12 minute read
New coupling technologies offer more support for encoders...more miniaturization...and new IoT functionalities
The location of mechanical couplings — connecting rotating shafts powered by electric motors and fairly close to the loads being moved or manipulated — makes it an ideal place to optimize the performance of machine axes. No wonder that our 2020 Design World Trends survey of industry experts indicates an uptick in innovation related to optimizing the torque and angular velocity through couplings and (with flexible variations) compensation for misalignment that’s more robust than ever. Some feedback even suggests all-new options for addressing vibration and improving system dynamics.
This applied to couplings for motion-control applications (including positioning axes) such as disc, slit or beam, curved-jaw, bellows, and other zero-backlash couplings for precise torque transmission. It also included rugged couplings for power transmission (as in heavier equipment as well as pumps and material-handling machinery) such as Oldham, disc, grid, jaw, and gear couplings. Just consider the input of Robert Watkins, V.P. of sales and applications at Ruland Manufacturing Co.
Please discuss the use of couplings in reconfigurable conveyor installations as well as linear-transfer systems.
The conveyor market as a whole has been increasing steadily over the last few years as Amazon, UPS, FedEx, and the Postal Service modernize and expand their facilities. Warehouses using these conveyors often have shaft collars seated against rollers or bearings as safety stops or for component alignment.
Couplings can drive the conveyor itself … or can go on conveyor accessories such as sorting switches. Of course, shaft collars and couplings are designed in on various manufacturers’ conveyors — and in many cases, the same exact part is used regardless of the system. This can make it challenging to identify what conveyor types are spiking in demand unless we are explicitly told by the manufacturer.
Controlflex couplings from Ruland Manufacturing Co. solve three encoder application requirements.
What applications have you supported over the last 12 months?
At Ruland, we’re expanding the types of couplings we offer to better meet the varied demands of our users. Over the last year, we’ve added Controlflex couplings and slit-type couplings to our lineup. We’ve also added universal joints and developed stainless-steel Oldham couplings.
Controlflex solves three specific encoder application requirements that our standard beam couplings do not.
1. First, Controlflex couplings have speed capabilities to 25,000 rpm in contrast with our standard beam couplings rated to 6,000 rpm. Of course, other beam couplings on the market are rated to 10,000 rpm … but these can be insufficient, as there are plenty of encoder applications that operate to 10,000 rpm and beyond.
2. Controlflex couplings can fit into confined spaces with a length-to-outer-diameter ratio under 1:1. Even in single-beam couplings — a standard style of encoder coupling — the ratio normally tops out at 1:1. Tight envelopes are common in encoders because mounts are often custom built … leading to a lack of standardization. Designers are usually trying to keep them on the shorter side to reduce the amount of misalignment. This can result in an unusual sizing relationship between the shaft sizes and coupling envelop requirements.
3. Lastly, Controlflex couplings come in myriad versions — including those with dramatically different bore-size combinations.
Shown here is a stainlesssteel Oldham coupling from Ruland Manufacturing Co.
At Ruland, our beam couplings usually have a large-to-small bore size ratio of 2:1. It’s not uncommon in an encoder to have a large motor shaft (such as 20 mm) connecting to a small encoder shaft — such as 8 mm, for example. Our standard beam couplings cannot accommodate this drastic step in shaft sizes. That’s because when we designed the beam coupling line, it was meant for encoders and light-duty servo applications … which meant we had to be able to maintain torque transmission throughout the bore range. Such large steps in shaft sizes made it challenging to rate the coupling to our desired torque level, because it would overcome the clamping force on an 8-mm shaft.
In contrast, Controlflex can handle a largeto-small bore ratio of up to 3.5:1 depending on the outer diameter size. This gives designers a lot of flexibility when selecting an encoder to attach to their motor.
Ruland is distributing Controlflex, which is manufactured by Schmidt Kupplung in Germany. We have had a long partnership with Schmidt, who owns our German distributor Orbit — so it made sense to partner on stocking and reboring Controlflex couplings.
These are some examples of shaft collars from Ruland Manufacturing Co.
What new support are you offering to laboratory automation or other industries that require small and precise builds?
Slit couplings are our newest addition and fill four existing holes in our product range. They have small bore sizes down to 1.5 mm. These sizes are common in scientific and analytical equipment. Nothing in our standard product range fits sizes that small.
These new slit couplings also have speed capabilities to 70,000 rpm. Such speeds are common in those small shaft sizes … though even the larger bore sizes that cross into our standard size range have higher rpm options.
Thirdly, these new slit couplings have moderate torque and high misalignment capabilities. We don’t have another standard coupling that satisfies applications with parameters that fall between those that suggest the use of bellows or disc couplings and those that suggest the use of beam couplings with low inertia. After all, bellows and disc couplings are high-performance couplings that have limited misalignment capabilities. Aluminum beam couplings have limited torque and high misalignment capabilities … and stainless-steel beam couplings have high inertia. The high inertia is not desired in most motion control systems.
Slit couplings have torque capabilities comparable to those of stainless-steel beam couplings but with better overall misalignment capabilities.
Lastly, our new slit couplings can fit in confined spaces and accommodate all misalignment forms. Currently, the only product we sell for high torque in tight envelopes is a single disc coupling. They have no accommodation for parallel misalignment which causes problems if misalignment can't be precisely controlled.
This is a double-slit Reliaflex flexible coupling from Ruland Manufacturing Co. to accommodate eccentricity and declination as well as axial misalignment between shafts. High-strength 7075-T6 Duralumin maintains twisting rigidity.
Our slit couplings are manufactured by Reliance Precision in Ireland. Reliance is well known for building precision assemblies and assisting companies with their designs. They have been using Ruland couplings as one of their standard options for many years.
Do any of your couplings go into food and beverage machinery subject to washdown?
Stainless-steel Oldham couplings were recently added to our standard offerings because they address three design challenges our other couplings do not.
1. Stainless-steel Oldham couplings are suitable for food processing and packaging applications that may experience washdown. Our other coupling styles use aluminum as the base material. The exception is stainless-steel beam couplings … however, these are not a corrosion resistant coupling. The standard hardware is alloy steel and will rust which can lead to failure.
2. The stainless steel Oldham product line has a stainless steel screw giving it consistent corrosion protection. Second, they can be used in high temperature applications. When combined with a PEEK disk they are capable of temperatures up to 148° C far surpassing anything else in our standard product range.
3. Lastly, stainless steel Oldham couplings excel in applications where low outgassing is required. Two caveats: This does require the use of a PEEK disk … and the end user may have to change out the standard screw (which has a proprietary anti-galling coating) depending on the application.
Describe how the increasingly common process of outsourcing the design of motion subassemblies has impacted you.
Ruland is seeing more coupling applications start with a design and prototyping firm as opposed to an OEM. This makes sense as companies have streamlined operations with R&D augmented by an outsourcing partner. As a manufacturer and component supplier, this trend hasn’t altered our process or interaction with customers. We may not know who the end customer is but the requirements won’t change and the mechanical engineers at the design firms have all the requisite expertise to properly select couplings … or give us the information to help in selection.
Where have your couplings been applied in robotic or AGV applications?
Ruland components are in numerous robotics applications. These systems often use smaller shafts and require zero-backlash operation — and that’s where our couplings fit in the market. Robotics covers a broad range of application requirements. Our vast coupling product line lets designers come to us as a single source and use standard off-the-shelf components regardless of system needs.
This is a new TSC150 coupling (to transmit up to 150 ft lb) from Twin Spring Coupling. The manufacturer is currently developing a smaller version called the TSC100 for compact industrial applications. In contrast with certain beam, bellows, and elastomeric couplings that can in some instances allow only limited misalignment angles. “Our couplings can be used at least twice that angle. This lets design engineers redesign equipment to leverage our couplings and their high flexibility — without having to resort to traditional options such as universal joints,” explains Twin Spring Coupling CEO and founder Darren Finch. “That in turn helps engineers avoid the maintenance issues some such technologies introduce — such as the requirement for constant lubrication, broken yokes, and worn bearings. “Our one-piece design and no internal bearings means we can offer the performance of the universal joint without the issues commonly associated with them,” adds Finch.
COUPLINGS: THE PERFECT PLACE FOR SENSORS
In another conversation with Andrew Lechner of R+W, we discussed IoT functionality in a new line of couplings from the component manufacturer motion components. Here’s what Lechner had to say.
Lechner • R+W: 15 or so years ago, we experimented with bellows couplings capable of measuring misalignment. couplings that can provide information about shaft misalignment and torque. In fact, for a couple decades other coupling manufacturers have supplied couplings integrating torque meters ... but these are no different from standard torque meters — and they require a static component in addition to the rotating coupling.
R+W actually leads in IIoT innovation, and has made significant progress on such technology through our R&D department ... which includes a team of engineers 100% dedicated to the development of smart couplings. What’s changed is that suddenly our industry is very interested in the IIoT … so now machine builders are asking: “How do your components connect? What’s your part in all of this?”
Now we’ve released an informative coupling that goes beyond torque measurements to monitor other characteristics in the driveline — and address current technologies’ deficiencies in accurately recording downstream performance characteristics.
There are problems associated with both of the dominant technologies currently used.
• Readings done at the motor drive are often too insensitive to what’s happening at the furthest reaches of the axis, as such readings are too far upstream and can fail to account for driveline inertia.
• Torque sensors and vibration monitors peppered over a machine at strategic locations can be expensive and typically require static base stations to be nearby.
The third option we offer with our informative coupling packages the sensing into a rotating component farther down the driveline and outputs signals wirelessly — for a more effective and economical solution overall.
Lisa Eitel • Design World: What industries will these products serve?
Lechner • R+W: Much of the interest has been from our industrial equipment customers — so people in the process industry designing extruder, pumping, and heavier manufacturing applications. Here, a flywheel effect can greatly influence driveline components downstream without much effect at all on the motor. So the first models of these informative couplings are for application torques of 350 to 2,500 Nm.
Do you think we’ll see informative couplings for smaller applications?
Lechner • R+W: I hope we will. Of course, smaller motor drives can be somewhat more sensitive than larger drives ... but we've observed that even small servos can fail to detect the downstream results of impact loads and abrupt stops. Of course, it’s a design objective to make all industrial rotating equipment compact. The sensor package on current informative-coupling models is about 75 mm long … of course, the larger the transmission, the less impact this size has on the overall design footprint.
Shown here is a coupling from R+W that integrates an array of sensing devices to provide useful information about applications at a location that’s particularly useful — close to where the axis moves or manipulates the load.
What was behind the decision to use a battery to power the sensors?
Lechner • R+W: Batteries are robust and easy to implement. We extend sensor operation by allowing two modes — a high-resolution mode to allow three days of data collection and a lower-resolution mode for a couple weeks of data collection.
Of course, many engineers want this design to have constant power sans need for recharging. That’s why we’re currently developing an informative-coupling variation with energy harvesters to allow 24/7 high-resolution monitoring.
Would you be at liberty to discuss the exact sensor technologies inside?
Lechner • R+W: Torque and axial strain are measured with strain gauges. Then accelerometers measure vibration. A gyroscope tracks speed. These devices are similar to those you’d find in your phone.
It’s Moore’s law at work.
Lechner • R+W: Indeed. Traditional methods of developing and bringing such a coupling to market are obsolete; now we need to build the car while we’re driving it. So the informative couplings we are selling now are prototype-level oneoffs — and we’re perfecting the design in partnership with OEMs. We aim to sell informative couplings as standard catalog product toward the end of 2020. In fact, engineers who want to share their thoughts on this company are invited to review the R+W information we’ve published on this offering and fill out a survey we’ve setup.
We’ll be sure to post that questionnaire on motioncontroltips.com. Engineers can also visit www.ai-coupling.com. Moving on to integrating these couplings … what output signals does this informative coupling generate?
Lechner • R+W: We keep the design simple so end users can easily get their data. There's wireless transmission to the R+W Android app. We're also developing a gateway with USB, RS232, and analog output. End users can also emulate a serial connection using third-party software. Soon, R+W informative couplings could have IO-Link connectivity as well.
The R+W iLP3 mobile app allows access to key informative-coupling data.
Is the R+W app for this readily available — or is that still in development?
Lechner • R+W: In Germany it's on Google Play as an Android app. Once proven, it’ll release in the U.S. … most likely in July.
Is this technology primarily to support predictive maintenance?
Lechner • R+W: There’s far more to it than that. Predictive maintenance is the first function, as that affords lets end users know when tools are worn or axes are exhibiting misalignment or lubrication loss.
In addition, the informative coupling supports condition monitoring. Case in point: Process engineers involved in everything from food to plastics to oil (such as drilling mud in the oil industry) must monitor viscosity variations along with other properties of the material being processed. Measuring torque required by a mixer, extruder, or pump to stir or push through that substance at the coupling yields accurate information about viscosity.
For example, the start of an extrusion process needing more torque than usual may indicate that the vat of plastic is too cold — and requires more warming. Here, our informative coupling can help optimize such processes.
