Module 3 Energy & Time

8/13/2019 Module 3 Energy & Time

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Module 3

Energy & Time

Golden Eagle

Resistance Welding Training


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2

Major Resistance Welding

VariablesMaterials

EnergyGoodWeld

WeldForce

Time


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Resistance WeldingTechnologies:

High Frequency Inverter (HF)

Linear DC

Capacitor Discharge (CD)

Direct Energy (A.C.)


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High Frequency Inverter

Power Supply

WeldingTransformer

Weld Head Feedback

1 - 25 kHz


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High Frequency Attributes

Single Pulse

Upslope/Downslope

Dual Pulse

Characteristics:Energy control in Current,Voltage, or PowerTime control in 0.1 millisecondincrements (minimum)

High Repetition RatesClosed Loop Feedback -Compensates for varying partconditionsBuilt-in Monitor

Applications and Use:Best control for automation.Extends electrode life. Can weld awide range of applications.


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Linear DC

Power Supply Weld Head

Feedback

C a p a c

i t o r

C h a r g

i n g

C i r c u

i t

CapBank

VoltageLeads DriveUnit

CurrentShunt MOSFET

Bank


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Linear DC Attributes

Single Pulse

Upslope/Downslope

Dual Pulse

Characteristics:Energy control in Current,Voltage, or Power

Time control in 0.01 millisecondincrements (minimum)Low Repetition Rates

Closed Loop Feedback -Compensates for varying partconditions

Built-in Monitor

Applications and Use:Ultra stable waveform. Extendselectrode life. Best choice forwelding fine wires and thin foils.


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Capacitor Discharge

Power Supply

PulseTransformer

Weld Head

C a p a c

i t o r

C h a r g

i n g

C i r c u

i t

CapBank

SCR Circuit


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Capacitor Discharge Attributes

Single Pulse

Pulse Width Adjustment

Dual Pulse

Characteristics:Energy control in % Energy orWatt-SecondsTime control in Pulse Widths

Low Repetition Rates

Open Loop - No FeedbackLacks true upslope control

Applications and Use:Fast rise time with high peakcurrent. Good for welding flatconductive parts. Require goodpart fit up.


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Direct Energy

Power Supply

WeldingTransformer Weld Head

Timer

Triac

Taps


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Direct Energy Attributes

Transformer Taps

Cycle Welding

% Current Control

Characteristics:Coarse energy control withtransformer taps

Fine energy control in %CurrentTime control in Line Cycles

High Repetition RatesOpen Loop - No Feedback

Susceptible to Line VoltageFluctuationsWeld cools between cycles

Applications and Use:General purpose, lower costwelders with high energy output.Longer weld times useful forbrazing applications.

I %


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Capability vs. Optimal Range

AC

CD

HF

DC

Size of Smaller Part (Thickness)

.001 .010 .020 .030 .040 .050

.025 mm 0.25 mm 0.51 mm 0.76 mm 1.02 mm 1.27 mm

FLAT PART SIZES

Optimal

Optimal

Optimal

Optimal

Optimal

Optimal

Optimal

Size of Smaller Part (Diameter)

.0002 .018 .036 .054 .072 .090 .005 mm 0.46 mm 0.91 mm 1.37 mm 1.83 mm 2.29 mm

ROUND PART SIZES

Optimal

Resistive: Molybdenum, Tungsten, Zinc, Nickel, Platinum, Tin, Tantalum,Steel, Titanium, MP35N, Nichrome

Conductive: Silver, Copper, Gold,Aluminum, Brass

TYPICAL MATERIALS:


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Specification ComparisonClosed Loop:

DC HF Open Loop:

CD AC 115V; 230VSingle Phase

240V; 400V; 480VThree Phase

115V; 230VSingle Phase

115V; 230V; 460VSingle Phase

5-4000 Amps 50-4000 Amps Up to 875 WS Up to 16 KVA

I, V, & P I, V, & P N/A (Open Loop) N/A (Open Loop)

Input Power

Output Range

Feedback Modes

Feedback Rate

Time Control in: .01 msec steps 0.1 msec steps Pulse Widths Line Cycles

>10 micro-sec 40-250 micro-sec N/A (Open Loop) N/A (Open Loop)

Weld Monitoring Built-in I, V, & P Built-in & Sentry Sentry Option Sentry Option

Repetition

Rate

Equipment

Cost

Application andUse Notes

Fine energycontrol, smoothwaveform. Best

choice for weldingfine wires & foils.

Best automationsupply. Extends

electrode life.Welds wide range

of applications.

Fast rise time withhigh peak current.Good for weldingconductive parts.

General purposecontrol with high

energy output.Longer weld timesuseful for brazing.


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Why Choose Closed Loop?

Repeatable Welds Controlled Heating Rate Feedback Modes Built In Monitoring

Process Tools Longer Electrode Life


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A Real World Example

Weld 1:

Weld 2:

Two sequential welds were made on production parts.The same current was delivered, but the voltageadapted to the difference in work piece resistance.


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Controlled Heating Rate(Upslope)

At the beginning ofthe weld, contactresistance is high.

Using open loop power supplieswithout controlledupslope can result in:

ExpulsionElectrode StickingExcessive Marking

R C1 R C2

R C3

Weak Welds


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Controlled Heating Rate(Upslope)

If too muchenergy is applied

before theelectrodes have achance to seat

properly, energy

will be wasted atthe electrode to part contact area.

HeatAffected

Zone


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Feedback ModesConstant Voltage: Compensates for parts misplacement and force problems

Reduces weld splash Ideal for round (non-flat) parts M onitor curr ent

Constant Power: Varies current and voltage for consistent energy Breaks up surface oxides and plating Ideal for automation to extend electrode life M onitor cur rent or voltage

Constant Current: Delivers same current regardless of resistance changes Compensates for part thickness changes Ideal for flat parts with consistent electrode to part fit-up M onitor voltage


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Part and Process Challenges:

Parts:Surface RoughnessPlating

InconsistenciesOxidized PartsContamination

ProjectionsWire WeldsThicknessInconsistencies

Process: Part Misplacement Varying Overlap

Inconsistent Force MushroomedElectrodes

Oxidized Electrodes Automated Systems Weld Cables


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Part Challenges:

Surface RoughnessPlating

InconsistenciesOxidized PartsContaminationProjectionsWire WeldsThicknessInconsistencies

Constant Power

Constant Voltage

Constant Current


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Process Challenges:

Part Misplacement Varying Overlap Inconsistent Force MushroomedElectrodes Oxidized Electrodes

Automated Systems Weld Cables

Constant Voltage

Constant Power

Current, Voltage,or Power


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Feedback ModesFeedback Mode Part Challenges Process Challenges

Constant Voltage ProjectionsWire Welds

Part MisplacementVarying OverlapInconsistent ForceMushroomedElectrodes

Constant Power SurfaceRoughnessPlatingInconsistenciesOxidized PartsContamination

Oxidized ElectrodesAutomated Systems

Constant Current Flat Parts,ThicknessInconsistencies

Weld Cables


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Weld Monitoring

Graphic waveform traces (HF25, DC25, UB25) provide: Simple, dynamic weld information for process

understanding and diagnostics Easy set limits with programmable relay action Other process tools

Pre-Weld Check A.P.C. Resistance Set Weld to Limit Energy Limit


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Process Tools

Weld to a Limit

Energy Limit

Active Part Conditioner

/ Resistance Set

Pre Weld Check


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Process Tools

Note: Welding conductive parts with resistive electrodes may be difficult to monitor electrically.

In these applications, the bulkresistance of the electrodes ismuch greater than the resistanceof the parts.

Displacement monitoring is preferred.


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Statistical Process Control

Some monitors offer RS-232or RS-485 transmission ofweld data to a P.C.

Identify Process Trends

Record Keeping

Quality Reporting

S.P.C. software packagescan generate controlcharts and provide datasummaries

Documents

Module 3 Energy & Time