3D modelling and CAD as documentation basis

Today the 2D drawing is often a result of a 3D model not the starting point. As a technical designer you work in CAD programs where you build a model from which drawings lists and visualizations are extracted. This means the quality of your model determines the quality of everything that comes out of it.

Parametric modelling means that the geometry is controlled by parameters and relationships instead of fixed, entered points. If you change one value — for example a plate thickness or a height — the model updates itself and derived drawings follow. This makes changes fast and reduces the risk of one drawing contradicting another.

• 01Sketches are bound with geometric and dimensional constraints.
• 02Features are built on top of each other in a logical, editable tree.
• 03Naming and structure must be understandable to others than yourself.
• 04Avoid over-constrained sketches that make the model brittle and difficult to change.

In construction increasingly BIM is used where the model not only describes geometry but also contains information about materials components and properties. A wall is not just three surfaces but an object that knows it is a wall with a specific structure. This provides the ability to extract quantities collision checks and analyses directly from the model.

Regardless of whether you work in 2D or 3D, discipline around layers, naming and folder structure is crucial. A colleague — or yourself in six months — should be able to open the file and understand what belongs together. Agreed naming standards and layer structures are often specified in the project's CAD manual or IKT agreement.

From one good model you can produce several types of deliverables that always match because they come from the same source.

A model is only valuable if it's correct and can be reused. Clean up unnecessary geometry keep file size down and document the assumptions you've built in. Good data quality means the model can live on in later phases — from planning through operation and maintenance.