3D Drawing with AutoCAD - Section 8

37.1.5 Propellers

Strictly speaking, in Autocad a helix is ​​a spline of uniform geometry in the 3D space. It is an open spiral with a base radius, a higher radius and a certain height. To build a propeller we use the button of the same name in the Drawing section of the Home tab. The command window will ask for the center point of the base, then the radius of the base, then the upper radius and finally the height. Also we have option to define the number of turns and the direction of the torsion, among others. If the base and top radius are the same then we have a cylindrical propeller. If the value of the base and top radius differ, then we will have a conical helix. If the base radius and the upper radius differ and the height is equal to zero, then we will have a spiral in the 2D space, as we studied in section 6.5.
Being a spline, the propellers should be the subject of study of section 36.1. Even if you look carefully, the draw button is next to 2D simple drawing objects, such as rectangles and circles. What actually happens is that this command is usually combined with the Sweep, which we saw in section 37.1.2, so that it can create solids in the form of a spring in an easy and fast. For this we use a circle that serves as a profile, the propeller, of course, will serve as a path.

37.2 Primitives

We call primitive the basic solid objects: rectangular prism, sphere, cylinder, cone, wedge and torus. You can find this drop-down list in both the Modeling section of the Home tab and the Primitive section of the Solid tab. As the reader can assume, at the time of elaboration, the command window requests the pertinent data according to the solid in question. In fact, many of these data and the order in which Autocad requests them, coincide with those of the 2D objects from which they are derived. For example, to create an Autocad sphere you will ask for a center and a radius to be indicated, as if it were a circle. In the case of a rectangular prism, the initial options fully match those we use to draw a rectangle, plus height, of course. For the pyramids we first draw a polygon, and so on. So it is not idle to think about the importance of knowing 2D drawing tools as a prerequisite for drawing 3D objects.
Let's see what parameters are necessary to draw the different types of primitives we have listed. It is no use suggesting that you make primitives at your discretion by experimenting with the options of each one of them.

On the other hand, if we use a visual style that shows the wire structures, as we saw in section 35.6, then, by default, the shape of the solid objects is defined by 4 lines. The variable that determines the number of lines representing the solid is Isolines. If we write the variable in the command window and change its value, then the solids can be represented with more lines, although, of course, that will detract from the speed of regeneration of the drawings. Actually the change is optional, since the properties of the solid are not modified.

37.3 Polysolids

In addition to the primitives, we can create solid objects derived from polylines and in consonance with them, these are called polysolids.
Polysolids can be understood as solid objects that are derived from extrusion, with certain height and width, lines and arcs. That is, simply draw lines and arcs with this command (like a polyline) and Autocad will convert them into a solid object with a certain width and height that can be configured before starting the object. Therefore, among those same options, we can also point to a polyline, or other 2D objects such as lines, arcs or circles, and these will become a polysolid. Let's look at some examples that allow us to use their different options.

37.4 Composite solids

The composite solids are formed by the combination of two or more solids of any type: primitive, revolution, extruded, high and swept and can be constructed using the methods of the following sections.

37.4.1 Cut

As its name indicates, with this command we can cut any solid by specifying the cutting plane and the point at which the plane is to be applied. We must also choose whether one of the two parts is eliminated or if both are maintained. The command window shows all the options available to define the cutting planes, or how to use other objects that define those planes.

Página anterior 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36Next page

Leave a comment

Your email address will not be published. Required fields are marked with *

Back to top button