CAD for simple 3-D metal & wood projects?

[none]

I don't have Skectchup yet, but I sure would like to see a few pictures of partial construction of the face frames in the back of a unit.

[Leon]

Ill post some more pictures after breakfast to show that detail.

[jim]

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.

[Richard]

Huh? I guess you didn't check out my offerings?

Lofted to .01 inch, since traditional nail in the floor lofting considered 1/8th inch superb fairing.

[Lloyd E. Sponenburgh]

jim fired this volley in news:dZCdnTMPefxT9g7PnZ2dnUVZ [e-mail]:

You hit it right on the head. That's why it's not suitable as CAD, even though it's an extremely useful system for visual presentation.

And although I might not have made it clear... that was my whole point on base-1.

Lloyd

[Leon]

Details of the back face frames, 16 pictures. I added a few captions to explain what is going on but you should get the idea.

I showed my dado extender jig, e-mail me and I-ll explain further. This is kind of a trade secret. stupid simple but a time saver and a must when attaching any face frame to any side, top or bottom panel.

Any way, follow this link and scroll left and right to see the set of pictures.

[Jim Wilkins]

"jim" wrote in his blissful ignorance

"The axis position feedback system uses a 0.5-nanometer scale to reliably track axis motion commands programmable in steps as small as

10 nanometers."

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.

jsw

[jim]

I did look. And its nice work. But you aren't claiming that you took a 3d model and produced a part held to tenth accuracy. If you can achieve .01" accuracy in manufacturing that hull to match the 3d model, that would be extraordinary accuracy.

[Swingman]

Except that what you quoted as justification for your "whole point" is incorrect, therefore you're still wrong.

With SketchUp, "precise numerical inputs" can be input to the same precision as AutoCAD, by simply using the keyboard.

Try again ...

[Leon]

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.

[Leon]

Lloyd, you simply do not know how to use Sketchup to its extents. Your comments show your ignorance about Sketchup. I'm not trying to belittle you but most every thing you have mentioned about Sketchup is inaccurate.

Again, I switched from AutoCAD to Sketchup about 6~8 years ago because I get the same needed resolution and accuracy.

I am a woodworker and routinely work with pieces that measure in 1/8" resolution however the program is quite capable of accurately and quite quickly drawing a box that is 4 1/16 x 5 3/64 x 9 19/32.

don't knock the program until you actually learn how to use it, not just play around with it.

I would be more than willing to show you some detailed drawing that I have done with Sketchup.

[Swingman]

Only for presentation, and depending upon the resolution you have set.

For dimensional computations, SketchUp still uses its internal accuracy, the same as AutoCAD.

[Leon]

Speaking of which, I have a plug in for chaining the units, precision of the units, type of units, etc with out having to open up the Sketchup Dialog box.

[jim]

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.

[Swingman]

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.

[jim]

Yes. I said you can do it if you want to, but the program is obviously targeted at people who want to use the mouse for input.

It looks like it can take much more precise input than that. There is a setting in the units dialog box. And you don't have to work in fractions. You can switch to decimals and input numbers down to a millionth of a mm. Internally, the data is even more precise than that.

[Swingman]

Ayup ...One would hope that their accuracy in their work indeed exceeds their accuracy/misconceptions about a program with which they obviously have little familiarity. ;)

[Jim Wilkins]

You are demonstrating my point that petulant misfits will snatch at any excuse to belittle capable people.

[Richard]

I'm sorry, Jim, but this sounds like arguing just for the sake of arguing.

Drafting (or modeling) and machining are two distinctly different disciplines and outside of a few hobbyist, damned few people do both.

A fiberglass boat's hull is seldom held to anywhere near that accuracy. If you check carefully you will usually find all manner of inaccuracy in construction. Missed dimensions (by INCHES some times), asymmetry, misalignment, etc, that the eye simply does not catch.

On the other hand, large steel ships MUST hold that kind of accuracy. Those ships are built in smaller sections called "lifts", which are then stacked together to form the finished structure. They HAVE to be built that accurately just to fit together.

For what it's worth...

[Lloyd E. Sponenburgh]

Leon fired this volley in news: [e-mail]:

If I were using it for woodworking, I assume those accuracies would be adequate, if a little gross for a CNC router...

But I work daily with sub-thousandth measurements. Do you really understand how funny dealing with "thirty-secondths" sounds to a metalworker? Today, I had to lay out a complex, multi-curved cam slot a half-thousanth wider than a bearing, because the bearings that ride in it work the plus side of their tolerances -- and the bearings are spec'd by the customer. Even two thousanths of an inch would cause them to track wrong.

I also am not belittling what you do. I've done it (in a prior life) with very nice results on some 'fine' reproduction furniture. They're just not the same games, that's all.

I have -eh- maybe 250-300 hours building large-scale models in Sketchup;

100 meter scale. Maybe I could finesse it into doing 1/4" stuff to tenths of a thou.; but why, when there are CAMs out there well-adapted to what machinists do? Why use an axe where a scalpel is called for?

Lloyd