Application and development of mechanical probes Mechanical probes are generally 6mm steel balls. They are spring-loaded on the measuring rod. When the workpiece is hit, it can be retracted and the circuit is turned on to emit light signals. The coordinate position of the measured surface can be obtained by the indication of the photoelectric probe and the machine coordinate position. It is necessary to record the coordinate value of each measurement, and then manually calculate it. Finally, the calculated value is manually input into G54 to G57. Especially when the workpiece origin is at the center, the calculation is complicated, the efficiency is low, and it is easy to input errors during the input process. Frequently, part processing is scrapped because of incorrect coordinate values. In order to avoid such errors, the tooling process is optimized, and some subroutines are developed. The numerical calculation and coordinate value input are changed to the CNC system for automatic execution. In this process, the R parameter is used to calculate the coordinate value, and the @ command is used to automatically input the coordinate value into G54 to G57. When measuring the origin of the workpiece, you only need to input the corresponding offset value, and then call the corresponding subroutine to complete the input of the workpiece origin. The workpiece origin measurement is simple and fast, and the most important is to improve the efficiency and accuracy of the workpiece origin measurement, and it is not easy to cause human error. The MSGP6101 floor boring and milling machine is taken as an example to illustrate its development process.
The MSGP6101 floor boring and milling machine system is SIEMENS840C, and the spindle can be converted vertically. During the tool setting process, the X, Y, and Z offset values ​​vary with the vertical and horizontal modes. Therefore, the variable R50 is introduced into the subroutine to determine the offset. Value, only need to assign the corresponding offset value to R50 during measurement, the system will automatically calculate the actual position value of the workpiece coordinate system. In order to measure the subroutine corresponding to each coordinate axis (in order to avoid conflict with other subprograms in the program execution, the subroutine is represented by three digits, wherein the second digit represents the axis to be measured, 1, 4 is The X axis, 2, 5 is the Y axis, 3, 6 is the Z axis; the third digit is that the measured value will be automatically transferred to the set of registers in G54 ~ G57).
The improved X-axis tool-to-tool flow probe is used in parts and components. Some space-type parts in aerospace have complex spatial structure. There are groups of holes on the surface. The blanks are generally precision castings with small machining allowance. Some dimensional position errors in casting are relatively large. Before processing, it is necessary to ensure that the machining allowance of each hole system is uniform by borrowing the deviation, otherwise the holes will not be completely removed. The machining accuracy of the 4-32+0.0250mm rudder shaft hole on the part is required to be high. The diameter of the rudder shaft hole before machining is Φ30. If the alignment is improper, the four rudder shaft holes cannot be fully smashed, and the rudder shaft hole is It is the part with the highest processing precision on the part, so it is the key to processing the four rudder shaft holes that are 90° each other.
The original method of aligning is to install the dial indicator on the machine spindle and sequentially align the four rudder shaft holes to offset the parts. The specific process is as follows: first adjust the dial gauge mounted on the machine spindle to make it measure the Φ32 standard hole. The time is displayed as zero; then use the dial hole of the four rudder shaft holes to adjust the C axis so that the reading of the meter is within (+0.8, -0.8) mm, which ensures that the boring allowance is greater than 0.2mm. To read a hole table larger than the above range, you need to adjust the C axis, then the other three holes must be found again. Until the four holes of the disk are read within (+0.8, -0.8) mm, the angular position of the hole is determined. At the end of the deviation, the coordinate of the C axis is the origin of the C axis of the workpiece coordinate system. Due to the large dimensional error and angular position error of casting blank hole casting, each workpiece often needs to use the dial repeatedly, which is time-consuming.
Conclusion The probe is an important accessory for CNC machine tools. The use of a good probe is very beneficial to actual production. It not only reduces the labor intensity of workers, but also effectively ensures the accuracy of parts and improves production efficiency. How to use and develop the function of the probe to maximize its function of high efficiency, accuracy and convenience in real production is also an important aspect of the efficiency of CNC machine tools.
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