It is estimated that everyone will have a machining center in their workshop. The accuracy of a machining center is very important, because the accuracy of the machining center affects the processing quality. Therefore, regarding the accuracy of the machining center, those engaged in mechanical processing have also been studying how to reduce errors as much as possible. Methods. So how to judge the accuracy of a machining center? Let's talk about 4 aspects below.
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1. Positioning of test piece in vertical machining center:
The test piece should be located midway through the When there are special requirements for the positioning position of the test piece, these should be specified in the agreement between the manufacturer and the user.
2. Fixation of specimen:
The test piece should be easily mounted on a special fixture to achieve maximum stability of the tool and fixture. The mounting surfaces of the fixture and test piece should be straight.
The parallelism between the mounting surface of the test piece and the clamping surface of the fixture should be checked. Suitable clamping methods should be used to enable the tool to penetrate and machine the entire length of the center hole. It is recommended to use countersunk screws to fix the specimen to avoid interference between the tool and the screws. Other equivalent methods can also be used. The total height of the specimen depends on the method of fixation chosen.
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3. Test piece material, tool and cutting parameters:
The material of the test piece, cutting tools and cutting parameters are selected according to the agreement between the manufacturer and the user, and should be recorded. The recommended cutting parameters are as follows:
1) Cutting speed: Cast iron parts are about 50m/min; aluminum parts are about 300m/min.
2) Feed amount: approximately (0.05~0.10)mm/tooth.
3) Cutting depth: The radial depth of cut for all milling processes should be 0.2mm.
4. Dimensions of test piece:
If the test piece is cut several times, the outer dimensions are reduced, and the hole diameter is increased. When used for acceptance inspection, it is recommended that the final profile processing test piece size be consistent with that specified in this standard, so as to faithfully reflect the cutting accuracy of the machining center. The test piece can be used repeatedly in cutting tests, and its specifications should be kept within ±10% of the characteristic dimensions given in this standard. When the specimen is reused, a thin layer cut should be made to clean all surfaces before a new fine-cut test is carried out.
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It is estimated that everyone will encounter another problem in the process of using the machining center. Why does the accuracy of the machining center deteriorate as it is used? Did we buy parallel imports?
The poor machining accuracy of parts of the machining center is generally due to the fact that the feed dynamics between the axes are not adjusted according to the error during installation and adjustment, or due to wear and tear, the transmission chain of each axis of the machine tool has changed (such as screw clearance, pitch Error changes, axial movement, etc.). It can be solved by readjusting and modifying the gap compensation amount.
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When the dynamic tracking error is too large and an alarm occurs, you can check: whether the servo motor speed is too high; whether the position detection component is in good condition; whether the position feedback cable connector is in good contact; whether the corresponding analog output latch and gain potentiometer are in good condition; Whether the corresponding servo drive device is normal.
If the machining accuracy is poor due to overshoot during machine tool movement, it may be that the acceleration and deceleration time is too short, and the speed change time can be appropriately extended; it may also be that the connection between the servo motor and the screw is loose or the rigidity is too poor, and the position can be appropriately reduced. The gain of the ring may be due to the out-of-tolerance roundness when the two axes are linked. This deformation may be caused by the machine not being adjusted properly. Poor positioning accuracy of the shaft or improper lead screw clearance compensation will lead to roundness errors when crossing quadrants.
It turns out that there is so much knowledge about the accuracy of machine tools.
But there is another saying among the people: high accuracy is guaranteed by people. It is said that the machine tools with the highest machining accuracy in the world are calibrated by people. In Japan, there are dedicated craftsmen who calibrate the machining accuracy of machine tools. Such people are priceless treasures in every machine tool manufacturer. According to this statement, it is possible for us to use parts with relatively low precision to assemble machine tools with amazing processing accuracy.
