Ahhhh, learning to build with expensive wood. Buy a beautiful piece of
walnut, bring it home and mill it to thickness, straighten one edge then
the other, and cut to length. Oppps, 1/16" too short, cut it again,
still too short. Redraw the plans slightly smaller, start over....
Eventually it is built and you sand the beautiful surfaces through 3
grits and it is finally ready for the finish. Open the can and roll the
"The axis position feedback system uses a 0.5-nanometer scale to
reliably track axis motion commands programmable in steps as small as
I've watched a large aspherical Germanium infrared camera lens being
diamond-turned to a mirror-like submicron finish on a CNC lathe.
All you demonstrate is that YOU don't know how to do this.
Yes that machine should be able to cut 3d parts so they match
the 3d computer geometry to within a tenth.
However, the CAD model of the part can be made a million times more
accurate than even that machine can manufacture.
I didn't say there were no way to produce complicated 3d
parts that are within a tenth of the 3d CAD model.
I said that I doubt anyone reading this was doing that. You
still haven't changed my mind.
Turning something on a lathe doesn't need a 3d model.
That is not 3d machining.
And watching someone else do it doesn't count as doing.
Turning an *aspherical* lens does need a model, and a very
precise and mathematically complex one at that, to cause it to focus
where it should. And you can't check a Germanium lens by the techniques
used for visible-light lenses -- they are opaque to visible light, so
you want it cut right the first time. Same applies to silicon lenses.
I've seen both used in various experimental Infrared cameras.
He did not say that he was watching someone else do it. He was
watching the *machine* do it. No *human* does it with CNC. At best
s/he feeds the data to a program which generates the motions necessary
to produce the surface to feed to the CNC machine tool.
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
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.
Here, do this:
Open SU, go to Go to Window|Model Info|Units|Fractional and choose 1/64"
or whatever Format you desire .
Now, draw a rectangle of any size using the rectangle tool
Select the rectangle and right click Area|Selection
You will see a number representing the area of the rectangle you
selected to .000000 precision.
No, can you think/tell me what that converts to as a fraction off the
top of your head? LOL My calculated industries calculator can't
I like to see fractions, on my drawings, that I can actually come close
to reproducing. ;~)
A bit off topic, I checked the outside temp a few minutes ago,
42.51232367 degrees F.
Weather is usally single digit precision. Usually.
"A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet,
balance accounts, build a wall, set a bone, comfort the dying,
take orders, give orders, cooperate, act alone, solve equations,
analyze a new problem, pitch manure, program a computer,
cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects."
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