Before machining with 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 methods for measuring compensation parameters now include: trial cutting method, use of electronic probes, mechanical and optical tool presetters. The trial cutting method is rarely used, electronic probes are expensive, and the tool presetter is widely used outside the machine. Use an electronic measuring head or a tool presetter to align the tool, both under static conditions. In practical cutting, due to the influence of cutting force and vibration, the practical results after machining are not completely consistent with the static tool setting data. When the tool quality is reliable and the machining process is stable, there is a correction amount of 0.01mm-0.02mm in the axial and radial directions. The operator needs to adjust based on their experience according to the specific situation of the vertical machining center and tool system.
1. Before machining, the cutting force should be roughly estimated based on the machining center, cutting parameters, cutting tools, and workpiece data, using some existing empirical formulas.
2. Loosen the nut so that the tension spring only accepts the weight of the measuring rod. Based on the cutting force and spring stiffness, tighten the nut and compress the spring. Make the elastic force of the tension spring equal to the cutting force.
3. Install the measuring equipment according to the diagram and place it on the workbench. After placing dial gauge 6 on top of measuring block 7 (or stacking several measuring blocks), set the gauge head to "0" to determine a measurement benchmark.
4. Use a dial gauge to mark the outer surface of measuring rod 3. Lower spindle 5 so that tool 4 touches the outer surface of the measuring rod and continues to compress tension spring 2, causing it to deform. Record the reading. At this moment, nut 9 and washer 8 should be out of touch with measuring seat 1, and the tool should receive the same tension spring force as the cutting force. The deformation or neglect displayed by the dial gauge reading should be considered, depending on the situation.
5. Remove the dial gauge and raise the tool back to its original position.
6. Tool extension length=machining center z-axis stroke - current z-axis coordinate value - gauge block length - dial gauge reading
Without considering the errors in the measuring equipment of the machining center, as well as the production errors and wear of the machining center worktable, the comparative method is used for measurement, with the cooperation of measuring blocks and micrometers. The maximum measurement error is 0.03mm.
If the cutting force changes significantly during the machining process, it can be weighted uniformly based on the effect of different cutting forces on the cutting process. When performing important surface processing, if there is a significant difference in cutting force, corresponding tool alignment operations can be performed for each cutting force, and all results can be input into the CNC system. During cutting, specific compensation parameters can be called separately.
The tool presetter should be designed based on the specifications of the machining center, cutting tools, workpieces, and cutting parameters. The two ends of the tension spring should be tightly ground flat, with appropriate stiffness, capable of producing the required elastic force, and the elastic force should be within its operating range. The tool should be slowly fed in units of 0.01mm before and after touching the surface of the measuring rod. To ensure the relative movement between the sleeve and the measuring rod, H6/H5 clearance cooperation can be selected. When the tool compresses the tension spring, it is possible to cause the two axes of the measuring seat and the measuring rod to deviate, resulting in a skewed outer surface of the measuring rod and increasing measurement errors. The surface of the measuring rod can be finely ground to achieve a flatness level of 3-4. When measuring, the dial gauge is rotated around the outer ring of the measuring rod, and the uniform value of the small and large values is taken as the reading of the dial gauge.
