# Pro Engineer/Create Features/Extrude

ProEngineer Wildfire2 is a computer aided design (CAD) program that is used to create models on a computer in three-dimensions. Since three dimensions are used the models mimic real parts in the way that they are constructed. The models are sometimes referred to as virtual parts since at the design stage they only exist within the computer. Most of the models made in ProEngineer Wildfire2 are termed solid models which implies that the computer has a full understanding of the solidity of the part i.e. the computer ‘knows’ where there is material and where there is empty space. Solid modelers use commands to construct models that reflect manufacturing techniques, such as extrude and cut, combining these to make complex shapes.
ProEngineer Wildfire2 is a fully parametric CAD program. This means that when a part is designed and modeled dimensions are assigned which define the part. If, at a later time, these dimensions are found to be unsuitable they can be easily changed and the modification will filter through the system wherever the part appears. This is particularly helpful when dealing with collection of parts (known as an assembly) since if a modification is made to a single part, the modification is carried throughout the assembly. A designer can also define relationships between parts. For example, in an engine, if the diameter of the piston is increased or decreased, the corresponding engine block can be defined such that it is automatically modified to match the specifications of the modified piston. Using any CAD system complex models need to be built by combining simpler shapes. In ProEngineer Wildfire2 these simpler shapes are called features. Several features are combined to form a part. Using Figure 1 as an example the part shown diagrammatically is made up of four features as follows:
* A rectangular block of material is created.
* Removing material from the block creates a slot.
* Finally material is removed to form a large hole.
* Material is again removed to make four small holes.
Later tutorials will explain how several parts can be combined to form assemblies as shown in Figure 1.

## Creating a Part

In this tutorial we will introduce you to some basic modeling concepts including creating parts, creating basic features, sketching and saving information. Before starting to work through this tutorial you need to be sitting in front of a computer which has access to ProEngineer Wildfire2 and be logged on. You tutor should have advised you of how to log in already.
Start ProEngineer Wildfire2 by double clicking on the icon on your desktop or from the START menu. The main application window should appear shortly.
You will see the normal Windows features – menus, toolbars, a main graphics area and on the left side a browser window. The next step is to create your first part. To do this use the menu FILE > NEW. As you click on this menu notice the small picture to the left of the word New… This is the icon for the NEW command. You could choose this icon from the toolbar below the menu if you prefer. Generally in this tutorial the menu command is given but you will often find the icon more convenient so look out for them.
After choosing the new command a dialog box will appear as shown in Figure 3. Notice that the Part option is already checked and type in calculator as the name of this part (Note : ProEngineer does not allow spaces and other special characters in names). A second dialog will appear offering different options for parts – in particular different units of measurement. Choose mmns_part_solid which means the units of length will be millimetres and units of mass will be Newtons and click on the OK button.
Well done – you have made your first part! The part contains some features already. The browser on the left of Figure 5 shows 3 datum planes and a coordinate system. So what are datum planes? As the word plane implies these are flat areas that can be used as references for defining parts of your model. In some case you can define models without any datum planes, in other cases they are essential. Many people choose to always have a basic set of default datum planes (like the ones in your model) defined as a starting point for their model. Datum planes are displayed as rectangles that are just big enough to enclose the model. They are given names by the system such as RIGHT, TOP and FRONT. You will see datum planes drawn in either brown or black. This is to distinguish between the two sides of the datum. If you looking exactly onto the edge of a datum plane you will see two parallel lines drawn representing the two sides of the plane