smalley - Motion Control Tips

New Spirawave nested wave spring series from Smalley

January 8, 2019 By Lisa Eitel Leave a Comment

Smalley now offers a new nested Spirawave wave spring series. Smalley has been producing nested wave springs as customs for over 30 years, but this will mark the first standard series on the market.

These multiple turn, flat wire wave springs are coiled in parallel to produce two to three times as much force as traditional single-turn wave springs. Nested Spirawave springs can be used to replace stacks of single-turn springs, eliminating misalignment and inconsistent loading.

The sturdy, tangle-resistant design allows for simple, time saving automated handling. Reduced costs can be realized from the use of a single spring and a simplified assembly process.

“Introducing a standard line of nested springs gives customers the ability to streamline production while meeting their high force requirements,” says Dan Frank, Research and Development Engineer.

Standard Nested Spirawave springs are available from 0.500 to 4 in. or 16 to 3,000 mm in carbon and stainless steel. Stock parts are available for overnight shipping.

Nested Spirawave springs are specified for many applications including heavy duty bearing preload, connectors, valves, and seals. The increased forces produced make them suitable for industries that need precision wave springs with high loads.

If a standard nested spring doesn’t meet the application requirements, Smalley has a team of experienced engineers capable of designing a custom nested spring. Custom or standard, Smalley will get the right part, in the right material, with No Tooling Charges.

Request a copy of the brochure or a free Nested Spirawave Wave Spring sample at nestedsprings.com.

For more than 50 years, Smalley has been the leading manufacturer of retaining rings and wave springs for OEM engineers worldwide. As an ISO 9001 and ISO 14001 company, we deliver quality products certified to: IATF 16949, AS9100 and ISO 13485. Custom or standard, we are dedicated to delivering the right part, in the right material for application. For manufacturing news and product updates, visit smalley.com/blog.

Common challenges that wave springs address

August 13, 2018 By Lisa Eitel Leave a Comment

Updated November 2018 || Springs are flexible mechanical components to store and release energy or apply and release forces on machine axes. Wave springs combine flat (non-coiled) bow springs (as their waves) with traditional compression-spring coil geometry. For the design’s compactness (as a high force-to-work height ratio) and other benefits, some motion systems have migrated from traditional helical or coil springs to flat-wire wave springs.

Design engineers typically work with manufacturers to customize wave springs to specific operating conditions by material, thickness, number of turns, and other geometric features. That helps address or avoid the following spring-installation challenges.

Wave springs outperform other springs under the application of normal (non-twisting) forces. Data courtesy P. Ravinder Reddy and V. Mukesh Reddy

Column buckling in springs occurs with long free lengths and spring ends that can’t evenly distribute load around the spring circumference. Buckling mainly depends on geometry and not spring material properties. Traditional springs tend to buckle when deflection (for a set free length) is excessive. Such buckling is preventable by keeping the design to below critical deflection and length values. The former is the ratio of deflection to spring free length; critical length is the ratio of that length to the spring diameter. One rule of thumb for avoiding buckling in traditional springs is to keep free length to less than quadruple the spring diameter — and load to less than the product of spring rate, length, and buckling factor.

Wave-spring buckling factors vary greatly, but the value is nearly always higher than those of other springs. That means they readily hold their centered cylindrical shape and often self-locate into assembly bores — even operating reliably in machined assembly features held to relatively loose tolerances.

Spring surge is a potential concern in assemblies with a compression spring having one free end. Depending on the motion input, such springs can exhibit resonance that’s large enough to cause temporary loss of contact with the assembly housing — and damage surrounding machine elements. That’s an issue of highest concern if the spring material provides little damping and the spring operates on an axis that must make fast reciprocating strokes. Well-chosen wave-spring geometry and material can help avoid issues of spring surge and resonance excitation.

Mean, cycling, and localized stresses on the spring each load cycle (and the load cycle itself) dictate when spring fatigue failure could occur. For any spring design, more turns make for a longer MTBF … while longer springs generally have shorter MTBF. But no matter the variation, wave springs fatigue more slowly and have longer MTBF than traditional springs.

Springs under normal operation exhibit no permanent spring-rate or dimensional changes — called relaxation or set. But deflection under full load with stresses exceeding the spring material’s yield strength will induce permanent deformation that compromises the spring ability to deliver full design force or energy. This is often a concern in designs that must operate in extremely hot ambient conditions. Wave-spring deflection is about 25% lower than that exhibited by traditional springs. Wave springs are also more resistant to relaxation for comparable diameters, free lengths, and turns. One caveat: In designs necessitating fewer turns and shorter free lengths, sometimes traditional compression springs outperform wave springs by exhibiting less deformation.

Any spring under a twisting moment load exhibits shear stress and stores strain energy. Wave springs exhibit less strain energy than traditional spring variations (and lower equivalent stress values) so better withstand such loading.

Shown here are wave-spring application examples. From top to bottom, these include clutches, automotive vehicle mirrors, rolling doors, airbag inflators, water sprinklers, general airbag assemblies, night-vision lenses, and bayonet connectors. Image courtesy Rotor Clip Company Inc.

Wave spring basics video: Spring force, work height, materials, and installations

January 13, 2018 By Lisa Eitel Leave a Comment

Within mechanical designs, tension, compression, and torsion springs take numerous forms to store and release energy. A wave spring is a type of compression springs made of flat wire. They are called wave springs because they have multiple waves per turn. The flat wire, along with the multiple waves per turn, combine to create the same spring force at reduced work heights compared to round wire coil springs.

Recent technology innovations in manufacturing, have led to applications decreasing in size — so the need for more compact springs has grown. A wave spring’s reduced work height (compared to that of a traditional coil spring) lets engineers shrink the overall height of the spring cavity. This often translates to a smaller assembly and potential weight savings.

Wave springs are designed around a spring force and work height. These requirements are determined by the application. The spring can be configured to accommodate cycling or static operations. A valve is an example of a cycling application. The spring oscillates between two work heights to regulate the valve. A wave spring can also be used in a static application such as preloading a bearing. In the bearing example, the spring is compressed to a work height and remains at that height for the lifetime of the application. This reduces vibration and ultimately prolongs the life of the bearing.

A wave spring is available in an array of materials. The material is dictated by the application environment. When the spring is not exposed to corrosive elements, carbon steel is the standard material used.

Wave springs are available in a range of stainless steels if the spring is in a corrosive environment. For high temperatures environments, an exotic alloy wave spring may be required. Common exotic alloys include, Elgiloy, Hastiloy, and Inconel.

The versatility of the wave spring allows it to be used in a variety of industries — including oil and gas, automotive, medical, and aerospace. Wave springs are used across these industries because they can range in sizes from as small as 0.157 in. (or 4 mm) to 120 in. or 3,000 mm in diameter.

Because wave springs are produced from coiling, manufacturing a custom spring can be an economical solution. Often only a simple set up is required, available with no tooling, to produce a spring that meets unique application requirements.

PT essentials meet changing market demands

April 1, 2016 By Michelle DiFrangia Leave a Comment

Michelle DiFrangia • Assistant Editor

With three- or four-stage labyrinths and an internal V ring for additional sealing effect and efficient grease purging, the new SKF Taconite seal for split block bearing housings is made to provide protection in extremely contaminated and wet environments.

Power-transmission components must satisfy an ever-changing array of industrial design needs, but some trends dominate today’s shifting engineering landscape. These include migration to more customization, the use of new materials, and demand for longer life and durability from all motion components. Here are some related advances that industry professionals see in designs for compression and wave springs, chains, locking assemblies and shaft collars, and seals.

Applications drive new compression and wave spring uses
The need for miniaturized designs continues to drive changes in compression and wave springs. Perhaps the biggest instigator of this trend is the medical industry. “As the population is aging, there’s been expansion of the medical-device industry and corresponding increased use of compression springs,” said Sanjeev Rivera, VP of sales and engineering at Lee Spring. “In particular, a lot of research and development has gone into creating disposable medical technologies.”

In fact, medical applications such as implantable devices or surgical instruments always benefit from being smaller, agreed Ben Moskalik, senior research and development engineer, Smalley Steel Ring Co.

Implant devices are revolutionizing the way medicine is being practiced, said Rivera. “Some operations that would be inpatient procedures, with the help of our springs and product innovation, can now be performed as outpatient procedures.”

The smaller the components, the smaller the tool, the easier it is to handle—a power hand tool, like a cordless drill, for example. “The ability to manufacture smaller diameter springs is the forefront of these technological advances,” added Moskalik. In addition, wave springs in these compact designs offer a slight advantage over coil compression springs. That’s because they get the same spring rate and deflection in about half the length, according to Moskalik.

A wave spring is simply an alternate form of a conventional helical wind spring that lets designers fit comparable loads in tighter spaces. “As more engineers become aware of this benefit, we’ve seen much greater wave spring use in both existing and newly developed applications,” said Rivera.

Rexnord has had innovative breakthroughs in lubrication and corrosion resistance that contribute to longer life and reduced maintenance for their roller chains in automotive material handling markets.

2016 trends in chains
When it comes to chains, it’s all about longer life, durability and lubrication. “Common in material handling, product transfer and power transmission functions, base chain product as a whole has remained relatively stable,” said Jon Utz, engineering manager, Rexnord. “But there is consistent effort to improve reliability, productivity and product lead times.”

One improvement leading to longer life is a trend toward lubrication-free or self-lubricating chain. Lambda self-lubricating chain from U.S. Tsubaki features hardened self-lube bushings, which are helpful in applications where keeping chain lubricated is difficult or impossible. Consider this application story: A food manufacturer using an O-ring chain was experiencing premature wear. U.S. Tsubaki engineers determined that the O-rings were drying out and failing because they weren’t being properly lubricated. As a result, the chain was lasting about six months shorter than expected—causing unexpected downtime and maintenance, as well as increased costs and lost production. So, the engineering team recommended lube-free Lambda chain as a solution.

“Lambda chain combines oil-impregnated sintered bushings and coated pins for long-term internal lubrication,” explained Michael Hogan, senior roller design and application engineer. Solid rollers engage cleanly with sprockets, creating smooth articulation, recuing chain pull, and lengthening system life. “As a result of switching to the Lambda chain, the customer increased their chain life leading to a significant decline in unexpected downtime,” Hogan said.

Durability problems can be solved with alternative materials, coatings and platings. “Many challenges associated with difficult conditions, often as a result of controlling pollution and a desire for improved environmental protection in applications, can create harsh environments for chains,” said Utz. “Consequently, these environments require continual advances, such as unique product designs and coating technology.”

Engineers should also consider specialized chain when standard product wears out quickly and there are significant maintenance costs involved, according to Utz.

Titan Chain from U.S. Tsubaki is a specialty carbon steel chain specifically designed for difficult environments like the kind Utz described. “The chain has a hard chrome-coated pin plus zinc-coated pin plates,” explained Hogan. “This style of chain has been particularly effective in extending life in the forestry products industry where heavy debris, lack of adequate lubrication and high-speed orientation are prevalent.”

In addition, the company’s new Performax bushing and ring coined connection links are increasing the life of standard chains. The ring coined connection links have a fatigue strength equaling that of a riveted chain link, thus eliminating what was once the weakest link, said Hogan.

Locking devices and shaft collars
Machinery manufacturing and industrial automation are two of the biggest drivers in the development of new keyless locking devices. “The trends that we are seeing have more to do with reductions in assembly and maintenance,” said Jeremy Bigler, product manager, Fenner Drives. “Over the last decade, there’s been stronger focus on providing keyless locking device solutions to meet the customer’s specifications.”

B-LOC Compression Hubs differ from other keyless locking devices in how they engage the mounted component. Rather than creating a radial force on the mounted component, the outer tapered rings are drawn together to generate an axial clamping force.

For instance, Fenner Drives recently had a customer that used B-LOC compression hubs on a conveyor that manipulates large panels. The application required several large rotating discs to mount to a line shaft. “The B-LOC Hub let engineers simplify the design by eliminating the need for a welded hub in the large discs,” said Bigler. “They also reduced material and labor costs by eliminating the keyed connection on the line shaft. Prior to the development of B-LOC compression hubs, the customer had to weld in a hub and purchase a standard locking device.”

In fact, engineers at Fenner Drives have developed three new keyless locking devices in the last couple of years:

B-LOC compression hubs let customers mount thin components such as plate sprockets to a shaft without a hub
B-LOC Speed locking devices deliver the same performance of popular series and sizes, but install 50% faster
Trantorque Micro is for servo and stepper-motor applications and features the lowest-profile keyless locking device on the market.

Andrew Brown, president of Whittet-Higgins, also sees a trend toward custom products. “The use of high-speed, super precision, computer-controlled and robotic-fed lathes and machining centers lets us competitively manufacture smaller lot sizes of unique and more complicated parts,” he said.

Brown also sees a growing trend of locking devices being used in applications with gyroscopic stabilization systems.

Shaft collars are beginning to make their way into the medical market with advances in shaft collar technology benefiting robotic surgery designs.

“While cutting-edge technologies enable these designs, the requirement for proven basic mechanical designs and components in these innovations remains,” said Bill Hewitson, VP of operations at Ruland. “Traditional mechanical components, such as shaft collars, can provide structural support, adjustments and mechanical stops. New materials now being used in shaft collars—316 stainless steel, titanium, advanced plastics—offer increased flexibility for engineers designing robotic surgical equipment, for example.”

These are clamp-style shaft collars made by Ruland Manufacturing for solid holding. Suitable for medical equipment, the collars can guide, space, stop and align. Face-to-bore perpendicularity is a TIR less than or equal to 0.002 in., critical when the collar serves as a load-bearing face or aligns gears or bearings.

Engineers traditionally use shaft collars as stops or locators, but are beginning to use them more for mounting components to shafts, according to Arthur Stafford, president and senior engineer, Stafford Manufacturing. “The addition of mounting flats and flanges allow for a single part rather than needing to weld or otherwise connect to separate parts,” he said.

Consider another application, in which a company building astrophysics and meteorology equipment uses a Stafford Accu-Flange Mounting collar to connect hatch arms to open and the close covers on infrared sky imaging cameras. “The flange configuration let them use an off-the-shelf product, saving them development time and cost,” Arthur Stafford said.

In fact, Stafford Manufacturing’s latest introduction, the 3D Freedom series, features one-piece, two-piece and hinged-collar masters, machined in conventional materials and designed to mate with custom printed bushings, to let users immediately create hybrid collars for myriad applications, explained Arthur Stafford.

In addition, recently developed quick-release type collars allow rapid prototyping, offer convenience and save valuable setup time.

New innovations in seals
Every industry presents unique design challenges for seals. “Engineers from these industries are always looking for improvements and pushing the limits for seals,” said John Tranquili, materials manager for Apple Rubber.

This cutaway shows a Turcon M12 seal with PTFE based material, developed for use with environmentally friendly lubricants for effective friction characteristics and extended life. Image courtesy Trelleborg Sealing Solutions

Take, for instance, the aerospace industry, which is moving away from chrome plating. “Our dynamic seals must now function effectively on new surfaces, such as ceramic or laser-clad,” said Colin Macqueen, director of technology, Trelleborg Sealing Solutions. The company’s Turcon VL seal is specifically designed for a small groove, making it a popular choice for aerospace applications.

In motion designs driven by fluid power, zinc-free hydraulic oils have caused unexpected surface damage when paired with traditional sealing materials, said Macqueen. To combat this, Trelleborg now offers Turcon M12, a PTFE-based material. “Turcon M12 was designed specifically for these environmentally friendly lubricants—for effective friction characteristics and extended life,” he said.

Reducing friction has always been top priority. Here, rubber-seal improvements have helped most over the past decade. “Adding new filler systems in rubber compounds has helped lower coefficients of friction,” said Tranquili. “Engineered texturing of the mold surface has also reduced the many seals’ working surface area to reduce friction. New coatings that permanently bond to the rubber compounds have greatly reduced friction as well.”

In addition, changes in environmental compliance and new regulations have spurred advances in rubber polymers themselves. For example, HNBR polymers outperform standard Nitrile compounds for ozone and weather resistance, and new grades of FKM are more resistant to steam used to clean piping in the food and pharmaceutical industries, said Tranquili. “These new materials have much better chemical, heat and compression resistance. This allows for less change out or downtime.”

“On the production side,” he continued, “new injection molding press designs give better control for higher precision parts. New mold-making equipment yields better surface finishes and higher cutting tolerances. This gives design engineers less tolerance stack up for assemblies, thus giving less chance of compression issues on the seal resulting in leaks.”

“Micro seals are becoming more of the norm than years past,” said Apple Rubber’s John Tranquili. “Much of our seals that are less than 1 mm require more attention to detail when building molds or processing parts.”

Today’s electric-motor-driven applications also need to last longer and drive the lowest possible torque. Here, seals can reduce the amount of power wasted to overcome system friction. “Traditionally, these applications use standard catalog products and materials,” said Bryan Uncapher, business development manager at SKF. “These trends are requiring us to borrow advanced materials from automotive for industrial applications. Furthermore, we are using design simulation and testing to further optimize sealing lips.”

SKF also sees success in implementing new sealing systems in steel-mill applications previously viewed as a commodity and routine maintenance. “Instead of fixing the problem, one customer focused on cost acquisition instead of cost of operation,” said Uncapher. “Our combination of new seals, different bearings, changes to lubrication intervals, and validation with sensors creates a solution that delivers an ROI of more than 200% in certain circumstances and applications.”

Lee Spring
leespring.com

Smalley Steel Ring Co.
smalley.com

Rexnord
rexnord.com

U.S. Tsubaki
ustsubaki.com

Fenner Drives
fennerdrives.com

Whittet-Higgins
whittet-higgins.com

Ruland
ruland.com

Stafford Manufacturing
staffordmfg.com

Apple Rubber
applerubber.com

SKF
skf.com

Trelleborg Sealing Solutions
tss.trelleborg.com