JP4128929B2 - Machining method for confirming displacement amount of machine tool and workpiece for confirming displacement amount - Google Patents

Description

  The present invention relates to a machining method for obtaining a displacement of a machine tool during machining in a machine tool such as a milling machine, a machining center, or a combined machining lathe, and more particularly, machining for easily confirming a displacement amount of a machine tool during machining. The present invention relates to a method and a displacement amount confirmation workpiece obtained by this processing method.

When machining with a rotating tool such as a milling machine or end mill on a machine tool such as a milling machine, machining center, or combined machining lathe, heat generated when the rotating tool cuts a workpiece, motors and feed screws that operate each part of the machine tool, etc. Each part of the machine tool undergoes thermal deformation due to heat generated in the drive system or changes in temperature. Since such thermal displacement changes the relative position between the tool and the workpiece, if thermal displacement occurs in the machine tool during machining, the workpiece machining accuracy deteriorates.
On the other hand, the positional relationship between the tool and the workpiece in a state where the machine temperature is controlled by cooling each part of the machine tool, in a room where the temperature is controlled, or in the state where the heat is displaced in advance by sufficient warm-up operation. Or predicting the thermal displacement from the experiment and correcting the operation command value of the machine tool.
Of these, the machine tool and the method of controlling the temperature require complicated and expensive equipment, and also requires installation space. In the method of performing warm-up, there is a problem that thermal displacement occurs after sufficient warm-up, and in recent years, research on techniques for predicting and correcting thermal displacement from experimental results has been actively conducted. Has been put to practical use.
In such a case, in order to predict the thermal displacement from the actual measurement or the experimental result, it is necessary to accurately evaluate the thermal displacement at the stage of the experiment or the like.

In order to measure the amount of thermal displacement, for example, the following three methods are known.
First, as shown in FIG. 6, a test bar 10 is attached to the main shaft, a dial gauge is applied to the test bar from the table, and the measurement is performed over time. A non-contact sensor may be used instead of the dial gauge. In FIG. 6, arrows A, B, and C are positions where dial gauges or non-contact displacement sensors are installed on the test bar 10 from the table. By measuring in the X, Y, and Z directions with time, the displacement relative to the table is known.
In addition, as a technique using a non-contact sensor, there is a technique disclosed in Patent Document 1.

Secondly, as shown in FIGS. 7 and 8, the ball end mill performs groove cutting in the vertical direction and the horizontal direction, and increases the groove cutting step by step with the passage of time. This groove is always a crossing path, and the displacement is read from the state of the groove width that appears on the groove bottom.
In FIG. 7, the groove B is processed simultaneously with the processing of the lateral groove A, and thereafter, the grooves C, D, E,. C and D are deep with respect to the groove A, and E is restored. On the other hand, since F is shallower and the ball diameter is the same, the displacement from the reference position of the width a to Z shown in FIG. 8 can be obtained geometrically.

Third, as shown in FIG. 9, as time passes, a flat end mill 11 performs groove cutting or single-wall cutting at a certain depth on the plane of the workpiece W, and measures thermal displacement from the height difference of the processing bottom surface. To do.
In this way, if the flat end mill 11 sequentially performs groove cutting or single-sided cutting with the passage of time and measures the thermal displacement of the Z axis by measuring the height of the bottom surface, the actual condition when a constant groove depth is indicated. The amount of displacement can be measured from the difference from the measured value.

Japanese Patent Laid-Open No. 5-92353

However, in the method shown in FIG. 6, the graph data is created based on the measurement data, and the thermal displacement cannot be expressed directly.
In the method shown in FIGS. 7 and 8, although the cutting work can be directly visually recognized, numerical values need to be calculated separately, and a microscope with a scale is required for measurement, which is not easy.
In the method shown in FIG. 9, even if the cutting workpiece is viewed, it cannot be understood that the height from the processing bottom surface is not measured.
That is, in any measurement method, it was not possible to evaluate the numerical value as it was by looking at the workpiece.

  Therefore, the present invention has an object of proposing a displacement amount confirmation machining method in which displacement evaluation by heat or the like can be easily performed simultaneously with the completion of cutting, and a displacement amount confirmation workpiece obtained by this method. .

In order to achieve the above object, according to the first aspect of the present invention, a predetermined shape is processed by a rotary tool mounted on a machine tool on the plane of a workpiece having a plane perpendicular to the rotary tool axis. While changing the cutting amount in the axial direction at a predetermined pitch, the machining position is sequentially moved in a predetermined direction on the plane to perform a plurality of times in a row, and this row processing is further performed while changing the temperature of the machine tool. It is characterized in that the process is repeated a plurality of times every time and in a state where there is almost no temperature change in each column so that the columns are parallel to each other.
Invention according to claim 2, in addition to the purpose of claim 1, a machine tool equipped with a temperature compensation function, in order to clarify the effectiveness of the function, the thermal displacement at the same temperature conditions Row processing is performed separately for the state in which the correction function is turned on and the state in which the correction function is turned off.

In order to achieve the above object, a third aspect of the present invention is a displacement amount confirmation workpiece obtained by the displacement amount confirmation processing method according to the first or second aspect .
In the present invention, the change in the amount of cut in the direction of the rotary tool axis includes a numerical value on the + (plus) side that does not contact the workpiece.

According to invention of Claim 1 and 3 , the thermal displacement which arises in a machine tool by temperature change can be recognized clearly by the presence or absence of a process trace simultaneously with completion of a process. In particular, since row processing of a predetermined shape is performed in order from different places, the machining trace becomes a bar graph shape, which facilitates understanding when the workpiece is visually recognized. Moreover, since this row | line process is performed for every predetermined time, the change of the thermal displacement amount for every time can also be understood easily.
Furthermore, since the row processing for each predetermined time is performed in parallel with each other, it is possible to easily understand the change in the amount of thermal displacement for each predetermined time.
Then, by comparing and examining the method of changing the machine tool temperature every predetermined time and the result of the row machining, it becomes easy to confirm the characteristics of the thermal displacement of the target machine tool.

According to the second aspect of the present invention, in addition to the effect of the first aspect , the change of the thermal displacement amount can be easily understood for each of ON / OFF of the thermal displacement correction function, and the generated thermal displacement is corrected. The effectiveness of the thermal displacement compensation function is obvious.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<< Form 1 >>
FIG. 1 is an explanatory view of a displacement amount confirmation workpiece (hereinafter simply referred to as “workpiece”) 1 processed by the displacement amount confirmation processing method of the present invention. The lower side is a cross-sectional view of the processed portion of the row t0. 2 is an explanatory view showing a machining state in the circular portion of FIG. 1, and FIG. 3 is a partial perspective view of the workpiece.
The workpiece 1 has a square plate shape, and grooves 2, 2,... (Squares shown by solid lines) are formed in the X and Y directions by an end mill 4 on an upper surface that is a plane orthogonal to the Z axis. . In addition, squares 3, 3,... Indicated by two-dot chain lines in the same figure indicate portions where the end mill 4 has been moved so as to be processed but not actually processed.

  In FIG. 1, the cutting depth (Z axis) of the end mill 4 when cutting the uppermost grooves 2, 2,... Is constant at −10 μm. It is a standard for confirmation. The grooves 2, 2... Below the second row (showing t0 on the left side in the figure) are cut by raising each 1 μm in the Z direction every time they move to the right as shown on the upper side in the figure. ing. That is, the top surface height of the workpiece 1 is set to Z = 0, and the Z command is a height that is −3 to +5, and the row machining is performed nine times while moving the cutting portion for each pitch. is there. However, here, the grooves 2 in one row are cut almost at the same time. However, in each row in the Y-axis direction, as shown below, similar row machining is performed after a predetermined time. The first cutting points are aligned in the Y direction so that the columns are parallel to each other.

First, row processing at t0 is cutting at the start, that is, in a state where no thermal displacement has occurred, and this is barely visible at the Z axis 0 μm position, and on the left side (main axis position is minus, that is, Z−). A processing mark (groove 2) remains, but no processing mark remains on the right side (square 3).
After the row machining at t0, as shown in FIG. 4, the room temperature is changed so that the temperature of the machine tool rises, stays constant, and falls with time. This can be realized by installing a machine tool such as a machining center in a temperature-controlled room.

Thus, at the first row processing t1 in the third row, the room temperature is changed, and due to this influence, the main shaft is displaced in the Z direction to-(minus). For this reason, as a result of performing the row machining with the same Z command as at time t0, the groove 2 is cut below +1 μm, but no machining trace remains on the right side.
In the next row processing t2, the room temperature further changes, but at this time, the main axis changes by 2 μm in the Z direction. Therefore, in the row processing in this state, the groove 2 is cut at +2 μm or less.
Subsequently, the row processing t3 to t4 after a unit time has further changed at room temperature, but since the thermal displacement of the machine tool maintains the same state as at t2, the machining trace is also in the same state as at t2. It has become.
At t5, since the change in room temperature has started to return, the change in the Z direction has also started to return. As a result of the row processing in this state, the thermal displacement is the same as t1.
Since the room temperature has returned to the original at t6, the displacement in the Z direction also returns to the original, resulting in the same processing result as at time t0, and the groove 2 is processed only at a position of 0 μm or less.

As described above, according to the displacement amount confirmation processing method and workpiece 1 of the first aspect, the end mill 4 performs grooving on the upper surface of the workpiece 1, and the cut amount in the Z-axis direction is set to a predetermined pitch (1 μm). ) Is performed in order to move the machining position in order for each pitch while changing the number of times, and the row machining is performed a plurality of times, and the rows are parallel to each other at predetermined time intervals while changing the temperature of the machine tool. As described above, the thermal displacement caused by the temperature change can be clearly recognized by the presence / absence of the groove 2 simultaneously with the completion of the processing. In particular, since row processing of a predetermined shape is sequentially performed by a command value that is gradually changed in the Z-axis direction, the amount of thermal displacement corresponding to the passage of time becomes a bar graph shape by the groove 2, and understanding when the workpiece 1 is visually recognized. It becomes easy. Further, by comparing and examining the method of changing the machine tool temperature every predetermined time and the result of row machining, it becomes easy to confirm the characteristics of the thermal displacement of the target machine tool.
Here, since the first machining locations of each row machining are aligned in the direction orthogonal to the row machining direction, the change in the amount of thermal displacement per predetermined time can be more easily understood. .

  In the above embodiment, the number of squares in each column is comprised of 9 pieces of data, from −3 to +5 μm, but it can be increased or decreased depending on the accuracy. In addition, row processing is carried out in 7 rows from t0 to t6, but in order to see the difference due to room temperature change more accurately, the measurement time is increased or the row processing interval is shortened while keeping the same time interval. The number of times can be increased, and the mode of room temperature change can be changed as appropriate. Furthermore, although the amount of change in the Z direction cut in the X direction square is 1 μm pitch, it can be made larger or smaller depending on the thermal displacement characteristics of the machine tool and the width of the room temperature to be changed. It is.

  In addition, the shape of the groove may be a circle shape, other figures, numerical characters, marks, or a combination of these may be used, and each shape may be separated without being unified, and created by an NC program. The shape can be changed as appropriate as long as it is possible. Further, in the above embodiment, the shape is divided for each predetermined pitch. However, for example, a shape such as a straight line extending over a plurality of pitches / processing points may be processed. In this case, the pitch / processing points are subdivided. By doing so, it can be processed into a single shape (for example, a straight line) with a smooth change in pitch. Further, the numerical value may be matched with the pitch in the Z direction so that the thermal displacement can be directly recognized from the portion where the numerical value remains. In addition, as a cutting tool, a radius end mill or a ball end mill may be used without using a flat end mill. When using a ball end mill, the line width of the figure to be cut differs depending on the depth of cut, so that it is possible to further increase the display disassembly capability in the Z direction.

  On the other hand, in the above embodiment, thermal displacement is generated by changing the room temperature. However, as a method of changing the temperature of the machine tool, a workpiece (for example, a mold) as an actual production activity is performed during a unit time interval. ), Or by preparing a predetermined program and performing a so-called idle operation that periodically operates the spindle and feed axis, the machine tool itself due to heat generated by the cutting point, spindle and feed axis motors and feed axes, etc. The temperature may be changed, or these may be combined with room temperature control.

<< Form 2 >>
Next, another embodiment of the present invention will be described. In addition, since the same code | symbol as the form 1 shows the same structure part, the overlapping description is abbreviate | omitted.
For example, as disclosed in Japanese Patent Application Laid-Open No. 2003-39278, which is the prior application of the present applicant, the machine tool corresponds to a temperature detection unit that measures the temperature of each part of the machine, and the temperature measured by the temperature detection unit. A machine tool comprising: a correction amount estimating unit for estimating a thermal displacement correction amount; and a machining control unit for calculating an axis correction coordinate based on the thermal displacement correction amount from the correction amount estimating unit and outputting a correction command to a correction target axis. In many cases, a function of automatically correcting the thermal displacement based on the temperature is provided. In this case, not only the thermal displacement amount of the machine tool but also the characteristics of the thermal displacement correction function may be confirmed. Therefore, if the thermal displacement amount confirmation method described in the first embodiment is performed for each ON / OFF of the thermal displacement correction, both can be compared and the characteristics of the thermal displacement correction function can be confirmed.

  Specifically, in the same manner as in the first mode, every time when moving to the right, the row processing in which the groove 2 is raised by 1 μm in the Z direction and the nine grooves 2 are cut in a row is processed as shown in FIG. 7 is performed every predetermined time by changing the temperature so that the temperature rises, stays constant, and descends. At this time, as shown in FIG. 5, the plate-like body is machined every predetermined time (t0 to t6). The row processing is performed a plurality of times on the upper surface of the object 1a in each of the states of thermal displacement correction OFF (left) and ON (right).

First, in the row machining at the start t0, the tool tip is set to Z = 0, so that four grooves 2 up to Z = 0 are generated, and the machining trace is not generated in the machining after Z = 1 μm. Remains in its initial state (the five squares 3 on the right).
In the row machining after t1, since the temperature rises from the initial state, the machine is thermally displaced. For example, when the tool tip is deformed so as to approach the workpiece 1a, machining is performed with Z = 0 command in a state where the thermal displacement correction is OFF. Even so, the tool is not only in contact with the workpiece 1a but also cut. Therefore, as the temperature rises, the squares (grooves 2) generated as shown in the left half of FIG. 5 increase. The change in the number of grooves 2 for each row is the same as that described in FIG.
On the other hand, when row processing is performed with the thermal displacement correction turned ON, the thermal displacement of the machine is corrected, and the number of grooves 2 generated as shown in the right half of FIG. Does not change.

Thus, according to the thermal displacement amount confirmation method and workpiece 1a of the above-described form 2, the same effect as in form 1 can be obtained in which the thermal displacement caused by the temperature change can be clearly recognized by the bar graph-like groove 2. . In particular, by changing the thermal displacement correction function to ON and OFF by changing the thermal displacement correction function to ON and OFF, the row processing is performed a plurality of times. However, it can be easily understood by visually recognizing the workpiece 1a, and the generated thermal displacement and the effectiveness of the thermal displacement correction function for correcting the thermal displacement become obvious at a glance.
Further, here, since the same workpiece 1a is processed at the same temperature state in both the ON / OFF states of the thermal displacement correction function, the thermal displacement correction function of the machine tool to be checked for the amount of thermal displacement is provided. It becomes easy to grasp the performance.

  In the above-described embodiment 2, the machining with each of the thermal displacements ON / OFF is formed on the same workpiece, but may be a separate workpiece. In addition, the thermal displacement correction OFF (left side) is processed at each time point from t0 to t6, and then the thermal displacement correction function is turned ON to process the right side. However, these may be performed at the same timing. If the temperature state and the change can be made the same, they may be performed separately. That is, the same room temperature change is made, or the same workpiece (for example, a mold) is processed as an actual production activity during a unit time interval, or a predetermined program is prepared and the spindle and feed axis are periodically It is possible to carry out modifications such as so-called idling that is operated, or in combination with room temperature control.

In the first and second embodiments, the change in the relative position between the tool and the workpiece has been described by taking the thermal displacement as an example. However, the present invention is not limited to this. For example, tool change, pallet change Needless to say, the repeatability in the operation of attaching and detaching a tool or workpiece to or from a machine tool, such as attaching or detaching a workpiece by a robot, can be similarly evaluated. That is, in the case of tool change, the tool change time becomes a predetermined time, the tool change operation is repeatedly performed using the automatic tool changer, and the processing shown in the form 1 is performed when the tool is attached to the spindle. It ’s fine. Similarly, in the case of pallet exchange, the workpiece 1 fixed on the pallet may be processed when the pallet is attached to the machine tool using an automatic pallet exchange device.

It is explanatory drawing of the workpiece of form 1. It is explanatory drawing which shows the process state of a groove | channel. It is a partial perspective view of a workpiece. It is a graph which shows time passage and room temperature change. It is explanatory drawing of the workpiece of form 2. It is explanatory drawing which shows the conventional thermal displacement amount measuring method. It is explanatory drawing which shows the conventional thermal displacement amount measuring method. It is explanatory drawing which shows the conventional thermal displacement amount measuring method. It is explanatory drawing which shows the conventional thermal displacement amount measuring method.

Explanation of symbols

1, 1a ... Workpiece, 2. Groove, 3 .... Square, 4 .... End mill.

Claims (3)

To said plane of the workpiece with a plane perpendicular to the rotary tool axis, the machining of a predetermined shape by a rotary tool mounted on the machine tool, the machining portion while changing the depth of cut of the rotary tool axis direction at a predetermined pitch Move in order in a predetermined direction on a plane and perform a plurality of times in a row, and further, this row processing is performed every predetermined time while changing the temperature of the machine tool, and there is almost no temperature change in each row, A machining method for confirming a displacement amount of a machine tool, which is repeated a plurality of times so that each row is parallel to each other. If the machine tool has a function to automatically correct the thermal displacement, it is divided into a state where this thermal displacement correction function is turned on and a state where it is turned off at the same temperature state. The machining method for confirming the amount of displacement of the machine tool according to claim 1 . Claim 1 or displacement confirmation workpiece obtained by the displacement amount confirmation processing method according to 2.

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