On Tuesday 06 October 2009, dave wrote: >On Tue, 2009-10-06 at 09:47 -0400, Gene Heskett wrote: >> On Tuesday 06 October 2009, Ian W. Wright wrote: >> >HI, >> > >> >I'm in the process of building a second little mill - this >> >time a stepper-driven gantry type and I'm wondering what the >> >pros and cons might be of different driver locations. On the >> >first mill I had all the controls in a big box under the >> >bench with heavy wires going to each motor but I'm wondering >> >now whether any advantage might be gained in this project by >> >positioning the driver cards adjacent to each motor. This >> >would shorten the cables carrying power to the motor but >> >would mean carrying signal cables from the parallel port >> >around the machine together with DC power wires to each >> >card. One reason for considering this is that, on my >> >previous machine, I had a problem with the Z-axis stepper >> >picking up interference from brushed spindle motors and so I >> >had to change to a 'universal' AC motor drive for the >> >spindle which was heavy and limited in speed. I tried >> >various methods of screening the Z-axis motor leads and put >> >ferrite beads over them but nothing seemed to work. As I'd >> >like to use a high speed spindle based on a DC motor on this >> >mill, I wondered if it might be easier to shield the >> >'signal-in' wires rather than the power wires to the motor. >> >Any thoughts? >> > >> >Ian >> >> I may sound like a broken record Ian, but the 'star' grounding >> configuration, and running all signal and motor drive circuits through a >> cable similar to Belden "Star-Quad" with all the shielding for even the >> motors output drive tied to the central point of this star, where the >> central point where it all comes together is at the common point. The >> cumputers ground line from the parport, and the minus rail of the motor >> power psu are all connected, possibly to a single long bolt, or in my >> case I ran a handy piece of 12 gauge bare copper that goes from the motor >> - terminal on the xylotex, around to the side of the box I made for the >> xylotex board, so that the shields of the motor cables were tied to it. >> My motor cables are about 6 feet long, and the shields stop short of the >> motor, no connection on that end. The machines ground is also connected >> there via a rather circuitous route going through the spindle motors >> power cable, the one cable that is not shielded, via the PMDX-106 and the >> interconnecting cable back to the breakout strip on the xylotex. >> >> I have not had any noise problems. >> >> Belden's search facilities can be confusing. >> >> Another supplier might be Canare >> <http://www.canare.com/UploadedDocuments/Cat11_p35.pdf> > >I've been known go to Home Depot and buy a Cutler-Hammer neutral bar; >and tie everything to that. Seems to work. > That, and no place else for each branch that leaves it. Same idea as by piece of 12 gauge and a hot soldering iron. Either will work provided the screws are tight enough to present a gas tight joint for extended amounts of time. You cannot do that with alu conductors of course as they cold flow at 20x the rate of copper. This relaxes the joint pressure, air gets in, and alu does what it normally does when exposed to the oxygen in the air, form an insulating film with 100% coverage, and a 30-50 volt breakdown in about one millisecond. Alu is great, in its place, but inside an electrical box of any kind its just a damned fire starter with a long fuse timing.
>Dave > > >--------------------------------------------------------------------------- >--- Come build with us! The BlackBerry® Developer Conference in SF, CA > is the only developer event you need to attend this year. Jumpstart your > developing skills, take BlackBerry mobile applications to market and stay > ahead of the curve. Join us from November 9-12, 2009. Register > now! http://p.sf.net/sfu/devconf >_______________________________________________ >Emc-users mailing list >Emc-users@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/emc-users > -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) The NRA is offering FREE Associate memberships to anyone who wants them. <https://www.nrahq.org/nrabonus/accept-membership.asp> The opulence of the front office door varies inversely with the fundamental solvency of the firm. ------------------------------------------------------------------------------ Come build with us! The BlackBerry® Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9-12, 2009. Register now! http://p.sf.net/sfu/devconf _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
