Mark Cason wrote: >On 10/27/2009 03:27 PM, Chris Radek wrote: > > >>On Tue, Oct 27, 2009 at 02:54:53PM -0500, Mark Cason wrote: >> >> >>> OK, here come stupid question of the day... >>> >>> Why does it matter if the encoder tells the computer which direction >>>the spindle is turning?? Or is this just a side effect of quadrature. >>> >>> >>> >>For lathe threading you don't need to know it. For tapping you >>do. >> >> >> > That part I understand, but, if a spindle is under computer control, >then the computer should already know which direction the spindle is >turning, right? > > No.
The computer knows which direction it *wants* the spindle to turn. When doing rigid tapping, the spindle is first run forward, then is commanded to stop and turn backwards. The computer can't tell when the reversal takes place unless the encoder feedback provides that information. The reason is that the computer will be commanding a zero or negative spindle speed, but the spindle will take time to decelerate and then accelerate in the opposite direction. All the while, the PC is commanding reverse rotation, but it can't be assumed that the spindle is turning in the requested direction. - Steve ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
