Re: FWD: RP wish list

From: David Flynn (Plynetics Express Corporation)
Date: Wednesday, January 18, 1995

From: David Flynn (Plynetics Express  Corporation)
Date: Wednesday, January 18, 1995
Subject: Re: FWD: RP wish list
Beth of BD writes:
>I am a builder of mostly small parts and the 
>disappearing feature has gotten me a few times.
     I had an interesting conversation with Chris Manners (3D's head software
guy) about this very issue. In CSlice, if a feature's borders are closer
than 2 LBO's (LBO=Layer Border Offset), the act of line width compensation
results in degenerate geometry, which is simply discarded. I expressed the
opinion that he was arbitrarily throwing out *my* features. Chris was of the
opinion that since the offending geometry could not be created properly,
that it was ok to blow it away. The older Slice program, in contrast, would
leave such features intact, albeit fatter than desired. I personally prefer
this approach. 
     To be fair, CSlice performs line width compensation much more efficiently
than Slice. Also, the need to use LW comp is a fact of life - line widths
being finite. The problem is somewhat amplified by the epoxy resin with it's
low Dp value (Remember, Line Width ~= (Beam Diameter)*SQRT(CD/2Dp) ).
SL5170's Dp is a relatively low 4.5 mils, resulting in wider lines for a
given cure depth as compared with some of the older resins with their Dp
values of 6 or 7 mils.
     What's the answer? This is a tough one, since we are up against real
physical limits. Higher Dp's would help. A smaller laser spot size would
help too, but that's not always desireable. I believe that smarter software
is a must, but if you don't want the software to be making too many
decisions, more user involvement in the slice process would be required -
also not necessarily desirable.
     Any thoughts?
Dave Flynn

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