Statistical tolerance analysis using ToleranceCalc 6.0
White paper by Mr. Mike Poccia

Challenge: Today many companies are beginning to recognize that tolerances related problems are causing significant damage to costs and competitiveness.

There are two main aspects to the problem:

1. Currently many companies are using the "design, manufacture, inspect, reject, redesign" paradigm for product development. Frequently they specify tighter tolerances than would be necessary with the expectation of achieving better product quality. However, it is becoming increasingly clear that the costs associated with inspection, rejection, rework, redesign and excessively tight tolerances are themselves driving product costs out of control.

2. The prevalent tolerance analysis methods are self-limiting - frequently they are applied at the end-of-line. With tolerance analysis relegated to the end of the design process, one can only hope to catch problems, not prevent them.

The solution lies in a comprehensive DFM (design for manufacturing) process focused on product quality from the very early stages of product development. Which means all designers and engineers must participate in achieving the company's product quality goals.

Existing solutions: Currently there are many software tools available to perform analysis of drawing tolerances by an established method called Monte Carlo analysis.

These tools fall into two categories - expensive, complex, high-end tools, some of which are integrated within CAD packages, and inexpensive low-end tools many of which work as Microsoft Excel add-ins.

With high-end tools all but the simplest problems require the work of a specialist. This limits their usefulness during the early stages of product design. The low-end tools require geometry information to be entered manually - a tedious and error prone process. For most geometric relationships this can get very complicated very quickly.

ToleranceCalc 6.0: ToleranceCalc 6.0 is a statistical tolerance analysis tool that deals directly with 1D and 2D tolerance chains that are imported from any popular CAD application. It's true power lies in its speed, ease-of-use, and flexibility. It is made for the early stages of product development, where the cost to fix is minimal and the benefits are greatest. Its flexibility, though, makes it useful all the way to the shop floor.

About Mike Poccia: Mike Poccia is a mechanical engineering veteran from Eastman Kodak. As a Six-Sigma Black Belt, Mike has been a panelist and presenter at the ASME Design Technical Conferences, Six-Sigma Conference, and the first Key Characteristics Conference. Mike holds BS and ME degrees in Mechanical Engineering from Rensselaer Polytechnic Institute. He is the holder of five U.S. patents on mechanisms in printing presses, ink-jet printers, cameras, and Computed Radiography scanners.