DIYbanter - View Single Post - CAD for simple 3-D metal & wood projects?

jim

wrote:

On Sun, 24 Nov 2013 18:22:26 -0600, jim
wrote:

wrote:

On Sun, 24 Nov 2013 17:08:14 -0600, jim
wrote:

wrote:

People have been making things flat or round to that level of
precision for ages.

Flat and round (spherical) are trivial problems and as you note it's
been done for ages, at least since the middle ages.

And there isn't much advantage in having a
CAD model for those shapes.

There isn't much reason to have a CAD model for a board, either, but
when you want to put a few dozen of them together, having a CAD model
gets rather interesting.

Other shapes are
more difficult, as is size.

And it is doubtful there is anyone reading this who
is cutting complex shapes from CAD models with precision
held to tenths.

Huh??? Have you ever heard of a mirror, or lens, system? Please
explain your statement?

How many have you modeled in CAD and then manufactured
to within tenth of the designed part?

You still make no sense. Are you saying that precision machining
doesn't require the same level of modeling that sloppier work does?
Really?

First of all most of the examples of precision that have
been given involve no 3d modeling at all. And the rest
appear to be at best 2d modeling (e.g.. a lathe profile).

I'm saying that any CAD system can produce geometry that
is far more accurate than any manufacturing process. If a 3d
computer model has dimensions that are different than what you
like them to be, it is because of the input the software was
given, not because the software is sloppy.

A program like Sketchup caters to people who want to
model something that looks good without paying much attention
precise numbers. But that doesn't mean it is sloppy. It just
means it is not as easy to hit the exact numbers you may want as
in other programs that cater to people who want models driven
by precise numerical inputs instead of mouse actions.