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issue: March 2008 APPLIANCE Magazine

Assembly & Fastening
Lean and Flexible Assembly and Manufacturing

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by Leanna Skarnulis, Contributing Editor

Almost faster than you can say “changeover,” suppliers of assembly and fastening solutions for appliance OEMs find themselves responding to or anticipating another need.

Tiny electronic components in hearing aids and other medical devices can wreak havoc in a conveyor. Bosch Rexroth offers assembly systems that are “friendly” to fasteners and other small components.

As competitive pressures mount, OEMs look to suppliers as partners in improving product innovation, aesthetics, performance, manufacturing efficiencies, reduced work-in-process, lower material costs, and more.

Hungry for Lean

One trend that continues to loom larger than others is manufacturers’ appetite for lean. Suppliers are constantly challenged to help them cut waste.

In the quest for lean, OEMs are relying heavily on suppliers to provide a nearly completed subcomponent, says Derek Rathel, appliance segment manager, Tesa Tape Inc. (Charlotte, NC, U.S.). “This has increased intimacy between customer and supplier, helped to drive down costs due to leaner internal infrastructures and parts inventories, and has enabled OEMs to focus on streamlining production processes.”

Lean manufacturing is no longer limited to manual production systems. “While manual production systems may be the optimal assembly solution for some applications, other applications are better served with a mix of manual and automated systems, and still others may benefit most from a completely automated approach,” says Mark
Dinges, product manager, TS Conveyors, Bosch Rexroth Corp. (Hoffman Estates, IL, U.S.). “It’s important for manufacturers considering lean to approach the subject from the standpoint of reducing waste. Then, depending on a variety of production factors, such as takt time, cycle time, part size, and even labor costs, an automated assembly system may be a better solution than a manual production system.”

Dinges adds that keeping costs down is especially critical for OEMs struggling to keep their manufacturing in the United States. “Implementing lean production techniques is one way that these manufacturers can improve efficiencies, cut costs, reduce rework, and enhance safety.”

Rexroth offers white papers and guidebooks that describe how to get started with lean and how to decide whether to automate. “We’ve also launched a manual production systems product line that specifically helps with manual assembly situations,” says Dinges. “Manual production systems were designed from the ground up to fit into a lean strategy and can be easily combined with automated equipment where needed.”

Modularity, flexibility, and quick changeover time are important to OEMs. Assembly solutions from both Rexroth and Hess Industries (Niles, MI, U.S.) are said to meet these criteria.

“While various types of automation are available, nonsynchronous, pallet-based assembly conveyors represent one of the most flexible technologies,” says Dinges. “The Rexroth line of TS assembly conveyors is built from modular, bolt-together components and aluminum framing. This modular design allows for greater flexibility, which makes it easy to combine manual and automated workstations on the same assembly system, or to reconfigure or expand the system as assembly requirements change. Additional new developments, such as Rexroth’s Cartesian motion systems, also make it much faster and easier to specify and install multiaxis robotics systems.”

A new lean solution from Hess Industries is its Demand Flow sheet metal fabrication and assembly system. It is said to enable a manufacturer to replace 20 press-to-press stations with a line that fabricates multiple parts from a single coil with no delay between different parts.

For example, one line that Hess created produces 17 different sizes or configurations of furnace air-filter housings with changeover on-the-fly. It consists of a coil or flat-stock feeding station; a pierce, punch or notch station; a cut-to-length station; stations to bend, form, and fold; and an assembly station. The entire line is operated with one person at the beginning to feed stock and one at the end.

“We can transition from one part to the next without having to start another program,” says Tom Fruk, senior applications engineer. “It’s done on-the-fly. We have a control algorithm that blends different programs together so when the last feature on the outgoing part is produced, the first feature on the new part begins.”

Another advantage of the Demand Flow system is reduction of scrap, says Bill Williamson, business development manager for Hess Industries. “Often there’s no lost scrap on the sides or length-to-length. The only scrap is one inch at the very beginning of a coil and four or five feet at the end.

Reduction of work-in-process is essential for appliance manufacturers seeking to make their operations leaner. “Some facilities have giant storage racks to hold partially finished parts,” says Fruk. “The Demand Flow system allows you to batch exactly to what you need so you can tailor production runs to match the final assembly line where parts come off our system and go into final assembly.”

UV22 is a new Master Bond nanosilica-filled, one-component, UV-curable epoxy developed for coating, sealing, and encapsulation applications. It designed for superb abrasion resistance, excellent optical clarity, low shrinkage, and high physical strength properties. Temperature resistance can be further enhanced with postcuring. Adding heat (195°–257°F for 30 minutes) will give the material glass transition temperature of 275°F, far higher than traditional UV systems. The postcuring also effectively increased the material’s chemical resistance to solvents, acids, and bases.

Global Pressures

In addition to lean needs, global pressures due to the shifting of manufacturing centers are a key driver of change.

“We all know there is a manufacturing tsunami occurring in Asia, driving manufacturing out of North America and moving it east,” says Rick Sheffer, marketing, Hess Industries. “Everyone wants quality products at the lowest cost. China and India are filling this bill, and Eastern Europe and Russia are also gathering manufacturing steam.”

Increasingly, OEMs are adopting common technology and styling for products offered around the world. “These appliances have some specific size and feature requirements to the specific markets in a country, but the globalization is apparent,” says Sheffer. “As the utilization of design becomes more global, the utilization of manufacturing as well as equipment providers also becomes more global.”

A family of 17 different furnace filter housings were manufactured with changeover on-the-fly using the Demand Flow sheet-metal fabrication system from Hess Industries.

Suppliers’ Role in New Product Development

As the time-to-market window for new product development continues to shrink, more manufacturers are relying on the full turnkey services provided by a systems integrator, says Dinges. Using a system integrator rather than automating in-house can dramatically shorten the time it takes to implement an assembly system. “A system that used to be delivered in 11–12 months, for example, might now be delivered in six. The deployment of modular technologies helps here, too. But additionally, we’ve developed 3-D solid models for virtually any design software an integrator might use, as well as sophisticated design software to help streamline the upfront engineering effort. It requires a true partnership to get a new product manufactured and in the market fast, including the manufacturer, the assembly technology supplier, and the automation system integrator.”

Sheffer believes globalization and product innovation will drive North American OEMs toward Demand Flow manufacturing over the next three to five years. “They need to be first to market with superior products.”

Another emerging trend is shorter life cycles for appliances. “Back in the 1980s, we quoted equipment for a company whose product design had not changed in 30 years. You don’t see that today,” says Williamson. “With most appliances, five to seven years is tops, and with changing technology, it will get shorter. The impact on appliance makers is that whether they make refrigerators or stoves, even if their total annual volume doesn’t change, the number of different models they’ll have to sell to reach that volume will be greater.”

This need for versatility will go upstream to the equipment supplier, says Williamson. “Today’s refrigerator door not only comes in models that offer ice and water but also DVD players and TVs. The manufacturing equipment has to have features built in so it knows if the door will have an ice maker or a slot for a DVD player.”

A lesser trend is the emergence of regional preferences for appliances. “With increased competitive pressures from Asia and Europe, manufacturers may compete to offer appliances designed specifically to U.S. regional consumer preferences,” says Sheffer. “Consumers in California may prefer a different appliance look than consumers in New York or Florida. This market driver plays directly into Demand Flow sheet-metal fabrication and assembly. Manufacturers will be able to easily change over lines to make sheet-metal changes for regional product preferences.”

AKH (Indianapolis, IN, U.S.) and Flexible Automation (Burton, MI) teamed up to introduce the Robot-Mount AKH Fas-Ner system. The AKH system uses a unique, self-piercing fastener that mounts flush with the material being joined. The fastener, made of hardened aluminum or high-carbon steel, acts as its own punch, replacing spot welding or riveting joining methods. AKH has sold presses and custom automation for the joining system in the past, but developed the new advanced automation system with flexible automation to integrate into the manufacturing process and increase bottom-line efficiency.

Fastening Solutions

With OEMs needing increased production efficiencies and lower materials costs, sticking to fastening solutions like welding and rivets may not be the best way to go, say adhesives suppliers. “New adhesive products can easily replace traditional mechanical fasteners such as rivets and screws,” says Rathel of Tesa. “They’re costly, add weight to finished product, which in turn increases shipping costs, and require more time than permanent bonding adhesives to apply. Self-adhesive tapes can be applied much easier and faster.

“At Tesa we’ve seen a demand from OEMs for incorporating automated tape dispensers and applicators during in-line assembly. This type of dispensing system, coupled with long-length, spool-wound rolls of tape can reduce slowdowns during production processes.”

Appliance manufacturers continually strive to cut the costs of manufacturing processes and raw materials while producing high-performance, aesthetically attractive products. Cost-cutting measures include improving line speeds and throughput, reducing assembly time and labor costs, reducing rework, and cutting raw-material costs.

“Henkel is helping appliance manufacturers achieve these goals by developing innovative new adhesives and sealants,” says John Lafond, market development manager for Appliance and Electric Motors with Henkel Technologies. The company is a supplier for the commercial and consumer refrigeration, cooking, dishwashing, laundry, HVAC, and medical appliance industries.

“Our sales to the appliance market have been growing significantly as manufacturers switch from mechanical fasteners and welding to sealants. We have been successfully selling our Loctite branded epoxy, cyanoacrylate, as well as acrylic and anaerobic adhesives into a variety of bonding and sealing applications ranging from refrigerator and laundry doors to laundry consoles to refrigerator liner repair systems to gaskets for laundry drive systems. Yet the largest driver of our growth in 2007 has been our innovative two-part silicone adhesives.”

These rapid-curing adhesives, Loctite 5600 and Loctite 5604, are used in manufacturing glass stovetops. “Manufacturers used silicone in assembling glass stovetops in the past because of its high temperature resistance, flexibility, and environmental resistance,” says Lafond. “But silicone adhesives require a long cure time—from 8 to 24 hours—so large areas of the floor were set aside for racking and curing,” says Lafond. “Loctite 5600 has an open work time of 2 minutes and 5604, 4 minutes. Both 5600 and 5604 cure rapidly enough that stovetop assemblies can be moved to the next manufacturing operation in less than 10 minutes. Some manufacturers that are not that automated want a little more time to work the material, so we’re working on a slower-curing product.”

Lafond says manufacturers also need efficient delivery and dispensing systems to minimize waste, plus high-quality adhesives to reduce rework. “With these two-part silicones, we can dispense it very accurately, whether it’s a manual or fully automated robotic assembly process. Also, reducing work-in-process will often reduce rework because when you can assemble quickly, you’ll catch a problem quickly instead of having a floor full of failed product that needs to be reworked.”

The new adhesives are also said to meet OEMs’ high-performance requirements for tensile strength, shelf life, and resistance to chemicals, humidity, temperature extremes, and vibration. Lafond says there’s more innovation to come. While the main focus for silicone adhesives is currently cooking appliances, he anticipates there will be other applications as well. “The adhesives could be used in the drive system of washers and dryers that have motors that vibrate or in an HVAC unit that sits on a roof exposed to elements and temperature extremes.”

Adhesives play an indirect role in helping appliance OEMs reduce the cost of raw materials. “The high cost of Type 300 stainless steel is driving appliance manufacturers to turn to alternative steels that cannot be welded,” says Lafond. “Loctite-branded products allow for changes to lower-cost materials where welding or assembling with fasteners are not possible. Also, our products distribute loads evenly so the manufacturer can use thinner, lower-cost materials.”

Adhesives also contribute to the improved aesthetics of appliances, says Lafond. “One of the downfalls of fasteners is appearance. With adhesives there are no seams, weld discoloration, or bulky fasteners.” Lafond says Loctite products contribute to manufacturers’ needs for improved safety by eliminating hazardous assembly methods. “These methods involve heat or flame, such as welding or brazing, or high pressure or torque, such as riveting or installing screws. We’ve been successful at developing adhesives that are noncorrosive and nontoxic without offensive odors.”

Tesa takes a multifaceted approach to helping OEMs drive down costs. “First, we spend time on assembly lines and with staff engineers to understand the daily challenges facing appliance producers,” says Rathel. “Then we interface with industry suppliers to engage our products in application areas that enhance or speed the production process. For example, we work with plastic trim producers to provide them with a variety of tapes, particularly double-sided tapes, so that assemblers at OEMs can quickly and easily remove the tape liner and apply the trim to the final product.

“We are also continually reviewing our product mix to ensure we have tapes and systems for today and beyond.”

Investing for the Future

OEMs are demanding flexible assembly equipment that will adapt to future needs. Dinges calls this driver “future-proofing.”

“From subassemblies to final assemblies, appliance manufacturers continue to invest in flexible production systems. One of the primary goals of a flexible production system is to assemble multiple models or subcomponents on a single line. Manufacturers are achieving this through infrastructure upgrades, process improvements, and new technologies,” Dinges explains. “For example, workpiece pallets used on a nonsynchronous conveyor typically include an assembly fixture that allows different components to be assembled using one common fixture. When second- and third-generation appliance changes require an updated assembly process, usually a redesigned assembly fixture is all that’s required to adapt the line to the new process and save the cost of integrating a completely new line.”

The future of assembly and manufacturing will be even leaner, and ever more flexible, to meet the expectations of future appliance consumers.

Suppliers mentioned in this article:
tesa tape, inc.
Bosch Rexroth Corp.
AKH Fas-Ner Systems

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