On Thursday 18 April 2019 11:50:00 Ken Strauss wrote: > Google is your friend! > ft-lb =Nm * 0.73756 > So 75Nm = 55.3 ft lbs > 55 ft/lbs? Here the tool will walk out and break, very quickly at that tension. Doubtfull I have used less than 75 ft-pounds on the TTS adapters I use fairly universally on the G0704.
> > -----Original Message----- > > From: Gene Heskett [mailto:[email protected]] > > Sent: Thursday, April 18, 2019 11:45 AM > > To: [email protected] > > Subject: Re: [Emc-users] Something to think about re the hack-a-day > > tool changer > > > > On Thursday 18 April 2019 07:47:51 andy pugh wrote: > > > On Thu, 18 Apr 2019 at 10:22, Roland Jollivet > > > > <[email protected]> wrote: > > > > To recap; small steppers 'drive' the carousel around to tighten > > > > the motor. > > > > > > No, the motor drives round the carousel to tighten the collet. > > > > > > It is really rather clever. Assuming that it can't work based > > > purely on guess-work seems silly. > > > > No, not silly, experience Andy, experience reaching into the bank > > account to replace tooling that broke by walking out of the holder > > when I thought it was tight enough. > > > > > I suggested a very simple test using the same torque wrench as > > > Gene presumably uses now to tighten his collets to the correct > > > torque to test the hypothesis. > > > > All 4 of my 5 torque wrenches are in foot/pounds. The smallest is in > > inch pounds. How much is 75Nm, in inch pounds. > > > > > But, assuming a 5mm pitch screw and 5:1 motor reduction: > > > (0.5 Nm stepper * (2 * pi) / 5mm ) * 5:1 = 3kN. On the end of a > > > 75mm arm that is 235Nm. > > > Correct torque for an ER20 is 75Nm. > > > > That is no where near tight enough to keep it from walking out of > > the collet and breaking the tool because its digging 3/8" on a cut > > that should be 20 thou if it hadn't walked out. Here I use an end > > wrench about 15" long, ground thin enough to fit the flats on the > > TTS holder, and a 10 or 12" crescent wrench and a pull on the > > wrenches that is likely in excess of 100 lb-ft. I don't have a > > newtom-meters to pound-foot conversion handy but that certainly is > > tighter than 75Nm. > > > > Ditto if using an R8 directly, the R8 gets tightened with a 20 volt > > electric impact wrench driving an 8 point 10mm socket a lot tighter > > than I can draw it by hand with the supplied toy 10mm endwrench. If > > not, the TTS in the R8 may slip and walk out. The life of that > > socket before it splits might be 50 times, its hell on good quality > > sockets. > > > > > (Though I am not convinced that an ER17 can really lift a 300kg > > > mass, so suspect I messed something up. ) > > > > 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 > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
