On Saturday 13 June 2015 19:31:20 Greg Bentzinger wrote: > Replies inline > > > Quoting - Message: 7Date: Sat, 13 Jun 2015 14:42:37 -0400 > From: Gene Heskett <[email protected]> > Subject: Re: [Emc-users] was Suitable transformers = hens teeth > To: [email protected] > Message-ID: <[email protected]> > Content-Type: Text/Plain; charset="iso-8859-1" > > On Saturday 13 June 2015 12:05:11 Greg Bentzinger wrote: > > Gene; > > > > We really need to break your DC motor fixation. If you think PCW's > > 5i25 is neat just wait until you start using a VFD controlled > > spindle. > > > > Odds are that a better replacement motor and VFD will cost near the > > same of what your planning to build to support that marginal OEM DC > > motor. > > That marginal motor is easily replaceable with something with serious > grunt that is right at home at 5 grand at the armature, perhaps 1100 > at the spindle. > > The power supply in each case is the majority of the cost, but with > Jon's PWM servo driver, slightly modified, I've found I CAN manhandle > a treadmill motor fast enough to do rigid tapping, with grunt enough > to drive the tap. None of those vfd things, designed to turn at 24k > rpms for engraving, can even begin to drive a 4-40 tap, let alone a > 1/2-13. And for those situations where I don't have the grunt to do it > in one pass, I have already written pack tapping stuff to wrap up the > G33.1 with. > > > I have several great treadmill motors and some motor controllers for > > them, > > motor controllers intended for a treadmill motor are incapable of > doing the control needed. Jon's pwm servo amp, with increased wire > gauge in the toroids, can turn that treadmill motor around from 3 g's > at the artmature, 300 at the spindle, in a time frame quiter > comparable to the vfd if allowances for the flying weight to be > reversed are taken into consideration. On my lathe, that flying > weight is well above 10lbs as its swinging a 5" 4 jaw chuck. > But that is not using the treadmill controller, which cannot actively > stop the motor. Jons PWM Servo amp can. > > > but trying to keep fine tune of RPM vrs load is a hemroid and > > using those controls for reversing just isn't practical. Then there > > was the heating issue of running the motor at lower RPMs. > > I no longer try to subdue those BBLB controllers, they decorate a > shelf now. Jons PWM Servo amp is a breath of fresh air in comparison. > > > I would get a 1.5 or 2hp motor with a lower 60Hz rpm spec then over > > speed it as needed so you have plenty of low rpm power. > > And just how do I spin a 2.2kw water cooled, 24k revs motor at 250 > rpm's > > and have enough torque to throw a .015"x.015"x3/8" chip 2 feet away? > > -- ^ ^ ^ ^ ^ ^ No idea where you came up with this - never said > anything about water cooling or trying to use a 24K router type > spindle.
Because an ebay search for 2kw vfd spindles only returned such engraving motors with the exception of a $3700 head for a bridgeport. > I actually said a LOWER rpm rated motor (@60Hz)- such as a 1725 or > below. > > I dropped "56C 1.5hp 3ph" into ebay search and the first thing that > popped up was ebay item#4601799582 > > Buy it now price of $139 - I'm sure a better deal can be found, but > this was the first item that popped up It does look good, but where can I get an adaptor to mount that 56C frame on the GO704? Or is that my first project, making one? ;-) How about this for a driver? <http://www.ebay.com/itm/New-1-5KW-VARIABLE-FREQUENCY-DRIVE-INVERTER-VFD-NEW-2HP-220V-/121551267361?pt=LH_DefaultDomain_0&hash=item1c4d052621> At $116 + ship, looks good also. Needs a modbus circuit from lcnc. Who has that hardware? > New 56C/TEFC 1725rpm 1.5hp 5/8" output shaft inverter rated, 10:1 > Variable torque, 2:1 Constant torque > > Direct drive 1:1 this motor would provide: > > 172.5 rpm @ 6Hz > 1725 rpm @ 60Hz - Nominal motor spec - Optimal > > 3450 rpm @ 120Hz > 5170 rpm @ 180Hz > 5750 rpm @ 200Hz > > I would not trust the Grizzly spindle bearings @ 6000 rpm unless I had > removed, checked fit, regreased and set the bearing preload. > And TBT, these are horrible, 15 minutes no load at 1600 revs raised the quill temp 25F on my IR thermometer. I am repeating the breakin procedure, but I doubt if it will do much good, I believe them to be seriously preloaded way too high. IMO, decent bearings are a must, but you do not get those in a $850 machine. So no complaints to Grizzly unless I can't find decent bearings a year down the log. > Now if you got ambitious and wanted to do a step-pulley drive: > > Underdrive the spindle 1:0.5 > > 86.25 rpm @ 6Hz > 862.5 rpm @ 60Hz - Nominal > 1725 rpm @ 120Hz > 2587 rpm @ 180Hz > 2875 rpm @ 200Hz > > Overdrive the spindle 2:1 > > 345 rpm @ 6Hz > 3450 rpm @ 60Hz - Nominal > 6900 rpm @ 120Hz > > > On a side note you would still have the Pico drive available for > > your old mill so little things like engraving could still be done on > > it. > > Its actually on my lathe. Thats a PMDX-106 on the mill, driving a 1.8 > amp rated, 2500 revs at the spindle on the mill. The OEM pass hexfet > died years ago, and was replaced by one from a dead computer psu. > Nearly zero heating now, it could do a 400 watt motor just fine if I > ever get around to using the motor I took out of the lathe. > > > That 240V is just waiting to be used... > > I found a toroid to fix that last night. Admittedly, the PMDC motor > has brushes to wear out, where the vfd doesn't. But where do I find > the power to spin a 1/4" upcut solid carbide tool with that vfd driven > pipsqueak? Can that vfd and a water cooled motor do 47hz output and > > turn a 1/4-32 tap 180 revs in steel? > > I'm sure you would have no problems tapping @ about 300 rpm. > > Why piddle around with a 1/4" endmill when a 3/8" is a better buy - > save the 1/4" for finishing the corners. Because until I get this 704 running, I don't have the power to spin the 3/8 or 1/2. > > I had no idea what could really be done with the tooling I all ready > had until I went to the WESTEC tool show and watched other machines > plow through metal like butter. I was still thinking small. I need to do that myself. Sandevic has some nice videos, just bring little red wagonloads of money though. > Good question that. > > > > Cheers, Gene Heskett > > End quote & reply - Greg > > > > BTW the motor picked would put you close to the same as what Anders > Wallin used for his build. > > > http://www.youtube.com/watch?v=uhaKQH2CCGI > > ---------------------------------------------------------------------- >-------- _______________________________________________ > 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
