Siemens linear motors; Simotics L

[Sturmer]

Greetings, long time has passed since i posted my last post , but i have a question that i would like to hear from people - there experiences and thoughts.

I'm in constructing new 5 axis grinding machine, and i was presented with solution that replaces all together the need for ball-screws, bearings and servo /step motor - the Siemens linear motor solution. My question is , what are possible pit-fouls about this design? Does any of you used this motors in there construction?

Here is the link to the Siemens manual and catalog so you can have a vision of what is the use and design of this motors. I'm satisfied with the rated forces that it generates (20700 N with biggest motors !!), but as i think this is relatively new technology i would like to hear the experiences and thoughts of people that have had the contact with the technology first hand.No sales pitches and fairy tales ...

SIMOTICS L Linear Motors - English - Siemens

Best regards, and thank you in advance!

[RICHARD ZASTROW]

Look at the major tool and cutter machine builders. They all use linear motors in some models.

The only area that concerns me is in vertical applications. In case of a power failure there could be a free fall down. This would require some type of power-off brake to prevent the free fall.

Dick Z

[mike_Kilroy]

linear motors are not often used for machine tool applications for a few reasons:

1) cost. compare to ballscrew/rack-pin servo and gearbox and usually 3-8x more expensive
2) stiffness. 10,000N from screw/gerarbox/servo will usually be 10-100x stiffer than 10,000N linear motor since stiffness goes up by 4rth power(?) of gearing and linear has no mechanical advantage
3) hard to get gain up; similar to 2). you must run velocity gains 100+ times higher than servo motor for same end result gain since no mechanical advantage
4) magnetic attractive forces: a 1000# thrust motor will have 10,000# magnetic attaction you must design your bearings to handle

If you get around these design issues, you will have a machine that is 5-20x faster top speed, 5-20x faster accel capability.

[Sturmer]

As the desing has progressed , we have dismissed the lienar motors for the 5 axis milling center , but i have made the simple construction for honning machine.

Here are few images of the prefab model (a lot of things are still missing and are in the desing stage

And yes we are using the special line brakes (in case of power fail )