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How to Calculate Tolerance in Engineering Or Other Manufacturing Process


How to Calculate Tolerance in Engineering Or Other Manufacturing Process

The market nowadays requires products to be delivered quickly to meet customer needs. Therefore, in manufacturing, the importance is placed on how quickly the development schedule can be achieved. However, being overly conscious of speed can be a waste of time if the quality of the product is compromised due to a miscalculation of tolerance design. So what points should you pay attention to when determining tolerances? This section introduces the meaning of tolerance in the first place and how to design tolerances in detail.

The Fundamentals Of Tolerance Design


When a machine is made it is not made entirely in one go. It often includes many parts which needs to fit well to assemble it. Es the individual parts go together with other parts which essentially will end up becoming a fully assembled machine, these parts need to be perfectly measured in order to fit with each other and work properly. These fits need to be controlled under some standards, with defined tolerances.

What Is Tolerance?

Tolerance refers to the error allowed from a specified dimension. For example, when machining a 150 mm piece of material, even if everything is machined in the same way, it will not be exactly the same length and there will be some error. This difference is technically difficult to reduce to zero, even if you try to keep it small. Therefore, an acceptable range is set as the axis of manufacture with respect to the target values. Tolerance is a criterion that is also defined in JIS.

If the tolerance range is exceeded, the quality and performance of the product is affected, so it is essential to manufacture within the range. The ability to produce within the tolerance range is called the process capability index.

What Is Tolerance Design?

Tolerance design, as the term implies, is about setting tolerances. When determining tolerances, product and component specifications and costs must be taken into consideration. Tighter tolerances increase the quality of the product and reduce later defects. However, production costs increase because strict control is required at the manufacturing stage when the parts are machined.

However, when tolerances are made looser, the errors in each finished product are also greater, which causes problems after shipment and increases the defect rate of the product. This could result in higher costs. Tolerances must therefore not be judged from a single point of view, but by comprehensively considering specifications and costs.

How To Design Tolerances


In follow content, you will get all the basic information about “How to design tolerance in engineering” and the various terms involved in measuring tolerance.

Calculating Tolerances

There are two main methods of measuring tolerances. As the results of the calculation vary from method to method, the method must be chosen according to the policy of the manufacturing operation. Depending on the company, the two methods are sometimes used in combination, but here we will explain each method.

・The Calculation Method Of Cumulative Worst Value

In this method, the value that differs most from the standard value is added up for all parts. Due to the tighter tolerances, this method has higher manufacturing costs. Therefore, it is suitable for small-scale production.

・Incomplete Compatibility Method

Incomplete compatibility is a method in which tolerances are obtained by summing up the variances. This statistical method is based on the idea that the greater the number of parts manufactured, the lower the probability that the total number of parts will be the worst. Although the required tolerance values are relatively loose, it is suitable for high volume production as it requires normally distributed data.

Considering the manufacturer’s requirements

From the designer’s point of view, we want the tightest possible tolerances to improve the perfection of the product, but from the manufacturing site’s point of view, production costs increase. Even so, if tolerances are relaxed indefinitely, the quality of the product will deteriorate.

It is therefore important to understand the opinions of engineers, for example from the manufacturing side, and then determine the range of tolerances, rather than basing tolerances solely on the opinion of one or the other. By setting a balance between manufacturing costs and perfect tolerances, this will ultimately lead to lower costs.

3D Design For Tolerance


A product design is about visualizing, understanding customer requirements, and what they need in the product. It is the most important stage in the manufacturing process because the actual manufacturing and production really depend on the accuracy of the design. In the manufacturing sector, CNC machining has long been used for fabrication and production. With the advent of technology and computer-aided design software, designing a product may has become easier, however, it has made the design as such more complex than before. In the design stage itself, you need to set the standards for accuracy, precision, and tolerance of the product.

What Is 3DCAD (3D CAD)?

3DCAD is a system that allows product drawings to be created in three dimensions. In traditional 2D CAD, the shape of objects that can be seen from multiple viewpoints (e.g. front view, side view and plan view) is represented in two dimensions. With 3D CAD, however, objects can be examined from a more flexible perspective, as the objects themselves are created in three dimensions.

In addition, 3DCAD allows you to work more efficiently than with manual drawing. For example, if corrections need to be made to a handwritten drawing, only the corrected parts must be carefully erased with an eraser, so some people may experience torn drawings. However, 3D CAD systems allow immediate changes to be made.

In addition, as drawings can be shared as data, they can be worked on efficiently in practice. Another advantage is that the 3D data can be viewed from any angle, making it easy to visualise the finished drawing.

3DCAD And Tolerance Design

When designing with 3D CAD and needing to work with manufacturing, it is necessary to consider tolerance design as 3D as well. however, compared to traditional 2D models, 3D CAD models are influenced by many factors such as part size, contact position and gravity and are therefore difficult to measure manually.

In this case, let us use the tolerance analysis tool available in 3DCAD. With this function, the results of the analysis can be reflected in the model data, making it easier to design to higher tolerances.

Be-cu.com Can Meet Your CNC Machining Needs With High Precision Tolerance


Tolerances are not just variations, they are closely linked to product quality. From the designer’s point of view, tighter tolerances are required in order to maintain quality, but this increases production costs. Conversely, relaxing tolerances may lead to a reduction in quality, which in turn may increase costs.

It is therefore desirable that decisions are made after listening to clarification from both the designer and the manufacturer. Misjudging tolerances can delay development progress, so design tolerances from an early stage. In addition, 3D CAD is increasingly being used for drawing and tools can be used to easily perform tolerance analyses.

Since 3D models contain a large amount of data compared to conventional models, manual calculations are very difficult. Therefore, depending on the software you use, tolerance analysis can be carried out efficiently and at a reduced cost.

Be-cu.com offers more than 30 years of precision machining expertise to companies across a diverse range of industries, including medical devices, firearms, renewable energy and many others. We’ll collaborate with you to develop and implement a customized process that serves your functional requirements and fits your budget. Our goal is to create metal parts with high tolerance, enabling you to improve finished products’ quality, performance and reliability.

Learn more about our cnc machining services and design process and how it can benefit your business. Contact us online for additional information and a no-obligation quote today. You can also email us at [email protected].

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