hello pette but of course cam systems can output smooth splines, at accuracy beyond what a cnc system can handleWhen the cam system creates a spline it will not be initially smooth
if machine is expected to interpolate nurbs, then if inital code :in which the derivative of the curvature is looked at and then the curve is adjusted until it is to the required smoothness
... has nurbs g-code, and :
...... no more constraints are there, then those nurbs from g-code will simply pass through, no smoothness will occur
...... there are constrains, such as :
......... "alowable error", then only if "alowable error > 0" a set of nurbs modeling equations is being produced, and it's solutions will pop up within those initial constraints
......... "maximum feedrate", then solution from the modeling equations will be analyzed also cinematically, and variable feedrate will be mapped in advance
... does not have nurbs, then much more constraints will be used; its a more dificult case, because lack if initial data
is possible to use a full set of constraints even if there are nurbs g-codes, but this means that the cam software and/or programer can not be trusted, and in this case, there will be much bigger problems to worry about
if there is a point coming from the toolpath planner, then that point is there to be executed, not to be rejected as being out of tolerance; there is no time/no use to check if a point is somewhere where it shouldn't be ... this shows that the planner is screwed; there is no debateThe MC decimates the points that either create an out of tolerance path
what the mc does, is that it will try to reach that point closer or a bit distant, thus each point will be checked
but the toolpath planner may add/shift/delete points, only if smoothnes algoritms are used ; is the mc job to be sure that what comes from the planner will be executedA MC cannot add points
it can handle also uncontinous paths ... there are tolerances for such things, as there are for arches g2/g3The gcode tesselator can only tesselate continuous paths nothing more
as for nurbs, there are tolerances also for curvature g1 g2; g3 g4 comes out naturally after solving the associated equations
only cam software with mcs algortims can do that, but again, is not round&round, is one way shot, and this is very very rare; common cam softwares can't do itThe CAM has an adaptive loop that goes from toolpath creation to toolpath analysis and round and around until it meets the desired settings. Some software runs forward kinematics and reverse kinematics.
to simply put it, the cnc may toogle between a few cinematic modes, while a cam software is a bit lost, since it does not know how the cnc will behave; many people are satisifed if they have a working postprocessor, and very very few are into mcs algorithms; why should they be ?
a cam software may detect a possible interference, but can not predict a crash; a crash can not be simulated, and is the mc duty to react if it senses a crashThis is good for crash detection
there are the initial factory settings, but also dynamic settings may occur on request, thus they tune themselfsOtherwise you do motion trails ramping up accels until the machine complains then back down a bit. This is not an ideal way top tune the motion controller. Servos have tuning programs that do a good job.
it is not about an ideal way, but about finding fast the settings that suits the machine for that instant only
they can ramp up at medium value, analyze data, then adopt a biger value that is safe for actual conditions, but still lower than full capability; thus it can go even faster
no, such tasks are not done by computers, they can't keep up; is machine's electronics, that simply may use the computer as a side, to show dataComputers are fast enough these days to do all the work while looking ahead.
those high frequency loops are not to be handled by clasical computers
post processing is an atribute of the cnc, without conections to camPost processing is relative to the CAM work
nurbs are even harsher, with more inpredictable changes of curvature, so to say; depends also on cnc dinamic profile, and how curvy the nurbs is ... but simply to put it, there is much more flexibiliy to the nurbs, rather than lines/arches, so the system will work harderYou keep talking about lines and arcs they are not smooth. They are discontinuous with infinite changes of curvature at each end. This creates infinite acceleration at each end, this is no good for smooth motion.
the frequency of the loop is similar for line/circle/nurbs/steady ( thus machine is not moving ), but it's reaction is, or diff control, is more pronounced in high speed nurbs or hsm; to generalize, is harder with higher speeds on low radius profiles, and this can be seen
i don't talk about systems that require a laptop i think i just had a revelation ....That's how TinyG, your machine and all others do it.
i can create programing software, and 2d cad; also, i can record feedback loop data at each 0.008 - 0.015 seconds; if it matters, right now i am working on smoothing toolpaths from program files generated by cam softwares / kindlyDK do you use a CAD/CAM system or are you programming directly to the machine in gcode? if you use CAD cam what do you use?