Corrosion-Resistant Couplings Suitable For Multiple Applications
February 25, 2010 by CouplingTips
Filed under Featured, Safety
A full line of shaft collars and couplings for pump drive and structural systems in water treatment, pollution control, and similar facilities is available from Stafford Manufacturing Corp. of Wilmington, Massachusetts.
Stafford Corrosion-Resistant Collars and Couplings are offered in 303 and 316 stainless steel, brass, bronze, and other materials for various power transmission and structural system requirements. Featuring a wide range of sizes and styles, they are suitable for use in pump drive systems, mixing equipment, flow control instruments, and other applications exposed to water, harsh chemicals, solvents, and detergents.
Developed for water treatment, pollution control, pulp and paper, chemical plants and related facilities, Stafford Corrosion-Resistant Collars come in 1-pc, 2-pc and set-screw styles in sizes up to 16″ I.D. and the couplings in 1-pc, 2-pc, and 3-pc styles up to 6″ I.D. All can be modified with special bores, keyways, mounting holes, flats, hinges, threads, and more.
High Misalignment, Low Inertia Servo Couplings
January 25, 2010 by CouplingTips
Filed under Bellows, Featured
The trend in industry to process more material, faster and more efficiently calls for a high torque, high misalignment, low inertia servo coupling, with minimal compromise to torsional stiffness. Stainless steel bellows couplings have the highest torsional stiffness of commercially available flexible couplings, making them the best choice for aggressive servo driven applications. But in cases where the two shafts to be connected are mounted to different bearing surfaces, it can be difficult to maintain the precise alignment tolerances normally required.
Utilizing a special, high stiffness bellows and new, high strength connection method, the BKZ handles an average of 2.6x the traditional torque rating at a given outside diameter, and an average of 2.9x more lateral misalignment, opening up the benefits of precision bellows couplings to a whole new segment of machine design and servo motion control.
Accepting bore diameters ranging from 15 to 60mm and torque ratings from 20 to 1000Nm, the BKZ range is available in 4 sizes, with a variety of materials, finishes and the optional self-opening clamp system. View online at http://www.rw-america.com/bellows_couplings/bellow-coupling-bkz-t.php
R+W America
www.rw-america.com
Why Couplings Need Lubrification
January 18, 2010 by CouplingTips
Filed under Featured, Industry News
In an ideal world, multiple components could be produced in a single piece, or coupled and installed in perfect alignment. However, in the real world, separate components must be brought together and connected on-site.
Couplings are required to transmit rotational forces (torque) between two lengths of shaft, and despite the most rigorous attempts, alignment is never perfect. To maximize the life of components such as bearings and shafts, flexibility must be built in to absorb the residual misalignment that remains after all possible adjustments are made. Proper lubrication of couplings is critical to their performance.
Figure 1. Types of Misalignment
MISALIGNMENT
Misalignment can occur as either an offset or angular displacement on two of the three possible axes (Figure 1). The third axis, in the longitudinal direction, is not commonly measured, though errors in this direction can result in excessive thrust loads in a system. For major installations, such as large compressors, wire alignment methods are used. Smaller applications have traditionally used rim-and-face dial indicator readings to quantify and correct misalignment, though optical laser indicators have grown in popularity due to their ease of use and accuracy.In pace-setting maintenance organizations, efforts are also made to compensate for thermal growth that occurs in equipment during operation. All materials (except water) expand a small amount when heated; the amount by which they do so is governed by the material’s coefficient of thermal expansion and the degree to which it is heated. A machine that is brought into alignment at ambient temperature will creep into a position of misalignment as the machinery materials climb or fall to operating temperature.
Attempts are made to preheat or cool equipment to normal operating conditions before performing alignment checks. Alternatively, calculations of anticipated thermal growth can be used to intentionally misalign the drivetrain at ambient temperature so that it may grow into alignment. Whatever precautions are taken to make alignments as precise as possible, some amount of residual misalignment will inevitably remain. Misalignment forces rigid machine components such as shafts to deflect in order to effectively become aligned. This deflection stresses the components, causes vibrations, and distributes higher and uneven loads on the structures that support these elements, such as bearings. These stresses waste energy and can dramatically reduce equipment life and reliability.
Designed properly, couplings can absorb misalignment forces so that more expensive, critical and sensitive components may be saved. While rotating shafts appear sturdy, the bearings which support them are some of the most sensitive precision components in the drivetrain.
Figure 2. Gear Couplings
TYPES OF COUPLINGS
Coupling designs may be divided into four principal categories, each having several specific designs. Solid and magnetic couplings do not require lubrication, but are included here for completeness. Solid couplings are fundamentally rigid structures that do not compensate for misalignment, but do allow two shafts to be joined for the purpose of transmitting torque. Bolted hubs keyed onto shafts are an example of a machine with magnetic couplings. Magnetic couplings allow shafts not in direct contact to be driven together using powerful permanent or electrical magnets. A sealless magnetic drive pump is a common example.Other coupling types are flexible couplings and fluid couplings. Many flexible couplings use fixed-position flexible metallic, rubber or plastic elements, such as discs or bushings, that rotate with the shafts and absorb misalignment. Designs of this type do not require lubrication. Others such as geared, chain, grid and universal joints do require lubrication for performance and longevity. Fluid couplings include torque converters and torque multipliers. These couplings are filled with lubricating fluids that rely on the fluid to transmit torque.
Figure 3. Chain Couplings
FLEXIBLE COUPLINGS
Gear couplings (Figure 2) compensate for misalignment via the clearance between gear teeth. Shaft-mounted external gear teeth on both shafts mate with internal gear teeth on a housing that contains a lubricant. Other designs mount external teeth on only one shaft, mating with internal teeth mounted to the other shaft. Acceleration or deceleration can result in impacts between gear teeth due to backlash from the clearance being taken up on opposite sides of gear teeth. Misalignment will result in sliding relative motion across mating teeth as they pass through each revolution.Chain couplings (Figure 3) operate similarly to gear couplings. Sprockets on each shaft end are connected by a roller chain. Clearance between components and clearance in mating the chain to the sprockets compensate for the misalignment. Loading is similar to that of geared couplings.
External grid couplings (Figure 4) use a corrugated steel grid that bends to compensate for loading induced by misalignment. Grooved discs attached to the ends of each shaft house the grid, which transmits torque between them. Low-amplitude sliding motion develops between the grid and grooves as the grid deforms under load, widening in some locations and narrowing in others over each revolution.
Universal joints are used for maximum allowable misalignment up to 20 to 30 degrees, depending upon the design. They are used extensively for the drive shafts of vehicles to allow the wheels to move with the suspension system. Universal joints use a four-spindled component called the spider to connect two shafts terminating in yokes or knuckles at right angles (Figure 5). Each of the four spider journals is supported by a bearing or bushing contained in one of the knuckles, which allow articulation.
Figure 4. Grid Coupling
FLEXIBLE COUPLING LUBES
Both lubricating oils and greases can be selected to lubricate flexible couplings. Unless specifically noted by the coupling designer, couplings for the majority of industrial components are grease lubricated. Coupling components are protected primarily by an oil film which bleeds from the grease thickener and seeps into the loading zone.Lubricated flexible couplings require protection from the low-amplitude relative motion that develops between components. Other concerns include centrifugal stress on the lubricant (particularly grease), which causes premature separation of the oil from the thickener, poor oil distribution within the housing and oil leakage from the housing.
The motion’s low amplitude, articulation speed and tendency toward a sliding rather than rolling action inhibits the development of hydrodynamic (full-film) lubrication. Greases made with high-viscosity base oils, anti-scuff (EP) and metal-wetting agents are recommended to overcome the boundary (mixed-film) conditions that often exist in flexible couplings. High oil viscosity also slows the leakage rates.
Centrifugal forces in flexible couplings can be extreme, becoming greater with increased distance from the rotational axis. Even moderately sized couplings can generate forces thousands of times greater than gravity (referred to as Gs). Grease makers put a high priority on formulations that resist premature separation of oil and thickener due to the high G forces.
Figure 5. Universal Joint
FLUID COUPLINGS
Fluid couplings transfer momentum from the input shaft to a fluid and then to the output shaft when transmitting torque. Misalignment is accommodated solely by clearances between the moving parts. The small clearances don’t provide much room for error in alignment. However, it is possible to effectively compensate for shock loading and high-torque starting loads as there is no solid connection between input and output shafts.In fluid couplings, an impeller attached to the input shaft accelerates fluid within the coupling as it spins, much like in a centrifugal pump. This fluid then hits the vanes of the output shaft’s runner, transferring its momentum as the runner accelerates. It will accelerate until it approaches the speed of the input shaft, but will never actually reach it. The difference in speed between the input and output shafts is known as slippage. Of course, frictional and viscous drag must be overcome before the output shaft can rotate. The minimum input speed required for this condition is known as the stall speed. Equipment with large static loads, such as a steam or gas turbine, would use a fluid coupling to minimize the initial stress on the driving shaft.
Shock loads on the input side, such as starting torque, are never created. The speed of the input shaft is never restrained. When the stall speed is exceeded, the output shaft will begin to accelerate, but will do so at a constrained rate due to its moment of inertia (resistance to angular acceleration). Slippage is created as the runner accelerates to the speed of the input, dissipating excess energy through viscous heat generation in the fluid. Output side shock loads will be similarly dissipated, even if the output shaft should completely stall.
Torque converters and multipliers are special applications of fluid couplings that allow the input torque to be modified before transmission. These designs operate fundamentally by the same principles, but are mechanically much more complex.
FLUID COUPLING LUBES
The dissipation of energy that makes fluid couplings so tolerant of shock loading creates the potential for rapid and extreme increases in fluid temperature. The energy dissipated during stall and slip is converted to heat through the viscous shearing of the fluid (fluid internal friction). In extreme applications, the fluid temperature can rise above the normal 200-degree Fahrenheit operating temperature in less than a minute.Oxidation and thermal degradation resistance are important qualities of oil used for fluid couplings because of the potential for drastic temperature increases. Similarly, a high viscosity index (VI) is also useful to prevent severe decreases in operating viscosity at temperature spikes and excessively high operating viscosity at low-temperature conditions.
Low-viscosity fluids are ordinarily used in these applications to reduce the power lost to heat due to fluid friction. Fluid coupling viscosities may fall between 2.5 to 72 centistokes (cSt) at 40 degrees Celsius. For fluid couplings designed to operate at high temperatures, viscosity limits may be given at 100 C.
These fluids must also resist foaming due to the severe agitation caused by the impeller’s movement and its impact upon the runner vanes. Rust-protective properties help preserve the coupling’s metal components. Hydrocarbon-based fluids are superior in this regard to other fluids, but their performance can be improved through rust-inhibiting additives. Seal compatibility is also important for long-life usefulness.
RECOMMENDATIONS
Acceptable life can be expected from any of these devices only if proper maintenance is performed. Lubricant levels and quality must be verified through periodic checks. Additional lubricant may be needed to compensate for leakage. Periodically flush and change the lubricant to remove harmful by-products of lubricant breakdown, to replace oil-depleted grease or to refresh the additive population. Gear couplings require perhaps the most maintenance. Typical relubrication intervals are six months to one year, depending upon application severity and experience.All maintenance tasks must be performed with attention paid to contamination control. The sliding contact suffered by many couplings indicates that abrasive three-body wear caused by particulate contamination could be particularly damaging. Improper removal of solvents used to clean couplings during inspections and flushing operations can lead to significant viscous thinning of the lubricant in operation or detrimental reactions with grease-thickening materials.
Couplings will endure when the demands placed on them are reduced. Consider the first line of defense to be a minimization of shock loading, including hard starts and sudden load reversals. Sometimes operational demands make this impossible. The principal source of loading in coupling systems can be controlled to a great extent, however. Proper alignment is considered a high-priority, precision maintenance functions. Use vibration analysis or thermography during operation to identify couplings that are not in alignment, as even the sturdiest foundations shift over time. Certainly, check for proper alignment whenever intrusive maintenance or repairs are performed on the coupled components.
New Jaw Couplings Have Zero Backlash
December 18, 2009 by CouplingTips
Filed under Featured, Jaw
Zero backlash jaw couplings that are three piece couplings comprised of two hubs and a plastic element are one of Ruland Manufacturing’s new products in their coupling line.
The Spider, shown below, made of an advanced polyurethane material, provides dampening of impulse loads, minimizing shock to the motor and other sensitive equipment.
Available in two durometers, these spiders allow the user to customize the jaw coupling’s performance. Selecting a soft spider will give the jaw coupling the greatest dampening characteristics, while a hard spider will provide the greatest torsional stiffness and strength. All spiders are press fit onto a curved jaw profile, assuring zero backlash operation. The curved jaw profile concentrates the forces to the center of the spider’s limbs, improving the effectiveness of the elastomer material. Raised contact points on the spider limbs help maintain proper spacing between the two hubs, assuring electrical isolation and full angular misalignment capabilities.
Jaw couplings are considered fail safe because, even if a spider fails, the jaws of the two hubs interlock allowing direct power transmission, allowing the application to be safely shut down for maintenance.
Machined Spring Features HELI-CAL Flexure
December 17, 2009 by CouplingTips
Filed under Featured, Flexible
SANTA MARIA, CA—The HELI-CAL® Flexure is a flexible helix (curved beam) machined into a unique configuration that incorporates special design requirements, performance features and/or characteristics. The material is basically unlimited.
When used as a spring, the multi-functional flexure provides desired and predictable elastic performance in compression, extension, torsion, lateral bending and lateral translation modes.
One huge advantage of this technology—it enables customer specified end-attachments, such as tangs, clamps, flanges or threaded ends to be integrated into a single multi-functional component.
Helical Products Company, Inc.
www.Heli-Cal.com
Neo-Flex Couplings from Advanced Antivibration Components
November 10, 2009 by CouplingTips
Filed under Featured, Flexible
New Hyde Park NY — A new series of metric Neo-Flex couplings from Advanced Antivibration Components – AAC feature excellent torsional vibration isolation plus shaft-to-shaft insulation. The center of these couplings, identified as the V50FSR-… (inch) and V50FSRM… (metric) for the Short Series, and V5DFLR-…(inch) and V5DFLRM (metric) for the Long Series, are made from 73 durometer molded neoprene along with 303 stainless steel hubs. They are featured at the AAC eStore where you can order online, request a quote, download CAD models, check stock plus view catalog and technical pages.
They are stocked in two hub styles, conventional pin type hubs which use a set screw for fastening and a Fairloc® version. Fairloc® is a patented integral hub fastener which eliminates marred shafts. The choice of Fairloc® hubs permits frequent phase adjustment, timing and position adjustment while adding positive metal-to-metal fastening strength along both hub sections. The Fairloc® integral hub fastener consists of two slots that are machined into the hub, one radially the other angularly, to create a transverse wedge which remains attached to the solid portion of the hub on one side. The resultant cantilevered clamping section has a tapped hole to accept a cap screw which passes through a clearance hole in the solid portion of the hub, and into a threaded hole in the transverse wedge section. As the screw is tightened, the cantilevered section clamps the shaft securely. The screw can be tightened and released repeatedly without marring the shaft or affecting its torque-transmitting abilities.
They are stocked with both ribbed and smooth style center sections. The ribbed style features an angular misalignment of 5° or 15° (long style) and a parallel offset of 0.25 mm (.010″)(short style) or 0.38 mm (.015″)(long style). The smooth style features an angular misalignment of 1° (short style) or 8° (long style) and a parallel offset of 0.13 mm (.005″)(short style) or 0.25mm (.010″)(long style). They are designed to fit 3 to 6 mm metric shafts or .1200, 1/8, 3/16 and 1/4 inch shafts.
Advanced Antivibration Components – AAC
www.vibrationmounts.com/NewProducts/NeoFlexCouplings.htm
Silicone Insert Couplings from Sterling Instrument
November 9, 2009 by CouplingTips
Filed under Featured, Industry News, Rigid
New Hyde Park, NY — A new series of silicone insert couplings from Sterling Instrument (ISO 9001:2000+AS9100B Registered Manufacturer) features electrical isolation and no backlash. These metric couplings, identified as the S54HSAM… (clamp type) and S5PSAM… (set screw type) Series are stocked in 5 different bore sizes ranging from (6 mm to 16 mm).
These couplings have aluminum hubs with either set screws or clamps for fastening to shafts. The insert is silicone 40 ShA. Operating temperature ranges from -50°C to +150°C. They range in length from 26.5 mm to 57 mm. Their maximum speed is 5000 rpm.
They can be used in various applications and are especially able to accommodate tight or skewed connections. Quotes, online orders, available stock, and 3D CAD Model downloads are available at our new eStore at: www.sdp-si.com/eStore. SDP/SI offers over 1000 different types of couplings including inch and metric: magnetic, flexible, rigid, oldham, bellows, flexible shaft, spider type, Fairloc® shaft type, helical, slit-type, and neoprene flexible type couplings.
Sterling Instrument
www.sdp-si.com
Innovative Steel Bellows Coupling Released
October 26, 2009 by CouplingTips
Filed under Bellows, Featured
When first examined, steel bellows couplings seem to be the same superficially, but as one looks at the technical details, they will find there are substantial differences. The construction, structure and manufacturing quality of the steel bellows are the main factors for operational safety, reliability, service lifetime, misalignment capability and functional safety of the entire coupling. Other quality-influencing factors are the connection of the bellows to the hub components and the shaft-hub connections. They influence, for example, the transmittable torque and the coupling running characteristics decisively.
The backlash-free Primeflex steel bellows coupling
The backlash-free primeflex can be plugged in for easy installation and disassembly. It can be dismantled safely without putting the steel bellows at risk even after longer operating times. Herein lies one of the decisive technical advantages. On many other plug-in steel bellows couplings, there is a risk of damaging or even destroying the steel bellows when loosening the plug-in connection (tribo-corrosion effect on the conic hub). primeflex features specific material and geometry to fix this problem.
The extremely compact and high performance-density primeflex can be mounted easily onto the shafts via clamping or shrink disk connections. Another outstanding performance characteristic is the excellent misalignment capability of the new cost-effective steel bellows coupling. It compensates for axial, radial and angular shaft misalignments. The torque is transmitted via frictional locking or via frictional and positive locking. Furthermore, the internal mechanism integrates a stop in order to avoid bellows damages which can occur with excessive mounting pressure.
Primeflex Couplings currently come in three sizes that offer nominal torques ranging from 24 to 120 Nm. In the field of shaft couplings, Mayr power transmission has specialised in backlash-free couplings in servo power transmission services. With its steel bellows, elastomer and disk pack couplings, the company is able to provide the three most common constructional designs for this power transmission segment.
Steel bellows coupling are most often utilised to enable a power transmission between a motor and a reducer or a shaft, while allowing a correction of misalignment. The Main applications include all kind of machines (food processing, machine-tool, packaging…).
http://www.mayr.de/Startseite.1.0.html?&L=1
How to Properly Select a Bellows Coupling
October 6, 2009 by CouplingTips
Filed under Bellows, Featured
Properly selected bellows couplings result in the best control over the load in any servo application. Here are tips to ensure you choose the right size for the application.
Bellows couplings help maintain tight controls over loads.
For years, bellows couplings have been a mainstay for efficient motion systems because they offer high torsional stiffness, low moment of inertia, and minimal restoring forces under misalignment. They may help maintain tight control over loads, which is especially critical when considering that the flexible coupling often represents the point of least stiffness in an electromechanical system. In this way, couplings have a significant effect on the stability of the entire system, as well as the postional accuracy of the load. Bellows couplings benefits include misalignment compensation paired with precise transmission of velocity, angular positioning, and torque.
Most bellows couplings utilize a stainless steel tube which has been hydroformed to create deep corrugations that make them flexible across axial, angular, and parallel shaft misalignments while simultaneously maintaining the torsional rigidity inherent to a metallic tubular structure with a relatively large outside diameter. In shaft coupling applications, the stainless steel bellows absorb slight misalignments created by perpendicularity and concentricity tolerances between the mounting surfaces of the two connected components. They also absorb any axial force created by thermal expansion of the motor shaft during operation while minimizing torsional deflection and maintaining constant velocity. Exact transmission of velocity, angle, and torque, if not maintained, can compromise the operational performance of any servo motion system.
These scenarios place stress on the bellows, particularly parallel misalignment between the two shafts while transmitting torque. Lateral misalignment compensation causes the bellows to flex into an “S” shape with an angular bend at each end of the bellows that concentrates stress primarily on the end-corrugations closest to the mounting hubs. Excessive misalignment over time can harden these areas of the bellows making them brittle as they flex around circumferences. Enough torque can eventually cause the hub to tear away from the bellows during normal operation, an emergency stop, or aggressive acceleration.
Most bellows couplings use a stainless steel tube that has been hydroformed to create deep corrugations to make them flexible across axial, angular, and parallel shaft misalignments.
Torque considerations
While improved concentricity of the mounting faces of the coupled components (closer shaft alignment) can reduce lateral misalignment and ensure against failures, note that this mode of failure is closely related to the torque as well. High misalignment reduces the torque capacity of couplings. While a misaligned coupling will not normally tear until torque is applied, a precisely aligned coupling can transmit more torque than expected.
Because a range exists between misalignment and torque, bellows coupling ratings can vary. Hence, some manufacturers’ ratings are more conservative than others. For example, there are a variety of ratings for peak torque versus maximum misalignment values. Conservative coupling providers offer a shaft misalignment range in line with what the majority of electro-mechanical systems can handle, which is approximately 0.1 to 0.2 mm. Some are rated for slightly more or less misalignment. Peak torque ratings are generally similar across bellows couplings with this range of misalignment rating and a similar outside diameter. The associated torque ratings normally assume that the maximum misalignment condition will exist in the application.
This approach has been successful and normally allows for the coupling to fit well into assemblies involving the appropriately sized components. But not all coupling manufacturers use such a rating system. Some torque ratings may be inflated along with shaft misalignment tolerances. Check the documentation. Look for statements that say significant torque de-ratings must be applied in order to use a coupling’s flexibility. An improperly sized coupling can lead to significant pitfalls.
Some torque ratings may be inflated along with shaft misalignment tolerances. Check the product documentation.
Most bellows manufacturers agree on a combination of ratings that allow for a reasonable level of shaft misalignment to exist without yielding a maximum torque rating that would cause the coupling to be too large for an assembly. Some coupling manufacturers offer coupling designs with
additional corrugations and double flextures. These provide magnification of the lateral misalignment compensation within a given torque rating while maintaining a relatively high level of torsional stiffness.
Calculations to determine proper couplings
Proper bellows coupling selection should begin with a torque calculation. Quick factors to include in a bellows coupling selection are the peak torque capacity of the servo motor, multiplied by any application gear reduction ratio, and multiplied by a safety factor of 1.5. The appropriate bellows coupling should then have a torque rating greater than or equal to that of the calculated torque.
More precise calculations include the moments of inertia and actual torque required to accelerate the load by first overestimating the required torque of the application through the use of generalized service factors. Then, reduce the torque value by considering the moments of inertia of the drive and load. Inertia mismatch can be critical to coupling longevity as reflected load inertia in aggressive start/stop or reversing applications can produce significant spikes in torque. These spikes can exceed those estimated through the use of current limits into the drive amplifier.
Selection by torque is most common. However, calculating the required coupling torque rating can be skipped if their position accuracy requirements would result in a torsional stiffness value which would correspond to a torque rating in excess of the actual power requirements of the application.
A flexible coupling is typically the most compliant of components in any mechanical motion system making its torsional stiffness a critical factor in terms of maintaining positional control over the load. Since bellows couplings have the highest torsional stiffness of any servo motor coupling, they are employed in applications with high precision positioning requirements.
There are some rare cases in which the servo loop gains set high enough can result in a mechanical frequency which will excite the coupling’s natural frequency. In these instances, elevate the coupling torsional stiffness to avoid a situation where the rate at which the coupling springs back from a torsional impulse does not match when the next impulse would take place. Auto-tuning features in most modern servo drives have eliminated this potential problem for most applications. However, in some cases, this effort may be necessary. The following calculation allows for proper coupling selection based on mechanical resonant frequency.
Properly selected bellows couplings result in the best control over the load in any servo application. The selection criteria begin with ensuring that the coupling will have sufficient torque rating to accelerate the load, followed by checking that coupling misalignment tolerances are in line with practical expectations of the accuracy with which coupled shafts will be aligned.
Generally, higher misalignment tolerances can be achieved at potential compromise to torsional stiffness. However, in most applications, bellows couplings offer ample torsional stiffness. In cases where a coupling with a good mechanical fit has marginal torsional stiffness in light of stringent requirements, shaft alignment must be addressed in order to accommodate high stiffness requirements. A good rule of thumb would be to contact a coupling expert for servo coupling requirements to ensure optimal performance.
Discuss this on the Engineering Exchange:
R + W America
www.rw-america.com
Servo Torque Limiters
October 6, 2009 by CouplingTips
Filed under Featured, Industry News, Torque Limiters
Protection of an electromechanical system from torque overload is often assumed to be guaranteed by the current limits set in the drive parameters. But in the case of hard stops, impacts and other situations where overload occurs very rapidly, sufficient energy to do damage often exists in the rotating inertia driving the load.
R+W servo-rated torque limiters are accurate to +/-5% release torque and positively disengage the motor or gearbox shaft in 1-3 milliseconds. Patented pre-loads and a specially designed spring system remove backlash and guarantee a very low profile for higher release torques.
