The accuracy of the machining center affects the quality of the machining, so regarding the accuracy of the machining center, the industry has been studying ways to reduce errors as much as possible. So how to judge the accuracy of a machining center? Let’s talk about 4 aspects below:
1. Positioning of the test piece of the vertical machining center
The test piece should be located in the middle of the X stroke, and placed along the Y and Z axes at an appropriate position suitable for the positioning of the test piece and fixture and the length of the tool. When there are special requirements for the positioning of the test piece, it should be specified in the agreement between the manufacturer and the user.
2. Fixing of the specimen
The test piece should be easily installed on a special fixture to achieve the maximum stability of the tool and fixture. The mounting surface of the fixture and the test piece should be straight. The parallelism between the mounting surface of the test piece and the clamping surface of the fixture shall be inspected. Appropriate clamping methods should be used so that the tool can penetrate and machine the full length of the center hole. It is recommended to use countersunk screws to fix the test piece to avoid interference between the tool and the screw. Other equivalent methods can also be used. The total height of the test piece depends on the selected fixing method.
3. The material, knife and cutting parameters of the test piece:
The materials, cutting tools and cutting parameters of the test piece 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: about 50m/min for cast iron parts; about 300m/min for aluminum parts.
2) Feed rate: about (0.05~0.10) mm/tooth.
3) Depth of cut: The depth of cut in the radial direction of all milling operations should be 0.2mm.
4. The size of the test piece
If the test piece is cut several times, the outer dimension is reduced, and the hole diameter is increased. When used for acceptance inspection, it is recommended that the final contour processing test piece size is consistent with the specifications in this standard, so as to faithfully reflect the cutting accuracy of the machining center. The test piece can be used repeatedly in the cutting test, and its specifications should be kept within 10% of the characteristic dimensions given in this standard. When the test piece is used again, before a new fine-cutting test, a thin-layer cutting should be performed to clean all the surfaces before the test.