12 Pieces of Unmissable CNC Machining Experience

Due to the complexity of CNC machining (such as different machine tools, different materials, different tools, different cutting methods, different parameter settings, etc.), it is determined from engaging in CNC machining (whether machining or programming) to reach a certain level A relatively long period of time must be passed. This manual is a summary of some experience with CNC machining technology, procedures, selection of commonly used tool parameters, monitoring during processing, etc., summarized by CNC machining experts in the long-term actual production process. For reference.

1. Question: How to Divide the CNC Machining Process?

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

(1) The tool centralized ordering method is to divide the processes according to the tools used and use the same tool to machine all the custom cnc parts that can be completed on the custom cnc part. Use the second knife and the third knife to complete other CNC machining parts they can complete. This can reduce the number of tool changes, reduce idle time, and reduce unnecessary positioning errors.

(2) With the CNC machining parts ordering method, for precision cnc machining parts with a lot of processing content, the processing cnc precision part can be divided into several precision cnc machining parts according to its structural characteristics, such as internal shape, shape, curved surface or plane. Generally, the plane and positioning surface is processed first, and then the hole is processed; the simple geometric shape is processed first, and then the complex geometric shape is processed; the cnc metal parts with lower precision are processed first, and then the parts with higher precision requirements are processed.

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(3) For custom cnc machining parts that are prone to processing deformation by the rough and CNC machining sorting method, due to the deformation that may occur after rough machining, the shape needs to be corrected. Therefore, in general, all the processes that need to be rough and CNC machining must be separated.

In summary, when dividing the process, we must flexibly grasp the structure and manufacturability of the custom cnc parts, the function of the machine tool, the number of parts CNC machining content, the number of installations, and the production organization of the unit. It is also recommended to adopt the principle of process concentration or the principle of process dispersion, which should be determined according to the actual situation, but must strive to be reasonable.

2. Question: What Principles Should be Followed in the Arrangement of the Processing Sequence?

Answer: 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 important point is that the rigidity of the workpiece is not destroyed. The order should generally be carried out according to the following principles:

(1) The processing of the previous process cannot affect the positioning and clamping of the next process, and the general machine tool processing processes should also be considered comprehensively.

(2) Carry out the inner cavity adding process first, and then the outer shape CNC machining process.

(3) It is best to connect the processes of CNC machining with the same positioning, clamping method, or the same tool to reduce the number of repeated positioning, tool changes, and the number of times moving the platen.

(4) For the multiple procedures carried out in the same installation, the procedure should first be arranged with less rigid damage to the workpiece.

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3. Question: Which Aspects Should Be Paid Attention to When Determining the Clamping Method of the Workpiece?

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

(1) Strive to unify the design, process, and programming calculation benchmarks.

(2) Minimize the number of clamping times, as far as possible to be able to process 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 knife during processing (such as collision). In such a situation, use a vise or add a bottom plate to draw a screw.

4. Question: How to Determine Whether the Tool Setting Point is More Reasonable? What is the Relationship Between the Workpiece Coordinate System and the Programming Coordinate System?

① The tool setting point can be set on the cnc machining part to be processed, but note that the tool setting point must be the reference position or the position that has been CNC machined. Sometimes the tool setting point is destroyed after the first process, which will cause the second process and there is no way to find the subsequent tool setting points. Therefore, in the first process of the toolset, pay attention to setting up a relative tool setting position where there is a relatively fixed size relationship with the positioning datum so that the original position can be retrieved according to the relative position relationship between them. Knifepoint. This relative tool setting position is usually set on the machine tool table or fixture. The selection principles are as follows:

1) Easy to align.

2) Easy to program.

3) The tool setting error is small.

4) It is convenient to check during processing.

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②The origin position of the precision cnc machining parts coordinate system is set by the operator. It is determined by tool setting after the precision cnc machining parts are clamped. It reflects the distance position relationship between the precision cnc machining parts and the machine zero point. Once the precision cnc machining parts coordinate system is fixed, it is generally not changed. The precision cnc machining parts coordinate system and the programming coordinate system must be unified, that is, the workpiece coordinate system and the programming coordinate system are consistent during processing.

5. Question: How to Choose the Knife Route?

Answer: 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 the processing route is very important because it is closely related to the processing accuracy and surface quality of the cnc precision parts. When determining the path of the knife, the following points are mainly considered:

1) Ensure the machining accuracy requirements of the cnc precision parts.

2) Convenient numerical calculation and reduce programming workload.

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

4) Try to reduce the number of blocks.

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 stops at the contour (a sudden change in cutting force causes elastic deformation) and leave tool marks, and avoid vertical downward on the contour surface Knife and scratch the workpiece.

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6. Question: How to Monitor and Adjust During Processing?

Answer: After the custom cnc parts are aligned and the program is debugged, it can enter the automatic processing stage. In the automatic CNC machining process, the operator should monitor the CNC cutting process to prevent the abnormal cutting from causing custom cnc parts quality problems and other accidents.

The following aspects are mainly considered for monitoring the CNC cutting process:

①The main consideration of the CNC machining process monitoring rough machining is the rapid removal of the excess margin on the surface of the workpiece. In the automatic CNC machining process of the machine tool, according to the set CNC cutting amount, the tool automatically cuts according to the predetermined CNC cutting path. At this time, the operator should pay attention to observing the CNC cutting load changes in the automatic CNC machining process through the CNC cutting load table, and adjust the CNC cutting amount according to the bearing capacity of the tool to maximize the efficiency of the machine tool.

②Monitoring of cutting sound during cutting in the automatic CNC cutting process, generally when cutting is started, the sound of the tool cutting the precision cnc machined parts is stable, continuous, and brisk. At this time, the movement of the machine tool is stable. As the CNC cutting process progresses, when there are hard spots on the precision cnc machining parts, tool wear, or tool clamping, the CNC cutting process becomes unstable. The unstable performance is that the cutting sound changes, and the tool and the precision cnc machining parts will collide with each other. Sound, the machine tool will vibrate. At this time, the CNC cutting amount and cutting conditions should be adjusted in time. When the adjustment effect is not obvious, the machine tool should be suspended to check the condition of the tool and precision cnc machined parts.

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③ Finishing process monitoring and finishing are mainly to ensure the processing size and surface quality of the precision cnc machined parts, the cutting speed is high, and the feed rate is large. At this time, attention should be paid to the impact of built-up edge on the machined surface. For cavity machining, attention should also be paid to over-cutting and cutting at corners. To solve the above problems, one is to pay attention to adjusting the spray position of the cutting fluid so that the machined surface is always in the best cooling condition; the second is to pay attention to the quality of the machined surface of the custom cnc parts and adjust the cutting amount to avoid as much as possible. Changes in quality. If the adjustment still has no obvious effect, the machine should be shut down to check whether the original program is reasonable.

Special attention should be paid to the position of the tool when the inspection is suspended or stopped. If the tool stops during the CNC cutting process, a sudden stop of the spindle will cause tool marks on the surface of the custom cnc parts. Generally, consider stopping the tool when it leaves the cutting state.

④ Tool monitoring: The quality of the tool largely determines the processing quality of the custom cnc parts. In the automatic CNC machining and cutting process, it is necessary to judge the normal wear condition and abnormal damage condition of the tool through methods such as sound monitoring, cutting time control, pause inspection during CNC cutting, and workpiece surface analysis. According to the processing requirements, the tools should be processed in time to prevent the processing quality problems caused by the tools not being processed in time.

7. Question: How Do You Choose Processing Tools Reasonably? What are the Major Factors in Cutting the Amount? How Many Kinds of Materials are Available? How Do Determine the Speed, Cutting Speed, and Cutting Width of the Tool?

①When plane milling, you should choose non-reground carbide end mills or end mills. In general CNC milling, it is best to use the second pass to the CNC machining process. The first pass is best to use the end mill for rough milling, and continue to pass along the surface of the precision cnc machining parts. The width of each pass is recommended to be 60%-75% of the tool diameter.

② Endmills and end mills with carbide screw inserts are mainly used for processing bosses, grooves, and box mouth surfaces.

③ Ball knives and round knives (also known as round nose knives) are often used to process curved surfaces and variable-bevel contours. The ball knife is mostly used for semi-finishing and finishing. Round knives inlaid with cemented carbide tools are mostly used for roughing.

8. Question: What is the Function of the Processing Procedure Sheet? What Should be Included in the Processing Procedure Sheet?

(1) The CNC processing procedure sheet is one of the contents of the numerical control processing technology design, and it is also a procedure that needs to be followed and executed by the operator. It is a specific description of the CNC processing procedure. The purpose is to let the operator clarify the content of the procedure, clamping and positioning methods, and the cutting tools selected by each processing program should be paid attention to.

(2) In the CNC processing program list, it should include: the drawing and programming file name, workpiece name, clamping sketch, program name, a tool used in each program, maximum cutting depth, processing nature (such as roughing or finishing ), theoretical processing time, etc.

9. Question: What Preparations Should be Made before CNC Programming?

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

①The workpiece clamping method;

②The size of the workpiece blank in order to determine the processing range or whether multiple clamping is required;

③ The material of the workpiece- —In order to choose which tool to use for processing;

④What are the tools 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.

10. Question: What are the Principles for Setting the Safety Height in Programming?

Answer: The principle of setting the safety height: is generally higher than the highest surface of the island. Or set the programmed zero point on the highest surface, so as to avoid the danger of hitting the knife to the greatest extent.

11. Question: After the Tool Path is Compiled, Why is It Necessary to Post-Process?

Answer: Because the address code and NC program format that can be recognized by different machine tools are different, it is necessary to select the correct post-processing format for the machine tool used to ensure that the compiled program can run.

12. Question: What is DNC Communication?

①The method 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 (such as floppy disk, tape reader, communication line, etc.) for storage, and the program is called from the memory during CNC processing.  Because the memory capacity is limited by the size, when the program is large, the DNC method can be used for CNC processing. Since 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.

② There are three main elements of cutting parameters: depth of cut, spindle speed, and feed speed. The overall principle of the selection of cutting parameters is less cutting, fast feed (that is, the cutting depth is small, and the feed speed is fast).

③According to the classification of materials, tools are generally divided into ordinary hard white steel tools (materials are high-speed steel), coated tools (such as titanium-plated, etc.), and alloy tools (such as tungsten steel, boron nitride tools, etc.).

For many years, YIJIN Hardware has been known for providing custom cnc parts, precision cnc machined parts, precision cnc machining parts,cnc precision parts, and our production of precision cnc machining parts can stand out from the competitors. Much of this success stems from our ability to collaborate with customers to design parts.

The production of precision cnc machining parts requires a high level of industry experience, and YIJIN Hardware has unique expertise that enables our engineers to be as creative as possible in solving unique problems for our customers.

If you are interested in our custom cnc parts service, you are welcome to send your requirements with your drawings to us via email. We are very glad to give you the most favorable quotation.

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