Looking for the latest pneumatic actuator news? Look no further. Pneumatics Tips provides the most up to date news and information on pneumatic actuator products and pneumatic automation. For specific news and information on pneumatic actuator innovations, take a look at the articles below.
Roller Screw Actuators: Benefits, Selection and Maintenance
The choice of hydraulic/pneumatic or mechanical actuators always depends on the application, but if application factors are equal, the roller screw actuator has some advantages.
Roller screw actuators have several advantages over hydraulic or pneumatic actuators for many applications, especially those involving heavy loads and fast cycles. For example, the controls are simpler, eliminating the complex system of valves, pumps, filters and sensors that make up hydraulic and pneumatic systems. Other benefits include a small system footprint, long functional life and low maintenance requirements. And because roller screw systems don’t require high-pressure fluid, they reduce noise levels and are not subject to potentially hazardous fluid leaks.
inverted roller screw mechanism Rollers screws come in two basic kinds of configurations; the inverted roller screw mechanism, top, and the standard configuration roller screw, bottom.
Roller Screw Technology
Roller screws convert rotary torque into linear motion, similar to acme screws or ball screws. But roller screws can turn considerably faster and cycle more frequently than both acme and ball screws, making them an ideal fit for demanding, continuous-duty applications. Similarly sized roller screws are more efficient than acme screws and can carry larger loads than ball screws, handling loads up to 779,000 lbf.
The difference in performance is due to the design for transmitting forces. The number of contact points in a ball screw is limited by the ball size. In roller screw systems, multiple threaded rollers are assembled in a planetary arrangement around a threaded shaft, which converts a motor’s rotary motion into linear movement of a shaft or nut. The rollers feature radiused flanks that deliver point contact, similar to balls on a raceway, with only the radius near the point of contact included as part of the profile. This design allows a larger radius with additional contact points to fit into the existing space, lowering the stresses within the system and lengthening its functional life. Because the number of contact points is greater, roller screws have high load-carrying capacities, as well as improved stiffness. This typically means that a roller screw actuator takes up less space in order to meet a designer’s load requirement than a similarly sized ball screw.
Roller screws are designed to have larger radii at the point of contact, meaning that more contact points will fit within the same relative space. This lowers stresses and lengthens functional life compared to a comparably sized ball screw system, top.
High load capacities mean that roller screws have some major advantages in service life. For instance, in a 2,000 lbf average load application applied to a 1.2 in. screw diameter with a 0.2 in. lead, a roller screw will have an expected service life that is 15 times greater than a ball screw. Typical ball screw speeds are limited to 2,000 rpm and less due to the interaction of the balls colliding with each other as the race rotates. In contrast, the rollers in a roller screw are fixed in a planetary arrangement by a journal and gears at the ends, so they do not have the same speed limitations. Hence, roller screws can work at 5,000 rpm and higher, producing comparably higher linear travel rates.
Versatile nut options let you balance between backlash and load capacity demands and cost trade-offs. Some common nut configurations are the single nut, split nut and double nut designs. The most common configuration, the single nut, has a long service life and low backlash under 0.001 in. In split nut designs, the nut is split transversely and a precision-ground spacer sits between the front and back halves. The split nut configuration effectively eliminates backlash and also reduces the dynamic load rating by about 38%. As the name implies, the double nut arrangement uses two nuts preloaded against each other on a single screw. This design offers similar life expectancy as a single-nut design as well as decreased backlash, but typically costs more than a single-nut configuration.
Roller Screw Size Specification
Roller screw variables include the diameter, lead and sealing. When preparing the component specification, be sure to take into consideration the budget, maximum linear speed, maximum load, maximum stroke, necessary precision level, tolerance to backlash, the contaminants present and the needed level of protection.
A few key calculations help determine the ideal parameters for an application. For example, roller screw nut speeds cannot exceed their mechanical speed limit, which is dependant on the screw diameter and the lubrication method. Systems lubricated with oil should not exceed 140,000/do, while grease-lubricated roller screws systems shouldn’t surpass 90,000/do.
In high-speed roller screw applications, the roller screw shaft typically sets up natural frequency vibrations, which should be taken into account by calculating the critical speed. This speed is determined by the screw diameter, length, loading direction and bearing arrangement. The rotational speed of a roller screw should be kept below the critical speed, defined as:
ncrit = 86.4 x 106dofs / l2
where:
ncrit = critical rotational speed under zero axial load (rpm)
do = screw diameter, in. (mm)
fs = support bearing factor
l = screw’s length, in. (mm)
Another phenomenon to avoid is buckling. Buckling occurs when the compressive load on a screw’s shaft is too great for its diameter. The buckling force is determined by the screw length, diameter and type of bearing supporting the screw. The compressive load should be less than the buckling force, defined as: Fb = 81.3fbdo4 / l2
where:
fb = buckling force, kN
Fb = buckling force bearing factor
Another factor to consider is the motor size. A motor is selected by calculating the required torque as a function of load on the system and lead of the roller screw and comparing it to available motors and power transmission components. For applications that require a specific motor, roller screws with a lower or faster lead, belt or gear reductions can be configured into the system.
Protection and Maintenance
While correctly specified and maintained rollers screw systems can still fail from metal fatigue or abrasion of the thread flanks, other failures can typically be prevented. For optimal performance and life, roller screws, like other lead screws, should be well lubricated and must tolerate contaminants including abrasives, metal chips and non-lubricating fluids.
Although the friction created by the rolling screw design is minimal compared to sliding friction, it can still cause heat build-up, which can eventually lead to a costly failure. Lubricants should be used to dissipate heat in order to avoid wear and premature failure. In general, roller-screw life can be increased by regular grease and oil replenishment. Maintenance intervals depend on the screw size and operating conditions. Typically KP (DIN 51825) consistency two bearing grease should be applied. Some applications with higher duty cycles may need a high-performance gear oil with EP additives. Lubrication rates vary according to the screw diameter, number of rollers and the amount of heat to be dissipated.
Providing sufficient protection against contaminants is also critical to long functional life. For instance, if metal chips get into the nut assembly, the roller screws may grind them into a lapping compound, which will cause spalling and eventual catastrophic failure. Shaft wipers, bellows, shrouding and enclosures protect roller screw components from environmental contaminants, and should be selected according to specific application requirements. For example, wipers can be added to the front or back of the nut to scrape particulates from the threads throughout the screw stroke. Additionally, force tubes that house roller screws keep lubricants in, while preventing contaminant infestation. Force tubes with IP67 ratings are available in a wide array of mounting options.
Improper loading is another possible cause of roller screw failure. As a general rule, lead screws do not tolerate applied moments or side loading, so high-precision slide rails should be used to carry these loads and make certain that loading on the nut is co-axial to the lead screw.
Although roller screws may have a higher initial cost than alter-native motion actuation systems, they usually provide significant cost savings in the long run. In fact, a properly specified and maintained roller screw system typically costs half that of the cumulative cost of ball screw systems, since they do not need to be replaced or maintained as frequently.
High-Torque Actuators Are Optimized for Speed And Strength
WITTENSTEIN announced the TPM+/TPM+ High Torque sizes 300/500. These sumo-sized actuators offer maximum rigidity and the highest torque combined with WITTENSTEIN’s signature compact design.
The new sizes 300 and 500 meet the highest requirements concerning torque, compactness and dynamics. Features include high rigidity, extreme precision and excellent performance, making the TPM+ 300/500 actuators a fundamental contribution to increase the productivity of any machine.
Technical specifications at a glance:
- Torque up to 10,000 Nm
- Compact design coupling the alpha TP+ 300/500 gearbox and 220 series motors
- Optional strengthened output bearing (special gear housing)
Valve Positioners For Pneumatic Actuators
August 2, 2010 by admin
Filed under Actuators, Equipment, Positioning sensors, Valves
Spirax Sarco’s EP5 and PP5 control valve positioners operate on the balanced forced principle providing a tested solution for accurate control valve positioning. Both types are simple to commission and maintain with a low air consumption and 0,2 to 1,0 bar and 4-20 mA input signal options.SRU-plus Rotary Actuator from SCHUNK
With a new dampening system the SRU-plus rotary actuator from SCHUNK can rotate heavy loads just like its predecessor the SRU. The new unit is available in six different sizes. The user can choose between two dampening versions. The soft dampening version ensures shorter cycle times even with the same payloads; the hard dampening version enables the handling of a heavier payload with the same body size.
The completely revised rotary module series from SCHUNK has many options, including electric and fluid feed through, continuous adjustment of the end positions, as well as pneumatic or locked middle position versions. Furthermore, it is interchangable with its predecessor, which ensures a hassle free upgrade to the SRU-plus.
Linear Actuators
Linear Actuators are a class of mechatronic systems with some unique design constraints. As a result there are dozens of approaches, dozens of vendors, the option of designing the actuator from scratch, and, frankly, a lot of confusion. The problem lies in the fact that the actuator as a subassembly is the combination of a number of separate technologies. This means there are a number of design tradeoffs incorporated into the resulting actuator that must be acceptable in order to use that actuator.
Categorizing linear actuators is not entirely straightforward because many categories overlap. The “motive power” category can be any type of power source, rotary motor or linear motor powered. Linear motor solutions are much more commonplace in linear actuators today due to declining costs for this technology choice. But in a linear motor based actuator, the linear motor is both the motive power and the mechanical transmission at the same time.
Categorizing linear actuators by their mechanical transmission style is another approach. The most common categories are screw type, belt and linear motor. But the motive power for a screw based actuator could be a stepping motor or a servo motor. The stepping motor is predominant because of it’s suitability for positioning, but it may be underpowered for some applications where a servo is needed. So the linear actuator transmission category can have overlaps because of the different motor types that are used in conjuncion with it.
Price seems to be one means of eliminating the ambiguity. Stepping motor and lead screw combinations are popular because they are economical and maintaining 0.001″ accuracy is very easy. Linear motor systems are capable of .5 micron accuracy with little or no friction, acceleration and speed that is incredible, but generally the higher performance comes at a higher price.
But in the end, the selection process is best guided by the criteria of the application. The list is, thankfully, short. Load weight or force that must be generated, speed, accuracy and life expectancy or number of cycles of operation. This last is probably the key determinant in system selection. Long life or high cycling goals lead to linear motors actuators with little or no friction. You have to familiarize yourself with the overall field because the tendency of confusing the technology and the application needs.
At the recent Semicon gathering of manufacturers involved in semiconductor manufacturing, a lot of attention is given to the mechatronic content of machinery. And as far as I have been able to determine from many different market research projects, semiconductor manufacturing is one of, if not, the largest market for mechatronics every. So it’s also not a surprise that a lot of vendors come to the Semicon show with their latest and greatest product offerings.
Among the most interesting, Nanomotion continues to extend the reach of piezoelectric linear motors, yet another technology choice within the linear actuator sphere. Piezo motors have only one moving part, and meet the high precision, high reliability criteria. With increasing usage, there has been decreasing cost for this unique solution, along with superior position feedback technology and excellent packaging for space constrained applications.
In addition, IKO has released a number of new linear actuator assemblies, both screw driven and linear motor driven. They are also showing a number of unique 2-axis configurations one of which is the thickness of a tape reel and is targeted to unloading parts for electronic pick and place machinery.
Brilliant examples of manufacturers continuing to integrate mechatronic technology to make it more convenient for the customer.
Electromechanical Actuators Suit Off-Highway Equipment Applications
SKF® “drop-in” electromechanical actuators introduced for off-highway equipment applications provide easy-to-mount solutions for integration into new or existing design envelopes. These highly robust actuators ideally can perform functions traditionally controlled either hydraulically or manually.
The “plug-and-play” actuators have been engineered to promote precise and reliable movement in dozens of applications ranging from steering-wheel and seat adjustment to trailer tilting and hood lifting, among others.
Two series have been developed to satisfy medium/heavy or low-load applications. Both feature corrosion-resistant housings and durable metal gears offering the capability to withstand extreme temperature swings, vibration, shock, dust, and moisture in the field. The actuators are self-locking IP 66-rated and can operate over a wide temperature range (-40º C to 85º C).
Their use can deliver greater precision, process control, and accuracy; reduced maintenance-related downtime; diminished environmental impact with elimination of potential hydraulic fuel leaks; improved working conditions due to enhanced operator ergonomics and safety mechanisms; and increased productivity with the elimination of the need for manual operations.
This family of actuators can additionally be equipped with various options and otherwise customized for the particular application.
Humphrey Products Receives ISO-13485 Accreditation
June 23, 2010 by admin
Filed under Actuators, Equipment, Industry News, Valves
Kalamazoo, MI — Humphrey Products is proud to announce that it received the accreditation for ISO 13485: 2003 in addition to its continued accreditation of ISO 9001 status. ISO 13485 represents the requirements that medical device manufacturers must incorporate into their management, engineering, distribution and quality systems.
Adding to all the normal benefits that the ISO 9001 registration provides customers and distribution, ISO-13485 certification provides the system controls, serialization, process change controls and notification that are currently required for products used and sold within medical markets.
“The medical market is a huge and all encompassing category and can cover many and varied applications,” said Robert Humphrey, President and CEO of Humphrey Products, “anywhere from process equipment used in the automated preparation and evaluation of biopsy materials on test slides, to those applications such as oxygen concentrators used by the patient within their own homes, or all the way into the ER, and patient invasive devices used by surgeons to assist with various medical procedures.”
Humphrey Products
www.humphrey-products.com
Thermally Actuated Gas Shut-Off Valves Used To Control Flow Of Gases
Assured Automation announced the FireBag – a new line of thermally actuated gas shut-off valves used to control the flow of natural, propane or butane gases.
Many existing emergency gas shut-off devices require manual manipulation – a poor solution in emergency fire situations. The FireBag provides a solution by automatically discontinuing the flow of gas when the ambient temperature reaches 100° C (212° F). With this device, gas is automatically discontinued in fire situations to avert fire escalation and potential gas explosions.
According to the NFPA, the U.S. fire departments face 2,110 home fires a year where natural gas is the first material ignited, and 1,170 home fires a year where LP-gas is involved with the start of a fire. Most home gas fires originate in the kitchen at the stove or gas range.
The FireBag domestic product line includes:
o G4T404 for utility-supplied gas pipes, heating systems with radiant pipes, and hot air generators
o G2T50 for utility-supplied gas meters
o G4T10 for gas boilers and wall heaters
o G2T40 for gas appliances such as stoves ( ranges) and gas radiators
o G4TF for thermal stations
The FireBag industrial product line includes:
o G4T404 for varnishing and paint booths
o TASF for gas motors
o G4TF for commercial ovens
The FireBag has been used throughout the world to provide automatic thermal interruption of gas in paint booth applications, water heaters, stoves and ranges, radiator and gas utilities.
Although US fire codes and certifications for thermally activated shutoff devices currently do not exist, the FireBag conforms to internationally established codes and standards. For example, the European UNI EN 1775 Standard requires all indoor gas pipelines be designed, built and protected to prevent explosions in the case of fire as well as spreading of the fire itself. The FireBag conforms to this standard as well as the European Directive 90/396/CEE, the German Firing System Directive and DVGW TRGI 86/96. It also is certified for the German National Standard DIN 3586.
Pneumatic Feed Escapements Mount From Various Directions
AGI Pneumatic Feed Escapements come in two types and eleven sizes offered are dual timed type (AGE) and single non rotating type (AGMS). Pneumatic feed escapement actuator is ideal for singulating and release of individual parts from hoppers, conveyors, vibratory feeder bowls, tracks and magazines.
The AGE compact long stroke singulaters are internally sequenced. The cross porting makes sure both rods are extended before either rod can retract, ensuring positive part feeding and release occurs sequentially and without jamming. The AGI escapements have an easy part clearing feature due to internal back pressure cross port design, this allows both rods to be retracted with air pressure off to clear a jam.
AGMS single finger feed escapement is a double acting actuator with t-slot gib design is ideal for use in tight spaces needing large payloads. This single guided actuator has a T-slot bearing design that is supported the length of the body to handle large moments. Multiple mounting surfaces allow payloads to be attached to the top rail or the endplate. AGMS slides are offered in four stroke sizes from .25 inch (6.4mm) to 2 inch (101 mm) and have .5 and .75 inch bore sizes.
A combination of through holes and threaded holes on the escapement body allow for easy mounting from various directions. Dowel-pin holes on the body of the escapement provide for repeatable installations.
All of these units are available with sensor options for easy interfacing to electrical controls and stroke adjustments that are ideal for fine adjustments.
AGI supplies a complete range of sophisticated automation products that include: pneumatic parallel grippers, rotary actuators, thrusters, linear actuator slides, mini slides, tool changers, overload devices. The units are available in imperial and metric versions for flexibility and design for a world market.
Pneumatic Rod Lock from AME
May 26, 2010 by kremington
Filed under Actuators, Air Preparation, Equipment, Industry News
Advanced Machine & Engineering Co. announces the Fourth- Generation RLN Series Rod Locks. The new Pneumatic Series RLN Rod Lock has been developed as a solution to control problems inherent to pneumatics – over travel, drifting, bouncing and reverse traveling. The AMLOK® Power-Off Rod Lock can be mounted to a NFPA cylinder, or as a stand alone unit.
The patented AMLOK® Type RLN is constructed of black anodized aluminum housing with a special piston and wedge locking mechanism actuated by multiple springs that mechanically lock the rod quickly and securely. The clamp is unlocked when air actuates the piston, compresses the spring and releases the locking device.
–No rod displacement on engagement
–Large clamping surface reduces pressure-per-square-inch on the rod, extending service life
–Fast response time
–Low backlash
–4 bar (60 psi) release pressure
–Precision holding 0.002-0.003
–Consistent clamping force in both directions
–High cycle rates and accuracy
–Holds load during power/pressure loss
–Compact unit, easy integration
–Versatile sleeve nut/tie rod mounting to NFPA style pneumatic cylinders
–Many NFPA style-mounting attachments available for stand alone applications
The optional sealed RLN Series design is suitable for food and wash down applications as well as pneumatic and hydraulic presses, scissor-lift tables, test and positioning equipment, amusement ride equipment, printing and paper handling equipment, theatrical equipment (platforms), assembly equipment, and machine tool applications.
Advanced Machine & Engineering Co.
www.ame.com
