KR101316333B1 - Method for controlling tool shifting velocity in screw manufacturing using nc machine - Google Patents

Abstract

A method of controlling the feed rate of the tool (T) in threading using a numerical control device is disclosed. The method according to the invention comprises the steps of (a) obtaining the absolute positions (0, 1, 2, ... N-1) of the workpiece (W), and (b) the workpiece (W) being the absolute position (0, Checking whether the reference point (0) has passed from 1, 2 ... N-1), and (c) if the workpiece (W) has passed the reference point (0), the workpiece (W) exceeds the origin. Measuring the amount E rotated with (d), (d) obtaining a feed axis (Z-axis) distance D ₂ corresponding to the excess amount E of the workpiece W, and (e) To the target feed rate (V) of the tool, the distance (D ₁ ) between the feed time (B) and the cutting time (C) of the tool (T), and the excess amount of rotation (E) of the workpiece (W) corresponding feed shaft (Z axis) from the (D ₂₎ transfer acceleration (a ') of the tool (T) comprises: obtaining a from the following equation ^{a' = V 2/2 (} D 1 -D ₂ ) characterized in that it comprises a.

 Numerical control unit, threading, feedrate, control

Description

TECHNICAL FOR CONTROLLING TOOL SHIFTING VELOCITY IN SCREW MANUFACTURING USING NC MACHINE}

The present invention relates to a thread processing using a numerical control device, and more particularly, in a thread processing using a numerical control device, by controlling the feed acceleration of the tool to equalize the point where the tool cuts the screw, high precision thread processing A tool feed rate control method is provided.

In the numerical control apparatus, as shown in FIG. 1A, the tool T is rotated in a direction (Z-axis) parallel to the rotation axis of the workpiece W while the workpiece W is rotated at a constant rotation speed S as shown in FIG. 1A. From the feed point B to the cutting point C, the tool accelerates the feed to the target feed rate V of the tool. Then, when the workpiece W reaches the cutting point B as shown in FIG. The cutting of the workpiece W proceeds by uniformly feeding the tool T at the feed speed V. FIG.

On the other hand, in order to obtain a smooth surface at the time of threading, the above-mentioned processing process (finishing) is performed in multiple times. Therefore, the position which contacts the tool T workpiece | work W at the cutting time point C needs to be kept constant every time.

For this purpose, as shown in FIGS. 2A to 2C, the absolute number of workpieces is generated by generating a predetermined number N of signals per revolution of the workpiece by using an encoder directly connected to the rotating workpiece W side. Continue reading the position values (0 to N-1) and feed the tool (T) when it has passed the workpiece (W) reference point (zero point) as shown in Fig. 2a (i.e. when the encoder is zero-crossed). Accelerated transfer is carried out at the predetermined acceleration A from the time point B to the cutting time point C. FIG.

The determination of whether the encoder has crossed zero is performed by checking the current absolute position value P _n of the workpiece minus the previous absolute position value P _{N -1} (D = P _N -P _{N -1} ). For example, when the work W rotates in the counterclockwise direction S as shown in FIGS. 2A to 2C, the absolute position values of the work W are about 1, 2, ..., N-1 in order of 0-1. It will increase sequentially. In this process, the absolute value of D value (| D |) will be a small number around one. However, at the moment when the workpiece passes the reference point (point 0), which is the point at which the workpiece rotates once, that is, the moment when the workpiece moves from Fig. 2C (absolute position = N-1) to Fig. 2A (absolute position = 0), the absolute value of the D value Since it will increase rapidly (D = N-0 = N), it is determined that the instant (| D |> a) at which the absolute value of the D value sharply increases above the reference value (a) as the zero crossing point.

According to one embodiment, the reference value (a) for determining whether to cross zero can be set to half of the total number of pulses (N) of the encoder per revolution of the workpiece (W) (ie | D |> a = N / 2 Is determined as a zero crossing time point), the reference value a is not limited to N / 2 and can be appropriately set.

The tool transfer process in the conventional thread machining described above is shown in FIG. That is, the absolute position (P ₁ , P ₂ , P _N ) of the workpiece is counted sequentially using the encoder while rotating the workpiece at a constant speed (S) (S 10), the workpiece (W) is a reference point (0 point) When passing through (S20), the predetermined acceleration (A = V) to reach the target feed rate (V) from the stationary state of the tool (T) over the distance (D ₁ ) of the feed time (B) to the cutting time (C). ² / 2D ₁ ) is accelerated transfer (S 30), and when the tool T reaches the cutting time (C), the cutting is started while feeding the tool (T) at the constant speed (S 40).

On the other hand, due to excessive rotation of the workpiece due to inertia, etc., the point where the zero cross point is judged is often actually exceeded the reference point (zero point). That is, after the absolute position measurement of the workpiece at the time point of FIG. 2C (absolute position = N-1), the absolute position measurement of the next work piece passes the zero point passing state of FIG. 2A, (absolute position = 1) When the point of arrival is reached, it may occur that it is determined whether or not it is a zero cross. Furthermore, when the rotation of the work W proceeds more excessively, when the absolute position of the work W reaches two or more (2, 3, ...) points after the zero cross, the time of determining the zero cross is determined. It also happens.

However, in the related art, the feed acceleration of the tool T is set irrespective of the absolute position of the actual work W after zero cross of the work W. That is, it is assumed that the absolute position of the blank W after zero cross is always zero. Thus, although the actual absolute position of the workpiece at the actual zero cross point of view varies, conventionally, the acceleration T is equal over the distance D1 from the feed point B to the cutting point C, even though the tool T is varied. = V ² / 2D1), the absolute position where the tool T is in contact with the workpiece W at the cutting point C is inevitably different, which causes a decrease in the precision of threading.

The present invention has been derived to solve this problem, the point that the tool and the workpiece is cut at the time of cutting, even if the absolute position value of the workpiece is different every time when the workpiece is determined to be zero cross when the machining in the numerical control device It is a technical subject to make it maintain the same.

In order to solve the above technical problem, the present invention is to compensate (A ') the feed acceleration of the tool (T') when the workpiece (W) is rotated more than the origin after passing through the origin (zero cross) of the workpiece (W) The position where the tool T meets at the cutting point with the workpiece W is always controlled. To this end, the amount of excess rotation E after the zero cross of the workpiece W is obtained, and the Z-axis equivalent distance D2 is calculated therefrom to obtain the corrected acceleration A '.

More specifically, the present invention is a screw processing performed by feeding the tool (T) in the direction parallel to the axis of rotation of the workpiece (W) while rotating the workpiece (W) about a predetermined axis of rotation (Z axis) using a numerical control device In the above, for reaching the tool (T) from the stationary state to the feed target speed (V) with respect to the distance (D ₁ ) from the transfer time (B) of the tool (T) to the cutting time (C), It is a method of controlling the feed speed of the tool T in the threading process using a numerical control apparatus.

The method according to the invention comprises the steps of (a) obtaining the absolute positions (0, 1, 2, ... N-1) of the workpiece (W), and (b) the workpiece (W) being the absolute position (0). Checking whether the reference point (0) has passed from 1, 2, ... N-1), and (c) if the workpiece (W) has passed the reference point (0), the workpiece (W) is the origin point. Measuring the amount of excess rotation (E) from (d) obtaining a feed axis (Z-axis) distance (D ₂ ) corresponding to the amount of excess rotation (E) of the workpiece (W), ( e) the target feed speed V of the tool, the distance D ₁ between the feed time B of the tool T and the cutting time C, and the amount of excess rotation E of the workpiece W; ), a feed shaft (Z axis) distance (D _2), the tool (T) traverse acceleration (a 's) to obtain the equation below step ^{a' = V 2/2 (} D 1 from the corresponding a - D _2), the It is characterized by including.

The present invention adjusts the feed acceleration of the tool (T) according to the amount by which the workpiece (W) has rotated beyond the origin after the workpiece (W) passing through the origin, the actual position after the origin of the workpiece (W) is different Even if the tool T always controls the position at which both the workpiece (W) and the contact point at the beginning of the cutting. This increases the precision of threading since the cutting always starts at the same point in the repeated finishing process during threading.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a specific description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 to 2 and 5 will be described in the tool feed speed control method according to the present invention. 5 is a flow chart illustrating a method for controlling the feed rate of a tool in accordance with the present invention.

The process of determining whether the absolute position of the workpiece W passes the reference point (origin), that is, whether zero cross has occurred (S 100 to S 200) and the tool feed process when the current position of the workpiece at zero cross point is zero ( S 300 to S 600) is the same as the conventional method.

That is, as shown in Figs. 1 and 2, the workpiece W is rotated at a constant speed S, and then divided into equal parts by a predetermined number N per one revolution of the workpiece W using the encoder. The absolute positions of P _{1 , ...} P _N are sequentially counted (0, 1, 2, ... N-1) (S 100).

Then, the present absolute position value (P _N ) of the workpiece is subtracted from the previous absolute position value (P _{N -1} ) (D = P _N -P _{N -1} ), so that the absolute value of D is the reference value (a = N / 2) or more (| P _N -P _{N -1} | = | D |> a = N / 2), it is determined that the workpiece W has passed through the origin (zero cross) (S 200).

If the workpiece W has passed through the origin, and then the current absolute position value P _N of the workpiece is zero (S 300, FIG. 2B), as in the prior art, the feed time B with the uncorrected circle acceleration A is ) And the tool T is accelerated to the distance D1 from the cutting point C to the cutting point C (S400). Then, the tool T is accelerated to the cutting point C at the original acceleration A to the cutting point C (S 500), and then cutting is performed while the tool is fed at the target feed rate V from the cutting point C ( S 600).

Where V [mm / min] is the target feed rate of the tool T, the pitch of the thread machined on the workpiece W (moving distance of the thread per revolution) is L [mm / speed], and the workpiece W Assuming that the rotational speed of the tool is S (the number of revolutions / minute) (see Fig. 1), the target feed rate V of the tool can be obtained by the following equation.

 V [mm / min] = L [mm / rpm] × S [rpm / min]

In addition, the circle acceleration A is an acceleration required for accelerating the tool T from the stop state (speed 0) to the target feed speed V over the distance D ₁ from the feed time B to the cutting time C. It can be obtained by the following equation.

A [mm / min ² ] = V ² [mm / min] / 2D ₁ [minute]

According to the present invention, when the current position of the workpiece after zero cross of the workpiece W has passed the origin, the tool T has reached the cutting point C by obtaining a correction acceleration A 'correcting the acceleration A. The feature is that the position where the tool T and the workpiece W are in contact at the same time is always the same.

In other words, when the workpiece current absolute position value P _N after the workpiece W passes the origin is not zero, that is, when the workpiece W is rotated more than the origin, the workpiece W is After finding the amount E rotated beyond the origin, the Z-axis (tool feed direction) distance D2 corresponding to the amount of excess rotation E is calculated (S 700, FIG. 2A).

Here, the amount of excess rotation E is the number of absolute positions where the workpiece W has moved beyond the origin, and the unit will be [number of pulses], and the Z axis distance D2 corresponding to the amount of excess rotation E is the workpiece It means the Z-axis displacement of the thread caused by (W) rotating more than the origin.

Excess of workpiece Amount of rotation (E) calculation

The amount E by which the work W is rotated more than the origin must be determined differently according to the rotation direction of the work W.

When the workpiece is rotated counterclockwise as shown in the embodiment of Fig. 2, since the absolute position immediately after the workpiece W passes the origin will be 1, 2, the excess rotation amount E is immediately after the origin passage. It is equal to the absolute position value P _{N of} (Equation 3). For example, in FIG. 4A, the excess rotation amount E is an absolute position value P _N. = 1), equal to 1).

E = P _N (If the workpiece rotates counterclockwise)

On the other hand, if the workpiece W is rotated in the clockwise direction, the absolute position P _N immediately after the workpiece W passes the origin will be N-1, N-2, ..., so that the excess rotation amount (E) is the total number of absolute positions (N)-an absolute position value P _N immediately after the origin pass (Equation 4). For example, in the case of FIG. 4B, the amount E rotated in excess is the absolute position value P _N in the total number of absolute positions N. FIG. = 1 minus N-1).

E = N-P _N (If the workpiece rotates clockwise)

Excess Rotation amount (E)  Corresponding Z-axis distance ( D2 ) Calculation

Next, the Z axis distance D2 corresponding to the excess rotation amount E of the workpiece W should be calculated.

The pitch of the thread processed on the work W (the moving distance of the thread per revolution) is L [mm / speed], and the excess amount of rotation of the work W is E [the number of pulses], and the work W 1 Assuming the absolute number of revolutions per revolution is N [pulse / revolution] (see FIG. 1), the Z-axis (tool feed direction) feed of the workpiece W corresponding to the excess amount of rotation E of the workpiece W The distance D ₂ can be found as follows.

D ₂ [mm] = L [mm / speed] × E [pulse] × 1 / N [pulse / speed]

Compensated tool feed acceleration ( A ' ) Calculation

After calculating the Z-axis distance D2 corresponding to the excess rotation amount E of the workpiece W, the correction acceleration necessary for the transfer of the tool T from the feed point B to the cutting point C is shown. (A ') is obtained by the following equation (S 900).

A '[mm / min ² ] = V ² [mm / min] / 2 (D ₁ -D ₂ ) [min]

Comparing the correction acceleration (A ') with the correction power acceleration (A = V ² / 2D ₁ ) according to the equation 2 it can be seen that the correction acceleration (A') is larger than the value of the original acceleration (A). have.

The meaning of the acceleration correction will be described with reference to FIGS. 6A and 6B. It is to be understood that FIG. 6B is a rather exaggerated graphical representation of distance D ₂ for ease of understanding.

That is, when the workpiece W is positioned at the origin after zero cross, the acceleration A required for accelerating the tool T to the target feed rate V from the feed time B to the cutting time C 6A), when there is an amount E in which the workpiece W is rotated beyond the origin, the tool T is accelerated faster from the feed point B to the cutting point C. Means that the tool T should be accelerated (see FIG. 6B). The distance obtained by converting the excess rotation amount E into the Z-axis distance is D ₂ , and the corrected acceleration A ′ is changed from the correction power acceleration A using D ₂ .

According to this configuration, the present invention adjusts the feed acceleration of the tool T according to the amount by which the workpiece W is rotated beyond the origin after the workpiece W passes through the origin, and then after the workpiece W passes the origin. Even if the actual position is different, the tool T always controls the position at which the workpiece W contacts the workpiece W at the point where the cutting starts.

Although specific embodiments of the present invention have been described above, it should be understood that the spirit and scope of the present invention is not limited to these specific embodiments, but various modifications and variations may be made without departing from the scope of the present invention. It will be understood by those of ordinary skill in the art to which the present invention belongs.

Therefore, it should be understood that the above-described embodiments are provided so that those skilled in the art can fully understand the scope of the present invention. Therefore, it should be understood that the embodiments are to be considered in all respects as illustrative and not restrictive, The invention is only defined by the scope of the claims.

1 is a schematic view showing a threading process.

2 is a schematic view showing a process of absolute position measurement of a workpiece.

3 is a flow chart showing a tool transfer process during threading according to the prior art.

4 is a schematic view for explaining the amount of excess rotation of the workpiece.

5 is a flow chart showing a tool transfer process during threading according to the present invention.

6 is a view for explaining the meaning of the tool feed acceleration correction of the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS OF THE DRAWINGS

T: Tool W: Workpiece

S: Rotational speed of the workpiece V: Target feedrate of the tool

A: circle acceleration of the tool A ': compensation acceleration of the tool

L: Thread pitch E: Excess rotation of the workpiece

D ₁ : Traversing distance of the tool from the feed point to the cutting point

D ₂ : Z-axis distance converted from the amount of excess rotation of the workpiece

Claims (1)

In the threading process performed by conveying the tool T in the direction parallel to the rotation axis of the workpiece W while rotating the workpiece W about a predetermined rotation axis (Z axis) using a numerical control device, In the threading process for reaching the tool (T) from the stop state to the feed target speed (V) with respect to the distance (D ₁ ) from the feed time (B) of the tool (T) to the cutting time (C) As a method of controlling the feed rate of the tool (T), (a) obtaining the absolute positions (0, 1, 2, ... N-1) of the workpiece (W), (b) checking whether the workpiece W has passed the reference point 0 from the absolute positions (0, 1, 2, ... N-1), (c) when the workpiece W passes the reference point 0, measuring the amount E by which the workpiece W is rotated more than the origin; (d) obtaining a feed axis (Z-axis) distance D ₂ corresponding to the excess rotation amount E of the workpiece W; (e) the target feed speed V of the tool, the distance D ₁ between the feed time B of the tool T and the cutting time C, and the amount of excess rotation of the work piece W; Obtaining the feed acceleration A 'of the tool T from the feed axis (Z axis) distance D ₂ corresponding to E) by the following equation ^{A '= V 2/2 (} D 1 -D ₂ ) Thread processing control method of the numerical control device comprising a.

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