F.A.Q about NC processing procedures


5Q: How to choose the cutting route?

Tool path refers to the path and direction of the tool relative to the workpiece in the process of NC machining. The reasonable choice of machining route is very important, because it is closely related to the machining accuracy and surface quality of parts. The following points are mainly considered when determining the tool path:

1) Ensure the machining accuracy requirements of parts.

2) It is convenient for numerical calculation and reduces programming workload.

3) Find the shortest processing route, reduce the empty tool time to improve the processing efficiency.

4) Minimize the number of program segments.

5) Ensure the roughness requirements of the workpiece contour surface after machining. The final contour shall be processed continuously with the last cutter.

6) The advance and retreat (cut in and cut out) route of the tool shall also be carefully considered to minimize the tool marks caused by tool stopping at the contour (elastic deformation caused by sudden change of cutting force), and also to avoid scratching the workpiece due to vertical cutting on the contour surface.

6Q: How to monitor and adjust during processing?

The workpiece can enter the automatic processing stage after the alignment and program debugging are completed. In the automatic machining process, the operator shall monitor the cutting process to prevent the workpiece quality problems and other accidents caused by abnormal cutting.

The monitoring of cutting process mainly considers the following aspects:

1. The monitoring of the machining process is mainly concerned with the rapid removal of the surplus allowance on the workpiece surface. In the automatic machining process of the machine tool, the tool automatically cuts according to the predetermined cutting path according to the set cutting parameters. At this time, the operator should observe the change of cutting load during automatic processing through the cutting load table, and adjust the cutting parameters according to the bearing force of the tool to maximize the efficiency of the machine tool.

2. Monitoring of cutting sound in the cutting process In the automatic cutting process, the sound of the tool cutting workpiece is stable, continuous, and light when cutting is generally started, and the movement of the machine tool is stable. With the progress of the cutting process, when there are hard spots on the workpiece or the tool is worn or the tool is clamped, the cutting process becomes unstable. The unstable performance is that the cutting sound changes, the tool and the workpiece will collide with each other, and the machine tool will vibrate. At this time, the cutting parameters and cutting conditions should be adjusted in time. When the adjustment effect is not obvious, the machine tool should be paused to check the condition of the tool and workpiece.

3. The finishing process is monitored to ensure the machining size and surface quality of the workpiece. The cutting speed is high and the feed rate is large. At this time, attention should be paid to the influence of chip buildup on the machined surface. For cavity machining, attention should also be paid to over cutting and tool passing at corners. To solve the above problems, first, pay attention to adjusting the spraying position of cutting fluid, so that the machined surface is always in the best cooling condition; Second, pay attention to the quality of the machined surface of the workpiece, and try to avoid quality changes by adjusting the cutting parameters. If the adjustment still has no obvious effect, stop the machine to check whether the original program is reasonable.

In particular, pay attention to the position of the tool when suspending inspection or stopping inspection. If the tool stops in the cutting process and the spindle stops suddenly, tool marks will be generated on the workpiece surface. In general, shutdown shall be considered when the tool leaves the cutting state.

4. The quality of the tool monitoring tool largely determines the processing quality of the workpiece. In the process of automatic machining and cutting, it is necessary to judge the normal wear condition and abnormal damage condition of tools by means of sound monitoring, cutting time control, pause inspection during cutting, workpiece surface analysis, etc. Tools shall be handled in time according to the processing requirements to prevent the processing quality problems caused by the tools not being handled in time.

7Q: How to reasonably select the machining tool? How many elements are there in the cutting parameters? How many materials are there? How to determine the tool speed, cutting speed, cutting width?

1. The carbide end milling cutter or end milling cutter without regrinding shall be selected for plane milling. In general milling, try to use the second tool path for processing. The first tool path is better to use the end milling cutter for rough milling, and the tool path is continuous along the workpiece surface. The recommended width of each tool path is 60% - 75% of the tool diameter.

2. End milling cutter and end milling cutter with carbide insert are mainly used to process boss, groove and box mouth surface.

3. Ball knife and round knife (also known as round nose knife) are commonly used to process curved surfaces and variable angle contour shapes. The ball cutter is mostly used for semi finishing and finishing. The round cutters with carbide inserts are mostly used for roughening.

8Q: What is the function of the processing program sheet? What should be included in the processing program sheet?

Answer: (I) The processing program list is one of the contents of the NC processing process design, is also a procedure that needs to be observed and implemented by the operator, and is a specific description of the processing program. The purpose is to let the operator know the content of the program, the clamping and positioning methods, and the problems that should be paid attention to when selecting the tools for each processing program.

(2) In the processing program list, it shall include: drawing and programming file name, workpiece name, clamping sketch, program name, tool used in each program, maximum depth of cutting, processing nature (such as rough machining or finish machining), theoretical processing time, etc.