Geometrical Dimensioning & Tolerancing of a Car Seating System

Abstract

Geometric Dimensioning and Tolerancing (GD&T) is one of the most important tools which is used in Industry since ancient times. Application and development of GD&T technique arose during the World War II as the critical parts which were shipped from long distance were having fitment issues. Since then GD&T is widely used in industry. Similarly GD&T plays vital role in Automobile seating industry.

The aim behind performing this project is to rectify the GD&T issues which affects the stack up tolerance for complete seat assembly. Two critical sections of rear seat are studied and stack up analysis are performed using Worst Case and Root Sum square Techniques using spreadsheet. Variations found in both are taken into account.

Conceptual design of checking Fixtures and gauges have been developed for the verification of tool trial parts which were produced at initial level. Applied GD&T to parts are taken into account to develop the check fixtures. Basic concept of GO-NOGO gauges is used to develop checking gauges. Check fixture pin calculations have been performed against the applied GD&T to part level. Checking fixtures and 5 samples of each part are verified against the CMM report.

Complete process of a product development is performed starting from tolerance charting to tool trial, build parts and verification. Relaxation of tolerances is also taken into account due to manufacturability issues as well as difficulty in maintaining the tolerance which didn’t affected the functionality of part. Applied GD&T is freezed to an agreement after tolerance relaxation.