Subject:
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Re: x210c01 ChromeSilver Drill 4 x 4 x 7
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Newsgroups:
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lugnet.cad.dat.parts
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Date:
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Sat, 13 Dec 2008 19:55:45 GMT
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Viewed:
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12152 times
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On Fri, 12 Dec 2008 08:58:46 GMT, "Philippe Hurbain"
<philohome@free.fr> wrote:
> > > Just to refresh my memory ( I haven't done any parts since 2951)
> Welcome back!
>
> > > The
> > > 48 primitives divide a circle in 48 straight lines, right? That would
> > > for a 60 LDU diameter mean that each straight line is approx 4 LDU's
> > > long, so using coneshapes each 4 LDU long would yield approx the same
> > > resolution lengthwise as diameterwise, right? That's only about 40
> > > cones, so maybe I'll go with 2 LDU.
> >
> > I do not understand correctly what you are saying.
> > If you use a cone primitive you can stretch it in all direction. There is no
> > need to use "about 40 cones". A maximum of 10 should do the same! You should use
> > for this the program "cones and rings" that calculates the needed cones by give
> > the minimum and maximum diameter and the length of the parts cone shape.
> >
> > cu
> > mikeheide
>
> I agree with Mikeheide, since the total curvature is low I think 6 cones would
> be more than enough!
When the curvature is the only concern, then yes, but I have to take
the screwshape into consideration, the closer I am to the ideal curve,
the easier it is to calculate the screwshape and avoid holes in the
part. Furthermore when thinking about the amount of lines required for
the screwshape, 4, 8 or 16 cones will not make a big difference to the
filesize. The problem area is the front of the part where it curves
the most, with 4 cones of equal length the difference between the cone
and the ideal curve will be more than one LDU at the worst place, this
could ofcourse be handled by using more cones in the front part, but
having cones of different lengths is not desireable when it comes to
calculating the screwshape. Taking into consideration the amount of
work and code that goes into the screshape, using 16 cones for the
baseshape does not sound overkill at all to me, and it will give a
difference of app. 0.2 LDU between the actual radius and the ideal
radius at the point where it differs the most.
As for the screwshape itself I imagine building it of quads, using
"48" resolution, that would mean 96 quads per revolution, giving
somewhere in the neighborhood of 800 quads, 1200 lines plus all that I
have forgotten. I am not at all concerned about spending a little
effort on the baseshape:)
>
>
> > > As for the screwshape, i plan to embed it slightly into the body in
> > > order to avoid "holes". I'll create a program that does the math and
> > > writes the lines for me.
>
> Seems a good approach. As for the edge line between screw and cones, Isecalc
> will provide it instantly! (It would be difficult to create it with your program
> since this lines depends on the various cone sections).
I will have to look into that, it sounds interesting.
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Message is in Reply To:
 | | Re: x210c01 ChromeSilver Drill 4 x 4 x 7
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| (...) Welcome back! (...) I agree with Mikeheide, since the total curvature is low I think 6 cones would be more than enough! (...) Seems a good approach. As for the edge line between screw and cones, Isecalc will provide it instantly! (It would be (...) (16 years ago, 12-Dec-08, to lugnet.cad.dat.parts)
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