On Thursday 20 February 2014 09:14:28 Schooner did opine: > IMHO if you motorise the knee instead of the quill, you lose all the > benefits of the knee elevation for adjusting to workpieces and manually > touching off the Z tool, in favour of a very slow and potentially > troublesome Z axis which requires all movements to be inverted in a > somewhat counter-intuitive way.
I'll submit that if you are so limited, its poorly done. Most knees have a range that is entirely usable, and as far as non-intuitive motions go, a sign change in the scaling fixes that with no fuss because its never changed back. So other than the rather large increase in mass to be moved, it should be no different than moving the head up and down a "square" post, just needing a suitable motor and some of those nitrogen struts to help support the weight, which on a 10x57 mill would be several hundred pounds. A 1" ball screw should be able to do that if enough lift from struts s available. I have looked at a couple of the bigger "bridgeport" style mills with an eye to doing that, 50+ yo, worn to where I could have had one for a kilobuck, but haven't found my round tuit, and likely won't, my back is going to get fixed, if it can be, before I do much with any bigger machinery. > I agree that whilst possible, motorising the rack and pinion would > result in so much slop that it would be next to unusable Agreed. > What is commonly done with manual mill conversions of the turret knee > mills is to motorise the quill and leave the knee as manual. > The quill is disconnected from the rack and pinion arrangement and large > plate clamp is attached to the bottom of the quill > > This is driven up and down through a ballscrew from a box mounted on the > side of the head. > The travel is typically quite short (70 - 150 mm), because all major > adjustments are done on the knee and quill travel is just used to cut to > depth with the standoff between cuts that is required. > (same as it was when a manual mill) That limitation would exasperate me. Sure, what I have is a toy, but in terms of operating envelope nothing made today can match what you get from the larger square post machines. Even my toy has a vertical motion of 14", and can reach it at 30 ipm. Its so flimsy all thats good for is tool changing clearance, or wood carving (I've carved a BP gunstock on it, gets ohh's and ahh's at the range) but I can mount a vice that raises the work 3+ inches without a problem that ball screws in the xy wouldn't fix 90% of. Thats a WIP. <http://www.grizzly.com/products/Heavy-Duty-Benchtop-Mill-Drill-with- Variable-Speed-and-Power-Feed/G0762> Gives you a machine with an operating envelope of 18h x 7.5y x 22x, or 1.71875 cubic feet. For 2774 USD sitting on your 1/2 ton rated table, or another $275 on their stand. Add 3 ball screws & suitable motors & mount hdwe and LCNC. Might be $4500-5000. And that is a much larger cubic volume than you can get in any "Bridgeport" style machine when limited to driving the quill. > I have such a mill and it works very well. > > regards > > ------------------------------------------------------------------------ > ------ Managing the Performance of Cloud-Based Applications > Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. > Read the Whitepaper. > http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.cl > ktrk _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users 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) Genes Web page <http://geneslinuxbox.net:6309/gene> NOTICE: Will pay 100 USD for an HP-4815A defective but complete probe assembly. ------------------------------------------------------------------------------ Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
