Livingston & Company WELDWISE 2400 User manual

Revision C.001
Use
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WeldWise 2400
THE WELD MONITORING SPECIALIST
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0453-INS-400 Rev. F
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Disclaimer
Livingston & Company makes no warranty of any kind with regard to this material, including, but not
limited to, implied warranties of merchantability and fitness for a particular purpose.
Livingston & Company shall not be liable for errors contained herein or for incidental consequential
damages in connection with the furnishing, performance or use of this material.
Copyright
This document contains proprietary information that is protected by copyright. All rights are reserved.
No part of this document may be photocopied, reproduced or translated to another language without
the prior written consent of Livingston & Company. The information contained in this document is
subject to change without notice.
© 2007 Livingston & Company
All rights reserved.

ii 0452-INS-400 Rev. C
Product Road Map
The Livingston User's Manual includes the following sections:
• Overview of Resistance Welding: Explains the fundamentals of resistance welding and factors
that affect the quality of resistance welds
• Introduction to Resistance Weld Monitoring: Explains the fundamentals of resistance weld
monitoring and reasons for weld monitoring
• Tolerancing & Monitoring: Describes Livingston's concept of resistance weld monitoring and
terminology used regarding Livingston equipment
• Getting Familiar With the WeldWise™ 2400: A brief physical overview of navigating with the
software
• WMS Quick Start: A basic how-to guide to weld monitoring with Livingston equipment
• WMS Reference Guide: A complete software reference to the Livingston Weld Monitoring
Software (WMS) program
• Installing the Sensors: Describes the various types of sensors available for use with Livingston
weld monitors and installation guidelines
• Calibrating the Sensors: Explains how to calibrate sensors using the WMS program
• FAQ: Includes answers to frequently asked questions
• Troubleshooting Guide: A beginner's guide to basic troubleshooting for Livingston systems
• Appendices: Includes information reprinted from the RWMA, and various subject matter
pertaining to both Livingston equipment and software.
• Application Notes: Includes general 'how-to' procedures and notes relating to software and/or
hardware issues
• Contact Information: How to reach Livingston

0427-INS-400 Rev. D iii
Table of Contents
OVERVIEW OF RESISTANCE WELDING 1
INTRODUCTION 1-1
VARIABLES IN THE WELDING PROCESS 1-2
THEWELDCYCLE 1-2
CRITICALFACTORSINWELDING 1-3
CURRENT 1-3
VOLTAGE 1-3
POWER 1-4
RESISTANCE 1-4
ELECTRODES 1-4
SURFACECONTACT 1-6
CURRENTDENSITY 1-6
OHM'S LAW AND JOULE'S LAWS 1-7
IDENTIFYING AND CORRECTING WELD PROBLEMS 1-8
RECOMMENDATIONS FOR PRODUCING QUALITY WELDS 1-9
AVOID THESE POTENTIAL SOURCES OF WELD PROBLEMS 1-10
INTRODUCTION TO RESISTANCE WELD MONITORING 2
INTRODUCTION 2-1
WHYMONITOR? 2-1
WELD LOBES AND THE WELD PROCESS 2-2
STYLES OF MONITORING 2-2
BEFORE & AFTER MONITORING 2-2
MASSMONITORING 2-3
DYNAMIC MONITORING 2-3
EFFECTS OF DIFFERENT FACTORS 2-4
HOWMONITORSWORK 2-5
MOREBENEFITS 2-5
TOLERANCING AND MONITORING 3
INTRODUCTION 3-1
LIVINGSTON WELDWISE MONITOR 3-1
SIGNATURES&MASTERS 3-1
TOLERANCES 3-2
MEASUREDPARAMETERS 3-3
SEGMENTS 3-3
DATA COLLECTION 3-4

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GETTING FAMILIAR WITH THE
WELDWISE™ 2400 4
THEFRONTPANEL 4-1
WMS NAVIGATION AND EDITING 4-2
NAVIGATION 4-2
EDITING 4-2
OTHERBUTTONS 4-3
THEBACKPANEL 4-4
PROPER SHUTDOWN PROCEDURE 4-5
WMSQUICKSTARTGUIDE 5
GENERALSETUP 5-1
GATHERINGDATA 5-2
CREATINGAMASTER 5-7
ACCEPTING / REJECTING WELDS 5-8
TOLERANCING 5-10
SUMMARY 5-11
WMSREFERENCEGUIDE 6
MAINPROGRAMSCREEN 6-1
MAINMENUOPTIONS 6-4
DATAMENUOPTIONS 6-5
HALFCYCLE SUMMARY SCREEN 6-6
WELD SUMMARY SCREEN 6-11
SYSTEMLOGSCREEN 6-12
DATABASE MANAGEMENT 6-13
DATABASE IMPORT SCREEN 6-16
DATABASE EXPORT SCREEN 6-18
SCOPEDATASCREEN 6-20
MASTERINGSCREEN 6-21
EDITMASTERSCREEN 6-24
TOLERANCINGSCREEN 6-25
SETUPMENU 6-30
GENERALSETUP 6-31
SETUPUTILITIES 6-38
INPUTMONITOR 6-39
TOROID SETTINGS UTILITY 6-40
VOLTAGE CALIBRATION UTILITY 6-41
FORCE CALIBRATION UTILITY 6-42
DISPLACEMENT CALIBRATION UTILITY 6-43
TOLERANCE DEFAULTS SETUP 6-44

0427-INS-400 Rev. D v
GRAPHSETUP 6-45
SHUTDOWNMENU 6-46
INSTALLINGTHESENSORS 7
TYPESOFSENSORS 7-2
CURRENT 7-2
VOLTAGE 7-2
FORCE 7-2
DISPLACEMENT 7-3
INSTALLING THE CURRENT TOROID 7-4
INSTALLING THE VOLTAGE LEADS 7-5
INSTALLING THE FORCE SENSOR 7-6
INSTALLING THE DISPLACEMENT SENSOR 7-7
TESTING SENSOR INSTALLATION 7-8
CALIBRATINGTHESENSORS 8
IMPORTANTNOTES 8-1
FREQUENCY OF CALIBRATION 8-1
THEINPUTMONITOR 8-2
INSTALLING/SWAPPINGTOROIDS 8-3
PERCENTAGEADJUSTMENT 8-4
CALIBRATING DISPLACEMENT 8-5
ZEROINGTHEDISPLACEMENT 8-5
CALIBRATING FORCE 8-6
CALIBRATING VOLTAGE 8-8
FREQUENTLY ASKED QUESTIONS 9
TROUBLESHOOTING GUIDE 10
APPENDICES 11
WMSROADMAP 11-1
RECOMMENDED DATABASE MANAGEMENT 11-2
IMPORTING/EXPORTING TABLES 11-8
DISPLACEMENT CHANNEL OVERVIEW 11-10
SENSOR CALIBRATION UTILITIES OVERVIEW 11-11
IDENTIFYING AND INTERPRETING STATUS CODES 11-12
ATTACHING PERIPHERALS 11-14
INTERLOCK INTERFACE 11-18
BINARY SELECT & ACCEPT/REJECT TIMING 11-19
WELDWISE™ 2400 SPECIFICATIONS 11-20

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COMMON USES OF RWMA MATERIAL 11-21
WARRANTY & REPAIR POLICY 11-23
APPLICATIONNOTES 12
APP NOTE 118 – Changing WeldWise™ 2400 Identification and IP address 12-1
APP NOTE 121 – Copy weld data and use it to create an MS Excel chart 12-7
APP NOTE 307 – Replacing a Pod 12-21
CONTACTINFORMATION 13

0428-INS-400 Rev. E 1-
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Overview of Resistance Welding
Introduction
In simplest terms, welding is a process by which two or more pieces of metal are joined by applying
heat and pressure. Back in the good old days, blacksmiths and other crafty people would heat metals in
a furnace and then weld them by hammering the red-hot metals together. By hammering the metals as
they cooled, the weld would be made stronger. This heating-and-hammering method is known as forge
welding. While forge welding worked quite well for most of the welding done back then, today's
welding requirements are a bit more advanced. After all, it would be pretty difficult to heat all the
metal needed to build an automobile in a big factory furnace and expect workers to hammer together
each specific part used in the manufacturing process. We'd all still be riding horses to work!
Fortunately, there are always a handful of brilliant people throughout history who are kind enough to
invent newer, faster, and better ways of doing things. One of these people was a professor by the name
of Elihu Thompson. Sometime in the year 1885, Professor Thompson invented a process called electric
resistance welding. He discovered that to weld metals together, one could fire an electric current
through the metals while they were tightly clamped together. When the current passed through the
metals, it would create such a high heat that the metals would melt and run together and a weld would
be made. Many times, the welded metal would be even stronger than the original metals used in the
welding process.
Today's resistance welders work almost exactly the same way they did when Thompson invented the
process. The current is generated by a transformer, and is fired through electrodes, which hold the
metal pieces in place. These electrodes also apply force to the metal pieces, usually before, during, and
after the firing of the electric current. This method is called resistance welding because it is the
resistance between the contact surfaces of the metals being welded that generates the heat to fuse them
together.
Resistance is the opposition that a substance offers to the flow of electric current. The less resistance a
metal has, the less heat is generated when current passes through it. Conversely, the higher the
resistance of a metal, the more heat is generated when that same current passes through it. This
behavior can be paraphrased as follows: the heat is where the resistance is, and the resistance is where
the heat will be. Obtaining the best results in resistance welding requires a thorough understanding of
the materials being welded, careful control of the heat and pressure at the weld point, and consideration
of numerous other factors. This chapter will deal with the basics of resistance welding, the variables
involved, and why they're so important to the welding process.

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Variables in the Welding Process
The many variables involved in welding can be broadly categorized into two basic sections: process
variables and material variables.
Process variables include: Material variables include:
• Weld current • Coating thickness and type
• Squeeze time • Part fit-up
• Weld time
• Hold time
• Surface condition & cleanliness of
materials
• Electrode force
• Design of the electrode
• Workpiece material
The Weld Cycle
A typical resistance weld is broken down into several distinct periods, as shown in figure 1-1 below:
The Squeeze Time is when the weld heads (electrodes) come together and build up to a specified
amount of force before the current is fired.
The Weld Time is when the current is actually passing through the workpieces. This is when the
metals are being heated enough to melt and fuse together to form what is called a weld nugget.
Figure 1-1 A typical weld cycle

0428-INS-400 Rev. E 1-
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During the Hold Time, electrode force is still applied, even after the weld current has ceased. During
this period, the weld nugget cools and the metals are forged under the force of the electrodes. The
continuing electrode force helps keep the weld intact until it solidifies, cools, and the weld nugget
reaches its maximum strength.
Critical Factors in Welding
Understanding the resistance weld process requires an understanding of the main factors involved and
how they work together. This section will review current, voltage, resistance, and power, as well as the
various functions of the electrodes and how they affect surface contact and current density.
Current
Current, usually measured in Kilo-Amperes (KA — one Kilo-Amp is equal to 1,000 Amps), is one of
the most important factors. A resistance weld cannot be made unless there is sufficient weld current.
According to the RWMA, the typical amount of current needed to weld low-carbon steel, for example,
is about 10,000 Amps (10 KA) at about 5 Volts. To put this in perspective, a normal household or
office outlet provides a maximum of 15-20 Amps (0.015-0.020 KA) at 120 Volts, while a power
circuit in a factory may only be capable of providing 200 Amps (0.200 KA) at 500 Volts to a welder.
The factory's 200 Amps is then converted to the 10,000 Amps needed to weld by means of a welding
transformer.
A transformer consists of two coils of wire, called the primary and the secondary, wound around an
iron core. Power is transferred from primary to secondary via the magnetic properties of the iron. The
factor by which the current and voltage is stepped up or down is equal to the ratio between the number
of turns of wire in the coils forming the primary and secondary windings of the transformer. Consider
the steel that needs 10,000 Amps (10 KA) of current to be welded in a factory that can only provide
200 Amps (0.200 KA). If the welding transformer had 100 turns on the primary and 2 turns on the
secondary, the 'turns ratio' would be 100 to 2, or more simply, 50 to 1. The 200 Amp current in the
primary would then be converted (stepped up) to 10,000 Amps (200 Amps x 50 turns = 10,000 Amps)
in the secondary, which would yield enough amperage to make a weld.
Voltage
If current is the amount of electricity flowing, then Voltage (measured in Volts) is the pressure or force
that's causing the flow. A good analogy is water flowing through a pipe. A larger voltage will result in
greater water pressure, which will cause more water (current) to flow through the pipe. Using the
transformer example above, after the 200 Amps at 500 Volts on the primary passes through the
transformer coils, the secondary amperage increases to 10,000 Amps, but the voltage actually drops to
10 Volts. This decrease in voltage occurs because the amount of power coming out of a transformer
isn't actually increased, but more accurately exchanged.

0428-INS-400 Rev. E
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Power
Power is Voltage multiplied by Current, and is measured in Watts, or KVA (KVA stands for Kilo-
Volt-Amperes. Watts and KVA will be used interchangeably in this text). This means that the amount
of current flowing times the pressure that's causing it to flow equals the amount of power generated. A
basic law to bear in mind is that the power going into a transformer will always equal the power
coming out of it. Returning to the transformer example, 200 Amps coming in at 500 Volts (200 x 500
= 100,000 KVA) on the primary with a 50 to 1 turns ratio in the transformer will be converted into
10,000 Amps at 10 Volts (10,000 x 10 = 100,000 KVA) going out. As the math illustrates, the results
are the same. The initial and final amperage and voltage may be different, but because the ratio is the
same, the total amount of power is also the same.
Resistance
As mentioned earlier, resistance is defined as the opposition that a substance offers to the flow of
electric current. Resistance is calculated by dividing the Voltage by the Current, and is measured in
Ohms. (When written, Ohms are represented by the Greek letter Omega: Ω). Since resistance to the
current is what generates the heat in the workpiece, it is critically important that the area with the
greatest resistance be at the interface between the two parts being joined. This interface is also known
as the faying surfaces. Remember that the heat is where the resistance is, and the resistance is where
the heat will be. If the area with the most resistance is, for example, where the lower bus bar connects
to the transformer of the welder and not at the faying surfaces of the workpieces, then that's where the
heat will go. Likewise, if the greatest resistance is at the contact area between the electrode tip and the
workpiece, the heat generated there will cause the tip to weld directly to the workpiece.
Electrodes
Typically made of copper alloys, electrodes actually have three separate functions: to conduct current
to the workpieces being welded, to transmit the proper pressure or force to those workpieces to
produce and forge a good weld, and to help dissipate heat from the area being welded. To ensure that
all three of these functions are executed properly, it is important to regularly maintain the electrodes,
keeping them clean and in good condition. A reprint of an RWMA chart describing various types of
electrode materials and their different uses may be found in Chapter 11, APPENDICES, of this
manual.
Conducting Current
The first of these functions is purely electrical— fire weld current through the workpiece. Taking into
account the relationship among current, voltage and resistance, it becomes important to pay attention to
the type of electrodes used. For example, it wouldn't be wise to select electrodes made entirely from a
high resistance material, since they would get so hot they'd melt before the current even had a chance
to flow to the workpiece. It is also important to make sure that the electrodes are the right size for the
application; proper electrode sizing is largely dependent on the amount of force being used on the
workpieces.
Transmitting Force
The second function of the electrodes is mechanical. The amount of force needed to make a good weld
varies, depending on the type of metal being welded and other factors, but a general figure would be
about 600-800 lbs. Because electrodes are typically on the small side— roughly from about the size of

0428-INS-400 Rev. E 1-
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an acorn to the size of a plum, it is also important to choose electrodes that are able to withstand the
force needed to make a good weld.
A key point to understand is that force and resistance have an inverse relationship: more force will
result in less resistance, and vice-versa. The equation has to do with surface contact, which refers to the
specific area on the workpieces touched by the electrodes. Surface contact will be covered further in
the next section, but the following example will begin to illustrate this relationship: if you examine
your fingertip under a magnifying glass, what first appears to be a smooth surface is actually a mass of
rough-looking ridges and bumps. The same is true of electrodes and workpieces. The tips of the
electrodes and the surfaces of the workpieces may look to be smooth and in good condition, but in
reality their surfaces are quite rough, especially if the electrodes are old and worn or if the workpieces
are dirty. By applying pressure to these rough surfaces, any microscopic inconsistencies (e.g., dirt or
grease on the workpiece and/or pits and cracks in the electrodes) are compressed and the surface
actually evens out. This results in improved (increased) surface contact between the electrode tips and
the workpiece, and between the workpieces themselves. When the surface contact is increased, current
can flow more readily from the tips through the workpieces, which means that the resistance has been
lowered.
Force also is what helps to keep the weld intact as it's being formed. As the current generates heat, the
workpiece metal begins to melt. A good analogy to this process is a child eating a popsicle on a hot
summer day. When the popsicle melts, it doesn't remain on the stick―it drips everywhere. When
metal melts it wants to do the same thing, however because it's molten metal and not a runny popsicle,
it doesn't simply drip. It explodes out of the workpiece. This is why proper weld force is so important:
it literally forces the molten metal to stay put, so it can then cool to form a weld nugget. Without
sufficient force, the metal will do what it wants to do, which is what causes expulsion. Expulsion is
nothing more than little pieces of molten metal exploding out of the weld because they're not being
properly held in. The problem with expulsion is that all the metal flying out of the weld is metal that's
not going in to the weld; a weld cannot be made stronger by removing metal from it. Determining the
proper amount of force is entirely application dependent. The RMWA can be contacted for additional
recommendations and guidelines.
Cooling the Workpiece
Electrodes get considerably hot with 10-20 KA or
more repeatedly flowing under hundreds of pounds
of force. Although most welders have an internal
water cooling system that allows water to circulate
through the tips of the electrodes while welds are
being made, a common problem is a lost, damaged or
improperly sized cooling water tube. Without
anything to cool off the tips, heat can quickly build
up to the point where the electrodes will eventually
weld to the workpieces. To correct this problem, the
water tube should be placed so that the incoming
cold water strikes the hottest part of the tip first, as
shown in figure 1-2. Figure 1-2 Example of an electrode cooling
channel.

0428-INS-400 Rev. E
1-6
Surface Contact
The ultimate goal of the weld process is for the weld current to generate sufficient heat between the
workpieces being welded so that the metal will melt, fuse together and form a weld nugget. For this to
happen, the surface contact must be maximized. The following experiment may sound silly, but proves
an important point: take a piece of Scotch tape and stick it to a clean piece of paper. Assuming that the
tape was clean beforehand, it probably sticks very well. Now sprinkle some salt on the piece of paper.
Stick another piece of tape to the paper with the salt on it. Depending on how much salt is there, the
tape probably sticks somewhat to not at all. Lastly, stick a third piece of tape to some carpeting, then
pull it off. Now try to stick that same tape to the paper. The third piece probably doesn't stick at all.
Compare the electrodes to the tape and the workpiece to the paper. The clean tape sticks best to the
clean paper, just like well-maintained, clean electrodes have the best contact with a clean workpiece.
The tape sticks so-so to the paper with the salt on it, just like electrodes will have a so-so contact with
the workpiece if it's dirty, greasy, etc. Lastly, the tape that has been stuck to the carpet and then re-
stuck to the paper probably doesn't stick well at all, just like worn or pitted electrodes don't have very
good contact with the workpiece. By maximizing the surface contact, current density is increased. Both
of these factors play key roles in ensuring that enough heat is generated to reach that ultimate goal of
forming a weld nugget.
Current Density
Current density describes how much current is being delivered to a specific area. In other words, it
describes the concentration of the current in a small area of the workpiece— namely, the area where
the weld is. To calculate current density, the amperage (how much current) is divided by the surface
area (area of contact between the electrode and the workpiece). As a rule, the smaller the surface area,
the denser the current. When the current is denser, the surface area gets hotter and the metal melts
faster. Consequently, a current density that is too high for the application may cause expulsion. In
contrast, a larger surface area delivers a less dense current. If the current density is too low for the
application, there may be cold welds or perhaps no welds at all.
The size, shape and overall condition of the electrodes affect the surface area in contact. Small pieces
missing from the tips of the electrodes (pitting) will result in an increased current density due to the
decreased surface area. The same amount of current fired through a smaller surface area may cause
little hot spots that expel molten metal (expulsion), and/or may result in undersized weld nuggets.
Conversely, if the electrode tips mushroom and get bigger, the current density is lower. For example,
suppose that there are 6-mm round tips on a welder. The area of each tip is about 28 mm2. (The area of
a circle is πr2:32*3.14 ≈28). Suppose the tips deliver 10 KA to a workpiece. Current density equals the
amperage divided by the surface area, so the current density will be 0.36 KA, or 36 Amps for every
millimeter squared of surface (10 KA/28 mm2 = 0.36 KA/mm2). What happens if the tips mushroom to
measure 7-mm (about 0.040 inches greater in diameter)? Although one millimeter doesn't seem like a
significant increase, consider what happens to the current density: The 7-mm tips now have a surface
area of about 38 mm2(3.52*3.14 ≈38). Dividing the amperage by the surface area results in 0.26 KA
or 26 Amps for every millimeter squared of surface. The difference between 36 Amps per mm2and 26
Amps per mm2is a rather significant 28% reduction in current density! (36 Amps – 26 Amps = 10
Amps difference; 10 Amps is 27.78% of 36 Amps).
By allowing the electrodes to mushroom only one millimeter bigger, over a quarter of the current
density has been lost, even though the same amount of current is passing through the tips. Imagine the

0428-INS-400 Rev. E 1-
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size of the loss if they've mushroomed 2, 3, even 4 millimeters! A constant current control or a weld
stepper may be used to regulate the amount of current used, but a controller or stepper does not track
the change in surface area. So, even though the current is regulated, the current density is overlooked.
Unfortunately, inadequate current density usually produces inadequate welds. Following proper
preventive maintenance schedules can help ensure sufficient current density by ensuring that the
electrodes remain in good condition.
As proven in the example above, it is crucial to have the proper current density at the area where the
weld is to be made. Depending on the materials being welded, however, 'proper' current density is
actually a range, rather than one specific amount. Welding engineers call this range the weld lobe. Each
parameter involved in making the weld (current, voltage, resistance, etc.) has its own range, or lobe.
Quality welds are made when the weld process stays within the lobe. The next chapter will discuss
weld lobes and tolerancing, which is a way to ensure that the weld process does not fall outside of the
lobe.
Ohm's Law and Joule's Laws
The following laws are widely thought to be what make or break resistance welding. While it is true
that these laws are very important to resistance welding, there are a few details that should be clarified.
Ohm's Law states that V(Voltage) = I (Current) x R (Resistance).
What does this mean in real-world terms? Returning to the pipe example, the more water pressure
there is in a pipe (more voltage), the more water can flow through that pipe (more current). If the size
of the pipe decreases (more resistance), then the water flow will decrease (less current) but the pressure
drop along the pipe will increase (more voltage).
Joule's Law states that H(Heat) = I (Current) x V (Voltage) x T (Time the current is allowed to flow).
Or, written differently,
H(Heat) = I2(Current squared) x R (Resistance) x T (Time the current is allowed to flow).
Note: V(Voltage) = I(Current) x R(Resistance), so the two equations are the same, just stated
differently. The second version of this law is probably more common in the field.
Joule’s Law is an equation that gives the amount of heat (energy) delivered to something. It would
seem sensible to assume that it's the amount of heat delivered to the weld. However, it is important to
consider all the factors in the equation: Current, Voltage, and Time. Joule's Law assumes that each of
these factors remains constant in the secondary of the welding transformer. A weld controller or weld
timer may indeed provide a constant amount of current at the electrodes, but recall Ohm's Law:
Voltage equals Current times Resistance, or written differently, Current equals Voltage divided by
Resistance. Factors like pitting or mushrooming of the electrodes, dirty workpieces, changes in force,
etc. all have an effect on the surface area (the area of contact) between the electrode and the workpiece.
Since changes in the surface area affect the contact resistance (resistance of the surface area), it is
reasonable to say that the resistance at the workpiece is not constant, but rather a factor that can change
depending on a number of other conditions. If Resistance is not constant, then according to Ohm's

0428-INS-400 Rev. E
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Law, Current is not constant either. This means that the I-squared version Joule's Law will not reveal
the amount of heat generated at the workpiece unless the resistance at the tips is known.
Simply put, to determine how much heat is being generated at the workpiece using Joule’s Law,
current, voltage or resistance must be measured at the workpiece. Although a weld controller may be
programmed to deliver 20 KA at 10 Volts, if there is significant resistance in the secondary weld loop,
the heat will go there and not to the workpiece. Likewise, if the electrodes are worn or the workpiece is
dirty, resistance and current density will be affected. In such a situation, a controller might indicate 10
Volts at the secondary, however there might actually be only 5 Volts at the weld tips. Such a disparity
could easily cause bad welds.
Identifying and Correcting Weld Problems
A simple rule to remember is that quality usually equals consistency: welds that are always made
within the specified weld lobe will consistently be of high quality. The question is, how can you
determine if welds are being made consistently within the lobe? If a weld control is programmed to
deliver a certain amount of current at a certain amount of force, how can you ensure that the right
amount of current and force was delivered at the tips? The amount of current coming out of the
transformer may be correct, but is the current density at the workpiece where it should be? How do you
know if the weld is good? The most common method of answering these questions is through
destructive testing. It's hard to dispute the quality of a weld after it has been pulled apart and inspected.
However, destructive testing produces a lot of scrap metal, and while it will reveal whether the weld is
good or bad, it cannot explain the specific details of why or how a weld turned out the way it did.
Resistance weld monitoring provides a way to see what is happening while each weld is being made.
Critical parameters, such as resistance and current density, can be observed and measured at the
workpiece during the weld process. The next chapter will discuss how this process works.
The following is an abbreviated guide of commonly encountered welding problems and their possible
causes, adapted from documents published by the Resistance Welder Manufacturers' Association and
reprinted with permission.

0428-INS-400 Rev. E 1-
9
Recommendations for Producing Quality Welds
To produce high quality welds consistently, follow these tips:
1. Be sure that the electrodes you are using are suitable for the job.
2. Use standard electrodes whenever possible.
3. Select an electrode tip diameter suited to the thickness of the stock being welded.
4. Make use of flow indicators for viewing and assuring proper cooling water flow through the
electrodes (typically, 1.5 gallons per minute).
5. Ensure that the internal water cooling tube of the holder projects into the tip water hole to within ¼
inch of the bottom of the tip hole.
6. Adjust the internal water-cooling tube of the holder to the appropriate height when switching to a
different length tip.
Excess Indentation
Electrode
Mushrooming Undersized Weld
Nugget
Offset Weld Nugget
Misshapen Weld
Nugget
Explusion at Surface
Expulsionat Interface
Cracked orPoor Weld
Nugget Discolored Weld
Nugget
No Weld
Weld Force Too High X
X
X
X
Weld Current Too High X
X
X
X
X
Weld Time Too Long X
X
X
X
X
Weld Force Too Low *
X
X
XX
Weld Current Too Low
X
X
Weld Time Too Short
X
X
Electrode Face Too Small X
X
X
X
X
Electrode Face Too Large
X
X
Insufficient Electrode Cooling
X
Electrode Allow Too Soft
X
Electrodes Not Flat & Parallel
X
X
X
Electrodes Misaligned
X
X
Poor Fit Up X
X
X
X
X
X
X
Poor Heat Balance
X
X
Weld Spacing Too Close
X
X
Weld Too Close To Edge of Part
X
X
X
Dirty Material
X
X
XX
X
Metallurgy of Material X
X
Squeeze Time Too Short
X
X
Poor Follow-Up
X
X
XX
No Speed Regulator On Cylinder X
Poor Pressure Regulation X
Hold Time Too Short X
Transformer Tap Set To Off
X
No Weld Switch(es) In No Weld
X
Pressure Switch Open
X
Temperature Limit Switch Open
X
Electrodes Do Not Contact Work
X
Insulated Electrodes/Holders
X
Shunt Path In Secondary
X
X
Excess Ferrous Material In Throat
X
X
Emergency Stop Switch Open
X
* If Weld Force is too low, excess heating of the material surface may cause excess indentation.
Figure 1-3 Chart of weld defects and possible causes

0428-INS-400 Rev. E
1-10
7. Ensure that the top of the adjustable water-cooling tube in the holders is the proper height when
changing to a different tip length.
8. Coat the tip with a thin film of cup grease before placing it in the holder to simplify removal.
9. Use ejector type holders for easy tip removal that won't damage the tip walls.
10. Clean the tip taper and holder taper on a regular basis, removing any foreign materials.
11. Perform dressing of electrodes on a regular basis to maintain the correct contour.
12. Use a rubber mallet to align holder and tips, rather than a metallic tool.
Avoid these potential sources of weld problems:
1. Never weld using unidentified electrodes or electrode materials.
2. Avoid using special-purpose or offset tips if the job can be handled with a standard straight tip.
3. Do not use a small tip for welding heavy gauge materials or a large tip on small piece.
4. Do not overlook turning on the cooling water to the appropriate force when beginning to weld.
5. Never use a water hose that does not firmly fit the water connection nipples.
6. Avoid leaky, clogged or broken water connections.
7. Do not use holders that have leaking or deformed tapers.
8. Do not use electrode holders without an adjustable internal water cooling tube.
9. Avoid leaving the electrodes unused in tapered holder seats for long periods.
10. Do not use pipe wrenches or similar tools when removing electrodes.
11. Never dress an electrode using a coarse file.
These recommendations can help improve the quality and consistency of your welds. For more
information, you can contact the RWMA (Resistance Welding Manufacturing Alliance) or AWS
(American Welding Society) directly:
550 NW LeJeune Road
Miami, FL 33126
Tel: [phone]
Intl.: [phone]
URL: www.aws.org

0429-INS-400 Rev. C 2-1
Introduction to Resistance Weld Monitoring
Introduction
As discussed in the last chapter, what you see is not always what you get. Although a constant current
control may indicate that there is sufficient weld current to create a quality weld, unless the
measurement is taken at the electrodes, the actual amount of heat generated is only speculation. In
view of the fact that the generation of sufficient weld heat is a function of current density, it could
logically be argued that the primary cause of bad welds is inadequate current density. Many factors
affect current density: poorly maintained, worn or improperly sized electrodes, dirty materials, lack of
sufficient force at the tips and lack of sufficient weld current at the tips are just a few examples. This
being the case, how can a production person or weld engineer catch these (or other) potential problems
before they lead to bad welds? How do you make sure that what you see is what you get? The answer
lies in the subject of this chapter: resistance weld monitoring.
Why Monitor?
When Professor Elihu Thompson developed the concept of resistance welding, the idea of weld
monitoring most likely didn't exist. At that time, the only means available of differentiating a good
weld from a bad weld was through destructive testing. Even today, destructive testing is regularly used
to provide a reliable answer— 'good weld' or 'bad weld'— depending on how the weld reacts during its
destruction. For all its reliability, however, destructive testing doesn't tell the whole story. While it can
easily be determined whether a weld is good or bad, uncovering the precise factors that made it that
way is not as straightforward. Was there an excess or deficiency of one or many factors during the
weld? At what point or points in the welding process did the excess or deficiency occur? Resistance
weld monitoring can provide immediate answers to these questions.
With the advent of advanced computer technology, today's methods of observing and testing individual
weld integrity have advanced significantly, keeping in step with ever-evolving safety and quality
standards. By monitoring the welding process, compliance with international quality standards– such
as ISO and/or QS 9000+, or MVSS– is simplified. Weld quality can be instantly verified with
electronic documentation of individual weld characteristics; hard copy of weld data can even be
printed for comprehensive record keeping or for inspection. It's hard to dispute the integrity of a
product when the most critical stages in the manufacturing process have been systematically observed,
recorded and analyzed.
It's important to realize that weld monitoring is not a substitute for destructive testing. Rather,
monitoring and destructive testing go hand in hand. While destructive testing can unconditionally
guarantee whether an individual weld is good or bad, monitoring can show why that particular weld
was good or bad. Together, they can answer what is perhaps the most important question of all: is the
welding process consistently within the defined weld lobe?

2 0429-INS-400 Rev. C
2-2
Weld Lobes and the Weld Process
Each of the factors involved in the creation of a weld (Current, Voltage, Resistance, etc.) has a specific
range in which good welds can be made. This range is commonly known as the weld lobe. Bad welds
are made when the weld process falls outside of the lobe, so the simple answer to making consistently
good welds is to keep the process inside the lobe. It is not so simple, however, to ensure that this
happens for each weld made. This is where resistance weld monitoring is most valuable. The following
example uses a weld nut and the relative movement of the electrodes during the weld to examine what
goes on during the weld process. Livingston terminology (in italics) is used to describe various
measurements.
The nut itself has a number of little metal feet or projections on the bottom of it. These projections sit
on top of the workpiece to which they'll be welded. A measurement of the nut sitting on top of the
workpiece with the electrodes clamped on it before the weld is made is called the Initial Thickness.
When the proper electrode force is applied and weld current is fired, the projections melt into the
workpiece and create a weld. When the projections melt, the molten metal expands for a moment,
pushing the electrodes apart (this movement is called Expansion) before sinking down into the
workpiece (this movement is called Setdown). The expansion-setdown process is very much like a pot
of water boiling over before it's removed from the heat: as the metal is heated, it expands and then
quickly contracts as it cools to form the weld. A subsequent measurement of the nut/workpiece after
the weld is made is called the Final Thickness. All these different measurements of electrode
movement are measures of what's commonly called Electrode Displacement, or simply Displacement.
Measuring displacement provides a good indication of whether or not the resulting weld was formed
properly. If the nut sinks too far into the workpiece, it may be a sign of excessive heat which could
render the weld no good. It could also indicate that too much force was applied, the weld time was too
long, or a number of other things. Conversely, if the nut doesn't sink far enough, it may mean that not
enough heat was generated for the materials to weld properly, the force was insufficient, etc. Problems
with displacement can be problematic in many applications, such as welding hydraulic fittings. If the
setdown is too much/too little, chances are that the welded fitting will leak. When taken into account
that displacement is only one of many factors that, when measured, provide valuable information about
the formation of the weld and its overall quality, it becomes clear that weld monitoring is indeed a
valuable tool. Weld monitoring provides the user with an easy way to access a wealth of information
about the welding process— information that can actually help improve the process itself, as well as
alert the user to any number of potential problems.
Styles of Monitoring
There are many different types of monitoring systems on the market nowadays. These systems can be
broadly categorized into three different styles, which for educational purposes are nicknamed as
follows: Before & After monitoring, Mass monitoring, and Dynamic monitoring.
Before & After Monitoring
As the name suggests, Before & After monitoring (hereafter referred to as BA monitoring) focuses on
only two phases of the weld process: before the weld is made, and after the weld is made. This type of
monitoring is typically used to measure displacement only. As mentioned above, measuring