RSLogix 5000 Motion Control Instruction

I am trying to figure out the MCCM moves. There are three types; Circle, Via, and Radius. I do not understand the Radius type. I am confused on the value for the radius itself. The example in the Instruction Set reference manual gives a graph of radius 15 and -15. My question is relative to what? I know the values are supposed to be the radius value and a radius starts from the center of a circle to the edge. So where is the center in this example?

Thanks.

Consider the geometry of the radius in that example. A line that exists through the 2 defined points is a chord through the circle(s) and the centerline will be R distance away from those 2 points along a line that is perpendicular to the chord through its midpoint. In other words, given 2 points, only one, two or zero circles of radius R will exist that intersect those 2 points. Assuming the distance between the two points is less than to 2*R, than you choose which of those 2 circles that exist to use by specifying the Radius as either positive or negative. If the distance between the points is 2*R, than only one circle will exist and its center will be the midpoint of the chord.

Thus, specifing the midpoint is not required. It can be calculated knowing the location of the two points and the radius size. There will never be more than two circles that can exist and contain both points.

Hope that helps.

Yes, that helps. Thanks. I think I would prefer to use the 3 point method. The curve of the arc is not as important im my application as is the objects I need to miss.