On Friday 04 September 2009, Youda He wrote: >Thanks, that look good. > >Does the EMC2 tracking the actual position, assume sometimes the stepper >lost a step or so, with parallel port communication, how does one feed the >optical encode position info back to the computer? > >-- Youda
Through the input pins on that same port, or if there are not enough pins available, a 2nd parport card can be added to the computer. I believe there are enough spare pins that a quadrature pair can be had for 3 axis's without the extra port being needed. However there is a potential problem with that approach. If the stepper is pushed too hard or fast, it will indeed lose steps, and that error will be fed back into emc, which will attempt to play catchup, further weakening the motors torque since steppers torque falls with increasing speeds. So the incipient stall is converted into a full blown stall by the feedback. Either way the motor will generally stall until the step rate is reduced to near zero at the far end of the move, and the part is of course wasted. In my own experiments, I have found that if the machine is well lubed and adjusted, the snappieness of movement can be sacrificed, and because the accels are reduced, then the maxvels go up quite a bit. Faster in steel than my limited spindle can cut without breaking bits because the max spindle rpm is only 2400. I end up programming steel cuts at maybe 10 thou deep and 2 to 3 thou thick chips. Any more and the spindle will stall, blow a fuse or trip its safety off, and a $14 1/4" carbide bit is made into 2 or more pieces. Hard grades of alu can be cut at faster feed speeds but requires the surface be well flooded to preserve the finish and exclude as much oxygen from the cut as is possible. That of course we all know. With steppers, it is far more preferable to stay in the bottom half of the speed envelope where the potential for a lost step and or stalls disappears. If you need more speed with steppers, throw more psu voltage at the drivers, but currents are generally more than sufficient at 2 to 2.5 amps. Or if there is torque available, change the gearing to get more speed. > >On Fri, Sep 4, 2009 at 6:35 PM, Gene Heskett <gene.hesk...@gmail.com> wrote: >> On Friday 04 September 2009, Youda He wrote: >> >Thanks, it seems most computer works, especially the Intel Atom worked >> > well. Do we have drawings to connect parallel port to step driver? We >> > have some Allegro chip that takes pulse, direction and will do the rest >> >> of >> >> > driving. >> >> That is available as a ready made unit, 3 or 4 channels(motors) wide, >> from xylotex, google for it. >> >> I have both a 3 axis and a 4, and within its limits (2.5 amps/motor) and >> 30 volts max for the psu, it works quite well. It will need active >> cooling, so >> I made a box a few inches longer than the board, and the same square as a >> common psu fan, one in each end of the box, one blowing in and of course >> the >> other end is sucking the warm air out. That also works well. >> >> >-- Youda >> > >> >On Fri, Sep 4, 2009 at 12:21 PM, Peter C. Wallace <p...@mesanet.com> >> >> wrote: >> >> On Fri, 4 Sep 2009, Youda He wrote: >> >> > Date: Fri, 4 Sep 2009 11:42:21 -0700 >> >> > From: Youda He <yo...@geometrysystems.com> >> >> > Reply-To: "Enhanced Machine Controller (EMC)" >> >> > <emc-users@lists.sourceforge.net> >> >> > To: "Enhanced Machine Controller (EMC)" >> >> > <emc-users@lists.sourceforge.net >> >> > >> >> > Subject: Re: [Emc-users] What hardware should buy to start >> >> > >> >> > Thanks, do we need to consider what CPU performance level is needed, >> >> > P4, Core2, GHz? memory size? >> >> > >> >> > -- Youda >> >> >> >> Probably 1 GHz or greater, 256M or more of RAM. If you are using >> >> software >> >> >> step >> >> generation, for example with a parallel port driving the step motors, >> >> the >> >> >> main >> >> issue will not be the processor speed, but be the latency of the PC. >> >> This >> >> >> may >> >> require some fussing about with video cards, disabling SMI, or >> >> choosing >> >> a >> >> >> different motherboard. The wiki lists some known good motherboards: >> >> >> >> http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Latency-Test >> >> >> >> Peter Wallace >> >> ------------------------------------------------------------------------- >> >> >>----- Let Crystal Reports handle the reporting - Free Crystal Reports >> >> 2008 >> >> >> 30-Day trial. Simplify your report design, integration and deployment >> >> - and focus on >> >> what you do best, core application coding. Discover what's new with >> >> Crystal Reports now. http://p.sf.net/sfu/bobj-july >> >> _______________________________________________ >> >> Emc-users mailing list >> >> Emc-users@lists.sourceforge.net >> >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > >> >------------------------------------------------------------------------ >> >--- --- Let Crystal Reports handle the reporting - Free Crystal Reports >> > 2008 30-Day trial. Simplify your report design, integration and >> > deployment - and focus on what you do best, core application coding. >> > Discover what's new with Crystal Reports now. >> > http://p.sf.net/sfu/bobj-july >> >_______________________________________________ >> >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> >> >> Justice, n.: >> A decision in your favor. >> >> >> ------------------------------------------------------------------------- >>----- Let Crystal Reports handle the reporting - Free Crystal Reports 2008 >> 30-Day trial. Simplify your report design, integration and deployment - >> and focus on >> what you do best, core application coding. Discover what's new with >> Crystal Reports now. http://p.sf.net/sfu/bobj-july >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users > >--------------------------------------------------------------------------- >--- Let Crystal Reports handle the reporting - Free Crystal Reports 2008 > 30-Day trial. Simplify your report design, integration and deployment - > and focus on what you do best, core application coding. Discover what's > new with Crystal Reports now. http://p.sf.net/sfu/bobj-july >_______________________________________________ >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> Death is God's way of telling you not to be such a wise guy. ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
