Considering the axial cutting force vertical machining center tool extension length measurement

Before processing the machining center, the user must measure the compensation parameters such as the extension length of the tool on the spindle and its diameter. At present, commonly used compensation parameter measurement methods are: trial cutting method, using electronic probe, mechanical type, optical type tool setting instrument. The trial cutting method has been rarely used, the electronic probe is expensive, and the tool is used outside the machine and is widely used. The tool is aligned with an electronic probe or a tool setting tool under static conditions. In actual cutting, the actual results after machining are not exactly the same as the static tool setting data due to the influence of cutting force and vibration. When the tool quality is reliable and the machining process is stable, the axial and radial directions have a correction amount of 0.01mm-0.02mm [1]. It needs to be adjusted by the operator according to the specific conditions of the machine tool and the tool system.
The author has designed a simple tool setting device for tool setting on the machine tool for the vertical machining center of Taiwan Youjia Company purchased by this unit. Based on this improvement, the tool setting instrument shown in the figure is designed. Taking into account the effect of the cutting force in the axial direction, the error caused by the axial cutting force can be reduced to some extent. The steps are as follows:
1 Before the machining, the tool is roughly estimated according to the machining center, cutting amount, tool, workpiece material, and some existing empirical formulas.
2 Loosen the nut so that the spring only bears the weight of the measuring rod. Then tighten the nut and compress the spring according to the cutting force and spring stiffness. The spring force is made substantially equal to the cutting force.
3 Place the measuring device as shown and place it on the workbench. After the dial gauge 6 hits the top of the gauge block 7 (or the stack of gauge blocks), the head is set to "0" to determine a measurement reference.
4 Hit the upper surface of the measuring rod 3 with a dial gauge. Lower the spindle 5 so that the tool 4 contacts the upper surface of the measuring rod and continue to compress the spring 2 to deform it and record the reading. At this time, the nut 9 and the spacer 8 should be out of contact with the measuring seat 1, and the tool is subjected to a spring force substantially the same as the cutting force. Deformation or neglect displayed by the dial gauge reading,
Consider it, depending on the situation.
5 Remove the dial gauge and raise the tool back to the origin.
Tool extension length = machining center z-axis stroke - at this time z-axis coordinate value - gauge block length - dial gauge reading does not take into account the error of the machining center measuring device, regardless of the manufacturing error and wear of the machining center table, using the comparison method Measurement, gauge block, dial gauge fit, the measured limit error is 0.03mm.
If the cutting force changes greatly during the machining process, the weighted average can be performed according to the action of different cutting forces in the cutting. When performing important surface machining, if the cutting force differs greatly, the corresponding tool setting operation can be performed for each cutting force. All the results are input into the CNC system, and the specific compensation parameters are respectively called when cutting.
The tool setting tool should be designed according to the machining center specifications, tools, workpieces and cutting amount. The ends of the spring are tightly ground and the stiffness is appropriate. The required spring force should be generated and the spring force should be within the working range.
Before and after the tool touches the surface of the measuring rod, it should be fed slowly in units of 0.01 mm. In order to ensure the relative movement of the sleeve and the measuring rod, a H6/h5 clearance fit can be used. When the tool compresses the spring, it may cause the two sides of the measuring rod and the measuring rod to be skewed, which causes the upper surface of the measuring rod to be inclined, which increases the measurement error. The upper surface of the measuring rod can be finely ground to a flatness of 3-4. When measuring, dial the dial on the outer surface of the upper surface of the measuring rod, taking the average of the minimum and maximum values ​​as the dial gauge reading.

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