The Backlash is very small on the R/P [I can't measure it] but it does wear out over time [I'm on my second set of rack and third set of pinions] I've decided that it would be a better system if I moved to the ballscrew or a super hard helical R/P. The ballscrew came out cheaper so.. that's where I'm headed.. The R/P starts to get rough after it's worn in for a while and finally at some point you just have to replace it.. It's not SUPER high quality stuff either so the overall accuracy suffers a bit [It's very repeatable, just not super accurate over linear length]
Not sure I follow you on the bidirectional lead screw comp? J. Johnson > J. Johnson > If the rack drive has no backlash and is strong enough to > handle the > cutting forces there is no reason to go to a ball screw. > The bidirectional lead screw compensation works very well. > Stuart > > On Fri, Sep 4, 2009 at 12:46 PM, H & J Johnson > <hjjohn...@sasktel.net>wrote: > > Thanks Steve, this was infact my plan. I've got a bunch of > G202's and > > steppers sitting around. It would > > be fairly simple to load it up and start playing and get my feet > wet that > > way.. we'll see how things progress > > from there. I'm several months away from any major changes on my > > machine..just want to start > > mapping out the process and seeing if I can make it work. :) > > > > Thanks again! > > > > J. Johnson > > > > > H & J Johnson wrote: > > > > > > >Steven, thanks for taking the time to reply. I'm by no means a > > > programer>nor do I expect that I'd get proficient at it in the > > > time frame needed [or to > > > >the level that would be required]. I'm more interested in being > > > able to > > > >'look up' stuff and learn to read code a little.. to > understand what > > > >is be asked where etc. > > > > > > > > > > > Actually, I think I might have been wrong about where to start. > > > Get > > > yourself an old throwaway PC, and install Linux using the EMC2 > > > liveCD > > > from linuxcnc.org. You will find that it's very similar to what > > > you're > > > used to, just some of the details are different. (The "program > > > menu" is > > > at the top left of the screen, and is labeled "Applications" > > > instead of > > > being at the bottom left and labelled "start" ...) > > > > > > Play around, and don't expect to save anything from this install. > > > You > > > can always intsall again if you do something that you can't fix. > > > (Note: you can do a lot of experimentation just by booting from > > > the CD > > > - it's a fully functional system - but you may be nervous about > > > destroying data, that's why I suggest doing an install on a PC > > > that has > > > no useful data on it) > > > > > > >On the motion controler I should have called it a step generator. > > > I've>used the G100 and have [haven't installed it yet] a Smooth > > > Stepper>for Mach3. > > > > > > > OK, I wasn't sure. There are several similar units for EMC2, but > > > none > > > use ethernet or USB for communications - they're either PCI or > > > parallel > > > port connected. > > > > > > >I've been satisfied w/ how Mach3 has run the only > > > >thing that is driving my switch to EMC is the ability to do > > > proper tool > > > >offsets while in 5 axis. Brian [from Artsoft] has advised me > that he > > > >doesn't currently have plans to add this functionality. He's a > > > busy guy > > > >and my move is in no way a slight against him. > > > > > > > > > > > None taken :) > > > > > > >I'm sure that a switch to EMC is more daunting in the initial > > > stages > > > >than it is once one jumps in. However I'm at a bit of a loss > > > since I've > > > >no experiance w/ Linux or EMC. > > > > > > > > > > > It's more in your head than anywhere else :) > > > > > > The differences between Linux and Windows today are a bit like the > > > differences between cars. Some have the headlight switch on the > > > dash, > > > others on a stick on the steering column. Some need you to press > > > a > > > button to switch high/low beam, others need to be pulled to > > > toggle, > > > others are push-pull ... They all do more or less the same thing, > > > but > > > the controls are slightly different. You probably don't have much > > > trepidation about jumping into an unfamiliar rental car - try > > > adopting > > > the same attitude toward a new operating system. (note: I'm not > > > saying > > > that there are no differences, or that it will never be > > > frustrating to > > > figure out how to do something on Linux that you already know how > > > to do > > > on Windows, it's just that most of the differences in day to day > > > use are > > > small details) > > > > > > >I've down loaded the manuals and will start reading them this > > > weekend.> > > > >Has there been configurations created for a 5 axis system > where a > > > person>can just add the head dimensions to allow the software to > > > compute the tool > > > >offsets? > > > > > > > Yes, maybe. > > > > > > It depends on the construction of the head. There are two > > > versions that > > > I know of, one of which is included with EMC2 (5axiskins). Stuart > > > Stevenson has also made a kinematics file for one of his > > > Cincinatti > > > 5-axis machines, which takes many things into account, including > > > certain > > > build errors. I don't know if that's finished yet. > > > > > > > I'm hoping I can put a auto tool length system in as well so the > > > >machine automatically measures the tool length on each ATC. > > > > > > > > > > > Fully automatic measurement needs some G-code support at the > > > moment (you > > > can call a subroutine to measure and apply the length) > > > > > > >Just had a look at the Motec stuff, I see the 100 series has 8 > > > axis which > > > >would suffice [I need min of 6, prefer 7] for my setup. I'm not > > > seeing > > > >anywhere, where it states that it will output step/dir, as I > re- > > > read your > > > >reply I believe that is infact the case. > > > > > > > > > > > No, the Motenc hardware outptus analog control voltages. > > > > > > >Are the Mesa cards 'stackable' in that I can add as many as I > > > need [IIRC > > > >they have 4 axis cards so I'd need two?] Does Mesa provide > some form > > > >of a configuration file w/ their cards to help a user get to > > > [almost] plug > > > >and play, or does one have to manually configure the card etc? > > > > > > > > > > > You can mix and match anything you want. You can use parallel- > > > port > > > software PWM to control spindle speed, while using a Mesa card for > > > some > > > motors and a Pico Systems card (connected via a separate parallel > > > port) > > > for some other motors. They can be any mix of velocity control, > > > torque > > > control, PWM, and step/dir motors. > > > > > > A single Mesa 5i22 card can handle as many as 16 servos, though > > > I'm not > > > sure there's an FPGA configuration for that. The cards are > > > reprogrammable, and you can select different "firmware" for the > > > cards as > > > you see fit, even using different firmware for each card when you > > > have > > > more than one. The Mesa cards have from 2 to 4 "IO Connectors". > > > Each > > > connector can support up to 4 motors, or 24 I/O lines, and in some > > > cases > > > you can use motor controls and I/O on the same connector. > > > > > > >Also on alot of this hardware I'm seeing the closed loop of the > > > encoders > > > >coming back in. How does this play w/ a closed loop drive where > > > it requires > > > >the encoder connection back to it's self, to be able to accuratly > > > drive the > > > >motors? [ie; my Granite drives] > > > > > > > > > > > You can run the encoder back to EMC as well as to the drive. It > > > shouldn't be too much of a load on the encoder line drivers. For > > > the > > > Fanuc Yellow Caps, you may want to look into an analog velocity > > > mode > > > servo amp. I don't know how well the Granite drives are matched > > > to > > > those relatively large motors. I wouldn't choose step/dir > > > controlled > > > drives unless I had to (for example, because that's all my > > > software > > > supports ... :) ), I'd much prefer to close the loop in the > PC. I > > > think > > > you get snoother motion (which can translate to better surface > > > finish), > > > and you also have more advanced alogrithms available. The PID > > > software > > > in EMC2 is actually PIDFF - it has feed-forward terms that can be > > > used > > > to get better performance under acceleration. > > > > > > >Thanks VERY much for your help and advice.. > > > > > > > > > > > Sure. I just hope I'm right :) > > > > > > - Steve > > > > > > > > > --------------------------------------------------------------- > ---- > > > ----------- > > > 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 > > > > > > > -- > you can lead a person to knowledge > but you cannot make him think > ------------------------------------------------------------------- > ----------- > 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
