> I'm pretty sure the impact of acceleration is that LCNC always wants to be > sure it can stop at the > end of the 1-segment look-ahead. If the accel (decel) rate is slow, it can't > go very fast before the > stopping time extends beyond the length of the look-ahead.
I suspect that servo machine owners don't notice the poor CV that results from this limitation, as their accel settings are likely much higher than the stepper machine owners. I believe that this is the likely cause of the performance difference between Mach 3 and LinuxCNC's TP noted by Sam. As long as we're discussing the TP, however, there also exists an issue with line-arc transitions. I reported this a while back, with the simple test below. The code that has only line-to-line transitions runs 40% faster than the nearly identical shape with line-to-arc transitions: Running LCNC 2.5, copy the sim/axis config to your local configs, then change the max_acceleration for axis 0, 1, and 2 to 1.0 (previously 100): MAX_ACCELERATION = 1.0 Then run both of the following programs: % (1 inch square) G90 G54 G20 G64 P.125 G0 X0 Y0 Z0 G1 Y1 F50 X1 Y0 X0 m30 % (1" square with rounded corners) G90 G54 G20 G64 G0 X0 Y.25 Z0 G1 Y.75 F50 G2 X.25 Y1 I.25 G1 X.75 G2 X1 Y.75 J-.25 G1 Y.25 G2 X.75 Y0 I-.25 G1 X.25 G2 X0 Y.25 J.25 M30 The tool path on both programs is nearly identical because the square with hard corners is run at G64 P.125. http://static.inky.ws/image/3839/Screenshot-rounded_square.ngc%20-%20AXIS%202.5.0%20on%20LinuxCNC-HAL-SIM-AXIS.png If you watch the velocity display you will see that the program with only line-line transitions (1" square) reaches 35 inches/min - while the program with line-arc or arc-line transitions (1" rounded square) runs at only 26 inches/min. The arcs are certainly tangent here, and no one can point blame at the CAM software (although you're welcome to point blame at my poor hand coding style). Daniel Rogge ------------------------------------------------------------------------------ How ServiceNow helps IT people transform IT departments: 1. Consolidate legacy IT systems to a single system of record for IT 2. Standardize and globalize service processes across IT 3. Implement zero-touch automation to replace manual, redundant tasks http://pubads.g.doubleclick.net/gampad/clk?id=51271111&iu=/4140/ostg.clktrk _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
