Equations Walkthrough

A step by step example of making one dimension follow another, from the first number to the Equations window. It uses two lines, so you can do it in a minute. For everything a formula can hold, see Equations.

Before You Start

• Sketching is part of modeling, which comes with the Pro plans.
• Open a sketch on a plane (see Planes and Faces) and draw two lines, one above the other, with the Line tool on the Sketch tab.
• The examples use inches. Use any unit you like, and type it after the number.

Name the First Dimension

1. Click Dimension on the Sketch tab.
2. Click the upper line. A box opens with Length and the three buttons Aligned, Horizontal and Vertical.
3. Type 4 in and press Enter. The line becomes 4 in long.
4. Click the number on the sketch. The box opens again, and this time it also shows the dimension's name, D1@Sketch1, after the number. That is the name a formula uses.
5. Press Esc to close the box.

Make the Second Dimension Follow

1. Click Dimension, then click the lower line.
2. In the box, type D1@Sketch1 / 2 instead of a number. The name is the one you just saw. You can type it in small letters too.
3. Press Enter. The lower line becomes 2 in long, half the first.
4. Look at its number on the sketch. It starts with Σ, the sigma sign. That marks a dimension a formula drives. Hover over it to see its name and formula.

Change the First and Watch the Second

1. Click the number on the first line, type 6 in and press Enter.
2. The first line is 6 in. The second line follows to 3 in, with no typing from you.
3. Press Ctrl+Z. Both lines go back to 4 in and 2 in in one step. Press Ctrl+Y to bring 6 in and 3 in back.
4. Try a number that does not work, such as 0 for the first line. It is refused with a message, and nothing changes.

Use the Equations Window

1. On the Sketch tab, click Edit, then Equations.... A window opens at the right of the sketch.
2. Under Equations you see D2@Sketch1, its formula D1@Sketch1 / 2 and its value now, 3 in, with the Σ mark. Under Other dimensions you see D1@Sketch1.
3. Try to make a circle. Under Add an equation, pick D1@Sketch1, type D2@Sketch1 + 1 in and click Add. D2 already reads D1, so D1 cannot read D2. A red message says so by name, ends with Nothing changed, and the sketch is as it was.
4. Change the formula of D2. Click in its formula box, type D1@Sketch1 / 3 and press Enter. The second line follows to 2 in, and the message says the equation changed.
5. Delete the equation. Click the × in the row of D2. The line keeps its length, 2 in, and D2 moves down to Other dimensions as a plain dimension.
6. Press Ctrl+Z to put the equation back. Click the ✕ at the top of the window to close it.

Rename and Use the Name

1. In the Equations window, click the name D1@Sketch1, type Width and press Enter. Or click the number on the sketch, and rename it in the box.
2. The formula of D2 now reads Width / 3. Formulas that used the old name follow the new one.
3. A name uses letters, digits and the underscore. Width works. Slot Depth does not, because of the space.

Use It in an Extrude

1. Use a sketch with a closed shape, such as a rectangle with one side dimensioned 4 in, which is named D1@Sketch1.
2. Click Extrude on the Features tab. In the Depth box, type a formula that uses a dimension's name, such as D1@Sketch1 / 4. The names of the sketch you just drew work in the depth box.
3. The depth is 1 in. It is worked out once, when you press Extrude or Cut, and stays a number after that. It does not follow later changes.

Options

• Dimension box: a number or a formula, when you place a dimension or click its number.
• Equations window: add, change, delete and rename.
• Extrude depth: a formula, worked out once.

Tips and What to Expect

• A circle, a name that is not there and a mistake in the formula are each refused with a plain sentence, and nothing changes.
• Typing a plain number over a driven dimension ends its equation. The message says so.
• Everything here is saved with the sketch, and each change is one Undo step.

Related Tools

• Equations
• Smart Dimension
• Dimensions and Units
• Relations
• Extrude and Cut