Saturday, October 22, 2011
Seen on IRC yesterday. The python-scripting capability of FreeCAD(a Qt + OpenCascade based free CAD-program) allows calling opencamlib for toolpath-calculations much like is done from HeeksCAD/CNC(a Wx + OpenCascade based free CAD-program). Cool. Another screenshot with waterline:
If you calculate toolpaths around a very narrow and 'pointy' triangle you will get toolpaths in the shape of the inverse cutter - the "Inverse Tool Offset". Here I've plotted the basic operations, in red/blue drop-cutter which drops the cutter down along the z-axis until it contacts the triangle, and in cyan waterlines which are [...]
Here's a picture which compares the waterline toolpath for different cutters around a single triangle (cyan). The outermost path (red) is for a cylindrical cutter where we always make contact with either the shaft of the cutter or the circular rim/end of the cutter. Next is the yellow line for the toroidal or BullCutter, followed [...]
I'm not sure why it has taken so long to get the push-cutter methods for ConeCutter written. You would think that the cylindrical, spherical, or toroidal cases are at least as hard. Somehow I have just avoided working on the cone-cutter... The easy part is as usual contacts between the cutter and the vertices of [...]
As noted before, the waterline operation consists of radial cutter projection ("push cutter") along fibers/dexels, followed by a weave/grid construction, and contouring to produce the final toolpath. Like so: The new Weave2 class builds up a half-edge diagram in a smart way, maintaining "next" and "previous" pointers for each edge, so that the green toolpath [...]
I've written a new Weave class for opencamlib which makes the waterline operation faster. The first test-case is a single triangle, and we calculate a number of waterlines at different z-heights using a ball-cutter: The second test-case is the Tux model where we calculate a single waterline at some z-height. Note how using the chosen [...]
Thursday, February 17, 2011
The four basic cutter shapes in opencamlib are CylCutter (cylindrical or flat-endmill), BallCutter (spherical), BullCutter (toroidal, filleted-endmill), and ConeCutter (cone, "v"-cutter). With CompositeCutter it is then possible to combine these four into sensible combinations (such as the APT-tool). Below the combinations where the outer part of the cutter is conical, and the inner part is [...]
Friday, February 11, 2011
Some notes on the Sugihara&Iri 1994 topology-based algorithm for incremental construction of the voronoi diagram for point sites. (A) We start with initial VD for point sites that have already been inserted. We want to insert a new site, shown as a yellow sphere. (B) We then find the VD face to which the new [...]