Wow! Thanks John. This is a very nice explanation. Was looking for it for a while. Can you put it in some sort of wiki?
Thanks again, Ed [EMAIL PROTECTED] wrote: > Eduard Nesterov <[EMAIL PROTECTED]> wrote: > > >> I am running emc2.0.5 with Xylotex board and Taig mini mill. Before I >> adjusted SCALE_INPUT parameter I was able to run sample nc file without >> problems. After I set SCALE_INPUT = 32000 (200*8*20) 0 "joint 2 >> following error" keep showing up. >> I started emc from the terminal and got the following error description: >> emc/task/taskinf.cc 787: Error on axis 2, command number 1321 >> >> Could anyone help me understand what is going on. >> > > You are asking for more steps per second than than software step generation > can give you. > > What is your BASE_PERIOD? The default is 50000nS, or 50uS. That means > the "step" signal can change no more than once every 50uS, or 20,000 times > per second. Since every step pulse has a rising edge and a falling edge, > you can't generate more than 10,000 steps per second with the default > BASE_PERIOD. If your scale is 32,000 steps per inch, and you try to move > at 0.5 inches per second, that means you need 16,000 steps per second. > You won't get it, so the motors fall behind and you get a following > error. > > The default value of BASE_PERIOD is very conservative, since making it too > fast could drastically slow down or even lock up your computer. But you > can probably reduce it from 50uS (50000) down to 25uS, 20uS, or maybe even > less. At 20uS, you can have 25,000 steps per second. > > It takes very simple math to see what the limits are: > > First, try running EMC with smaller values for BASE_PERIDO, until you > find a "good" value. "Good" means the lowest value that doesn't cause > significant slowdown of the computer. Try 25000, then 20000, 16000, etc. > Lower it a bit at a time, start EMC, and see if the system feels "sluggish". > If the mouse starts to get jerky and windows respond slowly, raise the > value a little bit. If you are a little too low, you get slow response. > If you go a lot too low you can lock up your system, so go in gradual > steps. > > Once you find a BASE_PERIOD that works, you can calculate the maxiumum > step rate. It is 500000000 / BASE_PERIOD steps per second. > > The next step is to calculate your maximum speed in inches per second. > (Or mm per second, but since your scale is 32000, I bet you are using > inches.) The maximum speed in inches per second is the max step rate > that you just calculated, divided by your scale. > > For example: > > Suppose you find that the lowest BASE_PERIOD you can use is 19000. > Max step rate = 500000000 / 19000 = 26315. > > Max speed = 26315 / 32000 = 0.822 inches per second. > > You always need some "headroom", so in this case I would set the > max speed to 0.75 inches per second, which is 45 ipm. > > Regards, > > John Kasunich > > > ------------------------------------------------------------------------- > Using Tomcat but need to do more? Need to support web services, security? > Get stuff done quickly with pre-integrated technology to make your job easier. > Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > > > ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
