CAD Strategy Concept

I believe this is the most important instructional video in this

course because it discusses the concept of the CAD strategy.

The CAD strategy

in my opinion

is the single greatest factor that will determine whether you're successful

at creating a CAD model that's good,

that's accurate,

and that is reusable

in a design setting.

What is a CAD strategy?

The CAD strategy is the simple set of CAD operations

we plan

to execute in a particular order

to create a complex shape.

What does a CAD strategy look like?

Well,

of course,

CAD strategies can take a variety of forms.

They can even exist simply in one's head,

but I think that they are most useful

when they're hand sketched

and with annotations

and some dimensions

that dictate

the operations

and their order

that will be taken when you get into the CAD system.

Now it's important to recognize that when we make these hand sketches,

I believe it's worth

3 to 5,

maybe 10 minutes for a complex part,

but not more than that.

You need just enough to get going

and to understand what's ahead of you

in the CAD modeling process

so you can start sequencing things

nicely.

The CAD strategy captures that.

And of all the hundreds of models that I have created,

I am confident

that in less than 10 minutes,

you can create an excellent CAD strategy.

Now I'm just gonna say a few more things here about the CAD strategies and their use.

I will just say that when I have developed trouble during my modeling process,

I usually find that I actually didn't make a CAD strategy.

I said to myself before I even got going on the part,

I think this part's easy enough.

I can just get into the CAD system and start working on it.

Well,

if you get into the CAD system

and just start working,

that's where a lot of

trouble

bubbles up from,

in my opinion,

in my own experience, and having watched hundreds of students

learn how to use CAD.

And so,

I forced myself to create a CAD strategy.

When I do,

it does not let me down.

When I don't make a CAD strategy,

I can sometimes succeed but almost always

run into some difficulties.

All right.

In order to create a CAD strategy and use it effectively,

you're going to have to understand a couple of really

important things that we're gonna cover in this video now.

Number one,

we're gonna talk about how

the CAD system works

in terms of taking geometry that you want to give it

and then

it producing 3D geometry.

We're going to talk just briefly about that.

Then, we're going to talk about what CAD operations are available to you.

And then,

we are going to talk about

five critical questions that you've got

to ask yourself while developing your strategy

that will help you to know

what

CAD operations you want to use

and in what order.

So, I'm going to jump right now into Onshape,

and we're going to start looking at the first part of this,

which is

to understand how the CAD system works.

So, we have here

a classic Lego roof tile

that I have modeled up just a few minutes ago,

and I want to

make a very important point about what's going on with this simple image.

The CAD system works in such a way that we start

with a 2D representation of something

that turns into a 3D

shape,

and then we do another 2D

input of information that we then create another 3D shape. We go back

and forth between 2D and 3D and 2D and 3D and 2D and 3D.

And I'm gonna show you how that works with this model here.

OK.

I'm just gonna take the

rollback bar and go right up here to right at

the beginning as if we're starting this model from scratch.

OK.

The first thing that we do in the CAD system is we create a 2D shape.

My 2D shape is this sketch that I drew here on the top plane.

Then, I use that sketch that was made in 2D and I create a

3D

prism out of it.

OK.

Then,

I go on to my next step,

which is I'm going to create another sketch.

And what sketch am I gonna create?

I'm gonna create this triangular sketch on the side of this rectangular prism.

Then, what am I gonna do?

I'm gonna use that sketch to create another 3D

operation, that is I'm gonna remove all of the material

behind that triangle.

Then, I'm going to do another 2D operation.

I'm going to put

a circle right where the Lego stud goes.

OK.

And then, I'm gonna use that 2D shape to create a 3D

object by extruding it upward.

Maybe you can see what's going on here.

We're going from a 2D representation of a shape to a 3D

representation, and then 2D to another 3D and 2D to 3D and 2D to 3D.

This is generally what happens

in the CAD system, and this is important to grasp right now

because when you develop your CAD strategies,

you've got to think about what are your 2D

operations you're gonna do and what are your 3D operations you're gonna do.

Now, of course, let's just see this Lego part all the way through.

We're gonna take that stud and mirror it across this right plane.

OK.

And then,

this is looking really great from this perspective

but does not look like a Lego brick

at the bottom.

So, we're going to do a shelling operation,

which will give us a constant wall thickness everywhere.

And then,

we got to get those undertubes in there,

and I'm gonna do a sketch,

a 2D sketch,

and then I'm gonna do a 3D operation

that gets me those parts.

So, this is item number one in understanding strategies is how the CAD system works.

The CAD system expects you to put in a 2D sketch,

which we do in the sketching environment.

And then use that sketch to create a 3D shape

using one of the other CAT operations such as an extrude, a loft,

a sweep or revolve,

or something like that.

All right.

It's

important to know

as you're developing your strategies that not only do the

set of operations matter,

but the sequence of operations matters.

So, for example,

let's roll this back to where we just have the shell.

We'll get rid of the undertubes for a minute.

I'll turn off the planes, so we don't have to look at those.

OK.

All right.

We can see that there are these two holes in here.

Where are those two holes?

Well,

those two holes

are,

let's just actually take a look.

OK.

Those two holes are what happened

when we had the stud that's right up here,

and then we looked

at making a constant wall thickness with the shell.

It gave us a constant wall thickness here.

It gave us a constant wall thickness up here and

wasn't gonna leave a large chunk of material right here.

It's gonna give us a constant wall thickness.

So, that's what we see

when

well

we

have shelled

after

the studs have been put on.

And what happens if we shell before the studs are put on?

Well,

let's just take the shell and move it up here

to wherever that is.

I think it is right around here.

Yep.

OK.

We see that those underholes

have gone away,

and we no longer have a constant wall thickness.

It's because I added a feature

after

the part had already become a constant wall thickness part.

OK.

Because when I've got done with my shell,

where am I?

I'm just right here

in the set of operations.

And so, the point here

is that

we

need to be quite thoughtful about the order

of the operations

that we choose to do.

OK.

Let's see if I fixed this model or if I've messed up this model.

OK.

I have now fixed it.

All right,

that was the first bit.

The first bit of getting a good strategy is

understanding what is going on in the CAD system.

The next thing we have to know in order to know which kinds of

steps

or

operations we'll use in our CAD strategy.

We have to understand what

CAD operations are available to us.

And I just want to point out right now that

if you are feeling like the CAD system is overwhelming,

you just actually need to know that there's only

a few operations that are even going to matter

in terms of getting your strategies together and making most actual CAD models.

OK.

And I have put a small sheet of paper that describes these

right here in this unshaped document, and I'm just going to open it up right now.

All right.

Now, I'm going to describe this as we go along,

but

I want you to know that there are four

basic operations that we're going to pay attention to.

It's the extrude,

the revolve,

the sweep,

and the loft.

We're going to use this in the

sense of creating material with these operations,

which is what we see right here.

And we're going to use those same operations

to remove material—extrude cut,

revolve cut,

sweep cut,

and loft cut.

Then, we're going to talk just a little bit about two edge treatments,

and then we're gonna talk about one special operation

that's over here.

Now,

in order to understand our discussion today

on this,

it's really important that you understand

the concept of the

cross-section.

Now, cross-sections can be really easy for some people

to understand and harder for some other people to understand.

So, we're going to take just a minute

to describe what the cross-section is.

What a cross-section represents is that if I cut the part,

as we have,

which as we can do in the CAD system,

I can cut it anywhere I want in the part and see the cross-section.

The cross-section that I see is the cross-hatched area

that's right here.

That cross-section

can

be

constant,

such as what we see right here,

meaning like the cross-section is not changing in this area,

or the cross-section can be changing as we're seeing in this area.

Or we might be in a constant section again,

or we might be in a varying area,

or we might be down here in a spot where it's actually quite changing as time goes on.

So,

in a particular direction,

such as the direction I'm pulling right now,

we can think about the cross-section.

Now,

it turns out,

of course,

that the cross-section exists

in

all kinds of areas.

OK.

I could look at this one for a second.

OK.

Here's a different cross-section.

OK.

And this cross-section

is constantly changing.

OK.

Constantly changing there looks like I've got a bunch of

planes here

that's kind of crazy.

OK.

So, I'm gonna select this one,

and then I'm just gonna say,

take a look at this cross-section.

This is a cross-section,

of course,

in a different direction.

All right.

The cross-section,

it's important concept to understand.

And there's yet one more cross-section that we want to look at

for just a moment,

and that is

what happens if we are going to have a part that is axisymmetric.

OK.

Axisymmetric means

that,

okay,

let's turn these off for just a second.

OK.

And let me get rid of these

sketches.

OK.

All right.

What is going on with axisymmetric?

Let me get my cross-section up here again.

OK.

And

this particular part

is made by a revolve and what a revolve is doing

is it's taking a cross-section like the one we see here

and then it's pushing it around

a certain number of degrees.

And so, that means that this cross-section is the same

at every one of the cross-sections if

we're imagining

they're the same around this axis where my mouse is right here.

That means they're axisymmetric.

All right.

So

that is an important part.

I'm just gonna cancel out of this one for a second.

This is an important part of understanding

the table that we have in here is we have to have an understanding of what's going on

with the cross-section.

Here we have

in

this part of the tables, we have some stuff about cross-sections.

The next thing we need to understand is we have to understand extrude path.

OK.

And over here, I have a simple example of what is meant by extrude path.

For

this,

operation,

which is an extrude operation where we're gonna add material,

we simply take a cross-section like this red one that's there

and then we pull it or push it or

extrude it in a certain direction.

The direction that we extruded in is called the extrude path.

OK.

The extrude path.

If you understand those two definitions,

you will understand everything on this sheet of paper.

OK.

So,

what's

going on now is I've got a simple example of each of these,

and we're going to talk about them because

these are the CAD operations that are available to you.

And because they're available to you,

they should be part,

well they have to be part of your CAD strategy,

which of course is your simple set of CAD operations

that you plan to execute in a particular order

to create a complex shape.

So,

the first part of this table is all about adding material.

We're gonna look at that first because these,

this is strategy support right here.

This is for adding material.

So, I'm gonna go into this folder right here that's called Add Material.

I'm gonna look at extrude

and what I want to do is I'm looking back at that

same one that we had as an example just a second ago.

This is the base structure means we're going to add an extrude to this structure.

And what are we going to do?

We're going to add this piece

that's right there.

OK.

And how is this done?

Let me just get out of this for a second.

We have this profile

that's right there,

and then it's going to be extruded in this direction.

So, a

constant

cross-section

extruded in a particular direction.

So, what does that mean?

That means that this cross-section,

that rectangular cross-section that's there,

is the same everywhere along the extrude path.

No matter where I cut it in the extrude path,

I'm gonna see the exact same cross-section.

Every time I have a CAD feature

that wants to have

a

constant cross-section through a straight line,

I'm going to do an extrude.

So, let's just look at that for a second.

Every time I want to have a constant cross-section

that goes through a straight line,

I will do the CAD operation called extrude.

You really have no other option.

Now we're going to look at the next one,

which is that any time we want to have a constant cross-section

extruded around an axis in an axisymmetric kind of way,

we will use the revolve command.

So, we're gonna go over here to add material; we're gonna go take a look at revolve.

And when we look at revolve,

we're gonna see that I have a revolve here

that has a sketch

in orange

and the axis of revolution is the dashed line.

Now what's going on in this particular revolve is that

we chose to revolve only 270 degrees,

and that has created this

solid.

So, back to our sort of table on what's going on here.

Any time we wanted to

add material

where we have a constant cross-section around an axis

and I'm going to revolve it around that axis

or it's axisymmetric around that axis,

I will create that feature

by using the revolve

command

in

any

CAD system actually. In this case, Onshape,

but that's the same for all the CAD systems.

Alright,

the next one we're gonna look at is called a sweep. And what's going on with the sweep?

We're gonna use it to add material.

We want to have a constant cross-section

through a non-straight line.

So, this one's actually pretty

similar to the extrude,

a constant cross-section.

OK.

Extrude us through a straight line,

sweep us through a non-straight line.

You could actually do a sweep through a straight line, but

the strength of it is to do it on a non-straight line.

OK.

So, we're gonna go over here to add material. We're gonna take a look at sweep.

This is the part.

And what have we got going on here?

We have

this cross-section,

okay,

which is then going to be swept through that

line.

Now it's important to realize what's going on here because

let me just get into a cross-sectioning

tool.

Here, we have what looks like the same cross-section,

but as we go throughout this,

we see that it's not actually looking like the same cross-section.

Well,

what is meant by this when we say that

a

constant cross-section

swept through or extruded through a non-straight line such as this line.

OK.

That's actually not what I wanted to do.

When

we say we have this cross-section going through a non-straight line,

as the

section

follows

the

profile,

you know,

the

sweep

guide

or what do we call this like the non-straight line,

right?

It will stay normal to that, and when it is normal as it goes through that path,

it will be the same cross-section everywhere.

As

this profile bends and it turns up here

and then it bends down and turns over here,

this cross-section will always be the same and that is the definition of the sweep.

The sweep being that we want to have

a

constant cross-section going through a non-straight line.

All right.

The next one we're going to look at is called the loft.

What's happening with a loft, in this case, we're gonna add material.

We're gonna have a non-constant cross-section, which can

go through a straight or a non-straight line.

All right.

Coming into our add material folder, looking at the loft,

here we have

a cross-section here,

and then we have another cross-section here,

two different cross-sections.

And as I go from one cross-section to the next cross-section,

I have a varying

I

never have the same cross-section anywhere. It changes. It's non-constant

cross-section.

All right.

How

is this one done?

Well,

we do have

that cross-section and this cross-section and then we have some guide curves

that are telling how to get from this section

over to this section.

In this case,

we have another guide curve here up at the top too.

All right.

Now,

that's what it looks like for a non-straight loft.

I'm gonna take all this and I'm going

to...

What am I gonna do?

I'm gonna hide it,

and I'm gonna come over here and I'm going to unsuppress this one.

So, we can see what a loft looks like

when

it's through a straight line.

OK.

So, what is this?

We're gonna go from this side

over to this side,

oops, over to this side,

and

the extrude path is

this one.

It's just a straight line.

And what do we see?

Well,

we see an object that has a nonconstant cross-section.

In fact,

let's check our non-constant cross-section by just

hitting shift X to get a cross-section.

And we can see that that cross-section is shrinking

as it goes down.

OK.

It's actually hard to see,

but that's what's going on.

All right.

Well,

that's all of the operations

that are needed for adding material.

So just remember,

anytime you have a constant cross-section that is extruded through a

straight line or is expected to pass through a straight line,

you'll use an extrude.

Any time you have a constant cross-section

around an axis and it's axisymmetric,

then you will use a revolve to create that.

Any time you want a constant cross-section to go through a non-straight line,

we will use a sweep.

And anytime we have a non-constant cross-section

passing through a straight or non straight line,

we will use

a

loft.

And when I said straight or not straight line, I

meant a straight path or a non-straight path.

All right.

Now all of those same exact operations,

the extrude,

the revolve,

the sweep,

the loft

work when we remove material as well,

which is this section here which is

to support the strategy to remove material or subtract material.

In this case, we're gonna go look at extrude cut,

revolve cut,

sweep cut,

and loft cut.

All right,

coming into here.

OK.

Here, we have an extrude cut.

Where do we have the extrude cut?

It's this circle that's right here.

This

is a constant cross-section

that has been extruded

through a straight line, and it's that axis that is the straight line.

So, the exact same concept as an extrude except we're

removing material, which is that we have a constant cross-section

passing through a straight line or the extrude path is a straight line.

Let's look now at the revolve cut.

What's going on with the revolve cut?

Well,

we have a

section

sketch, which is shown right there.

OK.

And we're going to take this sketch,

and we're going to revolve it around an axis, and the axis we're revolving it around

in this image is this one.

OK.

And what does that produce?

Well,

it produces

an axisymmetric

cross-section that has been swept through or swept

is not the right word it's been revolved through

this.

And actually, I'll show you something here that

will make this slightly easier to see.

Let's go into our revolve.

Let's edit it from going from a full revolve to a

one directional thing that's say 30 degrees like we're seeing right here.

OK.

We can see now what's going on with this,

which is that this cross-section is being revolved around this axis

and the materials being removed.

I wonder if I can do this in real time.

I cannot.

OK.

We could switch that to 60 and then we could see what that looks like

just like that.

OK.

Let's go fix this one.

We'll switch this back to full,

and we'll accept that.

And that's what a revolve cut

looks like revolve cut.

All right.

What does a sweep cut look like?

Well,

in the sweep cut, we have the same exact thing.

OK.

We're gonna have a

constant

cross-section,

which is represented by this little channel down here,

and it is passing

through a non-straight line. And here is our

non-straight line that is passing through.

OK.

All right.

That's what a sweep cut is.

OK.

And then we have the loft cut.

What's going on with the loft cut?

Well,

the sloft cut can be one of the more complicated shapes,

obviously.

We're going from

one cross-section,

which is a half circle up here,

and we're ultimately going to get down to this other cross-section over here,

which is less than a half circle,

and it's going to go through a straight or not straight path.

In this case, it goes through a non-straight path,

and it's creating this.

That is a loft cut because we've used the loft to remove

material from this base structure

which is right here,

right?

All right.

Well,

I'm gonna go back over here and take a look at this image.

Now that we basically understand what's going on with this image,

we have all the additional, the ways to add material extrude revolve,

sweep, and loft.

We have all the ways to remove material—extrude, revolve,

sweep, and loft.

And let's just go here into this model for a second,

and let me just point something out that's really important.

Right here are those four operations—extrude,

revolve,

sweep,

and loft.

Now here we have thicken.

Thicken is when we get into surfaces,

but for our solids,

those are the only four operations

that

are

that all CAD models are made up of.

Then, there's a bunch of other stuff like mirror and pattern

and put on a thread and other stuff like that,

but these are the core operations.

If you know the core operations, now you know what's available to you

when you're creating your CAD

strategy. You're either going to have an extrude a sweep or revolve or a loft

in order to do those 3D

operations.

OK.

We have just finished the second piece of this.

The first piece was to

understand how the CAD system works in terms of 2D,

3D,

2D,

3D.

Now our second part was to understand what CAD operations are available to you,

and we just talked about them.

But we have to add

just a few more to them really fast.

And I'm going to just show you how that works right now,

which is going back over to this.

We have two edge treatments,

and then we have one special operation. And frankly,

there are not a lot of special operations,

but there's

just one, and it's this one. It's called the shell.

OK.

We're gonna talk about champfers and filets, and we're gonna talk about

shells.

So, I'm gonna come in here to these other operations.

We're gonna take a look at this crazy model right here.

I've made this crazy model so that I could show you

what half of it looks like when champfers are on.

OK.

These are what champfers look like.

OK.

Champfers can be used to remove material

like chopping off this corner that's right here,

or it can be used to add material,

which has happened in this case.

How does that work?

Let's go take a look at that one for a second.

The edges that are on the inside,

inside edges,

if you champf for them,

they ultimately add material.

OK.

So, that's what that is.

Corners that are on outside corners, if you champf for them,

they remove material,

such as this.

OK.

We can also see a small champfer right up in this area

that removed material. Then, we can also see champfer on a curved surface,

such as this one that's right up there.

All right.

How does this relate

to

fillets?

Well,

first of all,

while I'm turning the fillets on,

I'm just going to point out that

a champfer is a beveled edge.

You're gonna put a

flat edge on something like this.

A fillet,

however,

puts a curved edge on something.

In this case, we have knocked off this edge

with a fillet.

We have also added material here with a fillet,

which is exactly the same kind of operation

we did

with

the champfer, except we've grabbed the other side of this

and done a fillet, and so it's added material

into there.

And

we have got a fillet right up in this area and then a fillet on a curved surface

as well.

OK.

So those are the edge treatments.

There's only two edge treatments.

It's a champfer and a fillet.

And if you want it to be faceted,

use a champfer.

If you want it to be curved,

you use a fillet.

OK.

All right.

Now one other operation that we want to look at

which is a special operation is called the shell function.

What's going on with the shell function?

Let's actually roll this up before we have the shell.

Let's take a look at our part.

This is a solid part. If we do a cross-section through here,

okay,

like this,

we will see that it's solid.

And when we do the shelling operation,

what happens

is that it forces

a constant wall thickness everywhere.

Now this is really important because now I

can see my constant wall thickness in here.

And this is a great way

to produce parts that are cast or

molded or other stuff like this. We often need to have a constant

wall thickness, and there is a full CAD operation in all CAD systems

that are designed to help us do that really easily, and it's called the shell.

OK.

The shell is right here.

And you can see that we have

the extrure,

the revolve,

the sweep,

the loft,

some stuff with surfaces.

We have our fillets;

we have our champfers.

We have draft which we don't do in this course.

OK.

This is important, but not

for this course that we're in now.

OK.

We have this thing called ribs and then we have shell.

All right.

And then we have shell.

So, these are

the basic operations.

The one we're missing here—hole and thread.

We're going to get to those

a little bit later,

but these

ones that we see right here,

ribs,

shells,

holes,

and threads,

and actually even the draft,

these are just

as far as the CAD system is

concerned

basic operations

put into a format that makes it easy

for a designer to do something.

So, we could create this

shell,

for example,

by just using extrudes

by adding material and extrudes by removing material.

And what happens with the shell is that it just does that

same exact thing

except it combines them

into one operation that's just a little bit easier for

a designer to use. But nevertheless,

these are the basic operations

that are right here. And we now know

everything

about what they do for us

and when we need to use them.

All right.

So that was our second bit of this important part of this

talk about strategy.

The third thing that we want to do now

is we want to look at

five essential questions

that we would use to determine

what our strategies

should be about.

OK.

Well,

this is important because when we're creating our sequence of

steps or operations,

CAD operations that we're gonna do in the CAD system,

we need to think about a couple of things.

The first thing we want to do is we want to ask ourselves,

what features of our complex shape

do we think we want to create by adding material?

What?

And then we want to ask ourselves what features of our

complex shape do we want to create by subtracting material.

These might sound like simple questions, and they are simple questions,

but they are the basis

of the strategy.

You have to be thinking about,

well,

how am I going to get that feature in there?

Am I going to

add material to create it, or am I going to subtract material to create it?

All right.

The next thing we want to ask ourselves,

the third critical question here is where do we need to

place the origin and the main planes or the datums,

you know,

like the front plane,

the top plane,

the right plane?

Is there a good place to place them in our part?

And

we want to ask ourselves the fourth question,

which is,

is there any symmetry or is there any patterns in our part?

This might help us to know where the origins should go or where a plane should go,

like on the Lego brick where I wanted to mirror the stud to the other side,

it was helpful

that I put a plane right there at the very beginning that could be mirrored across.

And then, the last thing that we want to ask ourselves relative to creating the

CAD

strategy

is what do I think I might want to change later

in my model?

And do I need to do anything in my model development to make it changeable

later?

Now this is really important, and it's a bit forward thinking, and

I just want to talk about it for just a second.

When you're in a course like this,

the very first things that you're asked to do is to

take an engineering drawing and read it and then produce the part,

like reproduce it.

That's a bit unusual.

It's good for education,

but it's unusual.

If we had the engineering drawing,

we wouldn't need a CAD model

because we would have created the engineering drawing from the CAD model.

And so, usually, what we're doing is we're creating our CAD models from

a hand sketch or a representation of what we want and we're not entirely sure

all the features that we're going to want to have

and what shapes and sizes those features are going to be.

And so, if you are working on a new product development activity and you're

starting to create your CAD models and you're really unsure about some things about

the length of things or the number of items in a pattern or whatever,

knowing about that early

while you're developing your CAD strategy

helps you to build features into your CAD model

that allow for adaptability

and allow for flexibility

in

the model.

OK.

At this point, we have gone over

the key things that are needed for you to be able to develop your CAD

strategies.

Now the last thing that I want to say about this

is that if you make a CAD strategy,

I believe you're already on track for being

a lot more successful in your CAD modeling,

but if you make a CAD strategy,

you need to make sure you use it.

And what do I mean by that?

It means that

you create your CAD strategy first before you get into the CAD system,

then you get into the CAD system and you do step one of your CAD strategy.

Then, you finish step one and you go back to

step 2 of your strategy and you do it.

And then, you go back to step 3 of your strategy, and you go step by step.

This is one way to take a complex modeling activity

and break it up into simple pieces.

Now the reality is

it's quite likely that you'll have to change some bits of your strategy,

and that's OK.

The whole point of the strategy was to think about

the modeling that needs to be done before you do it

and then

start doing the modeling.

You might have to make some adjustments

and that's perfectly OK.

That's perfectly OK.

But I can tell you

as a summary kind of comment.

If you don't have a strategy and you plan to

just get into the CAD system and start working,

you will wander.

And as you wander, you will waste time.

And as you waste time,

you will not have as much time to do the stuff that really matters

in the product development work, the creative work,

the

detailed work,

the engineering analysis work.

And so,

I recommend

that you always have a CAD strategy.

That CAD strategy should be written

by hand with some sketches

and some key dimensions.

Those sketches should not take more than 10 minutes,

and those

well

strategies that you've sketched out should

capture

your basic plan for simple CAD operations

that you'll do in a particular order

to create the complex shape.

Take it from someone who's been doing this for

a long time and has seen people struggle

and

succeed in their CAD modeling,

the strategy makes a huge difference.