Parameters

A parameter is a size with a name, such as t = 12 for the thickness of your timber. You type the name t into a dimension or a feature's box instead of the number. If you change to 19 mm board later, you change t once and every part that uses it updates.

Parameters are in the Parameters list on the left, under the feature tree.

How to add one#

1. Click + Add beside Parameters. A new parameter appears, ready to rename (the first one is t = 12).
2. Type its name, such as t, W or kerf.
3. Click the box after =, type its value, such as 12, and press Enter.

Using a parameter#

• In a sketch: with Dimension, type the name instead of a number. The dimension then shows t = 12.
• In a feature: type the name into a box, such as an extrude's Depth.
• In a Box: its width, length, height and Position X, Y and Z all take names and sums, so a cabinet of boxes can be sized from a few parameters (W - 2*t wide, at X W/2).
• In a sum: 2*t, W/2 or 600-2*t. You can use + − * / and brackets anywhere you type a size.
• π: type pi or π for the circle number, such as pi*66 for the way round a 66 mm can (a parameter you call pi is used instead).

A parameter's value can be a sum that uses the parameters above it, such as iw = W/2 - t. When the value is a sum, the number it works out to is shown beside it.

Configurations#

When you have parameters, a Configuration list appears at the top of them. A configuration is a named set of sizes, such as Tall or Wide, so one design can come in several sizes.

• Save one: set the parameters, choose + Save these sizes as… in the list, and type a name.
• Use one: choose it in the list. The design is rebuilt with its sizes.
• Delete one: choose it, then choose Delete "…". The sizes stay as they are.

Renaming and deleting#

Click a parameter's name and type a new one: every dimension and box that uses it changes to the new name. Click × to delete a parameter.

Step by step#

Here is the whole thing on a shelf, from the SchoolCAD video tutorial.

Tips#

• Only names stay linked. If you type 24 where you mean two thicknesses, it stays 24 when t changes, so type 2*t instead.
• Use short, clear names: t for thickness, and W, D and H for width, depth and height.
• SchoolCAD works in millimetres, but you can type a unit after a number and it is changed to mm: 2 in or 5 cm.

If it does not work#

• The value turns red, or shows ! Point at it to read the problem. It is usually a typing mistake, or a name that is not in the table.
• Depth: "t" is not in your parameters table. A feature uses a name that is not in the table, perhaps because the parameter was deleted. Add the parameter again, or edit the feature.
• "W" is not in your parameters table, but W is there. A parameter can only use the parameters above it in the list.
• Names start with a letter and use letters, numbers or _ (no spaces). Change the name, for example to board_t instead of board t.
• That name is already used. Each parameter needs its own name.