JPH0645098B2 - Highly accurate tool compensation method for cutting tools with symmetrical cutting edges - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly accurate tool correction method for a tool having a symmetrical cutting edge when precisely cutting a spherical surface or an aspherical surface such as an optical lens or a reflecting mirror in a lathe. It is about.

2. Description of the Related Art Conventionally, in order to cut a spherical surface, an aspherical surface, or the like of an optical lens or a reflecting mirror in an ultra-precision lathe, it is usual to use a serial diamond tool. The cutting edge position of this cutting tool is a point where it contacts the workpiece on the tip nose R surface that changes depending on the feed direction, and when machining with NC, the positioning accuracy of the cutting edge position in the feed direction greatly affects the machining accuracy. Therefore, highly accurate tool compensation is required. For this reason, in the past, trial cutting was performed to measure the machined surface accuracy,
This was repeated many times until a satisfactory finish was obtained.

Problems to be solved by the invention The method of performing trial cutting many times described in the conventional technique is wasteful of time and labor, and the tool is worn out by several trial cuttings, resulting in shortened tool life. Have a point.

The present invention has been made in view of such problems of the conventional technique, and an object of the present invention is to provide a highly accurate tool correction method in the feed direction of a cutting tool having a symmetrical cutting edge. To do.

Means for Solving the Problems In order to achieve the above object, a highly accurate tool correction method for a cutting tool having a symmetrical cutting edge according to the present invention provides an end surface of a workpiece gripped by a spindle chuck with an NC command. The R groove having an arbitrary diameter is cut by a cutting tool having a symmetrical cutting edge for positioning, and the sensor is moved with respect to the end face in a direction orthogonal to the rotation center of the workpiece, and the R
The diameter of the deepest part of the groove is obtained, and the error between the obtained diameter and the X-axis command value at the time of cutting the R groove is calculated and used as a correction value.

Action R-groove is cut on the end face of the workpiece with a cutting tool having a symmetrical cutting edge for positioning, the X-axis command value at this time is stored, and the non-contact type sensor rotates the end face of the workpiece at a constant speed. Between the peaks of the peak representing the deepest part of the R groove in the displayed image by measuring the measurement result across one axis and taking the time on one axis and taking the distance between the sensor and the end surface on the other axis. The actual diameter of the R groove is calculated from the distance (time), and the tool is corrected using an error between the actual diameter and the X-axis command value stored previously as a correction value.

Example An example will be described with reference to FIGS. 1 to 6. In a known ultra-precision lathe, a headstock 1 is mounted by a NC so that it can be moved and positioned on a slide guide surface in the Z-axis direction that is cut on the upper surface of a slide base fixed to the left side on a bed (not shown). A chuck 2 is fitted to the tip of a spindle that is rotatably supported by the spindle stock 1. Furthermore, an X machined on the upper surface of the slide base fixed on the right side of the bed
A moving table 3 is mounted on the slide guide surface in the axial direction so as to be movable and positionable by NC, and a bite 5 having a symmetrical cutting edge on the moving table 3 via a bite holder 4.
Is attached so that it faces the chuck side in the Z-axis direction and is detachable. Further, on the moving table, a sensor base 9 whose height can be adjusted in the vertical direction is provided with a sensor 6 facing the chuck side in the Z-axis direction and mounted at the same height as the center of rotation of the spindle. As the sensor 6, a non-contact type of capacitance type is used, and since the measuring range is surface measurement, the displacement is measured as an average value of the surface to be measured. For example, as shown in FIG. When the sensor is moved at an average constant speed with respect to the measurement surface to measure the square groove, the output figure of the sensor displayed on the CRT screen attached to the measuring device shows the corner groove as shown in FIG. It is displayed as a drool. Therefore, with this sensor R
When the groove is measured, the R groove is displayed as a sharply pointed figure, which is very convenient for finding the deepest part of the R groove.

Next, the operation of this embodiment will be described. First, on the end surface 8a of the workpiece 8 gripped by the spindle chuck 2, an R groove 8 of an arbitrary diameter is given by an NC command by a cutting tool 5 for positioning.
Turn b. Next, the headstock 1 is moved in the Z-axis to position the sensor 6 at a position where the gap between the sensor 6 and the end surface 8a becomes a predetermined amount, and the moving table 3 is moved in the X-axis direction to move the sensor 6 near the outer periphery of the workpiece 8. After the measurement is started at the measurement start position, the sensor 6 is moved at a constant speed in the direction traversing the R-groove 8b in the X-axis direction to perform the measurement. As shown in FIG. 4, this measurement result is displayed on the CRT7 screen attached to the measuring device with time plotted on the horizontal axis and displacement on the vertical axis plotted on the vertical axis. Then, the diameter of the deepest portion of the R groove is obtained by calculation from the distance T (time) on the horizontal axis from the tips a to b representing the deepest portion of the R groove 8b of the displayed figure, and the R groove is cut first. Using the error between the X-axis command value at this time and the obtained diameter as a correction value, tool correction in the X-axis direction is performed so that the position of the cutting edge of the cutting tool exactly matches the positioning command position of NC.

The method for accurately adjusting the sensor 6 to the height of the rotation center of the workpiece 8 is to change the height of the sensor base 9 and perform several measurements.
When the diameter of the R groove 8b has the largest value, the height can be determined by the height.

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it has the following effects.

R-groove of arbitrary diameter is cut by NC command on the end face of the work held by the spindle chuck, and the non-contact sensor is moved at a constant speed with respect to the end face in the direction orthogonal to the rotation center of the work. Accurately determine the diameter of the R-groove using the easy-to-find display pattern of the contact type sensor, and calculate the determined diameter and NC at the time of cutting.
Since the tool correction is performed by using the error from the command value as the correction value, it is possible to accurately perform tool correction in the feed direction of the cutting tool having a symmetrical cutting edge without performing trial cutting, spherical surface, When processing the aspherical surface, it is not necessary to consider the position error amount, and the processing can be performed with high accuracy and high efficiency.

[Brief description of drawings]

FIG. 1 is a perspective explanatory view showing that an R groove is cut on an end face of a workpiece with a cutting tool having symmetrical cutting edges, and FIG. 2 is a perspective explanatory view showing a measurement made by a non-contact sensor. FIG. 3 is a cross-sectional view showing a non-contact type sensor during measurement of the end surface of a workpiece, FIG. 4 is a view showing a display graphic of the measurement result of FIG. 3, and FIG. FIG. 6 is an explanatory view showing a sensor, and FIG. 6 is a view showing a display graphic of the measurement result of FIG. 2 ... Spindle chuck 5 ... Bite with symmetrical cutting edge 6 ... Sensor, 8 ... Workpiece 8b ... R groove

Claims (1)

[Claims] 1. A left and right symmetrical cutting edge for positioning an R groove (8b) of an arbitrary diameter on an end surface (8a) of a workpiece (8) gripped by a spindle chuck (2) according to an NC command ( Cutting in 5), the sensor (6) is moved with respect to the end face in a direction orthogonal to the rotation center of the workpiece, and the diameter of the deepest part of the R groove is calculated.
A highly accurate tool correction method for a tool having a symmetrical cutting edge, which is characterized by calculating an error from an X-axis command value at the time of groove cutting to obtain a correction value.