A brief analysis of various scales in CAD software

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　　When using the Haochen CAD drawing software to create drawings, setting the CAD scale is also very important. Next, we will provide a detailed introduction to the knowledge related to setting CAD scale parameters from three aspects! 　　CAD drawing scale 　We commonly refer to CAD drawings as 1:1 drawings; this 1:1 ratio is considered a scale, but in reality, CAD does not use the concept of 1:n drawings. Let’s not assume for now that entering 100 means 100 mm; strictly speaking, what we enter is 100 graphic units, as we use the metric system, and in the metric system, 1 graphic unit equals 1 mm in CAD. Drawing involves creating a representation based on the specified drawing units, by accurately reflecting the actual dimensions of the object. For a line that is 1 meter long, you enter 1000; you don’t enter 1000/100=10 just because the drawing scale is 1:100. In this way, CAD software actually has no concept of drawing scale. 　　CAD drawings do not have any scale; only non-physical representations have a scale. Since CAD drawings are created at the same size as the actual object, the actual object itself has no scale. However, non-physical drawing information such as text, dimension annotations, and symbolic graphics. Originally, there was no such thing as a scale; yet in CAD, there is one. Why? Because when electronic files are printed as physical drawings, a 1:n scaling is used, and all objects on the drawing must be scaled equally. In this way, text that is 5 mm high on the physical drawing must be set to 500 mm in the CAD electronic file when the printing scale is 1:100, so that 500/100 = 5. In other words, during the drawing process, non-physical elements must take into account the scale of the drawing. 　　Scale in CAD dimensioning styles: The global scale factor for dimensions, which is the system variable DIMSCALE; the scale factor for measurement units, which is the system variable DIMLFAC; and the scale factor for fractional heights, which is the system variable DIMTFAC. Let’s start with the scale factor for measurement units – DIMLFAC has a value of 1, which is the default setting. If we refer to the size values shown in the diagram as dimension values, then: Dimension value = Actual measured value × Scaling factor of the measurement unit. 　　Through the above formula, it becomes clear that if we want to draw diagrams at different scales on a single sheet without using paper space, we must artificially scale certain elements. For example, if we need to draw an enlarged version at a scale of 1:25 on a base map with a scale of 1:100, we must enlarge those elements by a factor of 4; thus, a length of 1000 becomes 4000, and the dimension label would also be 4000. However, we don’t want the label to show 4000 – it should still read 1000. In other words, the actual measured value is 4000, while the dimension label shows 1000. Clearly, in this case the measurement unit scale factor DIMLFAC is 1/4 = 0.25. 　　By the way, I think it is not advisable to use input data or to edit the data after breaking it down, rather than relying on this system variable. 　　The above covers the three methods for setting CAD scale parameters in the HaoChen CAD software; I hope this information will be useful to everyone~