Parameters and formulas
Keep related dimensions connected as your design changes.
Parameters give names to the values that define a design. A formula expresses how one value depends on another, so you do not have to update every dimension by hand.
Choose meaningful names
Use names such as width, height, or thickness to describe the design. Keep independent inputs distinct from dimensions that can be calculated from them.
A component can use dimensions, numbers, angles, text, yes/no values, and pick-lists. An author can lock a parameter when downstream users should not override it.
Give lengths their units
Use unit helpers for fixed lengths inside a formula:
width - mm(18)This subtracts 18 millimeters from width.
A bare number inside a length formula is interpreted in canonical nanometers. width - 18 therefore does not mean “subtract 18 millimeters,” even when the interface displays millimeters.
Dimensionless numbers can stay bare:
width / 2
holes + 1Check the resulting geometry
Try the smallest and largest dimensions you expect to use. Check that holes, offsets, and other dependent features remain where you intend them to be.
A formula can be valid while producing an impractical part. Inspect the drawing and review machining again whenever its inputs change.
See Reusable components to apply the same design across multiple jobs.