CDD ABCs
Designers can evaluate and improve an assembly using constraint-driven design (CDD) in four steps:
1. Determine the degrees of freedom (DOFs) and assembly constraints (ACs) in the assembly as a whole.
2. Identify the mating pairs in the assembly. Count the DOFs and ACs in each pair.
3. Sum the ACs for all the mating pairs to get the total number of pair constraints (TPC). If your TPC is bigger than the system’s AC, the design might be prone to assembly or disassembly problems.
4. To cut the TPC, delete mating pairs or change their type. For example, a pin inserted into a hole (cylinder-cylinder) only has freedom in the Z direction and Z-axis rotation. Expanding the hole into a slot adds X-direction mobility and Y-axis rotation.