Accuracy

• Far more accurate than traditional hand-drawings. CAD software has in-built tools which are incredibly accurate and are able to work in microns (0.001mm) or even smaller. 

Detail

• It is possible to create incredibly detailed designs using CAD systems that would never be achievable by hand, no matter how skilled a sketcher a person is. 

Saving and Sharing

• It is possible to save the work and share it with others working in teams around the world. This means that organisations can be more productive and are not limited by geography or time constraints. 

Scalability

• CAD models can be very quickly scaled-up or scaled-down in order to make an object integrate (fit) another. This would take potentially many, many hours and require completely redrawing if doing this by-hand. 

Importing

• CAD models can be shared between colleagues and can be imported into other, existing models. Working in this way means that individuals can work on separate components (elements) of a design, breaking a job down into smaller, more manageable pieces. When a component is finished it can then be imported into a parent assembly, i.e. the finished, whole design. 

• There are many file sharing sites that exist such as www.grabcad.com which allow users to download CAD models created by their user-base. This means that a designer can concentrate on creating what is new and what is needed to be designed and not have to waste time on less important elements that can just be copied from other sources. 

Output to CAM

• CAD models can be sent directly to the machinery intended to manufacture a particular object. CAM, Computer Aided Manufacture is the name given to any automated making system which uses mathematical data generated by the original CAD model to ensure an accurate 1 to 1 version of the original design. These systems include CNC (computer numerically controlled) lathes, milling machines, laser cutters, engravers or 3D printers. 

Expensive

• CAD software is often quite expensive to purchase and often requires subscription services (that is, a continuing monthly or annual payment) to access more advanced yet critical features of the software.  A good 2H pencil and a sheet of A4 is comparatively much, much less expensive! (but clearly less capable).

Requires training

• In order to use CAD software it is necessary to be trained to do so. Whether designing in 2D or 3D there is a particular skill to thinking and working in that way. Also whilst there are usually more than one way to draw something in CAD, when you are being paid to stick to a schedule some 'workflows' are more effective than others. This needs to be learnt. 

• Whilst an experienced user of one piece of software is usually able to transition over to another, rival program relatively quickly there is often a 'learning curve' associated with 'getting to grips' with CAD programs. 

Mistakes

• Humans are able to make mistakes. This is true when using CAD too. There are examples of design failures which were created using CAD, however at the root of these mistakes were human beings. 

• Remember the 'A' in CAD stands for aided (helped, assisted). That means that they still need to be 'driven' by humans.

Hardware and software failure

• Whilst rare, it is possible for computers to fail and software to 'crash' leading to all the digitally stored worked being lost or irretrievable. For this reason it is very important to keep digital back-ups of the work so that project time and money is not lost in the event of hardware or software failure. 

Always on internet connection

• Another more recent 'problem' is that some CAD applications (programs) require an always on internet connection. In some rural countries or geographical areas this is not possible. If the software is reliant on a 'patchy' connection this could lead to losing work. 

Some advantages of CAM are:

• Greater design freedom, as changes can be incorporated easily at any stage

• Increased productivity, as machines can run constantly and accurately on repetitive tasks

• Good for mass or flow production, as the same design can be replicated many times

• Less material wastage, as the machines are precise and efficient

The disadvantages of CAM are:

• It requires a high initial investment and start-up cost.

• Machine maintenance is expensive.

• A skilled manual workforce may be lost.

• Highly trained operatives and technicians are needed.

• Technology failure may cause breakdowns and delays.