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Driving the position indirectly

You can also use mates to drive configured positions of the assembly using a series of angle mates. This makes it more difficult because to get to a particular location, you have to do some calculations, but the angle mates are more stable than simply relying on moving parts to unconstrained positions.

If you cycle through the derived configurations under the Indirect top-level configuration, you will notice that mates are not suppressed and unsuppressed; instead, the values are changed. This makes it more difficult to position the grippers precisely, but because it is specific about the positions of the individual parts, there is no ambiguity.

Positioning with sketches

Although this technique still uses mates to position the parts and to change the position, you change sketch dimensions rather than mate values. Sketches used to drive parts from an assembly are sometimes called layout sketches or skeletons. They are also discussed in Chapter 10 for in-context or top-down assembly techniques. Figure 8.10 shows the same assembly that is used for the rest of this chapter.

FIGURE 8.10

Positioning assembly components with sketches

This particular assembly is driven by two sketches on different planes to govern the position of the parts. Keep in mind that this assembly has been used for all the other techniques as well; this means that all these techniques can exist together simultaneously and are controlled by configurations.

Examine the assembly to see how the parts are mated to the sketches. This is important. The first time you create a part such as this, you may be tempted to mate part planes to the sketch lines.

Caution

Beware that mating planes to sketch lines has a very serious drawback. Unlike other types of mates, which have an alignment that you can control, plane-to-sketch line mates cannot be aligned. This means that the software may not align elements correctly on any plane-to-line mate.

Best Practice

A better way to mate part planes to sketch lines is to mate the Temporary Axes through the joints with the sketch endpoints. This solves the alignment problem.

Applying configurations for product variations

In this case, product variations mean variations in size or part replacement. Some examples are a 4-foot cabinet and an 8-foot cabinet, or a two-button mouse and a three-button mouse.

As a simple example, Figure 8.11 shows the familiar robotic arm assembly, but with a variation: one of the arms has been replaced with a subassembly. The subassembly is made of the original replaced part using configurations, and there are configurations of the subassembly, which is again being used as a flexible subassembly.

FIGURE 8.11

A part that is replaced by a subassembly

Through the course of this chapter, the robot arm assembly has greatly increased in complexity, but it has retained the original information that was in the first version. Maintaining valid assembly data through manually managed configurations is difficult, and all it takes is a simple mistake to wipe out a lot of assembly configuration data. Appropriately, the next section discusses assembly design tables.

Using design tables for assembly configurations

This chapter augments information you need to know to use design tables effectively in assemblies. Assembly design tables can do everything that part design tables can do, except for selecting configurations of base parts and split parts, which are not valid assembly functions. Assembly design tables can also do some things that a part design table cannot, including the following:

• Suppressing the state of a part (R for Resolved or S for Suppressed)

• Assigning the component configuration for the assembly configuration

• Enabling you to activate the Never Expand in BOM option

If you have been using design tables for a while and are familiar with older versions of SolidWorks, then you may have noticed that the $show parameter, which specified