Ubiquitous Servos Leverage Design Flexibility

While servo motors have been successfully adapted to wide applications in various industries, manufacturers persist in expanding the flexibility of these motors. Servo motors offer sophisticated motion control over wide torque ranges in standard compact packaging. They're also available in packages that resist electromagnetic- and radio-frequency interference and stand up to a host of hostile i...


Click here to view the complete research results from the April 2004 Electric Servo Motors Product Focus Study in the Resouce Center.



  • Ethernet communications

  • Software setup

  • Networkability

  • Direct-drive capability

  • Torque motors

While servo motors have been successfully adapted to wide applications in various industries, manufacturers persist in expanding the flexibility of these motors. Servo motors offer sophisticated motion control over wide torque ranges in standard compact packaging. They're also available in packages that resist electromagnetic- and radio-frequency interference and stand up to a host of hostile industrial contaminants.

This year's look at trends in the user marketplace was done in an e-mail/Web survey of subscribers, asking them about their preferences in servo motors. The survey was conducted by Control Engineering and Reed Research—both part of Reed Business Information ( www.reedbusiness.com )—highlights of which are presented here as received from 167 respondents in January 2004.

Servo motors' ubiquitous nature is verified by survey results placing them in a wide variety of applications. Among those polled that are involved in specifying, recommending, and/or purchasing servo motors, the top four applications were: assembly lines, with 21% of users (moving up from 12% in 2003); machine tools at 16.8%; packaging machinery at 13.8% (each down from 25%); and material handling with 11.4% (15% in 2003). See 'Applications...' bar graph for other usage. A relatively large percentage of responses (19.2%) fell into the 'Other' category, indicating more nontraditional uses for these motors, for example HVAC, metrology/inspection equipment, engine dynamometer control, and prison door control. (How's that for real 'cell' control?)

Checking usage

How are servo motors being used within applications? The 2004 survey finds new applications account for 51.9% of units purchased, while retrofits and replacements comprise 19.4% and 27.9% of motors, respectively. These results were essentially identical to the 2003 survey.

Economics appear to be behind these results. When asked about CE 's survey results, Paul Derstine, motion manager for GE Fanuc Automation, commented, 'GE Fanuc also reflects a higher percentage of servo usage in new machine applications compared to retrofits. However, the economy over the last several years has reduced capital spending for new equipment, driving end-users to retrofit existing lines and achieve gains through their installed base of machines. There is [now] an opportunity for both OEMs and end-users to take advantage of the significant benefits an optimized motion control system can contribute.'

Ethernet forges ahead

Survey respondents in 2004 networked 29% of servo motors in 2003 compared to 36% in 2003. Changes in network preference also took place. Ethernet rose from the number two network in use with servos to first place over 2003's leader, DeviceNet. Of those responding, 56.1% now use Ethernet, compared to 51.1% for DeviceNet. This outcome was not unexpected. The 2003 survey indicated that percentage of those planning to use Ethernet in the future was higher than for any of the other communication networks mentioned. This trend could continue, given this year's 'plan to use' responses also indicate that Ethernet is in the lead.

Servo motors leverage a wide array of features to meet diverse applications.

Other current networking choices include SERCOS (39.9%), Profibus (35.9%), Modbus (32.4%), and Firewire/IEEE 1394 (5.9%). These rankings showed no change from the previous survey.

Apparent popularity of Ethernet for servo motor networking could be a case of users' freedom of choice outstripping availability unless servo motor manufacturers rise to the occasion.

According to Brian Casey, Kinetix business manager, Rockwell Automation, 'Currently, relatively few products in the servo drives market have Ethernet support. But it's definitely an emerging capability, with more new products being launched [in Europe]. From Rockwell Automation's perspective, standard Ethernet technology will continue to evolve and be able to provide a solution for some portion of the motion control space, initially for controller-to-controller synchronization.

'With advancements like the IEEE 1588 standard, more of the values and features that customers associate with Ethernet will remain available, even for more demanding motion control applications. We expect to see the convergence of Ethernet networks for general automation and motion applications over the next few years,' Casey adds.

Performance features matter

'Software for setup/tuning' remained the top-rated performance feature, receiving the most 'very important' marks in the 2004 survey as it did in 2003. However, high continuous output torque and high torque at low speed , simply switched positions from their 2003 ranking to 2ndand 3rdplace, respectively, in the 2004 survey.

Among other 'very important' performance features, survey respondents raised their interest dramatically in direct-drive motors (no speed reducer or gearbox needed). Placing near the bottom of desired features in 2003, direct-drive capability moved up to fifth place in the current survey.

According to Martin Gertz, product manager, motion control drives and motors, at Siemens Energy & Automation, 'Siemens definitely sees more requests for information on torque motors, especially in the packaging and plastics industries. There are three main reasons to get rid of the gearbox. First, backlash is reduced and accuracy is increased. Second, eliminating the gearbox reduces package length. Finally, it reduces equipment costs. One thing to keep in mind about a torque motor: it's a very stiff and tight system from a control point of view. Users need to look more at the mechanical side—a mechatronic approach—when designing the machine.'

Servo motor products

For more manufacturers, visit www.controleng.com/buyersguide . For system integrators go to www.controleng.com/integrators . Also visit company Web sites.

Meeting food, beverage packaging demands

Designed for the harsh environments of food/beverage packaging and handling applications, Allen-BradleyMP-Series Food Grade Motors enable OEMs to use high-performance servo motors for improved product throughput, machine flexibility, and precision. These servo motors feature advanced sealing techniques and non-corrosive food-grade fasteners and coatings for extended performance. Available with continuous stall torque of 1.6 to 19.4 Nm (14-173 lb-in.), MP-Series motors include a shaft seal with a hardened wear sleeve for long life. Special IP67-rated connectors can be rotated 180 deg without using tools to allow optimum positioning and no risk to seal integrity. Food-grade grease and chip-resistant food-grade epoxy paint allow users to mount the motors above the food line for installation flexibility. www.rockwell.com . Rockwell Automation

Brushless servo line expands

BSM C-Series brushless servo motors are packaged in a smaller size than previous models—up to 2 in. (50 mm) for some motors. The units also provide up to 50% higher torque than their predecessors. Now available in three frame sizes, C-Series provides up to 780 lb-in. peak torque and 260 lb-in. (30 Nm) continuous stall torque. Speeds up to 6,000 rpm are standard. These motors are suitable for a wide variety of controls, including 115, 230 or 460 V ac. An extra high insulation safety protection system is a standard feature. All motors meet UL, CSA and CE standards.
www.baldor.com Baldor Electric

Geared servo motors introduced

Siemens Energy & Automation has unveiled its new series of 1FK7 geared servo motors. It combines the benefits of Siemens' 1FK7 CT synchronous servo motor with directly mounted helical, offset, bevel, or worm gears. The 1FK7 servo motor series features a complete bandwidth of gear types and ratios, as well as mechanical mounting options. The series broadens the range of Siemens geared motors for all applications.
Siemens Energy & Automation

Eliminate costly 'custom' products

Kollmorgen AKM servo motors offer an electromagnetic design with a global feature set. Available in more than 12,000 standard offerings, they allow users to specify the exact servo motor solution needed. This includes availability of 7 frame sizes with 25 stack/frame combinations, 77 standard windings, and 19 mounting patterns. AKM servo motors also offer multiple connectivity and feedback options, as well as shaft seals and integral brakes. They produce continuous torque in the 0.2-53 Nm range and can provide speeds to 8,000 rpm. Motors are uL, cUL, and TÜV listed, and carry the CE mark.
www.danahermotion.com Danaher Motion/Kollmorgen

New servos are compact, powerful

GE Fanuc has introduced new Alpha is Servo Motors, which combine compactness with high speed and power. Alpha is servos have a torque range of 2-1,000 Nm and run on 240 and 440 V ac input. Other features offered include smaller frame size, increased maximum speed and acceleration rate, less rotor inertia, and higher Pulsecoder resolution. The compact Pulsecoder provides very high resolution at standard 1,000,000 increments/rev and optional 16,000,000 /rev.
www.gefanuc.com GE Fanuc Automation

New generation motors offer high speed and torque

IndraDyn H synchronous motors from Rexroth are kit units optimized for high torque without compromising high speeds. They consist of a three-phase wound stator and a permanent-magnet rotor. Extremely wide constant-output-power (field-weakening) range, short speed ramp-up time, and low rotor temperature make these motors ideal for main spindles and other high-speed applications. IndraDyn H can provide up to 6,500 Nm torque and achieve speeds of up to 30,000 rpm. Acceleration is up to 2.5 times faster than for comparable asynchronous motors. An innovative cooling system, enclosed within the stator, reduces costs and work for the machine builder while maximizing cooling efficiency.
www.boschrexroth-us.com Bosch Rexroth

Small, economical servos

NT Motors are small, economical servo motors with high acceleration and very low inertia. 'High-motor-slot-fill' and 'flux focusing' technology reportedly enable NT motors to produce over 30% more torque, while being 20% smaller than conventional 2- and 3-in. servo motors. Other benefits of the patented design are low cogging torque (&1%), reduced flux leakage, and lower I
www.emersonct.com Emerson Control Techniques

Direct-drive servo motors

Expanded Sigma Series servo system now includes direct-drive SGMCS servo motors providing up to 5,310 lb-in. peak torque and up to 500 rpm maximum speed—without gearboxes—by using advanced motor design and amplifier power electronics. SGMCS servo motors come in six frame sizes, 17 models ranging from 5 lb-in. peak torque in a 135-mm diameter package to 5,310 lb-in. peak torque in a 360-mm diameter unit. Other motor features include high-precision 20-bit (1,048,576 ppr) resolution feedback; low noise, no backlash, gearless, compact construction; and open central space for wiring and piping.
www.yaskawa.com Yaskawa Electric America Inc.

Brushless servos meet demanding applications

SMB Series rotary servo motors reportedly combine high-performance segmented stator design with competitive pricing for today's demanding servo applications. An eight-pole segmented stator architecture produces extremely high torque values per motor volume. SMB Series is offered in five frame sizes ranging from 60 to 142 mm and is available with resolver, quadrature encoder, or high-resolution SinCos feedback devices. Additional features include 1.7-19 Nm continuous torque range, and IP64 enclosures rating.
www.parkermotion.com Parker Hannifin Corp./Compumotor Div.

Higher voltage, more capacity

MR-J2 Super (MR-J2S) ac servo product line now includes a full range of 380-480 V ac models. With this addition, the family now covers 50 W to 55 kW capacities. Also included are standard high-resolution absolute encoders and MR-Configurator, a Microsoft Windows- based set-up software. Control options include analog speed, analog torque, and pulse-train position. All motors are UL- and CE-compliant.
www.mitsubishielectric.com Mitsubishi Electric




Low-cost, single-phase servos

Smartstep servo motors and drives are said to be easy to set up via simple, front- panel adjustments. Operating from single-phase power input, Smartstep motors provide constant torque throughout their entire speed range, and momentary torque 300% of continuous torque, which prevents slipping from high continuous loading. These motors assist in their own troubleshooting and maintenance by displaying an alarm number, indicating cause of a fault. Drive features include autotuning capability.
www.info.omron.com Omron Electronics LLC

Click here to view the complete research results from the April 2004 Electric Servo Motors Product Focus Study in the Resouce Center.

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