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Tolerance Stack Up

Tolerance Stack Up

By STG Machine

If you are a person who works with technical drawings, you should be careful about tolerance stack up. Otherwise, there is a high possibility for you to run into negative consequences. From this article, we are going to discuss the basics of tolerance stack up and provide some useful tips, which you can follow to avoid it from happening.

What Exactly is Tolerance Stack Up? 

When it comes to a technical drawing, the dimensions you define are called nominals. However, you will not be able to get perfect conditions while you are manufacturing. Hence, you will need to define an acceptable amount of wiggle room for the dimension. This wiggle room is referred to as tolerance. 

Tolerance stack up refers to the sum of all acceptable dimensions given the tolerance of each part. Tolerances are in a position to contribute towards the performance and cost of a product. If a product is associated with tighter tolerances, it would be difficult to manufacture the product. Hence, the product manufacturing process can be expensive. 

How Can Tolerance Stack Up Hurt Your Manufacturing Practices? 

You need to be careful with tolerances because it can lead you towards unforeseen consequences. You need to ensure that you are using the wiggle room offered by tolerance in an effective manner. Otherwise, you will end up with parts that interfere with each other. This can usually happen with assemblies, where multiple parts mate together. 

How to Avoid Tolerance Stack Up? 

You shouldn’t make any guesses with tolerances. We often see situations where designers tend to guess the placement of tolerances based on prior drawings.

It is important to determine what parts will mate or possibly interfere with the manufactured part. In the meantime, you should also determine the factors that influence the tolerance. You should do that based on calculations and apply the ideal tolerance. Then you can easily refrain from the negative effects that can take place as a result of tolerance stack up.

The main objective of technical drawing is to inform the manufacturer on how to produce a specific part. The manufacturer usually doesn’t have a clear understanding of the design or purpose of the part. Instead, the manufacturer will just manufacture the product according to your dimensions provided. Therefore, you should be careful with the tolerances you provide within each drawing.

Many companies are using statistical methods to calculate tolerance analysis. It is possible for you to implement such methodologies as well. One of the most popular statistical methodologies available for you to consider is Root Sum Squared Method. Softwares such as Solidworks have built in functionality to help automate this process. However, it is always important to have a complete understanding of the drawing before releasing it to production. Every drawn feature should fall within your calculated tolerance range to avoid tolerance stack up.

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