The motion control industry is moving forward on several fronts, providing dramatic size reductions while also making significant improvements in resolution. Product introductions at this year's National Design Engineering Show (NDES) also highlight trends toward servo motors, open standards, and greater power.
NDES exhibitors are addressing many different aspects of motion control, with products that range from complex integrated motors and controllers down to simple yet critical components like bearing washers. In many of these fields, there is a common theme: reducing size. With higher level products, that's often done by blending two elements into a single package.
That's the tack taken with the latest addition to the MDrive line from Intelligent Motion Systems Inc. IMS; (www.imshome.com), which integrates a fully programmable motion controller into the motor package. The MDrive34 even includes an optional encoder inside a package that's no larger than models without the electronics. Including electronics reduces external wiring, which has benefits beyond eliminating the headache of connecting the system. "Reducing wiring contributes to the noise issues that are needed to get certified," says Steve Bolvschak, eastern sales manager at IMS. System developers can also add a closed loop control, which adds a 512-line encoder with index mark inside the MDrive34. Adding the closed loop controls permits stall detection and position maintenance.
The standard MDrive34 offering includes four 5 to 24V I/O lines, a 10-bit analog input, 0 to 5 MHz step clock rate, and an instruction set. Resolution goes as high as 51,200 steps per revolution. In 100-piece quantities, the MDI3424 model sells for $317 each.
Northrop Grumman Poly-Scientific (www.polysci.com) is also following the integration movement, melding drive electronics into brushless dc motors. In addition to saving space compared to motors that require external control electronics, the BND12 and BND23 motors simplify installation. The motor, drive, and feedback connections are all pre-wired internally, eliminating the interconnection issues involved with external controls.
"One of the obstacles that has slowed acceptance of this technology is that drive electronics have been a separate item, so they required extra effort to set up. If there were problems integrating electronics and motors, you could get finger pointing," says Paul Murphy, sales and business development manager at Poly-Scientific. The two Poly-Scientific motors, aimed at medical markets, reduce downtime and maintenance compared to stepper motors. Additionally, they offer low audible noise, long life, and efficient operation.
Integration is also important with discrete products. Smaller size is the major benefit of a linear encoder from Sony Precision Technology America, Inc. (www.sonypt.com). The BL55 Laserscale uses Sony's new optical integrated circuit to shrink the size of the reader head, which trims the overall unit size. The Sony line, targeted primarily at semiconductor manufacturing and inspection, meets the industry's requirements for linear motor applications with a response speed of 3,000 mm/sec (analog signal, 0.4-Ám resolution). It has three different output signals: 0.4-Ám analog output (sine wave signal), 0.1-Ám/0.05-Ám A/B phase output, and a high resolution 0.01-Ám A/B phase output.
Engineers who get these products work together are also interested in making their facilities run smoothly. Hoping to help in this regard, Bosch Rexroth's Electric Drives and Controls division (www.boschrexroth.com) is focusing its efforts on open standards as a pathway to shorter changeover times and improved accuracy for servo systems. Its VisualMotion control and drive system employs a number of common standards such as Ethernet TCP/IP, Profibus-DP, DeviceNet, Interbus, ControlNet and RS232/RS485.
Providing this broad array of interface techniques will make it simpler to integrate the drives and controls into new designs or upgrade existing plants, the company claims.
The control hardware includes a combined motion and logic controller that operates on up to 40 axes of motion. Up to 32 controllers can be synchronized to operate together so that more than 1,200 servo axes can be synchronized. The VisualMotion drives have popular power ranges from 0.1 to 600 kW.
Steppin' out queen.
While there's a big trend towards servo motors, manufacturers of stepper motors aren't falling off the technology treadmill. Stepper motors often provide lower costs than many types of servo systems, so they won't disappear any time soon. If NDES introductions are any indication, product development in this area shows no sign of fading.
Nyden USA (www.nyden.com) is extending its Five-Phase Motion Control offerings with the PCE High Torque Motor Series. The line has almost double the torque of its predecessors. That is accomplished by increasing the operative power generated between the intensity of the stator pole and magnetic flux of the rotor. As part of that improvement, Nyden employs a high permeability steel within the motor's stator flux.
The motors provide nearly 900 ounce-inches holding torque without a gear reduction system. Resolution is 500 full steps per revolution and 1,000 half steps per revolution.
Ranging in size from 33 mm in NEMA size 17 to 98 mm for NEMA size 34, the motors have high running speed and very low vibration. The PCE line uses a new design approach, installing a separator between the motor's coil, stator, and phase supply. This technique provides dramatic improvements in safety, increasing the motor's dielectric strength to 3,000V, triple its predecessor's rating. The family also boasts an improved seal that keeps out dust and moisture, while the exterior is made with an improved cast iron.
In applications that require even finer resolution, the PCE motor line can be linked to Nyden's NanoDrive drivers, which let the motor run with up to 500,000 steps per revolution. The INS50 provides that capability for ac applications, while the INS500 fits in dc products. Both versions have 16 resolution settings that can be programmed from 1/1 step to 1/1,000 step. They can drive any Nyden motor. The drivers employ a torque chip that monitors heat, prolonging product lifetime. An internal cooling fan helps keep the drivers from shutting down due to excessive heat.
Addressing all needs.
Though much of NDES' focus is on highly integrated products, design engineers know well that it takes quite a few pieces to make a full scale product. A number of seemingly minor components are important elements for those who take the big picture view of design. Products like bearings, simple motors, and guide rails are also critical to the success of complete systems.
THK America (www.thk.com) has incorporated its caged ball technology into guides and actuators targeted at the packaging and medical equipment industries, as well as machine tool equipment. These SHW guides have wide rails and a low center of gravity, making the line useful in applications that require a low profile. As with other THK products, the SHW line uses the company's Caged Ball technology. The balls are isolated by a cage so they don't impact free rotation, reducing friction as well. The cage also serves as a reservoir for lubricants, reducing maintenance time and effort.
In the SHW line, torque deviation is only a tenth that of standard LM guides, improving positioning accuracy. Another THK introduction is the SKR line, which provides improved rigidity and reduced noise levels for applications that require outer rail lengths of 150-740 mm with stroke ranges of 55-608 mm.
Bosch Rexroth is expanding its Star Compact Module line, unveiling a unit that is designed for high travel speeds over long distances. The CKR member lets users of the company's Ball Rail System and Ball Screw drives run at up to 5 m/sec at lengths up to 5.5m. Motors can be mounted with either front-mounted gear reducers or side drives with a timing belt. Various reduction ratios are available in either configuration.
Production systems often require a number of different types of motors. Engineers who need to drive conveyor belts may want to take a look at a line of gearmotors by Groschopp (www.groschopp.com). These boast lower operating temperatures and higher torque. Two motors in the new family offer a modular gearhead reducer that can be used in a wide range of automation and conveyor applications.
While many vendors use grease in their motors, Groschopp uses a synthetic oil which helps the motors run cooler. In addition, the line has gears with more face width than some competitors, giving more torque than comparably sized motors. A model with 5/8-inch output shaft and nine ratios in four stages will give continuous duty torque of up to 2,220 inch pounds.
Though tiny electronic products are highlighted above, other compact components are often overlooked. But that doesn't mean they aren't important. In the category of often-forgotten parts needed in many moving systems, igus Inc. (www.igus.com) is bolstering its line DryLin R low clearance linear bearings. A low profile version of the bearings can be used in applications with as little as 0.02 mm of available space. The line is designed to replace bronze parts, offering a lubricant-free alternative that requires no upkeep.