On Wed, 2011-08-10 at 12:25 -0700, Tobias Gogolin wrote: > No problem if the servo solution is a bit more expensive than the steppers, > i do believe that i's the way to go for a more agile and useful machine!
There are basically two rates to consider. One is cutting feed rate and is mostly determined by the workpiece material, cutter type, machine rigidity, etcetera. This rate is usually considered slow. Then there is rapid, which is the fastest rate the machine can move without gross position errors and is used to get the axes to and from home, the workpiece or the tool changer. If the application is a hobby machine, rapids are not usually important, so one can gear reduce the axes to get higher torque. Rapids become important in manufacturing when part-to-part time can cut into the profit margin. > I need to understand a bit more about what means EMC has to 'close the loop'. > I suspect a motor current readout would help to see how hard the driver has > to try to achieve the required position? One can get an idea of the load by using HALscope or HALmeter to watch the following error. This difference between the requested position and the current position is part of the feedback loop that EMC2 uses to compute the next output command. Geckos and similar step/dir input servo drivers have this loop intelegence built in. I prefer to use EMC2's loop because it allows the integrator to configure and customize the loop, and use HALscope and HALmeter. > Funny I also found the same http://www.geckodrive.com/g320x-p-28.html and > was studying its specifications, but i couldn't find a way this one would > close the loop! As above, the loop is inside the Gecko. One could run the encoder data to both the Gecko and EMC2, but this is more advanced than I can comment on. > You say that it could be simply connected to 2 lines of a parallel port? > Even from the manual I can't find any evidence that the Gecko driver could > be used for closed loop operation! The standard way to do this is to set EMC2 similar to a stepper system so that it outputs step and direction, then set up EMC2 .ini file parameters to known safe parameters. I don't know if Gecko servoe drives have a fault output, but if so, this could be linked into EMC2. > Are there any better solutions? I suppose for pico or the FPGA controller > (which I like for its potential to do very quick responses processed > locally) I'll have to consult with their application engineering? The FPGA solutions from Pico, Mesa, Pluto-P are fairly well developed, so their documentation should be enough to get one through a standard installation. An FPGA is basically used to receive a velocity or position command from EMC2 (through the printer port or PCI slot) and turn it into a high speed PWM signal that would then go to a PWM input servo amplifier. The printer port could also be used to create PWM signals, but the printer port is considered fairly slow. My Shizuoka uses the the printer port (software) signal generator: http://www.wallacecompany.com/machine_shop/Shizuoka/ which works fine for stepper phase generation (or step/dir signals). Software PWM generation is only good for playing in the lab, but can be very informative. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ uberSVN's rich system and user administration capabilities and model configuration take the hassle out of deploying and managing Subversion and the tools developers use with it. Learn more about uberSVN and get a free download at: http://p.sf.net/sfu/wandisco-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
