On Jul 21, 2012, at 9:50 AM, Jon Elson wrote: > Jeshua Lacock wrote: >> >> It looks like over a 10 foot span I have about 24mm (0.96 inches) of sag in >> the middle. >> > 10 foot span? 25 mm diameter? Oh, my, that sounds WAY past the safe range. > See http://www.nookindustries.com/ball/BallCalculators.cfm#CriticalSpeed > for a critical speed calculator. With the stiffest fixing of the ends, > you might > be able to get 500 RPM safely. That would be 100 IPM with a 5 TPI screw. > With a coarser leadscrew pitch, you don't ned as high an RPM, so maybe > this will be OK.
Thanks everyone for all the very useful information!!! Most of the information I had no idea about! And thanks for the calculator Jon. Using End Fixity B (one end double bearing the other single bearing) for 117 inch span I get a safe RPM of 278. At 5cm/rev that is 547 IPM. I think I could happily live with that. More important than top end speed to me is how fast the table can accelerate. And for a 250+ pound table 547 IPM rapids seems pretty decent to me. This axis is also going to be the slowest, so for raster scanning I can move more rapidly on the Y axis. If I had double bearing on both sides (End Fixity C), I would get to 805 IPM and with End Fixity D I would get to 1220 IPM. Unfortunately, I think that would require taking the ballscrews to a machine shop. I guess if I ever want faster top end speed that is an option. Thanks again, Jeshua Lacock Founder/Engineer 3DTOPO Incorporated <http://3DTOPO.com> Phone: 208.462.4171 ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
