IIW Doc. XII-2171-14

Development of Two Piece Type Contact Tip for Long Life
M.Kutsuna1 and T. Murakami2
1

Advanced Laser Technology Research Center CO., Ltd. 40-7 Hiromi, Anjo-cho, Anjo-shi, Aichi-ken, Japan 446-0026
2
Taiko Engineering Ltd, Hamamatsu, Shizuoka-ken, Japan
E-mail: altrec-kutsuna@nifty.com

Abstract
One piece type contact tip is now used as contact tip for gas
shielded arc welding. The life time should be improved forautomatic or robotic welding systems. In the present work,
two piece type contact tip was developed to improve thelife time and arc stability. The tip cover and contact tip
unit are also developed for most of the arc welding torch inJapan. Comparing with the life time of a conventional
contact tip, the life time of a developed one is 10 ～20times longer than that of conventional one.
1. Introduction
In gas metal arc welding (GMAW), an electric arc isestablished between a continuously fed consumableelectrode (welding wire) and the work piece. Welding
current is supply from power source to the work piecethrough a contact tip and the electrode in the welding torch.
So, the contact tip is a key component of a welding torch
for stable GMAW process. The contact tip has two mainfunctions. One of them is to feed the current to the workpiece through the electrode which is fed through the tip.
Another one is to introduce welding arc and electrode tip tothe correct position during welding to get stable welding
process, especially in robotic welding. ,The life of contact tip is important in automatic welding,because the changing time of contact tip reduce the arc
time and increases the welding cost. The contact tip shouldhave long life time and lower price.
Then, several
research are reported on a conventional contact tip (onepiece type).
For instance, contact tip wear was studied. If severe wear
is occurred on the contact tip as shown in Figure 1, robotic
welding operation can not continue. Conventional contact
tip should be changed in each several hours. Then, twopiece type contact tip has been developed to solve theproblems. One of the characteristics is long life time andanother one is stable arc phenomena without any troubles.
2. Development of two piece type contact tip
To get a smooth/stable feeding of current from contact tip
surface to electrode surface, low stress was applied to theone end (point C) of contact tip using a small spring in tip
base as shown in Figure 2. Another end (point A) ofcontact tip can be rotated at point B as an axis. Then, thepoint A of contact tip is pushed to the electrode wire
during welding. When a bended electrode wire issupplied, The gap of each contact tip can be expanded.
The applied stress to the contact tip is not increased toomuch. The contact point of electrode is kept always at
the point A. Then, Joule heating may be occurred fromthe point A. the temperature of end of tip is kept lower
comparing with conventional one which has the contact
point inside of tip Then, the wear of tip is not severe,
comparing that of the conventional one.

Figure 2 Cross section of two piece type contact tip(a) Unused contact tip(b) Tip wear after hours
Figure 1 The characteristics of contact tip wear [1]The weight of a developed contact tip is 3.2g. That ofconventional one is 17g as shown in Figure 3. The material
is copper or 3%Cr-Copper. The manufacturing process isdifferent from that of conventional one. In the case oftwopiece type contact tip, Roll forming, stamping and forge
cutting are used for forming. High production rate can beobtained using these forming processes. Figure 4 shows a

type of developed contact tip and contact tip unit for MAG
process using an electrode wire of 1.2mm in dia.

Figure 3: Contact tips (Left: conventional, Right; new one)

10 ～20 times longer than that of conventional tip. It isDue to the no Joule heating before contact of tip at thePoint A.
3) Higher arc stability without feeding hesitation :Resulting in less spatter and good arc starts
4) Good linear adjustment of filler wire to arc location
5) Low price of contact tip :Due to the high production process (forging/stamping)6) Small size and low weight of copper tip:
The weight of 25mm length tip is 3. 2g
and that of 30mm length tip is 4.2g .
4. Evaluation of two piece type contact tip
4.1 Tip wear test in CO2 and MAG welding
Mild steel SS400 plates were welded under the following
Welding conditions using a MG-50 (1.2mm in dia) filler
wire for a long time as shown in Figure 6.
Welding current : 280A ～ 307A.
Arc voltage: 32.7V ～32.9V
Welding speed : 600mm/min
Shielding gas : 100%CO220L/min
or 80%Ar +20%CO2 20L/min
Wire extension : 17mm-19mm
Figure 6 Welding test for contact tip using a robot(a) Tip cover(b) Contact tip(c) Tip base

Figure 4 Developed contact tip and tip units for MAG.
Several types of tip unit which includes tip cover and tip
base has been developed to attach to several type ofwelding torch. in Japan.

.Figure 5

Contact tip unit with a ceramic guide

The size of screw of conventional contact tip is the same asa developed tip unit. So, It is easy to change the contact tipfrom a conventional tip to the developed tip unit as shownin Figure 5..

3. Advantages of two piece type contact tip
The two piece type contact tip has the following features;
1) Excellent current transferability:
The wire contact point is kept at Point A in Figure 2
due to the spring mechanism during welding.
2) Long life of contact tip: The life time of contact tip isFigure 7 Bead appearance of welded plates
Arc time of each test piece was 6 minutes and weld
length was 3.6m each. 120 test pieces were welded in 24hours. The arc time was 12 hours. Tip wear was measured
by a laser microscope as shown in figure 8.

that of two piece type contact tip. In case of CO2 arc
welding, Total groove wear was 57μm after 12 hours ofarc time. Amount of Spatter on nozzle and contact tip wasmeasured each 36 minutes of operation. it was .0187g/min.
Figure 11 shows the photos of welding nozzles. Spatteron the nozzle and tip are a small amount. Color changingofwelding wire occurred from the tip of contact tip as shownin Figure 12. This means Joule heating of wire starts fromthe tip of contact tip. The temperature of wire is not high at
the end of contact tip.

Figure 8 Measurement of tip wear using a laser(a) Before welding(b) After 18 minutes
Figure 11 Photos of Welding nozzles

Figure 9 Measured groove depth of contact tip in MAG
process using a two piece type of contact tip( tip No.6 and No.10 a) Tip of contact tipb) middle point, c) Root of contact tip

Figure 10 Comparison of new tip wear to conventional tip
Figure 9 shows the results of groove depth measurement
after each two hours of arc time in MAG Process.
Measurement error is about ± 15 μ m.
Wear occurs
mainly tip of the contact tip (line a). Total (Tip No.6 andNo.10)
groove wear was 37μm after 12 hours of arc time. In thecase of conventional tip, the groove wear was 263μm
after
2 hours as shown in Figure 10. It was 39 times higher thanFigure 12 Appearance of welding wire and contact tip
after 4 hours welding operation
4.2 Arc stability test in CO2 and MAG welding
For evaluation of arc stability using a two piece typecontact tip, CO2 arc welding and pulsed MAG welding
were conducted using a conventional and a developed
contact tip. DS1A filler wire of 1.2 mm in dia.was used
under the following welding condition;
welding current : 208 A for pulsed MAG
230A for CO2 arc W.
arc voltage: 27V ～ 30 V
travel speed: 50 cm/min
Figure 13 and 14 show the bead appearance in pulsed
MAG Welding using a conventional and a developed
contact tip. The arc starting was excellent. Spatter is moreless on the plate in the case of a developed .contact tip.
Figure 15 shows the spatter on the torch nozzle. Spatter on
The nozzle using a developed contact tip is more less thanthat by a conventional one. In addition, the characteristics
of arc starts was checked. The developed contact tip
showed good arc starts. Nest, the welding current and arc
voltage are recorded during pulsed MAG welding using amemory recorder. The results are shown in Figures 15 and-16.

welding conditions are following;
Filler wire : DS1A 1.2mm in dia.
Wire feeding speed: 767cm/min (for CO2 arc welding)
800cm/min(for Pulsed MAG)
Travel speed: 50cm/min
Base metal: Mild steel (thickness : 9mm)
Figure 13 Bead appearance in pulsed MAG Welding using
a developed contact tip.

Figure14 Bead appearance in pulsed MAG Welding using
a conventional contact tip.

Arc stability in MAG process using a developed
contact tip is better than that using a conventional
one.

Figure 15 Welding current and arc voltage during welding
using a developed contact tip in pulsed MAG

Figure 17 Changing range of welding current in CO2 andpulsed MAGWelding current changes using contact tip in both welding
process are small comparing with that using a conventional
one. This means that arc stability using a developed
contact tip is higher than that using a conventional one.

Figure 18 Tip appearance of two piece typecontact tip after 50 hours in 8 daysin the work shop. (welding current:120A～ 160A)
Figure 18 shows the tip appearance of the developed
contact tip after 50hours operation in 8days. However ,thetip wear is not severe.

5. Application of two piece type contact tip
The applications of two piece type contact tip is the sameas a conventional one. It is also the same as applicationfield of MAG welding process. One of the application
fields is automotive industry. Figure 19 shows example ofparts to be welded using a two piece type contact tip inCO2 arc welding. Motorcycle parts were welded for
50hours in 8days.
Figure 16 Welding current and arc voltage during welding
using a conventional contact tip in pulsed MAG
Figure 17 shows the changing range of welding current
during CO2 arc welding and pulsed MAG welding. The

Figure 19 Motorcycle Parts welded by CO2 arc
welding using a two piece type contact tip.
(Diameter of filler wire : 1.0mm )Conclusion
The two piece type contact tip has been developed for
GMAW process. It has the following features;
1) Excellent current transferability2) Long life of contact tip
3) Higher arc stability without feeding hesitation
4) Good linear adjustment of filler wire to arc location
5) Small size and low weight of copper tip
These characteristics are shown in the welding tests
comparing with a conventional contact tip.
The contact tip unit is also developed for most of the arc
welding torch in Japan. Comparing with the life time of aconventional contact tip, the life time of a developed one is
10 ～20 times longer than that of conventional one.

References[1]

J. Villafuerte, “Understanding Contact Tip Longevity for Gas Metal
Arc Welding," Welding Journal, vol.78, pp. 29-35, Dec. 1999.