There are many aspects to design, but what is meant here is the process of developing ideas as solutions to problems using real materials and components.

CAD software can be seen as another tool for rapid modelling of ideas in 2D or 3D, in conjunction with sketching or a range of rapid construction methods with cardboard, plastics, Plasticine, kit materials etc. Rapid only in the sense that changes can easily be made and visualised; rather slow if you don't know the software particularly well! Students need some introduction to CAD and this is often done using a number of step-by-step tutorials. The problem with following detailed tutorials is that the student doesn't really know why they are being asked to do certain actions. At an early stage it is a great advantage to get students to develop strategies for shape creation and modification, so that they know how to change things if they are not quite sure what they want.

One problem with CAD/CAM is that the outputs on-screen, printed or manufactured are of such quality that it's easy to become precious about them and forget that they are a development tool. Encourage your students to draw on, paint, carve and add to CAD/CAM products, so that the product is improved.

SpeedStep, the textiles design software, has a design flow built in. Starting with technical sketches created by scanning, drawing, tracing or from a library of shapes, it progresses naturally into consideration of fabric colours, textures and patterns. Then it allows the visualisation of designed fabrics on photographic images so that evaluation can take place before transferring the design to real fabrics by digital printing.

ArtCAM also has a well-defined workflow from 2D graphics to the 3D relief that is then sent to the CNC machine for manufacture. It is particularly well suited to making signs, relief panels, moulds, jewellery and heraldry. The design emphasis is in the evaluation of the 3D relief and its suitability but it also allows the rapid exploration and development of alternatives.

Pro/DESKTOP is by definition 3D solid modelling software and so is useful for visualising any product that is made or assembled from rigid materials. There is no obvious work flow; so how does it support designing? The first benefit is to enable easy and rapid changes to design ideas:

• These ideas could be Pro/DESKTOP parts that others have created and students are asked to modify. The essential question to ask is "what if" the part was a different shape or size, the part was assembled in a different way, or it was made from a different material, etc. (The SCAMPER strategy is useful here)
• The Palette function in Pro/DESKTOP has the advantage of presenting a kit of ready-designed 3D shapes. The students just add imagination.
• There is also designing to be done with mechanical assemblies which are amenable to CAD modelling. For example, a simple linkage or mechanism can be assembled with suitable constraints and animated with the mouse to check clearance and extent of movement. Very little capability is required with Pro/DESKTOP if 'flat' components are being used, and these can be transferred to CNC to be cut as profiles relatively quickly.

Another benefit is being able to portray design intentions. Without the limitations of drawing skill, products can be visualised in 3D. However, this does need some planning based on the knowledge of how a range of similar objects was created. This may entail some discussion of the symmetry and similarity of solids, and the range of possible strategies for construction. For example, cylindrical shapes can be created by extrusion of a set of circles or by revolving a profile. The best approach often depends on which dimension or part of the solid needs to be changed when re-designing.

What sort of messages do your students get from the use of CAD/CAM?

We must make sure that our students experience the real benefits of CAD/CAM, and that they don't spend their time doing too many tutorials in order to master the software, but that their designing and making capability is supported and enhanced.

The key benefits of CAD/CAM are: accuracy, ease of modification, repeatability and quality of output.