On Mon, Sep 10, 2007 at 10:28:37PM +0000, Neil Buck wrote: > I'm half way through retrofitting a Cincinnati VMC with a MESA m5i20 setup. I > would welcome some advice as to the best way to control the spindle. My goal > is > to be able to do rigid tapping and fully automatic tool changes. My thoughts > are > that since I am planning on adding a 4th rotary axis very soon I would like to > not use the remaining spare axis on the m5i20 card. So I was thinking about > using one of the digital outputs via a PWM HAL component. Then filtering the > output with a simple RC low pass filter to provide the analog 0-10V that the > spindle drive requires. The direction control is trivial using 2 relays driven > from a couple of digital outputs. I wonder would this setup provide a command > signal accurate enough for rigid tapping - or would it even matter given that > the spindle generates an index pulse. Incidentally the spindle also has an > output that indicates when the spindle is upto the requested speed, I was > wondering whether it's worth using it or whether it's overkill.
On the Mazak at cnc workshop, we were tapping at 300RPM. EMC2 switches the commanded speeds between +300 and -300 at the bottom of the tap and expects the spindle to decelerate and reverse in a controlled fashion. If your spindle drive can do this (you can test with S300 M3, then M4) it will tap just fine. You should pick a speed that allows the spindle to reverse in "a few" turns. You can read about the exact operation of the rigid tap cycle here: http://www.linuxcnc.org/docs/devel/html/gcode/main/index.html#SECTION00340000000000000000 I think you can get by with filtering some PWM output. For the NIST lathe spindle I did that with a parallel port output pin. But, that motor control had a 0-5v analog setting and did not have to reverse. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
