Extracting Critical Information from Drawings

Reading an engineering drawing is hard.

It's a foreign language and it takes practice and it takes skill

to know how to read those engineering drawings.

In this particular course,

I know you've been given some complex drawing sets that you need to try to digest.

It can be frustrating and it is definitely difficult.

In this particular video,

I'm gonna take you straight into my iPad and together

we're gonna look around at the engineering drawing for the NES

front cover for the Nintendo game controller for the NES system.

And what I'm going to do is talk through

how to extract essential information

from

the engineering drawing set.

All right,

so just pulling a chair up over here,

looking at the engineering drawing now.

Any time you have an engineering drawing,

you've got to spend time actually reading the engineering drawing

and so what I've what I'm doing right now,

I'm taking a look at a couple of things,

maybe I'll highlight where I'm sort of looking.

First thing I'm doing is I've come down here to

see how many pages or sheets are in this drawing set

that's alerting me to

the extent of the information that I need to be looking for

and through.

I'm also taking a look at what's going on up here with the revision block.

I'm seeing that there was a corrected dimension on a rim groove.

I like to just know what rev I'm looking at and why I'm looking at it.

I

like to start by just sort of glancing through each of the sheets

and understanding what I might be seeing on each of the pages.

In this case,

I

am seeing the front face and I'm seeing the front face again

with a bunch of dimensions here for the whole cutouts,

and then there seems to be this little rim

that goes around this stuff right here,

these seem to be defined in this view.

Right here,

seeing another cross-section and another note.

OK,

on this one, I'm seeing all of the underside

objects

as well as having an ISO view here which is helpful,

so don't have to go all the way back to sheet 1.

I can see that this page is going to be

helping me understand how to create these thin-walled

features that are sort of in these areas.

OK,

and then I see there's at least 3 cross-sections here,

just trying to get a sense for what's in the drawing.

And then here all these screw bosses,

this is a screw boss right here by the way,

all these screw bosses are defined, their location,

their heights,

etc.

And then in the last page of the drawing,

we have this whole,

this whole situation that's going on in detail

'J'

is being defined out

on this sheet.

That's where the cable comes out of the controller.

And so, I've spent about a minute

just glancing through these five sheets.

I have a sense for what's in here.

I haven't absorbed any

deep information yet,

but I have

checked to just sort of see what is there,

OK?

I've also spent a little bit of time glancing at the title block,

particularly in this area,

to understand a couple of things.

This model needs to be created in millimeter units.

The model material

needs to be ABS,

and then there is a texture on it,

MT11010,

and there is a color specification that's given.

So, there's a lot of stuff that's been given right there that's

going to be essential for me as I create this model,

especially as I begin the modeling process,

I've got to absolutely make sure that my units are right,

that can cause a bit of trouble if I'm starting in inches.

And then I need to switch this to millimeters.

The other thing I'm noticing here that's quite helpful for me

is this data right here that shows what the mass

of this finished top cover is.

That's going to be helpful for me as I

analyze my model and go along,

during

the modeling process,

that's going to be helpful

to me.

OK,

so that's the first part of just sort of absorbing

an engineering drawing set is just to

give it a once over,

then we need to start thinking about how to extract out

the essential information that's in this drawing.

Now,

a couple of tips.

Item number 1

is that engineering drawings are often

created in a sort of hierarchical way,

meaning that the top level information is on page 1

and the more detailed information is later

in the process.

So, if you're getting started with your model,

the first CAD modeling steps are likely going to be coming from

the details found in the first couple of pages of the drawing

versus the latter

pages

or sheets in the drawing.

So, for example,

if I was going to start the process of making this model,

I've got to ask myself some key things like

what is the overall width and what is the overall height,

and what is the overall thickness

of this basic prism

that this thing is made of?

Take a look at the drawing now and see if you can extract that out

in a reasonable

way.

What you should be looking for here is

the largest dimension,

here is my length.

My next dimension here is my total sort of height as it would appear in this

or

the width,

I guess we could say

in this view,

and then I have the height or the thickness

of this

overall part shown right here.

These three dimensions are essential for me as I get started in my CAD model

because I'm gonna start by creating

some chunk of material out of which I will cut out a bunch of holes and other stuff

like this

and these three dimensions,

the width.

Excuse me,

the length,

the width,

and the height

are super helpful.

But I can also notice a really important thing that's going on here and that is that

we

have

basically

like

a trapezoidal

prism

in this shape.

In other words,

they do not have

vertical walls.

And this means I'm going to have to start my CAD work in a particular way,

because the first piece that I wanna pop in here

that isn't actually going to be

a rectangular prism,

it's going to be more like a trapezoidal prism,

and I have to start to understand

that shape.

This is what it looks like from the right side,

also from the front view right here,

we're seeing the same thing,

OK,

we're seeing a

trapezoidal

inward sort of

slanting to those walls.

So, this is a really,

really important bit of information to extract from

this drawing set.

Now,

the major question is how much does it slant in?

Well,

we luckily have this detail view right here

that is telling us that something important is going on in this section,

and we can go find that in Detail A.

Let's go find Detail A.

Here's Detail A.

And

Detail A has

some important information and frankly,

we need to step back just a second

and say,

"One of the first things we have to do whenever we start the drawing,

reading,

the drawing,

the

reading of the drawing is we need to really pay attention to the notes.

The notes are there to help,

like,

to guide and to give direction and to help,

you know what

the creator of the drawing wanted you to know.

So, we can see,

for example,

hidden lines are removed for clarity.

OK,

there's a virtual sharp in Detail A that's

interesting because we're looking at Detail A right now,

and there's something about detail A that's being told to us.

General wall thicknesses are shown in section AA.

Well,

here's section AA,

OK?

And section AA is shown as a slice and not a full cross-section.

If it was a full cross-section,

what this would mean

is that we would actually see

the rest of the object here

without a crosshatch,

but we'd be able to see,

you know,

there'd be like posts and some other stuff,

and it

would get quite cluttered.

So, in this case,

for clarity's sake,

section AA was provided as only a slice.

OK,

now what is a virtual sharp?

OK,

we need to go understand what a virtual sharp is. Because a virtual sharp

is appearing in detail A

and this is an important

part of knowing how the trapezoidal prism

geometry should be made.

So, this little thing that we have here,

I'm going to point to it right now before I draw on it,

that little plus that's there

is the virtual sharp.

What this means is

that if this object

did not have a fillet

in its corner,

right up there,

there's a fillet right in there.

It would have a sharp point,

like what we're seeing right over here.

And that sharp point

would be something that could be dimension too.

And when that sharp point goes away,

such as when there's a filet that's added to something like this,

then

a

marker can go right here.

Let's see if I can switch this color

and

make this even more obvious,

OK?

Then a marker can go right there exactly where the sharp point would have been,

therefore

it is called a virtual sharp.

That can be valuable because

if we want to dimension

to that

we can and we do the dimension to

the virtual sharp and that's actually what's going on

right here.

This 0.85 typical

is going to this virtual sharp.

That helps us to know

what size

that trapezoidal prism

is made at.

All right,

so I'm seeing those 3 or 4 critical dimensions that help

me get my first chunk of material into the CAD system.

Once I have that basic chunk of material into the CAD system,

it's a matter of me starting to chip away

at producing

the geometries associated with that.

So,

I

can see that

because there is

some attempt to describe,

I'll switch colors here for a second,

there's some attempt to describe a general wall thickness,

it's most likely that a shell is used

somewhere in this set,

because the shell gives us a nice constant

wall thickness, and I can see that the wall thickness is shown in section AA,

(whereas it's shown),

it's right here.

OK.

If we're going to look at something that's called general.

Then we're gonna look for something that's called typical

because typical 'TYP'

means that

this same thickness

that's here

also exists here, and also exists here, and also exists here, and also exists here, and

here, and here

and

throughout.

It's a little different over here,

but

nevertheless,

everywhere

in those areas, we would have constant wall thickness.

So,

what have I done?

I have gone into my drawing.

I've tried to figure out how am I going to create my first basic shape.

I've looked at the drawing to pick out

the, the dimensions that are most likely the

ones that I need to create that basic geometry.

Now

it's worth knowing

that there's a lot of information here that's not needed yet.

OK,

so I'm trying to build out my basic trapezoidal prism.

There's some stuff I just don't have to worry about,

OK?

I don't have to worry about,

you know,

this dimension,

for example,

or this dimension.

Those are going to come later.

And the reason why this is important is because

there's a lot of information on these drawing sets

and

you have to be able to start to pick out what

is the important information and what is the not important information

for the given step that you're working on.

And if you had a CAD strategy and your CAD strategy looked something like this,

like you're going to

draw one plane and then I'm gonna switch colors here for a second.

You're gonna draw another plane like this,

OK?

And then you are going to extrude between them

and create some sort of trapezoidal prism.

You would need to know how to first draw

one of those sketches and then how to draw the other sketch,

and what those dimensions would be.

So, you're

looking for those in the drawing set.

All right,

now,

what

else

should we say about this,

OK?

It's important to know,

while you are

looking around drawings for particular bits of information,

there's a couple of rules that you should know about.

Number one,

well,

we don't have any hidden lines on this drawing,

and that's actually good for you right now,

but

you should know that

you're not allowed to dimension to hidden lines on drawings.

This is part of the ASME standards.

You're not allowed to dimension to a hidden line,

and that would mean that if I wanted to know,

for example,

how tall is this post?

Can we go look at the isometric view for a

second so we can know what we're talking about.

I want to know how high is that post.

There's only one way for me to know this in this drawing set

and that is that I have to look for a cross-section,

OK?

And so, let's go see if we can find that cross-section.

Well,

there's a cross-section B right here.

OK,

this is cross-section B and there's no post in that one,

so that's not gonna be it.

OK,

here's some other cross-sections here,

but

none of them go through the post I was wanting,

which was that one.

OK.

So that's a little bit

difficult.

See

what else we have going on here.

OK?

"Oh,

here

we go.

Section-F

goes right through the exact post that I want,

and here's section-F.

Right here,

and it is telling me

the height of that post,

the height of that post is 5.68.

All right,

the height of that post is 5.68.

Another thing you should know about drawings

is you're extracting information from drawings,

and that is

that

lines that,

for example,

I'm gonna look right in here,

OK?

Lines that appear to be right angles

are assumed to be right angles,

that's supposed to be 90,

OK.

Lines

that appear to be on the same line

such as this

are actually on the same line.

And these are important things to know about drawing.

So, for

example,

because,

let's see if I can undo that one that I just did,

OK.

The

height of this post

is this much

and the height of that post is also that same amount,

5.68, because they appear to be on the same line,

OK?

Same thing goes with lines that are flat

appear to be flat

are actually flat,

and all that kind of wonderful stuff.

OK,

what else do we need to know about this?

We need to know that

there are some symbols on here that

need to be described.

OK.

This is a complex one,

for example,

OK?

This means that there are 6

features that have a diameter of 1.44,

see if we can think about what that is,

there's 1,

there's 2,

there's 3,

there's 4,

there's 5,

and there's 6.

How do I know that those are the ones?

Because when you come over here and you look at this,

all 6 of those look similar.

OK,

I got to get back to sketching and not erasing

that one,

that one,

that one,

that one,

and that one and that one.

All appear similar. And in this

drawing image they also all appear similar

and the fact that there's a dimension that says 6X

means

that they are.

Now what does this symbol here mean?

This means that there is a hole,

and it's pointing to a hole,

OK,

you can see it pointing right there to that hole.

This hole that's right here

is

5.68 millimeters deep.

Now,

if we couple that together with what we saw in the cross-section,

we can actually see that hole,

it's right there.

OK,

it goes all the way down right there and it

is in line with this.

And so, we know actually that we've interpreted that

correctly.

Let's see if there's anything else in here that's

interesting to talk about right now

other than

the stuff we have already talked about.

I think this is a good one right here.

Let's take a look at this for a minute.

Maybe this drawing has more than one that will help us,

OK,

this is good.

There are two things going on on this drawing that

are on this view that are worth thinking about.

One is the fact that sometimes

8X is used

and sometimes a thing called typical is used.

'TYP' means typical.

Well,

we already know the 8X version of this.

It means that there's 8 radii

of the same exact

size,

and they should be easily pick out a ball

in this drawing.

There's 1,

there's 2,

there's 3,

there's 4,

there's 5,

there's 6,

there's 7,

there's 8.

All 8 of those are 1.3.

But over here,

we have something different going on,

OK?

We don't have

a certain number,

you know,

like 12X or something in front of this 1.00.

We instead just have 1.00 typical.

Why is that the case?

Well,

if we take a look at this guy,

OK,

and let's go erase some of this stuff that I had on here earlier.

OK,

if we look at this guy,

I'm gonna turn this one to blue for a minute.

I've got 1-2-3-4-5-6-7-8-9-

10-11-

12,

but then I also have

this one in red

13-14-

15-16-

17-18-

19-20.

20 geometric features that have a dimension of 1,

just in this particular part of the image.

And so, the way that that's dealt with is not

to say,

well,

what number did I say?

I don't know,

is it 16.

No,

it was 20.

It's not to do this.

But instead,

it's to say 1.00 TYP.

Because it's more obvious that that's what's going on

in this area.

OK,

erasing those.

All right,

what

else do we need to talk about?

It's important to know that circles

will always be designated

by the standards as a diameter and arcs,

not complete circles,

will always be designated by a radius.

It's also important to know that in engineering drawings,

according to the standards,

circles will only be dimensioned where they look like a circle.

So, if I had a shaft,

for example,

that looked like this,

and I had an engineering drawing that looked like this,

I would dimension this one

in this view,

not

like this.

OK,

this one is diameter something.

This is no good.

And the reason why I'm telling you that is because as you look for information,

you want to make sure

that you

are

looking in the right spot.

So, if you're looking for the dimension of a circle,

look where it actually appears

like

a circle.

OK,

a few things I want to just go over here for a second.

As you're trying to extract out the information from these drawings,

(let me just zoom out here for a second).

We want to start

by getting an overall view of the drawing by just scanning through it,

understanding what images are there,

trying to absorb a little bit of stuff,

OK?

We want to take a look at the title block,

see what information is given there.

We definitely want to read the notes,

OK?

And then we want to start getting the top level information

that will help us

to start building out the geometry.

OK.

While

you're doing this,

you want to learn to look for clues

in the drawing,

and I don't mean this from an educational perspective.

I just mean that there are certain things like

general wall thickness that's going to tell you

there's going to be a shell somewhere,

right?

Or

there are

things like these virtual sharps that we saw here that mean that

really we're trying to give a dimension before a radius would occur in a CAD model,

right,

or before a radius occurred in a manufacturing

step.

Also,

we

want to take a look at the cross-sections.

We want to know that the cross-sections are there to help us

and we want to really try to absorb the cross

sections and understand what's going on with the cross-sections.

Then we want to do our best to soak in the details

of the detail view,

right?

What is this telling us?

This is an interesting one right here,

OK?

Because

this line

and this line

are parallel to each other and this line and this line are parallel to each other.

This is interesting because

there are other ways

to

have measured this.

Yeah,

we did this one and this one,

OK?

We could have measured like this,

and these give us two different numbers actually,

and this is something that can cause trouble in this particular

model.

So,

understand

what

these things are telling you,

OK?

Also,

most

important,

I think as you're looking through these engineering drawings is just to realize

that the information is there.

You don't need all of it at once.

You need to use your CAD strategy

to help you know just what bit you need,

what feature you want to create so that you can get into this

set of drawings and go find the essential

dimensions

that will help you get it.

So, I'm coming back now to

just sort of end of this and say that it

is indeed really hard to read these engineering drawings.

It is a foreign language in my view

and it takes practice.

It takes

patience

and it takes a willingness

to actually read them,

and to try to

see what they're telling you, and to envision the geometry

that's being described.

And as you do that,

your mind will be able to

notice certain dimensions,

certain features,

certain patterns,

certain other things

that will help you

during the CAD modeling process.