SolidWorks 2011 Assemblies Bible - Matt Lombard [46]
Note
To connect a macro to a hotkey, first put the macro in a folder identified at Tools⇒Options⇒File Locations⇒Macros, and then restart SolidWorks. Then use the Keyboard dialog box (Tools⇒Customize⇒Keyboard) to assign hotkeys to the macros in the list.
Like SmartMates, macros work best for the simpler mate types where you do not need to select any options. The workflow with macros can be very fast, but you have to have the parts pre-positioned and be very sure of what you want.
Mating for Motion
Dynamic Assembly Motion is a powerful tool for visualizing the motion of mechanisms in SolidWorks. It works best if there is a single open degree of freedom. Assemblies with more open degrees of freedom can do some unexpected things when you try to move them. If there are multiple possible positions, the parts could jump between those positions. If the assembly has parts with unrelated open degrees of freedom, such as fasteners not constrained rotationally on an articulating arm, you may have some difficulty getting the motion you want.
Keep in mind that not all assemblies can function in multiple roles. For example, if you are trying to use a single assembly for an accurate BOM drawing, an exploded view, Dynamic Assembly Motion, setting up in-context references, and a rendering, you may find that even if you are using configurations (covered in Chapter 8) to divide the types, they might still interfere with one another.
For these reasons, you may want to consider separate assemblies for types of data that are most likely to interfere with other purposes, such as anything to do with moving parts around — Dynamic Assembly Motion, Animation, Rendering, or others.
Another question you need to ask yourself is whether the Dynamic Assembly Motion is actually necessary. Often people just set it up because they can, and may be paying consequences unnecessarily. For example, parts with in-context references should not have motion between the parts involved. If a referenced part moves, a hole or boss on the referencing part may also move. This sort of thing can be managed, but it requires discipline, and there is an element of risk to the integrity of your data should an untrained or forgetful employee gain access to it.
Analyzing degree of freedom
When working with motion in SolidWorks, you need to be comfortable with the concept of degrees of freedom. When inserted into an assembly, each model begins with six degrees of freedom:
• Translation in X (tX)
• Translation in Y (tY)
• Translation in Z (tZ)
• Rotation about X (rX)
• Rotation about Y (rY)
• Rotation about Z (rZ)
When applying mates, and especially when troubleshooting motion or overdefinition problems, it is important to look at how each mate translates into degrees of freedom being tied down. For example, a Coincident mate, planar face to planar face, ties down one translation degree of freedom (in the direction perpendicular to the faces) and two rotational degrees of freedom (about directions which lie in the plane of the faces). What remains are two translational degrees of freedom in the plane of the faces and one rotational degree of freedom about an axis perpendicular to the planar faces.
A point-to-point Coincident mate ties down three translational degrees of freedom, and the part can only rotate.
An edge-to-edge Coincident mate ties down two translational and two rotational degrees of freedom. As a result, a part that you mate in this way can only slide along the mated edge and rotate around the mated edge.
Tip
When using face-to-face Coincident mates, it takes three mates to define a block type part fully. When using edge-to-edge Coincident