openvoronoi: medial-axis pocketing idea

[andyw]

Some work today with marching along the medial-axis and creating simple output along the way:

http://www.anderswallin.net/2012/02/towards-medial-axis-pocketing/

This is actually very similar to the medial-axis-walk class hacked together for V-carving. Just a slightly different way to walk along the medial-axis, and slightly different output.

I hope to hook up the paths into a pocketing-strategy as the next step. It would be nice to animate this with a cutting-simulator. If no better opportunity comes up I might write a simple pixel-mowing cutting simulation that shows how the tool cuts the pocket.

Anders

[Anders Wallin]

> I hope to hook up the paths into a pocketing-strategy as the next step. It
> would be nice to animate this with a cutting-simulator. If no better
> opportunity comes up I might write a simple pixel-mowing cutting simulation
> that shows how the tool cuts the pocket.

This shows the first pocketing-path I was able to produce:
http://www.youtube.com/watch?feature=player_embedded&v=X2IO1i0EQ3M

similar to V-carving, there are issues with edges between parallel or
nearly parallel line-segments that have to be solved before this will
work on a pocket of arbitrary shape.

The code is in my "ma-pocket" branch and is quite messy at the moment.
The c++ class that does this is only around 400 lines and fairly
straightforward, but then there's a lot of hackish stuff in the
700-line python script I use to produce the actual toolpath...

This strategy should work for closed or "internal" pockets where we
want to clear an area (possibly with islands) that is bounded by
un-machined stock on all sides.
A slightly different approach can be used if we have say a square
piece of stock and want to clear everything but an island in the
middle. I'll try to do a demo of that next week maybe.

Anders

[andyw]

I've made two new videos that show the latest progress:

http://www.youtube.com/watch?v=_Qr8tZXGXZU
and
http://www.youtube.com/watch?v=lfIU_gv0iB8

There are at least two problems:

- when the pocket rapidly narrows from wide -> narrow there is overcutting. This happens during the bi-tangent cuts from one MIC to the next MIC.

- towards the end of a cycle in the MA, the algorithm is not aware of the fact that the start of the cycle has already been cleared, so a lot of air-cutting happens.

I thought I had some good ideas for "external" HSM-pocketing, i.e. where we cut the stock from the outside and leave just an island. But I haven't been able to write down any code for this yet. Does anyone have any good ideas?

This shows the idea http://www.youtube.com/watch?v=KpYXPwQSzWw

Anders