Application of on-line measurement technology in front cover processing
On-line measurement is a measurement technology based on computer automatic control, and the measurement process is controlled by a numerical control program. On-line automatic measurement of workpieces on CNC machine tools is an effective method to improve the automatic machining level of CNC machine tools and ensure the accuracy of workpiece machining. Therefore, the online automatic measurement system for CNC machine tools is one of the important features to measure the technical level of CNC machine tools. It is an essential configuration that is essential for the purchase of high-precision CNC machines.
Process analysis of parts processing
The front end cover of the passenger electric vehicle's gearbox is a key component of the motor assembly, with strict assembly dimensions and high dimensional tolerance accuracy. The parts are typical die-casting parts, the material is ZL104, the part weight is 2.3KG, the annual demand is 80,000 pieces, and the maximum size of the parts is φ321×78.
According to the structure of the parts, the machining of the parts is processed in three processes: OP10 CNC, machining end face and φ72e6. OP20 CNC machining A reference end face and φ321e6, φ62S7, OP30 machining center, using the machining center fixture with A-axis rotation, positioning and clamping with A reference end face and φ288h8, the machine adopts online automatic measuring system to assist the operator before processing. φ62S7 is the positioning reference, the workpiece is corrected, and the workpiece coordinate system is automatically set to ensure the processing specification of the position of the two sides of 4-φ7.6H7 to the reference C of 0.05MM. Figure 1 is a schematic diagram of the process of part OP30
figure 1
OP10, OP20 machine tool uses Japanese TAKISAWA (泷泽) TC350E CNC lathe, OP30 machine tool selects LGMAZAK (Little Giant) 510C vertical CNC machining center, to ensure the processing accuracy requirements of parts, the temperature of the external space environment for the processing of parts The temperature of the cutting fluid is effectively controlled. The temperature of the external space environment is controlled by the central air conditioner. The temperature requirement is 20 ° ± 1 °. The machine tool is equipped with a special cutting fluid constant temperature circulation control system. The temperature requirement is 20 °~25°, which minimizes the influence of the heat generated during the continuous cutting process on the machining accuracy of the part.
The working principle of online measurement of CNC machine tools
The online inspection system of CNC machine tools consists of hardware and software. The hardware part is usually composed of the following machine body, CNC system, servo system and online measurement system.
3.1. Composition of online measuring system The online measuring system selected by LGMAZAK 510C vertical CNC machining center in OP30 process is the product of Italy MARPOSS. It adopts infrared transmission spindle measuring system and the triggering probe system is in The working installation in the machine tool is shown in Figure 2.
figure 2
The online measuring system consists of a triggering probe, a signal transmission system and a data acquisition system. It is a key part of the online measurement system of CNC machine tools and directly affects the accuracy of online measurement. The key component is the trigger type probe. The trigger type probe can be used for dimension measurement during the machining process. The machining program is automatically modified according to the measurement result to improve the machining accuracy, so that the CNC machine tool is both a processing device and a measuring machine. Features.
3.2. Working principle of CNC machine tool online measuring system The turning jig 4 is located at the position shown in Figure 3. The operator puts the parts into the turning jig 4 as required, and opens the manual two-way four-way hydraulic switch control valve (not shown) The hydraulic oil passes through the oil distributor 6 connected to the rotary clamp 4, pushes the hydraulic angle cylinder 8 on the rotary clamp 4, presses the component 2, and then starts the machine program operation, and the machine tool passes the A-axis 1 and the tailstock according to the program. 5 Drive the rotary clamp 4 to rotate 180°, and the machine tool adjusts the trigger type probe 7 from the tool magazine to the machine tool spindle by the machine tool manipulator (not shown) according to the program requirements, and executes the online measurement macro program to measure the part φ62S7 reference. The coordinate position of C is set to the initial origin of the part machining program by the online measurement macro program, and the machine automatically completes the setting of the part coordinate system according to the macro program. The machine tool continues to follow the requirements of the part machining program, and calls the tool 3 to process the parts according to the drawings until a machining cycle is completed. In order to ensure the positioning accuracy of A-axis 1 and tailstock 5 during machining and measurement, both A-axis 1 and tailstock 5 use hydraulic brake locking to ensure the overall rigidity of the clamp during high-speed machining and movement. Figure 3 is a schematic view of the rotating part of the machining center of the part OP30.
image 3
Conclusion
The online automatic measuring system can assist the operator to correct the workpiece before machining, automatically set the workpiece coordinate system, shorten the auxiliary time and improve the processing efficiency; and automatically measure the workpiece size during processing and after processing. According to the measurement result, the error compensation data can be automatically generated and fed back to the numerical control system to ensure the dimensional accuracy of the workpiece and the dimensional consistency of the batch workpiece. In-machine online measurement can also avoid the secondary error caused by moving the workpiece to the measuring machine, which can improve the machining accuracy and precision retention. The qualified product can be obtained by one cutting, which greatly enhances the intelligent degree of the CNC machine tool. .
According to the machining process requirements of the parts, the machine is equipped with an online measuring system. After about 6 months of use, about 30,000 pieces of products have been processed, and the initial design requirements have been met with full effect. The main key dimension characteristics have reached the technical requirements of CPK ≥ 1.67, and the initial quality design has been satisfactorily achieved. Requirements, the current products have been successfully put into volume production.
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