On Tuesday 25 November 2014 09:49:28 Leonardo Marsaglia did opine And Gene did reply: > 2014-11-25 0:40 GMT-03:00 Gene Heskett <[email protected]>: > > 360, a pulse every degree? if you can only track it to 20 kilohertz, > > your circuit is in trouble by about 58 rpm. I am using a 50 > > cycle/turn encoder, and the 5i25 is still loafing at 1500 revs. But > > I would think it would have to work a little harder watching a 360 > > cycle ABX. As far as usefulness for threading, the 50 cycle seems > > at least adequate. I have used every thread I have cut with it > > except the one I saw being started well at about 150 rpm, then > > shoved the slider over to about 700. Instant mess. > > Hello Gene. I didn't express correctly about that. The 20 Khz is the > pulse generation cabability of these encoders.
I wondered about that, after I had clicked Send. :) > I'm going to use > hardware encoder counters so I'm far above 20 Khz for reading the > pulses. For the job that I'm planning to do with the lathe wich is > rough cutting of camshafts I'm not going to exceed 40 RPM on the > spindle because the maximum speed of the X axis is 10000 mm/min. That is about 2x what mine can do. I think, not actually measured because it only has a hair over 2.5" of travel. > It > would be ideal to use a round mill and cutter compensation for this > job to increase cutting speed and I'm sure LinuxCNC can handle this > more than well, but for this first test I'm comfortable with the low > speed since this is a big improvement in machining the lobes. Also, > for that case we have two old slant copying lathes that are great > candidates for such a modification, in fact they are waiting for a > LinuxCNC retrofitting. > I am sure we've both seen some pretty "square" camshafts but everytime I think about the roller tappet stuff, I recall the cam and tappets in the Nash Ambassador big 6 engine used from '49 to the end of Nash. That engine was a stroker, at 4 & 3/8", but it had, from a hot rod viewpoint, every trick in the book, much of which was unlocked if you put the timing gears back in so the cam was a tooth late. Between that and some work on the distributor, there was another 100 horses in there you could take to the starting gate. One of its secrets was the cam follower tappets, huge mushroom faces that just cleared the next one over, fully 2" or a hair more in diameter, with a spherical face radii of about 4 feet. That gave them room for a cam diameter out of sight for most engines, and while the timing was only about 255 degrees, the lift, and squareness of the lift was at least as good as you could get with roller tappets. Combined with tulip'd valves and double springs, and despite the single barreled carb and that covered ditch in the head casting capable of being uncovered and suitably polished, could breath better than anything else on the road at the time, and got phenomenal gas mileage, 20+ at 100 mph doing it. Biggest problem was the puny brakes, nowhere big enough to do a panic stop but once, then you had to replace all the drums, they got that hot & warped out of round, about a quarter inch. 9" drums, 1.5 wide in front, 1.25" wide in back IIRC. A joke. But that joke could hang the speedo needle straight down if you wanted it to. > ANyway for normal turning I'm close to 1200 RPM sometimes, but that's > not going to be a problem for these encoders, nor the hardware for > reading them. The way that 1hp is geared, 1200 is marching right along for my toy. 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> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS ------------------------------------------------------------------------------ Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server from Actuate! Instantly Supercharge Your Business Reports and Dashboards with Interactivity, Sharing, Native Excel Exports, App Integration & more Get technology previously reserved for billion-dollar corporations, FREE http://pubads.g.doubleclick.net/gampad/clk?id=157005751&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
