12 experience summaries of CNC machining

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

(1). The tool centralized sorting method is to divide the process according to the tools used, and use the same tool to CNC machine all the parts that can be completed. Use the second knife and the third knife to finish other parts they can finish. This can reduce the number of tool changes, compress idle time and reduce unnecessary positioning errors.

(2). Using the processing part sorting method, for parts with a lot of Cnc Processing content, the processing part can be divided into several parts according to their structural characteristics, such as inner shape, outer shape, curved surface or plane, etc. Generally, planes and positioning surfaces are processed first, and then holes are processed; simple geometric shapes are processed first, and then complex geometric shapes are processed; parts with lower precision are processed first, and then parts with higher precision requirements are processed.

(3). Use the rough and fine CNC machining sequence method. For parts that are prone to CNC machining deformation, they need to be calibrated due to possible deformation after rough machining . Therefore, generally speaking, the processes must be separated for rough and fine machining. To sum up, when dividing the process, we must consider the structure and craftsmanship of the part, the function of the machine tool, the amount of CNC machining content of the part, the number of installations and the production organization status of the unit. It is also recommended to adopt the principle of process concentration or decentralization, which should be determined according to the actual situation, but it must be reasonable.

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 need for positioning and clamping. The key point is that the rigidity of the workpiece isn’t destroyed. The sequence should generally be carried out according to the following principles:

(1). The CNC machining of the previous process can't affect the positioning and clamping of the next process. Comprehensive consideration must also be given to general machine tool processing processes interspersed in the middle.

(2). Carry out the inner shape and cavity processing first, and then the outer shape processing.

(3). CNC machining processes with the same positioning, clamping method or the same tool are best carried out in succession to reduce the number of repeated positioning, tool changes and platen movements.

(4). For multiple processes carried out in the same installation, the process that will cause less rigid damage to the workpiece should be arranged first.

The following three points should be noted when determining the positioning reference and clamping plan:

(1). Strive to unify the benchmarks of design, technology, and programming calculations.

(2). Minimize the number of clampings and try to CNC machine all the surfaces to be processed in one positioning.

(3). Avoid using machine-occupied manual adjustment solutions.

(4). The clamp should be smooth, and its positioning and clamping mechanism shouldn’t affect the tool movement during CNC machining . When encountering such a situation, clamping can be done with a vise or by adding screws to the bottom plate.

(1). The tool setting point can be set on the part being processed, but note that the tool setting point must be a datum position or a part that has been finished. Sometimes the tool setting point is destroyed by CNC machining after the first process, which will result in the second process and subsequent tool setting points being unable to be found. selection principles: a, Easy to find; b, Programming is convenient; c, The tool setting error is small; d, Inspection during processing is convenient and traceable.

(2). The origin position of the workpiece coordinate system is set by the operator himself. The workpiece coordinate system and the programming coordinate system must be unified.

The tool path refers to the movement trajectory and direction of the tool relative to the workpiece. Considerations:

(1). Ensure the processing accuracy requirements of parts.

(2). Facilitate numerical calculation and reduce programming workload.

(3). Seek the shortest CNC machining route and reduce the empty tool time.

(4). Reduce the number of program segments as much as possible.

(5). The final contour should be processed continuously in the last pass.

(6). The advance and retreat routes must be carefully considered to minimize tool marks or scratching the workpiece.

During the automatic machining process, the operator must monitor:

(1). Process monitoring: Observe the cutting load changes and adjust the cutting amount according to the bearing capacity of the tool.

(2). Monitoring of cutting sounds: Changes in sound indicate hard spots, tool wear, or clamping issues. Adjust or stop to check.

(3). Monitor the finishing process: Ensure surface quality. Pay attention to overcutting and tool yielding in corners. Adjust cutting fluid spray and cutting amount. Avoid spindle stops during cutting to prevent marks.

(4). Tool monitoring: Normal wear and abnormal damage must be determined through sound, time control, and surface analysis. Tools must be processed in a timely manner.

(1). Non-regrinding carbide end mills should be used for surface milling. Width of each pass: 60%--75% of tool diameter.

(2). Carbide insert face mills are for bosses, grooves and box openings.

(3). Ball cutters and round cutters are for curved surfaces. Ball cutters for finishing; round knives for roughening.

(1). The machining process sheet is key to CNC machining process design. It helps the operator understand program content, clamping, and tools.

(2). Content: drawing/file names, workpiece names, clamping sketches, program names, tools, max depth, processing properties, theoretical time, etc.

(1). Workpiece clamping method;

(2). The size of the workpiece blank;

(3). The material of the workpiece;

(4). What tools are in stock?

Higher than the highest surface of the island feature to minimize tool collision risk.

To convert program formats to specific address codes recognized by different machine tools.

DNC is used when the program is large; the machine tool reads directly from the computer, so memory capacity isn't limited.

(1). Three major factors: cutting depth, spindle speed and feed speed. Principle: less cutting, fast feed.

(2). Knife materials: hard white steel (high-speed steel), coated knives (titanium), and alloy knives (tungsten steel, boron nitride).