CAD modelling is, truly, my favourite part of the design process.

It is so satisfying to go from a few basic sketches to a digitally defined design that can be realised as an actual physical object. I still get a little kick every time I take a first prototype off the printer first thing in the morning after an all-night print – it reminds of hauling in the fishing nets at 6am, eager to see what you’ve got…

CAD modelling can be done using surfaces or solids. When you fly a plane on Flight Sim, that model is all surfaces – there’s no point in wasting data defining the bits you can’t see – but a CAD model for printing obviously needs that information.

Say I start with a circle:

I can now ‘extrude’ that circle to make a tubular surface:

And now I can tell the software to thicken the surface – at this stage it has become solid object.

Now let’s draw a shape on the plane running down the middle of that tube;

…and now I’ll extrude that. Here I’m not thickening a surface, just extruding it straight up as a solid.

I’ll just mirror that on the other side. Look Mum, I made a plane!

OK, so there’s a bit more to it than that, and the ways you do the details depend on what functions your software provides. Every package will have a bunch of buttons which do various things by applying some hard maths to the data you have provided.

Maybe revolving a 2d drawing to make a round solid;

Or maybe joining two dissimilar shapes (usually called lofting);

Ultimately you are using digital tools to make an idea real.

And just like the old fashioned way, sometimes those tools get it right first time, and sometimes they turn out not to work and you use a different tool. It is trial and error at first – and even with experience, any new design can bring a new challenge – but it gets pretty quick after a while.

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