Why is it necessary to correct the cutting tool before machining on a vertical machining center

Before machining on a vertical machining center, the user must measure compensation parameters such as the extension length and diameter of the tool on the spindle. The commonly used compensation parameter measurement methods currently include: trial cutting method, use of electronic probe, mechanical and optical tool alignment instrument. The trial cutting method is rarely used, and electronic measuring heads are expensive. The tool setting instrument is widely used outside the machine. Use an electronic probe or tool setting instrument to set the tool under static conditions. During actual cutting, due to the influence of cutting force and vibration, the actual results after machining are not consistent with the static tool alignment data. When the tool quality is reliable and the machining process is stable, there is a correction of 0.01mm-0.02mm in the axial and radial directions. The operator needs to adjust based on experience according to the specific situation of the vertical machining center and tool system.

  • 1. Before machining, set the cutting tool and roughly estimate the cutting force based on the machining center, cutting amount, cutting tool, and workpiece material using existing empirical formulas.
  • 2. Loosen the nut so that the spring only bears the weight of the measuring rod. According to the cutting force and spring stiffness, tighten the nut and compress the spring. Make the spring force basically equal to the cutting force.
  • 3. Install the measuring device as shown in the diagram and place it on the workbench. After hitting the dial gauge 6 on the top of gauge block 7 (or a combination of several gauge blocks), set the gauge head to “0” to determine a measurement reference.
  • 4. Use a dial gauge to hit the surface of measuring rod 3. Lower spindle 5 so that tool 4 contacts the upper surface of the measuring rod, and continue to compress spring 2 to cause deformation. Record the reading. At this point, the nut 9 and gasket 8 should be out of contact with the measuring seat 1, and the tool should withstand spring force that is basically the same as the cutting force. The deformation or neglect displayed by the dial gauge reading shall be taken into account, depending on the situation.
  • 5. Remove the dial indicator and raise the tool back to the original point.
  • 6. Tool extension length=machining center z-axis stroke – coordinate value of z-axis at this time – length of gauge block – dial gauge reading

Without considering the error of the measuring device of the vertical machining center, the manufacturing error and wear of the machining center workbench, the comparison method is used for measurement, and the measurement limit error is 0.03mm with a combination of gauge blocks and dial indicators.

If there is a significant change in cutting force during the titanium 5 axis machining process, it can be weighted average based on the effect of different cutting forces in the cutting process. When performing important surface machining, if there is a significant difference in cutting forces, corresponding tool adjustment operations can also be performed for each cutting force, and all results can be input into the CNC system. During cutting, specific compensation parameters can be called up separately.

The tool alignment instrument should be designed specifically based on the specifications of the machining center, cutting tools, workpieces, and cutting amounts. The two ends of the spring should be tightly ground flat, with appropriate stiffness and should be able to generate the required elasticity, and the elasticity should be within its working range. Before and after the tool contacts the surface of the measuring rod, it should be slowly fed in units of 0.01mm. To ensure the relative movement between the sleeve and the measuring rod, a H6/h5 clearance fit can be used. When the tool compresses the spring, it may cause the axis of the measuring seat and measuring rod to deviate, causing the upper surface of the measuring rod to tilt and increasing measurement error. The upper surface of the measuring rod can be finely ground to achieve a flatness of 3-4 levels. When measuring, the dial indicator should make a circle on the outer surface of the measuring rod, and the average of the small and large values should be taken as the reading of the dial indicator.