Plastics welding technology joins 'world-class' manufacturing.

Latest products show that computer controls and SPC are no strangers to plastics welding today, which is increasingly seen in the context of integrated systems rather than stand-alone operations.

Plastics welding technology is assuming its place in the realm of world-class manufacturing, as more processors extend their reach into assembly operations, which are deemed a necessary requirement for world-class status.

The essential trends driving plastics welding technology include: expanded use of microprocessor controls and software systems, which enable processors to document statistical process control (SPC) data, as well as monitor part and process quality; greater expectation of systems integration help from suppliers, linking welders with upstream and downstream operations; and more emphasis on part and tool design to better exploit "design-for-assembly" capabilities of various welding methods.

This article will examine these trends and how they are reflected in the newest equipment on the market.

'WORLD-CLASS' WELDING

The various methods of welding plastic components all represent value-added assembly procedures for processors, one of the wider range of services now expected of those seeking world-class manufacturing status and participation in strategic partnerships with customers and suppliers. Successful utilization of new technologies to implement welding/assembly methods and document quality provide a competitive advantage to processors.

That is not to say that every user of plastics welding equipment has high-tech needs; many don't and prefer to stick with simpler equipment. But automation, system integration, computer-numerical-controls (CNC), and advanced software for plastics welding appear to be inevitable trends among manufacturers who intend to keep pace with the accelerating demands of global competition and world-class quality.

Full CNC for plastics welders was first introduced around 1985; but even today it's not for everybody, says Dave Quebbemann, sales manager for Herrmann Ultrasonics. "Many smaller companies aren't interested in CNC technology. But those that want it are interested in producing parts that meet world-class standards; they seek contracts with secondary operations as a value-added advantage. They see the payoff in lower reject rates and higher quality. We're seeing more interest in CNC, where quality comes from process control over welding variables." Quebbemann notes CNC welding enjoys wider utilization in Europe, while the U.S., thus far, is somewhat behind the curve.

Besides providing the ability to gather and document SPC data, now considered a de facto requirement for markets such as automotive, medical and electronics equipment, microprocessor control of welding also allows processors to automate their operations, reduce setup time and develop a consistent template of work procedures over a wide stable of equipment and operators. Several welding equipment suppliers in recent years have been offering "multiplexer" technology: computer controls and software that provide the ability to simultaneously control numerous welding stations.

"Processors are looking for greater service and support behind the more sophisticated welding technology we offer," according to Bill Lynch, v.p. of sales and marketing for Dukane Corp. Lynch estimates that more than half of his firm's welding equipment sales since 1986 have included microprocessor controls. "Custom molders are becoming more diversified and include welding and assembly in their operations," he says.

Janet Devine, president of Sonobond Ultrasonics, adds that "processors must invest to get world-class quality into their operations. Quality requirements are stringent for certain markets. Today we find there is a much higher percentage of our customers now demanding microprocessor controls--something that was once considered an expensive option."

PROCESS CONTROLS TAKE OVER

For ultrasonic welding, virtually every process parameter now is subject to microprocessor control. This includes part weld time or duration, peak-to-peak amplitude, voltage and pressure.

Typically, the builders of welding equipment also supply their own custom computer hardware, architecture and software controls. Walter J. Hatcher, national sales and technical services manager for Sonics & Materials, says the welding process is highly specialized, and doesn't lend itself to integration with off-the-shelf computers or software for control purposes.

Process-control data is provided via digital monitors and printers or CRT screens. SPC data, gathered from the microprocessor, can verify process and part quality through a variety of measures, such as part residence or duration time, depth of melt conditions, finished assembly height, and overall wattage transmitted to a given part.

Of all the process variables in ultrasonic welding, pressure (lb of force a horn applies to a part) is the most difficult to control. Traditionally, pressure was monitored via an air-pressure regulator. However, newer, more accurate pressure measurement technologies have been developed in recent years, such as piezoelectric transducers.

Hatcher says welding equipment suppliers also continue to build process-control intelligence capabilities into their basic microprocessor package, such as Sonics & Materials' calibration pulse control, which separates idling losses from actual measured energy delivered to the part.

SYSTEM INTEGRATION: A 'MUST'

Integration of complementary, manufacturing technologies such as part fixturing and tooling, retrieval and management of SPC data, and automated material handling will all play a more important role for processors investing in welding technology in the coming years. As integrated welding/assembly systems become more sophisticated, processors demand greater support and service from equipment suppliers.

Ken McClelland, an executive with ToolTex Inc., a system integrator for custom automation equipment and a distributor for Sonics & Materials, says there is a growing need for equipment manufacturers to provide services to processors such as computer/software consulting, part design to better accommodate welding, and customized welding horns and tooling fixtures. He says plastics processors will probably base their capital-investment decisions for welding and assembly technology in coming years on whether a potential supplier can provide turnkey operations and offer full support as a system integrator--the ability to harmonize the various components of a manufacturing system.

'D-F-A' TAKES HOLD

Another trend is to approach front-end design of plastic parts with an eye to best utilizing the various welding technologies. "Design-for-assembly" is the new catch phrase for engineering the part in the early concept phase so as to maximize productivity over the multiple steps of producing a finished assembly.

The key design consideration to accommodate plastic welding is the joint configuration and joint-line interface of parts, according to equipment builders. Another important design consideration is incorporating joint flash traps to manage excess resin displaced by the welding process, particularly with ultrasonics.

WHAT'S NEW IN ULTRASONICS

Sonics & Materials this month will unveil its new multiplexer ultrasonic welding control unit at the National Design and Engineering Show in Chicago. The multiplexer can control up to 16 ultrasonic welding stations from a single central location. It can monitor various functions such as start/stop, calibration pulse, amplitude control, welding time and speed. The parameters can be individually adjusted for each welder by a single PC operator.

The company also recently introduced its new 40-kHz Slimline Actuator ultrasonic welding system at K'92 in Germany. Sonics and Materials says the welder was designed to join small precision parts in automated systems where space limitations are critical.

The snap-in converter, booster and horn assembly all ride on a precision bearing system. Overall stroke length is 3 in. Like other Sonics & Materials welders, the Slimline Actuator is available in microprocessor controlled or digitally timed versions, with computer interfaces that allow for SPC and on-line quality assurance.

Dukane Corp. will unveil a new 200-watt power supply for its 40-kHz ultrasonic welder before the end of the second quarter, according to Bill Lynch, v.p. of sales and marketing. The firm currently offers 350- and 700-w models. Also slated for introduction this year is a new mobile ultrasonic workstation.

Another new development, introduced by Dukane late last year, is version 3.0 software for its Ultra-Com microprocessor controls, which offers bidirectional communication, advanced graphics, programmed sequencing of welding options, and standard SPC interface capabilities.

The company also recently introduced a multiplexer that controls up to eight ultrasonic devices (see Pt, Aug. '91, p. 94). The multiplexer incorporates an SPC software package, interfaces with microprocessor controllers, and is priced between $995 and $1595.

Mecasonic, div. of Forward Technology Industries Inc., is introducing its new Omega S ultrasonic welders. These low-cost models offer frequencies of 20 and 30 kHz with three choices (1000, 1500, and 2000 w) of power supplies.

Two methods of welding are possible with the Omega S: constant time or constant level. Either the welder supplies ultrasonic energy for a precise time period during each weld, or the weld head moves to preset levels. Three digital timers control emission time, length and cooling cycle, while an internal cycle counter can be used to monitor production rates.

Herrmann Ultrasonics introduced late last year its "Active Control" series of Dialog ultrasonic welders, enhancing an existing product line (seee PT, Dec. '92, p. 71). The new series allows programming of amplitude from 70% to 100%. Unlike conventional generators, the Active Control generator series provides constant-amplitude output regardless of voltage variation (from 190 to 240 v), the company says. The generator has a self-tuning range of |+ or -~500 Hz. A high-power 4000-w generator also is available.

Recent improvements to the head of the press virtually eliminate deflection during welding, Herrmann says. The air cylinder has been placed in direct alignment with the welding horn, and ball bearings have replaced roller bearings in the machine column, for greater accuracy and repeatability.

Sonobond Ultrasonics has introduced the SureWeld 70 ultrasonic welder, now available with microprocessor controls. The unit features a 70-kHz, low-power design that allows it to cut and bond smaller, more precision parts, films and fabrics. The SureWeld 70 features electropneumatic triggering and pneumatically actuated, 1/4-in stroke.

Branson Ultrasonics Corp. recently introduced two new 2000-w, 20-kHz power supplies for its 900 series of ultrasonic welders. Known as the 920MA and 920BA power supplies, they provide electronic amplitude control, which allows rapid amplitude changes during the weld. The new power supplies also provide fully automatic tuning and store horn frequency at the end of each weld. The company also recently unveiled a new ultrasonic fabric-sealing system known as the FS-90 (PT, Aug. '92, p. 32).

Applied Ultrasonics Inc., introduced last fall the newest versions of its Hydrosnubber mechanical damping control device, a line of accessories designed for use with ultrasonic welders to permit accurately controlled part contact speed and improved actuator stroke settings. The Hydrosnubber HS4 and HS4W, for Branson IW Series welders ($625 and $675 respectively), control the contact rate during welding without restricting down speed, thus preventing cracked parts and incompletely staked heads. Micrometer-type stroke adjustment in 0.001-in. increments helps users obtain repeatable stroke lengths. Additional models are available for retrofitting to most Branson models, while custom models can be designed for Sonics & Materials and Dukane ultrasonic welders.

The latest from Mastersonics is the ability to integrate its 50-kHz Marksman 50 Thruster ultrasonic unit into an automated system, incorporating the thruster design concept as part of a robotic end-of-arm tooling, while providing a concentrated 50-kHz frequency range. The thruster can be mounted in a horizontal configuration.

GOOD VIBRATIONS 

Although ultrasonic and thermal techniques account for the preponderance of welding applications, industry sources believe vibration technology represents the new high-growth segment of the plastics welding sector.

Forward Technology Industries, recently introduced the LVW-2040 vibration welder, which can bond irregularly shaped parts up to 20 x 40 in. size. The unit also can accommodate multicavity tooling for simultaneous welding of several smaller parts. The machine is available in two frequencies: 100 and 200 Hz.

LVW-2040 employs horizontal vibratory movement under pressure to bond parts. Its computer controls include a multiple weld-pressure system that allows eight adjustable welding pressures during the weld cycle. Other features include a maintenance-free electromagnetic drive system and adjustable amplitude control.

Branson Ultrasonics is coming out with a new "mini-welder" to its 90 Series vibration welders, which features a "footprint" of about 9 sq ft. The company also added a Model VW/2 to the 90 Series. It's designed to weld large and irregularly shaped parts up to 16 x 24 in. The unit features an Allen-Bradley SLC 500 programmable controller and 5-hp, solid-state power supply with adjustable frequency (240 Hz).

Branson Ultrasonics last year acquired Vinton Inc., a producer of vibration, hot-plate and orbital welding devices based in Henrietta, N.Y. (PT, June '92, p. 87). Vinton had introduced a novel friction-welding process, known as orbital welding, at the NPE '91 show in Chicago (PT, Aug. '91, p. 93). However, Sylvio J. Mainolfi, Branson's director of marketing for non-ultrasonic welders, says Branson now has redesigned the OmniWeld orbital welding system, which is now known as the (Constant Velocity) CV-12. The new unit, introduced at the Plastics USA show in Chicago last October, features full microprocessor control and ability to download SPC data.

Mainolfi says that while ultrasonic welding equipment is more widespread and better suited to welding amorphous resins, welding technologies such as vibration, hot-plate and infrared can offer advantages for crystalline polymers.

TURNING ON THE HEAT

Extrusion Services Inc., recently unveiled its Thermal Plastic Welder Model 7C, which employs radiant heat and pressure to join parts, requiring no welding rod or flux. The unit features a General Electric PLC and all solid-state contactors, unlike many welders that still use relay contacts and manual switches and timers. Model 7C has adjustable temperatures up to 600 F, weld area up to 2 in. wide and 1 in. high, and weld angles to 45|degrees~.

The unit's price ranges from $11,000 to $14,000, plus mold tooling. Along with specialized tooling, Extrusion Services also provides dedicated, automated turnkey welding and assembly systems.

Engineered Inserts & Systems Inc., recently debuted its PHS-4000 pneumatic system for heat welding and staking. Applications include heat staking, heat forming, spot welding, embossing, and multiple staking and insertion. The unit is priced around $6000.

Solid-state controls feature a digital LED readout of setpoint and process conditions, PID temperature controller with auto-tune capabilities, and |+ or -~3% accuracy over an operating range up to 1500 F. Welding can be designed for semi- or fully automatic operation.

The press assembly has a 3.5-in. steel mounting column attached to a cast aluminum flange and base, and a front panel that contains air gauge, regulator and flow controls. In addition, all heater/thermocouple assemblies are made with quick disconnects.

Along with the PHS-4000, Engineered Inserts later this year will introduce its new ET-1000 welder, priced at about $4000.

Drader Manufacturing Industries Ltd., recently announced it was developing a new process for welding UHMW-PE (PT, Dec. '92, p. 13). Drader's Injectiweld handheld welding gun continuously feeds and melts a plastic rod, then extrudes it under pressure into the weld zone. The substrate surface in the weld area also is melted by the hot tip of the gun. A Drader spokesman says the company is now test marketing prototypes, which include a hot-air preheater for welding UHMW-PE.

Seelye Inc. recently introduced three models in its Superwelder series of portable, hand-held thermoplastic thermal welders. The three models, priced between $357 and $700, feature adjustable temperature control from 400 to 900 F.

Seelye, Vertrod Corp., and Laramy Products Co. all offer a full line of heat-sealing equipment and thermoplastic welding torches. This field of welding is described as a mature technology, subject to periodic upgrading of existing product lines, rather than major new introductions.

FOCUSED INFRARED BOWS IN

Branson first introduced its novel "focused-infrared" welding technology at NPE '91 in Chicago (PT, Aug. '91, p. 94). This non-contact fusion bonding technique currently is in the semi-commercial phase, with several custom production sites in operation. Branson expects to introduce a full standard commercial line later this year, with base pricing (not including tooling or fixtures) pegged at around $60,000.

The process makes use of reciprocating, focused infrared heat reflected from a single quartz lamp, and can achieve melt temperatures up to 1500 F. Welding is accomplished by scanning a concentrated beam of infrared thermal radiation over the surfaces of two parts to be welded, raising the material temperature to the melting point; and then the mating parts are clamped together.

Branson says the temperature and intensity of the beam can be precisely controlled during the welding cycle. Also, the energy focused on two mating parts can be controlled independently, an advantage in joining thick and thin parts or ones of unlike materials with different melt temperatures.

ELECTROMAGNETIC INDUCTION 

Emabond Systems is introducing a new turnkey system designed for welding three-dimensional nylon and nylon-alloy parts, utilizing its Emaweld induction-heating technology. The new 5-kw system is said to represent an advance in part design, tooling, and equipment technology for welding nylon parts. One of the first customers for this system will use it to weld glass-filled nylon auto air-intake components.

The company offers two basic product lines: an entry-level, 2-kw system priced between $35,000 and $45,000; and a 5-kw system designed for higher volumes and larger parts, priced between $65,000 to $85,000. Prices include tooling. The welding systems come in semi- to fully automated configurations.

RF AND LASER WELDING NEWS

High Frequency Technology Co. is introducing the Series HFT RF high-frequency welder. Designed for welding and sealing PVC and urethane elastomers, the model's output ranges from 1 to 30 kw. Available options include a complete, integrated materials-handling system, including shuttle feed tables, rotary indexing turntables, robotic pick-and-place feeders, and the new HFT/630 programmable roll-feed indexer.

The Series HFT has such easy-maintenance features as 100% duty-cycle ratings, plug-in timer modules, and washable aluminum air filters. The equipment is said to be competitively priced and configured to suit specialized customer requirements.

Plastics USA saw the North American debut of high-frequency welders from Eurotron srl of Italy, represented here by Mopoll Inc. (PT, Dec. '92, p. 59). Mopoll president Franco Canova says Eurotron's welders are fully screened to protect workers against RF radiation. Such screening reportedly will soon become an OSHA requirement.

Coherent General Inc. recently introduced its new "Diamond" Sealed C|O.sub.2~ laser welder, which the company says represents a marked improvement over existing laser systems. The output beam of the Diamond laser beam can be focused up to four times smaller and sharper than other models, so materials can be welded or cut with less power while producing a smaller heat-affected zone.

The sharper focus vaporizes less material, reducing the amount of exhaust gases created, according to the company. The Diamond laser also generates "square-wave," pulsed frequencies up to 10 kHz; the pulse wave shape reportedly reduces wasted power during welding and matches the output of larger machines.