20 years of CNC machining practice, 12 experience summaries


CNC machining, also called CNC machining, refers to machining with CNC machining tools. Because CNC machining is programmed and controlled by a computer, CNC machining has the advantages of stable machining quality, high machining accuracy, high repeatability, complex surface machining, and high machining efficiency. In the actual processing process, human factors and operating experience will affect the final processing quality to a large extent. Let’s take a look, one with twenty CNC machining experience in the old master , summed up twelve valuable experience ….

 

How to divide the processing procedure?

The division of CNC machining processes can generally be carried out according to the following methods:

 

 

What principles should be followed in the arrangement of processing sequence?

The arrangement of the processing sequence should be considered according to the structure of the part and the condition of the blank, as well as the needs of positioning and clamping. The important point is that the rigidity of the workpiece is not destroyed. The sequence should generally be carried out according to the following principles:

  1. The processing of the previous process should not affect the positioning and clamping of the next process, and the processing of general machine tools should also be considered comprehensively.
  2.  Carry out the inner cavity adding procedure first, and then the contour processing procedure.
  3. It is best to connect the processes of processing with the same positioning, clamping method or the same tool to reduce the number of repeated positioning, the number of tool changes and the number of moving the platen.
  4. For the multiple processes carried out in the same installation, the process should be arranged with less rigid damage to the workpiece.

 

Which aspects should be paid attention to when determining the clamping method of the workpiece ?

The following three points should be paid attention to when determining the positioning datum and clamping plan:

  1. Strive to unify the design, technology, and programming calculation datum.
  2. Minimize the number of clamping times , and try to achieve all the surfaces to be processed after one positioning.
  3. Avoid using manual adjustment schemes.
  4. The fixture should be opened smoothly, and its positioning and clamping mechanism should not affect the cutting during processing (such as a collision). When encountering such a situation, use a vise or add a bottom plate to draw a screw.

 

How to determine the tool setting point is more reasonable?

What is the relationship between the workpiece coordinate system and the programming coordinate system?

1) It is easy to align .
2) Easy to program.
3) The tool setting error is small.
4) Convenient and checkable inspection during processing.

 

How to choose the knife route?

The path of the tool is the path and direction of the tool relative to the workpiece in the index control process. The reasonable choice of processing route is very important, because it is closely related to the processing accuracy and surface quality of the parts . In determining the path of the tool, the following points are mainly considered:

  1. Ensure the machining accuracy requirements of the parts.
  2. Convenient numerical calculation and reduce programming workload.
  3. Seek the shortest processing route, reduce the empty tool time to improve processing efficiency.
  4. Minimize the number of program segments.
  5. To ensure the roughness requirements of the workpiece contour surface after processing, the final contour should be processed continuously in the last pass.
  6. The advance and retreat (cut-in and cut-out) route of the tool should also be carefully considered to minimize the tool stop at the contour (a sudden change in cutting force causes elastic deformation) and leave tool marks, and also avoid vertical downward on the contour surface Knife and scratch the workpiece.

 

How to monitor and adjust during processing?

After the workpiece is aligned and the program is debugged, it can enter the automatic processing stage. In the automatic machining process, the operator should monitor the cutting process to prevent abnormal cutting from causing workpiece quality problems and other accidents. The monitoring of the cutting process mainly considers the following aspects:

 

How to choose processing tools reasonably?

What are the major elements of cutting amount? How many kinds of materials are available? How to determine the speed, cutting speed and cutting width of the tool?

 

What is the function of the processing procedure sheet?

What should be included in the processing procedure sheet?

 

 

What preparations should be made before CNC programming?

After determining the processing technology, you must understand before programming:

 

  1. Workpiece clamping method ;
  2. The size of the workpiece blank—-in order to determine the processing range or whether multiple clamping is required;
  3. The material of the work piece — -In order to choose which tool to use for processing;
  4. Which tools are in stock-avoid modifying the program during processing because there is no such tool. If you must use this tool, you can prepare in advance.

 

What are the principles for setting the safety height in programming?

The principle of setting safety height: generally higher than the highest surface of the island. Or set the programmed zero point on the highest surface, so that the risk of knife collision can be avoided to the greatest extent .

 

After the tool path is compiled, why post-processing is necessary?

Because the address code and NC program format that can be recognized by different machine tools are different, the correct post-processing format must be selected for the machine tool used to ensure that the compiled program can run.

 

What is DNC communication?

The way of program delivery can be divided into CNC and DNC. CNC means that the program is delivered to the memory of the machine tool through media media (such as floppy disk, tape reader , communication line, etc.) for storage, and the program is called from the memory during processing. Processing. Because the memory capacity is limited by the size, when the program is large, the DNC method can be used for processing. Because the machine tool directly reads the program from the control computer during DNC processing (that is, it is done while sending), it is not affected by the memory capacity Limited by size.

  1. There are three major elements of cutting parameters: depth of cut, spindle speed and feed rate . The general principle of selecting cutting parameters is: less cutting, fast feed (that is, the cutting depth is small, and the feed speed is fast)
  2. Classified by material, tool Generally divided into ordinary hard white steel knives (material is high-speed steel), coated knives (such as titanium plating, etc.), alloy knives (such as tungsten steel, boron nitride knives, etc.).
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