Key Stage 2 design and technology · Design

KS2 prototypes, pattern pieces and CAD: a guide for parents

In Key Stage 2, children learn to model an idea before they make the final product. They build a quick prototype from cheap materials, make pattern pieces so that parts are cut to the right size and shape, and may use computer-aided design to draw and adjust a design on screen. Modelling lets them find problems early, when changing the design is cheap and easy.

Prototypes, patterns and CAD, explained

The programme of study says that pupils should be taught to generate, develop, model and communicate their ideas through discussion, annotated sketches, cross-sectional and exploded diagrams, prototypes, pattern pieces and computer-aided design. This guide covers the modelling part: prototypes, pattern pieces and computer-aided design, often shortened to CAD. The drawn forms are covered in the companion guide on sketches and diagrams.

A prototype is a first version made to test an idea. It is usually built from cheap materials such as paper, thin card, scrap fabric or modelling clay, because the point is to learn from it, not to keep it. Children use prototypes to check that the size is right, that the parts fit and that the idea works, and they test them against the design criteria that came from their research into the user. Sometimes a prototype models only one part, such as a fastening. Finding a problem at this stage is a success, and a prototype that “fails” has done its job. Several rounds of prototype and improvement are normal, which is the iterative process the curriculum describes.

Pattern pieces are templates for the shapes that make up a product. In textiles, each piece of fabric is cut around a paper pattern so that the pieces match. A pattern often includes a seam allowance, which is the extra edge beyond the finished size that is taken up by stitching. Patterns are also used in other materials, for example the flat shape, called a net, that folds up into a box. A good pattern piece is labelled with its name, how many to cut and the seam allowance.

Computer-aided design means using software to draw or model a design on a screen. The advantages are accuracy, because measurements can be typed in, and flexibility, because shapes can be resized, copied, rotated and undone with no mess. Primary schools use CAD in different ways, from simple two-dimensional drawing of a shape or pattern to basic three-dimensional modelling, and some schools have limited access to it. Which software a school uses is its own choice. Some schools go on to send a design to a cutting machine, but that is not required at this stage.

These forms of modelling work together. A child might draw a pattern on screen, print it full size, make a quick prototype, test it, change the measurements and print again. At the end, they compare the product with the design criteria they wrote at the start.

Words your child will hear

Prototype: A first version of a product, made to test whether the idea and the size work.
Mock-up: A model, often a rough one, that shows what a design will look like.
Pattern piece: A paper or card shape used as a guide for cutting material to the right size and shape.
Seam allowance: The extra edge left outside the finished size, so there is room to stitch pieces together.
Template: A shape you can draw around again and again to get identical pieces.
Net: A flat shape that can be folded up to make a 3D shape such as a box.
Computer-aided design: Using a computer to draw, change and test designs. It is often called CAD.

What the National Curriculum says

The programme of study for Key Stage 2 says:

When designing and making, pupils should be taught to generate, develop, model and communicate their ideas through discussion, annotated sketches, cross-sectional and exploded diagrams, prototypes, pattern pieces and computer-aided design
When designing and making, pupils should be taught to use research and develop design criteria to inform the design of innovative, functional, appealing products that are fit for purpose, aimed at particular individuals or groups

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

Try it: a pattern piece for a bean bag

A child wants to make a square bean bag for a Year 1 child to throw and catch. It is made from two squares of fabric sewn together with a 1 cm seam allowance, with a small gap for filling. The first plan is for a bean bag 10 cm across when finished. How big should each pattern piece be, and how do a prototype and CAD help?

Work out the pattern piece. The stitching sits 1 cm in from each edge, so the fabric needs an extra 1 cm on both sides of the finished width.
```
10 + 1 + 1 = 12 cm
Pattern: 12 cm by 12 cm square
```
Make a prototype. Cut two 12 cm squares of scrap fabric using the paper pattern, stitch or pin them together, fill through the gap with a handful of dried rice, and close the gap.
Test it with the user. A Year 1 child tries to throw and catch it. It feels too small and slips through their fingers. The prototype has shown a problem that would have wasted good fabric.
Change the design. The finished size becomes 12 cm, so the pattern piece must grow too. Add the seam allowance again.
```
12 + 1 + 1 = 14 cm
Pattern: 14 cm by 14 cm square
```
Use CAD to help. Draw a square on screen, type 14 cm for the sides, copy it to make the second piece and print at full size. Check the printed square with a ruler, as printer settings can shrink a design to fit the page. Label the pattern: “Bean bag, cut 2, seam 1 cm”.

For a 10 cm bean bag, each pattern piece was 12 cm by 12 cm. After testing the prototype, the finished size was increased from 10 cm to 12 cm, so each pattern piece became 14 cm by 14 cm (12 cm plus 1 cm of seam allowance on each side), cut twice.

Common mistakes and how to help

Making the pattern piece the same size as the finished product

Children focus on the size they want and forget that stitching and folding use up some of the material.

What helps: Sew a scrap together and measure it. The finished piece is always smaller than the cut piece. Then add the seam allowance to each edge in the plan.

Treating the prototype as a waste of time or as the final product

Children want to get on with the real thing, or they try to make the prototype perfect.

What helps: Say that the prototype is for learning. Ask, “What did it show us?” and keep it rough. Cheap materials, such as scrap paper, remove the worry about wasting something good.

Thinking a prototype that goes wrong means the design has failed

Children are used to being marked on whether the work is right, not on what they learned from it.

What helps: Explain that designers expect prototypes to show problems, which is why they make them. A problem found now is a problem fixed before the final version.

Believing that CAD does the designing for you

Software looks clever and produces tidy results, so it seems that the computer is making the decisions.

What helps: CAD draws only what you tell it to. The designer still decides the sizes and the shapes. Print a design at full size, and check it against the real measurement.

How to help at home

Prototype before the real thing. Before building anything from good materials, make a quick version from scrap paper or card. Test it, then change one thing and test again.
Draw around a template. Make a paper shape such as a bookmark or a pocket, then trace it several times so that every copy matches. This is how pattern pieces work.
Open out a box. With an adult’s help, carefully pull open a cereal box along its glued edge and lay it flat. Your child can see the net and then work out how it folds back up.
Draw on a screen. If you have a drawing program on a home computer, let your child draw a shape, change its size by typing numbers, and copy it. Print it and measure it with a ruler to check.
Paper aeroplane improvements. Fold a paper aeroplane, fly it, and change one thing at a time, such as the wing size or the nose. It is a safe way to practise testing and improving.

Builds on

Key Stage 1: Design criteria and users
Key Stage 1: Drawings, templates and mock-ups

Leads on to

Key Stage 3: Understanding user needs
Key Stage 3: Identifying design problems
Key Stage 3: Writing a design specification
Key Stage 3: Biomimicry and user-centred design
Key Stage 3: Communicating design ideas