Re: Adaptive slicing problems.

From: Floyd Roberts (
Date: Mon Feb 24 1997 - 18:59:12 EET

Might the first problem be solved by not using STL files in the first
place? Would DXF files be more workable?

At 12:49 PM +1000 2/24/97, Raymond Hope wrote:
>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
> Home +61 7 3217 7410
>Facsimile +61 7 3365 4799

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