On Fri, 2009-06-05 at 15:32 +1000, Erik Christiansen wrote: > On Thu, Jun 04, 2009 at 09:42:21AM -0700, Dave Engvall wrote: > > It may be possible to get more bang for your buck by purchasing a > > better ball screw ( ebay or HIWin). > > Thank you for that. I'm not sure that I'd trust ebay on duch products, > unless it's a recognised vendor using that means to advertise a > warranted product.
I've had a hard time finding a good vendor for ball screws. I orI tried Hiwin which did not turn out as well as I'd like. http://www.wallacecompany.com/machine_shop/bridgeport/ (See bottom of page) Microkinetics seems to have a good product, meaning they have decent screws with double nuts and provision for lubrication. http://www.microkinetics.com/conv_kits/index.htm I've heard Grainer might be a good source, but I haven't studied their products yet. http://www.grainger.com/Grainger/wwg/productIndex.shtml?L2=Ball&operator=prodIndexRefinementSearch&originalValue=ballscrews&L1=Screws%2C (Short URL) http://preview.alturl.com/gkmv Wherever you shop for screws, make sure you get confirmation that the screws have adjustable preload, and that you are getting the other features you want. Vendors don't seem to want to give specific answers, so you'll need to press them for what you want, or just move on to someone else. Don't assume anything, like I did. This could take time so you may want to get your acme screws going first. Ideally, you should look for an old CNC that already has ball screws. I bought my Shizuoka and converted to EMC2 for less than $2500. http://www.wallacecompany.com/machine_shop/Shizuoka/ ... snip > Ah, it's off with the quill feed pinion, capstan, and fine feed worm > then, unless milling the 3 bolt holes to slots will allow the pinion to > slip into pefect mesh with the rack on the quill. There's then room to > fit a vertical ballscrew, clamped externally to the quill nose. It would > only be 3-4 cm to the right of the quill circumference, but that would > be about 8cm (3") from the quill centre. I haven't tried this, but I don't think you will ever get the backlash down to the .0005" area that I think is needed. Others have used the quill rack and have been satisfied. Check out CNCzone.com for examples. I prefer putting a ball screw on the knee. Or even better, remove the head altogether and fit a new slide and CAT 30 or 40 spindle instead. If needed you could refit your old head and be back where you started. > Yes, stopping to think it through, with the encoder on the motor or > leadscrew, backlash after that isn't a feedback issue. But it may be a positional and surface finish issue. The table will have uncontrollable movement within the backlash. With manual machines, the better machinists will lock the axes during a cut, and always come up to a location from the same direction. You can try this with your CNC but it's not common practice. ... snip > Yes, it is just that kind of analysis paralysis which results from > having a purely manual machine, and thus no quantitative starting point > for the conversion. I have some 100W and 300W motors, which will at > least provide points from which to extrapolate. Good luck, be patient, have fun. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ OpenSolaris 2009.06 is a cutting edge operating system for enterprises looking to deploy the next generation of Solaris that includes the latest innovations from Sun and the OpenSource community. Download a copy and enjoy capabilities such as Networking, Storage and Virtualization. Go to: http://p.sf.net/sfu/opensolaris-get _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
