A product’s observable variability shows the degrees of freedom that process steps introduce into an item.

Overview: What is the Percent of Tolerance?

Within a batch of identically manufactured parts, a certain percentage will fall within the acceptable tolerance required by the customer. Tolerance represents the span of values between the minimum and maximum allowable range of error within large amounts of items produced. While testing each item to ensure they meet requirements is often cost-prohibitive, a statistical analysis estimates the permissible tolerance.

Three Benefits of the Percent of Tolerance

In Six Sigma, less than 3.4 articles out of a million fall out of the range of acceptable values. By decreasing the tolerance, only products approaching perfection are kept. But more rejects are created. Increasing the tolerance allows more items to be shipped, risking disappointing the customer. Benefits, therefore, of the percentage of tolerance include:

1. Attain Sustainable Results

Making products designed with an acceptable percentage of tolerance can ensure that the products can perform within those tolerance limits.

2. Describe Output Behavior

The percentage of tolerance allows the manufacturer to design an item with an acceptable degree of precision. This allows for consistent replication in the output of a product that will meet the customer’s specifications.

3. Improves Quality Control

Quality control is a matter of achieving acceptable numbers when sampling lots. Sampling items to test for variations in good tolerance range is a cost-efficient method of earning a high degree of precision.

Why is the Percent of Tolerance Important to Understand?

Tolerances establish how much room for error exists when manufacturing a part. Appreciating the crucial role tolerances play in the manufacturing process allows the production of higher-quality products with fewer costly mistakes by improving:

1. Fit and Functionality of Parts

Tolerance boundaries ensure profit when manufacturing parts that must be compatible with other items.

2. Aesthetics of the Product

The tolerance controls the dimensions and positions to produce a smooth, flush joining of parts.

3. Cost-benefits

Tighter tolerance allowances increase the cost of manufacturing, while loose tolerances reduce expenses. With a clear understanding of the desired percentage of tolerance that accomplishes the best product, customers can define tolerance requirements best for the most cost-effective outcomes.

An Industry Example of the Percent of Tolerance

Electronic components on a printed circuit board used for wireless communication must be shielded. The shielding gasket needs to precisely sit on the gold trace around the components so that it does not touch or affect the components.

Three Best Practices When Thinking about the Percent of Tolerance

Choosing tolerances is an involved process. It demands that you carefully think about the design details necessary to incorporate the customer’s requirements and the manufacturer’s capabilities. Three tips to achieve best practice results include:

1. Avoid tolerance stacking

Having too many tolerance requirements in a row can lead to flaws. Instead of having tolerances based on other points with tolerances of their own, beginning with a set point of reference can avoid subsequent manufacturing problems.

2. Establish which tolerances matter

Detail what the end product is supposed to do. Suppose you want one component to turn into a half-circle. Then, the clearance tolerance must be specified to keep the part from catching on to something.

3. Consider the materials to be used

Some raw materials may expand or contract under different temperature or moisture exposures. Suppose the material will be stored in a hot warehouse after cutting to size. In that case, tolerances must be defined to consider the effects of expansion, if necessary.

Frequently Asked Questions (FAQ) about the Percent of Tolerance

1. Isn’t the percentage of tolerance simply a tolerance range?

The tolerance range allows for calculating the percentage of tolerance, allowing for the result to be expressed as a percentage.

2. What is repeatability?

When using a gage or measurement tool to measure the same part regularly, the variation that occurs is its repeatability. A significant variation from repeatability may indicate a problem with the gage.

3. Why are tolerances necessary in manufacturing?

Variation is intrinsic in manufactured parts. Tolerances allow these variations to be controlled within acceptable ranges.

The percentage of tolerance allows for building products that will perform within the limits of tolerance needed.

The percentage of tolerance is a vital concept in manufacturing because it ensures consistency and proper performance of the parts.

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