Every single process has variation, and a defined tolerance basically tells how much variation is acceptable for a given part or service. For example for a product like a mobile phone, every part that goes inside the phone will have a tolerance to ensure it can be properly assembled at the end.
Why use Tolerance
There are several reasons why tolerance is used within engineering, and the tolerance can relate to a lot of different features. Below are some examples of where tolerance is used.
- Colour Tolerance: When coloured parts are produced for a mobile phone, they might be produced in several batches. Due to the fact that a new load of paint is mixed for each batch, it will naturally add some variation in colour from batch to batch. Imagine 2 parts from two different batches is mounted next to each other on a phone, in that case a slight variation in colour would easily be seen by the costumer. If they on the other hand was on each their side of the phone, then a bigger variation could be present without it being noticeable.
- Dimensional Tolerance: If two parts need to be mounted together, there could be a requirement to a dimensional tolerance for them to fit. It could be the flatness of a surface or diameter of a hole the pin from another part locks into.
Tolerances must be thoughtfully defined to avoid any issues with assembly or malfunction for the costumer. Tolerance Analysis is usually performed as part of the design process to avoid any of those issues, and to understand how imperfections when parts are produced or assembled affect the functionality costumer’s expect of the final product.
Cost of Tolerance
The defined tolerance can have a huge impact on the price of the part. Often the technology or processes used have a certain capability, meaning they are able to consistently deliver product within a certain tolerance. If a tighter tolerance is required, this could mean having to invest in new and more advanced machines and equipment, which will then be added to the cost of the part.
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