On Wed, Mar 5, 2014 at 9:42 PM, sam sokolik <sa...@empirescreen.com> wrote:
> Ok - I finally got a chance to test some more real hardware. This is a > bastard router that has 3 different steppers/drive (it was a converted > step/repeat machine.) I built robs latest (RC3) from the linuxcnc git > and ran some of the test programs. some good news one bad. > > Good news. The motion is very smooth. The program I was testing was > the LHchips4.ngc. It sounds very nice. > > http://electronicsam.com/images/KandT/testing/LHchips4.ngc > > I found one issue. A cutting profile containing more than 1 axis will > only go as fast as the slowest axis. This machine has 3 different axis > velocities > > X 150ipm > Y 78IPM > Z 50IPM > > On the 'belly' of chips - there are long x-z profiles (mostly X moves). > The profiles would peak at 50ipm. (they should peak at something > between X and Z. The current TP actually runs that profile faster > (closer to 100ipm) There are long XY profiles also - they peak at 78ipm > but should peak pretty close to 150ipm in some areas.. > I think the reason this is happening is that I was a bit lazy with how I coded the velocity limits. The big issue is that the max velocity of a line segment can be higher than any one axis limit, as long as the net motion in each axis is less than the maximum. Take a simple case: (Assume X and Y axis Vmax = 100IPM) G0 X0 Y0 Z0 F99999 G1 X1 Y1 G1 X2 Y0 Each line here should be able to reach sqrt(2) * V_max ~= 144 IPM along each line segment. Now, imagine we round the corner with a tangent arc. At the midpoint of the arc, the velocity is along the X axis only, which means it can't exceed 100IPM. Unfortunately, you wouldn't know this just by looking at each line segment's max velocity. I took the easy way out and made the maximum velocity for the arc always be limited by the axis velocity. The good news is, I think there's a simple calculation to get a more optimal velocity if the angle between segments is small. Basically, we need to calculate the altitude of the triangle composed of the two lines' velocity vectors. The next few days will be a little busy, but it won't take long once I sit down and do it. ------------------------------------------------------------------------------ Subversion Kills Productivity. Get off Subversion & Make the Move to Perforce. With Perforce, you get hassle-free workflows. Merge that actually works. Faster operations. Version large binaries. Built-in WAN optimization and the freedom to use Git, Perforce or both. Make the move to Perforce. http://pubads.g.doubleclick.net/gampad/clk?id=122218951&iu=/4140/ostg.clktrk _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
