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.
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