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Technology

Maglev Chip Finds Niche in Power Tools 87 87

andhar writes: "This story in the Financial Times just goes to show you that it's often not the sexiest application of a technology that makes the best business sense. 'Today, while "maglev" trains remain a technological curiosity, linear motors are being quietly exploited in the less obviously glamorous field of machine tools. One of the leaders in such applications is Forest-Liné, a French company that makes products vital to the competitiveness of much larger industrial businesses' My margaritas want a maglev blender!"
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Maglev Chip Finds Niche in Power Tools

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  • by e7 (117450) <webmaster&spazquest,org> on Tuesday July 16, 2002 @05:58AM (#3892587) Homepage Journal

    Rock-solid slides for milling machines would rock the world. No, it ain't a sexy application, but it brings us a step closer to the ideal manufacturing scenario, where mechanical parts can actually be CNC-milled before they're even designed.

  • Yawn (again) (Score:2, Informative)

    by Pig Hogger (10379) <pig@hogger.gmail@com> on Tuesday July 16, 2002 @08:40AM (#3893138) Journal
    Nothing new there. Is Slashdot a nostalgia technology site????

    More than 20 years ago, I remember seeing at a computer show a daisywheel printer whose head was propelled by a linear motor (it was manufactured by a subsidiary of Exxon).

    And in 1984, in Toronto, the Scarborough RT (Rapid Transit) line [metropla.net] opened, which was the first full scale ICTS implementation [inter.net]. Since then, the small linear motor subway has found home in Vancouver [inter.net] and Detroit [presby.edu].

  • by redtoade (51167) on Tuesday July 16, 2002 @10:37AM (#3894045) Homepage Journal

    "My margaritas want a maglev blender!"

    There's a difference between levitation and propulsion.

    From the Financial Times article: "Linear motors are "flattened out" versions of conventional rotary motors. As their name implies, they promote linear motion - of the kind required in many kinds of machine tools that use a large number of sliding and shuttling actions, fundamental to the job of cutting metal."

    Linear motors are just rotary motors cut and laid out flat... or another way to explain them is a rotary motor of infinite radius.

    "Maglev" is obviously short for magnetic levitation. Linear motors are common in maglevs simply because there is an air gap between the vehicle and the track. It would be very difficult to use conventional motors in such a system whithout driving wheels (or mechanical friction). However, other types of propulsion can also be used... such as jet engines, solid rocket boosters, etc. Although perhaps not practical for commercial trains, a maglev with rocket propulsion could be used for launching scram jets from the ground.

    Linear motors can be used without magnetic levitation. It is completely feasible to use a linear motor on conventional wheeled "people movers." Although this application is rare since linear motors typical consume more energy than rotary motors.

  • by Samedi1971 (194079) on Tuesday July 16, 2002 @10:50AM (#3894153)
    Rock-solid slides for milling machines would rock the world.

    Quality milling machine slides are already rock-solid. The gain from linear motors is speed. As the article mentions, this can benefit very large milling operations like milling a long slot in an aircraft wing. In most milling operations, torque is more important than speed, because you've got to keep the work stationary against the cutting forces.

    If you really want speed in a CNC machine, just gear the servos or steppers up instead of down. It'll work great as long as you keep your cuts light.

    No, it ain't a sexy application,

    CNC is always sexy!

    but it brings us a step closer to the ideal manufacturing scenario, where mechanical parts can actually be CNC-milled before they're even designed.

    I doubt these linear motors run fast enough to travel in time.

  • by cutecub (136606) on Tuesday July 16, 2002 @11:27AM (#3894522)
    Brother Typewriter had a product in the mid 80's called the Brother EM-1 electronic typewriter. The print carraige rolled back and fourth on a Linear Moter.

    It had the advantage of having no belts or pulleys. Nothing to tighten or replace. It couldn't get out of alignment.

    They abandoned it in later models for a wire pulley system. I guess the fact that it sounded like a BART train freaked people out.

    -Cutecub
  • by gessel (310103) on Tuesday July 16, 2002 @02:57PM (#3896419) Homepage
    They're not "new," we used Anorad [anorad.com] linear motors back in college too many years ago to remember, back mapping the EMF using a sub-nanometer resolution laser interferometer to improve the velocity and position accuracy (they've been around since the '50s).

    Currently I help design machines that use a mixture of linear motors and ball screws as appropriate. In applications with high linear speed, short/medium stroke, and no static hold requirement, linear motors are a good choice.

    If you move slowly, that long chain of rare earth magnets isn't a good investment compared to a ball screw (but the ones that came out of a linear motor we broke that are on my refrigerator really impress people.)

    If you need a long stroke, that chain of magnets gets very expensive ( though they're used for elevators sometimes. [fujitec.co.jp]) On the other hand, ball screws can be limiting in applications requiring long length as the driven mass increases linearly with the length of the drive, not the case with a linear motor.

    If your application requires extended static holds, then a ball screw is a lot easier to integrate.

    For most machine tool applications they aren't really a good choice (since machine tools typically have feed rates and target accelerations well suited to ball screws) but a number of companies do build machines with linear motors [google.com] for one or more axis, and they tend to dominante the "ultra-high speed machining market."

    This [moldmakermag.com] is a decent comparison of the strengths and weaknesses of the two dominant linear motion technologies for the curious.

    Now if you want a really new technology for linear motion appropriate to high accuracy machining, then what you really want is hydrostatic leadscrews and bearings. [machineshopguide.com]

In practice, failures in system development, like unemployment in Russia, happens a lot despite official propaganda to the contrary. -- Paul Licker

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