On Friday, November 18, 2011 12:10:04 PM [email protected] did opine: > Thanks Gene, > > That's very helpful. Sounds like you've covered a lot of ground that > I've just begun to explore. But I've just about concluded what you > suggest: designing a 2 motor spindle drive that uses the reqular DC > spindle motor for turning, and a stepper for threading, with some way > to keep them both premanently mounted and clutch between them. > > I may even incorporate Sherline's manualy turned threading attachment > > http://www.sherline.com/3100inst.pdf
Interesting, and an excellent tome on the subject, applicable to most any lathe. One big enough to run with emc would be a definite plus. My 7x10's carriage would need a quite major redesign to carry enough motor though. I have considered rear mounting a 50oz and extending its shaft alongside the cross slide to a stepdown pulley driving the front end of the cross slide screw, which would balance the weight it would have to carry. Some sort of a push-pull dog clutch to disengage it for manual feed could be built into the extension shaft. Warning, my thinking can be dangerous. :) However, for a mill, it would be so much easier to do the stepper spindle and let emc do the change gears math. Or to put an encoder on the existing spindle. Either way emc can maintain the sync. > and let it control the pitch with the spindle stepper only controlling > the number of turns. > > If I'm successful, and sufficiently pleased with the results, I'll bring > it to Cabin Fever this year. Perhaps I'll see you there. I have been meaning to hit one of those at some point before I fall over for good, when & where is the next one? Maybe I could even bring my Rube Goldberg contraption, if I could get it clean enough to display that is. Sorta show off what can be done with a micromill. Tables rent for ? > Best, > > David Clark in Southern Maryland, USA > > ----- Original Message ----- > From: "gene heskett" <[email protected]> > To: [email protected] > Sent: Friday, November 18, 2011 11:31:30 AM > Subject: Re: [Emc-users] Stepper Spindle Drive > > On Friday, November 18, 2011 10:07:55 AM [email protected] did opine: > > Hello Group, > > > > I have machined or purchased the necessary parts to duplicate > > Sherline's Stepper Motor Spindle Drive Conversion Kit, P/N 6500 > > > > http://www.sherline.com/6500pg.htm > > > > I have all the mechanical parts together, and all is running well. > > Using the standard Sherline controller and EMC2 with the supplied > > Sherline files, I'm able to go through the motions of cutting > > threads. It remains to be seen if adequate torque and accuracy are > > obtainable. > > That is a #23 framed motor good for 120 oz/in. A bit puny for a spindle > IMO. #23 framed motors are available for up to 430 oz/in. I got a 4 > pack of them some time back from xylotex. I have one on my Z axis > which seems to be able to turn nearly as fast as the shorter > (lengthwise) 225's on the XY. With a 17/42 stepdown to a 10 tpi screw, > 34 ipm can be had. XY can do about 22 ipm on 20 tpi screws > > > Is there a way in EMC to command one stepper to run continuously at > > high speed to drive the spindle, while the other 2 are running a > > normal 2 axis lathe turning profile? > > An interesting question, and not that I know of. The problem is likely > one of overflow in the emc internal counter, at which time emc has > obviously lost track of where the spindle is, but not a concern for the > relatively few turns a threading operation would be. The larger > concern to me would be the loss of torque and stalls under load when > spinning at the higher speeds. A spindle stall that was not detected, > and without encoders feeding back it won't be, will equal a lot of > broken, and expensive, solid carbide tooling, not to mention the > wrecked parts as the stationary bit digs into the part before it > breaks. > > I have wished for that in driving my rotary table when I have it setup > like a lathe head, but have had to settle for driving it a few thousand > degrees, first one direction, then the other. Geared 90/1, there is > nothing 'fast' about it, but I can put a dremel diamond disk in my > spindle and do a quite good job of polishing to exact size. A lights > out operation obviously. > > This is not a problem when only turning a few dozen turns like a > threading operation. > > I believe in your case, I would obtain enough parts to build a complete, > and then quickly interchangeable spindle assembly so that threading > could be done with this assembly, and normal milling done with the OEM > setup. > > It is something I have considered for mine, but I have only gone so far > as to purchase another Z axis casting, with thoughts of machining a > stationary new spindle right into the casting. Something with R8 > tooling perhaps. Then I start looking at the short ways, and get > discouraged, it needs another inch of way length on both top and bottom > as the existing lashup allows it to rock slightly. Cheap is cheap > regardless of what one pays for it. And an HF micromill pretty well > defines the word... :( > > > Thanks, > > > > David Clark in Southern Maryland, USA > > I am not that far away, N. Central WV, Weston TBE. It is about 3.5 > hours to Harrisonburg from here. > > Cheers, Gene 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> If food be the music of love, eat up, eat up. ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
