The “GD&T Knowledge Gap” in Industry

Abstract

Mechanical designs in industry typically do not include adequate specification of allowable part geometry variation. Poorly applied Geometric Dimensioning and Tolerancing (GD&T), ambiguous plus/minus location or orientation controls, and sometimes no variation specifications (only a 3D CAD body) are commonly all that is done. Since improper specifications cause confusion, and since functional requirements are likely either more precise, or less precise, than the manufacturing process will deliver, excessive costs of dealing with geometry variation result. Specifications which unambiguously capture the functional needs of critical part features, combined with properly gathered and consistently reported measurement data would provide a competitive advantage for any company producing a precise mechanical product. The need to capture functional requirements, and also the improved part designs that result when thinking includes the cost & quality issues clarified by GD&T makes this subject an important element of design focused mechanical engineering education. Especially when tolerance analysis and measurement process quality considerations are included, there is sufficient academic rigor to justify additional coursework. The critical seed needed to remedy industry’s knowledge gap regarding dimensional specifications and associated data is to include two academic quarters of GD&T and Dimensional Management design electives as part of every mechanical engineering curriculum.