WO2000001507A1

WO2000001507A1 - A method for manufacturing a resistance welding tip

Info

Publication number: WO2000001507A1
Application number: PCT/IB1999/001192
Authority: WO
Inventors: Leon Vincent De Bruin
Original assignee: Springset Fasteners Natal (Proprietary) Limited; Crozier, Trevor
Priority date: 1998-07-02
Filing date: 1999-06-24
Publication date: 2000-01-13
Also published as: AU4639099A; CA2336349A1

Abstract

A method of manufacturing a welding tip for resistance welding includes the steps of forming stock having at least two concentric metallic layers; parting the stock into desired lengths, with each length having the concentric metallic layers; and applying a forming process to each length of stock so that a front end of each length defines a contact surface for resistance welding. The invention includes a welding tip for resistance welding.

Description

A METHOD FOR MANUFACTURING A RESISTANCE WELDING TIP

This invention relates to resistance welding. More particularly,

this invention relates to a method of manufacturing a welding tip for

resistance welding, to a welding tip for resistance welding, to a method of

manufacturing stock for a welding tip for resistance welding and to stock

for a welding tip for resistance welding.

According to a first aspect of the invention, there is provided

a method of manufacturing a welding tip for resistance welding, the method

including the steps of:

forming stock having at least two concentric metallic layers;

parting the stock into desired lengths, with each length having the

concentric metallic layers; and

applying a forming process to each length of stock so that a front

end of each length defines a contact surface for resistance welding.

The stock may be formed by drawing a circular cylindrical tube

of a first metallic material over a circular cylindrical rod of a second metallic

material. At least one of the rod and the tube may be deformed in the

drawing to retain the rod in the tube once the tube has been drawn over

the rod. Thus dimensions of the rod and the tube may be preselected so

that deformation of one of the rod and the tube occurs to retain the rod in the tube once the tube has been drawn over the rod.

Instead, the stock may be formed by extruding a circular

cylindrical tube of a first metallic material over a circular cylindrical rod of

a second metallic material. Further instead, the stock may be formed by

extruding a circular cylindrical tube of a first metallic material and

simultaneously extruding a rod of a second metallic material, the tube being

extruded over the rod and concentrically therewith.

The method may include the step of shaping each length of

stock so that a rear end of each length defines a mounting for mounting the

welding tip on to a resistance welding tool.

The forming process applied to each length of stock for

defining the contact surface may include cold forging. The shaping of each

length of stock to define the mounting may also be by means of cold

forging.

A cavity may be formed in each length of stock, the cavity

opening at the rear end of the length of stock. Then, an inner, cavity-

defining surface of the length of stock may be shaped to define the

mounting for mounting the welding tip on to a resistance welding tool. The

cavity-defining surface may be shaped by means of cold forging. The contact surface of each length of stock may be formed in

a first operation, the cavity may be formed in a second operation, and the

inner cavity-defining surface may be shaped in a third operation. Instead,

the contact surface and the cavity may be formed and the cavity-defining

surface shaped in a single operation.

The method may include drawing the tube over the rod in the

absence of a lubricating medium between the rod and the tube.

According to a second aspect of the invention, there is

provided a welding tip for resistance welding, the welding tip including

a metallic body having a passage defined therein; and

a discreet metallic core, the core being secured to the body, in the

passage, with the front end of the body and a corresponding front end of

the core being shaped to define a contact surface for resistance welding,

and with at least the body defining a mounting formation to permit the body

and the core to be mounted on a welding tool, the body and the core

having been formed from a preselected length parted from a length of stock

having at least two concentric metallic layers.

One of the body and the core may be of a material having a

higher electrical conductivity than the material of the other. Further, one

of the body and the core may be of a material having a higher tensile

strength than the material of the other. Still further, one of the body and the core may be of a material having a higher hardness than the material of

the other.

The mounting formation may be defined by the body and the

core.

The core may project from the front end of the body. Instead,

the front end of the core may be substantially flush with the front end of

the body.

The mounting formation may be in the form of a cavity defined

in the core and opening at a rear end of the core and the body. Instead, the

mounting formation may be in the form of a cavity defined in the body and

opening at a rear end of the body. Then, an inner cavity-defining surface

of the body may frusto-conical in shape, tapering inwardly from the rear end

of the body. It is to be appreciated that the mounting formation can be of

any suitable shape to suit the welding machine on which the welding tip is

to be mounted.

The body of the welding tip may be of substantially pure

copper.

The core of the welding tip may be of an alloy of copper. The

alloy of copper may be one of the following: (a) Copper-Chromium-Zirconium;

(b) Copper-Zirconium;

(c) Copper-Chromium;

(d) Copper-Nickel-Tin-Chromium;

(e) Copper-Nickel-Cobalt-Beryllium;

(f) Copper-Beryllium;

(g) Sintered Copper-Tungsten;

(h) Copper-Silver.

Instead, the core of the welding tip may be of an alloy of

silver.

In a preferred embodiment of the invention, for use in

resistance welding of aluminium, the body may be of substantially pure

copper and the core may be of sintered copper-tungsten.

According to a third aspect of the invention, there is provided

a method of manufacturing stock for the fabrication of resistance welding

tips, the method including the step of drawing a circular cylindrical tube of

a first metallic material over a circular cylindrical rod of a second metallic

material.

At least one of the rod and the tube may be deformed in the

drawing to retain the rod in the tube once the tube has been drawn over the rod.

According to a fourth aspect of the invention, there is provided

a method of manufacturing stock for the fabrication of resistance welding

tips, the method including the step of extruding a circular cylindrical tube

material.

According to a fifth aspect of the invention, there is provided

a method of manufacturing stock for the fabrication of resistance welding

tips, the method including the step of extruding a circular cylindrical tube

of a first metallic material and simultaneously extruding a rod of a second

metallic material, the tube being extruded over the rod and concentrically

therewith.

According to a sixth aspect of the invention, there is provided

stock for the manufacture of welding tips, the stock including

a metallic body having an axially extending passage defined

therethrough; and

a discreet metallic core coterminous with the body, the core being

secured to the body, in the passage.

The invention is now described, by way of examples, with

reference to the accompanying drawings. In the drawings,

Figure 1 shows a side sectioned view of a first embodiment of a

length of stock, in accordance with the invention, for welding tips for

resistance welding;

Figure 2 shows a side sectioned view of a welding tip, in accordance

with the invention, for resistance welding, fabricated from the stock of

Figure 1 ;

Figure 3 shows a side sectioned view of a second embodiment of a

length of stock, in accordance with the invention, for welding tips for

resistance welding;

Figure 4 shows a side sectioned view of a second embodiment of a

welding tip, in accordance with the invention, for resistance welding,

manufactured from the stock of Figure 3;

Figure 5 shows a length of stock to be used in the manufacture of a

welding tip for resistance welding according to a method of the invention;

Figure 6 shows the length of stock in a first stage of the manufacture

of the welding tip;

Figure 7 shows the length of stock in a second stage of manufacture

of the welding tip;

Figure 8 shows the length of stock in a third stage of manufacture

of the welding tip;

Figure 9 shows a side sectioned view of a third embodiment of the

welding tip;

Figure 1 0 shows dimensions of the welding tip of Figure 4; and Figure 1 1 shows a side sectioned view of a fourth embodiment of the

welding tip.

In Figure 1 , reference numeral 1 0 generally indicates a length

of stock, in accordance with the invention, for manufacturing welding tips

for resistance welding.

The length of stock 1 0 includes a circular cylindrical tube 1 2

and a cylindrical rod 1 4. The tube 1 2 is drawn over the rod 1 4 in a

conventional drawing process with the absence of a lubricant between the

rod 14 and the tube 1 2.

The tube 1 2 is of cathodic copper while the rod 1 4 is of a

copper alloy. The tube 1 2 is of a more readily deformable than the rod 14.

Thus, as the tube 1 2 is drawn over the rod 14, the tube 1 2 is deformed.

This, together with the fact that a lubricating medium is not used, results

in the rod 14 being fixed within the tube 1 2.

The copper alloy can be chosen to suit a user's requirements.

Some examples of the copper alloy are:

(a) Copper-Chromium-Zirconium

(b) Copper-Zirconium

(c) Copper-Chromium

(d) Copper-Nickel-Tin-Chromium (e) Copper-Nickel-Cobalt-Beryllium

(f) Copper-Beryllium

It will be appreciated that, instead, the rod 1 4 may be of a

alloy of silver.

The stock 1 0 can be supplied in indefinite lengths or in

predetermined lengths, depending on a user's requirements. The stock 10

can also be supplied in different diameters to suit a user's requirements.

In Figure 2, reference numeral 20 generally indicates a first

embodiment of a welding tip, in accordance with the invention,

manufactured from the stock 1 0.

The tip 20 includes a body 22 having a passage 23 defined

therethrough. A core 24 is fixed within the body 22. A front end 26 of the

body 22 is flush with a front end 28 of the core 24.

The front ends 26, 28 of the body 22 and the rod 28,

respectively, are shaped to define a contact surface 30 suitable for

resistance welding. In particular, the front ends 26, 28 are shaped to define

a domed profile. Those skilled in the art will appreciate that the front ends

26, 28 can be of any shape to suit a particular application. A cavity 32 is defined in a rear end 34 of the core 24. The

cavity 32 is formed so that a portion 36 of the core 24 is radially deformed

to define a wall 38 which defines the cavity 32.

The cavity 32 is formed in a stamping operation while the body

22 is inhibited from moving radially outwardly. This results in a portion 40

of the body 22 surrounding the wall 38 being reduced in thickness.

The cavity 32 facilitates mounting of the tip 20 on to a welding

tool (not shown) .

In Figure 3, reference numeral 50 generally indicates a second

embodiment of a length of stock, in accordance with the invention, for the

manufacture of welding tips for resistance welding. With reference to Figure

2, like reference numerals refer to like parts, unless otherwise specified.

The tube 1 2 of the stock 50 has an outer diameter of

approximately 1 6,0 mm. The rod 1 4 of the stock 50 has a diameter of

approximately 6,3 mm.

In Figure 4, reference numeral 60 generally indicates a second

embodiment of a welding tip, in accordance with the invention,

manufactured from the stock 50. With reference to Figure 2, like reference

numerals refer to like parts, unless otherwise specified. The body 22 of the welding tip 60 defines the cavity 32. The

cavity 32 is frusto-conical and tapers inwardly from the rear end 34 of the

body 22.

The core 24 of the welding tip 60 is positioned in a passage

62 which extends from a front end 64 of the cavity 32 to open at the front

end 26 of the body 22. The core 24 and the passage 62 define

corresponding waisted transverse profiles. It follows that the core 24 is

effectively locked in the passage 62. The front end 28 of the core 24 is

proud of the front end 26 of the body 22 to an extent of approximately 0,2

mm.

In Figures 6 to 8, there are shown three stages of

transformation of a length 66 of stock 50, shown in Figure 5, to the

welding tip 60 during the manufacture of the welding tip 60. With reference

to Figures 1 to 4, like reference numerals refer to like parts, unless

otherwise specified.

In a first stage of manufacture, a front end 68 of the length 66

of stock 50 is cold forged so that the front end 68 has a curved axial profile

as shown in Figure 6. In a second stage of manufacture, the length 66 is

held in a die and a circular cylindrical cavity 70 is punched into a rear end

72 of the length 66. This results in elongation of the length 66 and the

formation of the core 24 positioned in the passage 62. This also has the effect of urging the core 24 forward to stand proud as described above.

Further, as a result of the different characteristics of the rod 1 4 and the

tube 1 2, the core 24 and the tube 1 2 are deformed so that the core 24 and

the passage 62 define the complementary waisted axial profiles described

above.

In a third stage of operation, the length 66 is held in a die and

a tapering tool is pressed into the cavity 70 to form the frusto-conical cavity

32 described above. This results in further elongation of the tube 1 2 so that

the body 22 reaches a desired length at this stage.

In Figure 9, reference numeral 70 generally indicates a third

embodiment of a welding tip, in accordance with the invention,

manufactured from the stock 50. With reference to Figures 2 and 4, like

reference numerals refer to like parts, unless otherwise specified.

The welding tip 70 has the same general shape as the welding

to 60 of Figure 4, and is manufactured in the same general process

described above in respect of the tip 60, illustrated in Figures 5 to 8, with

the exception that in forming the cavity 32, a slug 72 of the material of the

body 22 is urged behind a rear end 74 of the core 24.

The following table give typical dimensions of the tip 60,

illustrated in Figure 4, with reference to Figure 1 0:

It will be appreciated that the above dimensions are for

example purposes only, and may be varied to suit user requirements.

In Figure 1 1 , reference numeral 80 generally indicates a fourth

embodiment of a welding tip, in accordance with the invention,

manufactured from the stock 50. With reference to Figures 2, 4, and 9, like

reference numerals refer to like parts, unless otherwise specified.

Again, the welding tip 80 has the same general, shape as the

welding to 60 of Figure 4, and is manufactured in the same general process

described above in respect of the tip 60, illustrated in Figures 5 to 8, with

the exception that in forming the contact surface 30, a front portion 82 is

tapered to provide a more pointed profile than is the case with the tip 60.

It is a problem with welding tips that they wear out at a rate

which results in excessive downtime of welding equipment and resultant

high costs. The reason for this is that, generally, welding tips are of a metal which has a high electrical conductivity. Such a metal is cathodic

copper. Unfortunately, cathodic copper is of a relatively low tensile

strength and relatively low wear resistance. Consequently, it tends to wear

out at an unacceptable rate.

It has been found that by using welding tips of a copper alloy

the wear rate can be reduced. However, copper alloys do not have the high

electrical conductivity of copper and this can result in certain problems.

By having the core 24 of the copper alloy and the body 22 of

cathodic copper, the applicant believes it can obtain a suitable electrical

conductivity together with adequate strength. Furthermore, the applicant

believes that by using the method of this invention, the stock 10 can be

produced at a relatively low cost.

Claims

1 . A method of manufacturing a welding tip for resistance welding, the

method including the steps of:

forming stock having at least two concentric metallic layers;

parting the stock into desired lengths, with each length having

the concentric metallic layers; and applying a forming process to each length of stock so that a

front end of each length defines a contact surface for

resistance welding.

2. The method as claimed in Claim 1 , the stock is formed by drawing

a circular cylindrical tube of a first metallic material over a circular

cylindrical rod of a second metallic material.

3. The method as claimed in Claim 2, in which at least one of the rod

and the tube is deformed in the drawing to retain the rod in the tube

once the tube has been drawn over the rod.

4. The method as claimed in Claim 1 , in which the stock is formed by

extruding a circular cylindrical tube of a first metallic material over a

circular cylindrical rod of a second metallic material.

5. The method as claimed in Claim 1 , in which the stock is formed by extruding a circular cylindrical tube of a first metallic material and

simultaneously extruding a rod of a second metallic material, the tube

being extruded over the rod and concentrically therewith.

6. The method as claimed in Claim 1 , which includes the step of

shaping each length of stock so that a rear end of each length

defines a mounting for mounting the welding tip on to a resistance

welding tool.

7. The method as claimed in Claim 6, in which the forming process

applied to each length of stock for defining the contact surface

includes cold forging.

8. The method as claimed in Claim 6, in which the shaping of each

length of stock to define the mounting is by means of cold forging.

9. The method as claimed in Claim 6, in which a cavity is formed in

each length of stock, the cavity opening at the rear end of the length

of stock.

1 0. The method as claimed in Claim 9, in which an inner, cavity-defining

surface of the length of stock is shaped to define the mounting for

mounting the welding tip on to a resistance welding tool.

1 . The method as claimed in Claim 1 0, in which the cavity-defining

surface is shaped by means of cold forging.

2. The method as claimed in Claim 1 0, in which the contact surface of

each length of stock is formed in a first operation, the cavity is

formed in a second operation, and the inner cavity-defining surface

is shaped in a third operation.

3. The method as claimed in Claim 1 0, in which the contact surface and

the cavity are formed and the cavity-defining surface shaped in a

single operation.

4. The method as claimed in Claim 2, which includes drawing the tube

over the rod in the absence of a lubricating medium between the rod

and the tube.

5. A welding tip for resistance welding, the welding tip including

a metallic body having a passage defined therein; and

a discreet metallic core, the core being secured to the body,

in the passage, with the front end of the body and a

corresponding front end of the core being shaped to define a

contact surface for resistance welding, and with at least the

body defining a mounting formation to permit the body and

the core to be mounted on a welding tool, the body and the core having been formed from a preselected length parted

from a length of stock having at least two concentric metallic

layers.

1 6. The welding tip as claimed in Claim 1 5, in which one of the body and the core is of a material having a higher electrical conductivity than

the material of the other.

1 7. The welding tip as claimed in Claim 1 5, in which one of the body and

the core is of a material having a higher tensile strength than the

material of the other.

1 8. The welding tip as claimed in Claim 1 5, in which one of the body and

the core is of a material having a higher hardness than the material

of the other.

1 9. The welding tip as claimed in Claim 1 5, in which the mounting

formation is defined by the body and the core.

20. The welding tip as claimed in Claim 1 5, in which the core projects

from the front end of the body.

21 . The welding tip as claimed in Claim 1 5, in which the front end of the

core is substantially flush with the front end of the body.

22. The welding tip as claimed in Claim 1 5, in which the mounting

formation is in the form of a cavity defined in the core and opening

at a rear end of the core and the body.

23. The welding tip as claimed in Claim 1 5, in which the mounting

formation is in the form of a cavity defined in the body and opening

at a rear end of the body.

24. The welding tip as claimed in Claim 23, in which an inner cavity-

defining surface of the body is frusto-conical in shape, tapering

inwardly from the rear end of the body.

25. The welding tip as claimed in Claim 1 5, in which the body is of

substantially pure copper.

26. The welding tip as claimed in Claim 1 5, in which the core is of an

alloy of copper.

27. The welding tip as claimed in Claim 1 5, in which the alloy of copper

is one of the following:

(a) Copper-Chromium-Zirconium;

(b) Copper-Zirconium;

(c) Copper-Chromium;

(d) Copper-Nickel-Tin-Chromium; (e) Copper-Nickel-Cobalt-Beryllium;

(f) Copper-Beryllium;

(g) Sintered Copper-Tungsten; (h) Copper-Silver.

28. The welding tip as claimed in Claim 1 5 in which the core is of an

alloy of silver.

29. A method of manufacturing stock for the fabrication of resistance

welding tips, the method including the step of drawing a circular

cylindrical tube of a first metallic material over a circular cylindrical

rod of a second metallic material.

30. The method as claimed in Claim 29, in which at least one of the rod

and the tube is deformed in the drawing to retain the rod in the tube

once the tube has been drawn over the rod.

31 . A method of manufacturing stock for the fabrication of resistance

welding tips, the method including the step of extruding a circular

cylindrical tube of a first metallic material over a circular cylindrical

rod of a second metallic material.

32. The method of manufacturing stock for the fabrication of resistance

welding tips, the method including the step of extruding a circular cylindrical tube of a first metallic material and simultaneously

extruding a rod of a second metallic material, the tube being extruded

over the rod and concentrically therewith.

33. Stock for the manufacture of welding tips, the stock including

a metallic body having an axially extending passage defined

therethrough; and

a discreet metallic core coterminous with the body, the core

being secured to the body, in the passage.

34. A method of manufacturing a welding tip for resistance welding

substantially as herein described with reference to the accompanying

diagrammatic drawings.

35. A welding tip for resistance welding substantially as herein described

with reference to the accompanying diagrammatic drawings.

36. A method of manufacturing stock for the fabrication of resistance

welding tips substantially as herein described with reference to the accompanying diagrammatic drawings.

37. Stock for the manufacture of welding tips substantially as herein

described with reference to the accompanying diagrammatic drawings.