![]() Note that A1, A2, A3 are datum target areas and B1, B2 are datum target points and C1 is datum target line. Basic dimensions are toleranced with gage-makers’ tolerances. Datum targets are used to establish orientation on irregular parts. All datum targets are dimensioned for location and size either by toleranced dimensions or basic dimensions. Datum Targets Datum targets are also used to establish the datum reference frame. Where a datum target area is required, the desired area is outlined by a phantom line and filled with section lines, as shown for datum targets A1, A2, and A3. Since datum target C1 is on the far side of the part, a dashed radial line is used to connect the datum target symbol. Movable Datum Target When selected (checked), the targets being created will be moveable, which will allow them to be used in generating equalized center. A datum target line is represented by a target point symbol on the edge of the part in the top view of the drawing and by a phantom line on the front view, datum target C1. Datum target points are represented on a drawing by target point symbols and identified by datum target symbols such as datum targets B1 and B2 shown in Figure.Īctual tooling points on the fixture are not points at all but pins with hemispherical ends contacting the part with the highest point on the hemisphere, as shown in Figure. A combination of datum target points, lines, and areas may be used. And one datum target establishes a tertiary datum plane. Datums should not over or under constrain the part limit all 6 degrees of freedom. Two datum targets are used to establish a secondary datum plane. Datum areas or targets should not be close to parting lines, sprues or other common casting problem areas. ![]() A primary datum plane is established by a minimum of three datum targets not in a straight line. These datum targets are usually referenced from three mutually perpendicular planes to establish a datum reference frame. Optim.Datum targets are designed to contact parts at specific points, lines, and areas. A location optimization method for aircraft weakly-rigid structures, Zhong-Qi Wang, Yuan Yang, Yong-Gang KangZhong -Qi Wang, Yuan Yang, Yong-Gang Kang and Zheng-Ping Chang, Int.Deformable Sheet Metal Fixturing: Principles, Algorithms, and Simulations. New York: American Society of Mechanical Engineers. ASME Y 14.5-2009, Dimensioning and Tolerancing.In upcoming posts, we will delve into the various cases with measured data to observe these effects. We should emphasize the fact that we could have put more than nine targets on the primary datum in different positions the number and position of locators are usually determined using finite element analysis. With this final datum target area, we have eliminated the translation in the X-axis, that is along the longest axis of the fuselage. MS NASDAQ: MSFT) amerika meunarodna korporacija sa seditem u Redmondu, Vaington, koja razvija, proizvodi, licencira, prodaje raunarski softver, korisniku elektroniku, te line raunare i servise. Tertiary datum defined by one target area (C1) ![]() In our case, these datum target areas are designated by A1 to A9.įigure 3. ![]() Since we have a very large surface, the use of datum target areas, as opposed to datum target points, makes it easier to measure. Therefore, an adequate fixturing system for sheet metal usually requires N>3 locators on the primary datum to properly restrain workpiece deformation.ĩ Datum Target Areas on the Primary Datum Planeįor our case, we selected 9 positions for datum targets on the largest cylindrical surface of the fuselage (Figure 1). Analysis shows that the average deflection of a sheet steel plate 400 mm x 400 mm x 1 mm under its self-weight can be between 1-3 mm with a 3-2-1 location layout. This deformation cannot be neglected, even under the self-weight of the workpiece. ![]() However, for most sheet metal manufacturing processes, the main dimensional problem is the sheet metal deformation normal to the surface. In a previous post, we talked about using 3-2-1 precision location to create an accurate and repeatable datum reference frame for the part, while avoiding overconstraint. ![]()
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