Lesson video

Hi everyone, my name is Mr. Booth and welcome to your design and technology lesson for today.

We are looking at communication.

Today we're going to be looking at interpreting orthographic projections.

As you know, as you work through your design and technology lives, you have to communicate your ideas and your designs in a variety of wonderful ways.

Well, today we're going to get technical.

Today's lesson is all about interpreting orthographic projections, why we use them, and understanding the rules that we have to follow to be able to do an orthographic projection.

By the end of today's lesson, I hope that you can interpret an orthographic projection and be able to sketch shapes in 3D.

I really hope you'll also be able to add things like dimensions and be able to label parts of orthographic projections so that in later lessons you will be able to then create your own orthographic projections for yourselves, which will be a really valuable technical working drawing for your design and technology work that you do over the next few years.

We have got some brilliant keywords for today.

Some of these you may have never come across in your lives.

The first one is of course orthographic.

Now orthographic, it represents 3D objects in 2D where the views are projected from one of the object's surfaces.

And we're going to go into detail on that.

We also have isometric.

Now, isometric you might have heard of.

This, of course, is a 3D representation of an object where all sides are shown, or sorry, are drawn, at 30 degrees from the horizontal line and you might have drawn in isometric already even without knowing it when you draw a cube in 3D.

We then have dimension, a really important part of an orthographic projection.

These dimensions are of course measurements and they're drawn to show the exact size of parts no matter what scale we are drawing at.

And then finally, we have a centre line.

Now a centre line is a dashed line that marks the middle of a hole or a symmetrical part of an object.

And again, we use these all the time in our orthographic projections.

So I want you to look out for these keywords as we go through them in the lesson.

And you'll see them coming up all the time.

Two learning cycles today.

The first one, orthographic projections, an introduction to those, and then applying standard conventions, which are the rules that govern how we draw these fantastic projections.

Let's get going.

So an orthographic projection is a technique for representing a three-dimensional object in two dimensions.

Now that sounds quite confusing.

So what we're going to do is we are going to display the object from multiple angles.

But when you combine all those views together, they create a complete picture of the object.

And that's quite a complex thing to understand and also to do in the real world.

Now in the real world, builders, engineers, and designers use these drawings all the time because they are mainly used for making or manufacturing the products that we love.

For example, our houses, the machines we use, or the furniture that we buy for our homes.

Now, most orthographic projections, most of them include three views.

We have what we call the plan view.

Now that is the view from the top.

So that would be like looking down up on my head, what the object looks like from above.

We have the front view, which shows what the object looks like from straight ahead.

And then finally we have the side view, which of course is what the object looks like from the side.

When you put all those views together, you get a complete picture of the object without needing to see it in real life.

And if you then add things like dimensions and manufacturing information, you can then make that product very successfully.

Now, before beginning to create an orthographic projection, you need to be able to label the three views of whatever object you are wanting to draw.

So here we have two really simple 3D objects.

We've got a cube and we've got a cylinder.

So let's label the views on each of these shapes.

So if you remember, the first view we need to have, can you remember? That's right, it is of course a plan view, what the object will look like from above.

The next view? Excellent, it's the side view.

So what the product might look like from the side.

And then finally, of course you got it, we have the front view, what the product looks like from the front.

So it's really important to be able to label each of those views before we start producing any kind of orthographic projection.

So, quick check for understanding.

What are the three views on an orthographic projection called? Is it A, front, side, and plan? Is it B, front, side, and bottom? Or is it C, front, side, and side? Pause the video, have a go.

Come back when you've got an answer.

If you answered A, front, side and plan, brilliant, well done.

Orthographic projections have three views.

We now know that.

Okay, we can label them and we know what they are.

All three views need to line up.

They need to be the same size or what we call the same scale.

And they have to have that because obviously they're part of the same object.

Now we line these up using what we call construction lines, and it's really important that you draw those on your drawing.

Otherwise it can look a little bit messy and it might not line up properly.

Another quick check for understanding.

Which is the correct definition of an orthographic projection? Is it A, a 2D flat view showing two views of an object? Is it B, a 2D flat view of an object showing the front, plan, and side separately? Or is it C, a 3D view of an object showing how it looks in real life? Pause the video, have a go at that.

Come back when you've got an answer.

So if you answered B, a 2D flat view of an object showing the front, plan, and side separately, well done, you've got it correct.

Now, quite often shapes will have other features on them, such as holes or cutouts or sometimes detail that is not visible from the three views that we want to use.

Now because we want to use these orthographic projections to manufacture a product, we still need to be able to show whoever is going to manufacture them where these details are.

So to do that we use what are called hidden lines, and we represent these using dotted lines.

So in this example, you can see there are some hidden lines on there.

So what do you think the dotted lines are on image B? You can also see some at image C as well.

But think about it, what do you think those dotted lines are showing on image B? Pause the video quickly, have a chat with the person next to you and see if you can figure out what they're actually showing.

So what those dotted lines are showing are showing the thickness of the ring, the cutout you can see in image A.

Now, there's no way the cutout, the hole in the middle of image A, you can show on B and C.

There's no way of doing it.

So what we actually do is we create hidden details by showing the lines of where that cutout will be.

What that means is that I can see on image A there is a hole.

I can see on image B that it cuts all the way through.

And then I can confirm that on image C.

So what I've got is a representation of that feature really well in those three views.

And that is using hidden lines.

Another check.

The three views for an orthographic projection can all be different sizes.

Is that true or is that false? Pause the video, have a go.

Come back when you've got an answer.

Did you answer false? Hopefully.

But can you explain why? Why the three views of an orthographic projection can't be different sizes? Again, pause the video, have a go at answering that, come back when you've got one.

So why? Well, of course the views are connected because they show different sides of the same object.

They've got to be the same size.

We want to make sure we can dimension them.

We want to keep that scale consistent, and that's what we need to do to be able to make the products.

Well done.

If you remember at the beginning of the lesson, I said that one of the keywords was isometric and orthographic.

And the reason isometric is also included in this lesson is because quite often we use an isometric image or an isometric drawing of the object or the products that we want to make on an orthographic projection.

And there are reasons for this.

So let's look at the fundamental differences between these two types, these two techniques of technical drawing.

So here we have the same product.

So in the image we have an isometric drawing of it.

Now the features of this is it shows a 3D view of the object.

It's like a real life view.

And also because it's 3D, it allows us to see multiple sides at the same time.

Three dimensions, three views.

Now why do we use this? Well, it helps to show us what the object will look like in 3D.

And it's useful when designing or making products to have a 3D representation of that product.

Now this has been done in computer-aided design.

You can print it off and obviously put it on an orthographic projection.

But in 3D computer-aided design, you could also rotate around this isometric drawing to be able to see what it's like in real life.

Now an orthographic projection is of course different because we've learned that now.

This shows 2D flat view of an object and we have those three sides, the front, the top, and the side, they're shown separately.

Now this is used for technical work, for engineering, manufacturing, because we want to make the product, but when you combine those two together, you get a very detailed technical drawing that you can then use to manufacture products.

So, quick check.

What I would like you to do now is, out of all these different techniques and drawings, I want you to identify all the orthographic projections.

So take your time with this, maybe have a chat with the person next to you.

When you think you've identified all the orthographic projections, come back to me and we'll see how you got on.

Let's see how you got on then.

So did you answer B, D, F, and I? If you did, well done.

They are all the orthographic projections.

Everything else that you can see on there are different forms of communication that we use in design and technology, but they're the ones we were looking out for.

Well done.

Now for your first task, I would like you to look at this orthographic projection and do two things for me.

First is label the front, side, and plan views.

And then from the drawing, I want you to see if you can sketch the 3D object.

This is a really useful task to be able to visualise what an orthographic projection is trying, the information the orthographic projection is trying to give us.

Have a go at it, pause the video.

When you finish, come back and we'll see how you got on.

Let's see how you got on.

So I've labelled all mine.

I've got front, sorry, I've got plan, view, side view and front view.

I've also done a really nice isometric view of what the product actually looks like.

And hopefully you have got something similar to that.

If you have, well done.

So the next task for this, task two, I would like you to identify the correct orthographic view, that will be the plan, the side, or the front, by looking at the isometric drawings you can see on the right hand side of this.

I would like you to pay close attention to the direction which the arrow is pointing.

So which view is that arrow pointing at? I would like you to identify it on the choice of three views that you have next to it.

And then also I would like you to label it as well.

So look very closely at where the arrow is pointing, identify which of those is the correct view on the right hand side, and then make sure you label it as well.

Have a go at that, pause the video.

Come back when you've got all three answers.

So how did you get on? So hopefully what you did is you looked at that first image, which of course are steps, were the steps.

And what you did is you saw the arrow was pointing from above down onto the object.

So you decided that was the plan view and hopefully you recognised that that plan view would look like the third image out of those three that you can see.

The next one, this looks like almost like a shelving unit, doesn't it? And I've decided that that is the front view that the arrow is pointing at.

And what I've done is I've ticked the view which I think would look like from the front.

And then finally, this almost wheel that we've got there, I think this is the side view.

And obviously a cylindrical object looking from the side actually just looks like a rectangle.

So I've ticked that middle image there.

So hopefully you got something similar to me.

Well done if you did.

We're now onto our next learning cycle, and this is apply standard conventions.

We've already looked at several rules for creating an orthographic projection, such as the three main views, front, side, and plan.

The alignment of the views, so we make sure that they line up and we use construction lines to do that.

We have a consistent scale that shows accurate measurements.

And of course, we've looked at things like hidden lines, dotted lines that show parts that are not visible.

These rules, we call them standard conventions.

They're just rules, but that's the name that we give them.

Now there are some other standard conventions that we need to think about and we need to use in our orthographic projections to make sure they work.

One of those is the centre line.

Do you remember that from our keywords? This is a thin dashed line that marks the centre of any holes or symmetrical parts.

We also want to include dimensions.

Well, of course, if we're going to make these products, we need to know how big the parts need to be.

So we need to add the measurements with numbers and lines that show the exact sizes.

Remember, no matter what scale we are working to.

Now these rules, they help engineers, architects, and builders read and create precise drawings.

And if you think about it, if I designed a product here in the UK and I wanted it to be manufactured somewhere else, let's say over in Japan, and I sent them a technical drawing and we used all these standard conventions, they would be able to read that technical drawing.

And that is really important when we are manufacturing products.

And these standard conventions ensure that everyone understands the technical drawing in the same way and it's a bit like a universal drawing language.

Isn't that brilliant? Quick check.

Standard conventions just means adding dimensions to an orthographic projection.

Is that true or is that false? Pause the video, come back to me when you've got an answer.

It is of course false, but can you explain why? Again, pause the video, have a chat to the person next to you.

Come back to me when you think you can.

Well, of course it is.

Whilst dimensions are a standard convention and are really important to be able to manufacture the products, we can also include things like centre lines, the three views, alignment, hidden lines, and of course, you know, scale because I've talked about that quite a bit as well, haven't I? So let's look at centre lines now.

So adding a centre line.

So it's usually drawn with an alternating long and short dashes.

Sometimes it looks like a little dot on there, but that's your centre line.

Now, a centre line will be used to show that you have a symmetrical shape to show that it's the same on both sides.

And that's really useful when dimensioning because it means you don't have to add as many dimensions if you know a shape is symmetrical.

But also we use it to show the centre of a circular part or where we have holes.

Just as if you are going to manufacture something with a hole in design technology, you would use a crosshair to mark it out so you can then drill it accurately.

It's the same principle here.

Now about adding dimensions.

Now, we have to do this in a very specific way.

When adding dimensions, we use a double-ended arrow, and the dimension is always positioned above the arrow line and it's usually in millimetres.

In most of your design and technology practise, it will be in millimetres.

If you go on to be a designer or engineer, you're probably going to have to work in inches as well because of course that's how the USA does all their dimensions.

But for now millimetres is absolutely fine.

So here you can see we have our part that we've been looking at already and we can see we've dimensioned two things.

We have dimensioned the top part, 15.

8 millimetres, and also we've mentioned the diameter of the hole in the middle, which is 20 millimetres.

That's what that little symbol means.

The little circle with a line through it is a diameter.

We have allowed enough space around the object.

We don't want to add dimensions to sit within the object.

If you do, it can get confusing.

If you imagine you have a quite complex part and then you've got lots of numbers on the inside of that part, that can actually detract from us being able to manufacture the product correctly because it makes the drawing very busy.

And here you can see two examples.

One which is of course correct, one which is of course incorrect.

And I'm sure you'll agree that the correct one looks much neater and it's much easier to understand, because that's really what we want do is communication.

We're trying to communicate as clearly as possible the size of this object or this design so we can manufacture it.

Now on to task B.

For this, I want you to look at the orthographic projection.

Using a ruler, I would like you to add some dimensions.

Do it to scale.

So actually measure the product that you have in front of you, whether it's on your sheet or whether you have been given a product by your teacher or whether you have a product at home.

Show the alignment and label the three views.

So you're going to have to draw some construction lines to do that.

What I then want you to do is using the same dimensions, is sketch an isometric view to scale.

That's quite a tricky task.

Your checklist.

Have you added those dimensions? Have you shown that alignment? Are the three views labelled? And have you included an isometric view? Have a go at that.

Good luck.

When you've done it, come back and let's see how you've got on.

Let's see how you got on.

So hopefully your drawing looks something similar to mine.

You might have your dimensions in different places, but hopefully you've got enough on there that you could actually manufacture this product.

So let's just go through the checklist to make sure we've done everything that we needed to do.

So first of all, have we added the dimensions? Well, yes we have.

And if you notice on my dimensions, I've not repeated any dimensions for the same features of these parts.

What I've done is I've made sure I've got enough dimensions to be able to make the product, but not too many to make my drawing too busy.

You can see that I've aligned everything to make sure everything is aligned using my dotted lines.

We have three views are labelled.

I've got my top view, my front view, and my side view.

And we've also got our lovely isometric view added so we can see what it looks like in 3D.

Well done with that.

That's quite a complex task.

Now you should have all the skills you need to be able to apply standard conventions for orthographic projections.

So we've now come to the end of the lesson.

Here's a quick summary of everything that we've learned.

Orthographic projection is a way to show an object in 2D from different angles, front, side, and top.

Orthographic and isometric drawings are different.

Isometric shows a 3D design, whereas an orthographic projection shows 2D views of an object.

Standard conventions are used to help everyone around the world understand and read and interpret drawings so products can be manufactured successfully.

You've been absolutely brilliant today.

That was a really complex lesson and you've done fantastic.

Well done.

See you again soon.

Bye-bye.