Computer Aided Design vs Building Information Modeling
Currently, the development of the BIM system is acquiring so much power that in many cases it becomes a requirement in current Engineering and Building projects, however, CAD continues to dominate the stage, we are in a moment of transition, where the coexistence of both systems and especially their coordination is especially important.
Aware of their predecessors, all BIM programs allow you to import CAD originated files directly or as references. Although this apparently means its easy and immediate incorporation, it is only in part, since all the information it contains cannot be read as BIM, that is, we will have an inserted plan that we can work with but its edition will be limited to aspects size, location, display and style.
Therefore, starting a BIM project with a CAD base is very helpful, the current market has a higher percentage of CAD professionals, if we add that BIM programs like REVIT allow a good association with the CAD model, it allows us to take advantage of the speed and integration of CAD in the professional world with the capacity and future of BIM.
Hardly, in the short and medium term, the CAD system disappears completely and is completely replaced by BIM since the second can integrate the first, it does not necessarily have to eliminate it.
Its diffusion and use in the generations of professionals since its appearance and implementation in the 90s, will keep it in force for a long time. But also because its own characteristics and utilities make it in some aspects more useful than the BIM system.
Defining concepts will help us better understand the good relationship between the two systems:
In order to better understand the relationship between the two, we will have to introduce a new term of the BIM methodology, the so-called BIM dimensions that are linked to the type of information that the model has.
CAD allows us a 2D / 3D representation of reality, with this level of model information we could find ourselves in the first dimensions 0 and 1 of the BIM, where we would basically be dealing with the information generated from the first sketches of the project to a the graphic definition of the project.
BIM is a virtual model, a digital construction of an active object. It is then when a program is needed that can contain the information that we need to reach the different dimensions, in each dimension that we add the model will gain information typologies:
- 0D BIM would be the first digital traces of the project in a conceptual way, volumes, general spaces, project lines, …
- 1D BIM we would begin to digitally detail the model, we would begin to size the main axes of the project, definition of volumes, project program, pre-dimensions …
- 2D BIM would involve beginning to develop detailed information from project information in a collaborative 3D environment with joint graphical data, but in separate discipline models.
- 3D BIM is surely the BIM concept that we know best, where the process of creating non-graphical information begins, which is added to the graph and all this information is shared in a common data environment. It is at this time that as the project progresses, this graphical / non-graphical information is further detailed to the point that all data will be delivered to the client when the project ends.
- 4D BIM is the so-called construction sequencing adding an additional dimension of information in the form of data programming. This information can be used to make schedules, planning and visualizations of how the project will develop sequentially. When Time appears, it will allow us a safe, logical and effective planning.
- 5D BIM we rely on the components of the information model to be able to extract cost information. This information makes it easy to extrapolate the quantities of a component and achieve a global cost for development. As the data can be consulted at any time, this allows anticipating possible contradictory prices and better controlling the different stages of the project.
- 6D BIM or project life cycle information. We build an information model with the intention that once it is built it will continue to be developed, incorporating endless operational data and diagnoses of all the components of the project, anticipating the deterioration and / or malfunctioning of the parts, planning some revisions and corrective measures that prevent a malfunction of the element.
Another point to keep in mind in order to better understand the BIM methodology is the so-called Level of Development (LOD), which defines the level of development of the information that an element, construction system, project has …
- LOD 100 – Concept Design. This is the 3D model under construction to represent the information at a basic level through volumes, areas, heights, location and orientation.
- LOD 200 – Schematic Design. We would start to measure “roughly” the shapes represented in LOD 100 and we could start adding “non-graphical” information to the model.
- LOD 300 – Detailed Design. We define the project elements specifically with the precise quantity, size, shape, location and orientation. At the same time we will add all the “non-graphic” information that can be detailed.
- LOD 350 – Construction Documentation. It details the model and all its elements as construction elements with graphics and written definitions, which will help us define its interconnections between systems.
- LOD 400 – Fabrication & Assembly. The elements are modeled as specific sets with all the detailed information, since all the interferences have been resolved in the previous sections. The elements can now be configured with all the desired “non-graphic” information.
- LOD 500 – As-built. The elements are already modeled as assemblies built with all the definitive information for their maintenance and operations. At this point, the model will be nourished by the user of the project’s exploitation, where he can add, supervise and modify information according to the actions that are applied.
Our LOD models will allow us to better control the project in its design, construction and operation phase.
All this information from the different LODs would have an automatic synchronization creating the so-called BIM system.
This synchronization is almost impossible if we do not have programs already devised to carry out this systematic coordination of information. So we are no longer talking about “drawing” but “modeling”.
It must be considered that BIM is a system and a methodology that is born with a multiplatform mentality and the main power is the integration and coordination of information. So it is clear that there is no reason to think that you should use one thing or the other, but that BIM is perfectly compatible with CAD.
The BIM system is an integrating system.
When a project has to be coordinated with external teams, if they do not work in BIM methodology, we can share information that is perfectly adaptable to the systems they use, using the import and export tools. Going one step further, if we use links properly, these files are automatically updated.
If we model the drawings, diagrams, details, … in CAD, having less information makes the files easier to use than a BIM model, they occupy less and are therefore easier to handle.
It is becoming easier to link CAD software with BIM software, although it must be recognized that BIM programs are becoming more self-sufficient and include more tools. However, there will always be more powerful specific programs in your field, what matters then is being able to coordinate and synchronize the information.
To ensure that the information has good coordination and synchronization, we must have our own protocols and storage service, either physically with servers or through the cloud.
All current tools already have the necessary programming that allows these connections automatically and instantly.
In short, CAD still has a lot to offer and a well-managed BIM system will take advantage of the potential of each tool.
