JPH064194B2 - Welding method by arc welding robot - Google Patents

Description

The present invention relates to a welding method by an arc welding robot using a consumable electrode and applying an automatic oscillating width control method.

In arc welding using a consumable electrode (wire), the change in groove spacing from the change in the sum of the arc length during welding and the protruding length of the wire (hereinafter abbreviated as "chip-workpiece distance") due to oscillating No method has been found yet for detecting and automatically controlling the oscillation width accordingly.

In view of the above situation, the present invention, in arc welding using a wire, calculates welding conditions during welding without mounting a tangible detector in the vicinity of the welding torch, and changes the oscillating width according to changes in the groove spacing. It is an object to provide an arc welding robot that can be automatically controlled. The present invention that achieves such an object is easy to detect, and the welding condition that is normally used is processed by an electrical arithmetic circuit to calculate the sum of the wire protrusion length and the arc length (chip-workpiece distance). Then, by oscillating the torch, the change in groove spacing is detected from the change in this sum (distance between chip and work piece), and the groove width direction and the direction perpendicular to the groove width are detected according to the size of the groove interval. The gist of the invention is to automatically control the oscillating width by two-dimensional control and obtain a sound welded joint without welding defects.

Embodiments of the present invention will be described in detail below with reference to the drawings. The arithmetic processing of the embodiment according to the present invention can of course be performed by an analog arithmetic unit, but this embodiment shows the case of processing by a digital computer.

First, the configuration will be described. In FIG. 1 and FIG. 2, 1 is a welding torch for consumable electrodes, 2 and 3 are rotating mechanism parts for giving a rotating and rotating motion to the welding torch 1, a torch tilt shaft 2 and a wrist rotating shaft 3. .

Reference numeral 4 denotes a Z-direction moving shaft that holds the torch tilt shaft 2 and the wrist turning shaft 3 and gives them a motion in the Z direction.

Reference numeral 5 is a Y-direction moving shaft that holds the Z-direction moving shaft 4 and gives motion to the Y-direction.

Reference numeral 6 denotes an X-direction moving shaft that holds the Y-direction moving shaft 5 and gives motion to the X-direction.

7 is a control command from the remote control panel 10 and is an electric drive device 8
Is a control device for controlling the movement of the torch tilt axis 2, the wrist turning axis 3, the Z-direction moving axis 4, the Y-direction moving axis 5, and the X-direction moving axis 6.

Further, the control device 7 acts on the arc welding machine 9 according to a control command from the remote control panel 10 to perform welding conditions such as welding current (I: Ia, Ie), welding voltage (V), wire feeding speed (v). Can be controlled. Further, in the control device 7, the torch position is controlled to automatically change the oscillating width according to the change in the groove interval of the welding line, and the welding speed is automatically changed in accordance with the calculated groove interval. It also has a built-in calculation function. The above control can be either manual or by a pre-programmed procedure, the so-called automatic.

9 is welding for generating the arc 14 between the wire 13 and the material 16 to be welded and supplying the electric energy required to obtain the weld metal 17, 45 is welding conditions such as welding voltage or welding current The setter 11, which is a shield nozzle, shields the atmosphere of the arc 14 and the weld metal 17 from the atmosphere together with the shield gas 15.

Reference numeral 12 is a chip for feeding power to the wire, 18 is a backing metal, and 19a and 19b are rollers for feeding the coiled wire 13 into the welding torch 1, and a feeding roller 19
a is mechanically coupled to the motor 21, and the speed of the motor 21 is controlled by the drive control device 22 so that the welding current or the welding voltage is adjusted together with the welding condition setter 45.

Reference numeral 20 is a power feeding portion to the welding torch 1 of the arc welding machine 9, 23 is a welding current value detector such as a shunt, and 24 is a voltage divider or the like for detecting a voltage value between the chip 12 and the material 16 to be welded. The voltage value detector 25 is mechanically fed to the roller 19b, and the rotation amount detector 26 for detecting the wire feeding speed (v) of an encoder or the like is a welding robot controller 7 To toss 1 oscillating position signal ((w) in X direction and (w _y ) in Y direction)
, 27 is an amplifier for setting the signal from the rotation amount detector 25 to an appropriate level, 28 is an amplifier for setting the signal from the voltage value detector 24 to an appropriate level, 29 is a current value An amplifier for generating a signal proportional to the average value of the welding current from the signal of the detector 23, 30 is an amplifier for generating a signal proportional to the effective value of the welding current from the signal of the current value detector 23, 31 the distance from the object to be welded 16 of the welding torch 1, i.e., chip - welded object distance _{L (= L E + L a} ) setter for setting, the 32,33,34,35,36,37 , 26, 27,
A for converting 28, 29, 30, 31 analog signals into digital signals and inputting them to the digital computer 38
An A / D (analog / digital) converter 39 is a D / A (digital / analog) converter that converts the digital signal from the computer 38 into an analog signal, and sends it to the controller 7 that controls the oscillating rate of the welding robot. Output through the amplifier 42. The signals are an oscillating width control signal and an oscillating speed control signal.

Reference numeral 40 is a D / A that converts the digital signal from the computer 38 into an analog signal, and outputs it to the control device 7 that controls the welding line copying through the amplifier 43. The signal is a welding line copy signal.

Reference numeral 41 is a D / A that converts the digital signal from the computer 38 into an analog signal, and outputs it to the control device 7 that controls the torch height through the amplifier 44. That signal is the torch height control signal.

Next, the operation will be described.

(A) The average value Ia of the welding current is obtained by the current detector 23 and the amplifier 29, and the effective value Ie of the welding current is obtained by the current detector 23 and the amplifier 30. Further, the voltage V between the chip 12 and the workpiece 16 is obtained by the voltage detector 24 and the amplifier 28. Further, the wire feed speed v is detected by the rotation amount detector 25 and the amplifier 27.

(B) These analog quantities are A / D converters 35, 36,
It is converted into a digital amount by 34 and 33 and added to the digital computer 38.

(C) Here, the symbols are defined as follows.

Ia: Mean value of the welding current, Ie: effective value of the welding current, v: Paiya feed speed, V: voltage between chip 12 and the material to be welded 16, L _E: from the tip of chip 12 to the arc 14 Wire 13
Length, so-called wire protruding length, L _A : distance from the tip of the wire 13 to the weld metal 17, so-called arc length, L: sum of L _E and L _A , that is, from the tip of the chip 12 to the weld metal 17 , V _E : voltage drop caused by welding currents Ia and Ie on the wire protrusion, V _A : voltage obtained by subtracting V _E from V, that is, arc voltage, and the above values are approximate. Has the following relationship.

(Where _k 1, _{k 2} is a constant _{V E = f 2 (I a} , v, L E) = k 3 · I a k4 · L E k5 · V k6 ... second equation (where _{k 3, k 4, k 5, k 6} are _{constants) V A = V-V E} ... third expression (Where _{k 7, k 8, k 9} , k 10 is a _{constant) L = L E + L A} ... first equation Equation 5 from Reference 1, and the fourth equation is determined from the reference 2. The specific form of the second equation can be found by experiments. Equations 3 and 5 are self-explanatory from FIG.

References (1) Japan Welding Society Welding Method Committee July 1980 Research on current controlled arc welding (2) Welding arc phenomenon Supplementary edition Kobo Ando Kohei et al. (D) Therefore, the relationship of the first equation is calculated by digital calculation. When the welding currents Ia and Ie and the wire feeding speed v are applied to the machine 38 and programmed, the wire protrusion length L _E is obtained.

(E) When the relationship of the second equation is programmed in the digital computer 38 and the welding current I _a , the wire feeding speed v, and the wire protrusion length L _E obtained in (d) above are given, the wire protrusion portion is given. The voltage drop of V _E is required.

(F) The relationship of the third equation is programmed in the digital computer 38, and the voltage between the chip 12 and the work piece 16 and the voltage drop V _E of the wire protrusion obtained in (e) above are given. And arc voltage V _A is required.

(G) The arc length L _A can be obtained by programming the relationship of the equation 4 in the digital computer 38 and applying the welding current I _a and the arc voltage V _A obtained in the above (f).

(H) If the relationship of the fifth formula is programmed in the digital computer 38, from the sum of the wire protrusion length L _E obtained in the above (d) and the arc length L _A obtained in the above (g) The distance L between the chip 12 and the object 16 to be welded is obtained.

(I) As described above, when the welding currents Ia and Ie, the wire feeding speed v, and the voltage V between the chip 12 and the workpiece 16 are given as explanatory variables, the chip 12 is calculated from the first to fifth formulas. The distance L to the workpiece 16 is obtained as the objective variable.

(N) FIG. 3 is based on the oscillating position signal (timing at which the amplitude becomes maximum and timing at which the amplitude becomes zero) from the welding robot controller 7, that is, based on the timing at which the oscillating amplitude crosses zero. Timings when the welding currents Ia and Ie, the wire feeding speed v, and the chip-to-weld object voltage V are sampled and L is calculated at every constant time Δt (this is equivalent to the oscillation amplitude). Because the oscillation rate is constant and the sampling interval is also constant.)
An example of the relationship with the distance L between the objects to be welded is shown when welding is performed within the V-shaped butt groove formed by the object to be welded 16 as shown in FIG. In this example, sampling of the data Ia, Ie, v, and V is performed only at the maximum forward path from the zero crossing of the amplitude and not at the return path.

When oscillating welding is performed in the groove in this way, a graph of the oscillating position and the corresponding chip-weld object distance L can be obtained.

(L) FIG. 4 shows a state in which the groove formed by the work piece 16 is changed, but FIGS. 5 and 6 show that oscillate welding is performed with two grooves having different groove intervals. FIG. 4 is a schematic diagram showing the relationship between the oscillating width w and the distance L between the chip and the object to be welded at the time of hanging.

(W) FIG. 4 shows a state in which the groove interval of the joint formed by the work piece 16 is changed, but FIGS. 5 and 6 are different in the position of the groove shown in FIG. The relationship between the oscillating width w in the X direction and the distance L between the chip and the object to be welded and the trajectories 46 and 47 of the tip of the chip are shown when welding is performed while oscillating two-dimensionally in two sections. FIG. 5 shows the case where the groove interval is small and FIG. 6 shows the case where the groove interval is large. In both cases, the two-dimensional oscillating locus (46, 4) is used.
(Corresponding to 7) is selected close to the groove cross-sectional shape, the chip-weld object distance L becomes flat in the relationship between the oscillating width w and the chip-weld object distance L.

(W) Fig. 7. And FIG. 8 pays attention to the relationship between w and L in FIGS. 5 and 6 and the loci 46 and 47 of the tip of the chip. When the oscillating height in the Y direction is w _y ,
(L-w _y ) with respect to the oscillating width w in the direction. Here, w ₁ and w ₃ is the X direction Otsushireto width, w ₂ and w ₄ is the width of w when a _{w y = 0, w y =} 0
Be symmetrical with respect to.

(F) FIGS. 9 and 10 show the w and L ′ ¹ ((L ′ ¹ = L-
It is an explanatory diagram that the oscillating width w can be controlled by focusing on w _y ).

Here, L _e ′ is when the oscillating width w in the X direction is small,
That is, it is the value of L ′ near the groove center. γ is a parameter provided to eliminate this influence, that is, a variation removal parameter, because the value of L ′ obtained by calculation causes variation due to an error due to disturbance. U is a parameter provided for controlling the oscillation amplitude, that is, an oscillation amplitude control parameter.

(Y) FIG. 9 is an explanatory diagram showing that the appropriate oscillating width w in the X direction changes depending on the set value of the oscillating amplitude control parameter U when the groove shape is unchanged.

Here, the variation removal parameter γ and the oscillating amplitude control parameter U are set to the digital computer 38 as appropriate values which have been obtained by experiments in advance.

(T) When welding is started, the zero timing of the oscillating amplitude in the X direction is detected, and if detected, the data Ia, Ie,
V and v are sampled and L is calculated according to the first to fifth expressions. When the next tumbling time comes, this process of fetching data again and calculating L is repeated several times to obtain the average value. The interval of sambling is shown in Fig. 3 △
t.

(L) After that, the data Ia, Ie, V, v at that time are calculated every Δt.
Based on the above equation, L is calculated and attention is paid to the magnitude relation between L'and {L ₀ '-(γ + U)}. If [(L ′) ≧ {L ₀ ′ − (γ +
U)}], further oscillate in the same direction. However, if the condition of [(L ′) <{L ₀ ′ − (γ + U)}] is satisfied several times in succession, the oscillating direction is reversed.

(So) Next, the timing at which the oscillating amplitude in the X direction in the opposite direction to the oscillating direction described in (Ta) is zero is detected, and then the sequence described in (ta) and (re) is repeated.

(T) In this way, the oscillating operation is repeated with an appropriate size according to the parameter conditions set by γ and U.

(D) By the way, Fig. 9 shows U when the groove shape is unchanged.
Shows U ₁ and U ₂ (U ₁ <U ₂ ).
In order to satisfy the condition of [(L ′) <{L ₀ ′ − (γ + U)}], it is necessary to oscillate U _{2 in} the X direction by a larger amount than in the case of U ₁ . Is self-explanatory. That is, the oscillating width w in the X direction can be controlled by adjusting U. If U ₁ <U _2, then w ₅ <w ₆ . Here, w ₅ is the oscillating width in the X direction corresponding to U ₁ , and w ₆ is the oscillating width in the X direction corresponding to U ₂ .

The control of the oscillating pattern is to control the oscillating widths w ₂ and w ₄ in the X direction in FIGS. 7 and 8, and w _ymax and (w ₂ −w ₁ ), (w ₄ −w ₃ ) is constant. Where w _ymax is the maximum value of w _y .

(D) FIG. 10 is an explanatory diagram that the oscillating width in the X direction can be controlled to an appropriate value by keeping U constant when the groove spacing changes during welding.

(A) The principle of operation is the same as the above (ta) to (so), but in the case of FIG. 10, U is set to a constant value U ₃ .
When U is constant when the groove intervals are different, the oscillating width w ₇ when the groove interval is large (shown by the solid line) is the oscillating width when the groove interval is small (shown by the dotted line).
It is obvious from FIG. 10 that it becomes larger than w ₈ . That is, when an appropriate value is selected and set for U, the oscillating width w in the X direction is automatically controlled by the change in groove interval.

(M) As shown in FIG. 9, the oscillating width w in the X direction can be controlled by the set value of U when the groove spacing is unchanged. Further, it is explained that by setting an appropriate U when the groove spacing shown in FIG. 10 is changing, the oscillating width w in the X direction is changed, and control can be performed to adapt to the change in the groove spacing. did.

(C) Next, (L '= L- in FIG. 7 and FIG.
The average value L _m ′ of one cycle of the X-direction oscillating shown in FIG. 3 for w _y ) can be calculated as follows.

(ヰ) Therefore, the set value Ld of the setter 31 and the L of the above (c)
'by comparing the, if L _{m' m} becomes 'outputs a signal proportional to (-Ld L _m> Ld if the control unit 7 for controlling the torch height of the welding robot L _m)' = Ld Up to controlling each axis 2, 3, 4, 5, 6 of the welding robot. On the contrary, if L _m ′ <Ld, the axes 2, 3, 4, 5 and 6 of the welding robot are controlled until L _m ′ = Ld as described above.

(B) Due to the above (m) and (c), L _m ′ can always be held at the value of L d.

(E) In addition, {L '(= L- in FIG. 7 and FIG.
w _y )} in the oscillating pattern shown in FIG. 3, the sum on the left side of the vertical axis L ′ And sum on the right The difference ΔD is However, when ΔD ≠ 0, it means that the central axis of the oscillate and the central axis of the groove formed by the workpiece 16 do not match. That is, if ΔD> 0, the oscillating center axis exists on the right side of the groove center axis, and conversely, ΔD <
If it is 0, the oscillate center axis exists on the left side of the groove center axis.

(H) Therefore, if ΔD> 0, a signal proportional to ΔD is output to the control device 7 that controls the welding line tracing of the welding robot.
Each axis of welding robot 2, 3, 4, until ΔD = 0
Control 5 and 6. On the contrary, if ΔD <0, each axis of the welding robot 2, 3, 4, until ΔD = 0, as described above.
Control 5 and 6.

(Y) By the above (M) and (K), the center position of the oscillate can always be held at the center position of the groove.

(B) As described above, according to the present embodiment, when the groove spacing changes, the oscillating width adapts to it, and even if the distance between the torch 1 and the workpiece 16 changes, the torch height L is always maintained. Can be maintained at the set value Ld. Furthermore, although it was described that the welding line can be automatically followed even if it deviates from the set position, the wire feeding speed v is constant (usually in this state) and the welding speed S is constant when the groove interval changes. If so, the bead height changes.

Therefore, since the digital computer 38 can calculate the oscillating widths w ₅ , w ₆ , w ₇ , and w ₈ as shown in FIGS. 9 and 10, the change in the oscillating width w can be calculated. Feed back to control the moving speed of the torch 1 so that the bead height becomes uniform.

(F) All the operations described above are controlled by the program of the computer 38.

According to the present invention as specifically described in connection with the above embodiments, there is no defect because the oscillating width can be automatically adapted to the variation of the groove spacing and the welding line can be automatically followed. Welding can be realized and the reliability of the welding robot can be improved.

[Brief description of drawings]

1 is a block diagram showing an arc welding robot according to the present invention, FIG. 2 is a block diagram showing a welding circuit and an arithmetic processing mechanism of an embodiment according to the present invention, and FIG. 3 is an oscillating pattern and a chip-weld. FIG. 4 is a characteristic view showing the relationship between the distances L between objects, FIG. 4 is a perspective view showing an object to be welded, and FIG. 5 is VV of FIG.
Explanatory diagram showing the change pattern of the distance L between the chip and the work piece with respect to the oscillating width w when oscillating in the groove in the cross section, and FIG. 6 is the case of oscillating in the groove in the VI-VI cross section of FIG. Of the chip-to-weld object distance L with respect to the oscillating width w of Fig. 7, Fig. 7 and Fig. 8 are chips in consideration of the oscillating height w _y in the plate thickness direction when oscillating two-dimensionally.
Explanatory drawing showing the relationship between the distance L between the objects to be welded and the oscillating width w, and FIGS. 9 and 10 are explanatory views showing the relationship between the graphs of FIGS. 7 and 8 and the groove cross-sectional view. In the figure, 1 is a welding torch, 2 is a bead tilt axis, 3 is a wrist turning axis, 4, 5 and 6 are moving axes, 7 is a control device, 8 is an electric drive device, 9 is an arc welding machine, and 13 is a wire. , 16 is a welded object, 23 is a welding current detector, 24 is a voltage value detector, 25 is a rotation amount detector, 31 is a chip-weld object distance setter, 38 is a digital computer, and 45 is a welding condition. It is a setting device.

Claims (1)

[Claims] 1. A moving mechanism capable of moving a welding torch to a desired point in a three-dimensional space, an attitude control mechanism for causing the welding torch to have a desired shape, and a control device for controlling required welding condition specifications. In a welding method by an arc welding robot, which is performed while oscillating the welding torch using a consumable electrode, that is, a wire, an average value I _a and an effective value I _{e of a} welding current, a wire feeding speed v, a tip and The wire protrusion length L _E and the arc length are detected by detecting the voltage V between the welding object and calculating the average value I _a , the effective value I _{e of} the welding current, the wire feeding speed v and the voltage V. L _a sum L _{E +} L _a or chips of - seeking weld object distance, the chip according Otsushireto of the welding torch - the welding from a change pattern of the welded object distance L _{a +} L _E Recognize the deviation between the center position of the torch oscillate and the center position of the joint composed of the material to be welded and the groove surface, and always keep the relative position between the oscillate center position and the center position of the joint as specified. The position of the welding torch is controlled by two-dimensional control in the groove width direction and in the direction perpendicular to the groove width so that the arc point automatically follows the welding line, and further, the oscillate width according to the change in groove interval. And a welding speed S is controlled so that a constant bead height can always be obtained even if the groove interval changes, and a welding method by an arc welding robot.