JP4471485B2 - Correction method for thermal displacement between two feed screws - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for correcting a thermal displacement of a feed screw, and in particular, between two points of a feed screw that adjusts the positions of two points on both ends of the feed screw in accordance with the workpiece width and corrects a stroke error between the two points. The present invention relates to a thermal displacement correction method and apparatus.
[0002]
[Prior art]
Conventionally, as a method for correcting the thermal displacement of a feed screw in a machine tool, one disclosed in Japanese Patent Application Laid-Open No. 11-254273 developed by the present applicant has been proposed.
[0003]
The above-mentioned Japanese Patent Application Laid-Open No. 11-254273 measures the true value of the total length of the lead screw and the distance from the machine origin at the two ends of the lead screw to determine the error from the true value. This is a two-point thermal displacement correction method in which an origin shift amount and a pitch error correction value are determined and error correction is performed for the entire stroke. Thereby, first, the true value of the total length of the feed screw and the distances from the machine origin at the two ends of the feed screw are measured, and the error from the true value is obtained. Subsequently, an origin shift amount and a pitch error correction value are determined from the error. Thereby, the error correction of the whole stroke area between the two points of the feed screw can be accurately performed.
[0004]
Since the setting between the two points of the feed screw is a fixed type, it is not related to the size of the workpiece. For this reason, when the workpiece width is close to the set distance between the two points, the thermal displacement correction is accurately executed by the proximity of the two. However, if the workpiece width is extremely narrow with respect to the set distance between the two points, the stroke part unnecessary for machining will be expanded, so even if it is set between the two folding points and the thermal displacement is corrected, the correction error will be expanded. There's a problem.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the problems seen in the above-described conventional two-point thermal displacement correction method. The object of the present invention is to adjust the position of two points on both ends of the feed screw in accordance with the work width and to correct the thermal displacement between the two points of the feed screw and to correct the stroke error between the two points. The purpose is to provide.
[0006]
The method for correcting thermal displacement between two points of a feed screw according to claim 1 of the present invention measures the true value of the total length of the feed screw and the distances from the machine origin of the two points on both ends of the feed screw. In the method for correcting the thermal displacement between two points of the feed screw by determining the origin shift amount and the pitch error correction value from the above error and correcting the error over the entire stroke, the positions of the two points on both ends of the feed screw are set to the workpiece width. The stroke error correction between the two point positions is performed by adjusting the close relationship .
[0008]
[Action]
In the method for correcting the thermal displacement between the two points of the feed screw according to the first aspect, since the setting between the two points of the feed screw is an adjustment type, it can be adjusted in relation to the size of the workpiece. For this reason, if the set distance between the two points is adjusted so as to be close to the workpiece width, the thermal displacement correction is more accurately executed by the closeness of the two. Therefore, since the two sensors are brought closer to the workpiece width with respect to the set distance between the two points to reduce the stroke portion unnecessary for machining, the correction error of the set distance between the two points is suppressed to the minimum value. It is possible to correct the thermal displacement of the lead screw exactly and unmatched by the lead screw thermal displacement correction method.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to embodiments shown in the drawings. FIG. 1 is a front view of a feed screw two-point correction apparatus for carrying out the feed screw two-point thermal displacement correction method of the present invention, and FIG. 2 is an action diagram of the feed screw two-point thermal displacement correction method. 3 is a plan view of the feed screw two-point detection means, and FIG. 4 is a left side view of the two-point detection means.
[0011]
The feed screw two-point thermal displacement correction method and the feed screw two-point thermal displacement correction apparatus 100 that implements this will be described with reference to FIGS. In FIG. 1, a feed screw 12 is screwed to a table 10 that is one of moving bodies of a machine tool, and the table 10 is moved left and right by forward and reverse rotation of the feed screw 12. A tension bearing 14 is supported on one side of the feed screw 12. A pulse motor PM is connected to the feed screw 12 of the fixed side bearing 16. The pulse motor PM controls the feed of the table 10 in a specified direction by a predetermined amount in response to a feed command from the NC controller 20. At this time, if the feed screw 12 is thermally displaced, an error occurs in the amount of movement of the table 10 with respect to the rotation of the pulse motor PM because it is different from the true length.
[0012]
The present invention corrects the thermal displacement error of the movement amount of the table 10 in accordance with the workpiece width. The table 10 has a measuring point (О1) slightly separated from the machine origin (О) and a measuring point (О2) just before the stroke end (O3) when the table 10 passes between the two-point detecting means. Is detected by the position detection sensor S. The position detection sensor S is a proximity switch fixed to the machine body and detects the magnet pieces M1 and M2 arranged at the measurement points (O1) and (O2) on the table 10 and sends detection signals to the NC controller 20. It comes to send to.
[0013]
The mounting configuration of the position detection sensor S and the magnet pieces M1, M2 is shown in FIGS. The position detection sensor S is a magnetic proximity switch, and a mounting body 2 is fastened and fixed to a fixed side 1 of the machine body with a bolt 5. The other two magnet pieces M1 and M2 are attached to the side surface of the table 10 with a guide bar 30 having a U-shaped cross section directed in the moving direction thereof so that the movement can be adjusted. The mounting structure includes a magnet mounting body 36, 37 in which a nut body 34.35 screwed with the bolt 31, 32 is fitted in the groove 30a of the guide bar 30, and magnet pieces M1, M2 are attached to the head side of the bolt. Are fastened to the nut body and fixed in place. Therefore, the measurement points (O1) and (O2) that are the attachment positions of the magnet pieces M1 and M2 are finely adjusted by loosening the bolts 31 and 32 and continuously adjusting the magnet attachment bodies 36 and 37 in the lateral movement direction. can do.
[0014]
FIG. 2 shows a relationship diagram between the movement amount L of the table 10 and each measurement point (O1) and measurement point (O2). The distance L of the table 10 is (L1), the distance from the machine origin (О) to the measurement point (О1), and the distance from the machine origin (О) to the measurement point (О2) as (L2). To do. On the other hand, the error ± ΔE from the true value (E) with respect to the movement amount L of the table 10 is indicated by the vertical axis, and becomes the error −ΔE1 of the measurement point (О1), and the error of the measurement point (О2) is + It is represented by an error curve E ′ that becomes ΔE2. The above error curve E ′ shows the distance between two points from the measurement point (О1) slightly away from the machine origin (О) and the measurement point (О2) close to the stroke end (О3) from the machine origin (О). The origin shift amount and the pinch error correction value are determined by measuring and obtaining an error ± ΔE between the true value (E) and the actual feed amount with respect to the table feed amount. This makes it possible to correct the error over the entire stroke.
[0015]
The feed screw two-point thermal displacement correction apparatus 100 that performs the feed screw two-point thermal displacement correction method of the present invention is configured as described above and operates as follows.
First, normal pinch error correction is performed using a laser measuring instrument or the like. Immediately after the error correction, the position detection sensor S measures the distances (L1) and (L2) from the mechanical origin (O) of the moving body 10 to the measurement points (O1) and (O2). This is stored as a true value (E).
Next, during or after machining, the position detection sensor S measures the distances (L1 ′) and (L2 ′) from the machine origin (O) of the moving body 10 to the measurement points (O1) and (O2). To do. This is the true value (E ′) and is shown in FIG. Here, from (L2'-L2)-(L1'-L1) / (L2-L1) = ΔL2-ΔL1 / L2-L1, ΔL2-ΔL1 / L2-L1 = magnet pieces M1, M2 The amount of elongation between the two attachment positions / the true distance between the two attachment positions of the magnet pieces M1 and M2, and the gradient of the actually measured value (E ′) is determined. Further, ΔE = ΔL1− (ΔL2−ΔL1 / L2−L1) × L1, and the coordinate correction amount at the mechanical origin (O) can be obtained.
[0016]
As described above, the basic method for correcting the thermal displacement between two feed screw points is to measure the true value of the total length of the feed screw and the distance from the machine origin (О) at two points on both sides of the feed screw. Find the error from the value of. The origin shift amount and the pinch error correction value are determined from the error. Thereby, error correction over the entire stroke of the feed screw is performed with high accuracy.
[0017]
In particular, the method for correcting the thermal displacement between two points of the feed screw according to the present invention can be adjusted in relation to the size of the workpiece because the setting between the two points of the feed screw is an adjustment type. For this reason, if the set distance between the two points at the measurement point (O1) and the measurement point (O2) from the machine origin (O) of the moving body 10 is adjusted to be close to the width W1 of the workpiece W, the two can approach each other. Thermal displacement correction is performed even more accurately. Therefore, since the workpiece width is made closer to the set distance between the two points to reduce the stroke portion unnecessary for machining, the correction error of the set distance between the two points is suppressed to the minimum value, and the conventional feed screw thermal displacement is reduced. It is possible to correct the thermal displacement of the lead screw exactly and unmatched by the correction method.
[0018]
Moreover, about the feed screw two-point thermal displacement correction apparatus 100, since the setting between the two points of the feed screw is an adjustment type, it can be adjusted in relation to the size of the workpiece. For this reason, if the set distance between the two points is adjusted to be close to the workpiece width, the thermal displacement correction is accurately executed by the closeness of both. Therefore, since the measurement point (О1) and measurement point (О2), which are set distance between two points, are brought close to the workpiece width and the stroke part unnecessary for machining is reduced, the correction error of the set distance between the two points is minimized. Therefore, it is possible to provide a two-point feed screw thermal displacement correction device that performs accurate and unmatched feed screw thermal displacement correction, which is limited by the value and is not found in conventional feed screw thermal displacement correction devices. As shown in FIGS. 3 and 4, the adjustment of the set distance between the two points is performed by moving the magnet pieces M1 and M2 arranged at the measurement points (O1) and (O2) left and right along the groove 30a of the guide bar 30. This is done by adjusting and fixing.
[0019]
The present invention is not limited to the above-described embodiment. For example, the point-to-point detection means is not limited to that shown in the figure, and various types of sensors and switches and their attachment / adjustment means can be used. Furthermore, the moving body of the machine tool is not limited to the table 10, and may be a moving column, a saddle, a spindle head, or a ram.
[0020]
【The invention's effect】
According to the first aspect of the present invention, the two point positions on both ends of the feed screw are adjusted in accordance with the workpiece width, and the stroke error between the two point positions is corrected. Displacement correction can be implemented and controlled with high accuracy and efficiency.
[Brief description of the drawings]
FIG. 1 is a front view of a two-point feed screw thermal displacement correction apparatus for carrying out a two-point feed screw thermal displacement correction method of the present invention.
FIG. 2 is an action diagram of a method for correcting a thermal displacement between two points.
FIG. 3 is a plan view of a point-to-point detection unit.
FIG. 4 is a left side view of the point-to-point detection means.
DESCRIPTION OF SYMBOLS 1 Machine side fixed side 2 Attachment body 5 Bolt 10 Table 12 Feed screw 14 Tensile bearing 16 Fixed side bearing 20 NC controller 30 Guide bar 30a Groove 31, 32 Bolt 34.35 Nut body 36, 37 Magnet attachment body E True Value E 'Error curve L Travel distance L1 Distance from machine origin (О) to measurement point (О1) L2 Distance from machine origin (О) to measurement point (О2) О Machine origin O1, O2 Measurement point O3 Stroke end S Position detection sensor PM Pulse motor M1, M2 Magnet piece 100 Thermal displacement correction device between two feed screws

Claims (1)

  Measure the true value of the total length of the feed screw and the distance from the machine origin at the two ends of the feed screw, find the error from the true value, and determine the origin shift amount and pitch error correction value from the above errors Then, in the method for correcting the thermal displacement between the two points of the feed screw that corrects the error in the entire stroke, the position of the two points on both ends of the feed screw is adjusted to be close to the workpiece width, and the stroke error between the two points is corrected. A method for correcting thermal displacement between two feed screws.

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