On Tuesday 17 July 2018 10:00:36 andy pugh wrote: > On 17 July 2018 at 14:25, Gene Heskett <ghesk...@shentel.net> wrote: > > 'twouldn't work on my machine. Incapable of loosening any collet/nut > > combo I own in 1/4 turn. 2 turns maybe, and in any event could only > > tighten a collet to about 5% of the torque it needs to adequately > > hold a tool. > > That depends purely on the diameter of the disc and the axis force. > > It uses the axis move to crack the collet free, then spins the spindle > to loosen further. > And there is no reason that the rotary move couldn't be more than a > quarter turn. > > ER20 wants 80 Nm.
I'm much more familiar with something like lb/ft, how do I translate that into what I am currently tightening the er20 nut to?, which I'd estimate at 50+ lb/ft. So mentally I can't compare that to 80Nm. > If the disc is 100mm radius then it needs an axis force of 800N, or > 80kg. If the ballscrew on the axis is 5mm pitch then that implies a > motor torque of 0.6Nm. So even a relatively small stepper can do it. That disc I'd estimate was no more than 50mm radius, doubling the required motor power. With less than 5.5" of Y motion available due to the Y drive conversion design limiting how far forward it can move, I'd be hard put to come up with a working 70mm radius for a 185 or 190 degree turn. I would be much more interested in converting that spindle to some sort of an atc gripper design, but that would probably be prohibitively expensive since the tool holders are around 50 bucks each. So my thoughts keep comeing back to ways of driving the drawbar bolt with the spindle motor, but even if I bang the motor that hard, how long would the plastic backgears last. The shock load of using the racheting screwdriver on it is probably damaging the gears now, but I don't have any choice until I can economically key all those TTS holders into the spindle. The r8's are keyed of course, but nothing inserted in them is except the tap hats I have made 50+ of so far, so it has to be tightened the proverbial 1/16 turn from broke to get an adequate grip on the TTS's smooth and hardened shank. Side comment on the link showing the use of atc type tool holders on the gantry machine. Listening to the motor run, its going to have a bearing life measured in running hours, probably under 2, as its way out of balance, and its not the holder, its the motor. I have a 24k rpm 1 hp air cooled motor that came with a 1.5 hp vfd for a hair over 235$, and at 24k rpms, all you can hear is the air its moving thru itself for cooling. Its amazingly quiet and free of vibration. I did not expect that level of balance from a Chinese motor. I may see about getting another vfd, and making a toolpost grinder out of it. I mounted a cheap Chicago die grinder, running it on a powerstat at about half voltage to clean up the short mt5 in that lathes bent spindle. I didn't want to blow up a 12k rated stone inside the spindle. It ran that way for probably 50 hours, polishing away about 7 thou before it was trued. Then I found the mt5-5c adapter was junk, and had to buy another from Grizzly $100, then shorten and customize it to run true, and now my er40 adapter runs out about a thou 4" out of the collet. Thats close enough for the girls I go with. :) Then of course I had to reface and redrill the backing plates for the chucks. Lots less spinning vibration now. Next is figuring out how to measure bed wear so I can use the linear and offset modules to insert compensation for that. Trying to design a laser, and a toolpost mounted target that will show me bed errors, but have not mentally come up with something that looks accurate enough to build. Yet. -- 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> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
