Transitioning from 2d to 3d autocad drawings

Wednesday, August 20, 2008

Beginning a drawing in AutoCAD: Model space and drawing units


Dear Daily AutoCAD readers, previously I wrote an article named as Understanding Scale Concept and Drawing Units, and it includes some fundamental concepts necessary to be known before starting a new drawing in AutoCAD. I was very a popular article, so I decided to write a series of articles to explain these concepts that are essential for beginning a new drawing in AutoCAD. As drawing area, we have two options in AutoCAD. One of them is modelspace and the other one is paperspace.
Fig. 1
When AutoCAD is opened, first thing that appears on the screen in a part where “Command:” is written and some tabs as seen in Fig. 1. These tabs follow as Model/Layout 1/Layout 2. Unless you do something controversially, “Model” tab is active. Among the drawing areas that I mentioned above, first and the main one is this “ModelSpace”. Other area where you can make drawing is “Layout”, in other words what we call paper itself. Maybe just because some users can’t give up their traditional drawing with pencil and paper, they want to do the same with AutoCAD. However, first thing that you should learn is that you should prepare your drawings in ModelSpace. If we accept ModelSpace as our drawing environment in AutoCAD, then we can define our drawing as “model“.

After accepting the first rule of drawing as preparing the model in ModelSpace, then the second important thing in starting a new drawing is selecting the proper units. In ModelSpace there is no measurement reference like centimeters or inches on a ruler. Instead, there is the concept of “Drawing Unit” in ModelSpace, and you always draw with scale of 1 to 1 (If you don’t do it his way, you will have difficulty in scaling). Thus, if you draw a line that has a length of 5, its length will not be either 5 cm or 5 inches. You will have drawn a line with 5 drawing units. At this stage, what you have to decide is which dimensional unit you will assume as 1 drawing unit. For example, you are drawing in architectural discipline and you want to work at 1/100 detail (1/32” = 1’ 0”).

Most commonly accepted way of drawing in 1/100 scale is accepting 1 drawing unit = 1 cm ( For architectural format 1 drawing unit = 1 inch). This decision that you must give will affect all of the stages in drawing from dimensioning to taking sprint outs.

As a summary, you are not drawing with versatile and set-squares on paper anymore. After this time, you will prepare your model by a “drawing unit” that you assume in a space which includes all of your model. In the next article, I will explain units.

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