Pro/ENGINEER Concepts

Transcription

1 1 Pro/ENGINEER Concepts Becoming a Pro/ENGINEER user means learning to think in terms of how the components of a design interact, and to think ahead to how those interactions may change. At the simplest level, these components may be the discrete geometric shapes, called features, that comprise a solid part: extrusions, holes, or chamfers, for example. At a higher level they may be the individual parts of your assembly, joined together in an interdependent way. At all levels, this component interaction toward a common purpose is called the design intent. This chapter describes how the principle of design intent is passed through all phases of the design, from conception to final documentation. Parametric Associativity and the Design Intent Suppose you want an extrusion centered on a rectangular surface. You could place the extrusion by measuring half the sides of the rectangle and using dimensions to locate its x-y position. However, your design intent is to have the extrusion centered, even if the length or width of the surface changes. Pro/ENGINEER gives you the tools to create models based on this kind of information. In this instance, you could constrain the extrusion so it is centered between the four referenced edges. The x- and y-coordinates of the extrusion will always equal half of the length and width of the rectangular surface. Pro/ENGINEER calculates and updates the extrusion's position no matter what the dimensions of the rectangle are. You can use these and other processes to define simple geometry, or you can use them with more complex calculations like mass, volume, or center of gravity. The establishment of parametric relationships between design entities can save an enormous amount of time and effort when engineering changes are required. The more associative information that you build into the model, the more you can quickly experiment with new solutions in the design as they occur to you. You can also adapt existing 1-1

2 designs to meet new requirements and create new products from them, rather than starting a design from scratch for a product that is essentially similar to an existing one. Opportunities to create these relationships exist at every level of Pro/E, from the simplest part to the most advanced assembly. Often they are built into the workflow. The biggest challenge is to start thinking parametrically. You must constantly ask "How could this change, and what could change with it?", and then learn to create parametric relationships that can make adjustments automatically when the changes occur. End-to-End Associativity Pro/ENGINEER not only lets you design individual parts quickly, it also records their assembly relationships and produces finished mechanical drawings. You can easily access and edit dimensions and parametric associations at any stage of the workflow. The dimensions that show on the plot are derived from the 3D model dimensions and remain dynamically linked to the source 3D files. The link is bidirectional: if you edit the 2D drawing, the 3D model dimensions change accordingly. Pro/E Basic Design Modes There are three basic Pro/ENGINEER design steps from conception to completion: Part creation Assembly creation Drawing creation Each design step is treated as a separate Pro/ENGINEER mode, with its own characteristics, file extensions, and relations with the other modes. Remember that all information dimensions, tolerances, and relational formulas are passed from one mode to the next bidirectionally. This means that if you change your design at any mode level, the change is automatically reflected at all mode levels. If you plan ahead and use the associative features correctly, you can save significant time in the design and engineering process. 1-2 Getting Started with Pro/ENGINEER Wildfire

3 Part Mode: The Dashboard and Sketcher In Part Mode, you create part files (.prt), the separate components that are joined together in an assembly file (.asm). Part mode lets you create and edit the features the extrusions, cuts, blends, and rounds that comprise each part being modeled. Most features start with a two dimensional outline, or section. When the section is defined, you assign a third dimension value to it in order to make it a 3D shape. You create the 2D section in a tool called Sketcher. As the name implies, Sketcher lets you roughly draw the section with lines, angles, or arcs, and then input the precise dimensional values later. You use an interface called the dashboard to create and edit 3D feature geometry. The dashboard presents feature-specific fields for input as you switch from feature to feature. Once a 3D feature is created, it can be edited directly in the graphics window. Antenna tip in Sketcher and 3D mode Assembly Mode After you have created the parts, you create an empty assembly file for the model, then assemble the individual parts within it, assigning the positions the parts will occupy in the final product. You can also define exploded views to better examine or display part relationships. Pro/ENGINEER Concepts 1-3

4 Assembly in an exploded view Drawing Mode In a slightly more advanced scenario, you would start the model as an assembly and create each part (and part file) from what is called a skeleton part. This is the key to top-down design, where an edit to one part can automatically affect the parts to which it is joined. You can also associate one part to another part in an ordinary assembly using assembly relations these will retain associativity between dimensions as they change. In addition, with model analysis tools, you can measure an assembly's mass properties and volume to determine its overall weight, center of gravity, and inertia. Determining interference between components throughout the entire assembly is also possible. Drawing mode lets you create finished, precise mechanical drawings of the design, based directly on the dimensions recorded in the 3D part and assembly files. In fact, it is not necessary to add dimensions to objects as you may have done in other programs. Instead, in Pro/ENGINEER you selectively show and hide dimensions that have been passed from the 3D models. Any information objects dimensions, notes, surface notes, geometric tolerances, cross sections, and so on that have been created for the 3D model can be passed to the drawing mode. When these objects are passed from the 3D model, they remain associated, and may be edited to affect the 3D model from within the drawing. 1-4 Getting Started with Pro/ENGINEER Wildfire

5 Dimensioned drawing views of the antenna tip Pro/ENGINEER Concepts 1-5

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