JPH05100723A - Tool length correcting system for machine tool - Google Patents

Abstract

PURPOSE:To improve machining accuracy by controlling a machining path so as to be a straight line in the case linear interpolation is executed in a machine tool provide with a rotary head. CONSTITUTION:A tool length correction vector V is calculated for every distribution period in accordance with the angle of an axis of rotation for controlling the inclination of the rotary head, and tool length is corrected based on the calculated tool length correction vector V. Besides, the distribution pulse vector DELTAU of the command path of a tool tip path is calculated by the linear interpolation, and the variation vector DELTAV of the tool length correction vector V at every distribution period is calculated in accordance with the angle of the axis of rotation, and the distribution pulse vector DELTAP of a tool standard position after the correction of the tool length is calculated from the calculated distribution pulse vector DELTAU of the command path and the variation vector DELTAV. Thus, when the tool standard position is moved along a moving curve L4, the actual machining path of the tool tip comes to conform with the command like the straight line L3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool length correcting method for a machine tool, and more particularly to a machine tool having a rotary head having at least one rotary shaft, the rotary shaft of the tool being arbitrarily inclined with respect to the Z axis. This invention relates to a tool length correction method for machine tools that sometimes corrects the tool length.

[0002]

2. Description of the Related Art Conventionally, some numerically controlled machine tools have a rotary head in which a head for holding a tool can be rotated in order to process a complicated mold or the like. In a machine tool having such a rotary head, when the tool rotation axis is arbitrarily tilted with respect to the Z axis, the tool length correction amount changes according to the size of the tilt angle. A tool correction method in which a tool length correction vector is obtained and the tool length is corrected is known in, for example, Japanese Patent Laid-Open No. 3-109606.

FIG. 4 is a schematic view of a rotary head of a machine tool to which the above correction method is applied. In the figure, the rotary head 1 can rotate about a B axis 3 parallel to the Y axis, and can also rotate about a C axis 4 parallel to the Z axis. A tool 5 is provided at the tip of the C-axis 4. The tool reference position on the rotary head 1 corresponding to the position where the tool offset amount is zero is G, and the tip position of the tool 5 is H.

FIG. 5 shows the tool reference position G and the tool tip.
FIG. 6 is a diagram showing a locus of movement of the end position H in the processing block.
is there. Hereinafter, description will be given with reference to FIGS. 4 and 5. the above
In the tool compensation method, a tool is used for each end point of the machining block.
Calculate the length correction vector V and calculate the calculated tool length
Within the machining block by performing tool length compensation with vector V
Tool reference position G at start point S and end point E of_S, G_ECalculate
To do. And especially for linear interpolation,
Two tool reference positions G_S, G _ETool reference position between
Tool movement control is performed so that G moves along the straight line L1.
Done.

[0005]

However, when the tool reference position G moves along the straight line L1 between the two tool reference positions G _S and G _E as in the above tool movement control, the actual machining path is The locus of movement of the tool tip position H is as shown by the curve L2 in FIG. Originally, the commanded tool path is the tool tip position H _S at the start point S and the end point E in the machining block,
Despite the straight line L3 connecting H _E , the actual tool tip path becomes a curve L2 as the rotary head rotates between the start point S and the end point E. The curvature of the curve L2 shown in FIG. 5 is expressed to be slightly larger than it actually is.

Therefore, there is a problem that the machining accuracy is deteriorated when the machining according to the command is not performed and the rotary head largely rotates between the start point S and the end point E in the machining block.

The present invention has been made in view of the above circumstances, and improves the machining accuracy by controlling the machining path to be a straight line when linear interpolation is performed by a machine tool having a rotary head. It is an object of the present invention to provide a tool length correction method for a machine tool designed to achieve the above.

[0008]

In order to solve the above problems, the present invention is directed to controlling the inclination of a rotary head in a tool length correction system for a machine tool having a rotary head having at least one rotary shaft. The tool length correction vector (V) is calculated for each distribution cycle according to the angle of the rotation axis of
There is provided a tool length correction method for a machine tool, which corrects a tool length based on the calculated tool length correction vector (V).

Further, in a tool length correction method for a machine tool having a rotary head having at least one rotation axis, a distributed pulse vector (ΔU) of a command path which is a tool tip path is calculated by linear interpolation, and the rotation is performed. A variation vector (ΔV) of the tool length correction vector (V) for each distribution cycle is calculated according to the axis angle, and the calculated distribution pulse vector (ΔU) and the calculated variation vector (ΔV). From the above, there is provided a tool length correction method for a machine tool, which is characterized in that a distribution pulse vector (ΔP) of a tool reference position after the tool length correction is calculated.

[0010]

A tool length correction vector (V) is provided for each distribution cycle according to the angle of the rotary shaft for controlling the inclination of the rotary head.
Is calculated, and the tool length is corrected based on the calculated tool length correction vector (V).

The distribution pulse vector (ΔU) of the command path which is the tool tip path is calculated by linear interpolation, and the variation amount vector (V) of the tool length correction vector (V) for each distribution cycle is calculated according to the angle of the rotary axis. [Delta] V) is calculated, and from the calculated distribution pulse vector ([Delta] U) of the command path and the calculated variation vector ([Delta] V), the distribution pulse vector of the tool reference position after the tool length is corrected. Calculate (ΔP).

Thus, when the machine tool having the rotary head performs the linear interpolation, the actual machining path can be made a straight line.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a hardware block diagram of a 5-axis control numerical controller (CNC) to which the present invention is applied. In the figure, 10 is a numerical controller (CNC). A processor (CPU) 11 is a central processor for controlling the numerical control device 10 as a whole, and a RO is connected via a bus 21.
The system program stored in M12 is read, and the control of the numerical controller 10 as a whole is executed in accordance with this system program. The RAM 13 stores temporary calculation data, display data, and the like. RAM13 has SRA
M is used. The non-volatile memory 14 stores a tool diameter correction amount, a pitch error correction amount, a machining program, parameters and the like. The non-volatile memory 14 is composed of a CMOS backed up by a battery (not shown), and even when the power of the numerical control device 10 is turned off, those data are retained as they are.

The interface (INT) 15 is an interface for an external device, and is connected to an external device (TR) 31 such as a paper tape reader, a paper tape puncher, or a paper tape reader / puncher. The processing program is read from the paper tape reader, and the processing program edited in the numerical controller 10 can be output to the paper tape puncher.

A PMC (Programmable Machine Controller) 16 is built in the numerical controller 10 and controls the machine with a sequence program created in a ladder format. That is, the M function instructed by the machining program,
According to the S function and T function, these are converted into necessary signals on the machine side by the sequence program, and the I / O unit 1
Output from 7 to the machine side. This output signal drives a magnet or the like on the machine side to operate a hydraulic valve, a pneumatic valve, an electric actuator, or the like. Also, in response to signals from the machine side limit switch and machine control panel switch,
Perform necessary processing and pass it to the processor 11.

The current position of each axis, alarms, parameters,
Image signals such as image data are sent to the CRT / MDI unit 25
Is sent to the display device and displayed on the display device. The interface (INT) 19 receives data from the keyboard in the CRT / MDI unit 25 and transfers it to the processor 11.

The interface (INT) 20 is connected to the manual pulse generator 32 and receives pulses from the manual pulse generator 32. The manual pulse generator 32 is mounted on the machine operation panel and is used to manually precisely position the working part of the machine.

The axis control circuits 41 to 45 receive the movement command of each axis from the processor 11 and output the command of each axis to the servo amplifiers 51 to 55. The servo amplifiers 51 to 55 receive the movement command and drive the servo motors 61 to 65 for the respective axes (X, Y, Z, B, C axes). Servo motor 61
A pulse coder for position detection is built in to 65, and a position signal is fed back from each pulse coder to each axis control circuit 41 to 45 as a pulse train. In some cases, a linear scale is used as the position detector. A speed signal can be generated by F / V (frequency / speed) conversion of this pulse train.
In the figure, the feedback line and velocity feedback of these position signals are omitted.

The spindle control circuit 71 receives a spindle rotation command and a spindle orientation command and outputs a spindle speed signal to a spindle amplifier 72. The spindle amplifier 72 receives the spindle speed signal and rotates the spindle motor 73 at the commanded rotation speed. In addition, the spindle is positioned at a predetermined position according to the orientation command.

A position coder 82 is connected to the spindle motor 73 by a gear or a belt. Therefore, the position coder 82 rotates in synchronization with the spindle 73, outputs a feedback pulse, and the feedback pulse is read by the processor 11 via the interface 81. This feedback pulse moves the other shaft in synchronization with the spindle motor 73, enabling precise tapping processing and the like.

FIG. 3 is a flow chart of a processing program of the tool length correction method executed by the numerical control device configured as described above. This program is stored in the ROM 12 and is executed by the processor 11 every distribution cycle (for example, 8 msec). The numbers following S in the figure represent step numbers.

Prior to the description of FIG. 3, the book will be described with reference to FIG.
A state of tool movement control in the invention will be described. Rotary
The head rotates between the start point S and the end point E in the processing block.
Even so, the actual movement of the tool tip depends on the start point S in the block.
And tool tip position H at end point E_S, H _EStraight line L connecting between
Tool reference position G in order to be carried out along 3
So that the movement within the machining block of is performed along the curve L4
To This curve L4 is the starting point S and
G which is the tool reference position at the end point E_S, G_ECurve connecting between
And the tool reference position G_SIn addition, the work calculated for each distribution cycle
The distributed pulse vector ΔP at the tool reference position can be sequentially added.
Obtained by. Calculation of this distributed pulse vector ΔP
The output method will be described by returning to FIG.

First, before the execution of step S1, the following values are set by reading the machining block. Command start position S = (S _X , S _Y , at the tool tip,
S _Z , S _B , S _C ) Command end position E = (E _X , E _Y , at the tool tip)
E _Z , E _B , E _C ) Tool reference position P = (P _X , P on the curve L4 for each distribution cycle)
_Y , P _Z , B, C) At the above three positions, the first to third terms in the parentheses represent the coordinate values of the X, Y and Z axes, and the fourth and fifth terms are B and C.
Indicates the rotational position of the axis. In the following vectors, each term represents a vector component on each axis similar to the above. Distribution pulse vector ΔP of the tool reference position at position P (corresponding to after tool length correction) = (ΔP _X , ΔP _Y , ΔP _Z , Δ
B, ΔC) Distribution pulse vector ΔU = (ΔU _X , ΔU _Y , ΔU _Z , ΔB, Δ) at the tool tip position on the command path Q for each distribution cycle
C) Tool length correction vector at position Q V = (V _X , V _Y ,
V _Z , 0, 0) Amount of change in tool length correction vector V at position Q ΔV = (ΔV
_X , ΔV _Y , ΔV _Z , 0, 0) Tool length correction vector fi (B, C) = Vi (i = X,
Y, Z) i.e., JP-A for the calculation of _{V X = hsin Bsin C V Y} = -hsin B COS C V Z = h COS B (h the tool offset amount _{.V X, V Y, V Z} 3-109606 (Detailed description in No.) Command speed F Distribution cycle ΔT The following steps are executed based on the values above. [S1] The distributed pulse vector ΔU at the tool tip position at the position Q is calculated as follows. ΔU corresponds to the tool length distribution pulse vector of each axis that does not include the tool length correction vector V.

First, since the tool moving speed on the machining path becomes the command speed F, the following formula is established. ΔU _X ² + ΔU _Y ² + ΔU _Z ² = (FΔT) ² (1) Further, since the command path is a straight line, that is, linear interpolation, the following formula is established. _{ΔU X: ΔU Y: ΔU Z} = (E X -S X) :( E Y -S Y) :( E Z -S Z) ··· (2) above (1) and (2), .DELTA.U Find _X , ΔU _Y , and ΔU _Z.

[S2] The distributed pulses ΔB and ΔC of the rotating shaft are
Calculate from the following formula. ΔU_i: ΔB: ΔC = (E_i-S_i): (E_B-S_B): (E_C-S_CHowever, i is | E among X, Y, and Z._X-S_X｜, ｜ E
_Y-S_Y｜, ｜ E_Z-S _ZThe maximum value of |
Try to choose the same as the six. [S3] Tool length
The variation amount ΔV of the correction vector V was obtained in step S2.
It is calculated based on the following formula using ΔB and ΔC. ΔV_i= Fi (B + ΔB, C + ΔC) -fi (B, C) (i = X, Y, Z) [S4] ΔU obtained in step S1 and step S3
Based on the following formula, using ΔV obtained in
The distribution pulse vector ΔP at the tool reference position is obtained. ΔP = ΔU + ΔV The relationship between the above values is shown in FIG. That is, position Q
Let Qa be the position on the straight line L3 after the next distribution cycle T of
And the distributed pulse vector ΔU at the tool tip position is Q, Q
It can be represented as the line between a. Also, the tool length correction vector V
Can be represented by a line connecting the position Q and the position P. here,
Of the same absolute value parallel to the tool length correction vector V from Qa
Draw a vector V, and let its end point be Pb, then position P
The line connecting the end point Pb is the distribution pulse vector of the tool tip position.
The vector ΔU is parallel to and has the same absolute value.

On the other hand, assuming that the tool length correction vector V at this time of the distribution cycle is represented by a line between Q and P, the tool length correction vector (V + ΔV) at the next time of the distribution cycle is Qa, Pa.
It can be represented as a line between. The position Pa is a position on the straight line L4 after the distribution period T following the position P. Therefore, the line between Pb and Pa corresponds to the variation amount ΔV of the tool length correction vector V, and therefore the distribution pulse vector ΔP of the tool reference position at the position P, which is the sum of ΔU and ΔV, is P,
This corresponds to the line between Pa.

That is, the distribution pulse vector ΔP of the tool reference position is a distribution pulse vector for each distribution cycle with respect to the tool reference position that is the movement control target, and the tool is in accordance with the distribution pulse vector ΔP for each distribution cycle starting from the point G _S. When the reference position is moved, the locus becomes a curve L4. Therefore, the tip position of the tool moves along the straight line L3 along the command path.

In the above description, the rotary head is controlled to tilt the tool, but other than this, the table may be tilted and the tool may be relatively tilted with respect to the work surface. In this case, the tool length correction vector and the distributed pulse vector ΔP are calculated from the current position of the axis controlling the table.

Although two axes are used to control the tool inclination, the present invention can be similarly applied to the case where the tool inclination is controlled by one axis.

[0030]

As described above, according to the present invention, the tool length correction vector (V) is calculated for each distribution cycle according to the angle of the rotary shaft for controlling the inclination of the rotary head, and the calculated tool length is calculated. The tool length is corrected based on the correction vector (V). Further, the distribution pulse vector (ΔU) of the command path which is the tool tip path and the variation vector (ΔV) of the tool length correction vector (V) for each distribution cycle are calculated, and the distribution pulse vector ( Calculate ΔP). Therefore, when linear interpolation is performed by a machine tool having a rotary head, the actual machining path can be made straight, and machining accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing trajectories of movement of a tool reference position and a tool tip position in the present invention.

FIG. 2 is a hardware block diagram of a five-axis control numerical controller (CNC) to which the present invention is applied.

FIG. 3 is a flowchart of a processing program of a tool length correction method executed by a numerical controller.

FIG. 4 is a schematic view of a rotary head of a machine tool.

FIG. 5 is a diagram showing a trajectory of movement of a conventional tool reference position and a tool tip position.

[Explanation of symbols]

G _S Tool reference position at starting point S in machining block H _S Tool tip position at starting point S in machining block G _E Tool reference position at end point E in machining block H _E Tool at end point E in machining block tip position P for each distribution period of the tool reference position Q tool tip dispensing each cycle position L3 tool tip position H _S, line L4 tool reference position connecting the H _E G _S, distribution curve ΔP tool reference position connecting the G _E Pulse vector ΔU Distribution pulse vector of command path which is tool tip path ΔV Change amount vector of tool length correction vector (V) for each distribution cycle

Claims (3)

[Claims] 1. A tool length correction system for a machine tool including a rotary head having at least one rotary shaft, wherein the tool length is corrected every distribution cycle according to the angle of the rotary shaft for controlling the inclination of the rotary head. A tool length correction method for a machine tool, which calculates a vector (V) and corrects the tool length based on the calculated tool length correction vector (V). 2. A distributed pulse vector (Δ) of a command path, which is a tool tip path, in a tool length correction method for a machine tool including a rotary head having at least one rotation axis.
U) is calculated by linear interpolation, a variation vector (ΔV) of the tool length correction vector (V) for each distribution cycle is calculated according to the angle of the rotation axis, and the calculated distribution pulse vector (ΔU) And the calculated variation vector (ΔV), the distribution pulse vector (Δ of the tool reference position after the tool length correction)
A tool length correction method for machine tools characterized by calculating P). 3. The distribution pulse vector (ΔP) of the tool reference position is the calculated distribution pulse vector (ΔU) of the command path and the calculated variation vector (ΔV).
The tool length correction method for a machine tool according to claim 2, wherein: