tailieunhanh - Dimensioning and Tolerancing Handbook Episode 2 Part 8

Tham khảo tài liệu 'dimensioning and tolerancing handbook episode 2 part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Multi-Dimensional Tolerance Analysis Automated Method 13-11 TÕỊ DRF Figure 13-14 Applied geometric variations at contact points Component tolerances are set as a result of analyzing tolerance stackup in an assembly and determining how each component dimension contributes to assembly variation. Processes and tooling are selected to meet the required component tolerances. Inspection and gaging equipment and procedures are also determined by the resulting component tolerances. Thus we see that the performance requirements have a pervasive influence on the entire manufacturing enterprise. It is the designer s task to transform each performance requirement into assembly tolerances and corresponding component tolerances. There are several assembly features that commonly arise in product design. A fairly comprehensive set can be developed by examining geometric dimensioning and tolerancing feature controls and forming a corresponding set for assemblies. Fig. 13-15 shows a basic set that can apply to a wide range of assemblies. Note that when applied to an assembly feature parallelism applies to two surfaces on two different parts while GD T standards only control parallelism between two surfaces on the same part. The same can be said about the other assembly controls with the exception of position. Position tolerance in GD T relates assemblies of two parts while the position tolerance in Fig. 13-15 could involve a whole chain of intermediate parts contributing variation to the position of mating features on the two end parts. An example of the application of assembly tolerance controls is the alignment requirements in a car door assembly. The gap between the edge of the door and the door frame must be uniform and flush parallel in two planes . The door striker must line up with the door lock mechanism position . Each assembly feature such as a gap or parallelism requires an open loop to describe the variation. You can have any number of open loops in an assembly tolerance