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A Method of Measuring the Accuracy of a Machining Center

1. Positioning of vertical machining center test pieces:

   The test piece shall be placed in the middle of the X stroke and placed along the Y and Z axes at appropriate locations suitable for specimen and fixture positioning and tool length. When there are special requirements for the positioning position of the test piece, it shall be specified in the agreement between the manufacturer and the user.

 

2. Fixing the test piece:

The test piece should be easily installed on a special fixture to achieve maximum stability of the tool and fixture. The mounting surface of the fixture and test piece should be straight.

      The parallelism of the mounting surface of the test piece and the clamping surface of the clamp should be checked. A suitable clamping method should be used to allow the tool to penetrate and machine the full length of the center hole. It is recommended to use a countersunk screw to secure the test piece to avoid interference between the tool and the screw. Other equivalent methods are also available. The total height of the test piece depends on the fixing method chosen.

  

3. The material, knife and cutting parameters of the test piece:

 The material of the test piece and the cutting tool 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: 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 operations should have a radial depth of cut of 0.2 mm.

  

4. Size of the test piece:

If the specimen is cut several times, the outer dimensions are reduced and the aperture is increased. When used for acceptance inspection, it is recommended that the final contoured specimen be the same size as specified in this standard in order to accurately 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 size given in this standard. When the test piece is used again, a thin layer cut should be performed before the new fine cut test to clean all the surfaces before testing.

It is estimated that everyone will encounter another problem in the process of using the machining center. Why does the precision of the machining center deteriorate when used? Did we buy parallel imports?

The machining accuracy of the machining center parts is generally due to the fact that the feed dynamics between the shafts are not adjusted according to the error during installation adjustment, or the drive chain of the machine tool has changed due to wear and tear (such as screw clearance and pitch). Error variation, axial turbulence, etc.). It can be solved by re-adjusting and modifying the amount of gap compensation.

 

 When the dynamic tracking error is too large and the alarm is alarmed, it can be checked whether the servo motor speed is too high; whether the position detecting component is good; whether the position feedback cable connector is in good contact; whether the corresponding analog output latch and the gain potentiometer are good; Whether the corresponding servo drive is normal.

 If the overshoot of the machine tool causes poor machining accuracy, the acceleration and deceleration time may be too short, and the speed change time may be appropriately extended. It may also be that the connection between the servo motor and the lead screw is loose or the rigidity is too poor, and the position can be appropriately reduced. The gain of the ring may be the roundness deviation of the two-axis linkage, which may be caused by the mechanical unadjusted. The positioning accuracy of the shaft is not good, or the compensation of the screw gap is improper, which will cause roundness error when crossing the quadrant.


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