1.7.1 CAD systems & FEA

Introduction

Computer aided design (CAD) has been around for many decades but, in the last few decades, has become one of the key methods of developing and manufacturing products both in schools and colleges as well as industry.

Advances in Computer Aided Manufacture (CAM) has allowed for the models and components created in CAD to be quickly manufactured using computer numerical control (CNC) and CAM machinery.

Computer Aided design (cad)

The main advantages of using CAD:

CAD speeds up the product design development process
CAD makes it easier for teams to collaborate and develop ideas even when in different locations across the globe
CAD drawings and models can be shared digitally
CAD models take up no real space unlike physical models
aesthetic properties can be changed without destroying the original model
numerous variations can be produced in a short space of time
CAD models can be send to CAM and to RPT machinery for quick realisation of ideas

The main disadvantages of using CAD:

software can be expensive to buy (although much is free for schools and colleges)
staff need to be trained in the use of software which can be quite complex
software needs updating regularly to keep it from bugs and to enhance its features
CAD software is not always easy for quick ideas, but some people can use it faster than drawing!
CAD is still dependent on user input so faults can occur due to human error

The use of CAD to develop and present ideas for products

Modern CAD is so advanced that it can create 3D models and render them to be indistinguishable from real objects. This level of visualisation allows designers and clients to envision what the final product could look like and make changes to shape, colour and finish quickly with almost instant results. The results can be indistinguishable from a photograph.

2D CAD

CAD can range from 2D drawing packages such as Adobe Illustrator and Techsoft 2D Design to complex 3D surface modelling packages.
2D packages are generally used with laser cutters and plotters to cut out shapes from sheet materials.

Onshape working drawing

Adobe Illustrator

3D CAD

More complex than 2D CAD, this is software that can produce full 3D models and assemblies. These can be well suited to younger students in programs such as Tinker CAD and Onshape. Professional packages like AutoCAD, Fusion 360 and SketchUp are free to use in schools but, like Solidworks, are expensive to buy for industrial use.

If you have a 3D CAD model, working drawings can be quickly produced, dimensioned and annotated.

Software can be used to tesselate lots of parts into the most cost-effective solutions to manufacture using standard size materialsand cutting tools can be set up to automatically cut, drill and router parts using CNC.

Virtual Reality (VR)

Virtual reality is an immersive process which was popular in the 1980’s but computer visualization technology was crude at the time and made the experience impractical, infuriating and sometimes nauseating as the user was immersed in a 3D world viewed through a headset.

It has been dormant for several decades but the advances in technology now mean that users can experience visuals that are lag free and almost photorealistic. It is very popular at the moment for recreation but is also becoming an essential tool for designers and engineers.

tilt brush by google

Augmented reality (AR)

is an non-immersive process which as been around for many years, but the technology was not able to support it effectively. It has recently gained popularity for its implementation in smartphones and tablets such as the iPad. This process places information, graphics and 3D models over an existing display by using the device’s camera and some clever software. The possibilities for such technologies range from seeing how your room will look painted in different colours to road maps on car screens and doctors being able to see a virtual x-ray of your body through special glasses. Even Apple are working on the technology for their glasses.

Computational fluid dynamics (CFD)

CFD is a tool available in most professional packages and is used to simulate the flow of fluids or gases in or around a product. It is invaluable in improving the efficiency of fans, turbines and other elements which require efficient flow. It would have been used to develop products like the Dyson fans and hairdryers.

Finite element analysis (FEA)

FEA takes scientific information about the mechanical properties of the material being used in a structure and calculates the forces that will be applied to the structure. The resulting visual data shows where the stresses and loads will be and highlights potential problems which the designer or engineer can then address. The product can then be re-engineered to reduce potential problems. Generative design is a new advance in the area of FEA.

Generative design

A relatively recent advance in CAD, generative design (or topology) is software which goes beyond FEA and analyses the geometry of a component. It then generates almost infinite variations of that product that reduce materials/weight while increasing physical properties such as strength. The designer can then choose the variation with the right combination of visual appeal and technical performance to develop or engineer towards a solution.

Honda recently used generative design to develop a crankshaft that is 50% lighter than previous crankshaft components while still retaining the necessary strength and performance. By using this process across the range of car components, considerable savings could be made in terms of power consumption.

Computer aided manufacture (CAM)

CAM usually involves downloading completed CAD drawings to machines that will cut and shape materials. Most CAM machines take the drawing and convert it into a computer numerical controlled (CNC) program which is translated into movement in 2 or 3 axis by the cutting or shaping tool.

Most modern tools and machines can have a CNC version.

Laser cutting

Laser cutting uses a high energy laser beam to cut or vaporise materials and compressed gas or air to blow away the waste material. It is capable of cutting and engraving incredibly small and detailed parts in a wide range of materials including plastic, stone, glass, metal, wood, fabric and more.

They are commonly used in schools and industry but they can only cut in 2 axis with depth dependent on the power of the laser, but they cannot create organic 3D shapes.

Routing/Milling

Routing / milling are essentially the same process as they involve a cutting or shaping tool which moves in 3 axis. The difference is in the torque/power of the cutter and the materials being worked on. Milling is used for harder materials and therefore the cutter requires more torque. A 5 or 6 axis milling machine has a cutting head that can move in all directions around the material.

These machines can be small enough to fit on a table or so large they fill a whole factory floor!

Turning

Turning involves rotating the material to be shaped between two fixed end points (on a lathe) then introducing a cutting tool or profile to shape the product. Industrial lathes may form part of a flexible manufacturing system (FMS) together with milling machines and laser cutters which may be loaded by robot arms which transfer the parts between machines. They can shape parts very quickly but like most CNC machines, are expensive.

Plotter cutting

Plotter cutting works like a printer but, instead of using print heads to print pictures, they have a small blade that cuts through the material being fed into the plotter.

A Vinyl cutter is a common machine to find in a school classroom or workshop and can cut out plastic and paper/card.