Adaptive slicing problems.

From: Raymond Hope (
Date: Mon Feb 24 1997 - 04:49:46 EET

Hi all;

My name is Ray Hope. I've been working on slicing procedures for layered
manufacturing, and am using layers with sloping boundary surfaces to
eliminate the stair case effect. I have recently been working on adaptive
slicing, and have come across some cases that can cause problems. So I
thought I should call on the greater collective knowledge of the group and
see if we can come up with some ideas.

Note I am obtaining the definition of parts from B-spline surfaces. Layer
error is approximated from the radius of curvature and angle of the
surface normal.

Problem 1.

 Joins between two or more surfaces, and vertices can cause the error
approximation to give incorrect results. Previously published work (by
others) has tried to solve this problem by slicing the part so that the
surface joins coincide with layer joins. However this can only work if the
surface joins are in the same plane as the layers. In many cases where a
part is defined by two intersecting surfaces, the intersection curve is not
in the layer plane. So what do we do?

Problem 2.

 The method mentioned above to predict the error, produces a predicted
error much less than the true value near inflection points. This is
because at an inflection point the curvature becomes zero, and is also very
small nearby. So how should we predict error near inflection points?

I look forward to hearing some interesting suggestion from all of you.

Ray Hope
Department of Mechanical Engineering
The University of Queensland
Brisbane QLD 4072

Ph +61 7 3365 4179
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