Constraints/Dimensions or No Constraints/Dimensions in 3D Modeling

[GreenTwin]

I remember that. Well vaguely. I think one flavor was memory / processing based in the good old days. The other was some kind of pre printing rigmarole.

Yes, your link says the limits was designed to to avoid the dreaded "regen".
I recall the regens using AutoCad on a 286 machine could be 20 minutes, and basically had to be avoided at almost any cost.

We ran the 286 machines for a few months, and then they found some hyper-fast video cards, which basically was a computer on a card, with a lot of memory, and a lot more processing power than a 286. The video card was not constrained by the 640k memory like an IBM PC.
The video card was $4,000.00, and than was in 1986 money, or thereabouts.
A 286 with the video card was well over $12,000.00 as I recall.

With the video card, regens were not bad at all.

We used AutoCad and VersaCad in the same office, and they were not compatible programs/files as I recall.
We had AutoCad-VersaCad user wars in the office, with lots of bloodletting, pickforks, burning torches, eye gouging; each side making a concerted effort to stamp out the rival 2D CAD users and program.

When the set up the first four 286 AT machines in our office, they hired computer guys to run them.
The computer guys did not know how to use a CAD program, and had never done manual drafting, so they were totally useless.
The engineers refused to work with the CAD guys, and so after about 4 months, they fired the CAD guys, and trained the engineers to do CAD on the computers.

Doing your 2D drafting on a computer in 1986 was like making some sort of scared pilgrimage to a holy place (the computer room).
You did not use CAD at your desk.

For several years, we would try to do an entire project in CAD, and get about half way through it, and then run out of time, print out all the drawings, and finish the project by drawing manually on vellum.
The early CAD days were about as much fun as plowing a frozen field with a wood plow.

VersaCad did not have XREF's, but in many ways was easier to use than the AutoCad of those days.
AutoCad was unstable for many years, and never really had a very advanced interface.
AutoCad had the lowly command line, and my 2004 version still uses the command line, which is basically the DOS method when we did not have mice.

We used a sneaker net, with 5.25" floppy drives.
One of the wordprocessing women was typing a spec too fast, and she accidentally typed "the files shall be exchanged via a floppy dick", and did not catch her error.
We never let her live that down.

Those were the days for sure, but not good days for CAD.
There was a civil war between the various CAD programs and users.

There was no network, and so people over-wrote each other's files.

The pen plotters were terrible.

Many of the engineers gave up trying to learn CAD in disgust, and went back to drawing everything on the drafting board.
Computers and programs were not so good back then. There were a few good programs.
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[johnmcc69]

C'mon. All you 3D CAD junkies. You all have so many opinions, but I'm seeing little examples of your work, besides Pat & Jason.

Would like to see some of the examples expressed in your posts.

 

[GreenTwin]

If I have to add a part to the assy., or modify the shape of a part, I have to (Ughhhh) export all the drawings all over again. This affects all the assembly, section, & exploded views & once again disconnects all my data & requires me to update all my drawings. Painfully.

I create the initial base sketches in Autocad and then import that sketch into Solidworks, but any subsequent sketch work is done in Solidworks.

I never export a sketch from Solidworks back to Autocad.
Once the Autocad sketch goes into Solidworks, generally I only need to do minor edits in Solidworks.

Occasionally if a sketch is really complex, and is having major problems, I will go back to the original sketch in Autocad, modify it, and then to a copy/past into Solidworks again, replacing the problematic sketch.

My approach for using AutoCad sketching and Solidworks is purely speed.
By using AutoCad for initial sketches, and then pasting those in Solidworks, I probably have an 80% time savings.
Despite any and all efforts on my behalf to be able to sketch in Solidworks as fast as I can in Autocad, the fact remains that sketching in AutoCad takes 10% of the time that sketching the same sketch in Solidworks takes me, for whatever reasons that I cannot overcome.

I use a relatively bare-bones approach to 3D modeling engines, and I realize that method would not work well for commercial projects.
Model engines are not commercial projects, and the spare time I have to do 3D modeling for engines is extremely limited.

I have to do what works for me, regardless of how bastard that may be, because what does not work for me..............does not work for me; its pretty simple logic.

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[GreenTwin]

@GreenTwin I wonder if you are aware of this SW functionality example. I started a very simple sketch within SW. It has some dimensions defined thus far, but still has some blue lines so not fully defined. As my picture notes convey, its very easy to see what's going on with active feedback. I just grab a line element. If it doesn't move, it means its constrained (dimensionally and/or by virtue of relationships). If it can move, it expands or contracts or changes in the orientation that is still free & floaty. So you say aha & define that dimension or relationship.

Now if you don't mind, can you try that in one of your imported sketches. Is this SW diagnostic feature essentially locked into whatever you imported?

I will have to play around with that.
I have literally ignored and sidestepped these features since 2012, and so I will have to get back into the learning curve again to even be able to remember how all that works, and to leverage the power of it.

No time right now to learn anything new, due to workload.

Perhaps one day I will go "full 3D" and quit using Autocad, but I am definitely not there yet, and not close to that either.

After all, if Jason can "go CNC", then who knows what I could potentially do.
I could go full "CND", "CNE" or even go all out "CNG", whatever it takes.

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[GreenTwin]

By importing bad geometry, you have no similar feedback inside the sketch if there is an issue until the feature blows up. This is just scratching the surface but hopefully helpful.

In the beginning, I did import some bad geometry, but that was before I had a good conceptual understanding of how a 3D program works.

There is no doubt I could leverage some of the features in Solidworks that I am not using.
Being able to link dimensions with formulas is a very powerful feature, but I have not had time to think through how to effectively use this feature, when to use it, or what part would benefit most from its use.

Learning 3D takes time, and I am not retired.
I work like 70 hours a week, almost every week.

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[johnmcc69]

I think you should try the sketching tool in SW. It's probably not as hard as you may think. Like I've mentioned, they're aren't too many things you can't create there.

I'm not dismissing 2D ACAD, it still has it's uses, & I can probably show you some "old dogs" some new tricks about using model space/paper space. That would be another thread....

 

[GreenTwin]

Bentwings said:
im kinda lost here . I’ve been through so many cad programs over the years I remember goingvto an auto cad seminar when it turned out it was noting but an electronic drafting board . I had already benn in solid modeling for a number of years . I even ran and serviced the mini computer and work stations . I could not believe the “ monkey business “ this was. Essentially you created a drawing with a stylus pen A week or so later the sales rep came to see what we thought of his system I gathered the other cad people to my cubicle then Since I had a paper copy of his drawing I did a watch this thing . I recreated it as a solid model then I said how big would you like to see the paper drawing , pick a scale factor I’ll put at least had a dozed views including s broken section up too then I had each of our crew add some features.

Now that you mention it, in the pre-mouse days, in my office, they used 10-button digitizer tablets, and the commands were on the tablet, along with programming of the 10 buttons.
We had to pry those digitizer tablets out of the CAD guy's hands; those guys were almost impossible to convert to the mouse only.
That was a huge prolonged pitched battle (digitizer vs mouse), also with much blood letting and eye gouging.

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[GreenTwin]

I think you should try the sketching tool in SW. It's probably not as hard as you may think. Like I've mentioned, they're aren't too many things you can't create there.

I'm not dismissing 2D ACAD, it still has it's uses, & I can probably show you some "old dogs" some new tricks about using model space/paper space. That would be another thread....

Its really just a matter of finding enough spare time to get proficient at sketching in Solidworks.
I just don't have any time right now.

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[petertha]

You are confusing dimensions created by pressing the "smart dimension button" with the dimensional value that shows up in the dialog box on the left of the screen when you draw a shape such as a circle. One is pushing a button to create two leaders, arrowheads, and a number, and the other is a value in the database that does not appear on the screen as a normal dimension.

I think I touched on this my other post but just to put pictures to words, here is a series of screen grabs that hopefully clarifies what you mentioned. The dimensional values in the properties box and the dimensional values of the classic arrowhead dimension (using smart button or whatever) are one & the same. If you adjust either one, the other will update automatically. The reason you see values in the properties box and not as dimensions is only because you didn't bother to use the dimension tool or subsequently deleted it from view. That is equivalent to being turned off or hidden. But hiding the dimension is not the same as deleting the numerical dimensional value. Its still there, in the database to use your words.

My screen grabs

1) from within SW, sketch a random line going off in space, click to begin, click to end. Note how SW is actually conveying the current length in the little box as it rubber bands? Now if I prefer, I can enter a keyboard value before terminating the line it will make it that exact length & auto-terminate. Anyway once its sketched, it is blue indicating 'not fully defined' (a SW term).

2) now look at properties box. The rough sketch reflects its current length & angle values however it was drawn, hence all decimal places. My point is the numerical values match identically to however the sketched line terminated. they are one & the same.

3) now I go back to sketch & define the length and angle to what I really want. The line segment now turns black confirming SW agrees its fully defined. It tells me that visually & numerically on one screen view

4) now look at the Properties box, it has reflected these changed value & once again they match

What you are doing is importing ACAD geometry that +/- matches step 3) but without the benefit of co-displayed dimensions when it would be advantageous & useful to see. You did 1&2 in ACAD which you are more proficient at, but dimensionally its the same data. Negating dimensions in SW sketch is not saving any computation time, or improving accuracy or any advantage I can think of. Its just how you prefer your current workflow which SW facilitates. IMO its equivalent to generating a Drawing of a part but neglecting to display critical dimensions. The actual dimensions are indeed numerically known within the model. But it's just not being conveyed at the appropriate stage where its most useful. In the case of a drawing, for the machinist. In the case of a sketch, for the designer. Even if you are the sole designer & CAD file never to be shared, maybe you will open that file & wonder - how did I cook up that sketch? what file version is it in? does that version match what's now in SW ? Did I tweak that dimension in ACAD or SW after the fact? etc. etc.

Sorry, you seem very disciplined in your approach but for me, all I see is a minefield of potential things to go wrong. But that's just my own personal opinion. Often I take screen grabs of different design mods or decision points or whatever & save them as jpegs or in a OneNote file for personal sanity. Even that pseudo documentation process is hard to connect the thought process a year later when it looks less familiar & especially if parts/assemblies start getting more complex.

 

[GreenTwin]

Sorry, you seem very disciplined in your approach but for me, all I see is a minefield of potential things to go wrong. But that's just my own personal opinion.

Sometimes things do go wrong, but generally it is due to using a very complex starting sketch, with perhaps a lot of splines in it, not due to a problem with sketching in AutoCad and importing into Solidworks.

The more complex the sketch, the higher the chances of something going wrong, or the higher the chance that the compound surfaces generated will not fillet correctly.

I will try and dig out some complex sketches.
I am sure someone well versed in the 2D aspects of a 3D program could work at a good speed.

This bottle engine frame was a bit odd to sketch and model, and I had to try several different things to find something that would work reasonably well.

You can see the beading at the top of the cutout is not working like it should.

 

[GreenTwin]

This Bernay is not very complex, but it was one of my dad's freelances, and I don't think it is a very accurate Bernay.

 

[GreenTwin]

This Cretors frame was a bit odd, but turned out pretty well.

These are the exact dimensions and style of a real Cretors No.06, and the intent is to cast parts that are fully interchangeable with the 1800's engines.

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[GreenTwin]

These Cretors No.02 flywheels were something I modeled early on, and they are flat spokes with a fillet.

A better and more accurate spoke is a lofted shape along a spline, which is a later technique I learned.

 

[GreenTwin]

The Dake did not have any big challenges from a 3D modeling standpoint, other than getting every part exactly like the original, which took a lot of time and study of photographs and prints.

 

[GreenTwin]

Getting a good taper on the flywheel (they had references in old pattern books about how much taper any given flywheel spoke should have) has always been tricky.

My first flywheels used flat spokes with fillets, and I progressed to lofted elipses, which are much more accurate as far as matching the old flywheel style.

Getting a fillet on the ends of the spokes to look right can be tricky.

 

[petertha]

Yup. I didn't even want to bring up surfacing, shelling, draft angles... that's where the rubber hits the road. The underlying sketches are very rarely 'standalone-able'. They are more likely to be based on more complex geometry of each subsequent feature step and/or have interconnected references many levels deep in the tree.

My induction tubes are generated from an assembly level. Its a simple 2D circle swept on a 3D curve. But, the curve is defined by multiple references - start & end planes, bend radius, included angle, tangent straight segment... This is an example where making a part in isolation & mating to assembly will not work.

 

[GreenTwin]

The Galloway frame and hopper were a bit tricky to draw accurate so that they matched an original Galloway exactly, and not a bolt-on cylinder.

 

[GreenTwin]

Yup. I didn't even want to bring up surfacing, shelling, draft angles... that's where the rubber hits the road. The underlying sketches are very rarely 'standalone-able'. They are more likely to be based on more complex geometry of each subsequent feature step and/or have interconnected references many levels deep in the tree.

My induction tubes are generated from an assembly level. Its a simple 2D circle swept on a 3D curve. But, the curve is defined by multiple references - start & end planes, bend radius, included angle, tangent straight segment... This is an example where making a part in isolation & mating to assembly will not work.

I have never successfully added to an assembly, but I have seen it done, as you have done.

That is a cool trick, and as you say, not something that could easily be done otherwise.
You could always draw two mock-up surfaces, sweep the curve, and then suppress the mock surfaces, if you really wanted a separate part file for the tube.

Nice engine.

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[GreenTwin]

No really challenges with the Robertson.

 

[GreenTwin]

The Speedy Twin has been somewhat challenging, just because it is a compact and relatively complex engine, especially the multitude of passages up in the top above the cylinders.

No one really complex 3D challenge, but a lot of little challenges.