Mechanical PT - Motion Control Tips

Advanced manufacturing and materials have made an highly efficient traction drive possible

September 14, 2018 By Lisa Eitel Leave a Comment

Rolling Motion Industries (RMI) has released two high-efficiency traction drives — the MAR-17-1-2.1 Traction Drive and the MAR-23-1-2.1 Traction Drive. These are 1-Way traction drives with only six moving parts and use an engineered traction fluid with a coefficient of friction of just 0.1 to 0.12. These traction drives typically last three times longer than conventional gearboxes and with no metal to metal contact these high efficiency drives generate up to 72% less heat after 24 hours of continuous operation, Additionally they create up to 38% lower dB at 3000 rpm (less than a home refrigerator) than conventional gearboxes. Even though there’s no metal to metal contact there’s no slippage or lost motion between the input and output shafts.

The MAR17-1-2.1 Traction Drive is designed for speeds to 3,600 rpm with 10 to 20 in/lb of torque, and the MAR-23-1-2.1 Traction Drive is rated for 3,600 rpm with 20 to 30 in/lb of torque. Operating at temperatures that are lower than a motor’s, with low vibration, and no torque losses from 10 to 3,000 rpm, these traction drives permit a motor to operate at peak efficiency. Applications for these 1-Way traction drives which can operate in explosive environments (ie. zone 1 and 21) include: Pumps, blowers, fans, turbo and super chargers, conveyers, HVAC systems, medical applications, and other power transmission and motion applications.

These revolutionary drives are available with an optional overriding clutch. Incorporating standard NEMA mounting dimensions, these drives can be easily integrated into new and existing applications.

In 1993 John Pawloski and his brother Ray took over the family business, Jewelers Machinist Co. They realized they needed to switch from outdated conventional thread grinders to CNC thread grinders. As a result, Jewelers Machinist Co is a source of some of the most complex thread grinding in the industry. The concept for the RMI traction drive came from John in 2007. Working in that high precision industry aided John in the development of the RMI Traction Drive.

In the years that followed, the design of the individual components and formula of the engineered traction fluid were finalized, testing was completed, a patent granted, and production begun. The RMI Traction Drive is one of the most efficient ways to transmit power from one point to another. Using rolling motion, RMI is able to transfer power at various ratios with minimal energy loss. Tested against V-belt, direct drive, chain, and gearbox setups, RMI Traction Drives offer energy saving benefits through true efficiency rating percentages up to 98%. The high efficiency of the traction drive allows electric motors to run at their peak efficiency ranges.

There are many applications where it can be used from automotive to industrial to medical. The RMI traction drive can be used in the electric vehicle market and precision applications. Offering benefits such as low backlash and no back driving, it set a new standard for high efficiency.

For more information, call (860)846-0530, email info@RMIDrive.com, or visit RMIDrive.com.

Galaxie Gearbox from WITTENSTEIN nominated as finalist for Germany’s Deutscher Zukunftspreis 2018

September 13, 2018 By Miles Budimir Leave a Comment

WITTENSTEIN’s Galaxie gearbox has been chosen as a finalist for the 2018 Federal President’s Award for Innovation in Science and Technology, recognized as “A radically new gearbox class – productivity leaps in the engineering industry”.

The jury for the Deutscher Zukunftspreis 2018 announced the three finalists for this year’s award. Galaxie inventors Dr. Manfred Wittenstein (Chairman of the Supervisory Board) and Thomas Bayer (Manager Innovation Lab) attended the ceremony and were officially recognized as part of the Deutscher Zukunftspreis “Circle of Excellence”.

The team of inventors nominated for the Deutscher Zukunftspreis 2018 (from left to right): Thomas Bayer (Manager Innovation Lab at WITTENSTEIN SE) and Dr. Manfred Wittenstein (Chairman of the Supervisory Board of WITTENSTEIN SE).

The new gearbox class has already won two prestigious awards: the Hermes Award in 2015 and the Innovation Award of the German Economy in 2016.

Dr. Wittenstein noted that “Germany’s prosperity is built on its engineering skills. The engineering industry is our country’s core competency and the biggest industrial employer. It is vital that this marketability be preserved for the future. We believe that our invention makes a significant and valuable contribution here.”

Originally unveiled at the Hannover Messe in 2015, the Galaxie Drive System is based on a novel, scientifically proven gearbox class. The principle of the innovative Galaxie gearbox is founded on several pillars: forces and torques are transmitted not by rigid gear wheels but by separate teeth which can be moved independently of one another. Rather than rolling against each other, these teeth slide to and fro in a ring gear. Furthermore, a very large number of teeth engage with one another at any given time, leading to full-surface contact because they are designed as a logarithmic spiral. This concept inspired the nominated team of inventors – Thomas Bayer and Dr. Manfred Wittenstein – to develop a completely new gearbox class which was radically different from anything that had gone before. “We weren’t happy with the state of the art at the time. Although we could probably have improved certain aspects, we were convinced that there must be another way,” said Dr. Wittenstein.

The Galaxie gearbox from WITTENSTEIN is a completely new gearbox concept with separate teeth instead of rigid gear wheels.

Mechatronic drive systems like Galaxie are employed in all kinds of automated production machinery. From food and packaging through medical devices, vehicles and wind turbines to robots or machine tools – almost all daily commodities are manufactured with the help of motor-gearbox units or make use of similar drive systems.

Deutscher Zukunftspreis 2018
The Federal President’s Award for Innovation in Science and Technology was instituted and presented for the first time in 1997; the intention is to encourage world-class scientific achievements that are simultaneously marketable and a source of employment. The Deutscher Zukunftspreis is not an award that is applied for, in other words projects must be nominated by one of the institutions entitled to propose worthy candidates. Once a year, a jury comprised of 10 independent experts from academia and industry then selects three teams for the final round.

The announcement of the winning team will take place on November 28, 2018. For all further information, see www.wittenstein.de and www.deutscher-zukunftspreis.de.

How to specify motion components for cleanroom environments: Part 2

September 5, 2018 By Danielle Collins Leave a Comment

In this two-part article, we cover the products, materials, and features that designers and engineers should specify when choosing motion components for cleanroom environments.

In part 1, we looked at how to reduce particle generation due to friction between moving components. In this second part, we’ll look at another source of contamination — outgassing — and how to minimize it.

Objective #2: Minimize outgassing

Silicon wafer processing is extremely sensitive to contamination, including both particulates and outgassing.
Image credit: WaferPro

In cleanroom applications that involve the manufacture of LEDs, optics, or glass, or the processing of silicon wafers, a second type of contamination can damage the process or the product: outgassing.

Outgassing is the desorption of vapors or gasses, either from within a material or from the surface of a material. ISO standard 14644-8 addresses outgassing in cleanroom environments and specifically refers to airborne molecular contamination (AMC) as:

The presence in the atmosphere of a cleanroom or controlled environment of molecular (chemical, non-particulate) substances in the gaseous or vapor state that may have a deleterious effect on the product, process, or equipment in the cleanroom or controlled environment.

These types of airborne molecular contaminants take the form of molecular vapor. They’re smaller than particles and easily pass through HEPA and ULPA filters, making them particularly difficult to control once released.

Minimize outgassing through material selection

The first criteria when choosing motion components for cleanroom environments where outgassing is a concern is to ensure the material has a smooth surface, which makes it more difficult for airborne molecular contaminants to adhere to the surface. Stainless steel and anodized aluminum are the preferred materials, although some epoxy paints are suitable for environments where low-outgassing is required.

Fortunately, numerous motion control components, such as linear guides, motors, and gearboxes, can be made of stainless steel. When possible, plastic end caps on linear guides and screws should also be replaced with stainless steel versions to further minimize the use of plastics. And standard steel fastening hardware, such as screws or pins, should be replaced with stainless steel versions.

Although epoxy paint is sometimes suitable for motor and gearbox housings, stainless steel versions are better options.
Image credit: Wittenstein

When the required material has a high outgassing tendency, other solutions exist. For example, epoxy paint is suitable in some cleanroom environments and can be applied to the housings of linear actuators, motors, and gearboxes. And when steel is required — to maintain hardness, durability or load-carrying capacity — nickel plating can reduce the tendency of steel to outgas. (Note: Some nickel-plating formulas include a PTFE, or Teflon^®, top coat. The use of Teflon is generally advised against, so be sure to choose a nickel plating formula that does not include Teflon.)

Good: Nickel-plated steel, epoxy coated aluminum
Better: Stainless steel or anodized aluminum; minimal use of plastics
Look for: Smooth surfaces (no textured paints)

Reduce outgassing from lubricants

A wide variety of cleanroom-rated lubricants are suitable for bearings, motors, gearboxes, and other motion components.
Image credit: NSK

When it comes to outgassing, lubricants are one of the major offenders, readily spewing molecules of water and oil vapor into the atmosphere. Unfortunately, in the majority of motion systems, the use of components that require lubrication simply can’t be avoided. When lubrication is required, ensure the lubricant is suitable for cleanroom environments. Cleanroom compatible formulas that minimize outgassing while protecting bearing surfaces from rust and friction are widely available.

Good: Cleanroom-rated lubricants
Look for: Opportunities to minimize the need for lubrication through component selection

Feature image credit: Lin Engineering, Inc.

How to specify motion components for cleanroom environments: Part 1

August 29, 2018 By Danielle Collins Leave a Comment

In this two-part article, we cover the products, materials, and features that designers and engineers should specify when choosing motion components for cleanroom environments. In part 1, we look at how to reduce particle generation due to friction between moving components.

Designers of automation systems are tasked with many competing demands, such as balancing cost and performance, fitting motion components and systems into existing machine or process layouts, and designing for ease of manufacturing and assembly — to name a few. But when the system is to be used in a cleanroom, an additional layer of complexity is added, requiring designers to choose products that won’t degrade or compromise the cleanroom environment.

The level of “cleanliness” of a cleanroom is determined by the number of particles, broken down into six size ranges, that are present in a specified volume of air. In the United States, Federal Standard 209E is often used for cleanroom ratings, although it was officially canceled in 2001. This standard specifies cleanroom levels from 1 (best) to 100,000 (worst) in multiples of 10.

The current, and more universally-accepted, standard is ISO 14644-1, which defines cleanrooms on a scale from 1 (best) to 9 (worst). Each of the ISO classifications has a corresponding FS 209E level, with the exceptions of ISO classes 1 and 2, which are higher (better) than the highest FS 209E classification, and ISO class 9, which is lower (worse) than the lowest FS 209E classification.

ISO standard 14664-1 rates cleanrooms on a scale from 1 (best) to 9 (worst). Federal Standard 209E uses a scale from 1 (best) to 100,000 (worst) based on the number of allowable particles greater than or equal to 0.5 micron.
Image credit: Mecart Inc.

Objective #1: Reduce friction

One of the two primary sources of contamination, or particles, that can degrade a cleanroom environment is friction from moving components. (The other source is people.)

Virtually every motion system involves some amount of friction between sliding or rolling surfaces — whether from linear bearings, rotary bearings, or meshing gears. And when there is friction, particles are generated. Therefore, when specifying motion components for cleanroom environments, reducing friction should be the foremost objective.

Linear guides and drives

To minimize friction from linear guides, choose rolling contact rather than sliding contact and, when possible, avoid systems with high preload. For example, a non-preloaded miniature rail guide that uses two rows of recirculating balls emits significantly fewer particles than a preloaded standard guide with four rows of recirculating balls. And because there’s little chance of the bearing experiencing contamination in a cleanroom environment, use linear guides with low-friction or non-contact type seals.

Air bearings are another, although less common, method for guiding and supporting loads. In cleanroom applications, however, air bearings are often the best choice for low particle generation, since they are completely non-contact devices.

When it comes to linear drives, belts and chains should be avoided in cleanroom applications, due to the significant contact and wear they experience. Similarly, the meshing of gears in rack and pinion systems cause high friction and wear, so these should also be avoided. This means that ball screws are typically the default choice for linear drives in cleanroom applications.

However, ball screws require lubrication, and the rotation of the screw can cause lubrication to “sling” or “splatter,” contaminating the cleanroom environment. Using low-friction or non-contact seals (see above) will help keep the lubrication inside the ball nut and protect the cleanroom.

Like air bearings for linear guidance, linear motors provide a completely non-contact option for driving the load. But in their traditional setup, linear motors operate with the forcer (primary part) moving. This means the cables must move as well, and as we’ll discuss below, cables are another source of particle generation. A better configuration for cleanroom applications is to keep the forcer (primary part) and its cables stationary and allow the magnet track (secondary part) to move.

The combination of air bearing guides and a linear motor drive in this ABL 2000 stage from Aerotech provides completely non-contact movement, ideal for cleanroom applications.

Good: Rolling contact (rather than sliding contact) guides and drives
Better: Air bearing guides and linear motors
Look for: Low-friction or non-contact seals; cleanroom lubrication

Cables and cable management

Another source of friction and, therefore, particle generation, is the cable management system, including the cables themselves. Traditional round cables can generate particles when they rub against each other or against parts of the cable track. The best way to reduce particulates from cables and cable management systems is to use components and system design practices that reduce the amount of cabling required — for example, using an integrated motor-drive system instead of separate motor and drive components.

Cable carriers used in cleanrooms should have low vibration, low-abrasion fastening, and smooth interior surfaces to prevent abrasion of cables.
Image credit: igus Inc.

For the power, feedback, and data cables that are necessary in a motion control system, manufacturers offer cable designs with special low-friction coatings to minimize particulates and reduce outgassing. Similarly, several cable track manufacturers offer systems that reduce wear between chain sections through the use of abrasion-resistant joints. And for shorter lengths, so-called “trackless cables” are self-supporting flat cables that don’t require a cable track or carrier.

Trackless cables are self-supporting and don’t require cable carriers.
Image credit: W.L. Gore & Associates, Inc.

Good: Round cables with anti-friction coatings; cable carriers with abrasion-resistant joints
Better: Self-supporting flat cables
Look for: Opportunities to reduce cabling

Rotating equipment: motors and gearboxes

When it comes to rotating equipment in motion applications, the bad news is, motors and gearboxes use rotary bearings, and gearboxes require meshing teeth — all of which are sources of friction and particle generation. The good news is that these components are enclosed, so particles are less likely to “escape” and contaminate the cleanroom environment. And there is a wide range of cleanroom-compatible lubricants that can be used in the high-speed, high-load conditions found in motors and gearboxes.

To improve cleanroom compatibility, it is also possible to add a slight vacuum to the motor or gearbox housing. The vacuum serves to extract and remove particulates so they don’t have an opportunity to contaminate the cleanroom. Note that vacuum purge is also a good option for enclosed actuators that have a static (non-moving) seal. Although the enclosed design tends to keep particles inside the actuator, adding vacuum purge helps to achieve higher levels (class 100, 10, or 1) of cleanroom compatibility.

Vacuum purge is an effective way to ensure particulates from closed systems, such as this linear actuator, don’t have a chance to escape and degrade the cleanroom environment.
Image credit: THK Co., Ltd.

Good: Fully enclosed housings
Better: Vacuum purge
Look for: Cleanroom grease options

In part 2 of this article, we’ll look at another source of contamination — outgassing — and how to minimize it.

For a given motion profile, when are other options for stopping insufficient — and a clutch or brake necessary?

August 19, 2018 By Lisa Eitel Leave a Comment

At the core of most motion axes are electric motors. Stopping loads on their axes can be done with the electric motor itself — called internal braking in certain contexts — or with an external clutch or brake. For the former, one simple approach is to simply cut motor voltage input and allow the axis to coast to stop. That’s acceptable where stops are infrequent — from a few times a minute (for designs running off small motors) to a few times an hour (for larger motor installations). Another option is to use controls to generate stopping torque in the motor via regenerative braking t convert kinetic into electrical energy; dynamic braking — the injection of dc current into the stator; or electric reversal as plugging.

But where such approaches are too slow — including all modern motion designs for high throughput — external brakes and clutches are required to get sufficiently quick stops or disengagement. This applies to conveyors, airport-baggage handlers, escalators, and elevators … as well as other axes that make frequent stops and starts — even as few as 10 cycles a minute in some cases. Where stops and starts happen at much higher cycle rates, motor inertia may degrade the quickness with which starts and stops are possible. So here, clutch-brakes are often more suitable — as they disengage the driven load from the motor to allow the former to run even while the brake engages and stops the load. Of course, though we focus on responsiveness here, failsafe design features are another main driver of brake and clutch inclusion.

Mechanical, electric, fluidic, and self-actuated clutches and brakes are suitable for different applications. For example, spring-set brakes benefit motion designs that slow loads with the motor before the brake engages … and they’re suitable as holding mechanisms. Control of electric brakes is easy, and they can keep pace to a thousand cycles per minute. Most air-actuated brakes and clutches are cool-running and hold with minimal input. Friction brakes with drum, disc, and cone geometries deliver e-brake functionality with failsafe holding.

Brake or clutch size and type depend on whether the axis at hand will make emergency stops or softer stops that sacrifice the clutch or brake to protect systems and loads from shock. Or sometimes it’s more essential that the brake deliver soft stops to prevent shifting loads and misalignment. After that, other criteria — cycle rates, thermal capacity, machine envelope, and MRO schedules — dictate final selection.

Miki Pulley’s BXR-LE electric spring-applied brakes are suitable for small and precise servomotor designs. A lightweight design optimizes servodrive performance and efficiency. Its voltage controller means the brake’s power consumption is stepped down to 7 Vdc after a split second of 24 Vdc for actuation. When compared to most other electric brakes, the BXR-LE brake consumes just a third the power (and generates just a third the heat) — though it’s half as thick. Speed is to 6,000 rpm; static friction torque is 0.044 ft.lb. to 2.36 ft.lb. and ambient operating temperature is 14° to 104°F. BXR-LE brake applications include those on end effectors, ballscrew actuators, XYZ positioning tables, and 3D printers.

Some tips: Size clutches and brakes to the machine axis’ motor torque. Where a brake must stop vertical loads, account for how motors can briefly draw current to output in excess of their rated torque. Consult performance curves in manufacturer PDFs for dynamic torque ratings at set speeds to match the brake or clutch to peak motor-output torque. Case in point: Consider an inclined conveyor with regularly spaced on-off cycles. Here, a power-off spring-set brake may suffice to prevent load crashes during power failures. But more complex conveyor installations to position discrete product of varied size — without jerking — may need multiple deceleration rates may need more sophisticated spring-set brake plus drive on the motor for stopping … or even a permanent-magnet brake for quick yet soft starts and stops.

Comparing clutch and torque-limiter functions

Torque limiters are not clutches, as they’re not designed to continuously slip. That’s an important distinction when design engineers are specifying slowing and disengaging technologies for mechanical designs. Some tips for optimal design selection: First consider whether a torque limiter will only protect against catastrophic failure or semi-regular overloads. That will indicate whether an economical friction-style torque limiter is sufficient or if the design necessitates a ball-detent design. The latter is usually more costly but capable of slipping and triggering a limit switch for shutoff and resetting to resume operation. Ball-detent torque limiters here can slip multiple times in their application … unlike friction torque limiters requiring reset.

When applying a torque limiter, confirm whether a zero-backlash design is needed. Note that torque limiters can generate heat at their frictional connections, so upon their activation, system shutdown is key. After it’s activated, the end user should inspect the torque limiter for wear and heat damage. He or she should also check its setting torque … as in some designs, that value will be diminished if the torque limiter has been run too long. As long as the torque limiter is still within design range, it’s safe from exhibiting more and more slipping. With some motion designs, a limit or proximity switch paired with controls can detect when the torque limiter slips — and shuts the system down to let the end user address the issue the torque limiter was protect (or protect against). || Insight into torque-limiter functions provided by KTR engineering services manager Chris Scholz.

Brake modules such as the mayr ROBA brake-checker and the ROBA torqcontrol monitor the condition of safety brakes — and can facilitate smooth deceleration of machines and devices. Shown here is a ROBA brake-checker module that without sensors. Electronics track current and voltage and recognize the movement of the armature disc to assess brake condition as well as temperature, wear, and tension path or tensile force reserve — in other words, whether the electromagnetic brake’s magnet has sufficient force to attract the armature disc. On reaching the tensile force reserve, a warning signal sounds to prompt service. There is a design for ac voltage; a coming version of the module will integrate brake input power supply (and replace a separate rectifier) for switching condition monitoring and brake control in one device.

Zero-Max Crown right-angle drives include Class 10 spiral bevel gears lubricated for life

August 14, 2018 By Lisa Eitel Leave a Comment

Lubricated for life with Beacon 325 premium grade grease, Zero-Max Crown drives feature heat treated AGMA Class 10 spiral bevel gears. This combination of bearing design and lubrication formulation ensures long-term, maintenance free operation for high performance, industrial applications. The drives feature long-life, precision hardened and ground ball bearings handling speeds up to 2000 rpm in most operating environments. The internal gears are permanently mounted to the shafts with the use of a press-fit and locking pins. This provides a very resilient and durable connection for use in heavy load applications while needing no maintenance.

Lubrication with Beacon 325 grease ensures optimum performance in temperature ranges from -50° C to +120° C without evaporation. This is especially important in sealed for life systems using motors, generators and similar equipment in industrial applications.

Zero-Max ensures their drives are predictably smooth operating, and similar model sizes have identical performance characteristics when designed into multiple drive setups. To accomplish this, Zero-Max drives are precision assembled for bearing and gear alignment. The drives are prelubricated during assembly, then completely enclosed in a heavy-duty anodized aluminum housing. This design ensures that internal gears stay permanently aligned, lubricated and free of contamination from outside debris.

Zero-Max Crown drives are suitable for a wide range of machine applications including food processing, packaging and material handling systems. Available in many sizes and models, they are suitable for myriad horsepower, torque and shaft speed requirements. Standard two and three-way models are available with 1:1 and 2:1 speed ratios in shaft diameter combinations of 3/8, 1/2, 5/8 and 3/4 in.

For more information, visit www.zero-max.com —or call (800) 533-1731 for a brochure.

Common challenges that wave springs address

August 13, 2018 By Lisa Eitel Leave a Comment

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.

Miki Pulley BXR-LE electric brakes for direct drive servo motors

August 10, 2018 By Mike Santora Leave a Comment

Miki Pulley’s BXR-LE electric spring applied brakes are suitable for small and precise servo motor configurations. Their unique compact and lightweight design optimizes servo drive performance and efficiency.

With accompanying voltage controller, the brake’s power consumption is stepped down to 7VDC after a split second of 24VDC for brake actuation. When compared to most other electric brakes, the BXR-LE design provides just one-third power consumption and heat generation in one-half the overall size thickness.

Specifications:

Maximum RPM: 6000
Static friction torque range: 0.044 to 2.36 ft.lb. (0.06 to 3.20 Nm)
Ambient operating temperature 14° – 104°F(-10° to 40°C)

Additional applications:

End effectors.
Ball screw actuators.
XYZ positioning tables.
3D printers

Miki Pulley
www.mikipulley.co

Updated: Basics of compression springs for motion designs

July 25, 2018 By Lisa Eitel Leave a Comment

Engineers incorporate compression springs in motion designs that need linear compressive forces and mechanical energy storage — designs such as pneumatic cylinders and push-button controls, for example. The most conventional compression spring is a round metallic wire coiled into a helical form.

Photo courtesy Lee Spring

This compression spring has a barrel shape for lateral stability.

The most common compression spring, the straight metal coil spring, bends at the same diameter for its entire length, so has a cylindrical shape.

Cone-shaped metal compression springs are distinct in that diameter changes gradually from a large end to a small end; in other words, they bend at a tighter radius at one end. Cone-shaped springs generally go into applications that need low solid height (the total height when compressed) and higher resistance to surging. Whether cylindrical or cone shaped, helical compression springs often go over a rod or fit inside a hole that controls the spring’s movement.

Other configuration types include hourglass (concave), barrel (convex), and magazine (in which the wire coils into a rectangular helix).

This compression spring has reduced ends.

Most compression springs have squared and ground ends. Ground ends provide flat planes and stability under load travel. Squareness is a characteristic that influences how the axis force produced by the spring can be transferred to adjacent parts.

Although open ends may be suitable in some applications, closed ends afford a greater degree of squareness.

Squared and ground end compression springs are useful for applications that specify high-duty springs; unusually close tolerances on load or rate; minimized solid height; accurate seating and uniform bearing pressures; and minimized buckling.

This concave (hourglass-shaped) compression spring can stay centered, even in large-diameter bores.

The key physical dimensions and operating characteristics of these springs include their outside diameter (OD), inside diameter, wire diameter, free length, solid height, and spring rate or stiffness.

• Free length is the overall length of a spring in the unloaded position.

• Solid height is the length of a compression spring under sufficient load to bring all coils into contact with adjacent coils.

• Spring rate is the change in load per unit deflection in pounds per inch (lb/in.) or Newtons per millimeter (N/mm).

The dimensions, along with the load and deflection requirements, determine the mechanical stresses in the spring.

When the design loads a compression spring, the coiled wire is stressed in torsion and the stress is greatest at the wire surface.

As the spring is deflected, the load varies, causing a range of operating stress. Stress and stress range affect the life of the spring.

The higher the stress range, the lower the maximum stress must be to obtain comparable life. Relatively high stresses may be used when the stress range is low or if the spring is subjected to static loads only.

The stress at solid height must be low enough to avoid permanent damage because springs are often compressed solid during installation.
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Timken acquiring precision-drives maker Cone Drive

July 24, 2018 By Lisa Eitel Leave a Comment

The Timken Company has reached an agreement to acquire Cone Drive, a leader in precision drives used in diverse markets including solar, automation, aerial platforms, and food and beverage. Cone Drive sales are expected to be slightly above $100 million for the full year 2018.

“We are executing our strategy to profitably grow Timken’s power transmission offering across diverse markets around the world,” said Richard G. Kyle, Timken president and chief executive officer. “The acquisition of Cone Drive will deepen Timken’s position in attractive, high-growth end markets such as solar and increase our power transmission presence in China. Cone Drive is highly complementary to our business, and we plan to generate significant sales and cost synergies with this transaction.”

Cone Drive is headquartered in Traverse City, Mich., and has manufacturing operations in the United States and China. The company has a global customer base and employs approximately 500 people. The business produces a broad range of highly customizable precision drive products that include Cone Drive and H-Fang branded high-torque worm gears, harmonic solutions and precision slew drives.

In recent years, Timken has diversified its portfolio by expanding into power transmission products and services adjacent to its core bearing lines. This includes gear drives, chain, belts, couplings, automated lubrication systems, industrial clutches and brakes, and a variety of related services, all marketed under strong industrial brands that include Timken, Philadelphia Gear, Groeneveld Drives, and Lovejoy.

Timken expects the acquisition to be accretive to earnings per share excluding one-time costs in the first year of ownership. The transaction, which is subject to customary government and regulatory approvals, is expected to close near the end of August 2018 and will be funded with debt.

Presentation materials related to this transaction have been posted to investors.timken.com.

The Timken Company engineers, manufactures and markets bearings, gear drives, belts, chain, couplings, lubrication systems and related products, and offers a spectrum of powertrain rebuild and repair services. The leading authority on tapered roller bearings, Timken today applies its deep knowledge of metallurgy, tribology and mechanical power transmission across a variety of bearings and related systems to improve the reliability and efficiency of machinery and equipment all around the world.