On Tuesday 24 January 2017 09:49:12 Ed wrote: > On 01/23/2017 11:45 PM, Gene Heskett wrote: > > Greetings all; > > > > I see some "Nema 24" motors at quite reasonable prices showing up on > > fleabay, > > SNIP > > > Now, I don't believe this is going to help with the resonance stalls > > I am getting at about 30 ipm, so I'm thinking of building a viscous > > damper to fit on the rear of this puppy. But unlike the ones on my > > hf micromill, which are long steel spools carrying a 2+ inch stack > > of heavy fender washers with elastomer sheets between the washers, > > which are true shock absorbers as the resonance is killed by the > > frictional losses as the washers walk on the talcum covered > > elastomer, but I don't have room for a 2+" stack of fender washers > > in this spot. 5/8" axially at best. > > SNIP > > > Cheers, Gene Heskett > > RANT MODE ON > > Why in this day of cheap encoders, small ebay servo motors, and good > inexpensive servo drives does any one even use stepper motors? > > Dampers, resonance issues, lost steps, stalls, only 30 IPM? Why? > > Gene, don't stay on the dark side! Go to servo's and don't look back, > you will never regret it. > > RANT MODE OFF > > ----deflates----- > > Ed. Because the stepper motor at up to 470 oz/in can be had for under a $40 bill, and a suitable driver for the mid $30's (nema 23), or mid $60's for a nema 34 if you don't need 3k revs and a suitable psu for less than $40 for either, less than $150 an axis worst case.
The only servo drive I am familiar with is $120, and motors with encoders are around $250 and up to $2500 on ebay right now (and obviously too long as I only have about 118 mm for the x motors depth) , and the interfaces giving the analog voltages the servo driver's need are about $20 an axis more? Although the vfd I find is happier that that famous hog being fed by a pdm signal at a 10 khz pulse rate) So here's a challenge Ed, find me a 2 axis kit that can move this 11x36 with as much torque at working speeds as these steppers can make, for a $300 bill, thats w/o the interface card as the pi doesn't have a parport, so I'm stuck either reverting to 1 or more 5i25's in an old Dell, or making the pi work. But this spi bus's noise sensitivity is killing me. There seems to be NO EXPOSED PLACE on eithers pcb where I could tie them together with a 2" piece of 5/16" wide braid using 3% silver eutectic solder, so they truly had a common ground. I may yet sacrifice a usb port on the pi (the guts look like plastic that would melt and be destroyed), and make up a 10 pair header with the top trimmed back enough to expose the tops of 10 female crimp terminals, so I can make a ground, a REAL ground, between the pi and the 7i90. If price really was no object, sure, but this is the real world, and I'm on SS since mid 2002. This is a hobby project to keep me out of the bars. I rest my case. There is point triple ought zero chance of this thing ever paying for itself in my remaining time. I am 82, a type 2 diabetic, and 2 collapsed disks in my back they refuse to consider doing any more for than write painkiller scripts for. And the only one that helps is about to become a scheduled narcotic in WV. It seems the overdose cadavers are testing positive for it. > > ---------------------------------------------------------------------- >-------- 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 > [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> ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
