JPS6026663B2 - Corner cut-in reduction control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for reducing gouges at corners that occur during tracing control.

In the profiling method, in which a stylus is moved along the model and the movement of the tool is controlled by position signals generated from the stylus, the work piece is ground according to the model. In this case, a large tracing error occurs due to inertia and the like.

For example, when copying as shown in Fig. 1, if the control contours 1, 2 form a corner at part C, the stylus moving in the direction of arrow F along the contours 2, S
changes direction 90o at corner C and moves in the direction of arrow F2 along contour line 2, but due to inertia etc., the direction cannot be changed instantaneously, and as shown by the dotted line, the It bites into the corner, then returns to its original position due to feedback control, and moves along contour line 2. In order to reduce the amount of biting, it is effective to reduce the feed speed at the corner, and in order to perform such control, it is first necessary to detect the corner. There are the following methods:

In other words, the stylus S moving along the contour line Y,
A displacement signal of y in the direction perpendicular to the line is generated by receiving a reaction force from the line, but when it hits the corner C, a displacement signal of x in the direction of the line appears, and the resultant displacement signal is Godajodo y2. This displacement signal x gradually increases from zero, while the displacement signal y gradually decreases until the stylus is on the line.
By the time the vehicle starts traveling along , the value x becomes the same as the previous value y, and the value y becomes zero. Incidentally, the displacement symbols Go x and Go y both represent the absolute value of the displacement. Therefore, corner portions can be detected by detecting temporal changes in the length of the corner. However, with this method, the corner detection signal cannot be obtained large enough, and detection tends to be delayed.

In this respect, the present invention makes it possible to obtain a large detection signal and further reduce the amount of biting. The present invention moves a stylus along a model, detects a corner of a plane where scanning control is performed based on temporal changes in each coordinate axis component of a displacement signal output by the stylus, and detects the tool feed rate at the corner. In a cut-in reduction control method that reduces the amount of cut-in at the inner periphery of a corner by decreasing the command, Detecting the amount of change over time and using this as a signal indicating the corner portion,
The present invention is characterized in that the feed speed command at the corner portion is reduced by this signal, and this will be described in detail below with reference to an embodiment. The x and y axis coordinate components of displacement occur as described above before and after the corner, but there is a time lag.

In other words, as shown in Fig. 4, the displacement x (indicated by ko, ko, ko, y (indicated by 2 in this case) maintains the previous state "1" until time t2, which is later than time t, and then gradually decreases, becoming "0" at a time later than time t, and thereafter. The stylus will move along line 2 in the y-axis direction. If there is such a time lag, the amount of change will be small if we take Go=Nogox20goy2. In this respect, the present invention calculates the amount of change in x+y, and this method allows a large amount of change to be obtained. FIG. 2 shows a circuit that generates a speed command for scanning control, 1 to 3 are amplifiers, 4 is a displacement synthesis circuit, 5 is a normal velocity generation circuit, 6 is a tangential velocity generation circuit, 7 is a distribution circuit,
8 is a switching circuit, and 9 is an indexing circuit, which operate in a known manner.

That is, the amplifiers 1, 2, and 3 have the displacement x from the stylus,
The y- and z-axis components and the x-, y-, and z-axis components are inputted, amplified, and then added to the displacement synthesis circuit 4, where they are processed as follows. The result is a composite displacement signal. This displacement is compared to the reference value by the comparator 11.
The difference between the two is calculated, and the signal is applied to circuits 5 and 6 to generate a normal velocity command VN for correction and a tangential velocity command V for the feed speed command. On the other hand, the switching circuit sends displacement signals x, y,
Select any two of dz and output them to the indexing circuit 9 or the like. Assuming that scanning control is now being performed on the x, y plane, the outputs of the switching circuit 8, , z2 are as follows. The indexing circuit 9 uses these signals to
The feeding direction is determined in the form of in8 and cos8, and these are input to the distribution circuit 7. The distribution circuit 7 uses these signals to calculate the x-axis component Vx and y-axis component Vy of the feed rate, and instructs these to the servo system of the stylus and tool to reduce the amount of bite at the corner as described above. It is better to reduce the feed rate command VT. Biting reduction circuit 1
0), corner detection is performed from signals 2 and 2, and control signal C for reducing speed command VT is performed.
Output S. Figure 3 shows the details. 15 in Figure 3
1 is an adder, 16 is a differentiating circuit consisting of a capacitor C and a resistor R, and 17 is a comparator receiving a reference voltage Vtef.

Further, D is a diode, R2 is a resistor, and Tr is a transistor, and these constitute a circuit that drops the speed command VT to ground. Further, C is a capacitor, which is inserted in parallel to the series circuit of the resistor R2 and the transistor Tr, and together with the resistor R constitutes a circuit for slowly restoring the speed command VT.
Next, to explain the operation of this cut-in reduction circuit, the displacement signals 1, 2, in this example, The output of this differentiation circuit 16, from which the differential value is determined, is as shown in FIG. 4, Vd.

The comparator 17 compares this output Vd with a reference voltage Vref, and outputs a signal Vc which becomes "1" while Vd>Vref. The transistor Tr is turned on by this signal Vc, and the feed speed command VT is grounded through the path D-R2-Tr2, thereby making it zero. When the signal Vc disappears, that is, when the corner ends, the transistor Tr turns off and D
Charging starts along the path -C, but this charging ends soon, and thereafter Vr returns to its initial state as shown in FIG. In this way, the feed speed at the corner portion is reduced, and the amount of biting is reduced. A comparison of the method of the present invention and the method of detecting a corner portion based on the time change of y2 is as follows.

If the displacement signal x that appears when it hits the cope part is divided into △ (A is the absolute value), the displacement amount A of the detection signal of the conventional method
,, that of the present invention △2 is △・=ノgo〆10△go2-goy〒
Goy (10 horses) -w -△do2 2doy △2=(goy+△go〉-goy=△go△go2 △go(2doy1△go) △2 -△,= △Go-Friend 2 Goy >0 ・ ... △2>△・ .

That is, the detection amount of the present invention is larger, and therefore it is faster.
It is possible to perform reliable control and reduce the amount of biting in corners.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the operation of the stylus at the corner;
FIG. 2 is a block diagram showing the configuration of a scanning speed command circuit, FIG. 3 is a block diagram showing the configuration of a corner detection circuit according to the present invention, and FIG. 4 is a waveform diagram for explaining its operation. In the drawing, C is a corner portion, x and y are coordinate axis components of displacement, and VT is a feed rate command. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. Move the stylus along the model, detect the corner of the plane where the tracing control is performed based on the temporal change in each coordinate axis component of the displacement signal output by the stylus, and set the tool feed rate command at the corner. In the cut-in reduction control method of reducing the cut-in amount at the inner circumference of a corner, the time-based Detecting the amount of change and using it as a signal indicating the corner,
A method for controlling gouge reduction at a corner portion, characterized in that a feed speed command at the corner portion is reduced based on the signal.