SolidWorks 2011 Parts Bible - Matt Lombard [61]
Beginning to create simple parts will help you understand techniques used in more complex modeling projects. Learning on simple tools and then expanding your skills helps you to understand best practice issues, which makes you a better contributor to a team environment.
Discovering Design Intent
By asking questions about the part's function before you start modeling or designing, you can create a model that will be easier to edit, easier to properly place into an assembly, easier to detail in drawings, and easier for other SolidWorks users to understand when someone else has to work on your models. Whether you are doing the modeling for someone else or doing the design and modeling for yourself may make a difference in how you approach the modeling task.
The purpose of these questions is to help you establish design intent. The term design intent is a statement of how the part functions and how the model reacts to modeling changes.
It may help if you try to put the design intent into words to help you focus on what is important in the design. An example of a statement of design intent is “This part is symmetric about two planes, is used to support a 1.00" diameter shaft with a constant downward load of 150 pounds using a bronze bushing, and is bolted to a plate below it.” This does not give you enough information to design the part, but it does give you information about two surfaces that are important (a hole for the bushing and the bottom that touches the mounting plate), as well as some general size and load requirements. The following questions can help you develop the design intent for your own projects.
Using symmetry
Symmetry is an important aspect of design intent. Taking advantage of symmetry can significantly reduce the time needed to model the part. Symmetry can exist on several levels:
• Sketch symmetry
• Individual feature symmetry
• Whole-part symmetry
• Axial symmetry (a revolved part)
• “Almost” symmetry (the whole part is symmetrical, except for a few features)
• Left and right symmetrical versions of the part
• Assembly symmetry
Determining primary or functional features
This is probably the most important question. Primary or functional features include how the part mounts or connects to other parts, motion that it needs to accommodate, and additional structure to support loads.
Often it is a good idea to create a special sketch as the first feature in the part that lays out the functional features. This could be as simple as a straight line to denote the bottom and a circle to represent the position and size of a mating part, or as complex as full outlines of parts and features from all three standard planes. This technique is called a layout sketch, and it is an important technique in both simple and complex parts. You can use layout sketches for anything from simply drawing a size-reference bounding box to creating the one point of reference for all sketched features in the part. You can use multiple layout sketches if a single sketch on one plane is not sufficient.
Predicting change
When the marketing department gets out of their meeting at 4:45 pm, what changes do you need to be prepared for so that you can still be out the door by 5:00 pm? No one expects you to be able to tell the future, but you do need to model in such a way that your model easily adapts to future changes. As you gain experience with the software and engineering design processes, keep this idea in mind; you will develop some instincts for the type of modeling that you do.
Determining the manufacturing method
Modeling for the casting process is very different from modeling for the machining process. When possible, the process should be evident in your modeling. There are times when you will not know which process will be used to create the part when you start to create a model. If you are simply