JPS625753B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a numerically controlled grinding machine that processes a workpiece and dresses the grinding wheel by controlling the feed of the grinding wheel based on numerical control data programmed in advance. relates to a numerically controlled grinding machine in which the dressing of the grinding wheel is carried out using a dressing tool installed on the table. To automatically correct the feeding amount of a car and to perform accurate dressing without having to accurately program the position of the tip surface of a dressing tool.

Another object of the present invention is to prevent the position of the retreating end of the grinding wheel machining surface, which has been set based on the sizing signal as a reference, from changing even when the grinding wheel is corrected, so that grinding can be performed by constant feed after the grinding wheel is corrected. The aim is to enable highly accurate machining even when the process is performed.

In a general numerically controlled grinding machine, a dressing tool is provided on a table, and the feeding of the grinding wheel is controlled based on numerical control data to perform dressing of the grinding wheel. Therefore, in order to perform accurate dressing in such numerically controlled grinding, it is necessary to accurately measure the position of the tip surface of the dressing tool and program numerically controlled data. However, since the dressing tool is generally attached to the side of the tailstock, it is very difficult to accurately measure the position of the tip surface of the dressing tool. It is often shifted from the tip surface position. For this reason, when dressing the grinding wheel on a conventional numerically controlled grinding machine, the amount of cut of the grinding wheel changes due to the deviation in the position of the tip surface, resulting in a state of insufficient cutting or over-cutting.
It was not possible to perform accurate dressing.

The present invention has been made to eliminate such conventional drawbacks, and the present invention has been made to eliminate the drawbacks of the conventional grinding wheel. The amount of positional deviation of the dressing tool is detected by detecting how much the position deviates from the theoretical position, and the depth of cut during dressing is corrected according to the amount of deviation to ensure accurate dressing. In addition, the amount of backward movement of the grinding wheel after dressing is also corrected according to the amount of deviation, thereby preventing the positional deviation of the grinding wheel processing surface at the backward end position before and after dressing. It is something.

Embodiments of the present invention will be described below based on the drawings. In Figure 1, 10 is the bed of the grinding machine,
In front of this bed 10 is a slide table 11.
is designed to be movable in the left-right direction (Y-axis direction), and is moved in the Y-axis direction by a pulse motor 12 attached to the side surface of the bed 10. On this slide table 11, a headstock 15 that supports a main shaft 14 that is rotationally driven by a motor 13, and a tailstock 17 that supports a tailstock center 16 are placed. A spindle center 18 and a drive pin 19 are fixed to the shaft 14 . A workpiece W is held between the headstock center 18 and the tailstock center 16, and is engaged with a drive pin 19 via a drive metal.

On the other hand, behind the bed 10, a grindstone head 22 that supports a grinding wheel 21 that is rotationally driven by a grinding wheel drive motor 20 is arranged so that it can move in a direction perpendicular to the axis of the workpiece W (X-axis direction). It is connected to a pulse motor 23 attached to the rear end of the bed 10 via a feed screw (not shown). These pulse motors 12 and 23 are connected to pulse motor drive circuits 25 and 26, respectively, to which command pulses are given from a numerical control device 24, and when command pulses are given to the pulse motor drive circuits 25 and 26, the number of command pulses is changed. The grindstone head 22 and slide table 11 are moved accordingly.
As a result, the relative position between the grinding wheel 21 and the workpiece W is changed, and the workpiece W is ground. Further, a dressing tool 27 for repairing the grinding wheel is fixed to the side surface of the tailstock 17 on the grinding wheel side.
Dressing of the grinding wheel 21 is also performed by changing the relative positions of the grinding wheel 22 and the slide table 11.

Furthermore, the workpiece W on the slide table 11
A measuring head 28 is provided at a position opposite to the grinding wheel 21 across from the grinding wheel 21 for engaging the machined surface of the workpiece W to measure the dimensions of the machined surface, and is moved forward and backward by a hydraulic cylinder (not shown). It's becoming like that. The signal from the measuring head 28 is sent to a sizing device 29 which outputs a sizing signal when the dimension of the machined surface reaches a predetermined size.
It is beginning to be given to In this example,
When the dimensions of the machined surface reach the dimensions of completion of rough grinding, a sizing signal AS1 is output, and when the dimension of the machined surface reaches the finished dimension, a sizing signal AS2 is output.

FIG. 2 shows a numerical control device 24 which distributes pulses to pulse motor drive circuits 25 and 26 based on a preprogrammed program, thereby machining the workpiece W and dressing the grinding wheel 21. 2, which shows an example in which the forward end position of the grinding wheel 21 is controlled by a sizing signal sent from a sizing device 29 to machine the processing surface of a workpiece W.

In this figure, DS10 to DS23 are the workpiece W
This is a digital switch that presets the necessary control data after machining and dressing the grinding wheel 21. DS10 to DS16 are preset with control data for workpiece machining, and DS20 to DS
In 23, control data for dressing is preset. The control data for workpiece machining set from DS10 to DS16 includes position data such as table index position, grindstone base position, grindstone head forward end position, and pulse distribution speed for dry grinding, fine grinding, and fine grinding. There is speed data to specify and depth of cut data to specify the depth of cut during dry grinding.
Among these data, the position data of the grinding wheel head is programmed using absolute coordinate data that expresses the distance between the processing surface of the grinding wheel 21 and the center of the workpiece in terms of the radius of the workpiece, and the depth of cut data is expressed as the radius of the workpiece. It is designed to be programmed with incremental amounts. It should be noted that the finishing dimension of the workpiece is preset at the forward end position of the grindstone head at the position of the grindstone head 22 on the program when the workpiece W reaches the finished dimension. Furthermore, the table index position data is programmed using absolute coordinate data.

On the other hand, the data for dressing set in DS20 to DS23 includes data on the table index position, rapid feed amount, depth of cut, and traverse amount, and among these data, only the table index position is programmed as an absolute value. However, other data are designed to be programmed with incremental values. In addition,
The rapid feed amount of the grinding wheel 21 is determined by measuring the distance from the processing surface of the grinding wheel 21 to the tip surface of the dressing tool 27 when the grinding wheel 21 is located at the original position in the program, and setting the measured value. In the numerically controlled grinding machine according to the invention, since the rapid feed amount is corrected according to the deviation of the tip surface of the dressing tool 27, it is not necessary to measure the distance to the tip surface of the dressing tool 27 with high precision.

The variable frequency oscillator 31 generates pulses at a cycle according to the speed data output from the control circuit 30, and the pulses output from the variable frequency oscillator 31 are given to the gate circuit 32 and the movement amount counter 33. It's becoming like that. The movement amount counter 33 is for counting the pulses output from the variable frequency oscillator 31 to detect the movement amount of the grindstone head 22 or the slide table 11.
When a pulse is output from the variable frequency oscillator 31, the command movement amount preset by the control circuit 30 is subtracted, and when the count value becomes zero, a distribution completion signal PGE is output to the control circuit 30. ing. On the other hand, the gate circuit 32 distributes the pulses output from the variable frequency oscillator 31 to each axis, and depending on the direction data output from the control circuit 30, the pulses output from the variable frequency oscillator 31 are distributed to the X axis or Output as positive and negative pulses for the Y-axis. These pulses are applied to pulse motor drive circuits 25 and 26 shown in FIG.
5 and these position counters 34, 35
The machining surface of the grinding wheel 21 and the current position of the slide table 11 stored in the machine are corrected. The contents of these position counters 34 and 35 are displayed externally by position indicators 36 and 37, so that the position of the machining surface of the grinding wheel 21 and the position of the slide table 11 are determined by the work vehicle. will be notified.

The count values of these position counters 34 and 35 are given to a subtracter 38 via gates G1 and G2, and when a calculation command is output from the control circuit 30, the count values of the position counters 34 and 35 are The subtractor 38 calculates the deviation between the stored current position data and the absolute coordinate positioning data set in the digital switch, thereby determining the incremental movement amount.

Furthermore, the count value of the position counter 34 that stores the position of the machined surface of the grinding wheel 21 is controlled by a digital switch.
It is now also given to the calculator 39 that calculates the amount of deviation between the programmed grindstone forward end position set in DS12 and the actual grindstone forward end position when the workpiece W reaches the finished dimensions. There is. As will be described later, this calculator 39 receives a dimensional signal from the dimensional device 29 when the machining of the first workpiece W is completed and the finished dimension is reached after manual dressing.
It is designed to operate only when AS2 is output. The deviation amount register 40 stores the deviation amount of the forward end position of the grinding wheel head calculated by the calculator 39. The deviation amount data stored in this deviation amount register 40 is transmitted to the digital switch DS21 and the control circuit 30. a subtractor 41 connected between
The fast feed amount of the grindstone head 22, which is given to the digital switch DS21 and set in the digital switch DS21, is corrected based on the amount of deviation.

The flip-flop FF is provided to determine whether or not this is the first workpiece machining after manual dressing.When manual dressing is performed, the flip-flop FF is reset and manual dressing is completed. It is set when the first workpiece machining is completed.

The control circuit 30 operates each of the aforementioned circuits in sequence according to an internally stored control program, thereby controlling the machining of the workpiece W and the dressing of the grinding wheel 21, and receives machining commands from the outside.
When GSC is given, the workpiece W is machined, and when a dressing command DSC or DMC is given from the outside, dressing is carried out.
The dressing command DMC is given externally when performing manual dressing.
Only the traverse operation of the slide table 11 is automatically performed. In addition, when a machining command GSC is given after manual dressing, calculation processing is performed to index the slide table 11 to the machining position and to measure the positional deviation of the dressing tool tip surface. It's becoming like that.

Next, the operation of the above-mentioned numerical control device during workpiece machining and dressing will be explained. When the grinding wheel 21 is replaced or when the power is turned on, a discrepancy occurs between the actual position of the processed surface of the grinding wheel 21 and the position of the processed surface of the grinding wheel stored in the position counter 34, so numerical control is performed. Before performing numerically controlled machining based on data, it is necessary to perform manual dressing to match the position of the machining surface of the grinding wheel 21 with the tip surface of the dressing tool, and perform numerical control based on this point. For this reason,
The operator manually dresses the workpiece before starting machining.

First, the operator manually moves the slide table 11 to position the grinding wheel 21 at the index position for dressing on the left side of the dressing tool 27, and then moves the grinding wheel head 22 toward the dressing tool 27. The processing surface of the grinding wheel 21 is positioned at a position advanced by a predetermined amount from the tip of the dressing tool 27. After this, the operator gives a manual dressing command DMC. As a result, the control circuit 30 sets the traverse amount set in the digital switch DS23 in the movement amount counter 33, and then outputs a Y pulse to the pulse motor drive circuit 26 to move the slide table 11 to the left. Then, the slide table 11 is moved to the left by the traverse amount, the count value of the movement amount counter 33 becomes zero, and a pulse distribution completion signal is sent to the control circuit 30.
When PGE is applied, the control circuit 30 sets the traverse amount in the movement amount counter 33 again, and then outputs a Y-axis pulse to the pulse motor drive circuit 26 to move the slide table 11 to the right. As a result, the grinding wheel 21 is dressed so that the processing surface of the grinding wheel 21 is located in the same plane as the tip surface of the dressing tool 27, and when dressing is completed, the grinding wheel 21 returns to the index position before dressing. Positioned. In this way, when manual dressing is completed, the control circuit 30
resets the flip-flop FF and remembers that manual dressing was performed.

When the manual dressing is completed in this way, the working vehicle presses a command switch (not shown) for a machining command, and gives a machining command GSC to the control circuit 30. The control circuit 30 first tests whether the flip-flop FF is in the reset state or the set state to determine whether the machining to be performed is the first machining of the workpiece after manual dressing. . In this case, the flip-flop FF is in the reset state, so
The control circuit 30 determines that this is the first workpiece machining after manual dressing, and indexes the slide table 11 before entering the machining cycle of the workpiece W. The control circuit 30 is first a digital switch.
The rapid feed amount of the grinding wheel 21 during dressing, which is set in the DS 21, is set in the movement amount counter 33, and speed data for fast feed is output to the variable frequency oscillator 31, and then a switching signal is given to the gate circuit 32. The pulses output from the variable frequency oscillator 31 are output to the pulse motor drive circuit 25 as X-axis pulses. As a result, the grinding wheel 21 is moved back by the distance set in the digital switch DS21 and positioned at the temporary origin.
At this time, if the position of the tip surface of the dressing tool 27 is in the programmed position, the grinding wheel 2
Machining surface 1 is at the retreat end position specified by the program.
However, if the tip surface of the dressing tool 27 deviates from the point on the program as shown by the broken line in FIG. It is positioned at the PO' position shown.

In this way, when the grinding wheel 21 is retreated to the temporary home position, the count value of the movement amount counter 33 becomes zero, so the control circuit 30 recognizes that the retreat of the grinding wheel 21 is completed. When it is recognized that the retraction of the grinding wheel 21 has been completed, the control circuit 30 presets the data of the grindstone base position set in the digital switch DS11 in the position counter 34, and also presets the data of the grinding wheel head position set in the digital switch DS20. The data of the table indexing position at the time is set in the position counter 35, and then the indexing operation of the slide table 11 is performed. This indexing of the slide table 11 is performed by using a subtracter 38 to calculate the deviation between the data of the indexing position during machining set in the digital switch DS10 and the table indexing position during dressing preset in the position counter 35. This is performed by calculating and setting it in the movement amount counter 33, oscillating a pulse by the variable frequency oscillator 31, and outputting this pulse to the pulse motor drive circuit 26 as a Y-axis pulse. Thereby, the processing surface of the grinding wheel 21 is positioned at a position opposite to the processing surface of the workpiece W.

When the indexing of the slide table 11 is completed in this way, processing of the workpiece W is started.
In the numerically controlled grinding machine according to the present invention, it is necessary to process at least the first workpiece after manual dressing by controlling the forward end position of the grindstone using a sizing signal from the sizing device. However, in this embodiment, the second and subsequent machining operations are performed by controlling the forward end position of the grindstone head using a sizing signal from the sizing device. FIG. 4 is a cycle diagram showing the feed of the grinding wheel 21 during workpiece machining. Dry grinding feed is performed by the amount set in the digital switch DS13, and then the sizing signal AS1 is sent from the sizing device 29.
The grinding wheel 21 is fed at a rough grinding speed until the sizing signal AS1 is sent out, and when the sizing signal AS1 is sent out, the feeding speed of the grinding wheel 21 is switched from the rough grinding speed to the fine grinding speed. Then, when the sizing signal AS2 is sent out, the feeding is stopped and the grinding wheel 21 is moved backward in rapid traverse.

When the control circuit 30 enters the machining cycle, it first sets the movement amount set in the digital switch DS13 in the movement amount counter 33, and also sets the digital switch DS14 in the variable frequency oscillator 31.
After that, a switching signal is given to the gate circuit 32, and the pulse outputted from the variable frequency oscillator 31 is outputted to the pulse motor drive circuit 25 as an X-axis pulse. As a result, the grindstone head 22 is moved to the forward end position of the idle grinding feed, and the processing surface of the grinding wheel 21 is located at the forward end position PA of the idle grinding feed shown in FIG.

When the dry grinding feed is completed in this way, the control circuit 30 outputs the speed data for rough grinding feed set in the digital switch DS15 to the variable frequency oscillator 31 to oscillate a distribution pulse for rough grinding feed. , this is sent to the gate circuit 3 as an X-axis pulse until the sizing signal AS1 is output from the sizing device 29.
Output from 2. As a result, the grinding wheel 21 is sent toward the workpiece W at a rough grinding feed rate, and rough grinding of the workpiece W is performed. Further, when the dimensions of the workpiece W reach the dimensions for which rough grinding has been completed and the sizing signal AS1 is output from the sizing device 29, the control circuit 30 transmits the speed data set in the digital switch DS16 to the variable frequency oscillator 31. output, and set the pulse distribution speed to a speed suitable for precision grinding. This results in
The feed of the grinding wheel 21 is reduced to a fine grinding speed, and the workpiece W is finely ground.

When the workpiece W reaches the finished size and the sizing signal AS2 is output from the sizing device 29, the grinding wheel 21 stops feeding and returns to the original position at a rapid traverse speed. In the case of W machining, before retracting the grinding wheel 21, the dressing tool 2
Arithmetic processing is performed to determine the displacement of the tip surface position of No. 7. That is, the control circuit 30 controls the sizing device 2
Upon receiving the sizing signal AS2 from 9, the grinding wheel 21
After stopping the sending of
Outputs the data of the forward end position of the grindstone head set in DS12. When a calculation command is given to the calculation unit 39, the calculation unit 39 reads the data output to the bus line B1 and the count value of the position counter 34, and calculates the deviation between them. position counter 3
4, the data of the original position of the grinding wheel set in the digital switch DS11 at the time when the grinding wheel 21 is positioned at the temporary origin is preset as the original position data on the program, and this is set as the data of the original position of the grinding wheel 21.
It will be subtracted as the number advances. The data for the grinding wheel head original position is preset as the distance from the grinding wheel machining surface to the center of the workpiece when the grinding wheel 21 is located at the original position in the program, so when the grinding wheel 21 is positioned at the temporary origin. If the position of the machining surface of the grinding wheel 21 is located at the backward end position PO on the program, the counted value of the position counter 34 will match the finished dimension of the workpiece W when the workpiece W reaches the finished dimension. , digital switch
The deviation from the data of the forward end position of the grinding wheel head set in DS12 is zero.

However, if the position of the tip surface of the dressing tool 27 deviates from the programmed position as shown in FIG. Because the workpiece W deviates from the backward end position PO, the workpiece W reaches the finishing dimension before the grinding wheel 21 is sent to the programmed forward end position, and even if the workpiece W reaches the finishing dimension, the count value of the position counter 34 does not change. does not match the finished dimensions of the workpiece W, but is a value that is shifted by an amount corresponding to the amount of positional shift of the tip surface of the dressing tool 27. Therefore, the calculation unit 39 calculates the count value of the position counter 34 and the digital switch.
When the deviation from the data set in the DS 12 is calculated, a value corresponding to the deviation of the tip surface of the dressing tool 27 is output as the deviation. Then, the deviation calculated by the calculator 39 is stored in the deviation amount register 40 and output to the subtracter 41. Note that when this operation is completed, the flip-flop
FF is set.

When the amount of positional deviation of the tip surface of the dressing tool 27 is calculated in this way, the control circuit 30
After loading the position data of the forward end of the grinding wheel head outputted to the bus line B1 into the position counter 34, the subtracter 38 is used to load the position data of the forward end of the grinding wheel head to the digital switch DS1.
The deviation between the data of the grindstone base position set to 1 and the data of the forward end position of the grindstone loaded into the position counter 34 is calculated, and this is set in the movement amount counter 33 as the retraction amount, and the data is set on the X-axis. Distribute the pulse. As a result, the grinding wheel 21 is accurately returned to its original position on the program, and the processing surface of the grinding wheel 21 is positioned at PO.

When the machining of the workpiece W is completed in this way,
This is followed by machining of a new workpiece or automatic dressing of the grinding wheel 21. If a new workpiece is to be machined, the operator installs the new workpiece in place of the already machined workpiece, and then presses a switch for machining commands. As a result, the control circuit 30 performs control for machining the workpiece, but in this case, since it is the second time machining of the workpiece, the control circuit 30 performs control to determine the indexing operation of the slide table 11 and the amount of deviation of the dressing tool 27. No calculation processing is performed. Note that whether or not the workpiece W is being machined for the second time is determined based on whether the flip-flop FF is set.

On the other hand, when dressing the grinding wheel 21 automatically after processing the workpiece, the operator presses a dressing command switch (not shown) and controls the control circuit 21.
Give dressing command DSC to 0. When the dressing command DSC is given to the control circuit 30,
As shown in FIG. 5, the numerical control device 24 indexes the machining surface of the grinding wheel 21 in front of the dressing tool 27 by moving the slide table 11, and then sends the grinding wheel 21 toward the dressing tool 27. Dressing is performed by making a predetermined amount of cut and traversing the slide table 11.

That is, when the dressing command DSC is given, the control circuit 30 first calculates the deviation between the dressing table index position and the current position of the slide table 11 using the subtracter 38, and calculates the deviation between the dressing table index position and the current position of the slide table 11. The counter 33 is set. Thereafter, predetermined speed data is output to the variable frequency oscillator 31 to generate pulses, and the pulses are output as Y-axis pulses to the pulse motor drive circuit 26 until the count value of the movement amount counter 33 becomes zero. As a result, the slide table 11 is moved to the left in FIG. 1, and the grinding wheel 21 is positioned to the left of the dressing tool 27.

When the indexing of the slide table 11 is completed in this way, the control circuit 30 switches the digital switch.
The rapid traverse movement amount set in the DS 21 is set in the movement amount counter 33, and an X-axis pulse is sent to the pulse motor drive circuit 25 to advance the grinding wheel 21 in rapid traverse. The fast-forward movement amount Lf set in the digital switch DS21 is corrected by the shift amount data Δ stored in the shift amount register 40 by the action of the subtracter 41 described above. That is, the subtractor 41 subtracts the deviation amount Δ from the fast-forward movement amount Lf to correct the fast-forward movement amount. In the case of this embodiment, since the position of the tip surface of the dressing tool 27 is set back from the point on the program, the data of the negative deviation amount -△ is stored in the deviation amount register 40, and the above-mentioned By performing such correction, the grinding wheel 21
is fed by △ more than the rapid feed amount in the program, and the position of the rapid feed forward end of the grinding wheel machining surface is in the same plane as the tip of the dressing tool 27 even if the tip surface of the dressing tool 27 is misaligned. Correctly positioned.

When the rapid forward movement of the grinding wheel 21 is completed in this way, the control circuit 30 switches the digital switch.
A number of pulses corresponding to the depth of cut set in the DS22 are distributed to the X axis to feed the grinding wheel 21 by a predetermined amount, and then a number of pulses corresponding to the traverse distance data set in the digital switch DS23 are fed. The positive and negative pulses are distributed to the Y axis to cause the slide table 11 to make one reciprocation. As a result, the machined surface of the grinding wheel 21 is dressed, but since the rapid feed amount is corrected according to the positional deviation of the tip surface of the dressing tool 27,
Even if the position of the tip surface of the dressing tool 27 deviates from the programmed position, there will be no insufficient or excessive cutting, and dressing will be performed in the best possible condition.

When dressing is completed, the control circuit 30 distributes a number of pulses to the X axis according to the amount of rapid feed corrected by the subtracter 41, and returns the grinding wheel 21 to its original position. And digital switch DS11
The data of the grinding wheel table original position set in is loaded into the position counter 34, and the coordinate deviation caused by the cutting of the grinding wheel 21 is corrected. Since the retraction amount of the grinding wheel 21 is also corrected by the amount of deviation stored in the deviation amount register 40, the position of the processed surface of the grinding wheel 21 is the retraction end position PO before dressing.
be positioned correctly.

Further, the control circuit 30 sets the table movement amount calculated by the subtractor 38 in the movement amount counter 33, distributes pulses to the Y axis, and moves the slide table 11 to the right. Then, when the processing surface of the grinding wheel 21 is indexed to a position opposite to the processing surface of the workpiece and the count value of the movement amount counter 33 becomes zero, the control circuit 30 stops pulse distribution and completes the dressing operation.

In the above embodiment, the rapid feed amount of the grinding wheel was corrected to keep the cutting amount of the grinding wheel constant, but if the amount of deviation of the tip surface of the dressing tool 27 is small, the digital switch DS22 The set depth of cut may be corrected.

In addition, in the above embodiment, the forward end position of the grinding wheel was controlled by the sizing signal from the sizing device to machine the workpiece, but the workpieces from the second grinding wheel onwards were machined using numerical control data. Processing may also be carried out by controlling the feed of the grinding wheel. In such a case, the positional deviation of the grinding surface after dressing due to the positional deviation of the tip surface of the dressing tool affects the machining accuracy after dressing. If the amount of retraction of the grinding wheel after dressing is corrected according to the amount of positional deviation of There is no surface misalignment, and highly accurate workpiece machining is possible.

As described above, in the numerically controlled grinding machine according to the present invention, the positional deviation of the tip surface of the dressing tool is automatically measured, and the feed amount of the grinding wheel during dressing is determined according to the measured positional deviation. Even if the position of the tip of the dressing tool deviates from the point on the program, the grinding wheel will not go into an insufficient or excessive cutting state during dressing, and optimal dressing will be achieved. It will be done. Therefore, there is no need to accurately measure the position of the tip surface of the dressing tool when creating a program, and there is an advantage that the program can be created easily.

In addition, in the present invention, the depth of cut during dressing is corrected according to the amount of positional deviation of the dressing tool, and the amount of backward movement after dressing is also corrected to ensure that the grinding wheel machining surface is in the position before the grinding wheel correction. In the subsequent machining, positioning control is performed using this retreat end position as a reference. Therefore, it is possible to prevent the position of the grinding wheel machining surface from changing before and after dressing when it is located at the retreat end, and after dressing, the grinding wheel can be cut by constant feed without using a sizing signal. There is an advantage that high-precision machining can be performed even if this method is performed.

[Brief explanation of the drawing]

FIG. 1 shows a schematic configuration of a numerically controlled grinding machine according to the present invention, and is a plan view of the grinding machine with a block diagram showing a numerical control device added, and FIG. 2 shows the numerical control device 24 in FIG. 1. A block diagram showing the specific configuration, FIG. 3 is a diagram showing the movement of the grinding wheel during machining of a workpiece, FIG. 4 is a diagram showing the grinding cycle in this example, and FIG. 5 is a diagram showing the movement of the grinding wheel during dressing. It is a diagram showing movement. 10...Bed, 11...Slide table,
12, 23... Pulse motor, 15... Headstock,
17... Tailstock, 21... Grinding wheel, 22... Grinding wheel head, 24... Numerical control device, 25, 26... Pulse motor drive circuit, 27... Dressing tool,
28...Measuring head, 29...Sizing device, 30...
...Control circuit, 31...Variable frequency oscillator, 32...
...Gate circuit, 34, 35...Position counter, 3
9...Arithmetic unit, 40...Difference amount register, 41...
...Subtractor, DS10 to DS23...Digital switch, W...Workpiece.

Claims (1)

[Claims] 1. In a numerically controlled grinding machine that controls the feed of the grinding wheel based on pre-programmed numerical control data to process a workpiece and dress the grinding wheel using a dressing tool placed on a table, The forward end position of the grinding wheel is controlled by the sizing signal from the sizing device, which is positioned at a temporary origin that is set back from the virtual tip surface of the dressing tool by an amount corresponding to the dressing feed amount on the program. A fixed size feeding means for feeding the workpiece to process the workpiece, a position setting means for setting a forward end position on a program of the grinding wheel fed by the fixed size feeding means, and a fixed size feeding means for processing the workpiece by the fixed size feeding means. A position detecting means for detecting the actual forward end position of the fed grinding wheel, and the actual forward end position detected by the position detecting means and the forward end according to the program set in the position setting means. A deviation amount calculating means calculates and stores the deviation amount between the position and the position during the first workpiece machining performed after manual drawing done when the power is turned on, and the deviation calculated and stored by this deviation amount calculating means. a movement amount correction means for correcting the feed amount and the backward movement amount during dressing according to the amount; and after feeding the grinding wheel based on the fixed length feeding means, the grinding wheel is moved back by a certain amount to adjust the processing surface of the grinding wheel. is positioned at a certain backward end position, and then the grinding wheel is corrected by feeding the grinding wheel by the feed amount corrected by the movement amount correction means, and the grinding wheel is moved back by the corrected backward movement amount. and a feed control means for positioning the grinding wheel machining surface at the retreating end position and performing the next machining feed from this retreating end position.