The accuracy of the machining centers affects the quality of the product's machining. As a result, the industry has been researching ways to minimize or even eliminate machining center accuracy issues. So how can you evaluate a machining center's accuracy? In this article, the following four aspects are briefly introduced.
Vertical machining center specimen positioning: The specimen should be positioned along the Y and Z axes at the proper location suitable for the specimen and fixture positioning, and tool length. It should be in the middle of the X-stroke. The agreement between the maker and the user should include any unique instructions for the specimen's location.
Fixing of specimen: The specimen should be easily installed on the special fixture to achieve the starting stability of the tool and fixture. The mounting surface of the fixture and specimen should be straight.
It is important to verify that the specimen's mounting surface and the fixture's clamping surface are parallel. To enable the tool to pierce and mill the whole length of the center hole, an appropriate clamping technique should be applied. To prevent tool and screw interference, it is advised to use countersunk screws to hold the specimen, while other similar methods may also be utilized. The chosen fixation method determines the specimen's overall height.
Material for the test piece, cutting parameters, and tool: The test piece's material, the cutting tool, and the cutting settings are chosen following the manufacturer's and the user's agreement and ought to be noted. The following cutting criteria are advised.
(1) Cutting speed: about 50m/min for cast iron parts; about 300m/min for aluminum parts.
(2) Feed: about (0.05~0.10) mm/tooth.
(3) Depth of cut: all milling processes in the radial depth of cut should be 0.2mm.
The test piece's size: Cutting the test piece more than once results in a smaller shape and a larger hole diameter. To accurately represent the cutting precision of the machining center when used for acceptance inspection, it is advised that the size of the contour machining test piece chosen from the end is consistent with that defined in this standard. The specimen's parameters should be kept within 10% of the characteristic size cab specified in this standard. It can be used again in the cutting test. Before performing a new fine-cutting test on the test piece, a thin cut should be done to thoroughly clean all the surfaces.
