How does Dongguan CNC Precision Machining Factory calculate the process dimensions and tolerances when the benchmarks overlap

How does Dongguan CNC Precision Machining Factory calculate the dimensions and tolerances when the benchmarks overlap? When the process benchmark, measurement benchmark, positioning benchmark, or programming origin coincides with the design benchmark, the process size and its tolerance are directly determined by the machining allowance and achievable accuracy of each process. The calculation method is to start from the last process and calculate forward, with the specific steps as follows:

1. Determine the total blank allowance and process allowance.

2. Determine process tolerances. The final process dimensional tolerance is equal to the design dimensional tolerance on the part drawing, while the other process dimensional tolerances are determined based on economic accuracy.

3. Calculate the basic dimensions of the process. Starting from the design dimensions on the part drawing, calculate forward until the blank size is reached. The basic dimensions of the final process are equal to the basic dimensions on the part drawing, while the basic dimensions of other processes are equal to the basic dimensions of the subsequent process plus or minus the margin of the subsequent process.

4. Mark the dimensional tolerance of the process. The tolerance of the final process at Dongguan CNC Precision Machining Factory is marked according to the design dimensions on the part drawing, the tolerance of the intermediate process dimensions is marked according to the "insertion principle", and the tolerance of the blank dimensions is marked in both directions.