Before machining the vertical 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, the commonly used compensation parameter measurement methods are: trial cutting method, electronic probe, mechanical and optical tool setting instruments. The trial cutting method is rarely used, the electronic probe is expensive, and the tool setting instrument is used outside the machine and has a wide range of applications. Tool calibration with electronic probe or tool setting instrument is performed under static conditions.
In actual cutting, due to the influence of cutting force and vibration, the actual results after machining are not completely consistent with the static tool setting data. When the quality of the tool is reliable and the machining process is stable, the axial and radial correction amount is 0.01mm-0.02mm. It needs to be adjusted by the operator based on the specific conditions of the vertical machining center and the tool system.
The steps for measuring the tool extension length of the vertical machining center are as follows:
- 1. Before machining, use some existing empirical formulas to roughly estimate the cutting force based on the machining center, cutting amount, tool, and workpiece material.
- 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. The spring force is basically equal to the cutting force.
- 3. Install the measuring device as shown in the figure and place it on the workbench. After the dial gauge 6 is hit on the top of the gauge block 7 (or several gauge blocks are superimposed), set the gauge head to "0" to determine a measurement standard.
- 4. Use a dial indicator to mark the upper surface of the measuring rod 3. Lower the spindle 5, make the cutter 4 contact 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 washer 8 should be out of contact with the measuring seat 1, and the tool bears the spring force which is basically the same as the cutting force. Deformation or omission shown by the dial gauge reading shall be considered, depending on the situation.
- 5. Remove the dial indicator and raise the tool back to the origin.
- 6. Tool extension length = z-axis stroke of machining center-z-axis coordinate value at this time-gauge block length-dial indicator reading
Regardless of the error of the measuring device of the machining center, the manufacturing error and wear of the worktable of the machining center are not considered, the comparison method is used for measurement, the gauge block and the dial indicator are matched, and the limit error of the measurement is 0.03mm.
If the cutting force changes greatly during the machining process, it can be weighted and averaged according to the effect of different cutting forces in the cutting process. When performing important surface processing, if the cutting force differs greatly, you can also perform the corresponding tool setting operation for each cutting force, input all the results into the CNC system, and call specific compensation parameters during cutting.
The tool setter should be specifically designed according to the specifications of the machining center, tools, workpieces, and cutting parameters. The two ends of the spring should be ground tightly, the stiffness should be appropriate, the required elasticity should be generated, and the elasticity should be within its working range. Before and after the tool touches the surface of the measuring rod, it should be fed slowly in units of 0.01mm. In order to ensure the relative movement of the sleeve and the measuring rod, H6/h5 clearance fit can be used. When the tool compresses the spring, it may cause the two axes of the measuring seat and the measuring rod to deviate, causing the upper surface of the measuring rod to tilt and increase the measurement error. The upper surface of the measuring rod can be finely ground to make its flatness reach 3-4. When measuring, the dial indicator makes a circle on the upper surface of the measuring rod, and the average value of the minimum and maximum values is taken as the dial indicator reading.
