spot welding 101

8/13/2019 Spot Welding 101

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CMW Inc. 2006CMW Inc. 2006

Presents:Presents:

Resistance Spot WeldingResistance Spot Welding


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Spot Welding is theprocess of joining two

pieces of metal together bypassing current through arelatively small area (spot)while applying pressure for

a given amount of time. Spot Welding is used for

resistance welding. Otherwelding methods are (Arc,Torch, MIG, & TIG).

Copyright CMW Inc. 2005

Resistance SpotResistance SpotWeldingWelding


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A Spot welding system typicallyconsists of a: cap or electrode that contacts

the metal

Holder that retains the cap orelectrode Gun arm that retains the

Holder Welding machine that thru a

hydraulic cylinder, delivers

pressure to the metal Controller that defines theweld cycle

Transformer that steps theline power up to the weldingpower level

Cooling chamber that keepsthe water at a constanttemperature that circulatesthru the entire system toremove excess heat




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There are threestandard types ofSpot Weldingsystems Base Type #1 Robotic or Cell

Type #2 Portable Type #3

Each has itsadvantage based onvolume, accessibility,operationalrepeatability

Type # 2

Type # 1

Type # 3Copyright CMW Inc. 2005



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Based primarily on volume, the user will either use Caps orElectrodes. Both Caps and Electrodes can be reconditioned orredressed to near their original shape for extended life. Electrodescan be redressed more times than Caps but ultimately more copperis thrown away. Caps, when used with a Shank, can be bothreconditioned and ultimately disposed of with less waste of copper




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Cap or Electrode noses areavailable in a variety ofshapes and are specifiedbased on the type of metalthat is to be welded, thespot desired and customerpreference.


POINTED

DOME

FLAT

OFFSET

TRUNCATED

RADIUS



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The anatomy of aCap/Electrode is asshown on the right.The Face comes indirect contact with themetal and largelydetermines the size ofthe spot. The Taper ispreciselymanufactured to allowa water tight sealbetween mating parts.

The Shaft is varied inlength andconfiguration to alignthe Face to the metal

TAPER

FACE

SHAFT NOSE




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Electrodes andShanks can be

supplied with or without water tubes. Thepurpose of the watertube is to better focusthe cooling waterflowing on the systemat the point where theheat is beinggenerated at theweld face.




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Caps and Electrodes are available in industry standard (RWMA) tapers to provide awater tight seal between the cap, shank and holder or between the Electrode andHolder.

Typical tapers are 4, 5, 6, & 7. The taper used is based on the current and pressure required for a given weld. The

higher the current/pressure, the larger (the taper number) taper will be used.

Caps, Electrodes and Shanks are available in either Male or Female configurations




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Electrodes andShanks areavailable in anumber ofconfigurations to

allow the Face ofthe Cap/Electrodeto come in direct flatcontact with the

metal.




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Electrodes are also available in a number of special configurationsfor specific applications




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Electrodes are also available in a number of special configurationsfor specific applications



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Single Bend or DoubleBend Electrodes can be

specified by OverallLength (C), Offset (D),and Nose Length (N), toallow easy access forspot welding in a tightarea.

Various holderconfigurations can alsoadd even more flexibilityto allow you a spot weldin a tight position.




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Caps/Electrodescan be specifiedin three basic

materials basedon the material tobe welded. (seethe weld chart)




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Holders are available in a number of configurations thatinclude (in addition to Taper options):

Straight (of various lengths and diameters) Offset (of various offsets)


200 Series (Ejector) WaterCooled Electrode Holder

100 Series (Non-Ejector)Water Cooled Electrode

Holder

300 Series Premium (Ejector)Water Cooled Electrode Holder



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Holders can

have amechanicalassist (knockout button) toremove thewornCap/Electrodefrom theHolder




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What to look for to find Spot WeldingCustomers: Uses Sheet metal in their product

Appliances Automotive and Transportation Filing Cabinets Computer and other Electronic Chassis

Manufactures shelving made of wire rods weldedtogether (typically at 90 ) as in Appliance shelving

Manufactures a container (Tank, Barrel, or Vessel) that haswelded seams (Seam Welding)




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Shown on the right areproducts which are used toSharpen or Redress Capsor Electrode

This purpose is to Use Redressing tools as

shown


Pneumatic Power Handle Electrode Dresser

Electrode Dresser With abrasive cloth

Electrode Dresser



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While there are a number of variables that must becontrolled to obtain a good weld, the most important are(after the selection of the correct components and Welding system)

The current settings on the transformer The timing of the weld (clamping, welding, and holding) Water flow These variable can be selected by using the Weld Tables as

supplied by the Manufacture of the Welding Components orSystem or referring to the RWMA website ( www.RWMA.org )




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A good Spot is stronger and more energy efficient.




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Go to Troubleshooting Guide


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23Copyright CMW Inc. 2005



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Visit us at www.cmwinc.com for more spot welding information and product line types.




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spot welding 101

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