Re: [CAD_CAM_EDM_DRO] Polar Coordinate based CNC

Lee Wenger wrote:

>What all would have to happen to allow a CNC machine to be based on a polar coordinate system rather than a rectangular one. The big benefit to me would be that the single most expensive component of a router/plama type of system is the slides and drive components (the screws or rack/pinon not the motor itself) for the longest axis (for systems of the size/type I have in mind this would be to move a gantry). But I assume that would mandate a change to the controller so it could interpret g-codes as polar coordinates. Are there any controller packages out there currently that support polar-coordinates?
>
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This is called a robot, in the CNC world. Industrial robots use rotary
axes almost
exclusively. EMC was originally designed for robots, and does cartesian
machines
as a simplification. The one big problem with this is that it would
only work correctly
for ball-end tools. The machine can bring the center of the tool tip to
a 3-D point
defined in XYZ, but then you have to specify a multi-axis rotation for
the tool at the
end of the arm. Maybe this isn't as complicated as I think, but it
definitely does
complicate things, if you want to run a straight router bit down the
side of a board.
Now, if you restricted the robot to 2 rotary axes, the cutting tool
could be kept
square to the workpiece, if both arm pivots were around the vertical axis.
EMC could handle this easily.

Jon