On 2014-06-29 14:41, Gene Heskett wrote: > On Sunday 29 June 2014 06:46:14 Marius Liebenberg did opine > And Gene did reply: >> I am finding it necessary to reconfigure my lathe as I cannot operate >> it properly as I have it setup now. I need some advice please. >> >> What I have. >> Mesa 5125 with a Mesa 7i76 > Good I believe. > >> Photo interrupter spindle speed counter > This will need to be replaced with a full A/B/X* encoder, which will give > you within its capability, all the spindle position and direction info > you'll need, and I believe the 5i25/7i76 handles it. > >> AC motor without VFD > While gear changing in the belts or back gear etc can be done, it will > need also, a means of stopping it, such as throwing a DC current thru it > to bring it to a near halt fairly quickly, (called suicide braking in some > circles) and a method in relays to run it in both directions if you want > to do rigid tapping, which will require the full A/B/Z encoder anyway. I > am using a treadmill dc motor, and a pile of ice cube relays to achieve > that control with a single quadrant controller. And my hal file may be > the longest one, its close to 300 LOC as all those direction & timing > related things are in it. I just yesterday, drilled and threaded 4, 1/2" > bits of cold roll rod to 6x1mm for the motor mount standoffs using a peck > loop using g33.1, where each time thru the loop it drove the tap 1/2 turn > deeper until I was out of tap. I could then blow the tap clean on the > backstroke, and apply a drop of cutting fluid. Ok so it looks like a VFD with a brake resistor on a 3Phase Ac motor will have to be used.
The motor is only 0.55Kw (0.73Hp) I will fit a 2Kw motor and leave the belts set to a happy middle of the road selection to get speed and torque > How many hp and what is the nameplate current draw of this AC motor? To > do the braking in a timely manner, you will need a dc supply capable of > delivering perhaps 125% of that nameplate current into what will be > essentially a dead short, and if running a peck cycle, capable of doing > that on a 40% or so duty cycle. Line voltage here can probably be done > with huge power limiting resistors, but a 12 volt supply should be > adequate as it is not the motor inductance, but the winding resistance > that counts. > > For smaller lathes, the treadmill motor and controller should be usable as > they can be had a 2hp from flea-bay. By the time their RPM is tamed and > converted to spindle turning torque, one of those can probably do about as > much real work as a 3hp ac motor. > >> Joystick type of jog > Never got around to this on my lathe, I just use the keyboard arrow keys. > Keeping key jamming swarf out of the keyboard can be a chore though as its > on the table in front of the lathe, a 7x12 very early and roughly finished > toy. > >> Gmoccapy or Gscreen > I'm still using axis so can't comment. > >> Manual tool change (tool changer to come) >> >> Seeing that I am going to redo the configuration, please tell me what >> is required to operate a lathe at best. If a VFD is required I will do >> that. I want to be able to cut using CSS and I will want to do rigid >> tapping as well. The tool changer will have a rotary tool attachment. >> What do the machining gurus suggest? > *By the A/B/Z terminology, A and B are photo-cells watching a slotted > disk, and adjusted physically so that each is seeing a slot with a 50% > duty cycle as it turns, AND the two are timed so as to be 90 degrees (not > in spindle position, but in terms of the slot signals apart. A third > photo-cell watches a longer slot and is adjusted to give a single pulse > output per revolution. From that info, linuxcnc can determine where the > spindle is, in my case with a 50 slot wheel on the rear of the spindle to > an accuracy of 1.8 degrees. With the 7i76/5i25 processing that info, the > maximum spindle speed will be well above what your lathe can turn and > tracking for the G33 stuff should be flawless. > > Others here will no doubt have other recommendations. This is how I am > doing it. There are many ways of skinning this cat. :) > > Cheers, Gene Heskett -- Regards /Groete Marius D. Liebenberg +27 82 698 3251 +27 12 743 6064 QQ 1767394877 ------------------------------------------------------------------------------ Open source business process management suite built on Java and Eclipse Turn processes into business applications with Bonita BPM Community Edition Quickly connect people, data, and systems into organized workflows Winner of BOSSIE, CODIE, OW2 and Gartner awards http://p.sf.net/sfu/Bonitasoft _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
