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9.2.1. Most sets of locators are over-constrained when variation is considered. For example, a brick-shaped part could be located to a fixture with three flat, perpendicular surfaces. Using three planar moves will overconstrain the part because its three locating surfaces cannot all be perfectly flat and perpendicular. 3DCS Mech includes three methods of simplifying the locators to be perfectly constrained.
9.2.1.1. Drop DoF active: 3DCS will match the moves on a part to a case number based on the moves and features used. Each case number corresponds to a certain set of locators. For example, in a certain case the move features from each part are used to define a pair of planes, a point and line pair with the line perpendicular to the planes, and a point and plane pair with the plane perpendicular to the first plane and passing through the line. The parts are then aligned Plane to Plane, Point to Line, and Point to Plane.
9.2.1.2. Drop DoF not active: 3DCS uses the moves to define equations controlling the position of each part in the model. If a part is over-constrained, terms will be dropped from the equation until it is perfectly constrained or under-constrained. Because each term could represent more than one DoF, it is possible for an over-constrained part to end up under-constrained.
9.2.1.3. Manual: The user must set up the moves to be perfectly constrained. For example, changing an over-constrained Planar move to a Point on Plane move.