Episode 1 Sketching

As I started to write this I realized I could go on and on forever, just about sketching. I started asking myself how to break it up so I wasn’t writing for days. The other thing that happens is every little thing leads to another discussion. So, ‘Episodes’ will be general discussions about tools (and closely related tools), and ‘Scenarios’ will be information about actually using the tools.

Those of you who have been in one of my classes (and thank you), will know that again and again I talk about keep it simple. So the three tools I try to use most are Line, Circle and Rectangle. And when I use the line tool I still try to keep my initial shape pretty simple. Some of you might say to yourself, ‘Well, why does he do that?’ The answer is a little complex, but here goes; ALL solid modelers before they can open the file the next time you want to use it, have to look at a number of things before you see the file. They have to make sure the sketches are all closed sketches (in general), they have to know where the lines, arcs, and circles are, and what their size is, etc. So, the simpler and more controlled the first sketch is, the easier it is for Inventor to start opening the file. In an assembly of 10 parts, it makes little difference how complex the part is. However, if that 10 part assembly is used in a 5000 part assembly now it starts to make a difference. And if it is used in a 50,000 part assembly it really makes a difference.

The message is try to ‘Keep It Simple’

The next thing to address with regard to sketches is ‘fully constrained’ vs ‘not fully constrained.’ It is always preferable to have a sketch fully constrained. Whenever there is doubt, or unconstrained situations this slows down the process because Inventor has to check everything against that unknown before it can proceed.

This brings up the idea of where to start a sketch. With Inventor I cannot think of a reason not to anchor your sketch, in some way, to the center point (0,0,0).

Displaying 0,0,0 or Part Origin; left-click on the ‘Tools’ tab, then left click on ‘Application Options’, left click on the ‘Sketch’ tab. Down towards the bottom left click in the box for ‘Autoproject part origin on sketch create’. In the next model you start there will be a point in the center of your screen that you can “tie” your sketch to by dimensions or constraints. You can also get to ‘Application Options’ from the Inventor Icon button in the upper left corner of Inventor 2010. Then left click on the ‘Options’ button at the bottom.

I have started a new part, and I left click on the ‘Circle’ icon, I move my cursor towards that point in the center of the screen and when I get pretty close I see a green dot, at that point I left click to start the center of the circle. Now I move my mouse away from the center point and I see the circle start to draw, and I can pretty much click anywhere to get the circle shape.

Inventor keeps track of your cursor position, similar to AutoCAD constantly giving you your X and Y position. (Lower right hand corner of your Inventor window). When you are in a sketch, and sketching (in this case the circle), it also gives you your Radius before you finish drawing the circle.

In Episode 2 we will delve into other important things to keep in mind regarding sketching, and start to look at some of the tools.

Tod