The Importance of Machining Tolerances in Manufacturing
In the field of mechanical manufacturing, tolerance matching is a rigorous and complex task, which requires mechanical designers and manufacturers to pay great attention to it. Nowadays, everyone has very high requirements for product quality, so in the product manufacturing process, standard processing tolerance is an important parameter that must be considered, which can ensure that the product remains consistent on a micro scale.
1、Definition of machining tolerance
Machining tolerance refers to the range of geometric parameters allowed to vary during machining. It indicates the requirements for part manufacturing accuracy and reflects the difficulty of machining. Generally speaking, the smaller the tolerance value, the higher the accuracy of the part. However, in actual operation, there is no perfect process. Even if modern manufacturing technology has reduced the tolerance value as much as possible, it can never reach zero.
2、Terms related to tolerance calculation
1.Linear dimensions
It is mainly divided into two categories: linear dimensions and angular dimensions. Among them, linear dimensions are the distance between two points, such as diameter, width, height, depth, thickness, and center distance.
2.Nominal dimensions
The nominal dimensions are the dimensions determined during design.
3.Limiting sizes
The limiting dimensions are the two extreme values of the allowable dimensions of a hole or shaft. The larger limit value is called the upper limit dimension (Dmax), and the smaller one is the minimum dimension (Dmin).
4.Actual size
The actual size is the dimension measured after the part is processed. Because there will be errors during measurement, the actual size measured is not the real size. The nominal size and limit size are given during design, and the actual size is between the upper limit dimension and the lower limit dimension.
5.Dimensional deviation
Dimensional deviation is the algebraic difference between a certain dimension (such as the limit dimension, actual dimension) and the nominal dimension. This algebraic difference can be positive, negative, or zero, and the deviation value must be preceded by a positive or negative sign. Deviation is divided into limit deviation and actual deviation.
Upper limit deviation = upper limit dimension – nominal dimension
Lower limit deviation = lower limit dimension – nominal dimension.
6.Dimension tolerance
Dimension tolerance t (that is, the variation range of qualified actual dimension) = upper limit tolerance dimension – lower limit tolerance dimension. Because the upper limit dimension (deviation) is always larger than the lower limit dimension (deviation), the tolerance is an unsigned number and cannot be negative or zero.
3、Types of Tolerance
1.Dimensional tolerance
The allowable change in size is the absolute value of the algebraic difference between the maximum limit size and the minimum limit size.
2.Shape tolerance
The sum of the allowable changes in the shape of a single actual element, including straightness, flatness, roundness, cylindricity, line profile and surface profile.
3.Position tolerance
The sum of the allowable changes in the position of the relevant actual elements relative to the reference. It can limit the relative position relationship between two or more points, lines and surfaces of a part, including parallelism, verticality, inclination, coaxiality, symmetry, position, circular runout and total runout.
4、Points to note when using tolerance
When dealing with tolerances, if you plan well in advance, you can effectively utilize resources, reduce the error rate of finished products, and greatly improve work efficiency. Although tolerances can directly reflect the accuracy of products, the smaller the better. Because the smaller the product accuracy, the higher the cost. And the tolerance of parts must be determined according to the actual needs of the parts. For example, some craft parts are mainly used for beauty, so the tolerance accuracy can be reduced to reduce costs. But for spare parts that require secondary assembly, strict tolerances must be used. If the tolerance is too large, it may lead to assembly failure and cause unnecessary losses.
When controlling strict tolerances, pay special attention to the following points:
1.Cost
Draw a relationship diagram between cost increase and tolerance reduction based on the prototype and usage of the designed parts, find the critical value that meets the acceptable range of the specific project, and then use the minimum tolerance that fits the budget. 2. Inspection
After the product is completed, it enters the quality inspection stage, which is to judge whether the final product is qualified or not. If it is unqualified, it will be rejected. Depending on the strictness of the tolerance, the time of the quality inspection stage is different. The stricter the tolerance, the higher the time cost and the more complex the inspection equipment required.
2.Processing technology and methods
Different processing technologies require different mechanical equipment, and the impact on the tolerance of parts is also obvious. Some parts need to be processed through many different machines and equipment, so you have to understand the tolerance levels of different machines in detail and adjust the processing sequence in a planned way to effectively control the tolerance of the finished product.
3.Surface roughness
The surface of all products has roughness distortion, and the roughness of different materials is different. So when choosing the strict tolerance of CNC processing, you have to keep in mind the existing surface roughness. If you aim for strict tolerances, a rough surface will cause a lot of trouble.
5、Conclusion
In short, machining tolerance is of great significance in the manufacturing industry. It is related to the quality and consistency of the product, and each part affects every link of production. Only by correctly understanding and controlling machining tolerances can we ensure quality while taking into account cost and efficiency, and achieve sustainable development of the manufacturing industry.
If you need to manufacture custom parts with reasonable tolerances, Xavier is undoubtedly your ideal choice for finding a custom processing manufacturer. Xavier CNC machining service has a professional team and advanced equipment, which can not only provide the best tolerance solution, but also implement it in production. It can display the design prototype and control the precision quality from design to production. Here, you can not only get the best tolerance solution recommended by professionals, but also rely on advanced equipment to implement it in production. Feel free to contact us to communicate your processing needs.