The Cost Of Tolerancing

May 27, 2021

Controlling Your Cost

The Cost of Tolerancing

Several questions outline the scope of any project QTS quotes for fixturing.  During our initial review, we work with you to identify the critical areas and unique requirements of the requested tooling and develop a concept to quote and design that fits your exact needs. One of the most important factors, when we begin to quote a project for fixturing, is understanding the print dimensioning and tolerancing for each individual part, and the entire assembly as a whole. Any manufacturing process from manual mill, to CNC to grinding and honing, has some level of variance that must be accounted for.  When parts or assemblies come to QTS for fixturing that have very precise features, we must maintain that level of precision with our designs.

For these precise features, we have to:

1.  Use more precise machinery (EDM, Grind, etc) as opposed to +-0.005” CNC tolerance

2.  Limit the amount of tooling to eliminate stack up tolerance issues (more complex single parts)

3.  Add shimming or other movable features to maintain exacting precision of part assemblies

Each of these methods increases costs and time to manufacture fixturing and are necessary in many circumstances where the print tolerances call for it.  By assigning proper tolerances to print features the process runs smoothly and the customer receives tooling that provides to-print assemblies for shorter lead times and less cost.

A Few Helpful Sources on Tolerancing:

Zong, Y., & Mao, J. (2015). Tolerance Optimization Design Based on the Manufacturing-costs of Assembly Quality. Procedia CIRP, 27, 324–329.

Hallmann, M., Schleich, B. & Wartzack, S. From tolerance allocation to tolerance-cost optimization: a comprehensive literature review. Int J Adv Manuf Technol 107, 4859–4912 (2020).

Chirone, Emilio & Tornincasa, Stefano. (1999). TOLERANCING FOR FUNCTION AND MANUFACTURING.


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