On Tue, 2009-09-29 at 17:43 +0100, Andy Pugh wrote: > 2009/9/29 Dave Caroline <dave.thearchiv...@gmail.com>: > > > > do you need one of use to make/cut a disk > > My machine has a milling head and a 4th axis, so making my own is > fairly straightforward (But thanks for the offer). > However I run the risk of doing a lot of machining and still having > exactly the same problems if it turns out that the paper encoder is > adequate and that the problem is elsewhere, or if I choose my encoder > resolution unwisely. > > The simplest solution would be to machine a series of slots in the > lathe spindle drive pulley face, I think. (my encoder uses reflective > sensors, I just need to check that there is enough contrast between > cast-iron and no cast-iron. > > My system seems to track a 50-line encoder adequately, would that > nromally be considered enough resolution for threading?
My guess is that a fifty line (200 pulses per rev) should be plenty. The spindle doesn't usually change speed very quickly so you can put your counting function in the servo thread, or maybe create a slower thread, which will allow many pulses to be counted per thread cycle. This will average out a lot of encoder jitter, if there is any. The more counts per cycle, the better, so you can get better resolution at very slow speeds, but watch out for the high end pulse rate, which I think you addressed already. With HALscope, you may have to run the scope at the base rate to see the jitter from your encoder. I still think your threading problem is due to the Z acceleration issue. You may try cutting an air thread that is as long as your Z axis will allow. If your thread wanders the same across the thread then I would look into your encoder more. If the wander settles to a perfect sync to your spindle, then look at the accel problem. Hopefully, someone will correct any errors I have made above. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ Come build with us! The BlackBerry® 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/devconf _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
