Router-CIM must have geometry to make toolpaths from. Valid types of geometry are Lines, Arcs, Circles, Polylines, 3D Polylines, Splines, Ellipses, and Solids.
Blocks should be broken down into usable geometry. There are many instances where the Geoshape command will do this for you, but nested blocks can cause the Geoshape command to leave some geometry in a block form and that is not acceptable for cutting.
The first operation that the Geoshape command executes is to erase any existing objects on layer NC_GEO. This step is important because the objects on layer NC_GEO are used to make polylines on layer NC_SHAPE. These existing objects (if any) on NC_GEO are erased so that you don't get two or more NC_GEO objects on top of each other.
After the NC_GEO layer is cleared, Router-CIM issues the Geometry command. Geometry copies what you have selected onto layer NC_GEO. If you select Polylines or blocks, they will first be copied onto layer NC_GEO then exploded into their smallest element.
The second part of the Geoshape command is running the Shapes command.
The Shapes command now converts the NC_GEO objects into CCW Polylines on layer NC_SHAPE. The Polylines will be closed, if possible. The Geoshape command will fix contingencies or gaps within .02". This fix gap tolerance is adjustable in NCVARs, Geometric, *brng*.
These steps are necessary because only Polylines and surfaces on layer NC_SHAPE are suitable for cutting. Since there is blending, any lines that are not tangent or are open by more than .02" will be considered separate, open elements, and will generate their own start points (see the section on Start Point Edit later in this chapter for more information about start points). Gaps are fixed because the NCVAR called NCJOIN is set to True, and the NCVAR *brng* is set at 0.02 this is the largest gap to fix.
After completion of Start Point Edit, the Geoshape command will delete any geometry on layer NC_GEO. The Geoshape command will place NC_SHAPE Polylines over the original objects. The original geometry produced is not altered in any way by Router-CIM.
Since the qualities of your tool paths are determined by your drawing, only clean, continuous objects should be selected. Proper geometry definition is important to making accurate tool paths. If you do not like the shapes created, delete geometry on layer NC_SHAPE, fix the geometry on your original layer, and try again.
You can create your own Polylines on layer NC_SHAPE and use them for making tool paths as well. Certain rules apply if you make your own Polylines:
•Any polyline that you want to machine must be on layer NC_shape.
•If it is a closed shape it must go in the CCW direction.
Therefore, if you create a 2D polyline that goes in the CCW direction, you may place that polyline on layer NC_SHAPE (using either the AutoCAD Change or Chprop commands) and then Cut it.