NC programming method to improve machining accuracy of CNC cutting machine
In the preparation of machining programs, proper use of methods and techniques is of great significance to ensure and improve the machining accuracy of CNC flame cutting machine tools. Shandong Jiabang CNC has accumulated some programming experience in the long-term practice, the introduction is as follows.
- Eliminate the influence of the position of the tolerance zone
Many dimensions of the part are marked with tolerances, and the position of the tolerance zone cannot be the same. However, the CNC program is generally compiled according to the outline of the part, that is, according to the basic size of the part, ignoring the influence of the position of the tolerance zone. In this way, even if the precision of the CNC machine tool is high, the machined part may not meet its dimensional tolerance requirements.
- Program according to the basic size, consider the position of the tolerance zone with radius compensation
That is, it is still calculated and programmed according to the basic size of the part, and the same turning tool is used to process the outer circles everywhere, and different tool radius compensation values are used when processing the dimensions of different tolerance zone positions. In this method, the radius of the tool nose arc must be known first (the machining trajectory of this part is parallel to the X and Z axes, so it is not necessary to know the radius of the tool nose arc), so it is inconvenient to use and can only be applied to some CNC systems.
- Change the basic dimensions and the position of the tolerance zone
That is, on the premise of ensuring that the limit size of the part remains unchanged, the basic size and the position of the tolerance zone are adjusted. Generally, it is adjusted according to the symmetrical tolerance zone, and the adjusted basic dimensions and tolerances. When programming, it is performed according to the adjusted basic size, so that the same turning tool and the same tool compensation value are used in the finishing process (in this example, the machining track is parallel to the X and Z axes, and the tool compensation is not required), the machining accuracy can be guaranteed. Of course, if the part is ultimately to be finished (such as fine grinding), in order to ensure sufficient grinding allowance, the basic size can also be slightly increased (in this case, the tolerance zone is asymmetric).
- Eliminate the influence of machine tool clearance
When the CNC machine tool is used for a long time or due to its own transmission system structure, there may be a reverse dead zone error. At this time, some measures can be taken during CNC programming and processing to eliminate the reverse dead zone error and improve the processing accuracy. Especially when the dimensional accuracy of the parts being processed is close to the repeatable positioning accuracy of the CNC machine tool, it is more important.
- Reduce the influence of the cumulative error of the numerical control system
During the operation of rapid movement and interpolation, the numerical control system will generate accumulated errors. When it reaches a certain value, it will cause the machine tool to generate movement and positioning errors, which will affect the machining accuracy. The following measures can reduce the cumulative error of the CNC system.
try to program in absolute terms
Absolute programming is based on a fixed point (the origin of workpiece coordinates), and each program and the entire machining process are based on this. Incremental programming is based on the previous point, and continuous execution of multi-segment programs will inevitably produce cumulative errors.
Insert reference point return command
When the machine tool returns to the reference point, the coordinates will be cleared to zero, thus eliminating the accumulated error of the numerical control system operation. Properly inserting the reference point return command in a long program is beneficial to ensure the machining accuracy. When there is a tool change request, you can return to the reference point to change the tool, which kills two birds with one stone.
Several forms and methods of NC programming:
- Manual programming: The specific shape and size are obtained from the part drawing, and the part graphic analysis, process processing, and numerical calculation are manually completed, and then the program list is input into the cutting machine system in the form of buttons, and the system will execute according to the input program. Finally get the desired graphics.
- Automatic programming: use a computer or a programming machine to complete the process of compiling part programs, which is very convenient for complex parts.
C.CAD: Using CAD software to cooperate with the cutting machine application software developed by our company, you only need to input the required size and graphics into CAD, generate the cutting machine graphics, do the compilation process, and then generate the cutting machine code, which is directly converted to CNC cutting It is used for cutting on the machine. Although this programming has a single function, it is easy to learn and has a low price. It is still the choice of small and medium-sized enterprises.
Points to be paid attention to in the operation of CNC plasma cutting machine for beginners
First of all, the operator needs to be proficient in the use of CNC plasma cutting machine specifications. Again, watch out for servo motors. The servo motor used by the CCNC cutting machine is different from the ordinary motor. It is equipped with a pulse encoder and a position detector. It is a wearing part. In particular, the pulse encoder is made of glass and is bonded with epoxy resin, which is relatively fragile. In some CNC plasma cutting machines, the cable connecting the servo motor is exposed to the outside and moves with the carriage, or drags on other components. Over time, the cable is damaged and causes failure.
If the CNC plasma cutting machine has the function of anti-collision test, then use this function to check the accuracy of programming. Therefore, for the servo motor, it is forbidden to use a hammer when assembling: it is forbidden to collide or place heavy objects such as parts and blanks on it.
In addition, every beginner is more or less scared in the early stage of operating the machine tool, afraid that the machine tool will collide with the gun or the machine. Only after the operator has mastered the operation of the CNC machine tool, can he overcome the similar fear and panic, and on this basis, can he learn to grasp the higher operating skills of the CNC plasma cutting machine. Therefore, the CNC machine tools must be inspected and maintained regularly, especially the cables, if they are found to be damaged, broken or virtual connections, they should be replaced to prevent the occurrence of failures.