2D and 3D drawing model creation

Computer Aided Design (CAD) replaced traditional technical drawing with ink and paper many years ago. Easy error correction and changes, low technical effort and fast results are the main advantages of on-screen design. The simple 2D CAD modeling is now in competition with the much more powerful 3D modeling. It can be used to display products in three-dimensional form and view them from all angles. Powerful programs also have render functions that can be used to produce photorealistic images. In addition, animations can be produced with 3D programs. We will give you a brief overview of the two forms of CAD modelling.

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Function of a CAD model

 

A CAD model is primarily used to visualize the conceived construction. It gives the designer an impression of whether his solutions are practical. Every 3D program has a 2D export function. This is the basis for manufacturing the components in production. Only the additive processes of 3D printing no longer require 2D drawings. However, they are indispensable for the worker at the CNC machine.

 

Advantages and disadvantages of 2D or 3D models

 

The question of which modeling method is the "better" depends on what is to be achieved in the end. An animated CAD model is more suitable for a first impression. 2D drawings without isometrics require some experience and spatial imagination in order to get a three-dimensional impression of the end product. The 3D model speaks for itself.

However, there are specific advantages and disadvantages to both approaches.

 

2D drawings - precision and detail

The pure 2D drawing (e.g. production drawings) does not stand alone. It is supplemented by all the information required to produce a component. To do this, the 2D drawings must meet the strict technical design standards. Knowing and using these is part of the training to become a product designer. The interpretation of a 2D drawing is therefore always dependent on the skills of the skilled workers. A correctly created drawing guarantees the desired result. Typical elements of a 2D drawing are:

 

• Freeform curves (splines),
  • interpolating curves (e.g. cubic splines), run through predefined support points.
  • approximating curves (e.g. B-splines) are calculated according to based on certain rules.
• Stretches
• Arcs
• crisis

Due to their low information content, 2D drawings  nowadays place low technical demands on the PC equipment. Sketch software for making sketches is already available for free. An example of this is the "Inkscape" tool. The market leader in the 2D area is the "AUTOCAD" program. It offers a comprehensive range of functions that are required to create standard-compliant technical drawings. 

The 2D modelling is mainly used as a basis for the 3D model creation and as a pure 2D drawing (production drawing).

Advantages and disadvantages of 2D modeling : 

• requires less computing power
• less training effort 
• Often serves as a preliminary stage for 3D modeling (especially in body construction)
• contains less information than a 3D model (e.g. Oloid)
• must be supplemented with lots of information
• more difficult to visualize the model

 

3D drawings - visualization and assembly

A 2D drawing program is easy and intuitive to learn. 3D design programs, on the other hand, are a much greater challenge. Roughly speaking, with INVENTOR or SOLID WORKS you work your way from a 2D basic body to the desired shape. The enormous selection of functions can quickly overwhelm a beginner. In addition, these powerful programs place high demands on the hardware. Editing a 3D model on a laptop for less than 500 euros can quickly overwhelm the device. The rendering times are always part of the construction of a 3D CAD model. These prepare the model optically in the way the product designer wants.

 

3D model types

3D models are subdivided into edge, surface, volume and voxel models.

Edge models, as the name suggests, are represented by edges. The main advantage of the edge models is thus the low data processing, which enables fast and rapid movement on the screen. In return, the pictorial representation is not clear and the geometric description is incomplete. Edge models are often used for sketches or in plant construction. 

Surface models are created by extruding or rotating contours. The main disadvantage of this type of model is the loss of information about the inner and outer edges of the component. Nevertheless, surface models are used for vehicle bodies or in industrial design.

Solid models make up the largest proportion of 3D model types used. They are used in all areas of mechanical engineering and contain the largest amount of information. Volume models consist of topologically closed surface structures and are created by Boolean operations or on the basis of surface models. A major advantage of volume models is that physical information can also be stored in them. 

Voxel models are defined by "voxels". Simplified, voxels can be thought of as 3-dimensional pixels that have no relation to each other. An object in a voxel model is created by a defined number of voxels. These models are mainly used in medical technology, e.g. in computer tomographs, magnetic resonance tomographs or magnetic resonance tomographs.

 

Creating an animated, photorealistic model can take a powerful computer all night. However, the complexity of the CAD model created is only limited by the performance of the computer. This makes it possible to create complete machines, including all the details, on sufficiently large computers.

Nevertheless, a trend can be observed. The argument "2D is faster" hardly applies anymore today. If you have a good command of a 3D-capable program and have suitable hardware, you will need a comparable time to create the CAD model for simple components as a 2D designer. The transfer to a usable technical drawing is done at the push of a button.

Fortunately, the entry barriers to powerful programs are practically non-existent today. What cost thousands of euros just a few years ago is now available free of charge. Both in the 2D and in the 3D area, freeware offers such as INKSCAPE or FREECAD invite you to experiment, draw and construct. This allows you to learn the technical basics before investing in expensive equipment and powerful software. If you are interested in construction, then take advantage of these offers. Youtube offers a wealth of tutorials for every freeware program. You can quickly get interesting results with this.

 

Advantages and disadvantages of 3D modeling : 

• More complete product models
• Many documents can be derived directly from 3D models
• Fast detection of manufacturing problems
• Possibility of incorporating new prototyping technologies
• The 3D model is usually a prerequisite for further support systems
• Increase in efficiency through the use of parametrics, features and knowledge bases
• requires expensive hardware
• More data processing than 2D modelling

 

2D versus 3D - both are needed

Both 2D and 3D CAD modeling have their advantages and disadvantages. In the course of digitization and the associated improvements in our data processing systems, complex 3D modeling is taking less and less time and is convincing due to its information content and the possibility of using subsequent simulations to reduce the proportion of errors enormously. On the other hand, the handling of these models is much more demanding and creating them is usually more complex than 2D modeling of the same component. Both approaches are therefore justified and will remain so in the future. It just depends on what you want to achieve.