40 mm.
The Acupoint fastener comes in M4, M6, and M8 sizes. Other sizes are currently under development.
For details contact Camcar Textron, 516 Eighteenth Ave., Rockford, IL 61104-5181; ph: (800) 544-6117; www.camcar.textron.com; FAX: (815) 961-5345
Standoffs thread ultra-thin sheets
New self-clinching threaded standoffs provide permanent threads in ultra-thin aluminum or steel sheets to enable stacking or spacing of pc boards and other components.
The PEM(R) Type TSOTM, TSOSTM, and TSOATM standoffs install in sheets as thin as 0.025 inch (0.63 mm) and deliver high push-out and torque-out resistances, says Michael Rossi, corporate communications supervisor at Penn Engineering.
Installation involves inserting the standoffs into punched or drilled holes and applying a squeezing force. The fasteners become a permanent part of the assembly, while the head remains flush with the mounting sheet.
Type TSOTM (steel), TSOSTM (stainless steel), and TSOATM (aluminum) fasteners come in both standard and metric sizes in varying lengths.
For more information contact Michael J. Rossi, Penn Engineering & Manufacturing, Box 1000, Danboro, PA 18916; ph: (800) 237-4736; FAX: (215) 766-0143; e-mail: [email protected]; visit http://www.pemnet.com
Adhesive withstands oil and contamination
Loctite(R) 243 single-component, removable, anaerobic, threadlocking adhesive stands up to oil and other contaminates. As a result, fasteners require no additional cleaning or preparation before the threadlocker is applied, says manufacturer Loctite Corp. (Rocky Hill, CT).
The adhesive cures without air when applied between close fitting metal parts such as nuts and bolts, while protecting fastener threads from rust and corrosion. Suited for threaded fasteners up to 3/4 inch (20 mm), the threadlocker works on stainless steel, plated finishes, and other substrates. Threaded fasteners treated with the adhesive can be disassembled using simple hand tools.
Loctite 243 is NSF/ANSI 61 certified for use in potable water systems, and can be applied manually or with semi- or fully automatic dispensing equipment. Packaging ranges from a 0.5-ml tube to a 1 liter bottle.
For more information contact Loctite Corp., 1001 Trout Brook Crossing, Rocky Hill, CT 06067; ph: (800) 323-5106 x67; FAX: (860) 571-5465.
How EWI does it
Most fillet-welding applications involve consumable electrode processes that use constant-voltage power supplies. The primary parameters of these processes include wire-feed speed, voltage or arc length, and travel speed. Current becomes a function of the wire-feed speed, type, diameter, and extension from contact tip.
The parameter development methodology in use at EWI yields the voltage as a function of wire-feed-speed curves for each process-consumable combination. Once this relationship is determined, a welding productivity window that relates heat input as a function of deposition rate is developed. The boundaries of the welding productivity window are established by bead shape geometry and weld pool stability criteria. The welding productivity window assesses both productivity and robustness.
Welding technology replaces aircraft rivets
Wichita, KS-based PACMIG Inc. has developed a new pressurized, air-cooled, metal inert gas (PAC-MIG) welding gun technology that may soon replace heavier rivet fasteners in commercial airframes. In preliminary, third-party fatigue tests, butt joint welds using the MIG technique were then shot-peened. The joints showed twice the fatigue life of comparable three-row, flush-riveted lap joints like those used by Boeing transports, says PACMIG President Joseph Cusick. The patented technology uses compressed air to cool the welding appliance and then vents it to the atmosphere. According to Cusick, PACMIG is lighter, simpler, and more economical to use than comparable rivet systems.
Additional details, contact PACMIG, 311 Laura, Wichita, KS 67211, ph: (316) 269-3040
Forum offers fastening solutions
Looking for a place where fastener manufacturers and distributors can gather with OEM engineers and purchasing agents to exchange information, go back to "school," and solve fastener application problems? The Fastening Design and Application Engineering Expo and Technical Conference is just the ticket, say its sponsors.
Taking place October 23-24, 1997 at the Novi Expo Center in Detroit, MI, the event features educational seminars, hands-on demonstrations, workshops, and discussion groups that will address questions and concerns in fastener application, design, and engineering. Participating companies will feature products for the aerospace, automotive, utilities, appliance, and shipbuilding industries, among others.
For more information on exhibiting or attending, contact FDAE, 5008-34 Pine Creek Dr., Westerville, OH 43081; ph: (614) 895-8348; FAX: (614) 895-3466; see http://www.bannister.com/fdae