Scale settings for AUTOCAD

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AUTOCAD’s scale setting experience 1. Drawing scale we* Commonly referred to as AutoCAD 1: 1 drawing, this 1: 1 should be regarded as the concept of proportion, but in fact AutoCAD has no 1: n drawing argument. Let’s not say that inputting 100 means 100mm. Strictly speaking, what we input is 100 graphics units, because we are using the metric system, and 1 graphics unit in the metric system is 1mm in AutoCAD. Drawing is based on the set graphics units and the actual drawing. For a line with a length of 1m, you enter 1000, not because the drawing scale is 1: For 100, enter 1000/100=10. In this way, AutoCAD drawing actually has no concept of drawing scale. 2. Printing scale In actual engineering, it is impossible to draw drawings as large as the physical object. In other words, the AutoCAD graphic file in the computer is not a drawing, but just a graphic electronic file. To turn it into a real physical drawing requires 1: nPrint out the picture. 1: 100 printing means printing a 100mm long line into 1mm long. In other words, if a 1000mm long line on the electronic file is printed and is 20mm on the drawing, it is called 1: 50 print out the picture (1000/20=50). Because of this, when drawing with AutoCAD, it is better to understand the drawing proportion as the printed drawing proportion, which is more appropriate. 3. Real objects have no proportions, only non-physical objects have proportions. Since AutoCAD allows the drawing to be as large as the real object, then the actual object has no proportion. However, non-physical drawing information, such as text, dimensions, and symbolic graphics. Originally there was no such thing as proportion, but there is proportion in AutoCAD. Why? Because, when printing electronic files into physical drawings, 1: n Zoom printing, all objects on the picture must be scaled equally. In this way, 5mm high text on the physical drawing, when the printing scale is 1: When 100, it must be set to 500mm on the AutoCAD electronic file so that 500/100=5. In other words, during the drawing process, non-physical content must consider the drawing scale. Here comes a concept: Because the object needs to be reduced n times for printing, the originally unscaled object must be enlarged n times in advance. Revise: There is a wrong concept about units above. It should be that DWG files only have graphics units. There is no metric system. One graphics unit = 1 mm. All millimeters, meters, and inches are set when printing, that is.: The units are printed. Before printing, they are just graphic units. 4. The proportional dimensioning global scale factor in the dimensioning style is the system variable DIMSCALE. The measurement unit scale factor is the system variable DIMLFAC. The fractional height scale factor is the system variable DIMTFAC. Let’s talk about the measurement unit scale factor first, DIMLFAC=1, which is the default setting value. If we call the size values ​​shown on the diagram dimensioning values, then: Dimension value = actual measurement value × measurement unit scale factor. Through the above formula, we know very clearly that if we want to draw pictures of different scales on a picture and do not use paper space, we have to artificially scale certain graphics, such as in 1: On the main scale diagram of 100, draw 1: 25, we need to enlarge this part of the figure 4 times. The length of 1000 becomes 4000, and the dimension is also 4000. However, we do not want to mark it as 4000, but still want it to be marked as 1000. In other words, the actual measurement value = 4000 and the dimension value = 1000. Obviously, the measurement unit scale factor DIMLFAC = 1/4 = 0.25 at this time. Let me just say it, I think it is not advisable to use this system variable instead of inputting data or editing the data after breaking it. 5. Viewport proportion This viewport refers to the viewport opened in the paper space. Beginners are not very familiar with the concept of paper space. Let me first explain the concept of paper space with a metaphor. You write some text and draw some graphics on a piece of paper, and then cover it with a piece of white paper, and you can't see anything. Make a small square hole in this piece of white paper so that you can see part of the paper below. Putting the distance between the two pieces of paper further, you see more and more things, but also smaller and smaller things. The bottom piece of paper is called "model space", the top piece of paper is called "paper space", and the small square hole is called the "viewport". The distance between the two pieces of paper is set using zoom, which is the viewport ratio. Note that the small square hole is just for you to see, because there is a piece of transparent paper stuck on the square hole, so the content on the lower paper cannot be modified on the upper paper. Open up the transparent paper on the small square hole, and it will become a real hole. You can extend the pen through the small square hole to change the things on the paper below. This is called "activating the viewport". A small hole can see everything on the paper below. This means that a small drawing can draw the entire building. As long as the distance between the two pieces of paper is adjusted, then the picture frame can be drawn on the top paper, no matter how big the things underneath it are, it can always fit in. If the distance is too large and you want to see the part clearly, then make a small hole. Of course, you have to cut the paper so that the small hole can be closer (ACAD does not need to "cut"), so that different proportions can be expressed on the same picture. Because it can express different proportions, the Chinese version calls paper space "layout". Obviously, with this function, when drawing graphics of different proportions on a picture, there is no need to manually scale the graphics. All objects are 1: 1 painted. When drawing in paper space, the natural printing ratio is 1: 1 (theoretically you can also 1: 2. Printing, the problem is that no one will ask for trouble like this). In this way, the viewport ratio has nothing to do with the printing ratio, but is related to the drawing ratio. Since it is related to the drawing ratio, different viewports must be opened for different ratios and different viewport ratios must be set. In order to facilitate understanding, we can use a popular saying: When using model space, you rely on the printer to adjust the drawing scale. When using paper space, AutoCAD adjusts the scale first and then prints it, so you don't have to rely on the printer. There is such a saying: “No matter how many scales there are on a picture, there is only one global scale factor DIMSCALE for dimensioning. ” This is drawing in model space. At this point, we are using paper space to draw. This sentence is wrong. When there are different proportions on a picture, it is actually equivalent to "printing" from model space to paper space at different proportions. In this way, this DIMSCA LE is not the same. Fortunately, the viewport ratio and the "printing" ratio are already available, so users simply do not need to use that DIMSCALE to avoid confusion, so DIMSCALE=0 (not set) in the dimensioning style. Do not set DIMSCALE, and there is no artificial scaling. DIMLFAC is always equal to 1.0. In this way, no matter how many different proportions there are on the diagram, there is only one dimensioning style.