Friday

Hatching from A to Z

All AutoCAD users

Hello dailyautocad readers,

There has been innovations in hatching after AutoCAD 2000. This article is prepared for those a wide range of people from those who have no knowledge about hatching to advanced users. I hope it will be useful for you.

As you know, hatching is used for highlighting a certain area of the drawing according to the standard of which drawing discipline it is used for. Main difficulties that users suffer while hatching are determination of the area that will be hatched, hatching scale and slowing down the drawing. In this article, we will examine all of these by starting from the beginning. You can access hatching command from draw menu, toolbar or by writing ‘bh’ into the command line.

1.STEP: Determine the area that you will hatch.

Selection of the area that will be hatched is important. For example, let’s take a look at the two examples below:

 
Fig.2/3 Examples for the areas that will be hatched one inside another and a single area that will be hatched. 

If we examine the geometry of each hatching in Fig. 2, you will notice that one of them includes one area in another one, and the other one does not include any spaces inside that are that will be hatched. This shows us that the area that will be hatched shows varieties from time to time. First of all, let’s see the simple one, thus the one in Fig. 3. When we enter ‘bh’ into the command line, then we get the hatching window as shown in Fig. 4.

Fig.4 HATCH window

In this window, you will use ‘Boundaries’ part to define the area that you will hatch. There are two different commands in this window. One of them is ‘Add: Pick Points’ and the other one is ‘Add: Select objects’. First one is most commonly used for defining closed areas and for those which do not include complicated areas like shown in Fig. 2. So, it is the most common type that you will use. It is enough to pick the area that you are going to hatch, just by clicking once inside the area. Now, let’s select the hatching area of the machine part shown in Fig. 3 by using ‘Add: Pick points’ method. If you pick a point inside the area that you will hatch, first area will be determined as shown in Fig. 5.

Fig.5 Determining the boundaries of the first hatching

As you can see, axis line that passes though the center divided the hatching line into two, however this is not the exact area that you would like to hatch. For now, it is not important. As you add more hatching area they will be shown with dotted boundaries in total. Finally, pick the upper right part of the detail drawing that will be hatched and press <ENTER> button. By this way, you finished picking the area that will be hatched. If we would have made the hatching shown in Fig. 2, then we should have selected ‘Add: Select objects’ option and it would be enough to select all of the entities in the drawings. Because, when we use entity selection method, then AutoCAD determines the area by skipping one by one if there are multiple entities one inside another. For example, it leaves the circle and triangle inside the rectangle empty but it hatches any area inside them if there is. This can be clearly seen in Fig. 2. Now, let’s continue.

Step.2 Defining the hatching pattern, preview and scaling

After determining the area that we will hatch, nest step is to define the hatching pattern. We can do this from the ‘Pattern’ combo box. You can learn about the hatching patterns by trying different patterns here. In our example, we will use ‘ANSI 36’ hatching pattern. After defining the hatching pattern as ‘ANSI 36’, then you can see how the hatching will look like by pressing ‘Preview’ button. Of course, only if your scale settings are correct. Otherwise, either you will not see anything and obtain a message prompt from the command line or you will see that hatching was not done by the intervals that you wanted. If you get ‘Hatch spacing too dense, or dash size too small.’ message from the command line, then it means that your scale is very small, or if you see ‘Unable to hatch the boundary.’ message from the command line, then it means that your scale is too big. In addition, you will see a hatching, however it will not be having the spacing that you desire. Return back to the hatching window, by pressing <ESC> button. In any of the three possibilities, you should change the scale value according to the situation and again press the ‘Preview’ button. Don’t worry, it is already not possible to get the correct scale at once. If the hatching looks proper in the preview window, then press <ENTER> button and exit the hatching.

Step.3 Setting the scale properly and layout

In architectural or mechanical drawings, hatching scale is very important. For example, you will make a 30×30 ceramic hatching and your hatching spacing is exactly 30×30. Let’s learn Let’s learn how to get the correct scale by this example. First of all, let’s draw a wall that has 3360 cm width and 270 cm height and hatch its interior by using NET hatching patterns and 1 scale value. Now, let’s measure one edge of the square ( in order to dimension it, you have to explode the hatch ). In my example, it is 3.175. Now, let’s erase the hatch by making undo 2 times and make the calculation. Now it is 3.175 units even if it should have been 30. My hatching scale is 1 unit (yours may be different). Here’s the formula for the correct scale:

Eq.1

For instance, in my example:

Eq.2

If we change the scale according to this and make the hatching again, then size of each square will be exactly 30.

Step.4 Other hatching methods

If you want to fill the area completely, then you can do this by selecting SOLID hatching pattern (Fig. 6).

Fig.6 SOLID hatching pattern

You can also make the filled hatching by using gradient. If you select the Gradient tab as shown in Fig. 4., you will see the window as shown in Fig. 7. It is very obvious here:

Fig.7 Gradient hatching window

You should select from one or two color gradient options and make the necessary settings.

STEP.5 Important points that should be taken into account while hatching.

• Not as much as it is in earlier versions, but hatching lines are still entities that slows down the drawing.
• Make your hatchings in a separate layer and be sure that you can work by turning off this layer if necessary.
• Never explode hatching entities. Because, hatching entities are indeed references, repetition definitions of which are predefines and if they are exploded, then they are converted in to thousands of entities, thus slow down the drawing. Another reason is that hatchings are composite entities and there are automatically updates if their boundary elements are stretched.
• Finally: In order to align hatch, use ‘Hatch Origin’ part that is under the hatch align window (Fig. 8).

Fig.8 Aligning hatch

Here, settings that is shown in Fig. 8 is done by accepting the lower left corner for aligning. However, by selecting ‘Click to set new origin’ option, you can align your hatch to any point that you want.

That’s all for now. I hope I was able to help. Have a nice day.

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