i think... On 03/01/17 09:16, Charles Steinkuehler wrote: > On 2/28/2017 5:52 PM, andy pugh wrote: >> On 26 February 2017 at 22:46, Charles Steinkuehler >> <char...@steinkuehler.net> wrote: >>> The A and B Axis has no >>> dependency on the rotation of the base of the robot arm (joint-0). >>> >>> Is this the expected behavior? >> I don't know. >> >> I did notice that the C axis value changes when you rotate the base. >> >> Have you seen >> http://linuxcnc.org/docs/devel/html/motion/5-axis-kinematics.html >> ? > Thanks Andy, somehow I missed that document. I'd gathered most of the > info from reading through some of the 5-axis kinematics code, but it > still doesn't really address my problem. I think the closest it comes > is a couple of places where it mentions "These relationships are > typically used in the CAM post-processor to convert the tool > orientation vectors to rotation angles". To me that implies the CAM > needs to have knowledge about the machine and account for the > kinematics, but it seems like it's far better to do this on the > machine side (where all the kinematics and dimensions are known). > > Perhaps a different way of asking my question: > > Given two types of 5-axis machine, one with A and B pivots on the > spindle, for the discussion, some vocab :-) this is 'knucklehead' like a wrist > and one with A and B pivots on the table, this is a 'trunnion' config > would identical > gcode be expected to produce identical results on these two machines? i dont think so, but that can be proven if we get two such machines together with a single part to execute really, wether the same gcode or different... it doesnt affect the rest of this thought > > On the machine with the pivot on the spindle, operation seems > straight-forward: Set the A and B angles, then move around in XYZ to > machine your part.
> On the machine that pivots the table, however, after setting A and B, > if you move around in XY, the Z axis will need to be coordinated with > the part position (since the part is now tilted, moving in X and Y > also affects the effective Z position). > > So is this difference handled in the kinematics, (i think) the kins have to handle the difference 'handle' meaning the relations of the joints for machine motion is in the kins ( which is a description of the joint relationships ) in the 'knucklehead' case, the tool axis ( line thru the cutter center ) is hypothetical ( aint up/down left right inout xyz ish ) in the 'trunnion' case the tool axis is simple cartesian and the workpiece attitude can be aeroplaney pitch yawed will AXIS produce the correct visual given the correct kins? dunno, but it can be tested, but (i think) AXIS is not a proofing tool will a vismach animation follow the correct kins? hmm i DO think so, given that vismach needs a lot of the relations that the kins would contain (also I've modeled a few multi axis systems in vismach ) will a CAM system produce the ( or 'a' ) good path given the _same_ kins, well (i think) its broke if it dont and, the trunnion is not always just 'posed', often its dynamic. (i think) the CAM has to know the same set of kins and react to corner cases and two-answer problems the same way it only works if both the control and path generator have the same idea how to get to grandmas house it only works if both the control and path generator have the same kins a control and cam system is usually a marriage, ( doesnt Siemens own NX now? hehehe ) > or is it expected to > be handled by post-processing in CAM? just my 2c tomp tjtr33 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
