Equipment for welding

Equipment for welding

Introduction to Welding Circuit

Current and Circuit Polarity

Cables, Electrodes

Arc welding power sources, DC and AC Power sources,

Welding Positioners, Manipulators, Robotic Arms

Automation in Welding

Introduction to Welding Circuit

Introduction and Classification of Power Sources for Welding

Also known as Power Supplies and Welding machines

Important Concepts

1. Duty Cycle

Percentage of any given 10-minute period that machine can operate at rated current without overheating or breaking down

Rating of 100% means machine can be used at rated amperage on continuous basis

Required by continuous, automatic machine welding

Rating of 60% means machine can be used at its capacity 6 out of every 10 minutes without damage

Satisfactory for heavy SMAW and GTAW

Also known as Power Supplies and Welding machines

Introduction and Classification of Power Sources for Welding

Also known as Power Supplies and Welding machines

Many different methods of classification

Two Important Classifications

i Constant Current CC- Also Referred to as Variable Voltage

ii Constant Voltage CV- Also Referred to as Variable Current

Selection of Power Source Relative to Welding Process

Because no single power source is right for all welding situations, it is necessary to know the processes to be used before selecting the best power source

Classification - Out Put Slope

2 Output slope

i Constant Current Current remains fairly constant regardless of changes in arc length Called drooping voltage, variable voltage, or droppers Load voltage decreases as welding current increase

ii Constant Voltage Voltage remains fairly constant regardless of changes in current

Introduction and Classification of Power Sources for Welding

Classification - Out Put Slope

Classification - Out Put Slope

Introduction and Classification of Power Sources for Welding

Classification – Power Source Type

1 Generated (Rotating)

i Motor Driven Current remains fairly constant regardless of changes in arc length Called drooping voltage, variable voltage, or droppers Load voltage decreases as welding current increase

ii Engine Driven Powered by gas or diesel combustion engineCan be found with a.c or d.c electric motor

No longer being manufactured and rarely found

Classification – Power Source Type

1 Generated (Rotating)

i Motor Driven

Introduction and Classification of Power Sources for Welding

Classification – Power Source Type

Motor Driven Generators Desirable Characteristics

Have forceful penetrating arcVersatile - Can be used to weld all metals that are weldable by arc processFlexible - With proper electrode, can be used in all positions

Durable and have long machine life

Requires considerable maintenance due to moving parts

Classification - Power source type

ii Static (Converted Power)

a TransformerUse basic electrical transformer to step down a.c line power voltage to a.c welding voltage

b Transformer-rectifierUse basic electrical transformer to step down a.c line power voltage to a.c welding voltageWelding voltage then passed through rectifier to convert a.c output to d.c welding currentMay be either d.c or a.c.-d.c machines

c InvertersIncreases frequency of incoming primary powerConstant current, constant voltage, or bothProduce a.c or d.c welding current

Introduction and Classification of Power Sources for Welding

Classification - Power source type

ii Static (Converted Power)

Reduces tendency to arc blow

Can use larger electrodes resulting in faster speeds on heavy materials

Lower cost

Decreased power consumption

High overall electrical efficiency

Noiseless operation

Reduced maintenance

Classification - Power source type

ii Static (Converted Power)

b Transformer- RectifierHave many designs and purposes Flexibility is one reason for wide acceptanceDeliver either DCEN or DCEP

May be used for:

Stick electrode weldingGas tungsten arc weldingSubmerged arc weldingMulti-operator systemsStud welding

Miller Electric Mfg Co.

Introduction and Classification of Power Sources for Welding

Classification - Power source type

ii Static (Converted Power)

b AC / DC Transformer- Rectifier

Permit welder to select either a.c or d.c and electrode negative or electrode positive Switch

Permits welder to use only transformer part of machine for a.c welding

Flipping switch then output current directed through rectifier which converts it to d.c welding

High frequency arc-starting devices, water/gas flow

controls, balance controls for a.c operation,

remote control often built into machine

Classification - Power source type

ii Static (Converted Power)

b DC and AC/DC Inverters

Portable, lightweight, and versatileMay be either constant current, constant voltage or both Can perform several different processes

Miller electric Mfg Co.

Miscellaneous - ELECTRODE AND WORK CABLE

Required to complete electric circuit between welding machine and workElectrode cable (welding cable) attached to electrode holder

Work cable attached to work

Rubber-covered multistrand

copper cable generally used

Must have high flexibility

CABLE CORE CONSTRUCTION

Woven of thousands of very fine copper wire

Greater the number of strands the more flexible

Components

A. Wires stranded for extra flexibility

B. Paper wrapping around wires

allows conductor to slip within robber covering when bent

C. Extra strength from open-braided

reinforcement of extra cotton cords

D. Special composition and curing of

heavy rubber covering

WORK CABLE

Not necessary to have flexibility of electrode cable

Usually same cable used

Important considerations

Amperage of welding machine

Distance from work

Larger cable

Greater the amperage and greater the distance

Resistance increases as diameter of cable decreases

Miscellaneous – CABLE LUGS

Required on both electrode cable and work cable

Soldered or fastened mechanically

Connections MUST be tight and secure

Miscellaneous – WORK CLAMPS

Variety of structures to be welded; many types of clamps may be used

Copper hook, heavy metal weight, C-clamp

Specialized work clamps

Miscellaneous – QUICK CONNECTORS

Attached to ends of different lengths of cables

Allow quick and easy attachment to any length cable

Device used for holding electrode mechanically

Conveys electric current from welding cable to electrode

Insulated handle protects hand from heat

Jaws of holder grip electrode at any angle

Made of metal with high electrical conductivity and ability to withstand high temperatures

Jaws can be replaced with new ones

Should be light in weight, well-balanced and have comfortable grip

Size of holder must be in line with size of welding machine

Fully insulated so stays cool even with high duty cycles

Miscellaneous – SPRING TYPE ELECTRODE HOLDERS

Miscellaneous – Welding Positioner

Miscellaneous – Welding Manipulator