JP2013206342A - Control device for machine tool and machining method for work by rotary tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of a machine tool for reducing a quadrant projection and a machining method of a work by a rotary tool.SOLUTION: A control device 10 of a machine tool 5 for cutting a work by relatively moving a rotary tool for performing intermittent cutting and the work includes: target position specification means 12 for preliminarily specifying a target position on a tool path in which a motion error is generated; and phase control means 14 for controlling the phase of the rotary tool during the machining of the work such that any machining trace can be prevented from remaining on a work machining surface by the cutting edge of the rotary tool at the specified target position.

Description

  The present invention relates to a machine tool control device that cuts a workpiece by relative movement between a rotary tool that performs intermittent cutting and the workpiece, and a workpiece machining method using the rotary tool.

  Machine tools may cause motion errors in the feed shaft due to drive system time delays caused by various causes. Examples of causes of motion errors include those due to fluctuations in cutting load and quadrant protrusions that occur when quadrants are switched such as circular interpolation motion. Variations in the cutting load occur when the cutting edge of the rotary tool begins to bite the workpiece, or when the cutting changes. FIG. 7 shows a case where a region 101 having a step is cut by a rotary tool 100 that performs intermittent cutting, such as an end mill, as an example of the processing form. At the moment of cutting the region 101, the rotary tool 100 is bent with a base end as a fulcrum by receiving a cutting resistance, thereby causing a shift in the movement trajectory of the tool and causing a motion error. FIG. 8 and FIG. 9 show an example of a machining mode in which quadrant protrusions are generated when the rotary tool 100 cuts the workpiece upper surface 104 and the inner corner 103 of the workpiece inner peripheral surface. In general, in the processing of the workpiece upper surface 104 in FIG. 8, an assembly of quadrant projections that are undesirable processing marks in the form of protrusions is formed as a streak 105 at the apex of the workpiece upper surface 104, and in the corner processing in FIG. Undesirable machining traces that are partially concave are formed on the work inner peripheral surface of the quadrant switching part that changes to a part.

  As described above, the movement error of a machine tool causes a shift in the movement trajectory of the rotary tool due to various causes, and forms a protruding machining trace on the workpiece outer circumferential surface, or on the workpiece inner circumferential machining surface. In some cases, a concave mark and a processing mark may be formed. In particular, undesired protrusions and recesses such as FIG. 8 and FIG. 9 are known as quadrant protrusions, which occur in the vicinity where the feed direction of the feed shaft switches from plus to minus or minus to plus, for example, When the servo motor receives an arc command, this is a machining error that occurs due to a shift in the operation timing of the feed shaft when the feed direction of the feed shaft is reversed (or a motion error is transferred to the workpiece surface). . Such machining errors can be reduced by appropriately adjusting the NC parameters of the machine tool. However, in order to set the NC parameter that affects the machining error to the optimum value, it is necessary to repeat the test machining with the actual machine and measure the shape, and adjusting the NC parameter by trial and error There is a problem that it is very time consuming and requires work.

  Patent Document 1 discloses a curved surface machining method and a machining apparatus that have a technical problem of preventing corrugated streaks from being formed on a workpiece machining surface at regular intervals corresponding to the feed rate of a rotary tool. In paragraph 0006, the workpiece is changed while changing at least one of the three machining conditions, ie, the rotational speed of the rotary tool, the relative feed direction between the rotary tool and the workpiece, and the relative feed speed between the rotary tool and the workpiece during machining. Is described.

  Patent Document 2 discloses a quadrant in which machining traces caused by lost motion or the like are not formed on a machining surface, that is, a motion error of a drive mechanism of a machine tool or a motion error caused by a servo delay appears on a workpiece outer peripheral surface. Disclosed is a method for cutting a work material, in which a projection is eliminated and a processed surface is finished with high accuracy. Paragraph 0029 describes that the direction and the magnitude of the feed rate vector of the cutting point, which is the contact point between the workpiece and the end mill tool, are made unchanged while the workpiece outer periphery is scanned once with the end mill tool. Also, in order to make the direction and magnitude of the feed rate vector at the cutting point unchanged, the end mill tool translates in the X, Y and Z axes, and rotates in the B and C axis directions of the table. It describes that the movement and the synchronous control are performed.

JP 2000-61777 A JP 2011-22898 A

  The machining method disclosed in Patent Document 1 removes the wavy traces formed on the workpiece machining surface at regular intervals corresponding to the feed speed by cyclically changing the rotation speed and the feed speed. However, it does not prevent machining traces caused by stick motion or lost motion from being formed on the workpiece machining surface. That is, Patent Document 1 does not disclose a method of eliminating quadrant projections as undesirable machining traces formed on the workpiece machining surface by circular machining of the workpiece outer periphery with a rotary tool.

  In the invention described in Patent Document 2, the quadrant projections caused by the lost motion or the like are prevented from being switched during the machining by the synchronous control of the translational movement and the rotational movement of the feed drive mechanism, and the quadrant projection caused by the lost motion or the like However, the direction in which the formation of quadrant protrusions can be excluded is limited to the direction in which the direction of the feed velocity vector at the cutting point coincides with the direction causing the motion error, and the cutting point It is impossible to eliminate quadrant protrusions that occur in a direction orthogonal to the direction of the feed speed vector. In this regard, paragraph 0048 of Patent Document 2 describes that quadrant protrusions are formed on the X-axis minus side and the X-axis plus side. In addition, it is necessary to newly add a configuration for rotating the workpiece on the table of the machine tool, and there is a problem that the machine tool becomes complicated.

  The present invention has been made in order to solve the above-described problems, and during machining of a workpiece by a rotary tool that performs intermittent cutting, the cutting edge is placed on the workpiece machining surface at a target position specified on the tool movement path. It is an object of the present invention to provide a machine tool control device that does not leave undesirable machining traces and a workpiece machining method using a rotary tool.

  In order to achieve the above object, according to the present invention, in a control device for a machine tool that cuts a workpiece by relatively moving a rotary tool that performs intermittent cutting and the workpiece, a target position on a tool path that causes a motion error is determined. Target position specifying means for specifying in advance, and phase control means for controlling the phase of the rotary tool during processing of the workpiece so that the cutting edge of the rotary tool does not leave a processing mark on the workpiece processing surface at the specified target position. A machine tool control device is provided.

  In the control device of the machine tool, the phase control unit is configured to perform non-cutting among intermittent cutting in which the cutting edge of the rotary tool at the specified target position is alternately repeated when cutting the workpiece and when not cutting. The phase of the rotary tool is controlled so that it exists at the rotation angle position.

  In the machine tool control device, the phase control means predicts the phase of the rotating tool at the target position specified by the target position specifying means, and the cutting edge of the rotary tool by the tool phase prediction section. Includes a tool phase / feed speed correction unit that changes the phase of the rotary tool or the feed speed of the relative movement when it is predicted to exist at the rotation angle position at which the workpiece is cut at the specified target position.

  According to the present invention, in the workpiece machining method in which the rotary tool for performing intermittent cutting and the workpiece are moved relative to each other to cut the workpiece, a target position on the tool path that causes a motion error is specified in advance, Machining the workpiece with the rotary tool, the step of controlling the phase of the rotary tool during machining of the workpiece so that the cutting edge of the rotary tool does not leave a machining trace on the workpiece machining surface at the target position A method is provided.

  As described above, according to the present invention, it is possible to eliminate an undesirable machining trace generated on a workpiece machining surface by using an existing machine tool without newly adding a configuration for rotating a workpiece on a table to the machine tool. Therefore, it is possible to obtain a workpiece machining surface with high accuracy.

It is a block diagram which shows the functional structure of the control apparatus of the machine tool of this invention. It is a block diagram which shows one Embodiment of the control apparatus of the machine tool of this invention. It is a flowchart which shows one Embodiment of the processing method of the workpiece | work with a rotary tool. It is a flowchart which shows other embodiment of the processing method of the workpiece | work by a rotary tool. It is explanatory drawing at the time of carrying out circular arc processing of the hole inner periphery of a workpiece | work by the conventional method which cannot control the phase of a rotary tool, (a) is the movement path | route of a rotary tool, and the phase of the rotary tool in specific target position AD. (B) is a figure which shows the distance from a workpiece processing surface to a cutting edge when a rotary tool makes 1 round of work inner periphery. It is explanatory drawing at the time of carrying out circular arc machining of the hole inner periphery of a workpiece | work by the method of this invention, (a) is a figure which shows the movement path | route of a rotary tool, and the phase of the rotary tool in specific target position AD. ) Is a diagram showing the distance from the workpiece machining surface to the cutting edge when the rotary tool makes one round of the workpiece inner circumference. It is explanatory drawing which shows an example of the processing form when cutting load changes in the process using a rotary tool. It is explanatory drawing which shows the process of the workpiece | work upper surface using a rotary tool as an example of the process form when a quadrant switches. It is explanatory drawing which shows the cutting of the corner part (in-corner part) of the work inner periphery using a rotary tool as another example of the processing form when a quadrant switches.

The machine tool control device of the present invention will be described in detail below.
In FIG. 1, a functional configuration of the control device 10 of the present invention is shown in a block diagram. Since the basic configuration of the machine tool 5 is a general one, illustration is omitted, but for example, a horizontal machining center having three orthogonal linear feed axes (X axis, Y axis, Z axis) is targeted. be able to. In a general configuration, a machining center includes a table that holds a workpiece, a spindle head that is supported by a column so as to be movable in the vertical direction, and a spindle that is rotatably held by the spindle head. It is possible to relatively move in three axial directions orthogonal to each other.

  The control device 10 of the present invention has a spindle rotation axis control (Cs axis control) function, a servo control unit (not shown) for positioning the spindle phase by servo control, and linear interpolation of feeds at each linear feed axis. And an interpolation unit (not shown) for calculating an interpolation pulse based on a movement command for circular interpolation.

Furthermore, in addition to the above-described configuration, the control device 10 of the present invention includes target position specifying means 12 for specifying in advance a target position that is a control target position on a tool movement path that is a movement locus of the tool center during machining, and a specification. Phase control means for controlling the phase of the rotary tool during machining so that the cutting edge of the rotary tool does not leave a machining trace on the workpiece machining surface at the target position.
The target position specified on the tool movement path is theoretically the tool center position when the cutting edge of the rotary tool begins to bite the work, and the tool center of the quadrant switching part when machining the inner corner of the work The position of the tool and the center position when machining the area where the incision changes such as the stepped part, the part where the feed direction (quadrant) of the linear feed axis switches from plus to minus or minus to plus due to the circular movement of the rotary tool This is the center position of the tool when machining. Perform test machining under various machining conditions, create a database of the deviation between the theoretical target position and the position where the actual machining trace occurs, and perform simulation based on the database when executing the actual machining program. The position should be determined.
For example, when the CAD 16 or CAM 17 system is used, the tool movement path is a machining program based on tool shape data, workpiece shape data, and machining condition data input to the system from the storage device 28 or an external input device (not shown). Generated. Tool shape data, workpiece shape data, and machining condition data can also be input to the system via a network. Also, position data such as the current position (X axis, Y axis, Z axis, Cs axis) of the rotary tool or workpiece is directly input to the control device 1 from the NC device that controls the machine tool 5.

  As described above, the target position specifying unit 12 specifies the target position specified on the tool movement path by calculation or simulation. At the specified position, the movement trajectory of the rotary tool is displaced due to the motion error of the machine tool 5, so when the inner peripheral surface such as the inner corner of the workpiece is being cut, that position, that is, the position where the quadrant is switched. If the cutting edge of the rotary tool bites excessively into the workpiece processing surface to form a dent, on the other hand, if the outer peripheral surface of the workpiece is being cut, the part is at that position. Therefore, a shallow cut is formed, and quadrant protrusions are formed on the workpiece machining surface. Hereinafter, the “machining trace” referred to in the present specification includes both a dent partially formed on the workpiece machining surface and a projection-like quadrant projection.

  FIG. 2 shows a functional configuration of an embodiment of the control device as a specific example in the case where the quadrant protrusion formed on the workpiece processing surface is excluded or suppressed. The control device 20 includes a reading unit 21 for reading command values of the current positions of the X axis, the Y axis, the Z axis, and the Cs axis, the spindle rotational speed N, and the feed speed F, and the target position specifying unit 12 shown in FIG. The quadrant protrusion generation position prediction calculation unit 22 and a phase control means 14 to be described later are provided. As shown in FIG. 2, the phase control unit 14 includes a tool phase prediction unit 24 and a tool phase / feed speed correction unit 26 that corrects the contents of a machining program created in advance. The tool phase prediction unit 24 obtains the orientation of the workpiece machining surface with respect to the rotary tool at each target position specified by the quadrant projection generation position prediction calculation unit 22, and the cutting edge of the rotary tool is a workpiece at each target position. The phase of the machining surface is predicted by calculation. As a result, at each target position, the cutting edge position can be expressed by the rotation angle and the distance from the work surface (see FIGS. 5 and 6), and the cutting edge comes into contact with the work surface (cutting). State).

  The tool phase / feed speed correcting unit 26 is configured so that the cutting edge of the rotary tool is detached from the workpiece when the tool phase prediction unit 24 predicts that the cutting edge contacts the workpiece machining surface at the specified target position. The phase of the rotary tool is changed by Cs axis control (so that the interrupted cutting state, that is, the cutting edge is in the non-cutting position).

  Here, the spindle rotation axis controlled by the Cs axis is a control axis additionally provided to the spindle in order to determine the phase of the spindle by servo control, and the cutting edge with respect to the workpiece machining surface by the Cs axis control. The phase of the main shaft (rotating tool) can be changed so that is detached. When the rotational speed of the Cs axis is constant, the feed phase can be changed to correct the tool phase at the quadrant projection generation predicted position. Therefore, the tool phase / feed rate correction unit 26 can selectively correct one of the phase of the rotary tool or the feed rate of the rotary tool so as not to leave a machining trace on the workpiece machining surface.

  Thereby, even if the machine tool 5 has a movement error and the shift of the moving path of the rotary tool occurs, the cutting edge is detached from the workpiece processing surface at the position where the shift of the moving path occurs. The formation of machining traces on the workpiece machining surface can be eliminated or suppressed.

  3 and 4 are flowcharts for explaining the workpiece machining method of the present invention. FIG. 3 shows an example in which a sudden change position of the cutting load is specified (acquired) as a target position on the tool movement path where the machine tool 5 causes a movement error. FIG. Another example in which the generation position of the quadrant projection is specified as the target position on the tool movement path to be generated will be shown.

  Referring to the flowchart of FIG. 3, in step S10, machining is started based on a machining program created by the CAD16 and CAM17 systems, and in step S20, a sudden change position of a cutting load existing on the tool movement path is calculated in advance. In step S30, the direction of the workpiece machining surface relative to the rotary tool is specified at the specified sudden change position of each cutting load. In step S40, the cutting edge of the rotary tool is moved to the workpiece at the sudden change position of each cutting load. The phase of the rotary tool held by the spindle is controlled by Cs axis control or feed axis control so as not to leave unnecessary machining traces on the machining surface, and the cutting edge is in the non-cutting range at the sudden change position of the specified cutting load. In step S50, the processing is terminated. In this case, it is preferable to determine the phase from the starting point of the movement path TP of the tool CT. By doing so, the feed amount per tooth does not change during the movement of the tool CT, and the machined surface quality is improved. Since FIG. 4 is the same as FIG. 3 except that the generation position of the quadrant protrusion is specified as the target position on the tool movement path, the description thereof is omitted.

  FIGS. 5 and 6 show that the rotary tool having a single cutting edge is included in the workpiece in the conventional case where the phase of the rotary tool for performing intermittent cutting cannot be controlled and in the case of the present invention where the phase of the rotary tool can be controlled. The figure shows the phase of the rotary tool and the amount of cutting edge detachment from the workpiece machining surface at the specific target position when the inner diameter machining of the workpiece is carried out by rotating counterclockwise along the circumference.

  FIG. 5A shows the phase of the rotary tool CT at specific target positions A to D in the conventional case where the phase of the rotary tool CT cannot be controlled. The single-blade rotary tool CT moves in the counterclockwise direction on the movement path TP along the inner periphery of the workpiece W. At the specific target positions A to D at which the quadrants are switched, due to a motion error of the machine tool 5, a protrusion-like deviation occurs in the movement path TP of the tool CT. That is, the rotary tool CT is maintained at a certain distance from the workpiece machining surface except for the specific target positions A to D, but approaches the workpiece machining surface at the specific target positions A to D. It becomes. At the specific target positions A, B, and D, there is no problem because the cutting edge CE is in a non-cutting state, that is, separated from the work surface, but at the specific target position C, the cutting edge CE is on the work surface. Contact (biting) will leave an undesirable concave processing mark.

  FIG. 5B shows the distance from the workpiece machining surface to the cutting edge CE. When machining is started, one cutting edge CE repeats contact and separation periodically with respect to the workpiece machining surface as the rotary tool CT itself rotates, and at the specific target positions A, B and D, the cutting edge Although the distance of CE from the workpiece machining surface increases, at the specific target position C point, it is shown that the cutting edge CE contacts the workpiece machining surface and cuts into the machining surface.

  FIG. 6A shows the phase of the rotary tool CT at specific target positions A to D in the case of the present invention in which the phase of the rotary tool CT is controlled. The movement path TP of the rotary tool CT is the same as in the conventional case. However, at the specific target position C, the phase of the rotary tool CT is controlled by the Cs axis and the cutting edge CE is detached from the workpiece machining surface. It is different from the example.

  FIG. 6B shows the distance from the workpiece machining surface to the cutting edge CE. In the case of the present embodiment, the Cs axis control is performed after the specific target position B point, and at the specific target position C point, control is performed so that the cutting edge CE is positioned, for example, 180 ° opposite to the workpiece machining surface. ing. Although the specific target position D point is not shown, one piece of cutting edge CE is controlled so as to be separated from the workpiece machining surface. Thereafter, the rotary tool CT is continuously moved along the inner periphery of the workpiece under this machining condition, and it is determined whether or not the cutting edge CE is in contact with the workpiece machining surface at the specific target position D, and does not come into contact. In this case, the machining is performed as it is, and in the case of contact, the cutting edge CE is controlled by Cs axis control so as not to contact the workpiece machining surface.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, it can deform | transform and implement variously. 5 and 6 show the rotary tool CT having a single cutting edge CE. Even when a multi-blade rotary tool having a plurality of cutting edges is used, the Cs axis control is used. It is possible to control the individual cutting blades so as not to contact the workpiece processing surface. In addition, it is not limited to the inner diameter machining of the workpiece W. Even when machining the inner corner portion of the workpiece, the outer diameter machining of the workpiece, the machining along the contour line, or the region where the cutting amount changes, It is possible to sequentially control the phase of the rotary tool during machining so that the cutting edge does not leave a machining mark on the workpiece machining surface.

  As described above, according to the machine tool control device and the workpiece machining method of the present embodiment, during the machining of the workpiece W by the rotary tool CT that performs intermittent cutting, the cutting at the target position specified on the tool movement path TP is performed. By controlling the phase (rotational position) of the blade CE, the cutting edge CE can be prevented from leaving undesired machining traces on the workpiece machining surface, and the workpiece W can be processed with high quality and high accuracy. .

10, 20 Control device 12 Target position specifying means 14 Tool phase control means 22 Quadrant projection generation position prediction calculation section 24 Tool phase prediction section 26 Tool phase / feed speed correction section W Work CT Rotating tool CE Cutting edge TP Tool movement path A , B, C, D Target position specified

As described above, the movement error of a machine tool causes a shift in the movement trajectory of the rotary tool due to various causes, and forms a protruding machining trace on the workpiece outer circumferential surface, or on the workpiece inner circumferential machining surface. there or to form a concave working mark. In particular, undesired protrusions and recesses such as FIG. 8 and FIG. 9 are known as quadrant protrusions, which occur in the vicinity where the feed direction of the feed shaft switches from plus to minus or minus to plus, for example, When the servo motor receives an arc command, this is a machining error that occurs due to a shift in the operation timing of the feed shaft when the feed direction of the feed shaft is reversed (or a motion error is transferred to the workpiece surface). . Such machining errors can be reduced by appropriately adjusting the NC parameters of the machine tool. However, in order to set the NC parameter that affects the machining error to the optimum value, it is necessary to repeat the test machining with the actual machine and measure the shape, and adjusting the NC parameter by trial and error There is a problem that it is very time consuming and requires work.

In order to achieve the above object, according to the present invention, in a control device for a machine tool that cuts a workpiece by relatively moving a rotary tool that performs intermittent cutting and the workpiece, a target position on a tool path that causes a motion error is determined. The target position specifying means to be specified in advance and the cutting edge of the rotary tool at the specified target position are present at non-cutting rotational angle positions among the intermittent cuttings in which the cutting of the workpiece and the non-cutting are alternately repeated. Thus, there is provided a machine tool control device comprising phase control means for controlling the phase of the rotary tool.

According to the present invention, in the workpiece machining method in which the rotary tool for performing intermittent cutting and the workpiece are moved relative to each other to cut the workpiece, a target position on the tool path that causes a motion error is specified in advance, Controlling the phase of the rotary tool so that the cutting edge of the rotary tool at the target position is located at a non-cutting rotational angle position among the intermittent cuttings in which the cutting of the workpiece and the non-cutting are repeated alternately And a workpiece machining method using a rotary tool.

Control device 10 of the present invention, the spindle rotation axis control (Cs axis control) has the function, lines earthenware pots servo controller in a servo control positioning of the spindle phase (not shown), linear interpolation feed at each linear feed axis And an interpolation unit (not shown) for calculating an interpolation pulse based on a movement command for circular interpolation.

Furthermore, in addition to the above-described configuration, the control device 10 of the present invention includes target position specifying means 12 for specifying in advance a target position that is a control target position on a tool movement path that is a movement locus of the tool center during machining, and a specification. Phase control means for controlling the phase of the rotary tool during machining so that the cutting edge of the rotary tool does not leave a machining trace on the workpiece machining surface at the target position.
The target position specified on the tool movement path is theoretically the tool center position when the cutting edge of the rotary tool begins to bite the work, and the tool center of the quadrant switching part when machining the inner corner of the work The position of the tool and the center position when machining the area where the incision changes such as the stepped part, the part where the feed direction (quadrant) of the linear feed axis switches from plus to minus or minus to plus due to the circular movement of the rotary tool This is the center position of the tool when machining. Perform test machining under various machining conditions, create a database of the deviation between the theoretical target position and the position where the actual machining trace occurs, and perform simulation based on the database when executing the actual machining program. The position should be determined.
For example, when the CAD 16 or CAM 17 system is used, the tool movement path is a machining program based on tool shape data, workpiece shape data, and machining condition data input to the system from the storage device 28 or an external input device (not shown). Generated. Tool shape data, workpiece shape data, and machining condition data can also be input to the system via a network. In addition, the current position of the rotary tool and work (X axis, Y axis, Z axis, Cs-axis) position data, such as is directly input to the controller 1 0 NC apparatus for controlling a machine tool 5.

Claims (4)

In a machine tool control device that cuts a workpiece by relatively moving the rotary tool that performs intermittent cutting and the workpiece,
Target position specifying means for specifying in advance a target position on a tool path that causes a movement error;
Phase control means for controlling the phase of the rotary tool during machining of the workpiece so that the cutting edge of the rotary tool does not leave a machining trace on the workpiece machining surface at the specified target position;
A machine tool control device comprising:   The phase control means is configured to be present at a non-cutting rotational angle position among intermittent cuttings in which the cutting edge of the rotary tool at the specified target position is alternately repeated when cutting the workpiece and when not cutting. The machine tool control device according to claim 1, which controls a phase of the rotary tool.   The phase control means predicts the phase of the rotary tool at the target position specified by the target position specifying means, and the cutting edge of the rotary tool at the target position specified by the tool phase prediction section. 3. The machine tool control according to claim 2, further comprising: a tool phase / feed speed correcting unit that changes a phase of the rotary tool or a feed speed of the relative movement when it is predicted to exist at a rotation angle position at which the workpiece is cut. apparatus. In a workpiece machining method in which a rotary tool that performs intermittent cutting and a workpiece are moved relative to each other to cut the workpiece,
Preliminarily specifying a target position on the tool path that causes a movement error;
Controlling the phase of the rotary tool during machining of the workpiece so that the cutting edge of the rotary tool does not leave a machining trace on the workpiece machining surface at the specified target position;
A method for machining a workpiece with a rotary tool, characterized by comprising:

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