Introduction There are two types of CNC lathes in our company. One is CJK1630 produced by Baoji Machine Tool Plant, the FANUC system is used, and the other is CYNCP320 produced by Yunnan Machine Tool Plant. It is aerospace numerical control system. In use, we found that the two systems are not the same, which made us pay special attention to the CNC lathe coordinate system and then analyzed it.
1 Introduction to CNC coordinate system
The machining of CNC machine tools is done by program control, so the determination and use of the coordinate system is very important. According to the ISO 841 standard, the CNC machine coordinate system is determined using the right-hand Cartesian coordinate system as a standard. The CNC lathe is parallel to the main axis direction, that is, the longitudinal direction is the Z axis, perpendicular to the main axis direction, that is, the lateral direction is the X axis, and the tool is forward away from the workpiece.
The CNC lathe has three coordinate systems, namely the machine coordinate system, the programmed coordinate system and the workpiece coordinate system. The origin of the machine coordinate system is the origin of the fixed coordinate system of the manufacturer when manufacturing the machine tool, also known as the mechanical zero point. It has been determined during machine tool assembly and commissioning and is the benchmark for machine tool processing. In use, the mechanical coordinate system is determined by the reference point. After the machine system is started, the reference point operation is performed and the mechanical coordinate system is established. Once the coordinate system is established, the coordinate system will not change as long as the power is not turned off. The programmed coordinate system is the coordinate system used in programming. Generally, we have the Z axis coincident with the workpiece axis, and the X axis is placed on the workpiece end face. The workpiece coordinate system is the coordinate system used by the machine tool for machining. It should be consistent with the programmed coordinate system. Whether the programming coordinate system is consistent with the work coordinate system makes the operation key.
In use, we found that the mechanical coordinate system of the FANUC system and the aerospace numerical control system are basically the same, and are determined by reference point after the system is started.
2 Discussion on the determination of two system coordinate systems The FANUC system has three methods for determining the workpiece coordinate system.
The first is to obtain the workpiece coordinate system by writing the tool offset value to the tool. This method is simple in operation and good in reliability. He is closely related to the mechanical coordinate system through the tool offset. As long as the power is constantly changed and the tool offset value is not changed, the workpiece coordinate system will exist and will not change, even if the power is turned off, restart. After the reference point is returned, the workpiece coordinate system is still in the original position.
The second is to set the coordinate system with G50. After the tool is moved, move the knife to the position set by G50 to process. For the reference knives first, the knives of the other knives are relative to the reference knives.
The third method is the MDI parameter. With G54~G59, six coordinate systems can be set. This coordinate system is constant with respect to the reference point and has nothing to do with the tool. This method is suitable for mass production and the machining of workpieces with a fixed clamping position on the chuck.
The workpiece coordinate system of the aerospace numerical control system is determined by setting the coordinate value of the current position of the tool by G92 Xa zb (similar to FANUC's G50) statement. Before machining, the tool needs to be calibrated first. The reference tool is used to achieve the correctness. After the tool is set, the coordinate will be cleared. When the other tool is displayed, the coordinate value will be written into the corresponding tool compensation parameter. Then measure the tool diameter Фd, move the tool to the position where the coordinate display X=ad Z=b, and run the program (the programmed coordinate system origin of this method is at the center of the right end face of the workpiece). Pressing reset or emergency stop during machining can return to the set G92 starting point to continue machining. However, if there is an accident such as: X or Z axis has no servo, tracking error, power failure, etc., the system can only be restarted, and the workpiece coordinate system set later will disappear, and the tool needs to be re-paired. If it is mass production, after processing one piece, return to G92 starting point to continue processing the next piece. If there is a slight mistake in the operation process, it is possible to modify the workpiece coordinate system and need to re-tool. In view of this situation, we have tried to fix the workpiece coordinate system on the machine. We found that the machine tool has 16 tool compensation values ​​that can be used, so we tested several methods.
The first method: When the reference tool is used, the displayed reference point deviation value is written to the No. 9 tool compensation, and the inverse of the tool diameter is written to the X value of the No. 8 tool compensation. After the system restarts, move the tool to the reference point and run the program to return the tool to the starting point of workpiece G92. The program is as follows:
N001 G92 X0 Z0;
N002 G00 T19;
N003 G92 X0 Z0;
N004 G00 X100 Z100;
N005 G00 T18;
N006 G92 X100 Z100;
N007 M30;
It is normal for the program to run until the fourth sentence. When the fifth sentence is run, the tool should move to the negative direction of X, but the positive direction moves to X and Z, and the result fails. The reason for the analysis is suspected to be the two knives for the same program to adjust one position.
The second method: when the reference tool is used, the Z value of the deviation from the reference point is written into the Z value of the No. 9 tool offset, and the sum of the displayed X value and the inverse of the tool diameter is written into the 9 good knife. The complemented X value. After the system restarts, move the tool to the reference point and run the following program:
N001 G92 X0 Z0;
N002 G00 T19;
N003 G00 X100 Z100;
N004 M30;
After the program runs, the tool is successfully moved to the starting point of workpiece G92. However, when running the part program, the tool should move to the negative direction of X and Z, but it will move to the positive direction of X and Z abnormally, and the result will fail. Analysis of the reason is suspected that after the system runs a program, the running tool is still in the memory, there is no emptying, it must first make the movement to eliminate the tool compensation when running the next program.
The third method: after the tool of the second method is used to move the tool to the starting point of the workpiece G92, the system is restarted, and the machining is not directly processed by the reference point, and can be processed after the test. But this does not meet the machine operating procedures, and the conclusion is that it is feasible but not feasible.
The fourth method: when the tool is set, the offset value of the displayed reference point is added to 100 and then written to the corresponding tool offset. Each knife is so, so that the tool compensation of each knife is relative to For the reference point, the G92 starting point of the machining program is set to X100 Z100, which is feasible after the test. The disadvantage of this method is that the starting point of each machining is the reference point, and the tool moves a long distance, but since this is G00 fast moving, it is acceptable.
The fifth method: the deviation from the reference point and the diameter of the tool are recorded when the reference tool is pressed. Once the system is restarted, the tool can be manually moved to the G92 starting position. This method is a bit more troublesome, but it works.
3 Conclusion The determination of the workpiece coordinate system of CNC machine tools is a major factor affecting the machining accuracy. It has different requirements for different types of machine tools. Only by accurately mastering and flexibly applying this knowledge can the CNC machine tools be operated.
1 Introduction to CNC coordinate system
The machining of CNC machine tools is done by program control, so the determination and use of the coordinate system is very important. According to the ISO 841 standard, the CNC machine coordinate system is determined using the right-hand Cartesian coordinate system as a standard. The CNC lathe is parallel to the main axis direction, that is, the longitudinal direction is the Z axis, perpendicular to the main axis direction, that is, the lateral direction is the X axis, and the tool is forward away from the workpiece.
The CNC lathe has three coordinate systems, namely the machine coordinate system, the programmed coordinate system and the workpiece coordinate system. The origin of the machine coordinate system is the origin of the fixed coordinate system of the manufacturer when manufacturing the machine tool, also known as the mechanical zero point. It has been determined during machine tool assembly and commissioning and is the benchmark for machine tool processing. In use, the mechanical coordinate system is determined by the reference point. After the machine system is started, the reference point operation is performed and the mechanical coordinate system is established. Once the coordinate system is established, the coordinate system will not change as long as the power is not turned off. The programmed coordinate system is the coordinate system used in programming. Generally, we have the Z axis coincident with the workpiece axis, and the X axis is placed on the workpiece end face. The workpiece coordinate system is the coordinate system used by the machine tool for machining. It should be consistent with the programmed coordinate system. Whether the programming coordinate system is consistent with the work coordinate system makes the operation key.
In use, we found that the mechanical coordinate system of the FANUC system and the aerospace numerical control system are basically the same, and are determined by reference point after the system is started.
2 Discussion on the determination of two system coordinate systems The FANUC system has three methods for determining the workpiece coordinate system.
The first is to obtain the workpiece coordinate system by writing the tool offset value to the tool. This method is simple in operation and good in reliability. He is closely related to the mechanical coordinate system through the tool offset. As long as the power is constantly changed and the tool offset value is not changed, the workpiece coordinate system will exist and will not change, even if the power is turned off, restart. After the reference point is returned, the workpiece coordinate system is still in the original position.
The second is to set the coordinate system with G50. After the tool is moved, move the knife to the position set by G50 to process. For the reference knives first, the knives of the other knives are relative to the reference knives.
The third method is the MDI parameter. With G54~G59, six coordinate systems can be set. This coordinate system is constant with respect to the reference point and has nothing to do with the tool. This method is suitable for mass production and the machining of workpieces with a fixed clamping position on the chuck.
The workpiece coordinate system of the aerospace numerical control system is determined by setting the coordinate value of the current position of the tool by G92 Xa zb (similar to FANUC's G50) statement. Before machining, the tool needs to be calibrated first. The reference tool is used to achieve the correctness. After the tool is set, the coordinate will be cleared. When the other tool is displayed, the coordinate value will be written into the corresponding tool compensation parameter. Then measure the tool diameter Фd, move the tool to the position where the coordinate display X=ad Z=b, and run the program (the programmed coordinate system origin of this method is at the center of the right end face of the workpiece). Pressing reset or emergency stop during machining can return to the set G92 starting point to continue machining. However, if there is an accident such as: X or Z axis has no servo, tracking error, power failure, etc., the system can only be restarted, and the workpiece coordinate system set later will disappear, and the tool needs to be re-paired. If it is mass production, after processing one piece, return to G92 starting point to continue processing the next piece. If there is a slight mistake in the operation process, it is possible to modify the workpiece coordinate system and need to re-tool. In view of this situation, we have tried to fix the workpiece coordinate system on the machine. We found that the machine tool has 16 tool compensation values ​​that can be used, so we tested several methods.
The first method: When the reference tool is used, the displayed reference point deviation value is written to the No. 9 tool compensation, and the inverse of the tool diameter is written to the X value of the No. 8 tool compensation. After the system restarts, move the tool to the reference point and run the program to return the tool to the starting point of workpiece G92. The program is as follows:
N001 G92 X0 Z0;
N002 G00 T19;
N003 G92 X0 Z0;
N004 G00 X100 Z100;
N005 G00 T18;
N006 G92 X100 Z100;
N007 M30;
It is normal for the program to run until the fourth sentence. When the fifth sentence is run, the tool should move to the negative direction of X, but the positive direction moves to X and Z, and the result fails. The reason for the analysis is suspected to be the two knives for the same program to adjust one position.
The second method: when the reference tool is used, the Z value of the deviation from the reference point is written into the Z value of the No. 9 tool offset, and the sum of the displayed X value and the inverse of the tool diameter is written into the 9 good knife. The complemented X value. After the system restarts, move the tool to the reference point and run the following program:
N001 G92 X0 Z0;
N002 G00 T19;
N003 G00 X100 Z100;
N004 M30;
After the program runs, the tool is successfully moved to the starting point of workpiece G92. However, when running the part program, the tool should move to the negative direction of X and Z, but it will move to the positive direction of X and Z abnormally, and the result will fail. Analysis of the reason is suspected that after the system runs a program, the running tool is still in the memory, there is no emptying, it must first make the movement to eliminate the tool compensation when running the next program.
The third method: after the tool of the second method is used to move the tool to the starting point of the workpiece G92, the system is restarted, and the machining is not directly processed by the reference point, and can be processed after the test. But this does not meet the machine operating procedures, and the conclusion is that it is feasible but not feasible.
The fourth method: when the tool is set, the offset value of the displayed reference point is added to 100 and then written to the corresponding tool offset. Each knife is so, so that the tool compensation of each knife is relative to For the reference point, the G92 starting point of the machining program is set to X100 Z100, which is feasible after the test. The disadvantage of this method is that the starting point of each machining is the reference point, and the tool moves a long distance, but since this is G00 fast moving, it is acceptable.
The fifth method: the deviation from the reference point and the diameter of the tool are recorded when the reference tool is pressed. Once the system is restarted, the tool can be manually moved to the G92 starting position. This method is a bit more troublesome, but it works.
3 Conclusion The determination of the workpiece coordinate system of CNC machine tools is a major factor affecting the machining accuracy. It has different requirements for different types of machine tools. Only by accurately mastering and flexibly applying this knowledge can the CNC machine tools be operated.
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