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

Leon[_7_]

On 11/25/2013 9:24 AM, jim wrote:

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.

I'm going to take exception to your wording in your last paragraph.
Maybe I misunderstood.

I was an AutoCAD user for about 8 years, other CAD programs since 1986.

Anyway I am a furniture designer and builder. I have completely
converted over to Sketchup.

Now where I might be confused with your wording is that if I draw
something that is 4" long it is precisely 4" If I draw 4.015625, I get
a line that is 4 1/64" long, precisely.

Now if you are talking about a higher degree of resolution, I would a
agree that Sketchup begins to round after the fourth digit right of the
point. .0001

In woodworking drawings it it is typically not necessary to measure in
increments that are smaller than 32ths of an inch.".

While that is true, Sketchup can still very accurately draw in
increments that are 1/64" or greater. Anything with in that resolution
works out just fine.

And for what it is worth, You can type in precise distances just like
with a CAD program with in the resolution that Sketchup operates.

After drawing a complex piece of furniture with Sketchup, sometimes with
hundreds of separate components I use a plug in program that takes the
exact over all dimensions of every component and imports that data,
accurately, into an optimization program that has my inventory of
materials. I cut the components overall sizes using the optimization
program with no reference to the Sketchup drawings of the actual project.

I will reference the drawings for specific details for each component
that may need to have tenons, dado's, slots, mortices, ect.