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Technological Analysis of CNC Machined Parts

The technological analysis of CNC machining involves a wide range of aspects, and here we only analyze the possibility and convenience of CNC machining.

Ⅰ. The dimensional data given on the drawing of CNC machined parts 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

On the CNC machining part drawing, the dimensions should be quoted on the same datum or the coordinate dimensions should be given directly. This labeling method is not only convenient for programming, but also facilitates the coordination between dimensions, which brings great convenience in maintaining the consistency of design benchmarks, process benchmarks, detection benchmarks and programming origin settings.

Because the designers of CNC machined parts generally add V cores in dimensioning, considering the use characteristics of assembly and other aspects, they have to adopt a partially scattered labeling method, which will bring a lot of inconvenience to process arrangement and CNC machining.

Due to the high precision of CNC machining and repeated positioning, the use characteristics will not be destroyed due to large accumulated errors. Therefore, the local scattered annotation method can be changed to a unified reference citation size or a method of directly giving coordinate dimensions.

2. The conditions of the geometric elements constituting the outline of the part should be sufficient

The base point or node coordinates are calculated during manual programming. During automatic programming, all geometric elements that make up the contour of the CNC machined part are defined.

Therefore, when analyzing the part drawing, it is necessary to analyze whether the given conditions of the geometric elements are sufficient. For example, arc and straight line, arc and arc are tangent on the drawing, but according to the size given in the figure, when calculating the tangent condition, it becomes the state of intersection or separation.

Due to the insufficient conditions of geometric elements constituting CNC machined parts, it is impossible to start programming. When this happens, it should be resolved through consultation with the part designer.

Ⅱ. The structural manufacturability of each processing part of CNC machined parts should conform to the characteristics of CNC machining

1. The inner cavity and shape of the part should preferably adopt a unified geometric type and size. In this way, the tool specification and the number of tool changes can be reduced, the programming is convenient, and the production efficiency is improved.

2. The size of the inner groove fillet determines the size of the tool diameter, so the radius of the inner groove fillet should not be too small. The quality of the part's manufacturability is related to the height of the contour to be processed, the size of the radius of the transfer arc, etc.

3. When milling the bottom plane of CNC machined parts, the fillet radius r of the groove bottom should not be too large.

4. A unified datum positioning should be adopted. In CNC machining, if there is no unified datum positioning, the position and size of the contours on the two surfaces after machining will be uncoordinated due to the re-installation of the workpiece. Therefore, in order to avoid the occurrence of the above problems and ensure the accuracy of the relative position after two clamping processing, a unified reference positioning should be adopted.

There are suitable holes on the CNC machined parts as the positioning reference holes. If not, the process holes should be set as the positioning reference holes (such as adding process lugs on the blank or setting process holes on the allowance to be milled in the subsequent process).

If the process 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 should also be analyzed whether the required machining accuracy and dimensional tolerance of the parts can be guaranteed, whether there are redundant dimensions that cause contradictions or closed dimensions that affect the process arrangement.

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