Basics of CAD

Sketching Basics

Before we delve into sketching, make sure to check out simple navigation basics here: Navigating Onshape

What is Sketching?

Sketching is the most common way to build a 3D part in CAD. Almost every part you make will begin with a sketch that through the use of different features will become 3D. Sketches can be simple rectangles or complex shapes and many parts will require multiple sketches.

Sketching and Dimensioning a Rectangle

This quick guide will show you how to start sketching and using some of the very basic sketch features.

How to Begin Sketching

Before you even start sketching, you have to select the plane you want to sketch on by clicking on one of the three planes(front, right, top). Depending on your part it may benefit you to start on a particular and with more practice you will get better at choosing the best plane. Later on, we will also learn how to add our own planes.

Creating the Rectangle

Now that a sketch plane has been selected, your toolbar will contain sketch tools and features allowing you to begin your sketch. At first, it may seem overwhelming with the amount of sketch features, but for now we will focus only on a few. Onshape like most CAD software has built in functions for making simple shapes that include the correct constraints and for now we will select the rectangle feature. Once selected, you can place a point anywhere and drag out your mouse to create a rectangle. Then click on the second point to create the rectangle which should look similar to the picture.

Dimensioning The Rectangle

Dimensioning is one of the most important tools and is how we can ensure things integrate properly. To dimension you have to click on dimension icon which is shown on this page: Common Sketch Tools. Once you have clicked it, you can press on each line on the rectangle to dimension it. Though be aware that because the rectangle has constraints you can't dimension two lines that are parallel. If you want to learn more about constraints go to: Sketching Constraints.

Another Approach

In CAD there is always multiple ways to make one part and no way is necessarily wrong as long as the final part is the same. Though certain ways can be more efficient and make the part easier to modify later on. When creating a part you have to think about the best way to make it and if there is things that may need to be changed later on. As you get more practice, you will get better at finding the finding the most efficient and best way for each particular part.

Selecting Your Plane

Before we selected whichever plane, but now we want to sketch on the right plane as this will help us later on. Whenever you start sketching take time to consider which plane will be the best to use. Later on, when parts become more complicated choosing the right plane can really help.

Creating Sketch Entities

Unlike the first approach, this time we are going to use the line function. The line function can be used to make any straight lines and will apply some constraints. To sketch a line you can click anywhere, but for this example click on the origin. Now, you can drag the line out and click again to create the line. The line will turn black which tells you the entity was created. After creating the first line, click on end the point of the of first line and sketch a vertical line. Continue sketching the other two lines and when you are finished the rectangle will become shaded telling you it's a completely enclosed shape.

Dimensioning

Just like the first approach, you can use the dimension tool to dimension each line. Also, if you want, you can remove the constraints and mess around to see how they affect dimensioning. You might realize that now you can dimension every line and even move the entire shape around. To learn more about what you can do with constraints go to this page: Sketching Constraints.

What Is Design Intent?

Conclusion

After sketching both rectangles, you can now see how there is multiple ways to get the same sketch. The second approach was slower, but later on it will save time since we started on the right plane. Design intent can help save time later on and increase efficiency.

Next Walkthrough: 2D Sketch to 3D Part

Extra Tutorials

*highly recommend*

Onshape has a course here: Onshape Introduction to Sketching . You can follow with the videos and get a better understanding of what you are doing.
YouTube has a lot of videos that go really in depth, but some do involve more complicated sketches and include extrudes. Below is a list of some good videos on sketching.

Important Resources

These resources will help you learn and identify more features, and get you ready to create more complex sketches.

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