Stuart Stevenson wrote: > > in screenshots 1 2 and 3 notice the squared trace on the beginning of the > accel and decel > I get this on all axes including the spindle and am unable to tune it away > I have tried many different combinations of tuning values > the best trace is the spindle with a max accel of 2 - this allowed a much > higher Pgain and stiffened the spindle considerably > the spindle has very little inertia as it drives only the gearbox and > spindle > I see the squared traces on the spindle > the ending traces work smooth until I start getting the tuning a lot tighter > then the traces tend to even out on all axes > do you believe this is a result of the marriage between the fanuc hardware, > ppmc and emc2? > motion of the axes feels, looks and cuts smooth and accurate - the following > error spikes are the focus > Well, not sure exactly what you are seeing. The first traces have ferror going up to .025", which is huge. Maybe these are feedsrates too high for cutting, but it seems like the servo loop needs to be much stiffer. Possibly this is a mismatch between what voltage is needed to command the drive for some velocity, and the output EMC is giving for that velocity. That would be a change of P.
But, those steps you are referring to, which are most obvious in the expanded ferror trace on screenshot 4 are something else. I MIGHT guess the drive is having a delay before responding to the change in velocity command. I haven't seen anything quite like that before. How are you getting the encoder info to EMC? Are you using the auxiliary encoder output from the servo drive? I wonder if this output has some extra delay - like the drive only updates position a couple hundred times a second. Ohhhh! Are these Fanuc drives with the serial pulse coder? The ones that have a backup battery in the drive for the encoder? Those require the drive to command the encoder to send a new position report. I have no idea what the update rate of these is. Also, I think the whole idea of this scheme was that the CNC control would send some signal to the drive and ALL axes would sample the position simultaneously. Maybe of you don't provide this encoder "sync" signal, then the drives only interrogate position at a lower rate. I'm just guessing at this, I haven't been able to dig up more than the most incredibly vague info in the serial pulse coder protocol. Jon ------------------------------------------------------------------------------ Beautiful is writing same markup. Internet Explorer 9 supports standards for HTML5, CSS3, SVG 1.1, ECMAScript5, and DOM L2 & L3. Spend less time writing and rewriting code and more time creating great experiences on the web. Be a part of the beta today. http://p.sf.net/sfu/beautyoftheweb _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
