Method and apparatus for resistive spot welding

Patent metadata

Field	Value
Publication number	US-2016016252-A1
Application number	US-201414333064-A
Country	US
Kind code	A1
Filing date	Jul 16, 2014
Priority date	Jul 16, 2014
Publication date	Jan 21, 2016
Grant date	—

Abstract

An apparatus and corresponding methods are disclosed to resistively spot weld a stack of sheet metal having a plurality of sheets of sheet metal. In one embodiment, a method includes contacting a first welding tip to a first side of the stack and contacting a second welding tip to a second side of the stack, the second side comprising a thinnest exterior sheet of the stack, the second welding tip including a contacting surface area less than the first welding tip; applying a squeeze pressure to the stack; and applying a current to the stack by applying a first current pulse for a first duration followed by applying a second current pulse for a second duration longer than the first duration and with a lower current than a current of the first current pulse.

First claim

What is claimed is:

1 . A method of resistive spot welding, the method comprising:
contacting a first welding tip to a first side of a stack of sheet metal, wherein the stack of sheet metal includes a plurality of sheets of sheet metal having; contacting a second welding tip to a second side of the stack of sheet metal, wherein the second welding tip includes a contacting surface area less than a contacting surface area of the first welding tip, and wherein the second side of the stack of sheet metal includes a thinnest exterior sheet of the plurality of sheets of sheet metal of the stack of sheet metal; applying a squeeze pressure to the stack of sheet metal between the first welding tip and the second welding tip; and applying a current to the stack of sheet metal between the first welding tip and the second welding tip to resistively spot weld the stack of sheet metal, wherein applying the direct current comprises applying a first current pulse for a first duration followed by applying a second current pulse for a second duration longer than the first duration, the second current pulse having a lower current than a current of the first current pulse.

2 . The method of claim 1 further comprising contacting the first welding tip to the first side of the stack of sheet metal, wherein the stack of sheet metal has a stack ratio of at least seven.

3 . The method of claim 1 further comprising forming the stack of sheet metal to include at least four individual sheets of sheet metal.

4 . The method of claim 1 wherein applying a current to the stack of sheet metal between the first welding tip and the second welding tip further comprises applying a direct current to the stack of sheet metal.

5 . The method of claim 1 , further comprising performing a tip dressing procedure on the first welding tip and the second welding tip after performing a plurality of spot welding procedures.

6 . The method of claim 1 , wherein each of the first welding tip and the second welding tip comprises a spherical welding tip.

7 . The method of claim 1 , further comprising applying at least one intermediate current pulse to the stack of sheet metal after applying the first current pulse and before applying the second current pulse, wherein the intermediate current pulse is distinguishable from both the first current pulse and the second current pulse by one or more of the following: a current value, a duration of application, and a separation by a gap in time between applications.

8 . The method of claim 1 , further comprising waiting a period of cooling time after applying the first current pulse to the stack of sheet metal and before applying the second current pulse to the stack of sheet metal.

9 . The method of claim 8 , wherein waiting a period of cooling time comprises waiting five cycles to nine cycles, wherein one cycle is 1/60th of one second.

10 . The method of claim 1 , wherein applying the first current pulse comprises applying the first current pulse for the first duration of two cycles to five cycles, wherein one cycle is 1/60th of one second, and wherein applying the second current pulse comprises applying the second current pulse for the second duration of 25 cycles to 35 cycles.

11 . The method of claim 10 , further comprising: applying at least one intermediate current pulse for a third duration of two cycles to five cycles after applying the first current pulse and before applying the second current pulse.

12 . An apparatus, comprising:
a servo-gun resistive spot welding device comprising:
a first welding tip configured to contact a first side of a stack of sheet metal, wherein the stack of sheet metal includes a plurality of sheets of sheet metal; and
a second welding tip configured to contact a second side of the stack of sheet metal, the second welding tip including a contacting surface area less than a contacting surface area of the first welding tip, wherein the second side of the stack of sheet metal includes a thinnest exterior sheet of the plurality of sheets of sheet metal of the stack of sheet metal,
the first welding tip and the second welding tip applying a squeeze pressure and a current to the stack of sheet metal therebetween to resistively spot weld the stack of sheet metal; and a controller coupled in signal communication with the servo-gun resistive spot welding device to, at least in part, effect application of the current to the stack of sheet metal, the controller configured to:
effect application of a first current pulse for a first duration; and
effect application of a second current pulse at a second duration longer than the first duration, wherein the second current pulse is applied following the application of the first current pulse.

13 . The apparatus of claim 12 , wherein the first welding tip and the second welding tip are configured to resistively spot weld a stack of sheet metal having a stack ratio of at least seven.

14 . The apparatus of claim 12 , wherein the first welding tip and the second welding tip are configured to resistively spot weld a stack of sheet metal including at least four individual sheets of sheet metal.

15 . The apparatus of claim 12 , wherein the first welding tip and the second welding tip are configured to apply a direct current to the stack of sheet metal therebetween to resistively spot weld the stack of sheet metal.

16 . The apparatus of claim 12 , wherein each of the first welding tip and the second welding tip comprises a spherical welding tip.

17 . The apparatus of claim 12 , wherein the controller is configured to effect application of an intermediate current pulse prior to application of the second current pulse, wherein the intermediate current pulse is distinguishable from both the first current pulse and the second current pulse by one or more of the following: a current value, a duration of application, and a separation by a gap in time between applications.

18 . The apparatus of claim 12 , wherein the controller is configured to effect waiting a period of cooling time after applying the first current pulse to the stack of sheet metal and before applying the second current pulse.

19 . The apparatus of claim 12 , wherein the controller is configured to:
effect application of the first current pulse for the first duration of two cycles to five cycles, wherein one cycle is 1/60th of one second; and effect application of the second current pulse for the second duration of 25 cycles to 35 cycles.

20 . The apparatus of claim 19 , wherein the controller is configured to effect application of the intermediate current pulse for the third duration of two cycles to five cycles after effecting application of the first current pulse and before effecting application of the second current pulse.

21 . The apparatus of claim 12 , further comprising a tip dresser configured to dress the first welding tip and the second welding tip after performing a plurality of spot welding procedures.

22 . A method of resistively spot welding a stack of sheet metal, the stack of sheet metal including at least four individual sheets of sheet metal and having a stack ratio of seven or higher, the method comprising:
applying a squeeze force to the stack of sheet metal positioned between a first welding tip and a second welding tip, wherein the second welding tip has a contact surface area greater than a contact surface area of the first welding tip, and the second welding tip is in direct contact with a

Assignees

• Edwards Ii Paul C
• Honda Motor Co Ltd

Inventors

• Edwards Ii Paul C

Classifications

• B23K11/24 Primary

  Electric supply or control circuits therefor · CPC title

• B23K11/115

  by means of two electrodes placed opposite one another on both sides of the welded parts · CPC title

• B23K11/16

  taking account of the properties of the material to be welded · CPC title

• B23K11/11 Primary

  Spot welding · CPC title

• B23K11/36

  Auxiliary equipment (B23K11/31 takes precedence) · CPC title