arcs aren't supposed to have angles! right??

[amontgom]

ok,
first the machine.
i have just completed the retrofit on my supermax ycm-42 ( anilam eagle km-750).
ball screws on every axis in good condition and belts properly tensioned.

i replace the burnt servos with 4.5Nm nema34 steppers.. and i'm driving them with leadshine 850 stepper drivers.. ( a very good fit)

i am running ( testing right now) mach3 it is configured correctly and i can precisely locate any position on all axis within .0002 +/- .

spindle is turning around 3000 rpm with no noticeable vibrations and is true and properly trammed.

the computer is an older gateway laptop ( no watchdog issues( i am a former intel engineer))
the cable length is short and shielded.. no appreciable emf/rfi issues ( the emf issues are on the other side of the mill and inside of a metal box...

the problem...
when running some test code attached below.
a knob..

the z axis performs well but
there seems to be problems with some angling within the arcs ...
it resembles some backlash ..
i thought that there is no appreciable backlash with balls crews... right??/


the code i am using for testing...is attached

it appears to be a file with its arcs converted to millions of little angle segments...

the resultant output however looks like half of the segments were skipped...
or every other 3 positions were actually cut....
with the most significant areas being along the axis intersections.


i'll try to get some images up soon.. ( i loaned my camera out for the week..)

thanks in advance..
allan

[hub]

Try using gcode G2. (Or G3 for CCW arcs).

[Joe S.]

Hello,
Your code is typical of some CAD programs output, which do not use G2 G3 command structure. G2 G3 allow your machine controller to determine how to make the cut.
As I see it, stepper motors speed is a matter of how many steps per minute the control sends to it, however each step is a rapid movement, whereas a servo has the ability to reduce speed in a more linear fashion, due to throttling it's power to the motor. The program you have shown us very likely has movements smaller than the resolution of your machine and is why it is cutting in "little angles". I am pretty sure MACH3, has the ability to generate suitable movement using steppers based upon the parameters you have given it using G2 G3, allowing for the slow/rapid nature of stepper motors, probably using MicroStepping techniques.

[hub]

Arcs, Circles and curves etc are always "stepped", no matter what. Unless drilling, boring etc..

It's a matter of resolution how accurate the arcs are going to be. Of course back lash would make it worse.
Also what file format did you use? DXF can produce "arcs" that are actually many short straight lines forming the arc/circle. Maybe it's a software issue?