ComputerAided_Design_Engineering_amp_Manufactur.pdf

FIGURE 3.8
The vertical support fixture modules are employed to provide supports in the first plane, upward
z-direction.
In practice, at least three vertical support points are required to provide a stable positioning
(Figure 3.10[a]). The vertical support contact points are generally selected to be on the reference planes.
In addition, it may be required to provide additional supports in order to allow a uniform weight
distribution and prevent object deflection. The horizontal supports are placed against machined surfaces
or locating holes. These fixture modules, in general, provide supports in the second plane perpendicular
to the first, and in the third plane perpendicular to the first and second planes as shown in Figure 3.10(b).
This satisfies the positive location criterion for fixturing the workpiece when the subsequent clamping
operation is carried out.
The horizontal and vertical clamps are employed to constrain (i.e., clamp) the workpiece in the
horizontal and vertical planes, respectively. These fixture modules may be placed on any surface that the
geometry of the workpiece allows. However, it is recommended that the point of contact for the first
horizontal clamp should be chosen such that it would locate, and to an extent constrain, the workpiece
in the X - Y plane (Figure 3.10[c]), thus satisfying the positive location criterion. 26 Whenever possible,
© 2001 by CRC Press LLC
Structure of the data base. (From Reference 24. With permission.)