- Three basic requirements for selecting datum: (1) the selected datum should be able to ensure accurate positioning of workpiece, convenient and reliable loading and unloading. (2) The size calculation of the selected datum and each processing part is simple. (3) Ensure the machining accuracy.
(2) the positioning accuracy of the workpiece should be controlled strictly when the fixture is installed; (2) the positioning accuracy of all parts should be controlled strictly when the fixture is installed; (4) the positioning accuracy of all parts should be controlled strictly when the fixture is installed The selected datum should ensure the completion of as many processing contents as possible; (5) during batch processing, the part positioning datum should coincide with the tool setting datum of workpiece coordinate system as much as possible; (6) when multiple clamping is needed, the datum should be unified before and after.
Determination of fixture for machining center:
- The basic requirements of the fixture: (1) the clamping mechanism shall not affect the feed, and the processing part shall be open; (2) the fixture can be installed in the machine tool in a directional way; (3) the rigidity and stability of the fixture shall be good.
- Types of commonly used fixtures: (1) general fixture: such as vise, dividing head, chuck, etc.; (2) modular fixture: modular fixture is composed of a set of universal components with standardized structure and dimension; (3) special fixture: fixture specially designed and manufactured for one or several similar processing items; (4) modular fixture Adjustable fixture: the combination of modular fixture and special fixture can not only ensure the accuracy of processing, but also make clamping more flexible; (5) multi position fixture: the fixture that can clamp multiple workpieces at the same time; (6) Group Fixture: it is specially used for clamping workpieces with similar shape, size and positioning, clamping and processing methods.
The selection principle of machining center: 3
(1) On the premise of ensuring the machining accuracy and production efficiency, the general fixture is preferred;
(2) Simple special fixture can be considered for batch processing;
(3) Multi position fixture and high efficiency special fixture such as air pressure and hydraulic pressure can be considered for mass processing;
(4) Group fixture should be used when group process is adopted;
- The best clamping position of the workpiece on the machine tool table: the clamping position of the workpiece should ensure that the workpiece is within the processing stroke range of each axis of the machine tool, and make the length of the tool as short as possible, so as to improve the processing rigidity of the tool.
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