On Sunday 28 April 2019 05:52:45 andy pugh wrote: > On Sun, 28 Apr 2019 at 03:08, Gregg Eshelman via Emc-users > > <emc-users@lists.sourceforge.net> wrote: > > I just don't see the point in making the electronics and electrical > > system more complex when there's no need for it. > > I think that the reason is that it can be simpler to route wires to > two sides of a moving gantry / moving motor setup than to engineer a > cross-shaft. > > If the motor is stationary then cross-shafts make sense. But for the > common moving-motor designs (and Racks / Servobelt are inherently > moving-motor) the drive needs to be stepped-up through the gantry or > down under the table and that can be awkward and increases moving mass > and potentially introduces backlash.
My 6040's Y motor is smack on the middle of the bed frames end bulkhead, with a smallish ball screw driving a large plate of 1/2" alu that rides two 3/4" or so rods under the bed, with the ends of this plate sticking out from under the bed, and the gantry risers are bolted to the ends of this plate. Any racking would be in how this it assembled by the user, those bolt holes are very precisely sized requiring they be wiggled a bit to get the alignment for easy bolt insertion,and the motor is unaware of it. There can of course be something sticking out to catch the gantry as it goes by, or dull tooling with x way off center x could flex it, but it does seem sturdy enough for light alu work or pretty heavy wood carving. The only complaint I've seen on the forums is the x rods need to be heavier to better restrict the forward/backward tilt the cutting forces cause on the spindle, they are only 1/2 rods so I'd agree. I don't have a clue how well it would carve the green and green finger joints that I have done on the G0704, in 3 depth passes with a 1/4" end mill to get into a spoil board and jig. I think its wide enough to do the 1x12"'s that blanket chest uses for side and end boards, but at 600x390mm its not big enough to do the machineing of the lids which are 2 ea 1x12's wide with breadboard ends. I doubt its as rigid as the dual glued down belt and caterpiller tread drive would be, but it seems to be plenty good enough for wood working and its not subject to swarf or sawdust as all the drive is under the bed. If your tools are sharp, both cherry and mahogany can be carved very precisely. And I could see a dual drive even with the single motor in the center of the cross shaft as being at least 3x more costly because of the need for a precise bed for the glued down belting on both sides. This thing is a toy and I know it, these guides have oilite bushings, something else that lowers the cost and height. But its doubtfull I'll last long enough to wear it out, my present plans if they work out, will take me out of the garage, tuning AM radio towers with a new test tool I've purchased, so I'll be playing last of a breed and dying radio engineer till whenever. Now I better go take the missus her freshly made morning coffee and see what she wants for breakfast. 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> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
