Member postings for PatJ

I have written my own tutorials with the intent to help others perhaps avoid some of the grief I experienced when learning 3D modeling.

Writing your own tutorial also forces you to reach a deep understanding of what a 3D program is doing.

If you can put it into words, you are generally forced to much better understand it yourself.

.

3D modeling is parametric-style design.

I recall asking the question "What the heck is parametric design?".

The beauty of parametric design is that a change to any 3D model automatically propogates to its related drawing(s), and thus every view (such as left, right, top, bottom, side, and isometric) in a 2D drawing automatically changes when the associated model changes in dimension.

The power of this one feature cannot be overstated.

It would be the equivalent of changing a front view in 2D CAD, and having the right, top, side, bottom, and isometric views automatically change in a corresponding fashion.

The individual 3D models that you create are the "base" of the design.

Changes to any model not only automatically reflect in the 2D drawings, but also reflect in related assemblies, bill of material, motion study, expoloded view, etc.

Parametric means that everything is linked together in a web of interrelationships.

.

Edited By PatJ on 11/05/2022 02:23:49

I created 2D drawings daily for 18 years before I decided to try and learn 3D modeling.

I think "3D modeling" is a more accurate term, in lieu of "3D drafting" or similar terms.

You are no longer drafting per se, but rather created these solid models.

I have to agree that a long-term knowledge of 2D CAD is a detriment to learning 3D modeling; it was for me at least.

I had to create the graphical maps of information flow, which I posted in my other post, to clarify the differences in information flow in 2D CAD and 3D modeling (I will copy them below).

In 2D CAD, you created drawings that are isolated views.

In 3D modeling, you create individual models, and everything else emenates from those models, such as assemblies, 2D drawings, bill of material, motion studies, exploded views, etc.

I understand computer programming, and so I was simultaneously trying to figure out what the 3D program was doing from a computer program standpoint, and what equations it was using.

I found a good Solidworks tutorial book, but as mentioned by others, a tutorial video or book can be of limited usefulness when beginning to learn 3D.

The book I had stepped you through one feature at a time, and many of the features where ones that I would never use. The examples tended to be simplistic, and they did not address my specific need, which was how to model antique steam engines.

There was no guidance about how to combine the most useful and effective features together in order to efficiently make a 3D model.

When drawing in 2D, either on paper or on the computer screen, you basically lower the pencil, drag the pencil to create a line, and then raise the pencil. The end result is a 2D drawing.

My greatest difficulty is obtaining a broad overview of exactly what the 3D program was doing, and more importantly, understanding what it was that I was trying to make the program do, so that untimately I could produce a 2D drawing.

Understanding of the 3D modeling process gradually crystalized in my head over about a 1 year period, and once I understood the fundamentals of how a 3D program operates, and the various features they offer, then I could begin to figure out how to start creating steam engine models.

My first 3D models were absolute junk, but with each model there was experience gained, and I would learn a few more tricks and features.

It took me a solid year to learn 3D modeling as it applied to steam engines.

The green twin oscillator engine that I made originally started as a test to see if I really knew how to use 3D modeling. Much to my surprise, I was able to finally make quality 3D models for the green twin, and assemble them into an engine that would function virtually.

It was at that point that I said "I finally get it".

Not that I will every know every aspect of 3D modeling, but I can hold my own.

It was a triumphant point to reach, because my frustration level with trying to learn 3D was off the charts.

One tends to think that if you have mastered a 2D CAD program and used it for 18 years on a daily basis, then learning 3D modleing should be a shoe-in.  Not so !!!

I basically had too much money invested in a 3D program to let it go to waste.

It was a matter of learning Solidworks, or die trying.

Edited By PatJ on 11/05/2022 02:13:31

Someone above mentioned how intolerant 3D programs are to the slightest imperfection in a 2D sketch.

This use to stump me in the beginning, and I forgot how big a problem it use to be for me.

If you are not snapping exactly to the endpoints of lines and such, then you can have tiny imperceptible gaps that can be difficult to track down and eliminate.

One way to avoid the gap problem is to over-draw every line, ie: draw the lines longer than they need to be, and then use the trim command to cut them off, thus ensuring none of the dreaded gaps.

Sometimes the trim command itself creates a problem, such as at the intersection of two curved lines.  The trim command can produce a small section of arc on top of another line; and this stops a 3D program in its tracks.

Solidworks attempts to show you where the problems are in a sketch, but that feature is pretty ineffectual.

I draw 2D sketches that are intended for 3D very carefully these days.

Even then I sometimes have sketch problems.

One method for determining where sketch problems are is to draw a straight line across half the sketch, and trim it off.  If the problem vanishes, then it is on the side of the sketch that was trimmed off.

You can narrow down a problem area somewhat quickly using this method.

Another method to salvage a sketch is to go back and extend all the lines over each other, and then trim them all off again.

This usually clears up the problem.

A 3D program treats a sketch as a boundary, or a fence.

If there is a gap in the fence somewhere (no matter how small), or two lines where there should only be one, or one line on top of another, or a line projecting out by itself beyond the fenced boundary, then the program cannot make the calculation required to create a 3D solid.

Another way to visualize it is to think of a piece of string that has the ends fused together, so you have a continuous loop.  You can place this loop of string on a drawing board, and move it into an number of shapes (no overlapping shapes).  As long as the string is not broken, and does not overlap itself, the program will work.

A sketch must be a complete, clean, non-overlapping, continuous boundary.

.

Edit:

Another trick to diagnosing sketch problems is to temporarily cock the 2D sketch into an isometric position.

This is very helpful in exposing stray unintentional lines that are stopping the program.

I will attach a couple of examples, where I added a stray line segment up above my sketch, and another example where my vertical line extends beyond the circle.

It is much easier to see these problems with the view cocked over into isometric.

Edited By PatJ on 10/05/2022 00:54:55

Another neat thing that someone told be about (I forget who) is that 3D models can be downloaded for many parts and fasteners from McMaster Carr, such as these helical gears.

I can't necessarily edit these models, but I can import them and use them "as-is".

It should be noted that I am not a spring chicken, I am very much old-school in most ways, I don't like computers or smart phones, I like cars that don't have any electronics in them, I have been using a stick welder for 59 years and I refuse to get one of those new fangled MIG or TIGG welders, I like to draw using either pencil, or Indian ink on vellum, etc.

Learning new computer programs was not easy for me.

So i guess it boils to to the fact that I am proof that you can indeed "Teach an old dog new tricks".

.

And perhaps the feature that really makes 3D modeling worth the time and effort to learn is the ability to 3D print patterns on a 3D printer.

This feature is worth its weight in gold and time (if your 3D printer works easily and consistently).

The patterns that are 3D printed are highly accurate, and you retain all of the fine details of a part.

A 3D printer will generally operate unattended (not always), and so most of the time that would have been spent manually making patterns is saved.

3D modeling / 3D printing is a 21st Century method of design and pattern making, in my opinion, and an extraordinarily powerful design tool.

Edited By PatJ on 06/05/2022 21:49:02

An example of an exploded view of a model.

With 3D modeling, the 2D drawings are automatically created (actually I guess manually created using drag and drop) from each 3D part.

Any change to the 3D part automatically changes/updates the 2D drawing.

Other benefits of making an individual 3D model for each part are that you can create exploded views, bill of materials, assemblies of complete engines, and use motion studies to verify conflicts as the engine is running virtually.

I have never gotten the bill of material to work very well, but that is a minor thing to me.

Edited By PatJ on 06/05/2022 21:30:32

I made up a few sketches to be able to visualize the differences between what I was doing with 2D CAD drafting, and what I was trying to do with 3D modeling.

This is the sketch for 2D CAD or manual drafting.

The process is to look at an object (engine), and then draw one part at a time in 2D.

If I change any 2D sketch, the part will not longer fit with the mating/adjacent part, unless I change the adjacent part.

I often would make a change to a 2D part, and then fail to get every view correctly updated, and fail to get the mating parts and views also changed correctly.

All of the 2D drawings are derived from the engine parts, and they are not linked in any way, and so are totally independent.

I use colors much as they do in the pattern making world, but in my case it is more for emphasis and clarity.

I often use a light red color for surfaces such as drilled holes and bores that have to be machined.

I use pastels (correct term?) instead of the hard colors, and that seems to make a model more pleasing visually.

.

I am afraid I am guilty of just that sort of thing.

I am stubborn like a mule (according to my wife), and reluctant to change paths.

So for me, that would be the pot calling the kettle black, but I understand your point.

Edit:

My wife tells me that when I point a finger at someone else, there are three fingers pointing back at me, LOL.

.

Edited By PatJ on 06/05/2022 21:16:13

Another feature of 3D modeling that I find extemely useful is the ability to change surfaces to translucent, so you can see through them, and see what is happening inside of a model, and verify that things are as you expect them to be.

Here is an example.

I should mention what the benefits of 3D modeling are, and why it can be worth the trouble to learn 3D modeling, and use it instead of 2D CAD or manual drafting.

There are those who will be better served by using either manual drafting or 2D CAD, but for those who have the time, take the deep dive into the world of 3D modeling.

As with building model engines, 3D modeling can be addictive, and one seems to have to want to build those ever more challenging models/engines.

Some of the benefits of 3D modeling are:

1. You can create an assembly, and assemble the parts together, and verify if the parts actually fit, verify that things such as the holes in the cylinder head and the studs on the cylinder actually align, etc.

2. When you create an assembly, you run a motion study, and actually run your engine virtually (not all programs have this option).

If the parts do not fit, the engine will not run.

It is best to test each part for rotation as they are added, in case there is a misalignment.

Otherwise if you assemble all the parts before attempting a motion study, and you have a problem, you will not know which part is causing the problem.

3. Once you have created a 3D model, you can derive the 2D drawing from that model by creating a drawing file, and dragging and dropping the model onto a virtual sheet of paper.

You can drag the model left, right, up, down, and at angles, to automatically create, front, top, side, bottom, isometric, etc. views.

The views can be line drawings, or solids.

You can dimension the views, and if you change your models, the dimensions automatically update to reflect the new dimensions of the part.

Edited By PatJ on 06/05/2022 21:05:16

Everyone seems to eventually settle in on their favorite methods/techniques as they learn 3D modeling.

My techniques generally get refined with each model I create, as I discover better/more efficient methods.

The trick is to remember what you did, and how you did it, and thus the reason I use the paper trail for most of my models these days, since my memory is not very good.

There are many many ways to model any given part.

The only way to learn 3D modeling is to use the program, start with very simple models, learn one step at a time, and then keep using the program.

If you get frustrated with the program, put it away and try again another day.

This is how I learned machining.

I would chuck up a piece of metal, machine on it for an hour, ruin the piece, curse profusely, swear that I would never machine again, leave the shop, come back the next day, do the same thing, and by day 4 or 5, I would finally master machining that part.

Persistence is the key.

Few if any people learn machining or 3D modeling overnight.

.

Edited By PatJ on 06/05/2022 20:43:48

I showed my brother one of my 3D models, and he said "That looks very complicated".

I told him that despite the multitude of menus and toolbar buttons, in the end, 95% of the time, you use a few fundamental commands, such as draw a sketch, extruding, cutting or rotatw that sketch, and then repeat.

Once I learned 3D modeling, I was shocked at just how few commands I generally used to create models.

.

Edited By PatJ on 06/05/2022 20:35:20

One technique I have learned, which is very useful for complex parts, is to take a screen capture after each step, and paste that image into a photoshop program.

This leaves a quick visual paper trail, and should things go wrong, you can glance at your method, and generally figure out a new approach (if needed) quickly.

This paper trail is also very useful if you put a model away for a year or so, and then come back and start working on it again. I can quickly refresh on the approach that I took on any given part.

Here is a paper trail on a part that I modeled (a bearing support block).

Complex models may be intimidating at first glance, but the trick is to break their creation down into one simple step at a time.

Like climbing Everest; you don't jump to the top in one big leap, but rather take one small step at a time, and rest often for recovery.

Edited By PatJ on 06/05/2022 20:42:30

How to recover if you model expolodes;

1. Hit the "Edit-Undo" button (on my program, it is in the pulldown menu) repeatedly until you undo the problem.

2. In the beginning of my learning 3D, I would use a "Save-As" after every step, and if my model crashed, I could open the last good file.

These days, I never use the Save-As, and I only have one file for each part.

There are parts that are complicated enough that sometimes I cannot forsee which exact method I should use.

3D models are often created using the rotated sketch, additive method, and subtractive method.

On rare occasions I have to start a model over again, and map out a new strategy, but for me, starting over again on a model is very rare.

.

A third method is a subtractive method, and it is exactly like machining (the first method was an additive method).

We can create a larger diameter shaft, and then cut off (cutting from the center outwards) the material we don't want.

We result looks the same as the first method, but the difference is that when we change the length of this model, the flanges do not follow, and so we get what I call the dreaded "model explosion", where things stop working correctly.

One wants to avoid model explosion at all cost.

There is nothing worse than spending hours on a 3D model, only to have it all crash.

For round objects, the second method is to draw the shaft and flanges in section, and rotate that section around a central axis.