Re: CNC robotic welding arms

If your controller software still thinks its driving an XY machine
instead of a two jointed planar arm, it will not interpolate
correctly.

For instance, if you want to cut a straight line from a position 45
degrees to the left of the base to a position the same distance from
the base but 45 degrees to the right, your G code would command the
base axis to move +90 degrees and the elbow joint zero degrees.
Instead of a straight line you would get an arc whose center point is
the base of the machine.

A way around this is to break things up into very short segments line
a constant-contouring file. A better way is to use a controller that
knows what kind of mechanism it is driving ie feed it XY and let it
do the rectangular to angular conversion itself. I understand that
EMC can do this easily.

- Tom Scarince

--- In CAD_CAM_EDM_DRO@y..., "rainnea" <rab@r...> wrote:
> These would seem in theory to be ideal for plasma or laser cutting.
> Realising that calculating the movement coordinates can be pretty
> straightforwards set me thinking about these robot arms in the
first
> place. Just generate G Code that contains all rotational
coordinates,
> and most any controller would work in the same way that many folks
> use their controller's Y-axis to rotate a rotary table.
> However, how the controller handles the velocity calculations is
> another matter when you start using rotational axes, as the
> controller really needs to know the distance it's moving to
calculate
> the velocity. ie. many controllers have problems with a large
> rotational move combined with a very small linear move.
> Can anyone shed some light as to how high-end controller handle
this
> problem ?
>