CAD 101 Module 2: Mastering Sketching Techniques for Design

let's talk about module two and we're going to be looking at sketching uh sketching is a super handy

tool and we use it a lot many many designs in fact I I'd say the vast majority of designs all start out with

some sort of sketch it might be a sketch from a customer or from an engineer or an architect or maybe it's like in a

design team and you're together working with the design team and you're the one that starts sketching it and then you

take that sketch and it comes back to you and you build it in CAD and uh so actually that's the ideal kind

of situation is if you can do the sketch on your own then really you uh have a little bit of background you can

make sure that you get everything that you need into that sketch and it's also really quick and easy to do as well you

know all all it takes is just uh piece of paper right and uh graph paper is is really handy to use there's some

Square graph paper there if you're going to try to draw it in isometric it's really nice to have some isometric graph

paper and then of course need a pencil I prefer like a relatively large pencil

size this one here is a 0.9 millimeter pencil but like a 0.9 millimeter or a 0.7 millimeter out of your drafting kit

works great an eraser eraser is always handy uh so let's uh let's jump in we'll look at

what's uh what we've got for Content here in our module two of CAD 101 here in my

wdt this is the PowerPoint that we're going to go through today also available out here we've got some

printable isometric graph paper and uh Square graph paper so if you want to practice a little bit beforehand also

have some of that stuff printed out in class and uh then here's the step-by-step

instructions I'm sure you're getting pretty familiar with this moving forward here and and really we're we're right

here on this step number one doing our video discussion of the uh of the module right so we'll look at the PowerPoint

presentation not that one that one all right there we go

so sketching by the goal is by the end of this module everyone will be able to crank out a sketch that looks kind of

like this now maybe not I can't do that either so um this comes you may have seen

something like this it comes from Asher and uh looks like they're the people in this uh sketch

they're either all going up or they're all going down and they can keep going around in circles but uh so sketches can

get tricky but we're just gonna look at kind of the um the most important and the and the key

techniques of sketches there so um there's our objectives we're gonna be able to sketch lines circles arcs and

other geometric shapes uh be able to sketch multi-views which really means that we talked about that in our last

class the uh the front the top and the the right side view we can also have uh total three other views added onto there

too but they always stay lined up and we'll check that out and then also be able to sketch an

isometric make some isometric and onto that as well oblique sketches we'll we'll look at all of those three types

of sketches and uh here's kind of an interesting uh you know a sketch that started out man

whoever did this was quite the artist it was not me well it looks like it started out on a chalkboard and you know this is

just a design concept there looks like they were brainstorming how to uh make this little portable water tester that

you drop in your drop in your drink to make sure it's safe to drink maybe if you're traveling

or something like that um here's another example of a sketch this

is definitely a napkin sketch right this is like the type of sketch that you get from maybe an architect or even worse

like an engineer um or or maybe it's a customer but this one looks like it it came from like um

somebody that was trying to had some ideas on a kitchen room model or something that they wanted and and

here here you go uh draw this up in cat so and they're they just they end up with

as as the basis for uh all all of our Downstream deliverables

and it's a key element in our uh design process uh other advantages of sketching it's

just fast we get visual communication that lets us kind of organize our thoughts and then and that minimizes

errors when we go in and uh actual build the the drawing and um

they sometimes even sketches they might be end up being technical illustrations on reports but

that doesn't happen quite as much anymore you know it's really uh we we've got such great 3D modeling that we can

get um 3D or conceptual views of a 3D model a little bit better than um

then sketching it and uh just kind of to illustrate that point here's a

here's a sketch that um is just uh kind of a reference sketch for one of the 3D printed cars that you use as an example

in one of the third semester classes so that's what we're starting with going through the whole design process start

out with an isometric sketch kind of get your ideas down there and uh and then move forward from there

other things that sketching is really good for um recording uh recording Dimensions

when you go to reverse engineer something so for example this right here is a sketch of half of a wheel

so if you imagine cutting this wheel in half and looking at it this this wheel these are dimensions

inside that wheel recording the outside and then we would draw this up in a parametric solid modeling program and

then we would take that and kind of revolve it around and then we would have most of this wheel but

putting all the dimension doing your measurements and then putting all the dimensions down in a sketch are is a

really helpful way instead of trying to like take your measurement put it in CAD take another measurement put it in cat

and it can also be a tool for problem solving as well we were trying to figure out about how a linkage might work or

something like that and so there's our tools we kind of we kind of talked about that already at our

um very intro we just need a pencil paper and an eraser that's uh that's really all we need there

sketching straight lines you know uh when you're sketching a straight line especially when you have graph paper you

can do a pretty good job of just following Along on an existing line on the graph paper if you're starting from

scratch a lot of times it'd help it's helpful uh to just kind of sketch little in little short Strokes as you're

going along and um is it's also okay like if you're if

you're drawing like a a rough out line of the part and um or maybe uh an outside box to kind of

decide how big this is going to be just for starters and then you're you fill in there so you can kind of uh start out

with just very light lines and then come back later and darken them in and that's that's kind of the the dot to

dot method I guess you know once you once you have the the key locations in there then you can darken your sketch in

after that um so drawing um small circles small circles

is is pretty easy to draw just you know just with one one Loop like that sometimes it's it's easy to do in Two

Strokes just a half a circle there and another half circle there that'll get you a small circle if you're sketching

the large Circle though uh something like this I actually I cheated on this one I used a circle template to uh get a

really nice uh the circle there but um if you're drawing a circle in a on Square graph paper

it's helped helpful to visualize you know like what would a perfect square look like on that

and then start out in the center of one of those perfect squares and then just connect all of the the edges the

midpoints of the the edges of that square and that'll give you a pretty good pretty good Circle

and and it also does help there as you're sketching those kind of those longer arcs to just go in in short

Strokes as you're going around there that'll get you a pretty good estimate and then you can come back and darken it

in after you get the shape the way you want it arcs uh this this really kind of

summarizes what we're just talking about you got a box and uh usually that one works best uh it it doesn't hurt to have

a center line in there as well where you know where the center of your Arc is going to be you got your Center Line and

then really the center line is going to be like here if we know where the center of

this Arc should be we come out if we've got our our Center kind of sketched in there

we know that on our box it's going to meet at the midpoints of that box and then we can come in here and

China sketch our Sketcher each of the arcs to form that

Circle um yeah and the the ends of arcs are usually tangent to adjacent lines and so

what that means is like for example if we look at this maybe like this car body right here let's just say for example uh

this roof is is a straight line and we want to blend that into another straight line here

these this Arc that goes from here to here it's going to be a nice smooth blend and

that means that it's it's tangent we'll get into the term tangent a lot more in this class it's tangent at those two

points and then we also want to try to keep our sketch proportional uh

so that just means it's it's not like if you're drawing something let's say this this mouse or something

like that um it doesn't necessarily have to be this exact same size but the proportion

of the length to the height should be pretty close to what it is for the actual part from your paper to

the actual part um one thing that that helps with keeping

things in proportion is to first sketch a box that you think your part would fit into

and then kind of work your way in from that box and the Box might get it might just be

super light and be left there after you're done or maybe you want to come back and erase it

went the wrong way there all right so this is um the sketching technique using the block kind of been

discussing this and it it just helps control our proportion so this is actually an isometric sketch that we're

looking at here and so they started out with this blue bounding box

and um in isometric sketching so really this here's a here's a three-dimensional box

that that part would fit inside and well there should be a line right here too

and then once you have that box then you can start filling in the side so on this side we

know we've got kind of this trapezoid shape and then we've got a couple Square shapes on the the two end corners

and that really helps with our proportion not only in isometric sketching but also in 2D sketchy

so here's an example of 2D sketching we kind of put a frame of reference it's not really showing on here but we have a

frame of reference that wraps around this part here and then from there we can work in and

we can sketch this shape in and maybe that frame of reference it it started with outside and maybe the

center point here this is some some sort of uh crazy plate cam and it's going to there's going to be a

follower that goes on this thing that runs right here and then we've got a

shaft that's going through right here and as that shaft rotates

this plate is gonna loop around and our follower will follow that and create some sort of motion

all right so multi-view sketches this is the first type of sketch that we'll do and um

this is a method of orthographic projection which just means that you're looking at a face straight on or at a 90

degree or Ortho orthogonal angle to each of those faces

so for this part right here we've got the um

this this part here it actually does not match up with this drawing

um but uh it's it's just here to kind of illustrate what we've got going on so when you have when you have a part

you can pick out well I want this to be the front view and this to be the top view and this to be the right side view

and it's it does match up with that sketch but that sketch they didn't do a very good

job of of making the proportions so like this front view right here would be

looking at it like that and so this surface right here

right in there is this surface right here and then but you and you can see like it

looks like an isometric view it looks like it's taller than it is wide but here in the sketch view the

proportions are a little bit out of whack and it is wider than it is tall but

um this does show how those views stay lined up so once you create the front view the top view is always going to be

directly lined up with it actually let me let me go like this so here that's that's lined up and and

all of these features from the from the front view line up with the top view

same thing goes for the right side all the features from the front view line up with the right side view

and there's also a way to link the right side and the top views and we'll get into that more in the future

okay so here's kind of that same part in the sketch format

this looks a little bit more um you so so you can see you can see the

alignment here and this also shows a tool that we're going to use quite a bit here quite a

bit in the AutoCAD that allows us to line up the right side view and the top view

so it is and it is called a miter line so the miter line is located off of the innermost edge of the the top view

innermost edge of the right side view where those intersect we can draw a 45 degree

line which is really easy to do when you're working with square graph paper because you just go right through the

corners of the squares and then this allows us to figure things

out about the right side view or the top view and connect those views together so

let's say we wanted to know where's this hidden line right here well we know where that corner is in the

top view we can shoot that across to the miter line drop it down and that defines right

here where that hidden line is a similar thing goes maybe we don't want in this in this one we knew where this

line was in the right side view we were able to draw and locate that but we want to know well where is it in the top view

so in the top view we could bounce up to the miter line come across here and that locates that line right there

isometric sketches so we'll look at this a little bit more here and um

they just do a really good job of getting that 3D visualization going on and so especially for folks that are not

trained in visualizing uh orthographic sketching and multi-view

sketching where you've got the the front top and right side that can be really hard for someone that's not used to it

so a three-dimensional sketch is a little bit more realistic helps you visualize it

and um when we do these we we start out with three axes

and then we can any line that is parallel to those axes is

um is considered an isometric line any line that's not parallel to them is

considered non-isometric line so we'll look at that when we do an example here but isometric lines they will allow

always be to scale or if it's a one-to-one scale drawing they will be the the actual

measurement anything that's not parallel to the isometric axes will be distorted so really the first step in drawing an

isometric sketch is to create the axes

right and so we've got isometric sketching paper here and there's a bunch of lines on there

there and um we can select really where we want our lower our front

bottom kind of a front bottom like right corner that's closest to us we want to select where that is and there are some

precise ways of locating it which we'll get into in the future but for sketching usually you can kind of you have a you

can guess at it pretty well so here we say all right about down here on our piece of paper

that's where we want our isometric sketch to start we're gonna and then we begin with a vertical line for our axis

and then the other two axes to the right which is kind of like often to the back of the part

that we follow a line at a 30 degree angle and then in the other direction we

follow a line at a 30 degree angle back into the left that gives us our our isometric axes

and anything that's parallel to those any one of those three axes will be undistorted but anything that's at an

angle will be distorted so for example if we started here and we made a bounding box on this thing

it would end up being something maybe like like this all right we've got something like that

there's our bounding box we're going to try to fit everything inside of there now if we were to let's say we were to

draw uh a square on this front surface right here

oops that was not very good good square but let's let's try like this all of those lines are parallel to the

isometric axes they will be undistorted but uh let's say we have a

over here on this right face we've got a slanted line or slanted surface along here

this if we measured this line on the piece of paper it's not and and this we're making this

sketch the exact same size as we as uh the actual part we're able to fit it on our piece of paper so this is a

one-to-one scale like if we measured this vertical axis and that was two inches

and we measured this one and it was an inch and a half and then we measured this on our actual

part and we came up with the length of that maybe it's an inch and three quarters or

something like that on the actual part on the piece of paper that's not going to be an inch and three quarters

only because it's it's kind of been distorted so that we can get it

three-dimensional representation of our part on a 2d piece of paper all right so making the isometric sketch

we talked about you put your axes on there you form the bounding box

draw in what you know is on each of those three surfaces that you can see

so really on here after we get our bounding box on there pretty easy to draw what we know is on

the front surface of this part and really we're just kind of connecting the dots essentially on this top surface

right here there's there's really nothing on this top surface except for an edge

so we can draw that edge in there on the right surface the only thing that's actually on the right surface are

these two little Nubs these two little squares right here and so then once we have filled in there

what we know are is on those surfaces then we can start connecting the dots so like here to figure out this back Edge

well we just gotta we connect from here and it runs down and ties in right there this part is a little bit more tricky

here we we really need to know like where where this point is

and in order to figure out where that is if we know where it is going to be on let's say the front view if we were to

look at it from the front view we could pick out that point we've got a draw a construction line that comes back

here parallel to an isometric axis and then we can draw this other line

if we know that line is going to be parallel to let's say this line right here in the front we can keep them

parallel draw it up until it runs into there a similar thing we'll draw that up until

it runs into there and then this last kind of back corner there

that we can draw in we know it's vertical and it just so happens that it overlaps with this uh original vertical

axis and so then we can draw that in there this one to finish it out we know it has

to be parallel to one of our isometric axes so we can draw that one in back in parallel

so that's basics of isometric sketch isometric circles and arcs a little bit more tricky

and um here we don't have any circles and arcs on this thing but the best way to create

an isometric Circle and an arc and or an arc up here

is first to draw everything on our part that has the straight edges get that laid out and then come back in

and try to put your isometric Circle and arc on there and so let's say we're going to try to we're going to drill a

hole in this face and we need to put the representation of a circle there if we can imagine what a square would

look like on this face it would look something like this

everybody agree with that all right it's not an actual Square on the piece of paper though right it's

it's kind of been like squished like that and so we know that a circle

will fit inside of a perfect square and touch the edges and so now we can go back and try to put

our Circle in here and so that square we would have just very lightly sketch that square

um and then we can say all right well our circles gonna touch the midpoint of the

square there midpoint midpoint and midpoint there and then we can see how our Square was

distorted and distort the circle in the same way to get it looking right on there

so um so now our circles

gonna end up looking it actually becomes an ellipse harder to draw on the computer screen

but it's going to look something like that so it's become egg shaped like that now on one of these other on the like

the right side surface now I'm I'm going to greatly exaggerate this but after we if we were to do the same method with

our Square it would be egg shaped kind of like that or like

yeah the the camera flips it around so my fingers are not pointing in the right direction but uh and then on the top

surface similarly it would be squished like this to get it to fit on this the top surface

right so a circle on the top surface is going to look something like that we'll look at a

better one representation for that here uh so foreign these are those isometric circles

and um front surface over here it's squished sideways

and the right surface over here it's squished this way and then the top surface it's squished like that and as

long as you the the most Fail-Safe method is to just sketch in the representation of a square on your

isometric grid paper and then fill in your your ellipse there it's really really tempting to just kind

of start filling in your ellipse but uh it's uh it's it's just way easier if you put the

square on there first Square which is actually a distorted Square which looks like a kind of some

form of diamond all right and then the last type of sketch that we have to look at is an

oblique sketch so oblique is another way of showing um something in three dimensions and

it's a it's a kind of a quick and easy way to add depth to things that are not super detailed going back

uh so for example here on this part it's just kind of like this sideways tip b or whatever you know and um so

the drafter went in this you know sketched this out this is what the front view

would look like it's undistored and then to add depth to it it just came in and at all of the corners

at a 45 degree angle they added some depth just like that and then

um that amount of depth that's being added we'll use some rules of thumb in our

in our assignment but really that's kind of up to the the drafter or the Sketcher they're

going to add depth to make it look about about good what you want for a depth and those depths if it's a consistent

thickness that part that we're sketching we add the depth just the same amount in along all of the

from all the corners or all of kind of like the outside boundaries when you're adding depth to an arc it's

a little bit more tricky you just have to like imagine where a 45 degree line would touch that thing so it would touch

it right there and we add that depth back there and then

we just connect the connect the dots so all those consistent depths we connect them

and really it's like we're taking our that first view that we had and we're moving it back and to the right

and then only drawing in the portion that we want there in theory you know there would be some

hidden lines in here but um usually hidden lines are not shown on sketches that are 3D either oblique or isometric

they just add uh extra confusion there so hidden lines they can be left out so there's our intro to um

module 2 and I really recommend going in look at the homework assignment

and look at some of those parts try printing out some of the uh graph paper

isometric and the square graph paper and then try sketching a few of those on your own

and and then even you know try sketching just anything and maybe try it in try uh and

an isometric sketch try an oblique sketch and then try a multi-view sketch or an ortho orthographic sketch of

something let's say maybe it's even like this calculator you know how about that so we put it on our drawing and uh

I guess it'd be over here so here's our here's our front view and then so then our top view

would look like that and then our right view would look like that over there

okay and then if we're gonna do an isometric of it it's kind of like we'd be kind of

looking at it something like that if we're going to do an oblique view of it

we would take the front view and then we would just add depth to it kind of like back into the right

at a 45 degree angle and then I'll add a little bit of depth onto there so give that a try so that you know what

questions you might have on the homework assignment for when we meet in class and we'll see you then