JPS6234492B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a numerical control device, and more particularly to a numerical control device that automatically removes incomplete threads during thread cutting and processes multi-thread threads.

Conventionally, in order to remove incomplete threads caused by the turret acceleration time constant during thread cutting, the length of the incomplete threads that are likely to occur is determined in advance based on data such as various constants during thread cutting and thread pitch. Humans manually calculated the length of the thread, and then used a machining program that incorporated the results to cut threads with no imperfect threads. In addition, when cutting a high-thread thread, a person must manually calculate the pitch deviation between the reference thread and the high-thread thread in advance, and then cut the high-thread thread using a program that shifts the starting point of thread cutting by the calculated amount. was being cut.

FIG. 1 shows the conventional machining procedure for a multi-thread screw without incomplete threads. First, in step (1), a machining program is created. That is, a programmer creates a machining program from a machining drawing having a desired machining shape, taking into consideration the shape, machining conditions, etc. Next, in step (2), the programmer calculates the length of the incomplete thread based on the machining program created in step (1). Then step (3)
Modify the machining program taking into account the incomplete thread length calculated in (2). Next, in step (4), the programmer calculates the pitch deviation of the multi-thread thread with respect to the reference thread. Step (5) is a step based on the program created in step (3).
Create a machining program in which the thread cutting starting point is shifted by the pitch deviation calculated in (4). In the case of an n-thread thread, n-1 machining programs in step (5) are created. Thereafter, in step (6), the operator inputs the n machining programs created in steps (3) and (5) into the numerical control device.
In step (7), the numerical control device sequentially issues commands according to the input machining program, and the machine tool performs thread cutting according to these commands.

Here, the incompletely threaded portion will be explained using FIG. 2. In the diagram of FIG. 2, 11 is a thread cutting tool for thread cutting, 12 is a workpiece to be thread cut, 13 is an acceleration curve when the tool rest is accelerated,
14 is the tool speed curve at the end of acceleration, and _δ1 is the length of the incomplete thread portion that occurs when the tool post accelerates. Here, when a thread cutting command is issued, the tool 11 waits for a thread cutting start synchronization signal at the commanded thread cutting starting point, and when this synchronization signal is given from the spindle rotation encoder, the tool 11 and the tool rest will be at a machining speed of zero. Acceleration starts from to the commanded machining speed. The acceleration curve of the tool 11 is shown in FIG. 213. Therefore, the portion cut during this acceleration becomes an incompletely threaded portion. Therefore, in order to cut a thread without an incomplete thread, it is necessary to shift the starting point of the tool 11 from the end surface of the workpiece 12 by the length δ ₁₁ of the incomplete thread. The length _δ1 of this incompletely threaded portion can be determined by the following formula [A] and formula [B].

δ ₁ = {t ₁ −(1/K _S +1/K _P )+K _P ² _e ^−Kst1 −K _S ² _e ^−KPt1 /(K _P −K _S )・K _P・K _S
}F×10 ³ /60mm……[A] a=△P/P=1/K _P −K _S (K _P e ^-Kst1 −K _S e ^-
KPt1 )...[B] Here, F is the feed rate of the tool during thread cutting (m/min), which is determined by the program as the multiplier of the thread pitch and the spindle rotation speed. K _S is the smoothing circuit gain, which is a constant of the numerical control device, K _P is the position loop gain, which is a constant of the numerical control device, p is the pitch of the screw according to the program, and △p is the pitch error, which is determined by the grade of the screw. . _t1 is the time until the pitch error reaches Δp. Therefore, δ ₁ is obtained from equations [A] and [B] based on program data F, parameter setting data Δp/p, and constants K _P and K _S of the numerical control device.

Next, the multiple threaded portion will be explained with reference to FIG. Here, a double thread screw is shown as an example. In the figure, 21 indicates the thread of the reference thread, and 22 indicates the thread of the double thread female thread. 23 indicates the thread pitch p, and 24 indicates the pitch deviation Δpn between the reference thread and the double thread female thread. Reference numeral 25 indicates the starting point for cutting the reference thread, and 26 indicates the starting point for cutting the double thread female thread. 27 indicates the deviation between the reference thread and the starting point of the double thread female thread.

In such a situation, when cutting a double thread thread, first, the starting point 25 is used as the starting point for thread cutting, waits for a single rotation signal from the spindle rotation encoder, and synchronizes with that signal to cut the thread 21 of the reference thread.
Cut. Next, a position 26 shifted by p/2 (p is the pitch of the screw) from the starting point 25 of the reference screw.
If you use this as the starting point for a double thread female thread and wait for a single rotation signal from the spindle rotation encoder and start cutting in synchronization with that signal, you can cut the correct double thread thread. In addition, when machining a 3-thread thread, a thread whose starting point is a position shifted by p/3 from the starting point 25 of the reference thread mentioned above and a thread whose starting point is a position shifted by 2p/3 are machined. By doing so, a triple thread thread can be formed. In this way, when cutting an n-thread thread, add n-1 threads shifted from the starting point of the reference thread by p/n ~ (n-1)/np to the reference thread. An n-thread thread can be formed.

By the way, conventionally, a programmer calculates the incomplete thread portion, and this calculation formula is complicated, so the calculation takes time and there is a possibility that a calculation error may occur. Furthermore, even if the calculations were performed correctly, a program had to be created based on the calculation results, which required a lot of time and effort. In addition, when forming a multi-thread thread, it is necessary to calculate the deviation between the standard thread and the multi-thread thread, and in the case of an n-thread thread, in addition to the standard thread program, n-1 programs are created. This required the troublesome effort of inputting data into a numerical control device.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it automatically calculates the length of the incomplete thread part and the pitch deviation of the n-thread thread with respect to the reference thread, and incorporates the results. The purpose of this invention is to provide a numerical control device that has a function to automatically correct a machining program.

Hereinafter, based on FIG. 4, a procedure for cutting multiple threads without incomplete threads will be explained according to an embodiment of the present invention. First, in step (31), a programmer creates a program from a machining drawing having a desired machining shape. Next, in step (32), the machining program created in step (31) is input into the numerical control device. Next, in step (33), the numerical control device calculates the incomplete thread length and the pitch deviation of the multi-thread thread with respect to the reference thread based on the machining program input in step (32).
Next, in step (34), the numerical control device corrects the length of the incomplete thread part based on the calculation result of step (33) in the first input program.
Further, the program that has undergone this correction is set as a reference program, and a program is created in which the starting point is shifted by the amount of shift of the multi-thread screw calculated with respect to this reference program. Thereafter, in step (35), the numerical control device sequentially issues commands based on the program created in step (34), and the machine tool performs thread cutting according to these commands.

Conventional multi-start thread cutting without incomplete threads relies on manual steps (1) to (6) in Figure 1, which takes time to create the final program from the drawing and is prone to human errors. There were many factors that caused this. In this example, a human performs steps (31) and (32) in Fig. 4, and then the numerical control device calculates the length of the incomplete thread and the pitch deviation of the multi-thread thread. This reduces programming time and eliminates manual errors.

Next, the processing procedure of the embodiment shown in FIG.
This will be explained in detail using figures. This Figure 5 shows the formation of a double thread without an incomplete thread.
41 is the coordinate of the thread cutting starting point given by the program, 42 is the workpiece, 43 is the coordinate axis of the program,
44 is the current position of the tool bit, 45 is the corrected starting point for thread cutting of the reference thread, 46 is the calculated correction amount, 47 is the thread cutting tool, 48 is the coordinates of the programmed thread cutting end point, and 49 is the second thread. The thread cutting start point coordinates of the thread, 50, are the pitch deviation amount of the double thread female thread with respect to the reference thread.

Here, when the incomplete thread length calculation program is started by the processing sequence of the numerical control device, the thread pitch F and spindle rotation speed S commanded by the thread cutting program are set in advance to the parameters of the numerical control device. _t1 is calculated from the smoothing circuit gain K _S , position loop gain K _P , pitch error rate a, and formula [B]. Once t ₁ is calculated, the length δ ₁ of the incompletely threaded portion is then calculated using the above formula [A]. This completes the incomplete thread length calculation program. Next, the processing sequence of the numerical controller starts a correction program for the starting position. When the correction program is started, δ ₁ calculated by the program is added to the Z coordinate of the thread cutting starting point given by the program,
The result is reset in the memory of the numerical control device as a new thread cutting starting point, and the program ends. Next, the processing sequence of the numerical control device starts a multi-thread thread pitch processing program. When this program is started, the pitch deviation amount △p ₂ of a multi-thread screw (in this example, a two-thread female screw) with respect to the standard thread is calculated, and added to the coordinates of the thread cutting start point reset in the program, and the result is is set in another memory as the starting point for threading a double thread female thread, and this program ends.

After completing the above data preprocessing program,
The numerical control device performs interpolation processing from the current position 44 to the reset position 45, and outputs a movement command to the byte 47 to the position 45. Part-time job 47
When it reaches position 45, it pauses there,
Wait for one rotation pulse of the spindle rotation encoder, start thread cutting in synchronization with this one rotation pulse,
A thread with no incomplete threads is machined. After machining the reference thread as described above, the numerical control device uses the starting point 49 for thread cutting of the double thread female thread set in the memory.
A command to move the cutting tool 47 is output. Part-time job 47
When the machine reaches position 49, it pauses there, waits for one rotation pulse of the spindle rotation encoder, and starts thread cutting in synchronization with this one rotation pulse, thereby machining a double thread thread without incomplete threads. Incidentally, through similar processing, thread cutting of a multi-thread thread without incomplete threads can be automatically realized using a numerical control device.

As described above, this numerical control device calculates the length of the incomplete thread and the pitch deviation of the multi-thread thread, and thread cutting is performed based on the calculation results, so the turret acceleration time constant Calculation of the length of an incomplete thread due to this, correction (or creation) of a standard thread machining program based on this calculation result, calculation of pitch deviation between the standard thread and multi-thread thread, and calculation of the length of a standard thread machining program based on this calculation result. This eliminates the need for the programmer to perform work such as creating a thread thread program, thereby making it possible to perform thread cutting very easily and without mistakes.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the conventional thread cutting procedure, Figure 2 is a diagram to explain an incomplete thread, Figure 3 is a diagram to explain a multi-thread thread, and Figure 4 is a diagram to explain the thread cutting process of this invention. A diagram showing one embodiment, FIG. 5 is a detailed explanatory diagram of FIG. 4. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

Claims (1)

[Claims] 1. A multithread thread cutting program, a calculation program that calculates the length of an incomplete thread due to the turret acceleration time constant at the start of standard thread cutting based on data commanded by this processing program, and the calculation results of this calculation program. A correction program that corrects the reference thread cutting starting point given in the above machining program based on the above processing program and resetting a new reference thread cutting starting point; A numerical control device comprising a multi-thread pitch processing program that shifts from the standard thread cutting starting point reset by.