Lesson video

Hello, thank you for joining me for your Design and Technology lesson.

My name is Mrs. Conway and I will be guiding you through your learning today.

So today's lesson outcome is I can manufacture safely using equipment and machinery.

And these are today's keywords.

Adhesive, mechanical fixing, thermopolymer, and friction.

We'll go through each one of these in more detail as we work through the lesson.

So the first thing we're going to look at then is thermoforming.

Now, polymers can be categorized into two groups.

The first one of those is a thermopolymer.

Thermopolymers can be heated and formed repeatedly.

Now, some quality is also lost through the repeated reforming.

Thermopolymer examples include things such as high-impact polystyrene sheets, or HIPS, acrylic and polypropylene.

The other group then are thermosetting polymers.

Now, these can be heated and formed once.

Thermosetting polymer examples include things such as epoxy resin and also urea formaldehyde.

Now, thermoforming is a deforming process which changes the shape of material without removing any parts.

It uses heat and a force to shape polymers into a new form.

Deforming polymers makes it easy to create curved or angled shapes that would be hard to cut directly.

Here's an example in the image of yogurt pots that are made by the thermoforming process.

Okay, quick check for understanding on those points we've just covered then.

What is a deforming process in manufacturing? Is it A, changing shape by cutting material; B, changing shape by joining materials; C, changing shape by force without removing material; or D, adding a coating? Pause the video here just to take a moment to think about your answer.

And the correct answer? It was C.

So deforming is changing shape by force without removing material.

Well done if you got that right.

Now, thermopolymers can be heated using different methods.

Here's an example of a thermoforming oven.

Thermoforming ovens are versatile as they can heat up different shapes, sizes, and types of polymer.

Once the polymer is heated, it is removed from the oven, shaped into the desired shape using a former, and then left to cool.

Thermopolymers can reach temperatures of over 200 degrees during thermoforming and it's important to wear PPE, including things such as heat-protective gloves.

Another quick question for you then.

Please complete this sentence.

Thermopolymers can.

A, be heated and formed repeatedly.

B, be melted and formed.

C, be heated and formed once.

Or D, be melted and shaped.

Pause the video here just to take a moment to think about your answer.

And the correct answer? It was A, so thermopolymers can be heated and formed repeatedly.

Let's look at another method for heating thermopolymers.

Here's an example of a strip heater.

Strip heaters are used to heat up a strip or line across a piece of polymer.

This is then held in a vice or a former to cool in the desired shape, so it'll usually create some sort of fold in the polymer.

Just like before, this is going to heat the thermopolymer up to a high temperature, so appropriate PPE and also things like heat-protective gloves would be needed.

Here's a diagram of this process.

Now, in this example, the person is not wearing heat-protective gloves, but we're just showing you this to give you the example of how this works.

The orange line is the heated wire, and this is basically the strip as such.

The polymer is held over it and then it is bent or moved into the desired shape once it is heated up enough to be malleable.

Now, bending jigs and formers hold the heated polymer in shape while it cools, helping to create identical angles for multiple products.

So here you can see some examples of test tube holders that have been made using a strip heater.

They've been made using then a former to hold these in place to cool at that exact angle.

Here are a variety of bending jigs and formers.

Here's another example of a heating method for thermopolymers.

This is a vacuum former.

Now, vacuum formers are used to heat sheets of polymer which are forced over a mold.

A vacuum removes air from the chamber under the polymer, which causes the atmospheric pressure above to force the polymer over the mold.

In schools, we usually use high-impact polystyrene sheet, but in industry large vacuum formers can use a range of polymers.

So let's look at a diagram of the process of a vacuum former.

Firstly, a former is placed on the bottom of the vacuum former.

Then, a polymer sheet is heated.

The polymer sheet becomes flexible through the heat being applied, and the former is then moved up into the polymer sheet.

At the exact same time, air is sucked out and down.

That then pulls the polymer sheet over the former at a really tight fit.

Once it's cooled, you then have your hollow product.

Quick check for understanding then.

Add the missing thermoforming equipment names to each description.

Blank are used to heat sheets of polymer which are forced over a mold.

Blank are used to heat up a strip or line across a piece of polymer.

This is then held in a vice or former to cool in the desired shape.

And blank are versatile as they can heat up different shapes, sizes, and types of polymer.

Pause the video here to fill in the missing words.

Let's have a look at those missing words then.

So the first one was vacuum formers.

Vacuum formers are used to heat sheets of polymer which are forced over a mold.

Strip heaters are used to heat up a strip or line across a piece of polymer.

This is then held in a vice or former to cool in the desired shape.

And lastly, thermoforming ovens are versatile as they can heat up different shapes, sizes, and types of polymer.

Well done if you got all of those right.

Let's have a look at an example of thermoforming process.

Now, Alex has cut some hooks from acrylic on the laser cutter.

You can see that in the diagram.

That's a double hook design that's cut and engraved on the laser cutter.

He now needs to heat and form them.

He plans to use the strip heater and he's already engraved the fold lines so he knows where to strip heat.

Before he heats them, he must plan how to hold the acrylic whilst it cools.

We'll come back to this example in a moment.

It's gonna be up to you now to have a go at some tasks.

The first thing I'd like you to do is describe the difference between a thermopolymer and a thermosetting polymer.

Include specific examples in your answer.

I'd then like you to consider your design and explain which aspect you could manufacture using the thermoforming technique.

I'd also like you to explain how you would ensure the quality of your thermoformed polymer part.

And lastly, explain the health and safety measures that you will take.

Right, pause the video here to have a go at these four tasks and good luck.

Right, let's look at some example answers.

The first thing I asked you to do then was describe the difference between a thermopolymer and a thermosetting polymer.

Include specific examples in your answer.

So in this example answer then, it says, "Thermopolymers, such as acrylic, HIPS, and polypropylene, can be heated, formed, reheated, and reformed repeatedly.

Thermosetting polymers can only be formed once and then they are set.

Examples include epoxy resin and urea formaldehyde." If you ever struggle to remember these, remember, thermosetting, they are set.

So once they've been heated and formed, they are set, can only do it once.

So the clue is in the name there, thermosetting.

The second thing I asked you to do then was to consider your design and explain which aspect you could manufacture using a thermoforming technique.

I showed you before Alex's design that he had laser cut, and he was trying to work out then how he could form the shape.

He just explains here, "I've designed and laser cut different hook designs for my kitchen storage unit from sheet acrylic.

They are 2D and need to be shaped using a strip heater to create the 3D shape.

The red lines are engraved and I will use these to ensure the strip heater is heating the correct part." Your answer will naturally be different to Alex's depending on your design, but just check you've included enough detail in your answer.

The next thing I asked you to do was to explain how you would ensure the quality of your thermoformed polymer part.

Again, I'm going to use Alex's as an example here.

"Once the polymer is heated along the strip, I will shape the polymer around a former.

I've created a former from a piece of timber, which I'll hold in a vice." If you remember, we looked at formers and bending jigs to help to actually shape the polymer whilst it's cooling.

Have you thought about something similar there in your answer? And lastly, I asked you to explain the health and safety measures that you will take.

So, example from Alex here, "When shaping the heated polymer around the former, I will wear heat-resistant gloves." Have you remembered to include that PPE of those heat-resistant gloves in your answer? So next, we're going to look at joining.

The manufacturing processes where materials are joined are called fabrication.

There are two methods of fabrication.

Adhesives, which is when you are joining using a sticky substance.

Or mechanical fixings, which is joining using components.

Now, when designing products, designers must make decisions about the most suitable method, and this is dependent on the materials being joined and the shape of the join.

It also considers the intended function of the product as well.

Let's look at adhesives first then.

Now, polyvinyl acetate, or PVA, is water-based and works well with absorbent materials such as timbers, papers, and boards.

Here's an example of PVA glue, which I'm sure you're very familiar with.

Glue guns use hot liquid glue to join materials such as polymers and timbers.

Now, this is suitable for modeling and prototyping as the glue is brittle when cool and therefore not very durable.

Here's an example of a glue gun again that you might be familiar with from the classroom.

Okay, quick check for understanding on those adhesives then.

Which materials can be joined well with PVA glue? A, polymers; B, papers; C, metals; or D, timbers.

Pause the video here just to take a moment to think about your answer.

And the correct answer? There were two possible options here.

So PVA works really well with papers and timbers, anything that the PVA can be absorbed into it.

So more examples of adhesives then.

Tensol cement produces a chemical weld when used on acrylic, and you can see an example of tensol cement in the image.

Now, tensol cement can irritate the skin and the fumes can be harmful, so it must be stored in a locked metal cabinet and used in quite an open and airy room or a well-ventilated room.

Epoxy glue is two liquids which have a chemical reaction when they are mixed together, so they will usually come in two separate tubes.

Hopefully you can just about see that in the image.

Now, this creates a strong and durable adhesive, which works well on polymers, metals, and many other materials.

Now, adhesives are liquid and need to set in order to be effective.

This process is called curing.

The curing time for each adhesive is different.

So, for example, PVA glue cures in 24 hours, but a glue gun glue cures in a few minutes.

Now, manufacturers may speed up the curing time using heat or UV light.

Tapes with adhesive attached can also be used.

These usually do not need time to cure and create an instant join, and here's an example that's some double-sided sticky tape.

Right, another question for you here then.

What are the advantages of using a tape over a liquid adhesive? A, there's an instant join.

B, it takes 24 hours to cure.

C, it takes a few minutes to cure.

Or D, quicker.

Pause the video here just to take a moment to think about your answer.

And the correct answer? There were two possible ones here.

A, it creates an instant join, and D, is also quicker to use tape over a liquid adhesive.

Let's look now at mechanical fixings as opposed to adhesives.

So mechanical fixings, just to remind you, are components which are used to join materials.

Now, some use deformation such as rivets or staples, and this means they change shape due to the forces acting upon them.

Other mechanical fixings use friction, which is a force that resists motion when two surfaces come into contact with another.

Now, examples of these include things like screws, nuts, and bolts, as shown in the image there.

Screws are suitable for joining different materials to timbers.

They have spiral ridges called the thread, and the thread presses against the timber where friction occurs to create a strong join.

Here's an example of some screws in timber.

Now, bolts also have spiral threads, but the friction is between the bolt thread and the thread inside the nut, so these work slightly differently.

Right, another quick check for understanding then.

Which mechanical fixings use friction? A, screws; B, staples; C, rivets; D, nuts and bolts.

Pause the video here just to take a moment to think about your answer.

And the correct answer? Screws and also nuts and bolts use friction.

Now, this table summarizes different joining methods.

So on the left-hand column you have the joining method.

You've got in the list here you've got PVA, epoxy glue, tensol cement, screws, rivets, nuts and bolts.

You've then got the material that these are typically used with.

And lastly then, you have the features of that material.

If I just give you an example of two of these, epoxy glue, for example, is used with metals and polymers.

The feature of epoxy glue is its waterproof, but must be mixed immediately before use.

If you remember, it comes in those two separate tubes.

If I then give you the example of screws, they are typically used with timber and they are suitable for solid timbers only.

So let's look at an example of Alex's work.

Alex's kitchen storage unit design has several parts which are to be slotted together.

He must consider how to add the hooks to his design.

And you can see in the image the examples of Alex's CAD design and Alex's modified CAD design.

Alex just explains, "The main body of the design is made from PLA.

The hooks are made from acrylic.

Mechanical fixings such as a nut and bolt will be suitable.

I need to add holes to the CAD design before 3D printing the model." And you can see he's done this in his modified CAD design.

There's holes at the front.

Okay, it's gonna be up to you now to have a go at a few more tasks.

The first thing I'd like you to do then is to answer this question.

What is an adhesive, and which type would be most suitable for joining two pieces of timber? I'd like you to explain your choice.

The next question then.

What is a mechanical fixing, and which type would be most suitable for joining two pieces of sheet aluminum? Again, please justify your selection.

Next, I'd like you to identify the different parts of your design that require joining.

Explain and justify the joining methods you plan to use for each.

And lastly, I'd then like you to manufacture your design using the selected joining methods.

Once completed, then evaluate the effectiveness of your approach.

Okay, quite a few tasks here, and some of them are a little bit more time-consuming than others, so pause the video here to have a go at these tasks and good luck.

All right, how did you get on with all of that? The first thing I asked you to do was to answer this question.

What is an adhesive, and which type would be most suitable for joining two pieces of timber? I wanted you to explain your answer.

So, an adhesive is a sticky substance used to join materials together.

PVA glue is the most suitable for joining two pieces of timber together because timber is absorbent and PVA is water-based, which works well on absorbent materials.

The second question then was, what is mechanical fixing and which type would be most suitable for joining two pieces of sheet aluminum? And I wanted you to justify your selection.

Mechanical fixings are components which join materials.

To join sheet aluminum, a rivet or a nut and bolt can be used.

A rivet would be permanent, and a nut and bolt could be used temporarily or permanently.

Just compare your answers to the examples here and check you've got all of those key points.

The next thing I asked you to do was a more personal answer, looking at your own design.

I asked you to identify the different parts of your design that require joining, explaining and justifying the joining methods you plan to use for each one.

Let's look at Alex's example considering his CAD design that I showed you before.

"The main body of my design is made from 3D-printed PLA.

The hooks are made from laser-cut acrylic.

I thought about using adhesives, but joining two polymers would be very difficult.

I think a nut and bolt will be the most suitable fixing method as this relies on the friction between the nut and bolt.

This would offer a secure join, which would be good under tension when the utensils hang on the hooks." Just check your answer over.

Have you identified the different parts that require joining? And then justify the joining methods that you plan to use for each so you've explained them appropriately.

And the last thing I asked you to do then was to manufacture design using the selected joining methods.

Once completed, I then asked you to evaluate the effectiveness of your approach.

Let's look at Alex's evaluation.

"I modified my CAD design and 3D printed the unit with the holes.

I was then able to line up the holes on the acrylic hooks and push the bolt through from the front.

The nut is hidden inside the unit.

It was quite fiddly to hold and to tighten.

I used some long nose pliers, as my fingers didn't fit.

The join, however, is very strong and will hold utensils well." Check your manufacture and check that you've evaluated the effectiveness of the approach that you chose.

Right, let's summarize today's lesson then.

Today we've been looking at specialist techniques and processes for manufacture.

Now, tools and equipment are used to create products, and thermoforming processes can be used to deform and shape polymers.

The manufacturing processes where materials are joined are called fabrication, and the two methods of fabrication are adhesives or mechanical fixings.

Now, deciding which fabrication technique to use depends on the materials, shape, and function of the product.

Thank you so much for all of your hard work today and thank you for joining me for the lesson.

I will see you soon.