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Prevailment

Friday, November 18th, 2005 at 7:03 pm Written by:

The picture is the results so far. The nasty bits in the toolpath are disconnected fragments rather than glitches, which is good. That means they can be filtered out. Glitches are spikes in the toolpath, which makes them far harder to deal with. I think I can remember it being this way in Machining Strategist or Depocam, but I did my best to forget about it.

Scallop toolpath better

The const scallop algorithm has reached a point where I need a break. Surprisingly, the development of it, with all the fragmentary cases and fiddly bits, felt as though it was going down all the same paths as before. There are millions of little precision values that can make or break the result. It feels like I could teach it to someone as a lecture course over 8 hours. About the same as for classical group representation theory, only a lot less intellectually enlightening.

Maybe that’s an exaggeration. Teaching software is not like doing mathematics. You don’t have to write the code for the students in the same way as you have to write mathematical proofs.

Anyhow, the bulk of it seems done now, although it’s not the fastest implementation on the planet. I think I’ve run through all the important components of the algorithm in a week rather than the month it took the first time.

Work to do:

  1. Ensure all glitches are removed.
  2. Make it run with proper cutter location, rather than simply locating a ball nosed cutter against the points on. (I’ll have to rely on Cimco’s proprietary code until I find a reason for wasting my own time on a potentially public version).
  3. Make it faster. This is always going to be the demand. But it is not worth doing until there are no glitches. The right answer slow ought to be better than the wrong answer fast.

So it’s time for a break from this. I should get back to some of the real stuff instead of this repeat work. By that I mean the adaptive machining. Having gone into this depth, I can conclusively say that the traditional const scallop machining algorithm is not the way forward. There’s got to be a better theory.

1 Comment

  • 1. Francis Irving replies at 19th November 2005, 12:01 pm :

    So the adaptive stuff uses a braitenberg vehicle, but it is moving at a constant Z level? Presumably you’ve thought about using something similar for an effect like constant stepover, but with more robust adaptive algorithm. Is that possible?

    For the vertical scallops by braitenberg you’d need a material model though I guess. 2D braitenberg can use quite a simple model (one of your meshes), but one with height changes needs more.

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