Designing Tolerance Chart and Process for CNC Machining Parts

Document Type: Research Paper


Assistant Prof. of Mechanical engineering, Eghlid Branch, Islamic Azad University,


The map and the model designed by a designer and presented to a manufacturer in the form of a map is the result of his knowledge and innovation. The manufacturer, in turn, uses his best effort to produce a part accordingly. However, because of production problems and raw material, producing a precise part is very difficult and costly. One of the most important problems in this regard is designing the production process and tolerances for each stage in order to determine the final tolerance for the part. The solution to this problem lies in deciding on the priority of stages of operation and using tolerance chart. Selecting stages of machining and effective parameters like the depth of machining is important. Each stage of machining has its own tolerance, and in the end, when all tolerances are added up, the final tolerance might be more than the permitted assigned tolerance on the map. To prevent cumulative tolerance and reduce the production waste, it is necessary to decide on the tolerances for each stage (tolerance chart). Using software systems for this purpose not only increases speed and precision significantly but also reduces expenses to a large extent. A software has been designed for determing stages of machining and permitted tolerance for each operation (tolerance chart), and its efficiency is demonstrated in this article by using an example.