On Wednesday, January 18, 2012 12:16:45 AM cogoman did opine: > > Could you give me some idea of what the advantage is of using 2 and 3 > > > > > stack steppers? > > Perhaps I'm in over my head here, but I'll share what I think I > know. The tendency for 2 to 3 stack steppers is for the magnetic > circuit inside to get too long, and create high inductance for the > amount of field strength it produces. This limits the top speed of the > stepper (the assumption here is standard 200 steps per rev steppers). > There's a point where stepping up to a NEMA34 from a NEMA23 will get the > torque needed with less inductance, which allows for more speed. > This, is more theoretical than practical, since it is quite possible > to design a slow stepper in both NEMA23 and NEMA34 sizes, and many do > just that. While a fast stepper motor needs to have less than 3 mH > inductance per coil, I have seen even small steppers with over 10 mH. > > Rexstep stepper motors > <http://www.homeshopcnc.com/index.php?option=com_virtuemart&page=shop.br > owse&category_id=1&Itemid=1> and usa stepper motors > <http://www.usautomation.com/StepMotors.aspx> seem to have low > inductance per torque, assuming you can trust their specs. > > This one > <http://www.mpja.com/62V1A18-Deg-NEMA-23-Step-Motor/productinfo/17455+MS > />, and this one > <http://www.mpja.com/78V2A18-Deg-NEMA-34-Step-Motor/productinfo/17457+MS > /> seem to have too much inductance for fast operation.
Probably one of the reasons Marlin has those at what looks like a decent price. TANSTAAFL applies. > So practically > speaking, you need to evaluate each motor separately. That takes some knowledge of the motors else you don't really know what is important for a given job. Frankly I am not beyond that stage myself. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> She always believed in the old adage -- leave them while you're looking good. -- Anita Loos, "Gentlemen Prefer Blondes" ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
