JP2008290120A - Electrode tip dressing device - Google Patents

Abstract

An electrode tip dressing device capable of changing dressing conditions in accordance with the wear amount of the electrode tip is provided.
In an electrode tip dressing apparatus for dressing an electrode tip when the tip of the electrode tip attached to the welding gun is worn, the work of welding performed by the welding gun (for example, the number of welding points, the electrode) According to the tip wear amount W), the dressing of the worn electrode tip is controlled using the dressing time T (or the dressing cutter rotation speed) as a parameter.
[Selection] Figure 6

Description

  The present invention relates to an improvement of an electrode tip dressing apparatus.

  When resistance welding is performed, an electrode tip provided on a welding electrode is worn by heat and pressure generated during welding. The tip of the electrode tip is formed in a truncated cone shape, spherical shape, etc. in order to increase the current density at the welding location, but the tip tip area increases due to wear, and the current density at the welding location gradually decreases. Therefore, dressing (shaping) for adjusting the tip shape of the electrode tip is required.

As a conventional resistance welding electrode tip dressing device that performs such dressing, a dressing device that performs dressing when the number of hit points exceeds a predetermined number (for example, refer to Patent Document 1), and a function of detecting the amount of wear of the electrode tip. What is also possessed (for example, refer to Patent Document 2) is known.
Japanese Patent No. 2708362 Japanese Patent No. 3700390

FIG. 2 of Patent Document 1 will be described.
After the resistance welding is completed, when the set number of welding points required for dressing is reached, dressing is performed, and after the dressing is completed, the amount of wear of the electrode tip is measured, and when it is determined that the electrode tip has reached the wear limit, Will be replaced.

1 and 4 of Patent Document 2 will be described.
The chip dresser includes a chip dress part 1 and a displacement sensor 10 that detects the displacement of the chip dress part 1 in the vertical direction, and detects the chip dress and the amount of chip wear.
The tip dressing section 1 includes a pair of cutter blades 2 and 2, and the tip dressing is performed under predetermined conditions in a state in which the cutter blades 2 and 2 are sandwiched by the welding gun tips 21a and 21b with a predetermined pressing force. .

  The displacement sensor 10 detects the wear amount of the lower tip 21b from the displacement of the tip dress portion 1. The wear amount of the upper tip 21 a is detected by a position detection sensor 23 provided in the servo motor 44 of the welding gun 43.

In Patent Document 1, since the dressing operation is performed under a certain condition every time the welding operation reaches a certain number of hit points, for example, the amount of correction of the electrode tip by one dressing becomes larger than the necessary amount, and the electrode tip May shorten life.
Also in Patent Document 2, the chips 21a and 21b are merely chip dressed under a predetermined condition, and the chip dressing according to the wear amount of the chips 21a and 21b is not performed.

  An object of the present invention is to provide an electrode tip dressing apparatus capable of changing dressing conditions in accordance with the wear amount of the electrode tip.

  According to the first aspect of the present invention, in the electrode tip dressing device for dressing the electrode tip when the tip of the electrode tip attached to the welding gun is worn, the welding work performed by the welding gun (for example, welding) The dressing of the worn electrode tip is controlled according to the dressing time or the number of cutter rotations for dressing as a parameter in accordance with the cumulative number of hit points and the amount of wear of the electrode tip).

As an effect, when the amount of welding work performed by the welding gun is small, the dressing time is shortened or the rotational speed of the cutter for dressing is reduced. When the amount of welding work performed by the welding gun is large, the dressing time is lengthened or the cutter rotational speed of the dressing device is increased.
As described above, dressing according to the welding work amount can be performed.

The invention according to claim 2 is characterized in that the welding work amount is the cumulative number of welding points.
As an effect, if the cumulative number of welding points increases as the work of welding, the amount of wear of the electrode tip increases accordingly, so that the dressing amount of the electrode tip is increased.

The invention according to claim 3 is characterized in that the welding work amount is the actual wear amount of the electrode tip.
As an effect, if the wear amount of the electrode tip increases as the welding work amount, the dressing amount of the electrode tip is increased.

The invention according to claim 4 is characterized in that the welding work is calculated by a calculation unit of a welding machine provided with a welding gun.
As an operation, the welding work amount is calculated by the calculation unit of the welding machine provided with the welding gun, and the dressing amount by the dressing device is controlled according to the welding work amount.

In the invention according to claim 1, the dressing of the worn electrode tip is controlled by using the dressing time or the dressing tool rotation speed as a parameter in accordance with the welding work performed by the welding gun. The dressing amount of the electrode tip can be changed according to the welding work amount, and wasteful dressing of the electrode tip can be prevented.
Therefore, the life of the electrode tip can be extended, the frequency of replacement of the cutter of the dressing apparatus can be reduced, and the cost can be suppressed. Furthermore, the dressing time can be shortened and the power consumption of the chip dresser can be suppressed.

  In the invention according to claim 2, since the welding work amount is the cumulative number of welding points, the dressing device can be easily controlled only by counting the welding points by controlling the dressing device according to the cumulative number of welding points. The control program can be easily created.

  In the invention according to claim 3, since the welding work amount is the actual wear amount of the electrode tip, the dressing amount can be obtained with high accuracy, and unnecessary dressing of the electrode tip can be prevented.

  In the invention according to claim 4, since the welding work is calculated by the calculation unit of the welding machine provided with the welding gun, a series of calculations related to dressing can be performed by the calculation unit of the welding machine, and processing is performed. Can be done quickly.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
FIG. 1 is a block diagram showing the overall configuration of a resistance welding machine according to the present invention. The resistance welding machine 10 includes a welding gun 12 including a pair of gun arms 20 and 22, and the welding gun 12 is interposed via a bracket 14. It is attached to the tip of a robot arm (not shown). Reference numeral 16 denotes a transformer attached to the bracket 14.

The bracket 14 is attached with a transformer 16 and has a support shaft 18 at the tip thereof. Gun arms 20 and 22 are supported on the support shaft 18 so as to be swingable.
Electrode tips 24 and 26 are detachably attached to the tips of the gun arms 20 and 22, respectively, and a pair of output terminals of the transformer 16 are connected to the gun arms 20 and 22, respectively.

  The gun arms 20 and 22 have a pressure cylinder 28 attached to their rear ends, one end of a connecting piece 32 is engaged with a rod 30 extending downward from the pressure cylinder 28, and the other end of the connecting piece 32 has a pin 34. To the rear end of the gun arm 22 and the first link piece 36.

The first link piece 36 is connected to the second link piece 40 via the pin 38, the pin 38 is guided by the guide groove 42, and the second link piece 40 is connected to the rear end of the gun arm 20.
With the above configuration, by operating the pressure cylinder 28, the gun arms 20 and 22 are opened or closed.

  The pressurizing cylinder 28 is controlled by a pneumatic servo circuit 44. The pneumatic servo circuit 44 includes a servo valve 48 controlled by a servo amplifier 46 and a regulator 52 controlled by a driver amplifier 50. Prepare.

  A piston (not shown) is movably accommodated in the pressurizing cylinder 28, and a rod 30 is attached to the piston. The welding gun 12 is detected from the pressure in one of two chambers formed on both sides of the piston. And the opening of the gun arms 20 and 22 from the displacement of the rod 30 (this opening is converted into the distance between the electrode tips 24 and 26, and the amount of wear of the electrode tips 24 and 26) And an opening degree sensor 56 for detecting.

The opening sensor 56 is constituted by a magnetic potentiometer including a magnetic scale attached to the rod 30 and a pickup coil, for example.
The opening degrees of the gun arms 20 and 22 detected by the opening sensor 56 are input to the electrode wear amount calculation means 60 via the A / D converter 58.

  The wear amounts of the electrode tips 24 and 26 calculated by the electrode wear amount calculating means 60 are input to the CPU 62 constituting the pressure controller 63, and the CPU 62 calculates the electrode tips from the wear amounts of the electrode tips 24 and 26. The wear amount change characteristics of 24 and 26 are created, and the welding point cumulative number as the welding work amount is calculated by the calculation unit calculation unit provided in the CPU 62.

  A signal from the pressure sensor 54 is input to the CPU 62 via the A / D converter 61, and the CPU 62 applies a pressure command signal and a signal to the servo amplifier 46 and the driver amplifier 50 via the D / A converters 64 and 66. Supply pressure setting signal.

  The CPU 62 has a ROM 68 for storing the opening degree of the gun arms 20 and 22, a pressure control and a wear amount change characteristic, a chip dresser dressing condition to be described later, and corresponding to each hitting point position. The welding condition data to be stored, that is, data such as the welding current and energizing time, the applied pressure, the opening setting value corresponding to the thickness of the workpiece 69 at the striking point position, and the opening degree of the gun arms 20 and 22 after welding are temporarily stored. RAM 70 to be used, and wear limit setting means 72 for presetting the wear limit amounts of the respective electrode tips 24 and 26 are provided.

A setting signal for welding current and energization time is transmitted from the CPU 62 to the transformer 16 via the energization control circuit 74, and the electrode chips 24 and 26 are energized for a predetermined time with a predetermined current value.
The CPU 62 receives a spot position determination signal from the robot controller 76, and reads the welding condition data corresponding to the spot position where the welding gun 12 arrives from the RAM 70.
A welding controller 82 is communicably connected to the robot controller 76 and the pressure controller 63.

  When the electrode tips 24 and 26 are worn, the tips of the electrode tips 24 and 26 are shaped by the tip dresser 100 as a dressing device controlled by the CPU 62.

  FIG. 2 is a side view showing a chip dresser according to the present invention. The chip dresser 100 includes a base portion 101, a support column 102 extending upward from the base portion 101, and a housing 103 attached to the upper end portion of the support column 102. And a dresser main body 104 provided in the housing 103, an electric motor 106 attached to the upper portion of the support column 102, and a motor driving unit 107 for driving the electric motor 106 in response to a control signal from the CPU 62. .

The dresser body 104 includes a cutter 111 that shapes the electrode tips 24 and 26 pressed from above and below, and a driving force transmission mechanism 112 that transmits a driving force from the electric motor 106 side to the cutter 111 to drive the cutter 111. It consists of.
The chip dresser 100 and the CPU 62 described above constitute the dressing control device 113.

  FIG. 3 is a cross-sectional view showing a cutter provided in the chip dresser according to the present invention, and a chip shaping recess having a truncated cone shape on the upper and lower surfaces of the cutter 111 rotatably provided in the housing 103 of the chip dresser 100. 11a and 111b are formed. 111c is a plurality of blade portions formed in the chip shaping recesses 111a and 111b (the chip shaping recesses 111a and 111b are formed by the cutting blades of the plurality of blade portions 111c), and 115 and 115 are between the housing 103 and the cutter 111. Is a bush provided.

The procedure for dressing the electrode tips 24 and 26 described above will be described below.
4 (a) and 4 (b) are operation diagrams showing dressing of the electrode tip by the tip dresser according to the present invention.
(A) is a figure which shows the state before shaping | molding of the electrode tips 24 and 26, and the tip shaping recessed part provided in the cutter 111 of the tip dresser 100 as the electrode tips 24 and 26 with which the front-end | tip was worn is shown by the arrow. The electrode tips 24 and 26 are shaped by inserting them into 111a and 111b, applying a predetermined pressure with the gun arms 20 and 22 (see FIG. 1), and rotating the cutter 111 under predetermined dressing conditions.

  (B) is a figure which shows the state after the shaping | molding of the electrode tips 24 and 26, and has shown that the front-end | tip of the electrode tips 24 and 26 was shaped in the desired shape.

FIGS. 5A to 5D are cross-sectional views showing changes in the tip shape of the electrode tip, FIGS. 5A to 5C are examples (this embodiment), and FIG. 5D is a comparative example. .
(A) shows the cross-sectional shape before use (that is, unused) of the electrode tips 24 and 26 of the embodiment (reference numeral 24 is not shown).
The tips of the electrode tips 24 and 26 are formed in a tapered truncated cone shape in order to increase the current density during resistance welding.

(B) is the tip cross-sectional shape of the electrode tips 24 and 26 after performing the resistance welding of the predetermined number of hit points with the electrode tips 24 and 26 of the embodiment, and shows a state before shaping by the tip dresser.
The tips of the tip dressers 24 and 26 are worn by heat, sparks, and pressure applied during resistance welding. Let W be the wear amount of the most worn portion.

(C) shows a state after the tips of the worn electrode tips 24 and 26 of the embodiment are shaped by the tip dresser.
The tips of the electrode tips 24 and 26 are shaped into a truncated cone as in the state before use of FIG. When the dressing amount (cutting amount) by the chip dresser is D1, the dressing amount D1 is the same as or almost the same as the wear amount W shown in (b).

(D) shows a state after the tip of the worn electrode tip 201 of the comparative example is shaped by a tip dresser.
The tip of the electrode tip 201 is shaped into a truncated cone, and if the dressing amount by the tip dresser is D2, the dressing amount D2 is a constant amount for every fixed number of hit points of the electrode tip 201, as shown in FIG. This may increase the dressing amount D1 of the embodiment and shorten the life of the electrode tip.

FIG. 6 is a flowchart (Embodiment 1) showing the flow of dressing by the electrode tip dressing apparatus according to the present invention. STXX in the figure indicates a step number.
ST01 ... In the mass production line, it is determined whether the number of workpiece welds has reached the set number, or whether the number of workpiece hits has reached the set number.
This is output to the CPU 62 (see FIG. 1) as the welding work amount from the electrode wear amount calculating means 60 (see FIG. 1) of the welding machine.

When the number of workpieces has reached the set number, or when the number of workpieces has reached the set number (YES), the process proceeds to ST02.
When the number of workpieces does not reach the set number and the number of workpieces does not reach the set number (NO), ST01 is executed again.
ST02 ... The wear amount W of the electrode tip is detected as the welding work amount.

ST03 ... A dressing time T is set as a dressing condition according to the wear amount W of the electrode tip.
Condition 1: If the wear amount W of the electrode tip is 0 mm <W ≦ 0.5 mm, the dressing time T is set to T = 0.3 sec.
Condition 2: If the wear amount W of the electrode tip is 0.5 mm <W ≦ 0.8 mm, the dressing time T is set to T = 0.7 sec.
Condition 3: If the wear amount W of the electrode tip is 0.8 mm <W ≦ 1.2 mm, the dressing time T is set to T = 2.0 sec.

ST04 ... Pressurize with a predetermined pressure.
ST05 ... Dressing is performed under the above dressing conditions.
ST06 ... The number of workpieces set or the number of hit points is cleared.

FIG. 7 is a flowchart (Embodiment 2) showing the flow of dressing by the electrode tip dressing apparatus according to the present invention. STXX in the figure indicates a step number.
ST11 ... In the mass production line, it is determined whether the number of workpiece welds has reached the set number, or whether the number of workpiece hits has reached the set number.

If the number of workpieces reached the set number, or the number of workpiece hits reaches the set number (YES), the process proceeds to ST12.
When the number of workpiece welds does not reach the set number and the number of workpiece hits does not reach the set number (NO), ST11 is executed again.
ST12 ... The wear amount W of the electrode tip is detected as the welding work amount.

ST13 ... The rotation speed R of the cutter (that is, the dressing tool) is set as the dressing condition according to the wear amount W of the electrode tip.
Condition 1: If the wear amount W of the electrode tip is 0 mm <W ≦ 0.5 mm, the cutter rotation speed R is set to R = 5 rotations / sec.
Condition 2: If the wear amount W of the electrode tip is 0.5 mm <W ≦ 0.8 mm, the cutter rotation speed R is set to R = 10 rotations / sec.
Condition 3: If the wear amount W of the electrode tip is 0.8 mm <W ≦ 1.2 mm, the cutter rotation speed R is set to R = 15 rotations / sec.

ST14: Pressurization is performed with a predetermined pressure.
ST15 ... Dressing is performed under the above dressing conditions.
ST16 ... The number of workpieces set or the number of hits is cleared.

  By performing the dressing shown in FIGS. 6 and 7, the wear amount W and the dressing amount D shown in FIG. 5C can be made substantially the same, and unnecessary dressing can be prevented. The life of the electrode tips 24 and 26 can be extended.

  FIG. 8 is a graph showing the relationship between the dressing time and the dressing amount of the electrode tip by the tip dresser according to the present invention, and the pressing force of the electrode tip and the rotational speed of the cutter are set to predetermined conditions. The vertical axis of the graph represents dressing amount D (unit: mm), and the horizontal axis represents dressing time T (unit: (sec)).

  The points in the figure represent measured values, and the straight line represents the primary regression line. That is, as the dressing time T becomes longer, the dressing amount D increases. Based on this linear regression line, the dressing time T corresponding to the wear amount W shown in FIG. 6 is shown in FIG. A dressing tool rotation speed R corresponding to the wear amount W is obtained.

  As shown in FIGS. 1, 2, 6, and 7, when the tips of the electrode tips 24, 26 attached to the welding gun 12 are worn, the electrode tips dressing the electrode tips 24, 26. In the tip dresser 100 as a dressing device of 24, 26, the worn electrode tips 24, 26 are worn according to the work of welding performed by the welding gun 12 (for example, the cumulative number of welding points, electrode tip wear amount W). The dressing is controlled using the dressing time T or the rotational speed R of the dressing cutter 111 as a parameter.

  Accordingly, the dressing amount D (see FIG. 5) of the electrode tips 24 and 26 can be changed according to the work of welding performed by the welding gun 12, and unnecessary dressing of the electrode tips 24 and 26 can be prevented. Can do.

  Accordingly, the lifetime of the electrode tips 24 and 26 can be extended, and the replacement frequency of the cutter 111 of the tip dresser 100 can be reduced, thereby reducing the cost. Furthermore, the dressing time T can be shortened, and the power consumption of the chip dresser 100 can also be suppressed.

  Preferably, since the work of welding is the cumulative number of welding spots, the tip dresser 100 can be easily controlled simply by counting the welding spots by controlling the tip dresser 100 according to the cumulative number of welding spots. And a dressing control program can be easily created.

  Preferably, since the welding work amount is the actual wear amount of the electrode tips 24, 26, the dressing amount D1 can be obtained with high accuracy, and unnecessary dressing of the electrode tips 24, 26 can be prevented. .

  Furthermore, since the work of welding is calculated by the calculation unit of the CPU 62 constituting the resistance welding machine 10 provided with the welding gun 12, a series of calculations related to dressing can be performed by the calculation unit of the resistance welding machine 10. , Processing can be performed quickly.

  In the embodiment shown in FIGS. 6 and 7, Condition 1 to Condition 3 are provided as dressing conditions according to the wear amount W. However, the present invention is not limited to this, and the classification of the wear amount W for each condition is further subdivided. To increase the number of conditions. Thereby, the difference between the wear amount W and the dressing amount D1 can be further reduced.

  The dressing apparatus for electrode tips of the present invention is suitable for resistance welding machines.

It is a block diagram showing the whole resistance welding machine composition concerning the present invention. It is a side view which shows the chip dresser which concerns on this invention. It is sectional drawing which shows the cutter with which the chip dresser which concerns on this invention is equipped. It is an effect | action figure which shows the dressing of the electrode chip | tip by the chip dresser which concerns on this invention. It is. It is a flowchart (Example 1) which shows the flow of the dressing by the dressing apparatus of the electrode chip concerning this invention. It is a flowchart (Example 2) which shows the flow of the dressing by the dressing apparatus of the electrode chip concerning this invention. It is a graph which shows the relationship between the dressing time and dressing amount of the electrode chip | tip by the chip dresser which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 12 ... Welding gun, 24, 26 ... Electrode tip, 69 ... Workpiece, 100 ... Tip dresser, 113 ... Dressing control apparatus, R ... Dressing cutter rotation speed, T ... Dressing time, W ... Wear amount of electrode tip.

Claims (4)

In the electrode tip dressing device for dressing this electrode tip when the tip of the electrode tip attached to the welding gun is worn,
The electrode tip dressing apparatus, wherein the dressing of the worn electrode tip is controlled by using the dressing time or the rotation speed of the dressing cutter as a parameter according to the welding work performed by the welding gun.   The electrode tip dressing apparatus according to claim 1, wherein the welding work amount is a cumulative number of welding points.   2. The electrode tip dressing device according to claim 1, wherein the welding work amount is an actual wear amount of the electrode tip.   2. The electrode tip dressing device according to claim 1, wherein the welding work amount is calculated by a calculation unit of a welding machine provided with the welding gun.

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