Machining CNC machining 12 experience summary!


One: How to divide the processing process?

CNC machining process division can generally be carried out according to the following methods:

(1) tool concentration division method is to divide the process according to the tool used, using the same tool to finish processing all the parts that can be completed on the part. In the use of the second tool, the third to complete the other parts they can complete. This can reduce the number of knives compressed empty range when available, reduce unnecessary positioning errors.

(2) to process parts in order method for the processing of many parts, can be divided into several parts according to its structural characteristics, such as internal shape, shape, surface or plane. Generally first processing plane, positioning surface, after processing holes; first processing single geometry, and then processing complex geometry; first processing lower precision parts, and then processing higher precision requirements of the parts

(3) to roughing, finishing sub-sequence method for parts prone to processing deformation, due to the deformation that may occur after roughing and the need for calibration, so generally speaking, where roughing and finishing are to be separated from the process.

In summary, in the division of the process, must be depending on the structure of the parts and process, the function of the machine, the number of parts CNC machining content, the number of times the installation and the production organization of the unit flexible control. Another proposal to use the principle of process concentration or the principle of process dispersion, according to the actual situation to determine, but must strive to rational.

Second: the processing order should be arranged in accordance with what principle?

The arrangement of the machining sequence should be based on the structure of the part and the state of the blank, as well as the need for positioning clamping to consider, the focus is on 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 can not affect the positioning and clamping of the next process, the intermediate Li inserted a general machine tool processing process should also be taken into account.

(2) first inside the shape of the cavity plus process, after the shape of the processing process

(3) to the same positioning, clamping or the same knife processing process is best connected to reduce the number of repeated positioning, the number of tool changes and the number of dynamic platen.

(4) In the same installation of multiple processes, should be arranged first to the workpiece rigidity of the process of small damage.

Three: the workpiece clamping method should pay attention to the determination of those aspects?

In determining the positioning reference and clamping scheme should pay attention to the following three points

(1) strive to design, process, and programming calculations of the benchmark one.

(2) minimize the number of clamping, as far as possible, after a positioning to be able to process all the surfaces to be machined.

(3) Avoid the use of accounting machine manual adjustment program.

(4) fixture to open smoothly, its positioning, clamping mechanism can not affect the processing of the knife (such as the production of collision), encountered in such cases, can be used with the tiger or add the bottom plate to draw the screw way to clamp

Four: how to determine the tooling point is more reasonable? What is the relationship between the workpiece coordinate system and the process coordinate system?

1. tooling point can be located on the machined parts, but note that the tooling point must be the reference position or has been finely machined parts, sometimes after the first process tooling point is destroyed by processing, will lead to the second process and after the tooling point can not be found, so in the first process tooling to pay attention to the positioning of the benchmark has a relatively fixed relationship between the size of the place to set up a relative tooling position, so that according to their relative position between This way, the original tool setting point can be retrieved according to the relative position between them. This relative tool setting position is usually located on the machine table or fixture. The selection principles are as follows

1) Easy to find the correctness.

2) Easy to program.

3) Small error in tool setting.

4) Easy to check during processing.

2. The origin position of the workpiece coordinate system is set by the operator, it is set after the workpiece is clamped, through the tooling to determine, it reflects the distance between the workpiece and the machine zero position relationship. Once the workpiece coordinate system is fixed, generally do not change. Workpiece coordinate system and programming coordinate system both must be unified, that is, in processing, the workpiece coordinate system and programming coordinate system is the same.

Five:How to choose the tool route?

Tool path is the trajectory and direction of the tool relative to the machined part in the process of index control machining. The reasonable selection of the machining route is very important, because it is closely related to the machining accuracy and surface quality of the part. In determining the tool path is to consider the following points:

1) To ensure the machining accuracy of the part

2) To facilitate the numerical calculation and reduce the programming workload.

3) Seeking the shortest machining route, reducing the empty tool time to improve machining efficiency.

4) Minimize the number of program segments.

5) To ensure the roughness of the workpiece contour surface after processing, the final contour should be arranged to be continuously processed by the last tool.

6) Tool in and out (cut in and cut out) route should also be carefully considered to minimize the stopping of the tool at the contour (sudden changes in cutting force caused by unisex deformation) and leave tool marks, but also to avoid vertical undercutting on the contour surface and scratch the workpiece.

Six: How to monitor and adjust during the machining process?

After the workpiece is corrected and the program is adjusted, it can enter the automatic machining stage. In the automatic machining process, the operator should control the cutting process to prevent the quality of the workpiece and other accidents caused by abnormal cutting.

The cutting process control mainly consider the following aspects:

1. machining process procontrol rough machining is mainly considered the workpiece surface of the excess margin of the rapid removal. In the automatic machining process, according to the set cutting amount, the tool automatically cutting according to the predetermined cutting trajectory. At this time, the operator should pay attention to the cutting load table to observe the cutting load changes in the automatic processing process, according to the tool bearing force conditions, adjust the cutting amount, the maximum efficiency of the machine tool.

2. Cutting process cutting sound monitoring in the automatic cutting process, generally start cutting, the tool cutting workpiece sound is stable, continuous, brisk, when the machine tool movement is smooth. As the cutting process proceeds, when there are hard points on the workpiece or tool wear or tool feeding clamps and other reasons, the cutting process appears unstable, unstable performance is a change in the cutting sound, the tool and the workpiece will appear between the sound of mutual impact, the machine will appear vibration. At this time should be timely adjustment of cutting dosage and cutting conditions, when the adjustment effect is not obvious, the machine should be suspended, check the tool and workpiece condition.

3. Finishing process pro-control finishing, mainly to ensure that the workpiece processing feet and processing surface quality, cutting speed is higher, the feed amount is larger. At this time should focus on the impact of chip tumor on the machined surface, for cavity processing, should also pay attention to the corner processing overcut and let the tool. For the above-mentioned to the solution of the problem, one is to pay attention to adjust the spraying position of the cutting fluid, so that the processing surface is always in the best] cooling conditions; secondly, we should pay attention to the quality of the processed surface of the workpiece, by adjusting the cutting with the star, as far as possible to avoid changes in quality. If the adjustment still has no obvious effect, then the original program should be stopped to check whether the program is reasonable.

Special attention should be paid to the position of the tool when pausing to check or stopping to check. If the tool is stopped during cutting, the sudden spindle stop will cause tool marks on the surface of the workpiece. Generally, stopping should be considered when the tool leaves the cutting state.

4. Tool monitoring tool quality star largely determines the quality star of the workpiece processing. In the automatic machining cutting process, the tool should be monitored by sound, cutting time control, cutting process stop check, workpiece surface analysis and other methods to determine the normal grinding of the tool to mention the condition and abnormal broken condition. According to the processing requirements, the tool should be processed in time to prevent the occurrence of processing quality problems arising from the tool not being processed in time.

Seven: How to reasonably choose the processing tool? Cutting dosage has several elements? There are several materials of the tool? How to determine the speed of the tool, cutting speed, cutting degree?

1. When milling the plane, you should choose not to resharpen the carbide end mill or end mill. When milling in general, try to use the second tooling processing, the first tooling is best to use the end mill rough milling, continuous tooling along the surface of the workpiece. Each time the tool is recommended to be 60-75% of the diameter of the tool.

2. End mills and end mills with carbide inserts are mainly used for processing tabs, recesses and box mouth surfaces.

3. Ball cutters, garden cutters (also known as nose cutters) are commonly used for processing curved surfaces and variable bevel profile shapes. And the ball cutter is mostly used for semi-finishing and finishing. Town carbide tool member knife is mostly used to open rough.

Eight: What is the role of machining program list? What should be included in the machining program sheet?

(A) machining program list is the content of the CNC machining process design ー, is also required to comply with the operator, the implementation of the protocol, is a specific description of the processing procedures, the purpose is to allow the operator to clarify the content of the program, clamping and positioning, the processing procedures selected by the tool should pay attention to both the problem.

(B) in the processing program list, should include: drawing and programming file name, workpiece name, clamping sketch, program name, each program used by the tool, the maximum depth of cut, the nature of processing (such as roughing or finishing), theoretical processing time, etc..

Nine: CNC programming before what to do to prepare?

After determining the processing process, before programming to understand: 

1, the workpiece clamping:

2, the size of the workpiece blanks - in order to determine the scope of processing or whether the need for multiple clamping 

3, the workpiece material - in order to choose what kind of tool used for processing; 

4, what are the tools in stock - to avoid the absence of this tool to modify the program during processing, if the tool must be used, it can be prepared in advance.

Ten: What is the principle of setting the safety height in programming?

A: The principle of setting the safety height: generally higher than the highest surface of the island. Or the programming zero point is set at the highest surface, so that you can also minimize the risk of collision with the tool.

Eleven:After the tool path is programmed, why do I have to do post-processing?

Because different machine tools recognize different address codes and NC program formats, so you have to choose the correct post-processing format for the machine you are using.

The correct post-processing format must be chosen for the machine used to ensure that the program can be run.

Twelve:What is DNC communication?

Program delivery can be divided into CN and DNC, CNC refers to the program through the media media (such as floppy disk, read

The CNC refers to the program through the media media (such as floppy disk, readout, communication line, etc.) to the machine memory storage, processing from the memory to call out the program for processing. Because the memory capacity is limited by the size, so when the program is large, you can use the DNC method to add, because the DNC processing machine directly from the control computer to read the program (that is, while sending to do), so the capacity of the memory is not limited by the size of the cutting amount has three major elements: depth of cut, spindle speed and feed rate.

The overall principle of cutting amount selection is less cutting fast feed (i.e., small depth of cut feed speed)

According to the material classification tools are generally divided into ordinary hard white steel tools (materials for high-speed steel coated tools (such as titanium, etc.) alloy tools (such as tungsten steel nitriding tools, etc.)