Understanding scale concept and units in Autocad…
I wanted to write this article, which will help you to understand the AutoCAD’s working logic and learn some concepts like scale and unit, if you have just started using AutoCAD or if you are learning it by yourself.
First of all, I would like make clear that, whichever drawing you are making, area that you are substantiating this drawing is called modelspace. If you are using AutoCAD 2000 or higher versions, you have noticed phrases like “Model / Layout1 /Layout2” over the small tabs under the area which you are making the drawing. Do not forget that you make your drawing in Modelspace.
Just on the lower left corner of Modelspace, there is an icon that shows x and y axes. This is called UCS (User Coordinate System) icon. This icon shows the coordination system according to which you are currently making your drawing. Arrows pointing at x and y directions shows the + direction of Modelspace.
Now we can mention the subject of scale and unit. Coordinate system in AutoCAD Modelspace is cartesian coordinate system. If you take 0,0 point as origin where x and y values are 0 (this is the lower left corner of your screen), values towards right and up will be positive. Accepting 0,0 point as origin, x-axis is 0 degree towards rigth according to degree angle system. Angles will be according to counter clockwise, y-axis will be 90 degrees in + direction, x-axis will be 180 degrees in – direction, and y-axis will be 270 degrees in – direction.
We know that the drawing you make in AutoCAD is called model and the area in which this drawing is made is called Modelspace. This point is very important, drawing isn’t done by scale like it is done on paper, it is done as 1=1 and scaling is made when printing on paper. However, it is important how you accept 1 AutoCAD drawing unit. AutoCAD paper (layout) unit is mm(milimeters). Let’s say, you are drawing a architectural project and you accept 1 drawing unit as 1cm. So, you started your drawing with the assumption of 1 dwgUnit = 1cm. You continue drawing according to certain rules like the doors will be 100 units, height of tables will be 75 units. Thus, you draw everything on the cm basis. When you take print out, if you don’t change the scale, each 1cm will look 1mm as the AutoCAD unit is milimeters(mm). In other words, it will be printed as 1 dwgunit (we accepted as cm) = 1mm, which means 1/10 scale. In order to take print out, you should state in the scale part that your 10 drawing unit (that is to say 100 mm) shall look 1mm on paper, which is 10=1.
I hope it does not look complicated. In order for your AutoCAD drawings to be precise and to take print outs according to any scale at any time you desire you should make an acceptance for 1 drawing unit and you should draw according to one on one scale.
I will be glad to answer if you have questions. I wish you nice works.
First of all, I would like make clear that, whichever drawing you are making, area that you are substantiating this drawing is called modelspace. If you are using AutoCAD 2000 or higher versions, you have noticed phrases like “Model / Layout1 /Layout2” over the small tabs under the area which you are making the drawing. Do not forget that you make your drawing in Modelspace.
Just on the lower left corner of Modelspace, there is an icon that shows x and y axes. This is called UCS (User Coordinate System) icon. This icon shows the coordination system according to which you are currently making your drawing. Arrows pointing at x and y directions shows the + direction of Modelspace.
Now we can mention the subject of scale and unit. Coordinate system in AutoCAD Modelspace is cartesian coordinate system. If you take 0,0 point as origin where x and y values are 0 (this is the lower left corner of your screen), values towards right and up will be positive. Accepting 0,0 point as origin, x-axis is 0 degree towards rigth according to degree angle system. Angles will be according to counter clockwise, y-axis will be 90 degrees in + direction, x-axis will be 180 degrees in – direction, and y-axis will be 270 degrees in – direction.
We know that the drawing you make in AutoCAD is called model and the area in which this drawing is made is called Modelspace. This point is very important, drawing isn’t done by scale like it is done on paper, it is done as 1=1 and scaling is made when printing on paper. However, it is important how you accept 1 AutoCAD drawing unit. AutoCAD paper (layout) unit is mm(milimeters). Let’s say, you are drawing a architectural project and you accept 1 drawing unit as 1cm. So, you started your drawing with the assumption of 1 dwgUnit = 1cm. You continue drawing according to certain rules like the doors will be 100 units, height of tables will be 75 units. Thus, you draw everything on the cm basis. When you take print out, if you don’t change the scale, each 1cm will look 1mm as the AutoCAD unit is milimeters(mm). In other words, it will be printed as 1 dwgunit (we accepted as cm) = 1mm, which means 1/10 scale. In order to take print out, you should state in the scale part that your 10 drawing unit (that is to say 100 mm) shall look 1mm on paper, which is 10=1.
I hope it does not look complicated. In order for your AutoCAD drawings to be precise and to take print outs according to any scale at any time you desire you should make an acceptance for 1 drawing unit and you should draw according to one on one scale.
I will be glad to answer if you have questions. I wish you nice works.
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