CNC machining, also known as CNC machining, refers to the machining performed with CNC machining tools. Because CNC machining is controlled by computer after programming, CNC machining has the advantages of stable machining quality, high machining accuracy, high repeatability, complex profiles, and high machining efficiency. In the actual processing process, human factors and operating experience will greatly affect the final processing quality. Below, twelve valuable experiences summed up by Elimold’s professional CNC manufacturers….
1. How to divide the CNC machining process?
The division of CNC machining processes can generally be carried out in the following ways:
1. The tool centralized sorting method is to divide the process according to the tools used, and use the same tool cnc to process all the parts that can be completed. Doing the rest of the way they can with the second knife, the third. This can reduce the number of tool changes, compress the idle time, and reduce unnecessary positioning errors.
2. 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, the plane and positioning surface are processed first, and then the hole is processed; the simple geometric shape is processed first, and then the complex geometric shape is processed; the parts with lower precision are processed first, and then the parts with higher precision are processed.
3. For the parts that are prone to CNC machining deformation by the rough and fine CNC machining sequence method, due to the possible deformation after rough machining, the shape needs to be corrected. separate. To sum up, when dividing the process, it must be flexibly grasped according to the structure and craftsmanship of the parts, the function of the machine tool, the number of CNC machining contents of the parts, 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 be reasonable.
2. What principles should be followed in the arrangement of CNC 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 need for positioning and clamping. The key point is that the rigidity of the workpiece is not damaged.
The sequence should generally follow the following principles:
1. The cnc processing of the previous process cannot affect the positioning and clamping of the next process, and the general machine tool processing process interspersed in the middle should also be considered comprehensively.
2. First carry out the inner shape and inner cavity processing process, and then carry out the outer shape processing process.
3. The process of CNC machining with the same positioning and clamping method or the same tool is best carried out in conjunction to reduce the number of repeated positioning, the number of tool changes and the number of times of moving the platen.
4. For multiple processes carried out in the same installation, the process with less damage to the rigidity of the workpiece should be arranged first.
3. What aspects should be paid attention to when determining the workpiece clamping method?
The following three points should be paid attention to when determining the positioning datum and clamping scheme:
1. Strive to unify the benchmarks of design, technology, and programming calculations.
2. Minimize the number of clampings, and try to make all the surfaces to be processed by CNC after one positioning.
3. Avoid using the manual adjustment scheme of occupying the machine.
4. The fixture should be open, and its positioning and clamping mechanism cannot affect the cutting tool in CNC machining (such as collision). When such a situation occurs, it can be clamped by using a vise or adding a bottom plate to extract screws.
4. How to determine the reasonable tool setting point? What is the relationship between the workpiece coordinate system and the programming coordinate system?
1. The tool setting point can be set on the part to be processed, but note that the tool setting point must be the reference position or the part that has been finished. Sometimes the tool setting point is destroyed by cnc processing after the first process, which will lead to the second There is no way to find the tool setting point in the first process and the subsequent tool setting. Therefore, when setting the tool in the first process, pay attention to establishing a relative tool setting position at a place that has a relatively fixed dimensional relationship with the positioning datum, so that the relative position relationship between them can be determined. Retrieve the original setting point. This relative tool setting position is usually set on the machine table or fixture. The selection principles are as follows:
1) It is easy to find.
2) Easy to program.
3) The tool setting error is small.
4) It is convenient and checkable during processing.
2. The origin position of the workpiece coordinate system is set by the operator himself. It is determined by tool setting after the workpiece is clamped. It reflects the distance and position relationship between the workpiece and the zero point of the machine tool. Once the workpiece coordinate system is fixed, it generally does not change. The workpiece coordinate system and the programming coordinate system must be unified, that is, during processing, the workpiece coordinate system and the programming coordinate system are consistent.
5. How to choose the knife route?
The tool path is the movement track and direction of the tool relative to the workpiece during the exponential control process. Reasonable selection of machining route is very important, because it is closely related to CNC machining accuracy and surface quality of parts. When determining the tool path, the following points are mainly considered:
1. Ensure the machining accuracy of the parts.
2. It is convenient for numerical calculation and reduces the programming workload.
3. Seek the shortest CNC machining route and reduce the time of empty tool to improve CNC machining efficiency.
4. Minimize the number of program segments.
5. To ensure the roughness of the workpiece contour surface after CNC machining, the final contour should be processed continuously in the last pass.
6. The advance and retraction of the tool (cut in and out) should also be carefully considered, so as to minimize the knife stop at the contour (elastic deformation caused by sudden changes in cutting force) and leave knife marks, and also avoid going down vertically on the contour surface. knife and scratch the workpiece.
6. How to monitor and adjust during cnc processing?
After the workpiece is aligned and the program debugging is completed, it can enter the automatic processing stage. In the automatic machining process, the operator must monitor the cutting process to prevent workpiece quality problems and other accidents caused by abnormal cutting.
Monitoring the cutting process mainly considers the following aspects:
1. Monitoring of the machining process The main consideration for rough machining is the rapid removal of the excess allowance on the surface of the workpiece. In the automatic machining process of the machine tool, according to the set cutting amount, the tool automatically cuts according to the predetermined cutting path. At this time, the operator should pay attention to observe the change of the cutting load during the automatic machining process through the cutting load table, and adjust the cutting amount according to the bearing capacity of the tool to maximize the efficiency of the machine tool.
2. Monitoring of cutting sound during cutting In the process of automatic cutting, generally when cutting starts, the sound of the tool cutting the workpiece is stable, continuous and brisk, and the movement of the machine tool is stable at this time. With the progress of the cutting process, when there are hard spots on the workpiece, tool wear or tool feeding, etc., the cutting process becomes unstable. The unstable performance is that the cutting sound changes, and the tool and the workpiece will collide with each other. The machine will vibrate. At this time, the cutting amount and cutting conditions should be adjusted in time. When the adjustment effect is not obvious, the machine tool should be suspended and the condition of the tool and workpiece should be checked.
3. Finishing process monitoring and finishing, mainly 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 built-up edge on the machined surface. For cavity machining, attention should also be paid to overcutting and yielding at the corners.
To solve the above problems, firstly, pay attention to adjusting the spray position of cutting fluid, so that the machined surface is always in cooling condition;
The second is to pay attention to observe the quality of the machined surface of the workpiece, and avoid quality changes as much as possible by adjusting the cutting amount. If the adjustment still has no obvious effect, it should stop to check whether the original program is reasonable.
It is especially important to pay attention to the position of the tool when suspending the inspection or stopping the inspection. If the tool stops during the cutting process, the sudden spindle stop will cause tool marks on the surface of the workpiece. Generally, the shutdown should be considered when the tool leaves the cutting state.
4. Tool monitoring The quality of the 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 the tool by means of sound monitoring, cutting time control, suspension inspection during the cutting process, 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. How to choose a machining tool reasonably? How many elements are there in the cutting amount? How many types of knives are there? How to determine the rotational speed of the tool, cutting speed, cutting width?
1. When milling the plane, choose a non-regrinding carbide end mill or end mill. Generally, when milling, try to use two passes for processing. It is best to use end mills for rough milling for the first pass, and continue to pass along the surface of the workpiece. The recommended width of each pass is 60%–75% of the tool diameter.
2. End mills and end mills with carbide inserts are mainly used to process bosses, grooves and box 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 cutter is mostly used for semi-finishing and finishing. Round knives with carbide inserts are mostly used for roughing.
8. What is the function of the processing program list? What should be included in the processing program list?
1. The machining program list is one of the contents of the CNC machining process design. It is also a procedure that the operator needs to abide by and execute. It is a specific description of the machining program. The tool selected by the program should pay attention to the problems and so on.
2. In the processing program list, it should 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 roughing or finishing) , theoretical processing time, etc.
9. How to prepare before CNC programming?
After determining the machining process, before programming, you should understand:
1. Workpiece clamping method;
2. The size of the workpiece blank – in order to determine the scope of processing or whether multiple clamping is required;
3. The material of the workpiece – in order to choose which tool to use for processing;
4. What are the tools in stock? Avoid modifying the program because there is no such tool during processing. If you must use this tool, you can prepare it in advance.
10. What are the principles for setting the safety height in programming?
The principle of setting the safe height: generally higher than the highest surface of the island. Or set the programmed zero point on the highest surface, which can also avoid the danger of collision to the greatest extent.
11. After the tool path is programmed, why do it need to be post-processed?
Because the address codes and NC program formats 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 programmed program can run.
12. What is DNC communication?
The way of program transmission can be divided into CNC and DNC. CNC means that the program is transmitted to the memory of the machine tool through the media medium (such as floppy disk, tape reader, communication line, etc.) and stored, and the program is called from the memory during processing. processing. Since the capacity of the memory is limited by the size, the DNC method can be used for processing when the program is large. Since the machine tool directly reads the program from the control computer during DNC processing (that is, it is done while feeding), it is not affected by the capacity of the memory. Limited by size.
1. There are three major elements of cutting amount: cutting depth, spindle speed and feed rate. The general principle for the selection of cutting amount is: less cutting, fast feed (that is, small cutting depth and fast feed speed)
2. According to the material classification, the tools are generally divided into ordinary hard white steel knives (the material is high-speed steel), coated knives (such as titanium plating, etc.), and alloy knives (such as tungsten steel, boron nitride knives, etc.).
If you want to change from a CNC machining operator to a programmer, the above must be known. Besides the above, what else do you think you need to know? Is it also important to improve efficiency? It is also important to avoid collisions and empty knives.
If you need cnc processing service, contact elimold to serve you. Our global team is always ready to serve you.