eDrive - Summer 2013 - (Page 28)

Case Study New Linear Motor Designs Improve Speed and Positioning Multiple Design Offerings Permit a Variety of Configurations Linear motors enable maximum precision and dynamic performance in various motion control tasks. These include not only rapid traverse, but slow constant speed traverse of machine heads, spindle slides, tool management systems, part handling devices and more. There are considerable cost savings to be realized when various mechanical components are replaced by simple and efficient linear motors. These motors provide a total drive system, offering reliability, precision, high dynamic stability, low maintenance and improved production time. What is a Linear Motor? The rotary electric motors with which we are so familiar contain a circular electro-magnet called a stator. In a linear motor, the electromagnet is built the same way, only flat as if it were unrolled. The rotor is also built the same way, unrolled or flat. When the electromagnets of the primary are energized, they attract the secondary sections and push the motor along. The more current applied, the stronger the magnetic field and the more force the motor generates. Visualize a wooden roller coaster at your favorite amusement park. To get the train up the first hill for that “big drop”, we roll to the base of the hill where a chain drive, driven by an electric motor, gearbox and sprocket, clanks and jerks the train to the top of the hill. Now, imagine a ride a modern roller coaster with linear motors. Feel that sudden burst of acceleration as you leave the station? Enough force can be generated to propel the train over the first hill and through that first scary loop. Booster “shots” of force can be used at various points to maintain the train’s speed, as it rolls through loops and turns never before possible with older designs. Finally, you feel the braking action at the station by…you guessed it, a linear motor. What stopped the wooden roller coaster? Remember the guy at the station pulling a big lever? Linear motors are simple. Two main components, the primary containing electro-magnets and the secondary with either permanent magnets or magnet-free, drive the moving member. Gone are servo motors, resolvers, tachometers, couplings, pulleys, timing belts, ball screws and nuts, support bearings, lubrication systems and cooling systems. Gone also are systems that used hollow ball screws with coolant systems for thermal stabilization. Gone are rack and pinion systems that used expensive 28 Summer 2013 torque motors and/or gear boxes. Gone also are chain drive systems requiring high torque hydraulic motors with associated power units. So other than eliminating expensive components, what do we gain? The advantages of linear motors in machine applications include: • Outstanding dynamic response • High acceleration/deceleration • High traverse velocity over long distances at constant speeds • Backlash free positioning; no longer any need for “Ballscrew Compensation” • Easy installation with a minimum of components • Contactless drive with no mechanical wear • Design flexibility; primary sections can be stationary or moving With the recent introduction of its 1FN6 linear motors, Siemens now offers three models of Linear Motors for integration with all Sinumerik or Simotion control systems using Sinamics drives. Linear scales for position and velocity feedback are available from a variety of third party suppliers to suit the application. These linear motor models offered by Siemens are as follows. 1FN3 Peak Load Motors: Offer short time, high acceleration/deceleration and velocity rates comparable to S3 duty. Can be used for horizontal or compensated vertical axes. The 1FN3 offers Nominal Force (Fn) of 8,100 N, a Maximum Force (Fmax) of 20,700 N, a Maximum velocity of 253 m/ min, and liquid cooling. 1FN3 Continuous Load Motors: Offer long poweron duration for horizontal, inclined or compensated vertical axes. They are comparable to S1 duty and have Nominal Force (Fn) 10,375 N, Maximum Force (Fmax) of 17,610 N, have a Maximum velocity of 129 m/ min, and offer liquid cooling. 1FN6 Magnet Free Secondary: Suited for long traverse lengths at high acceleration and velocity rates. They can be magnet free secondary and air convection cooled design. They can be used for horizontal, inclined or compensated vertical axes. The 1FN6 offers Nominal Force of (Fn) 2,110 N, a Maximum Force (Fmax) of 8,080 N, a Maximum velocity of 532 m/min, and include air convection cooling. Siemens Article Continued on Page 30 www.e-DriveOnline.com http://www.e-DriveOnline.com

Table of Contents for the Digital Edition of eDrive - Summer 2013

eDrive - Summer 2013
Installing an Energy-Efficient Motor Helps Reduce Losses While Increasing Profits
Volatility and Oversupply: Why the Motion Control Market Underperformed in 2012
Model-Based Development of Motor Drive Controller for Hybrid Electric Vehicles
Motors & Drives
Motion Control
Components
Industry News
New Linear Motor Designs Improve Speed and Positioning
Marketplace

eDrive - Summer 2013