On Sunday 10 January 2016 06:56:35 Erik Christiansen wrote: > On 10.01.16 09:45, Marcus Bowman wrote: > > On 10 Jan 2016, at 00:22, andy pugh wrote: > > > On 5 January 2016 at 11:34, Dave Caroline <[email protected]> wrote: > > >> Here is an example of with and without limits in a trunnion > > >> design > > >> http://www.ebay.co.uk/itm/CNC-Rotary-Table-Dividing-Head-Rotation > > >>al-Axis-4th-5th-Axis-A-B-Axis-100MM-Chuck-/161679996211 > > > > That's an interesting configuration. There are a lot of small > > attractive looking Chinese 4th axes at reasonable prices, but I do > > have reservations. If I coudl be convinced they were accurate, I > > would happily order one; but other Chinese accessories are not of > > the standard to which I aspire, so I'm hesitant. > > ISTM that the table can only tilt +/- 45° or so. Since the need for a > symmetrical swing is obviated by rotation of the chuck, I'd rather > have one which could swing 90° one way, from horizontal to vertical. > > The coarser axis has a resolution of 0.3°, assuming 1.8° steppers, and > holding accuracy will be a function of cutting forces, I figure. If > anything finer than full steps are attempted, holding torque quickly > goes downhill. A clamping brake on the table would be a handy > addition. (A cone brake might might minimise misalignment as the brake > is applied?) > > Erik
Depending on what you want to do. I see those as engraving only helpers as neither of the 3 choices on that page have motors big enough to have any REAL holding torque to resist even 0.125" carbide mills cutting forces. A version like the British 230 priced one, where the limit of rotation for the second axis would be nominally +-360 degrees due to life considerations of its motor cable being externally twisted as it passes thru the hole in the carriage, makes far more sense, but needs scaled up about 4x to make room for additional gear down, and equipped with triple-stack, 500oz/in nema 23 motors. With that scale up, one could have room for a pair of 8/1 reductions, which if the belts are tight enough, ought to be 0.0375 degree accurate. I'd assume shop made, buying one like the 229 pound sterling one, scaled up big enough to just fit on my G0704's table would need the proverbial little red wagon loaded with $50 rolls of our dollar coins. And making it might be fun! Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
