JPH10202487A - Nc control type work rest device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make motion of a head end of the other rest arm precisely follow motion of an head end of one rest arm by finding a target position to be commanded to a servo motor to drive the other one of the both rest arms by multiplying a target position of the one rest arm by a specified ratio. SOLUTION: A target position and advancing speed of a lower part rest arm 14 are computed by multiplying a target position and advancing speed of an upper part rest arm 12 by a coefficient which is an electronic gear ratio. The target position and command speed of the upper part rest arm 12 are output to a drive unit DUY, and a correction target position and a speed command of the lower part rest arm 14 are output to a drive unit DUV. Consequently, advancing motion of a head end of the lower part rest arm 14 precisely follows advancing motion of a head end of the upper part rest arm 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rest device for supporting a cylindrical workpiece rotating on a predetermined axis against machining resistance during machining. The present invention relates to an NC control type work rest device suitable for use in a grinding machine capable of numerically controlling the movement of an upper rest arm and a lower rest arm.

[0002]

2. Description of the Related Art Generally, an NC control type work rest device used for a grinding machine comprises an upper rest arm which abuts against the outer periphery of a cylindrical work on the opposite side of a grinding wheel to oppose a grinding force in a normal direction, and a cylindrical work rest device. A lower rest arm which abuts against a lower outer periphery of the work and opposes tangential grinding resistance. The feed mechanisms of these rest arms are constituted by feed screw mechanisms driven by individual servomotors, and are of a wide-range type capable of dealing with relatively large-diameter work to small-diameter work.

The upper rest arm is configured to be moved by the same amount as the momentum of the feed screw mechanism driven by the servomotor, while the lower rest arm is pivotally supported at its base by the apparatus body. Therefore, the momentum of the tip of the lower rest arm that contacts the outer peripheral lower surface of the workpiece is moved while enlarging the momentum of the feed screw mechanism driven by the servomotor. In order to harmonize the momentum at the tip of the upper rest arm that contacts the work and the momentum at the tip of the lower rest arm,
A numerical control device for distributing a movement command value decelerated by a so-called electronic gear ratio obtained by multiplying a movement command value to be applied to the upper rest arm servomotor by a predetermined deceleration coefficient to the lower rest arm servomotor. Is programmed. The electronic gear ratio, that is, the ratio between the command value given to the upper rest arm servomotor and that given to the lower rest arm servomotor is determined by the pivot point of the lower rest arm to the apparatus body and the tip of the lower rest arm. It is fixedly set by the ratio of the distance b between the pivot point and the point of application of the turning moment set below the base of the lower rest arm to the distance a from the contact point.

[0004]

However, FIG.
FIG. 1A shows a case where a small-diameter work W1 is supported as shown in FIG.
In the case where the large-diameter work W2 is supported as shown in FIG.
The work support point at the tip of the lower rest arm 14 is SP1 to S
Since the distance a changes to P2, the distance a changes from a1 to a2 (a1> a2). When a conventional rest device having a constant electronic gear ratio is used as a wide-range type for a relatively small-diameter work to a large-diameter work, an error occurs in the follow-up accuracy of the lower rest arm 14 with respect to the upper rest arm 12. Therefore, in the final finishing stage of the grinding process, the workpiece is processed while being held at a position deviated vertically from the axis where it should originally exist, and this is a factor that reduces the final finishing dimensional accuracy of the workpiece. Was.

[0005] Accordingly, an object of the present invention is to provide a wide-range work rest apparatus applicable to small-diameter workpieces to large-diameter workpieces, so that the distal end of the lower rest arm extends over the moving range of the upper and lower rest arms. Is capable of faithfully following the movement of the tip of the upper rest arm.

[0006]

SUMMARY OF THE INVENTION The above-mentioned problems and objects of the conventional rest device are solved and achieved by the following means according to the present invention. NC according to the invention of claim 1
The control type work rest device includes an upper rest arm guided to the device main body so as to be able to advance and retreat toward the work so as to support the outer periphery of the cylindrical work on the opposite side of the processing tool, and a tip end of the work from substantially below the work. A lower rest arm pivotally supported by the apparatus body so as to advance and retreat toward the main body, a feed mechanism including a first servomotor for moving the upper rest arm forward and backward, and a second mechanism for rotating the lower rest arm. In an NC control type workrest device including a feed mechanism including a servomotor and a numerical control device for controlling the first and second servomotors, the numerical control device is configured to perform a control according to a finishing diameter of the work. First command value setting means for setting a first command value for controlling a feed motion of one of the upper rest arm and the lower rest arm; The controls the other feed movement of the upper rest arm and lower rest arm determined according to the finishing size of or the workpiece is determined by multiplying the coefficient 2
A second command value setting means for setting a command value, a correction feed amount setting means for setting a correction feed amount in accordance with a feed movement amount of the other rest arm, and adding the correction feed amount to the second command value. Adding means for obtaining a corrected second command value by using the first and second servomotors corresponding to the one rest arm based on the first command value and the corrected second command value. And control means for controlling the other of the first and second servomotors corresponding to the rest arms of the first and second servomotors, respectively.

According to a second aspect of the present invention, in the NC control type work rest device, the one and the other rest arms are the upper and lower rest arms, respectively, and the correction feed amount setting means is provided for each movement amount of the lower rest arm. And a means for reading a correction value corresponding to the amount of movement of the lower rest arm from the correction value table, and the control means includes the first command value and the second correction value. The first and second servomotors are respectively controlled based on a command value.

According to a third aspect of the present invention, in the NC control type work rest device, the one and the other rest arms are the upper and lower rest arms, respectively, and the correction feed amount setting means is a unit of the lower rest arm. A correction value table in which each incremental correction feed amount is stored in advance in response to an increase in the amount of exercise, and each incremental correction feed amount within the exercise range in which the lower rest arm moves from the current position to the target position is read out and cumulatively added. And accumulative addition means for setting a corrected feed amount. The control means controls the first and second servo motors based on the first command value and the corrected second command value, respectively. I do.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2, reference numeral 10 denotes a rest device main body, preferably a table or a bed 1 of a grinding machine.
1 is provided fixedly. The upper rest arm 12 is guided to the apparatus main body 10 so as to be able to advance and retreat with respect to the cylindrical work W on the front side of the grindstone G rotatably supported on the grindstone table 13 and on the opposite side of the grindstone G. The lower rest arm 14 has a pin 1
The lower end of the base is pivotally connected to one end of a link 16 via a pin 17a. The pin 17a functions as a point of action for receiving a turning moment by a driving arm 18 described later. Link 16
Is pivotally connected to the front end of the drive arm 18 via a pin 17b. The driving arm 18 is guided to the apparatus main body 10 so as to be able to move forward and backward while maintaining a parallel relationship with the driving arm 18 below the upper rest arm 12.

The upper rest arm 12 and the drive arm 18 have nuts 21 and 22 fitted in holes formed at the rear ends thereof, and these nuts 21 and 22 are respectively fixed to the rear surface of the apparatus main body 10 by a servomotor. It is screwed with screw shafts 25 and 26 rotated by 23 and 24. Therefore, when the servo motors 23 and 24 are operated, the upper rest arm 12 and the drive arm 18 which are prevented from rotating with respect to the apparatus main body 10 by the key members 19 and 20, respectively, are advanced and retracted. Encoder 2 attached to
3a, 24a. In this case, the driving arm 18
Of the lower rest arm 14 via the link member 16.
Is turned.

The work W is rotatably driven while its both ends are center-supported by a headstock and tailstock (not shown) installed on a table or bed 11, and is rotated while being ground by a grindstone G. Lower rest arm 14
Are supported by the shoes 12a and 14a provided at the front end of the. The upper rest arm 12 and the lower rest arm 14 support the work W to rotate on its ideal rotation axis against normal resistance and tangential resistance generated at a grinding point which is a contact point between the work W and the grindstone G. I do.

A computer-controlled numerical controller (hereinafter, CNC device) 30 includes a CPU 31 and a memory 32.
including. When operating in the data input / output mode, the CPU 31 receives a numerical control program and various control data input by the operator interactively using the keyboard 33 and the CRT 34 through the interface 35 and inputs them into the reception memory 32. The data in the memory 32 designated by the operator is displayed on the CRT 34. When operating in the setting change mode and the grinding cycle mode, the CPU 31 executes a numerical control program,
The command value is output to the servo motor drive units DUX, DUX and DUV via the interface 36.

The drive unit DUX controls a servomotor 41 that drives a screw shaft of a feed screw mechanism 40 that moves the grindstone table 13 forward and backward with respect to the workpiece W, and drives the drive unit DUX.
And DUV control servo motors 23 and 24 for driving the upper and lower rest arms 12 and 14, respectively. Encoder 41 attached to servo motors 41, 23, 24
The feedback outputs from a, 23a, and 24a are input to the corresponding drive units DUX, DOY, and DUV, while being input to the interface 36.

Each drive unit calculates a corresponding encoder output to generate a speed feedback signal, and controls the operation speed of the corresponding servo motor so that the speed feedback signal matches the command speed signal. The interface 36 allows the CPU 31 to refer to the corresponding encoder output at predetermined intervals, thereby enabling the CPU 31 to perform position feedback control on the movement of each servomotor.

FIGS. 3 and 4 schematically show a rest control program RCP constituting a part of a system control program stored in a not-shown read-only memory (ROM) area provided in the memory 32. FIG. FIG. 3 is an explanatory view schematically showing the contents of a correction value table TBL stored in the ROM area. The correction value table TBL is, for example, every time the radius increases by 1 mm in a range from a position supporting a work with a diameter of 75 mm (reference position) to a position supporting a work with a diameter of 35 mm (most forward position). Correction amount of lower rest arm 14 corresponding to increase (corresponding to tracking error for upper rest arm 12) α1 to α
20 are registered and stored in advance at addresses N1 to N20.

The rest device according to the present invention is controlled as described below in accordance with the rest control program RCP. For example, in a mass production line for grinding a crankshaft for an automobile engine, a form in which a certain lot of work is continuously processed and then a different lot of work is continuously processed is often adopted. In this case, a setting change operation is performed prior to starting the processing operation of the work of the next lot.

When a setting change command is given in the setting change mode, steps 101 and 102 in FIG. 3 are sequentially executed, and the initial positions UPi, LPi of the upper and lower rest arms 12, 14 are set. The initial position UPi of the upper rest arm 12 is set such that the leading end of the upper rest arm 12 is retracted by a predetermined amount (for example, 20 mm) with respect to the finish diameter Dfin of the work W of the next lot to be processed (step). 101), a coefficient (for example, 0. 1) which is a predetermined electronic gear ratio is set at the initial position UPi of the upper rest arm 12.
4) multiplied by the initial position LP of the lower rest arm 14
It is set as i (step 102).

The initial positions UPi and LPi (= 0.4 UPi) set in this way are output to the drive units DUY and DUV in step 114. As a result, the tips of the upper and lower rest arms 12, 14 are next. It is positioned at a position retracted by a predetermined distance (for example, 20 mm) from the workpiece finishing diameter Dfin of the lot to be processed.

After each of the rest arms 12, 14 is retracted to the initial position, the first work W of the next lot work is performed.
Is carried into a grinding machine and is center supported on a headstock and tailstock (not shown). When the completion of loading of the work is properly confirmed by the confirmation means, the operation mode of the CNC device 30 is switched from the setting change mode to the grinding cycle mode, and a grinding cycle start command is given. The CNC device 30 operates according to the numerical control program for the work of this lot, whereby the grindstone table 13 is advanced, and at the same time, the rotation of the work W is started.

By executing the grinding cycle, the plunge grinding speed of the grindstone table 13 is increased as shown in FIG.
The work W is ground by the grindstone G while being sequentially reduced to the coarse grinding feed speed and the fine grinding feed speed, and the grinding wheel table 13 is stopped for a predetermined time after reaching the forward end position specified by the numerical control program, and sparks out. Grinding is performed, and after a lapse of a predetermined time, the grindstone table 13 is rapidly moved backward to the plunge grinding start position.

In the course of the rough grinding step in which the grinding wheel table 13 is advanced at the coarse grinding feed speed, the rest arms 12, 14 are advanced. Preferably, a coarse grinding spark-out is performed prior to the advancement of the rest arms 12, 14, and after this spark-out, the grinding wheel head 13 is retracted a little distance (back-off) to allow the advancement of the rest arms 12, 14. You. When the forward command of the rest arms 12 and 14 is given, step 111 in FIG.
Pt and forward speed UFt are set according to a numerical control program. The target position UPt of the upper rest arm 12
Preferably corresponds to 1/2 of the finished diameter Dfin of the work W. In the following step 112, the target position LPt and the forward speed LFt of the lower rest arm 14 are calculated. More specifically, target position LP of lower rest arm 14
t and the forward speed LFt are calculated by multiplying the target position UPt and the forward speed UFt of the upper rest arm 12 by a coefficient (= 0.4) which is an electronic gear ratio.

In the following step 113, a correction feed amount setting program COMP shown in FIG. 4 is executed, and the position correction amount of the lower rest arm 14 is determined according to this program. More specifically, steps 102 and 112
Position LP of the lower rest arm 14 calculated at
i, reading of target position LPt, correction value table TBL
Counter A that specifies the initial read address of
Setting of the initial value Ni of C and zeroing of the correction amount register $ α, and further, the lower rest arm 14 is moved to the initial position LPi.
Is calculated in steps 201 to 203 respectively.

The initial value Ni set in the address counter AC in step 202 is set corresponding to the initial position LPi of the lower rest arm 14. Step 2
In the calculation of the moving distance of the lower rest arm 14 in 03, the target position LPt is subtracted from the initial position LPi of the lower rest arm 14, thereby obtaining the radius difference as an integer value n. This integer value n corresponds to the correction value table TB shown in FIG.
Indicates the number of steps of the read address of L.

Steps 204 to 208 correspond to step 20
2. The initial read address Ni of the correction value table TBL set in Step 2 is incremented by the number of times corresponding to the integer value n, and the correction amount α read for each step is sequentially and cumulatively added to the correction amount register Σα. Then, in step 209, the correction amount of the correction amount register $ α is stored in step 11
The correction target position LPt ′ of the lower rest arm 14 is obtained by adding the target position LPt of the lower rest arm 14 calculated in step 2.

Accordingly, in step 114 of FIG. 3, the target position UPt and the command speed UFt of the upper rest arm 12 are output to the drive unit DUY, and the corrected target position LPt 'and the speed command L of the lower rest arm 14 are output.
Ft is output to the drive unit DUV. For this reason, the forward movement of the tip of the upper rest arm 12 causes the lower rest arm 14 to move forward.
The forward movement of the tip of the arm follows exactly, and these rest arms 1
During the forward movement, the workpieces 2 and 14 abut against the outer periphery of the workpiece W being processed and support it against the grinding resistance. When the rest arms 12, 14 have reached the target position UPt and the correction target position LPt ', the tip of the upper rest arm 12 and the tip of the lower rest arm 14, when the workpiece W is machined to the finishing diameter Dfin. The finished outer circumference of the work W is held so that the axis of the work W is positioned at the ideal rotation center.

FIG. 7A shows a tracking error of the lower rest arm 14 with respect to a movement amount (displayed as a workpiece diameter) of the tip of the upper rest arm 12 when the same command value is given to the servo motors 23 and 24. . FIG. 7 (B) shows that the command value of the upper rest arm 12 is multiplied by a predetermined coefficient,
5 shows a tracking error of the distal end of the lower rest arm 14 with respect to the movement amount of the distal end of the upper rest arm 12 when the command value is.
As described above, when the target position LPt of the lower rest arm 14 is a value obtained by multiplying the target position UPt of the upper rest arm 12 by the electronic gear ratio and decelerating, the tracking error of the lower rest arm 14 with respect to the upper rest arm 12 is large. Is reduced to However, a tracking error still remains between the two rest arms 12, 14 at the center of the range of use of the rest device.

FIG. 7 (C) shows that the target position LPt of the lower rest arm 14 decelerated by the electronic gear ratio is error-corrected in accordance with the present invention as described above, and this corrected target position LPt '.
Shows the tracking error of the distal end of the lower rest arm 14 with respect to the distal end position of the upper rest arm 12 in the case where is given to the servo motor 24 of the lower rest arm 14. This FIG.
As is clear from (C), when error correction is performed according to the present invention, it is possible to eliminate the following error at the tips of both the rest arms 12 and 14.

As described above with reference to FIG. 6, the rest arms 12, 14 are advanced in the course of the grinding, and support the work W at the advanced position until the work W is machined to the finish diameter Dfin. In this forward position, the contact points of the tip shoes 12a, 14a of the both rest arms 12, 14 with the work W are equidistant from the ideal rotation axis of the work W,
For this reason, at the time of final spark-out grinding immediately before the grinding wheel head 13 retreats, the work W is in a state of rotating on the ideal rotation axis, and the grinding wheel head 13 retreats in this state. And
The rotation of the work W is stopped slightly after the retreat of the grindstone table 13, and the two rest arms 12, 14 are retracted to the initial positions UPi, LPi set in steps 101 and 102 in FIG. The processing of the work W ends.

When processing the second work W of the same lot, the above-described setting change operation is not performed. When the second work W is loaded and set on the grinding machine, the above-described grinding cycle is performed. It starts immediately. In the above-described embodiment, the correction amounts α0 to α20 each time the lower rest arm 14 advances by a unit distance (for example, 1 mm) are registered in the correction value table TBL illustrated in FIG. The correction amount αn is sequentially read out from the correction value table TBL and is cumulatively added. The registration form of the correction amount in the correction value table TBL is as follows.
When one of a large number of correction values registered in the correction value table TBL is corrected, there is no effect on other correction values. The advantage of this point is that an interpolation correction value between two correction values is obtained and fine correction is determined. And the effect of reducing the number of registered correction values.

However, the registration form of the correction amount in the correction value table TBL is not limited to this. For example, in each grinding cycle, the rest arms 12,
In the case of adopting a control mode in which the reference position 14 is advanced from the most retracted reference position to the target position, the correction amount registered at each read address of the correction value table TBL is:
It is also possible to register as a total correction amount according to the movement amount from the reference position to the target position. In such a modification, the correction feed amount setting program C shown in FIG.
The OMP is changed so that the total correction amount registered at the address corresponding to the workpiece finish diameter Dfin is read, and the total correction amount is added to the target position LPt of the lower rest arm 14 decelerated by the electronic gear ratio.

When the correction amount registered in the correction value table TBL can be calculated by a function formula relating to the moving position (or moving amount) of the rest arm 12 or 14, instead of using the correction value table TBL, By registering this function formula, it is also possible to directly calculate the correction amount from this function formula. In the above-described embodiment, the target position LPt of the lower rest arm 14 is calculated by multiplying the target position UPt of the upper rest arm 12 by the electronic gear ratio. It can also be specified directly as a parameter in the program.

Further, in the above-described embodiment, the target position UPt of the arm 12 is determined with reference to the upper rest arm 12.
Is multiplied by the electronic gear ratio in the deceleration direction to calculate the target position LPt of the lower rest arm 14. Conversely, the target position LPt is set based on the lower rest arm 14 and corresponds to the workpiece finishing diameter of the arm 14. The target position UPt of the upper rest arm 12 may be calculated by multiplying the set target position LPt by a predetermined speed increasing electronic gear ratio coefficient (for example, 2.5). In such a case, a tracking error of the tip of the upper rest arm 12 with respect to the movement of the tip of the lower rest arm 14 is registered in the correction value table TBL of FIG.

Further, in the present embodiment, both the rest arms 1
2, 14 target position UPt and corrected target position LPt '
Are set to coincide with the finish diameter position of the workpiece W. If necessary, these positions UPt and LP
t 'may be set to a position on the smaller diameter side by a predetermined amount (for example, several micrometers) from the work finish diameter position.

[0034]

As described in detail above, according to the first aspect of the present invention, the movement of the upper rest arm that moves linearly toward the cylindrical work is caused by pivoting the lower rest arm to move the tip of the lower rest arm. In the NC control type work rest device adapted to follow, a target position for instructing a servo motor for driving one of the upper rest arm and the lower rest arm is set according to the finishing diameter of the work, and the other of the two rest arms is set. The target position to be commanded to the servomotor to be driven is obtained by multiplying the target position of the one rest arm by a predetermined ratio or determined according to the finished diameter of the work, and the target position is set to the amount of movement of the other rest arm. Is set as a correction target position obtained by adding a correction amount corresponding to the movement of the tip of the one rest arm to the movement of the tip of the other rest arm accurately. It is to be able, thereby improving the machining accuracy of the workpiece.

According to the second aspect of the present invention, in order to obtain the correction amount of the lower rest arm, which is the other rest arm, the correction amount for each movement amount of the lower rest arm is stored in a correction value table in advance, Since the correction amount corresponding to the amount of exercise of the lower rest arm is read from this correction value table to correct the target position of the lower rest arm, it is possible to easily set or change the correction value.

Further, according to the third aspect of the present invention, in order to obtain the correction amount of the lower rest arm which is the other rest arm, each of the increment correction values corresponding to the increase in the unit movement amount of the lower rest arm is corrected. It is stored in advance in a table, and each incremental correction amount within the movement range in which the lower rest arm moves from its current position to its target position is read from the correction value table and cumulatively added to correct the target position of the lower rest arm. Therefore, when one of the many correction values registered in the correction value table TBL is corrected, there is no effect on other correction values, and
The advantage of this point is that the number of correction values to be registered can be reduced in a case where an interpolation correction value between two correction values is determined and a fine correction is performed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining that a support point of a work at the tip of a lower rest arm changes according to a change in a work diameter;

FIG. 2 is a side view showing a partially cutaway NC control type work rest device according to the present invention and a block diagram of a CNC device for controlling the work rest device.

FIG. 3 is a flowchart of a rest control program executed by the CNC device according to the present invention.

FIG. 4 is a flowchart of a correction feed amount setting program executed by the CNC device in step 113 of the rest control program.

FIG. 5 is an explanatory diagram showing an outline of a correction value table registered in a memory of the CNC device.

FIG. 6 is an operation cycle diagram showing feed positions of a grindstone and a work rest device in a grinding cycle.

7 (A) and 7 (B) are graphs showing a tracking error of a lower rest arm tip with respect to an upper rest arm tip position in a conventional NC control type work rest device, and FIG. 7 (C) is an NC control type work rest according to the present invention. 9 is a graph showing a tracking error of the lower rest arm tip with respect to the upper rest arm tip position in the device.

[Explanation of symbols]

W: Work 10: Rest device body 12: Upper rest arm 14: Lower rest arm 23, 24 ... Servo motor 25, 26 ... Feed screw mechanism 30 CNC device DUX, DUI, DUV Servo motor drive unit RCP Rest control program COMP Compensation feed amount setting program TBL Compensation value table

Claims (3)

[Claims] 1. An apparatus main body, an upper rest arm guided by the apparatus main body so as to be able to advance and retreat toward the work so as to support an outer periphery of a cylindrical work on a side opposite to a processing tool, and a tip of the upper rest arm is substantially equivalent to the work. A lower rest arm pivotally supported by the apparatus main body so as to advance and retreat from below toward the work, a feed mechanism including a first servomotor for moving the upper rest arm forward and backward, and pivoting the lower rest arm Second
In an NC control type workrest device including a feed mechanism including a servomotor and a numerical control device for controlling the first and second servomotors, the numerical control device is configured to perform a control according to a finishing diameter of the work. First command value setting means for setting a first command value for controlling a feed motion of one of the upper rest arm and the lower rest arm determined in advance,
A second command value, which is obtained by multiplying the first command value by a predetermined coefficient or is determined according to the finishing diameter of the work, and controls the other feed motion of the upper and lower rest arms is set. Second command value setting means, correction feed amount setting means for setting a correction feed amount according to the feed movement amount of the other rest arm, and a correction second command by adding the correction feed amount to the second command value. Adding means for obtaining a value, further corresponding to one of the first and second servomotors corresponding to the one rest arm and the other rest arm based on the first command value and the corrected second command value. Control means for controlling the other of the first and second servomotors, respectively. 2. The method according to claim 1, wherein the one and other rest arms are the upper and lower rest arms, respectively, wherein the correction feed amount setting means includes a correction value table for storing a correction value for each movement amount of the lower rest arm; Means for reading a correction value corresponding to the amount of movement of the lower rest arm from the correction value table, and the control means controls the first and second servos based on the first command value and the corrected second command value. The NC control type work rest device according to claim 1, wherein each of the motors is controlled. 3. The one and other rest arms are the upper and lower rest arms, respectively, and the correction feed amount setting means sets each incremental correction feed amount in response to an increase in the unit movement amount of the lower rest arm. A correction value table stored in advance, and a cumulative addition means for reading out and cumulatively adding each incremental correction feed amount within a movement range in which the lower rest arm moves from a current position to a target position to set the correction feed amount. The NC control type work rest device according to claim 1, wherein the control means controls the first and second servo motors based on the first command value and the corrected second command value, respectively. .