SolidWorks 2011 Assemblies Bible - Matt Lombard [48]
FIGURE 5.9
A robot arm assembly with degree-of-freedom conflicts
Working with Advanced and Mechanical Mate Types
Advanced and Mechanical mate types greatly expand the number of ways that you can put parts together into assemblies. Advanced mate types include Symmetric, Width, Path Mate, Linear/Linear Coupler, and Limit. Mechanical mate types include Cam, Hinge, Gear, Rack and Pinion, Screw, and Universal Joint. You can access Advanced and Mechanical mates by expanding the corresponding panels on the Mate PropertyManager shown in Figure 5.1.
If you understand sketch relations, the standard mate relations fall into place easily. One exception is the Lock mate. Lock is different from Fix, which pins a part to the background. The Lock mate locks two parts to one another, so that they always maintain the same relationship to one another, regardless of how they move with respect to other parts. This section goes into some detail of all the Advanced and Mechanical mates, with a brief example of each.
Symmetric mate
The Symmetric mate works a lot like the Symmetry relation in sketches, except that a plane is used as the plane of symmetry instead of a construction line. Figure 5.10 shows a Symmetric mate being applied to the gripper jaws. The Symmetric mate is listed in the Advanced Mates pane of the Mate PropertyManager.
FIGURE 5.10
Applying a Symmetric mate
Cam mate
The Cam mate creates a special instance of either the Coincident or Tangent mate. Four conditions exist with the Cam mate:
• Coincident. The vertex on the follower mated to a cam that is created from a single closed-loop face (spline, circle, and ellipse).
• Tangent. The cylindrical or planar face mated to a cam that is created from a single closed-loop face.
• CamMateCoincident. The vertex on the follower mated to a cam that is created from multiple faces. This condition enables the follower to go all the way around the cam, not stopping at the broken faces or following the extension of a single face.
• CamMateTangent. The cylindrical or planar face mated to a cam that is created from multiple faces. This condition enables the follower to go all the way around the cam, not stopping at the broken faces or following the extension of a single face.
Figure 5.11 shows both single-face and multi-face cams, along with the Cam Mate interface. The two assemblies are available from the DVD in the file named Cam.sldasm.
FIGURE 5.11
Using Cam mates
If you open the assemblies and spin the cam plate, you will notice that in both cases, the flat follower does not work very well. In fact, in the single-face cam assembly, it does not work at all.
Note
Barrel (cylindrical) cams cannot use the Cam mate to create cam motion, but they do work with the Path mate. Path mates are covered in more detail later in this section.
Width mate
The Width mate is often used as a replacement for the Symmetric mate in situations where parts are modeled with some tolerance and have a gap rather than touching face to face. The Width mate requires two pairs of faces to be selected, and works particularly well when a part has to be spaced evenly between two faces and there is no mid-plane, for example, when a square key is placed in a square keyway that is somewhat larger than the key. If a mid-plane is available, the Symmetric mate may be a better option, or at least a faster one to mate, given that the Symmetric mate only requires two faces and a plane. Figure 5.12 shows a good application for a Width mate as well as the PropertyManager interface for the mate.
FIGURE 5.12
Applying a Width mate
Gear mate
The Gear mate enables you to establish gear type relations between parts without making the parts physically mesh. You can also apply gear ratios and directions without physical connections, so that