Smoother, cleaner, quieter, longer

Feb. 25, 2004
How power transmission systems are becoming more compact, precise, efficient and maintenance-free

The unprecedented productivity of U.S. manufacturing workers is largely a product of automation, and supporting the myriad systems that energize it is not a trivial task.

"The technological trends we currently see impacting power transmission result from global competition and domestic economic forces," says Bob Summerlin, group vice president, sales and marketing, Motion Industries (http://www.motionindustries.com). "While the business press reports on migration of manufacturing offshore, we see U.S. plant facilities actively seeking significant solutions to improve production capabilities and reduce costs through industrial automation."

"Customers are making their decisions based on increased process reliability and uptime, lower cost per unit of production and improved asset utilization," says Bob Nemecek, director of marketing, Dodge products, Rockwell Automation (http://www.dodge-pt.com). "There's a huge focus on plant productivity there's not a customer I call on who doesn't know what one point of productivity means on the bottom line."

Take advantage of advances in component quality, power density and design to make your plant's power transmission systems more cost-effective and trouble-free.

Sensing smoothness

Figure 1: Twin City Fan's Brookings, S.D., facility performed vibration analysis tests on seven styles of bearings from a variety of manufacturers to find that concentric adapter-mounted ball and spherical roller bearings vibrated less that eccentric locking or set screw-mounted bearings.

Start with better metal

Operating environments directly affect the life and reliability of power transmission components. Factors such as inadequate lubrication, poor maintenance, excessive load, increased friction, vibration and debris can result in component failures from wear, fatigue, pitting, scuffing and bending. Advances in metal component compositions and surface treatments are making gears and bearings more tolerant of these hard facts of factory floor life.

For example, spherical roller bearings in the guide rolls of continuous casting machines operate under some of the most severe conditions imaginable: heavy load, ultra-low-speed rolling (only a few rotations per minute), and an environment of water and scale contamination. As a result, the bearings often suffer from uneven wear on their outer ring raceways, leading to cracks and flaking. Outer ring fracture and bearing failure has serious implications for continuous steel production.

"NSK has succeeded in developing a longer-life spherical roller bearing for use in the guide rolls of continuous casting machines," says Bob Highland, western regional sales manager, NSK (http://www.am.nsk.com). "The new Super Wear-Resistant (SWR) bearing has more than twice the life compared to conventional bearing types."

In another example, where paper-machine dryer cylinders are heated by steam injected through the bearing journals, thermal expansion of the hollow shafts would overstress and crack the inner bearing races. This problem was solved by using tougher steel for the races (NSK calls these its TL series bearings).

"Engineered surface technologies exist to improve the wear, fatigue and frictional performance of equipment including bearings, hydrostatics, engine components and gear systems," says Greg VanBuskirk, market development manager, The Timken Co. (http://www.timken.com). The company is able to use specialized vapor-deposited coatings and surface finishes that change the surface material, surface design or subsurface design of a component.

Depending on the application, these surface treatments can:

Maximize torque capacity.

Reduce frictional power losses.

Reduce component wear.

Increase debris resistance.

Address poor lubrication.

Minimize redesign costs.

For example, inadequate lubrication results in scoring and scuffing of tapered roller bearing roller ends and rib faces. "Timken has found that engineered surface tapered roller bearings survive these extreme operating conditions," VanBuskirk says. "This surface coating also combats problems caused by foreign material (bruising and abrasive wear), peeling, electric current (arc pitting or fluting), fatigue spalling and false brinelling."

In another example, treating a sun gear in a power train drive system increased the gear life "in excess of 300%," VanBuskirk says. "And independent tests have shown to increase the scuffing torque limit by as much as 70% and increase the pitting torque limit by as much as 33%."

The upshot is power train components are becoming stronger and more reliable than ever. "With carburized and ground gears, CNC machining and precision grinding, they last longer," says Ron Doll, marketing manager, Falk (http://www.falkcorp.com). "We just don't see replacement gear orders like we did years ago things just don't wear out."

Pack it in

Stronger, more precise gears and bearings, closer assembly tolerances and better lubricants are increasing power component ratings and efficiencies.

The result is smaller reducers and drives. "You can get more torque and horsepower from a smaller cube," Nemecek says.

"Weights and sizes are down to a third of what they were in the 1950s," Doll says. Higher load ratings with smaller gears and bearings also means vendors can cover more applications with fewer form factors. The resulting standard, modular packages save money, reduce lead times and improve parts availability.

Being smaller and lighter, they can be mounted directly on shafts or equipment. "Shaft or equipment-mounted drives require no foundation, couplings or alignment," Doll says. "They're more compact, which can lead to a smaller building that further reduces costs."

Higher power densities are not limited to gearboxes. For example, synchronous belt drives are also handling larger loads.

Ben Smith, application engineer, Gates (http://www.gates.com), says, "The current, second-generation curvilinear belts handle much higher loads, especially when made of strong materials like polyurethane reinforced by aramid fiber."

Compared to earlier synchronous belt drives, new narrower drives generate less overhung load, which can reduce shaft loads and increase bearing and gearbox life. "These belts can be about as narrow and sometimes narrower than roller chains with equivalent power ratings," Smith says.

More stainless and plastic

Food and specialty chemical plants have been doing a lot of investment in automation. Power transmission components in these facilities must meet requirements of regulatory agencies. "Efforts to avoid contamination and extend component life are leading to more use of stainless steel and non-metallics," Nemecek says. "Plastics continue to explode wherever speeds, loads and temperatures allow them."

"For food and specialty chemical applications, higher cleanliness and washdown requirements are driving demand for stainless steel sprockets and bushings," Smith says.

Exposed components from drives to bearing hangars and shaft couplings come under scrutiny. For example, at a typical food processor, washdown chemicals were rusting the coupling hubs to the shafts. The company changed these elements at least four times per year, taking at least five to six hours per pump. And rusty equipment makes it more difficult for a food plant to comply with U.S. Department of Agriculture (USDA) regulations.

The couplings were replaced with Lovejoy stainless steel hubs and six-pin elements and rings. The stainless steel hubs were less expensive than traditional stainless steel couplings. Easy, tool-free assembly eliminated the need to move the flanges for element replacement.

"The option of a stainless steel coupling helps these plants comply with USDA regulations," says Vince Baschoff, representative, Lovejoy (http://www.lovejoy.com). "It requires but a fraction of the previous time spent on maintenance."

Do less work

Better materials and surface treatments have not made it possible to ignore lubricants and seals yet.

Mark Hill, president, Companion Products (http://www.oilsafe.net), says, "It is well documented that lubricant contamination is a root cause of machine failure, and that reducing contamination can result in significant improvements in equipment reliability."

Gearbox designers are recognizing this and improving their products' defenses with better seals and more effective breathers.

"By eliminating outside contamination from the equation, gearbox reliability is greater, which translates into increased uptime for the end user," says Ralph Whitley, director of engineering, Boston Gear (http://www.bostongear.com). He says sealed-for-life gearboxes offer substantial maintenance cost reductions a typical plant with 100 gearboxes could save $40,000 per year.

Better materials, designs and sealing add up to lower maintenance requirements. Lubrication-free and permanently lubricated components need no oil or grease: along with lower downtime, the environmental costs of lubricant are reduced.

No-move designs allow wear components to be replaced without dismounting and realigning equipment. "It's expensive to do the realignment, so they're real cost-effective," Doll says.

Along with faster installation, improved mounting methods like concentric adapters instead of traditional keys and setscrews allow higher speeds with less vibration, which reduces stresses on other components (see Figure 1).

"Plants have fewer personnel and there are fewer engineers at the equipment manufacturers," Doll says. Many typical systems are now pre-engineered using pre-built components, he adds. "There's no design engineering cost or time delay, and the components are better integrated because they're standard. They can be available in two weeks at 20% lower cost. "We're supplying complete conveyor, mixer and mill drives we mount them on a baseplate and ship them."

You can increasingly draw on vendor expertise to get low-cost or free engineering. For example, "We are adding several new drive and control product lines as well as dedicated automation specialists," Summerlin says. "These specialists are skilled to assist with problem areas in the manufacturing process and to provide plants with machinery upgrades and/or retrofits to assist in plant automation."

Vendors that in the past may have concentrated on just making and shipping parts increasingly recognize they must do more to stand out and keep their customers thriving. Highland sums it up: "It's so much more than just the bearing."

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