GMAW EQUIPMENT, MAINTAINENCE, AND TROUBLESHOOTING 120103C

Question 1

Is it important to have wire guides in alignment with drive rolls on the wire drive unit? Explain your answer.

Answer 1

Yes. Misalignment can cause an unnecessary drag on the wire and lead to feeding difficulties.

Question 2

The installation of the power source must be done with local ______ codes and to be completed by _________ personnel.

Answer 2

The installation of the power source must be done in accordance with local ELECTRICAL codes and to be completed by QUALIFIED personnel.

Question 3

To obtain an accurate reading from a flowmeter, it must be mounted in the:
A) vertical position
B) overhead position
C) horizontal position
D) flat position

Answer 3

A. Vertical position.

Question 4

Why must you ensure that all electrical fittings on the welding leads have a tight connection?

Answer 4

The connections are to be tight to prevent overheating of the cables and power source.

Question 5

The wire spool hub should be adjusted to:
A) prevent the unwinding of the wire spool
B) feed freely, yet prevent a backlash of wire when feeding is stopped
C) allow the wire to be removed without restriction
D) run the wire from the bottom of the roll only

Answer 5

B. Feed freely, yet prevent a backlash of wire when feeding is stopped.

Question 6

How will penetration be affected when stick out is increased?
A) will increase penetration
B) penetration will not be affected
C) will decrease penetration
D) will affect penetration on the welds only

Answer 6

C. Will decrease penetration.

Question 7

Changing the gun (electrode holder) inclination will:
A) change the penetration of the weld
B) have no effect on the weld
C) cause the wire to pile up at the drive rolls
D) cause the wire to feed unevenly

Answer 7

A. Change the penetration of the weld.

Question 8

Describe how GMAW equipment is likely to behave when the contact tip is worn out.

Answer 8

With long use, the wire wears the contact tube orifice to an oval shape. This causes the wire to slide easier, but the transfer of current is not as efficient. Arcing in the contact tube may occur, stopping the wire, or an erratic arc will manifest itself.

Question 9

Excessive spatter buildup in the gun nozzle can cause:
A) undercut at the weld edges
B) excessive metal flow
C) an increase in stick out
D) inadequate gas coverage

Answer 9

D. Inadequate gas coverage.

Question 10

Moisture and dirt on the surface of the wire electrode is likely to cause:
A) porosity
B) cold lap
C) electrical shock
D) post weld stress cracking

Answer 10

A. Porosity.

Question 11

Excessive drag from a dirty liner is likely to cause:
A) porosity and cracking in the weld
B) slippage or bird nesting at the drive rolls
C) excessive undercut or lack of fusion
D) damage to the liner and contact tip

Answer 11

B. Slippage or bird nesting at the drive rolls.

Question 12

When arc hunting occurs, the problem is likely in the:
A) wire feeder drive motor or the motor gearbox
B) wire speed control or the voltage control
C) drive rolls or the remote control switch
D) contact tip or the conduit liner

Answer 12

D. Contact tip or the conduit liner.

Question 13

Stubbing is caused by excessive:
A) inductance
B) voltage
C) resistance
D) wire feed speed

Answer 13

D. Wire feed speed.

Question 14

List four causes of porosity.

Answer 14

A) lack of shielding gas coverage
B) wet CO2 gas
C) excessive tip to work distance
D) excessive travel speed
E) excessive gas flow rates
F) contamination on the base material
G) excessive current or voltage
H) incorrect wire chemical analysis
I) impurities in the base metal such sulphur or phosphorous
J ) plugged gas diffuser orifices
K) loose or off-center gas nozzle

Question 15

What is the major cause of cold lap when using GMAW short-circuit metal transfer?
A) fast travel with a small bead
B) slow travel with a large bead
C) slope control set to a flat volt-amp curve
D) wire stick out too short

Answer 15

B. Slow travel with a large bead.

Question 16

What causes whiskers?

Answer 16

A) too large a root opening
B) a root face that is too thin
C) a too fast travel speed
D) excessive wirefeed speed
E) improper gun manipulation

Question 17

Describe the procedure for clearing a bird nest.

Answer 17

1) De-energize power source/feeder.
2) Cut wire at spool; tie off.
3) Cut wire at back end of cable liner.
4) Remove contact tip; pull wire through gun and cable assembly.
5) Relieve tension on or remove idler rolls.
6) Remove bird nested wire; check for damage to drive roll assembly.
7) Manually feed wire from spool through wire feeder into back of cable liner.
8) Energize power source/wire feeder.
9) Replace drive rolls; set enough pressure to feed wire through to gun.
10) Replace contact tip; check drive roll pressure.

Question 18

How often should you clean the conduit liner of a wire drive set-up?

a) once per day
b) after 20 hours of operation
c) every time the wire spool is changed
d) the liner should never need cleaning

Answer 18

C. Every time the wire spool is changed.

Question 19

Ideally, a welding power source should be located in:
A) a confined area at floor level
B) an uncluttered, well ventilated area of the shop
C) the center area of the shop
D) and unventilated, especially enclosed mezzanine area

Answer 19

B. An uncluttered, ventilated area of the shop.

Question 20

What should you do when the liner becomes kinked?

a) Replace it.
b) Squeeze it in a vice until it straightens out, and place back into service.
c) Cut the kinked portion out, rejoin using manufacturer-approved fittings, and place back into service.
d) Stretch the liner until it straightens out, and place back into service.

Answer 20

A. Replace it.

Question 21

List six (6) things you should you check for if the arc becomes unstable.

Answer 21

a) De-energize power source/feeder.
b) Cut wire at spool; tie off.
c) Cut wire at back end of cable liner.
d) Remove contact tip; pull wire through gun and cable assembly.
e) Relieve tension on or remove idler rolls.
f) Remove bird nested wire; check for damage to drive roll assembly.
g) Manually feed wire from spool through wire feeder into back of cable liner.
h) Energize power source/wire feeder.
i) Replace drive rolls; set enough pressure to feed wire through to gun.
j) Replace contact tip; check drive roll pressure.

Question 22

What part of the GMAW system requires the most ongoing maintenance?

a) power source
b) regulator/flowmeter
c) wire feeder
d) gun and cable assembly

Answer 22

d) gun and cable assembly

Question 23

What can result from a poor work lead connection?

a) Overheating of the power source main transformer coil.
b) Erratic wire feed speeds.
c) Excessive penetration.
d) An unstable arc.

Answer 23

d) An unstable arc.

Question 24

List four (4) things you should check for when you see porosity in the weld when using GMAW.

Answer 24

a) check for empty cylinder,
b) spatter buildup in the gas nozzle,
c) obstructions in the orifices of the gas diffuser,
d) kinked, disconnected or gas line blockages and
e) malfunctioning gas solenoid.

Question 25

What should you check for when adjusting from short-circuiting to spray transfer with GMAW?

a) Ensure wire feeder drive motor is well lubricated.
b) Make sure the power source has a high frequency current control.
c) Make sure the gun is rated to handle higher currents.
d) Make sure the wire electrode is at least 0.9 mm (0.035”) minimum diameter.

Answer 25

c) Make sure the gun is rated to handle higher currents

Question 26

Describe the items you should include on an ongoing maintenance schedule and checklist for wire feed equipment.

Answer 26

You would develop an ongoing maintenance schedule and checklist for wire feed equipment by doing the following.
• Check and follow the equipment manufacturer’s recommendations.
• Arrange with your employer to set a specified time aside for routine maintenance.
• Check the environment around the equipment; harsh environments may require higher maintenance cycles than ideal ones.
• Perhaps recommend additional equipment like spool covers to help keep the wire electrodes clean.
• Put together a mini training program/checklist for the welders to use so they can maintain the equipment themselves.
• Keep a logbook with each equipment set-up to record repairs and completed maintenance activities

Question 27

Describe the procedure for changing a roll of wire on a GMAW system.

Answer 27

a) De-energize power source.
b) Remove empty roll.
c) Remove or relieve tension on idler rolls.
d) Remove contact tip; pull remaining wire through cable assembly.
e) Place new wire spool on hub; check hub brake tension.
f) Feed wire through drive roll assembly and into the liner (ensuring the wire is feeding off the roll straight into the guides).
g) Replace idler rolls; set minimum tension.
h) Re-energize power source/wire feeder; feed wire to gun.
i) Replace contact tip; check and set drive roll pressure.

Question 28

How should you check for correct drive roll pressure on a GMAW set-up?

Answer 28

Drive roll pressure should be set to manufacturer’s recommendations and the tension should be sufficient to drive the wire without undue deformation or scarring of the wire surface.