Nelson NCD+ Instructions for use

© 2016 Nelson Stud Welding, Inc. Page 1
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
Operating the
NCD+Contact Gun
Instruction & Maintenance Manual
These instructions are for experience operators.
If you are not fully familiar with the principles of operation and safe
practices for arc welding equipment, we urge you to read AWS SP –“Safe
Practices” available from the American Welding Society.
Do not permit untrained persons to install, operate or maintain the equipment. Do not
attempt to install or operate the equipment until you have read and fully understand these
instructions.
If you do not fully understand these instructions, contact your supplier for further information. Be sure
to read the Safety section before utilizing this equipment.

© 2016 Nelson Stud Welding, Inc. Page 2
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
NCD+ Limited Warranty
Nelson’s only warranty is that goods being sold will be free from defects in
workmanship and material. This warranty is expressly in lieu of other
warranties, expressed or implied and whether statutory or otherwise,
including any implied warranty of merchantability or fitness for a particular
purpose.
Nelson’s liability for breach of warranty shall arise only upon return of the
defective goods at Buyer’s expense after notice to Nelson of the claimed
breach, and shall be limited to furnishing a like quantity of such goods free
from such defects or, at Nelson’s option, to refunding the purchase price
(less reasonable depreciation based on actual use); provided, however, that
Nelson will not accept receipt of equipment returned unless buyer has
previously afforded Nelson’s personnel a reasonable opportunity to inspect
and repair said equipment at buyer’s facility or such other location as is
mutually agreeable. Notice to Nelson must be given within 30 days of such
defect or failure and within 90 days from the date the equipment was
delivered. No compensation or reimbursement for transportation costs of any
kind will be allowed.
Please note that this warranty does not extend beyond the original
registered purchaser, and does not warrant equipment that has been
modified by any party other than Nelson, or equipment that has been
improperly installed, improperly operated, or misused based upon industry
standards, or equipment which has not had reasonable and necessary
maintenance, or equipment which has been used for operation outside of
specifications for the equipment. Nelson shall never be liable for
consequential damages.
Nelson reserves the right to make engineering and/or part changes, at any
time without notice, as a result of our commitment to continuous
improvement.

© 2016 Nelson Stud Welding, Inc. Page 3
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
WARNING
The following Safety section is for
your protection. It summarizes
precautionary information from
the references listed in the
Additional Safety Information section. Before performing any
installation or operating procedures, be sure to read and follow the
safety precautions listed below as well as all other manuals, material
safety data sheets, labels, etc. Failure to observe these precautions
can result in injury or death.
ELECTRICAL SHOCK
Contact with live electrical parts and ground
can cause severe injury or death. DO NOT use
welding current in damp areas, if movement is
confined, or if there is danger of falling.
Therefore:
1. Be sure the power source frame (chassis) is connected to the
ground system of the input power.
2. Connect the work piece to a good electrical ground.
3. Connect the work cable to the work piece. A poor or missing
connection can expose you or others to a fatal shock.
4. Use well-maintained equipment. Replace worn or damaged
cables..
5. Keep everything dry, including clothing, work area, cables,
torch/electrode holder and power source.
6. Make sure that all parts of your body are insulated from work
and from the ground.
7. Do not stand directly on metal or the earth while working in tight
quarters or a damp area; stand on dry boards or an insulating
platform and wear rubbersoled shoes.
8. Put on dry, hole-free gloves before turning on the power.
9. Refer to ANSI/ASC Standard Z49.1 for specific grounding
recommendations. Do not mistake the work lead for a ground
cable.
PROTECT YOURSELF AND OTHERS
Some welding, cutting, and gouging processes
are noisy and require ear protection. The arc,
like the sun, emits ultraviolet (UV) rays and
other radiation which can harm the skin and
eyes. Hot metal can cause burns. Training in
the proper use of the processes and equipment is essential to
prevent accidents. Therefore:
1. Always wear safety glasses with side shields in any work area,
even if welding helmets, face shields and goggles are also
required.
2. Use a face shield fitted with filter shade #3 per ANSI Z87.1.
Cover sparks and rays of the arc when operating or observing
operations. Warn bystanders not to watch the arc and not to
expose themselves to the rays of the electric-arc or hot metal.
3. Wear flameproof gauntlet type gloves, heavy long-sleeve shirt,
cuffless trousers, high topped shoes, and a welding helmet or
cap for hair protection, to protect against arc rays and hot
sparks or hot metal. A flameproof apron may also be desirable
as protection against radiated heat and sparks.
4. Hot sparks or metal can lodge in rolled up sleeves, trousers cuffs
or pockets. Sleeves and collars should be kept buttoned, and
open pockets eliminated from the front of clothing.
5. Protect other personnel from arc rays and hot sparks with
suitable nonflammable partitions or curtains.
6. Use goggles over safety glasses when chipping slag or grinding.
Chipped slag may be hot and can fly far. Bystanders should also
wear goggles over safety glasses.
ELECTRICAL AND MAGNETIC FIELDS
Electric and magnetic fields may be
dangerous. Electric current flowing through
any conductor causes localized Electric and
Magnetic Fields (EMF). Welding and cutting
current creates EMF around welding cables
and welding machines. Therefore:
1. Operators having pacemakers should consult their physician
before welding. EMF may interfere with some pacemakers.
2. Exposure to EMF may have other health effects which are
unknown.
3. Operators should use the following procedures to minimize
exposure to EMF:
4. Route the electrode and work cables together. Secure them
with tape when possible.
5. Never coil the torch or work cable around your body.
6. Do not place your body between the torch and work cables.
Route cables on the same side of your body.
7. Connect the work cable to the work piece as close as possible to
the area being welded.
8. Keep welding power source and cables as far away from your
body as possible.
FIRES AND EXPLOSIONS
Heat from flames and arcs can start fires. Hot
slag or sparks can also cause fires and
explosions. Therefore:
1. Remove all combustible materials well away from the work area
or cover the materials with a protective nonflammable covering.
Combustible materials include wood, cloth, sawdust, liquid and
gas fuels, solvents, paints and coatings, paper, etc.
2. Hot sparks or hot metal can fall through cracks or crevices in
floors or wall openings and cause a hidden smoldering fire or
fires on the floor below. Make certain that such openings are
protected from hot sparks and metal.
3. Do not weld, cut, or perform other hot work until the work piece
has been completely cleaned so that there are no substances on
the work piece which might produce flammable or toxic vapors.
Do not do hot work on closed containers. They may explode.
4. Have appropriate fire extinguishing equipment handy for instant
use, such as a garden hose, water pail, sand bucket or portable
fire extinguisher. Be sure you are trained for proper use.
5. Do not use equipment beyond its ratings. For example,
overloaded welding cable can overheat and create a fire hazard.
6. After completing operations, inspect the work area to make
certain there are no hot sparks or hot metal which could cause a
later fire. Use fire watchers when necessary.
7. For additional information, refer to NFPA Standard 51B, “Fire
Prevention in Use of Cutting and Welding Processes,” available
from the National Fire Protection Association, Batterymarch
Park, Quincy, MA 02269
FUMES AND GASES
Fumes and gases can cause discomfort or
harm, particularly in confined spaces. Do not
breathe fumes and gases. Shielding gases can
cause asphyxiation. Therefore:
1. Always provide adequate ventilation in the work area by natural
or mechanical means. Do not weld, cut, or gouge on materials
such as galvanized steel, stainless steel, copper, zinc, lead,
beryllium, or cadmium unless positive mechanical ventilation is
provided. Do not breathe fumes from these materials.
2. Do not operate near degreasing and spraying operations. The
heat or arc rays can react with chlorinated hydrocarbon vapors
to form phosgene, a highly toxic gas, and other irritant gasses.
3. If you develop momentary eye, nose, or throat irritation while
operating, this is an indication that ventilation is not adequate.
Stop work and take necessary steps to improve ventilation in the
work areas. Do not continue to operate if physical discomfort
persists.
4. Refer to ANSI/ASC Standard Z49.1 (see listing on next page) for
specific ventilation recommendations.

© 2016 Nelson Stud Welding, Inc. Page 4
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
ELECTRICALLY POWERED EQUIPMENT
Faulty or improperly electrified equipment can
cause injury or death. Therefore:
EYE PROTECTION
Flying metal can injure eyes. Welding, chipping,
wire brushing and grinding can cause sparks
and flying metal. As welds cool, they can throw
off slag. Therefore:
1. Always have qualified personnel perform the installation,
troubleshooting, and maintenance work. Do not perform any
electrical work unless you are qualified to perform such work.
2. Before performing any work inside a power source, disconnect the
power source from the incoming electrical power using the
disconnect switch at the fuse box before working on the
equipment.
3. Install equipment in accordance with the U.S. National Electrical
Code, all local codes and the manufacture’s recommendations.
4. Ground the equipment in accordance with the U.S. National
Electrical Code and the manufacturer’s recommendations.
1. Wear approved safety glasses with side shields even under your
welding helmet.
2. Warn others nearby about flying metal hazard.
EQUIPMENT MAINTENANCE
Faulty or improperly maintained equipment can
cause injury or death. Therefore:
CYLINDER HANDLING
Cylinders, if mishandled, can rupture and
violently release gas. Sudden rupture of
cylinder, valve, or relief device can injure or kill.
Therefore:
1. Always have qualified personnel perform the installation,
troubleshooting, and maintenance work. Do not perform any
electrical work unless you are qualified to perform such work.
2. Before performing any maintenance work inside a power source,
disconnect the power source from the incoming electrical power.
3. Maintain cables, grounding wire, connections, power cord, and
power supply in safe working order. Do not operate any equipment
in faulty condition.
4. Do not abuse any equipment or accessories. Keep equipment away
from:
heat sources such as furnaces
wet conditions such as water puddles and inclement weather
oil or grease
corrosive atmospheres
5. Keep all safety devices and cabinet covers in position and in good
repair.
6. Use equipment only for its intended purpose. Do not modify it in
any manner.
1. Use the proper gas for the process and use the proper pressure
reducing regulator designed to operate from the compressed gas
cylinder. Do not use adaptors. Maintain hoses and fittings in good
condition.
2. Always secure cylinders in an upright position by chain or strap to
suitable hand trucks, undercarriages, benches, walls, post, or
racks. Never secure cylinders to work tables or fixtures where they
may become part of an electrical circuit.
3. When not in use, keep cylinder valves closed. Have valve
protection cap in place if regulator is not connected. Secure and
move cylinders by using suitable hand trucks. Avoid rough
handling of cylinders.
4. Locate cylinders away from heat, sparks, and flames. Never strike
an arc on a cylinder.
5. For additional information, refer to CGA Standard P-1, “Precautions
for Safe Handling of Compressed Gases in Cylinders”, which is
available from Compressed Gas Association, 1235 Jefferson Davis
Highway, Arlington, VA 22202.
ADDITIONAL SAFETY INFORMATION
For more information on safe practices for
electric arc welding, refer to the following
publications.
HEARING PROTECTION
Prolonged Noise from Capacitor Discharge
welding applications can damage hearing if
levels exceed limits specified by OSHA.
Therefore:
1. ANSI/ASC Z49.1 Safety in Welding and Cutting
2. AWS C5.1 Recommended Practices for Plasma Arc Welding
3. AWS C5.6 Recommended Practices for Gas Metal Arc Welding
4. AWS SP Safe Practices (Reprint) Welding Handbook
5. ANSI/AWS F4.1 Recommended Safe Practices for Welding and
Cutting of Containers That Have Held
Hazardous Substances.
1. Use Approved ear plugs or ear muffs if noise level is high.
2. Warn others nearby about noise hazard.
3. For additional information, refer to OSHA Safety Standards 3074.
MOVING PARTS CAN CAUSE INJURY
Electric fan can start at any time without
warning and cause severe injury, therefore:
1. Always disconnect electrical power prior to service to prevent the
fan from starting unexpectedly.
2. Keep all doors, panels, covers, and guards closed and securely in
place.
3. Have only qualified people remove guards or covers for
maintenance and troubleshooting as necessary.
4. Keep hands, hair, loose clothing, and tools away from moving
parts.
5. Reinstall panels or guards and close doors when servicing is
finished and before reenergizing welder.

© 2016 Nelson Stud Welding, Inc. Page 5
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
Contents
1Overview .......................................................................................................................7
1.1.1 Contact Mode Capacitor Discharge Welding ...........................................................8
1.2 NCD+ Contact Guns .................................................................................................8
1.2.1 Operation of the Contact Gun ..............................................................................8
1.2.2 Operation of Contact Gun with LED Option ............................................................8
2LED Option ....................................................................................................................9
3Features ...................................................................................................................... 10
4Gun Set-Up.................................................................................................................. 11
4.1 Setting Up Chuck Assembly.....................................................................................11
4.1.1 Setting Up Chuck ............................................................................................. 11
4.1.2 Adjusting Chuck and Stop Assembly................................................................... 11
4.1.3 Adjusting Stud Stop Assembly ........................................................................... 12
4.2 Setting Up Foot and Leg Assembly ...........................................................................12
4.3 Setting Spring Pressure .......................................................................................... 13
5Weld Setup .................................................................................................................. 14
6Maintenance of Stud Welding System ..............................................................................15
6.1 Stud Welding Gun ..................................................................................................15
6.2 Welding Cable / Control Cable .................................................................................15
6.3 Power Control Unit ................................................................................................. 15
7Troubleshooting............................................................................................................16
7.1 Visual Weld Inspection and Weld Parameter Adjustments............................................16
7.2 Weld Quality Physical Inspection and Weld Parameter Adjustments .............................. 16
7.2.1 Recommendations ........................................................................................... 16
8Exploded Drawings & Parts List ...................................................................................... 19
8.1 Contact Gun (751-650-600) ....................................................................................19
8.1.1 Parts List ........................................................................................................ 19
8.1.2 Exploded Drawing ............................................................................................ 21
8.2 Contact Gun with LED Option (751-650-610)............................................................. 22
8.2.1 Parts List ........................................................................................................ 22
8.2.2 Exploded Drawing ............................................................................................ 24
8.3 Electrical Functions of Guns..................................................................................... 25
8.3.1 Triggering Contact ........................................................................................... 25

© 2016 Nelson Stud Welding, Inc. Page 6
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
8.4 Gun Coding ...........................................................................................................25
8.4.1 Dismantling & Reassembling Welding Guns ......................................................... 25
9Schematics ..................................................................................................................26
9.1 NCD+ CTRL to GUN, 7 PIN, Contact ......................................................................... 26
9.2 NCD+ CTRL TO GUN, 12 PIN W/LED, Contact ............................................................ 28
10 Technical Specifications ............................................................................................. 29
10.1 Specifications ........................................................................................................ 29
10.1.1 Gun Dimensions .............................................................................................. 29
10.2 Accessories ........................................................................................................... 30
11 Contact Information ..................................................................................................31
ATable of Weld Parameters .............................................................................................. 32
BSpring Pressure Chart ................................................................................................... 33

© 2016 Nelson Stud Welding, Inc. Page 7
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
1Overview
The Nelson NCD+ stud welding gun is made to be used with Nelson NCD+ stud welding power
units, which utilize the capacitor discharge principal of stud welding. This system is designed to use
fasteners, which are manufactured with a small projection on the weld end and are welded by the
Contact method. Heat for fusion is obtained from an electric arc, which is established by flashing
away the small projection. The discharge of the welding current or energy stored in the capacitors
produces an arc that melts the end of the stud and a portion of the base material. The stud is
forced into the molten metal before the conclusion of the arc cycle. Upon cooling, a uniform cross
section bond is achieved. A special advantage of the capacitor discharge process is the limited heat
generated, and low penetration which allows the fasteners to be welded to thin and/or coated parts
opposite the weld side.
Contact welding is generally used with carbon steel and stainless steel especially when weld
appearance is not a prime consideration. The contact welding setup is easy and is tolerant to
workpiece flexing.
The welding gun is a “contact gun” which is suitable only for contact welding.
NOTE: Depending upon the weld setup established for any particular stud size or material, the
noise generated by the flashing away of the stud tip may exceed the allowable level established by
the Occupational Safety and Health Administration (Section 50-204.10 of the Federal Register, Part
II). For this reason, it is recommended that the stud welding operator and anyone working within
the immediate area of the stud welding operation use proper ear protection.
SAFETY SYMBOLS
ATTENTION! BE
ALERT! Your
safety is involved.
Used to call attention to immediate hazards which,
if not avoided, will result in immediate, serious
personal injury or loss of life.
Used to call attention to potential hazards which
could result in personal injury or loss of life.
Used to call attention to hazards which could
result in minor personal injury.

© 2016 Nelson Stud Welding, Inc. Page 8
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
1.1.1 Contact Mode Capacitor Discharge Welding
1.2 NCD+ Contact Guns
This manual covers the NCD+ welding gun series including the Contact gun and the Contact gun
with the LED Option. These guns are very similar from the outside, however they are not
interchangeable. Each gun has its own specific mode of welding studs. The internal parts that are
different will be identified so you can easily determine which gun you have.
1.2.1 Operation of the Contact Gun
The NCD+ Contact Gun is a capacitor discharge contact gun. Since there is no coil, there is only
one wire that goes to the trigger. The other side of the trigger goes to the foot assembly. When the
trigger is pulled, the capacitors discharge as the stud is held firmly against the workpiece. The tip is
flashed off allowing the arc and stud plunge.
1.2.2 Operation of Contact Gun with LED Option
The LED option provides the user with remote indication of whether or not the unit is ready to weld
and after the weld if the measured values were within the selected weld parameters.

© 2016 Nelson Stud Welding, Inc. Page 9
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
2LED Option

© 2016 Nelson Stud Welding, Inc. Page 10
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
3Features
Figure 3.1 Contact Gun
Refer to Setting Up Foot and Leg Assembly.
1
CHUCK NUT
6
LEG SCREWS
2
TRIGGER
7
SPRING PRESSURE GAUGE
3
CONTROL CABLE
8
SPRING PRESSURE ADJUSTMENT
4
WELD CABLE
9
GUN BODY (2 HALVES)
5
LED STATUS

© 2016 Nelson Stud Welding, Inc. Page 11
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
4Gun Set-Up
4.1 Setting Up Chuck Assembly
The unit should be switched off before inserting or changing a chuck.
4.1.1 Setting Up Chuck
At the beginning of a welding series or in case of a necessary change to different stud dimensions,
the chuck must be set to the correct stud type.
The chucks (Figure 4.1 Chuck and Stop Assembly) are not included and should be ordered
separately. See Accessories for correct sizes and part numbers.
Job Preparation
Tools Required: Screwdriver, open-end wrench (7mm, 8mm), and caliper gauge
1Select chuck with the correct diameter for the stud to be welded.
2Stop pin assembly for the proper stud length.
4.1.2 Adjusting Chuck and Stop Assembly
The unit should be switched off before inserting or changing a chuck.
To adjust the Chuck and Stop Assembly (Figure 4.1 Chuck and Stop Assembly):
The proper size chuck for the type of stud being welded must be used to ensure good electrical
contact between the stud and the stud chuck. If the stud fit seems too loose with the proper chuck,
the chuck tines may be pressed slightly together at the front end of the chuck.
NOTE: There must be good
electrical contact between the
stud to be welded and the stud
chuck. It may be useful to
press the tines of the chuck
together slightly at the front.
NOTE: During welding, it is very
important to draw the chuck
(gun) straight off the stud after
a weld has been made to avoid
spreading the chuck tines. If
this procedure is not followed,
chuck life may be substantially
shortened.
Figure 4.1 Chuck and Stop Assembly

© 2016 Nelson Stud Welding, Inc. Page 12
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
4.1.3 Adjusting Stud Stop Assembly
1Loosen the set screw.
2Adjust the stud stop (Figure 4.1 Chuck and Stop Assembly) so that the stud being welded
extends 4 mm beyond the chuck.
3Tighten set screw.
NOTE: For long studs, use maximum chuck depth. The chuck is assembled as shown and inserted
into the chuck adaptor. The chuck must be in firm contact with the stud stop while tightening the
chuck nut.
4.2 Setting Up Foot and Leg Assembly
The NCD+ guns come supplied with a foot and spark shield (Figure 4.2 Foot & Leg Assembly). The
foot is installed on the end of the legs. Alignment of the foot is important. The chuck should be
located in the center of the spark shield. To install the foot, unscrew the leg screws and place them
through the holes in the foot. Reattach the leg screws to the legs. Maintain concentricity between
the chuck and spark shield.
Figure 4.2 Foot & Leg Assembly

© 2016 Nelson Stud Welding, Inc. Page 13
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
4.3 Setting Spring Pressure
Required tools: NCD+ Weld gun, chuck and foot per application, NCD+ Set-Up Tool (Figure 4.3
Contact Gun with NCD+ Set-Up Tool #525-001-200) or flat bladed screwdriver
1Check Appendix B Spring Pressure Chart for the recommended spring pressure.
2With a flat bladed screwdriver or NCD+ Set-Up Tool, turn adjustment screw on the back of the
weld gun to the recommended spring pressure.
3Adjust stud stick out.
4Loosen leg screws.
5Insert stud in chuck
6Place NCD+ Set-Up Tool on a flat surface and insert stud into Contact Mode hole.
7Do not compress the spring.
8Adjust foot until tripod foot or spark shield are flat on top of NCD+ Set-Up Tool. Do not insert
tripod standoffs into holes on tool.
9Tighten leg screws to lock tripod foot or spark shield in place.
Figure 4.3 Contact Gun with NCD+ Set-Up Tool #525-001-200

© 2016 Nelson Stud Welding, Inc. Page 14
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
5Weld Setup
1Confirm that the unit is switched off.
NOTE: Combo cable is normally used with the Contact mode.
2Connect gun, combo cable and ground cables to the appropriate terminals.
3Determine initial weld parameters in the Table of Weld Parameters.
4Adjust voltage.
5Install chuck and stud stop.
6Adjust gun spring pressure.
7Adjust plunge.
Plunge is the distance the stud extends beyond the stand-off posts (or spark shield). Loosen the leg locking
screws and adjust the plunge to approximately 3mm and retighten the leg locking screws.
8Switch the power unit on.
9Check concentricity of chuck and spark shield.
10 Begin production welding after samples weld have been validated for strength and appearance.
11 For finer contact gun adjustments, refer to Error! Reference source not found..

© 2016 Nelson Stud Welding, Inc. Page 15
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
6Maintenance of Stud Welding System
A majority of the maintenance of a stud welding system is in:
1Stud Welding Gun
2Welding Cable / Control Cable
3Power Control Unit
6.1 Stud Welding Gun
The weld tool carries out most of the welding functions and should be periodically (at least every 3
months) disassembled and cleaned. Special attention should be given to the spring mechanism.
This shaft must be absolutely free with no binding inside the gun and there should be no contact
between the stud and the spark shield. Never lubricate the spring mechanism. It should be cleaned
with a dry cleaner such as electrical contact cleaner. Caution should also be exercised when
reassembling the gun to be certain not to pinch wires or the weld cable. This could cause erratic
welding problems which are usually difficult to isolate.
6.2 Welding Cable / Control Cable
When checking cables for continuity, it is important to slightly pull on all the connectors so that if
there is a break, the wires will be pulled apart. The continuity check can be performed with a
standard Ohm meter. All cables: ground, control and the weld cables should be periodically
inspected.
6.3 Power Control Unit
The power control unit contains electronic control boards. Normally, these items do not require
maintenance. However, in harsh environments, particularly those with grinding or sanding, metallic
dust can enter the welder. This conductive metallic dust can cause unexplained problems with the
welding system. Periodically removing the power control unit cover and blowing out the power
control unit is a good idea. Frequency will vary depending on the environment. Always disconnect
power before opening any power control unit. CD units will continue to store energy after they
have been unplugged. To ensure all energy is discharged, wait at least one minute before removing
cover and servicing the power control unit. Use voltmeter to check voltage between (+) & (-) grid
for 0 Volts.

© 2016 Nelson Stud Welding, Inc. Page 16
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
7Troubleshooting
7.1 Visual Weld Inspection and Weld Parameter Adjustments
Issue:
Cold Weld
Issue:
Acceptable Weld
Issue:
Hot Weld
Figure 7.1 Weld Quality Visual Inspection
7.2 Weld Quality Physical Inspection and Weld Parameter Adjustments
If visually inspecting the welds reveals a questionable weld, the weld should be physically tested.
Initial weld set ups should also be physically tested.
Suggested physical tests for steel and stainless steel studs are as follows:
1Bend Test. Stud to be tested shall be bent away from its vertical axis 90° or until failure.
Failure should occur in the stud proper, or, on thin plate, a full stud diameter plug of base
metal should be torn out.
2Torque Test. Stud shall be torqued until a pre- specified loading is attained or until the stud
fails or, on thin plate, a plug of the base material should tear out.
Physical test procedures for inspecting (magnesium) aluminum alloy studs are:
3Bend Test. The stud to be tested shall be bent, using a bending tool approximately 15° away
from its vertical axis before the stud breaks in the weld shank or the base material fails.
NOTE: Do not bend aluminum studs by striking with a hammer, always use a bending tool.
4. Torque Test. The stud to be tested shall be torqued in the conventional manner by applying torque
until the stud fails or a predetermined torque load is reached.
7.2.1 Recommendations
Before starting any stud welding operation, or after the equipment has remained idle for a period
of time, trial or test studs should be welded to a plate for testing. Testing should continue until
there is no failure of a test stud.

© 2016 Nelson Stud Welding, Inc. Page 17
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
Weld Issue
Weld Parameter Adjustments
Cold Weld
Weld failure at low value, no weld
flash or splatter, and weld base is
incompletely melted (very weak
weld). This indicates that not enough
heat was available.
Weld heat may be increased by:
Reducing spring pressure - Reducing the drop speed and provides
a longer weld time.
Increasing voltage - Increasing the voltage increases overall
energy into the weld.
Check stud ignition tips (possibly too short).
Hot Weld
Weld failure at low value, excessive
weld flash and splatter, and weld base
may be undercut (weak weld). This
indicates that too much heat was
available.
Weld heat may be decreased by:
Increasing spring pressure - Speeding up the weld time and
extinguishes the arc sooner.
Decreasing voltage - Reducing the voltage reduces overall energy
into the weld.
Check stud ignition tips (possibly too long).
Late or Cold Plunge
Cold plunge occurs when the stud
contacts the base material after
solidification of the molten weld metal
has started. This results in
inconsistent weld strength and is
recognized by a shiny, mirror-like
appearance in the fracture surface.
This issue can be rectified by:
Increasing spring pressure - Increasing drop speed and gets the
stud into the molten pool faster.
Decreasing voltage - Reducing the voltage reduces overall energy
into the weld.
Make certain that combo cable is installed (contact mode only).
Otherwise (if gap mode), remove combo cable - Reducing the
amount of weld energy flowing especially in gap mode because of
the high current spike.
Misfire
No arc initiation due to tip failing to
flash.
This issue can be rectified by:
Increasing voltage.
Using 10% detergent solution spray mist.
Problem: Cold Weld
Possible Causes
Possible Solutions
Coiled weld or ground cables. This
reduces weld current delivered to the
stud. The coiled cables act like a large
inductor and inhibit the flow of
energy.
Ensure weld and ground cables are not coiled during the stud welding
process.
Improperly set power supply controls.
Refer to the Section 3 Normal Operation within the Operating the
Capacitor Discharge NCD+ Stud Welding Unit manual.
Improperly formed tip on stud due to
manufacturing process.
Replace stud with one that is correctly formed.
Changes in alloys being welded.
Changes in alloys can usually be compensated for by changing the
settings on the power supply.
Equipment failure.
Refer to the Section 3 Normal Operation within the Operating the
Capacitor Discharge NCD+ Stud Welding Unit manual.
Varying gauges of sheet metal.
Changes in sheet metal can usually be compensated for by changing
the settings on the power supply.
Springs inside weld tool have fatigued
and don’t apply the same pressure.
Return weld tool to Nelson for service.

© 2016 Nelson Stud Welding, Inc. Page 18
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
Dirt inside weld tool prevents smooth
operation and hangs up or slows gun
operation.
Return weld tool to Nelson for service.
Problem: Arc Blow
Characterized by weld spatter of fillet on only one side of the stud (looks like molten metal was “blown” out
from only the one side of the stud). This problem will often cause incomplete fillet formation on one side of the
stud. This incomplete cross sectional welding may lead to weld failure.
Possible Causes
Possible Solutions
Molten metal runs away from the
ground. Incomplete or insufficient
grounding can cause this problem.
Double Ground. The addition of another ground on opposite sides of
the weld area will reduce this problem. The object will be to always
weld between the grounds. If you need assistance contact your
Nelson Representative.
Welding near the edge (1/4 inch or
less) of a piece of metal will
potentially cause these phenomena.
Unusual electrical current patterns are
set up near the edges of metals and
this can affect the flow of metal.
Place another piece of sheet metal of the same type and thickness
next to the edge you are welding. This will “fool” the electrical
currents and they will act like you are welding in the middle of the
sheet metal.

© 2016 Nelson Stud Welding, Inc. Page 19
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
8Exploded Drawings & Parts List
8.1 Contact Gun (751-650-600)
8.1.1 Parts List
ITEM
PART NUMBER
QTY
DESCRIPTION
SPARE?
1
D 751-650-001
1
BODY, GUN, RIGHT
2
D 751-650-002
1
BODY, GUN, LEFT
3
A751-650-003
1
COVER, FRONT
4
A751-650-005
1
CAP, REAR
5
A751-650-006
1
BEARING, FRONT
6
A751-650-007
1
BELLOWS
7
A751-650-008
2
WASHER, LEG
8
A751-650-009
1
NUT, CHUCK
9
A751-650-012
3
PIN, LOCATING
10
A751-650-101
1
ROD ASM, LIFTING
11
A751-650-104
1
BEARING RETAINER
12
A751-650-019
1
SPRING, RETAINER
13
A751-650-020
1
NUT, ADJUSTING, SPRING
14
A751-650-021
1
SCREW, ADJUSTING, SPRING
15
A751-650-022
1
WASHER, FLAT, M4
16
A751-650-211
1
SWITCH ASM, TRIGGER
17
A751-650-027
1
TRIGGER
18
A751-585-021
1
RING, RETAINING
19
87-05-22
1
SPRING, TRIGGER
20
A720-517-000
1
JUMPER, CABLE, WELD
21
524-005-097
4
SCREW, FPS, M5 X 5 LG
22
524-005-007
2
SCREW, SS, M8 X 8MM LG
23
511-001-131
1
SPARK SHIELD
24
524-005-100
3
SCREW, OHM, M4 X 16MM LG
25
524-005-101
2
SCREW, FHSC, M5 X 16MM LG
26
524-005-102
1
SCREW, FHSC, M4 X 12MM LG

© 2016 Nelson Stud Welding, Inc. Page 20
All Rights Reserved. January 2016 Part No. 729-110-043 Rev. 1.02
ITEM
PART NUMBER
QTY
DESCRIPTION
SPARE?
27
524-005-104
1
NUT, THICK, M5
28
524-005-105
1
SCREW, SHC, M5 X 10MM LG
29
524-005-003
1
SCREW, SS, M4 X 6 LG
30
729-023-017
1
WASHER, SPRING, CONICAL, MS
31
A726-013-002
1
COLLET
32
526-001-231
1
SPRING, MAIN
33
A502-001-261
1
FOOT
34
A504-001-056
2
LEG
35
527-003-094
1
BEARING
36
524-005-103
2
SCREW, LHC, M3 X 5MM LG
37
729-023-025
1
PIN, GROOVED, 3MM X 6MM LG
38
713-032-000
4
WIRE SPLICE
39
751-585-004
1
WELD CABLE GROMMET
40
721-268-011
1
CONTROL CABLE, 12 PIN
X
41
720-519-081
1
WELD CABLE
X
42
526-001-232
1
SPRING, GROUND SENSE WIRE
X
Additional Parts Needed for Repair
Part Number
Qty
Description
524-005-106
1
M5x25 FHSHCS