1、 Selection of positioning datum for computer gong machining center
(1) Try to choose the design datum on the part as the positioning datum.
(2) One time clamping can complete the machining of all key precision parts.
(3) When the machining center not only processes the datum but also completes the processing of each station, the selection of its positioning datum needs to consider the completion of as many processing contents as possible.
(4) When the positioning datum and design datum of a part are difficult to coincide, the assembly drawing should be carefully analyzed to determine the design function of the design datum of the part. Through the calculation of the dimension chain, the tolerance range between the positioning datum and design datum should be strictly specified to ensure the machining accuracy.
2、 Selection and use of fixture for CNC machining center
(1) According to the characteristics and processing needs of machining center, the commonly used fixture types include special fixture, modular fixture, adjustable fixture, group fixture and workpiece unified reference positioning clamping system.
(2) The high flexibility of machining center requires that its fixture structure is more compact and simple than ordinary machine tool, clamping action is more rapid and accurate, auxiliary time is reduced as far as possible, operation is more convenient, labor-saving and safe, and enough rigidity and flexibility should be ensured. Therefore, pneumatic and hydraulic clamping devices are often used.
(3) In order to keep all the surfaces to be machined fully exposed, the fixture should be open as far as possible, and the space position of the clamping element should be low as possible, so there must be space for the tool path.
(4) Considering the minimum distance between the machine tool spindle and the worktable and the clamping length of the tool, the installation position of the fixture on the machine tool worktable should ensure that the processing content of the workpiece can be completed within the stroke range of the spindle.
(5) Automatic tool change and worktable exchange can not interfere with the fixture or workpiece.
(6) Sometimes, the positioning block on the fixture is used when installing the workpiece. In the process, in order to meet the processing of the front, back, left and right stations and prevent interference, the workpiece can be removed after clamping. In this regard, we should consider the problem of maintaining the positioning accuracy of the workpiece after removing the positioning element.
(7) Try not to change the clamping point in the middle of machining.
3、 CNC machining to determine the best position of parts on the machine tool table
报错 笔记
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