Andrew Ayre wrote: > Hi, > > I have a gantry style machine with three axis. The X and Y axis have the > same motor and the same nut and lead screw on each). I am testing the > machine using manually entered commands into AXIS such as: > > G01 F80 X1 > G01 F80 X0 > > When manipulating one axis at a time (no cutting, just moving around) I > have found that I lose steps at different feed rates for each axis. > > X - lose steps at 148 ipm > Y - lose steps at 81 ipm > > I performed the real time tests on my PC and the theoretical maximum > feed rate for both these axis is 285.72 ipm. > > What factors could stop me from operating the Y axis at the same speed > as the X axis? > > What factors stop me from operating both axis at 285.72 ipm and how do I > adjust the ini file to compensate for those factors? > > Here are my calculations: > > ------------------------------ > Set BASE_PERIOD to 12us (hold time) + 93us (PC latency) = 105us = 105,000ns > > Therefore maximum step rate is 1 / (2 x 105us) = 1 / 210us = 4,762 steps > per second > > The motor turns 200 steps per revolution. The lead screw is 5 threads > per inch = 0.20in pitch. 0.20in / 200 steps per rev = 0.001in per step. > Therefore 1 / 0.001in = 1000 steps per inch. > Maximum speed is 4762 steps per second / 1000 = 4.762in per second = > 285.72in per minute. > > MAX_VELOCITY and STEPGEN_MAXVEL for the X and Y axis should therefore be > 4.76. > The INPUT_SCALE for the X and Y axis should be 1000. > ------------------------------ >
All those calculations are for theoretical limits to the step rate. But the reason you are losing steps is much less theoretical. You are probably running out of torque. When step motors go faster, the amount of torque that they can produce drops. When the load needs more torque than the motor can make, you lose steps. It does seem odd that the X can go faster than Y. X has to move more weight (I assume that X is the gantry, and Y moves a much smaller weight across the gantry). But something is making Y require more torque than X, so Y loses steps first. Regards, John Kasunich ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Register now and save $200. Hurry, offer ends at 11:59 p.m., Monday, April 7! Use priority code J8TLD2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
