- (1) The size data on the part drawing should conform to the principle of convenient programming
1. The dimensioning method on the part drawing should be adapted to the characteristics of CNC machining online quote. On the CNC machining part drawing, the size should be quoted on the same basis or the coordinate size should be directly given. This marking method is not only convenient for programming, but also convenient for mutual coordination between dimensions, and brings great convenience in maintaining the consistency of design benchmarks, process benchmarks, inspection benchmarks and programming origin settings. As part designers generally consider assembly and other use characteristics in dimensioning, they have to adopt a locally dispersed marking method
2. This will bring a lot of inconvenience to process arrangement and numerical control machining. Due to the high precision of CNC machining online quote and repeated positioning, there will be no
3. Large accumulated errors will destroy the use characteristics, so the local scattered labeling method can be changed to the same datum citation size or the coordinate size labeling method directly.
4. The conditions of the geometric elements constituting the contour of the part should be sufficient to calculate the base point or node coordinates during manual programming.
During automatic programming, all geometric elements constituting the contour of the part must be defined. Therefore, when analyzing the part drawing, it is necessary to analyze whether the given conditions of the geometric elements are sufficient. For example, the arc and the straight line, the arc and the arc are tangent on the drawing, but according to the size given on the drawing, when calculating the tangent condition, it becomes the state of intersection or separation. Due to the insufficient conditions of the geometric elements of the components, it is impossible to start programming. When encountering this situation, it should be resolved through consultation with the part designer.
- (2) The structure and craftsmanship of each machining part of the part should meet the characteristics of CNC machining online quote
1) It is better to adopt uniform geometric types and dimensions for the cavity and shape of parts. This can reduce the tool specifications and the number of tool changes, make programming easier, and improve production efficiency.
2) The fillet size of the inner groove determines the diameter of the tool, so the fillet radius of the inner groove should not be too small. The quality of the part manufacturability is related to the height of the processed contour and the size of the transition arc radius.
3) When milling the bottom surface of the part, the fillet radius r of the groove bottom should not be too large.
4) A unified reference positioning should be used. In CNC machining, if there is no unified reference positioning, the contour position and size of the two faces after machining will be inconsistent due to the reinstallation of the workpiece. Therefore, to avoid the above problems and ensure the accuracy of the relative position after the two clamping processes, a unified reference positioning should be adopted.
It is better to have suitable holes on the parts as the positioning reference holes. If not, set the process holes as the positioning reference holes (such as adding process lugs on the blank or setting process holes on the margin to be milled in the subsequent process). If the craft hole cannot be made, at least the finished surface should be used as a unified reference to reduce the error caused by the two clamping.
In addition, it is necessary to analyze whether the required machining accuracy and dimensional tolerances of the parts can be guaranteed, whether there are redundant dimensions that cause contradictions or closed dimensions that affect the process arrangement.