ac resistance welding machine manual 50kva

7/21/2019 AC Resistance Welding Machine Manual 50Kva

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INSTRUCTIONAL MANUAL

AC Resistance Welding Machine

KIRTI PRESSINGS PVT. LTD.


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Dear Customer,

KIRTI PRESSINGS PVT LTD thanks you for selecting our machine for yourproduction requirements.

Our resistance welding machines are designed for very high demand of rigidity andrepeat accuracy. Every part of the machine is now tested and proven successful inhigh production volumes. In standard models we have adopted simple controls, rigidmoving parts, minimum throat depth. Providing value for money for years.

Customer feedback is always proving a great opportunity to improve our machines.Your input regarding improvement or design modifications will allow us to build moreapplication friendly machines. I request you to help us making better designs.

With this manual we are furnishing installation requirements, operation instructions,basic fault finding, controller setting examples and information on resistance welding.

We are committed to make latest technologies available to our customers. Pleasekeep visiting our website for more information and new technology in resistancewelding. www.kirtipressings.com

Thank you once again,Yours Truly

Ujjwal Bahekar.Managing DirectorKirti Pressings Pvt Ltd


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Table of Contents

I. Preface and General Safety....................................................................4i. Introduction............................................................................................4ii. Safety Information.................................................................................5

iii. Warranty Information............................................................................6

II. Specifications..........................................................................................7III. General Dimensions................................................................................8IV. Unloading The Machine..........................................................................9V. Making Installations and Initial Settings...............................................9VI. Power Connection Requirement...........................................................11VII. Water Connection Requirement............................................................11VIII. Powering ON and Test Run...................................................................12IX. Internal Components of The Machine..................................................17

i. Transformer..........................................................................................17ii. Thyristor................................................................................................17

iii. Controller..............................................................................................18X. Example on Setting Current Monitor....................................................18XI. Setting Up and Making Resistance Welds...........................................20

i. Welding Electrode................................................................................20ii. Electrode Installation...........................................................................20

iii. Setting Weld Force..............................................................................20iv. Electrode Selection.............................................................................21v. Electrode Material................................................................................21vi. Electrode Design.................................................................................21

vii. Electrode Alignment...........................................................................22viii. Electrode Maintenance.......................................................................22ix. Pressure Settings...............................................................................22x. Heat Settings.......................................................................................23

xi. Time Setting........................................................................................23xii. Testing The Weld................................................................................24

XII. Fault Finding.........................................................................................25XIII. Spare Parts List.....................................................................................31XIV. Circuit Diagram.....................................................................................32XV. Standard Starting Parameters For Welding.......................................33

XVI. Contact Details.....................................................................................35


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I. Preface and General Safetyi. Introduction:

Thank you for purchasing this KIRTI Product for your production requirement.Our resistance welding machines are designed for very high demand of rigidity andrepeat accuracy. Every part of the machine is now tested and proven successful inhigh production volumes. In standard models we have adopted simple controls, rigidmoving parts, and minimum throat depth. Providing value for money for years.

WARNING

1. Read this instruction manual before using this machine. Be sure tofully understand the descriptions contained in this instructional manualbefore starting operation, inspection or maintenance of this machine.In particular, the machine must be installed, operated, adjusted andmaintained by trained specialists or qualified personnel as directed inthis instruction manual. If the machine is operated by anyone otherthan a trained specialist or other qualified personnel, it can result indamage to the machine or personal injury. In such case, themanufacturer of the machine shall be released from al theresponsibility and liability.

2. Any accidents or failures caused by users failing to follow theinstructions contained in this manual shall release the manufacturer ofthis machine from all responsibility and liability

3. Keep the instructional manual in a specified place near the machineas a quick reference tool. Please keep this manual in good condition.

4. When this machine is transferred to another owner, this instructionmanual must be transferred together with the machine.


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ii. SAFETY INFORMATION:This equipment must be used solely for welding operations.Welding can be harmful to yourself and others.The user must therefore be educated against the hazards deriving from weldingoperations.

Electric shock may be fatal.Install and earth the welding machine according to the applicable regulations.

Do not touch live electrical parts or electrodes with bare skin, gloves or wet clothing.Isolate yourselves from both the earth and the workpiece.

Fumes and gases may be hazardous to your health.Keep your head away from fumes.Work in the presence of adequate ventilation, anduse ventilators around the arc to preventgases from forming in the work area.

Sparks may injure the eyes ,burn the skin and may cause fire.Protect your eyes with welding masks fitted with filtered lenses, and protect your body withappropriate safety garments.you should also make sure there are no flammable materials in the area, and wear appropriateprotective gaements.Protect others by installing adequate shields or curtains.

NoiseThis machine does not directly produce noise exceeding 80dB,but the welding procedure mayproduce noise levels beyond said limit.

Users must therefore implement all precautions required by law.

ExplosionsDo not weld in the vicinity of containers under pressure, or in the presence of explosive dust,gases or fumes.

Eleltromagnetic CompatibilityThis must be used solely for professional purposes in anindustrial environment. There may be potential difficulties in ensuring electromagneticcompatibility in nonindustrial environments.

In case of malfunctions,request assistance from qualified personnel.

Do not dispose of electrical equipment together with normal waste.

This machine is protected by a thermostat, which prevents the machine fromoperating if the allowable temperatures are exceeded. In this condition the displaywill show the error


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iii. Warranty Information


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II. Specifications:Rated Power at 50% Duty Cycle 50kVASecondary Voltage 6v,8v,9v

Welding Current Maximum 13.5kA

Control Type Secondary Feedback typeDSP Based

Time Setting Least Count 1 Cycle

Throat Depth 300mm

Arm Gap Maximum 300mmElectrode Force 150~470kg

Maximum Strokes PerSecond(No weld)

6

Free Air Consumption for 100Spots 25mm stroke 1bar

250 liters

Cooling Water PressureRequired

2kg/cm

Cooling Water Flow Rate PerMinute

9liters/minute

Power Supply 415v 50Hz 2PhaseMain Supply Fuse Rating 150A

Delayed Fuse 150A

Supply Cable Required 50mm Aluminium/70mmCopper

Dimensions 900mm x 430mm x 1742mm

Weight 515kg


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III. General Dimensions

15301

742

900

953

258

430

1742

Front ViewSide View

212 1030


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IV. Unloading of the machine

For unloading eyebolts are provided at top of the machine.Use proper hook to unload the machine. For more safety use wire rope . Assume 800kg-unloading weight while choosing unloading equipment.

Caution. The weight of the machine is concentrated at upper portion. This may cause machineto topple if handled manually and carelessly. Use crane for unloading and placing the machine atplace. Due care should be taken for possibility of toppling.

V. Making installations and initial settings

Remove packing covers

Install machine at place.

Check for transit damages

Machine on long distance transport comes with protection to controller. REMOVE THISCOVER BY UNBOLTING FOUR SCREWS. This cover is not part of the machine. Pleaseremove this after installation.

Tower lamp is packed in this cage. UNPACK THE TOWER LAMP and screw it at thelocation at top of the machine. Two wires coming from tower lamp are marked (ERROR).Generally the packing is done by retaining the connection.

Locate the mark press

and turn

To fix


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Air preparation unit is packed in box and located inside the machine body. Unpack theFRL unit, Unscrew the bolts at left side of the machine Fix the FRL. Tubing is to be fittedat out of the FRL. Do this by placing the tube by little pressing against the connector. The

air pressure switch if supplied with machine is to be connected by two wires. Theseconnections are to be made on N.C. terminals of the switch. (N.O. terminal screw isremoved on dispatch)

Connect Factory air supply (minimum pressure 5~6 bar) to FRL unit

Fill the lubricator by 32 grade lubrication oil

Machine foundation is not generally required, If needed, expansion bolt fixing can be doneat the holes provided.

Connect tube

Fix the FRL unit

Connect wires to NC

contact of pressure

switch

Fix pressure guage


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VI. Power connection Requirement! Two phase connection with 35mm square copper single core multistrand cable is required

for better performance. Lower cable thickness will effect less current drawn at secondaryand heating of cables voltage drop in primary.

Minimum100 amp MCCB is required for isolating the machine.

VII. Water connection RequirementCooing water is most important input to the machine. Please do not take welds from the machineif water connection is not provided. Air tower cooling is recommended for the machine coolingwater.Like all cooling systems HARD WATER IS NOT GOOD FOR LIFE OF THE MACHINE. If you areusing hard water please treat it with softeners. Using hard water as machine coolant willdrastically reduce life of Transformer and Thyristor. These are high value spares.The cooling arrangement should be capable to take away heat from the water. Cooling tower isbest in performance. Underground tank of 4000 Liters can serve alternate to one machine.Water at output should be less than 5 degree above room temperature. This can be adjusted by

allowing more water flow through the machine.

CONNECT ONLY TWO PHASES OF 415V A.C. MAINS LINE AS INDICATED OPENINGBACK PANEL OF THE MACHINE.

Connect only two phases. (Phase 1 and phase 2) Connect water inlet and water outlet as indicated. Connections are to be made at nipples

provided right bottom at back of machine.

Insure proper flow of cooling water so that out water should not exceed 10 deg aboveambient. it is advisable to out water in free tunnel or dia 2 inch pipe gravity return.

Never operate machine without cooling water this may damage costly thyristor assemblies.

Connect equipment to proper earth.

Connect air line to the point provided at FRL unit

Connect supply

two phase 440v

by 30mm sq

copper cable


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VIII. Powering ON and Test Run

Before making supply 'on' please check and confirm following again.

1. Ensure the 440v supply is connected to the machine.

2. Check water input and output connection are made. Inspect visually for leakage . Stopleakages if any.

3. Inspect air connection for leakage. adjust pressure setting to 3~4 kg/cm^ as per jobrequirements

4. Insure electrode gap and fitment of electrodes

After insuring proper connections make supply on. Check power supply voltageby multimeter this should not be below 400v.

Check controller power supply by multimeter this should be 220v. There are taps

provided on 440 to 220v isolation transformer to adjust this voltageMake controller ON by accessing On/Off switch located at back of the controller.

CAUTION:PLEASE REPLACE PROTECTIVE COVER AFTER CONNECTIONS ORMAITANANCE OF THE CONTROLLER. THERE IS ELECTRIC SHOCKHAZARD AS HIGH VOLTAGE TERMINALS MAY BE ACCIDENTALYTOUCHED.


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Always insure thisprotective cover closed.Hazard of accidentaltouching to high voltage

points if kept open.

Controller On Offswitch makes controller

On or OFF but 440v isalways live andconnected unless Mainpower is off.

Never attempt to opencontroller lid when weldpower LED on frontpanel is glowing orwithout insuring

Weld powerLED indicatepresense ofphase 1 andphase 2

Ready LED :indicate machineis in weld modeand ready toweld. Start light : glows at

pressing of start switch. This light should beoff when foot switch isnot pressed

W.POWER READY START

STEP END CAUTION ERROR


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To start controller:Make sure weld power LED at top left is glowing. This light indicated the presence of phase 1and phase 2. If this light is off please check input connection of F1 and F2.

Make the controller on by reaching out on-off switch situated at back of the controller.

Controller with run through initial checks, showing 333 222 111 at all windows.

Select schedule 01 if not already selected.Put some values in welding parameters.To do so Press PROG/OPER values in some digit will be blinking now.Use curser < > to move blinking digit to squeeze window.By pressing + - select value for this field (say 18) .Move curser for next position by pressing >.Select (00) for weld1 ,(0) for cool1, (0) for slope 1,Select ( 12 ) for weld2 . This field indicates welding duration for main welding time,Select (00) for cool2 , (00) for wled2 ,(0) for slope 2 ,

Put value ( 08) in hold , this sets hold time for welding operation.

Put value (00) in OFF(pulse ) window. IF you select (00) machine will run in single cycle, forrepeat cycle select value = pause you need between to weld cycles .( 10 = 200 msec pausebefore starting next repeat cycle.)

Select valve (1)!. If output valve is connected to valve 1..Refer manual.

Press PROG/OPER AGAIN THE BLINKING WILL STOP . THIS COMPLETES SETTINGOF TIMING CYCLE.

Current 1,2,3 buttons: Setscurrent values to W1 , W2, W3

respectively.

Monitor on off :ON : current drawnin cycle is displayedin KA window 1andits %on set value inmonitor window 2OFF displays

setting values inwindow1

KA window1

Monitor window 2


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(YOU CAN TRY PRESSING PROG /OPER BUTTON AT ANY POSITION IF YOU PRESS ISTHE SETTING DIGIT WILL BLINK AND IF YOU PRESS IF AGAIN THE BLINKING WILLSTOP INDICATING THE VALUE IS SAVED)

Look for Curr1 curr2, curr3 buttons. The value in current window is corresponding to switchselected. The selected switch will glow.

Press curr 2 LED will glow on this switch---Enter value of secondary current required for welding.To do this press prog/ oper button bring curser in the window, select ( 08.0) and again pressprog / oper button.This means for weld 2 parameter you are selecting 8.0 Kilo Amp. As secondary current.Never select value beyond 15 KA. (Depends on machine capacity)

Look for mode switch. By repeated pressing values in MODE window will change. Selectmode (6). Press PROG/OPER button bring the blinking digit to DATA window by pressing>. Select maximum current ( 030.0) (differs from machine capacity) press prog/ oper again.

NOW the panel is ready for weld.

Check for air pressure ---set it to 3.5 ~ 4.2 bar

Pressure can be adjusted by lifting black knob upward and rotatingclockwise will increase the pressure. Pressing the knob down canlock the set value.It gets latched in one position.

Check for electrodes and its alignment.

Both electrodes should be in vertical plane.

CHECK FOR WELD BUTTON. This should be off for initial trials.

Confirm pressing WELD switch. The LED glowing shows welding on.

KEEP EVERY THING OFF THE ELECTRODES. TAKE CARE FOR NO BODY PART WILLCOME IN BETWEEN THE ELECTRODES.

Press foot switch electrodes should come down and go up completing the cycle.

If every thing is OK till this step. Make weld on by pressing weld

Switch. SOME MACHINES HAVE EXTERNAL WELD/ NO WELD SWITCH.


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-Put parts in the machine. Cycle the machine by pressing foot switch.

Welding current should flow and the value of this current flown will be indicated inCURRENT window. (Monitor display switch should be on )

If there is error error LED will glow. You can reset the condition by pressing error resetcheck for the reason referring manual.

PUT COMPONENT BETWEEN ELECTRODES; TAKE A DRY RUN.

TOGGLE WELD/ NO WELD SWITCH TO WELD POSITION.

NOW YOU ARE READY FOR WELD. ON PRESSING FOOT SWITCH WELDING WILL BEOPERATIVE.

ADJUST WELDING PARAMETERS TO SUIT THE COMPONENT.

FOR machines installed with pressure switch interlock : If the controller cycle isstopping at 'squeez please check air pressure or setting of air pressure andpressure swich. Machine will only operate if pressure set on pressure switchavailable .

This completes settings of the controller.

*Remember that exact parameters can only be decided by few trials.*All parameters (except ENERGY for W1, W2 & W3) are in terms of

Cycles, where 1 CYCLE = 20 milliseconds (1cycle of 50 Hz mains).


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IX. Important components in the machine

i. Transformer:Transformer is the heart of the machine.The transformers comes in various ratings i.e. 25 KVA, 35 KVA,50 KVA, 100 KVA etc. KVA = Kilo Volt Ampere.

It indicates maximum current X voltage delivered at out put for welding. Typically secondarywelding current is of the order of 10 KA (Kilo- Amp) to 20 KA for most of the applications.Primary side of the controller is connected to 440V AC between two phases. The One phase isconnected directly and other through thyristor, the electric regulator.The power can be made available at different tap levels.You can change the tap located at back side. Keeping common terminal at place change upperterminal lug.

There is thermistor switch located at bottom of the transformer it is connected to controller. Itshuts off welding in case of overheating.The transformer is water cooled. The water flows from the secondary coil .It takes away most of

the heat generated.Caution:

ALWAYS PAY ATTENTION TO COOLING OF THE TRANSFORMER. TAKE IMMEDIATEACTIONS IF THERE IS GENERATION OF OVERHEAT WITH IN ANY PART OF THEMACHINE.

ii. ThyristorThyristor controls energy to be dissipated through the part to be welded. It does it as per controlsignal received from the electronic controller.

This is very delicate device. It can get short or open like any electronic gadget. Please take carein proper earth of the machine. The variaster is attached across the terminal protects it form overvoltage spike. In such case this variaster getfused.

Care should be taken in connecting terminalsG1 G2 K1 K2The wire is soldered to the terminal withidentification ferrulesIn case of rewiring confirm four times is thewires are connected at G1 G2 K1 K2 of the

controller.

The device is cooled by heat sink. Water isalways flowing through it. For safety the waterpath is made series with transformer. In case ofrise in water temperature, thermo error isgenerated in controller.


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iii. ControllerThis machine uses AK 54, a current feedback controller.This controller sense current flowing in secondary of the machine and with feedback it correctsthe variation if any by controlling thyristor current. More facilities are available with this unit.Refer manual to know more about facilities provided.The current sensing coil is located at secondary of the transformer just behind the Bakelitecover.The best use of the controller can be done by using its current monitoring system. This systemcan instantly give alarm at the faulty spot.

X. Example on using current monitor.

While using current monitor you need to feed upper and lower limit to the controller. This can bedone as under:Example:Suppose your part requires 10 KA current for 8 cycle .

And your setting is as under

30 00 0 0 8 0 0 0 5 0

sq Weld1 Co1 Sl1 We2 Co2 We3 Sl2 hold off

And0 10 0

Curr1 Curr2 Curr3

(Insure you are putting value in curr2, this can be done by pressing curr2 button and insuring theled over the button is glowing. Also insure values in curr1 and curr3 by pressing respectivebuttons. If there is value in weld 1 , it corresponds to curr1 ; value in weld2 and weld3

corrosponds to curr2 and curr3 respectively. If you put some value in weld1 and 0 in curr1 thiswill result in error)

This setting means you need 10 KA current for good part.Press MONITOR DISPLAY button, insure the LED on the button is glowing.

Monitor display ON will give you actual current flown during the process this value will bedisplayed at window immediately above the curr2 button; Its percentage over set value ofcurrent will be displayed at the window above monitor display button.

Observe actual current flown, displayed in the window, and its percentage over set value (10KA)If the % difference is better than +/- 5%, your setting time is OK (else try to increase weld time).Make destructive test and confirm parameters OK for weld strength. After getting OK result movefor next step.

Calculate 10 % less of the set value (i.e. 9 KA)

Set 09.0 KA in curr2 window.Make a weld.Observe actual current drawn.Make destructive test for weld strength.


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If the test is ok,We can conclude 9KA current is also OK for making good weld.If you get test fails, Increase default value and repeat the procedure or insure your self, by trialand error correct lower value of current.

Accordingly set upper value. And calculate safe % of upper limt.In this example Now we have

9 KA as lower limit. ( 10% lower)10 KA set value10.5 KA as upper limit (5% high )

Now we can set upper and lower limit on controller monitor.

Push prog buttonPush lower limit button (- % limit)Enter 10Push upper limit ( +% limit)Enter 05

Push prog again

Take weld.Now the controller is programmed for upper and lower limits.It will give alarm (error output) at the instant the actual current fall beyond the go nogo limit.

Pressing error reset button can reset error alarm.There are other few other errors related to setting and maintenance of the controller. Pleaseread the error no. Details from the manual page 36.

We can also use other powerful function built in .

LikeElectrode wear compensationMultiple program callingInterlocking with other inputs.Computer interfacing for data download

Please refer FORWEL AK54 manual for details supplied with this booklet.


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XI. Setting Up and Making Resistance Welds

Given there mutiple variable in resistance welding, the key is to identify each of your variablesand minimize their change. When changing any one variable you must consider the influence onthe remaining variables. A reduction in time can increase demand for current, and a reduction inforce will decrease demand for current to reach welding temperatures. Document all changesand develop history of tests you make in developing your weld schedule.

Precise control over welding temperature is vital in resistance welding operations. The primary

variables affecting weld formation are heat, time, and pressure. Resistance welding equipment isdesigned to, 1) provide current, 2) exercise precise control over time and current and 3) supply aforging pressure with rapid follow-up. The following profile addresses important variables andsteps to follow in making a resistance weld. This introductory summary is followed by aprocedural analysis, which discusses each of these steps in greater detail

i. Welding ElectrodesSelect the proper electrode material or materials for metals being welded

Determine electrode geometry. If a standard shape electrode is not suitable for your operationan electrode should be designed to properly address the part/electrode interface The finalelectrode design should be easy to change with sufficient to access for maintenance.

ii. Electrode InstallationInstall the electrodes into electrode holders, and align. Electrode holders are typically adjustablefor both vertical and rotational positioning. Careful attention should be taken to ensure that thealignment is correct and. Electrode alignment should produce an even footprint, allow for theeasy insertion and removal of the parts, plus provide access to clean the electrode on themachine. In some cases electrode geometry in critical and will require cleaning off site.

iii. Setting Weld ForceMake sure the power source is shutdown and set electrode force using an electrode forcegauge. Most weld heads have an indicator that typical displays some nonlinear reference to theforce and should not be mistaken as actual force values. The use of a electrode force gauge isrecommended

Place the parts between the electrodes; actuate the top electrode to meet the parts. Carefullycheck to see that proper contact is being made. Determine if the effects of the pressure alonecauses any serious deflection of the electrodes and or deformation to the parts.

Turn the power on and set the heat control to low amplitude and time settings. Begin bygradually increasing the values to produce the required temperatures to form the weld .If themaximum power settings are reached before a proper weld is obtained; gradually decrease thepressure between successive trials. This procedure will increase the contact resistance between

the parts and increase the temperatures generated at the interface. (Note: A minimum amount ofelectrode force is required to stabilize the contact resistance between the electrodes and theparts). If the force is to low electrode sticking and expulsion of molten material will result.

The settings you begin your study with are not as important as the documentation of thechanges made and their respective results. To minimize the complications in developing a weldschedule do not attempt to change more than one variable at the same time. Evaluate each weldfor the strength and requirements of your particular application . Once the parameters have beendetermined fully document the process variables and publish in your manufacturing records.


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iv. Electrode SelectionElectrodes can be in the form of a rod, plate or incorporated into a special fixture. Electrodematerials are specific alloys designed for a range of conductivity and hardness. RWMA standsfor, Resistance Welders Manufacturing Association and they have identified a range of alloys.RWMA2, 3... can be also be referred to as Class 2, 3... Also, some materials are identified with a"Mallory" number. Your selection is based on the alloys ability to withstand the specific demandsof you application.

Electrodes simultaneously, conduct electrical current to the weld site, and conduct thermalenergy away. In welding resistive materials a conductive electrode pulls heat away fromelectrode / part interface, ensuring welding temperatures are only achieved at the parts interface.Welding temperatures develop at different rates depending on a materials mass and/orcomposition. Keep in mind, when welding dissimilar materials, heat generates at different rates,and two different electrode alloys may be required. To control the even heat generation in bothparts, electrodes of varying conductivity and or shape are used. For example, a larger diameteror more conductive electrode allows surplus heat to exit from a thinner material while a heavierpart reaches welding temperatures. This is referred to as Heat Balance. Changes in electrodematerial and geometry are used to ensure good heat balance.

Fundamental electrode selection calls for a conductive electrode when welding resistivematerials; and resistive electrodes when welding conductive materials. . The parts mass andcomposition are used as guidelines in the proper selection of the electrode material.

v. Electrode MaterialCopper is a commonly used electrode material due to its high electrical and thermal conductivity.To withstand the welding environment, copper is alloyed with other elements. For example,copper strengthened by the addition of aluminum oxide particles offers higher wear resistancethan traditional Copper-Chromium welding alloys. Oxygen-free copper should be avoided, due totheir low tensile and yield strength at elevated temperatures electrode deform quickly.

Established standards for welding alloys by the Resistance Welders Manufacturers' Association(RWMA) include a range of copper and refractory alloys. Some of the most common alloys usedare: RWMA Class 2 - Copper-Chromium Alloy used to weld resistive materials; RWMA Class 3 -Copper-Cobalt-Beryllium Alloy has the same general applications as the RWMA Class 2, but thismaterial sacrifices conductivity for increased hardness; RWMA Class 11 - Copper-Tungsten

Alloy is used in applications where high electrode force and conductivity are required; RWMAClass 13 - Tungsten. Class 13 materials are used for conductive alloys; RWMA Class 11 orMolybdenum electrodes are similar in conductivity to RWMA 13 materials, but Class 11 materialsare easier to machine. In summary, always fabricate the electrodes using a resistance weldingalloy.

vi. Electrode DesignWhen designing electrodes, consider ease of manufacturing, replacement, and maintenance.Electrode design is governed by part thickness, composition, shape, size and the required weldsize. Electrode geometry establishes current density in the weld site. The force applied by theweld head on the electrode influences current density in the weld site. The electrodes alsomaintain intimate contact between the materials and provide a forging action during theformation of the weld. Concurrently, they dissipate heat from the weld site, preventing surfacefusion between the electrode and the parts.


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The electrode face is directly above the point of fusion, and this area is subject to repeatedexposure to high temperature and pressure. If electrodes overheats and begins to fuse with thematerials being welded, consider increasing the electrode force, diameter, conductivity or usewater cooled electrodes.

Another important factor in determining electrode shape is accessibility to the weld site. Theweld site does not always allow for a basic straight shank electrode design. Limited access mayrequire offset, or angled electrodes. With offset electrodes, ensure the electrode diameter is

sufficient to transmit the required pressure and current without distortion.

When changes to electrode design and material fail to produce desired results projection weldingtechniques may offer a solution. A projection or dimple formed, typically in the thinner part,focuses welding current to assist in issues with heat balance or great difference in parts mass.

vii. Electrode AlignmentThe preferred electrode alignment is vertically opposed because is force exerted is one of simplecompression. Careful attention to electrode alignment is important; if the centers are not aligned,the net effective tip area is reduced. When electrode tips are not parallel the pressure andcurrent is confined to a fraction of the designed area, and destruction to both the electrodes and

the parts is likely.

viii. Electrode MaintenanceElectrode tips will eventually become pitted or spattered with weld material. They requireperiodic maintenance to reshape and/or clean the welding surface. Often, files are used as amaintenance tool for cleaning. This not recommended, files easily alter shape and surface finishof the electrode. A preferred electrode maintenance material is emery paper. Specially shapedelectrodes must be cleaned and dressed with consideration given to retaining original contours.Standard flat-tip electrodes of equal dimension can be reshaped very simply as follows:

Choose an emery paper of #400 to #600 grit. Fold the paper so that abrasive surfaces areexposed. Hold the emery paper between the electrodes and carefully bring the electrodestogether so that both tips are in light contact with the emery paper.

Rotate emery paper in circles between the tips, or pull it in alternating directions. Continue thispolishing operation until both tips are clean and smooth and are in good contact with each other.

A small dental mirror provides easy inspection. Care should be taken to keep the plane of theemery paper horizontal and perpendicular to the long axis of the electrodes. Commerciallyavailable emery cleaning disk adhere emery paper on heavy paper disk. Keep in mind the paperbacking is soft, and electrodes will tend to form a radius by simply spinning these disk betweenelectrodes. If you electrode are of different size, a ridged substrate between the emery paper isrecommended. In some cases ceramic is used to clean electrodes.

Remove emery paper and metal by products from the tips with either a brush, or flush withalcohol. Adding a small amount of alcohol to emery paper before cleaning operation canminimize the accumulation of cleaning by products on the tips and weld station.

ix. Pressure SettingsElectrode pressure forces the materials to be welded into good contact with each other before,during, and after welding. The effect on the weld is a forging action. The electrode pressure is


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indicated on the weld head and graduated in relative units. For precise work, a force gaugeindicating actual pressure obtained is recommended. The pressure should be high enough torender the surfaces of the materials uniform in electrical resistance. Forces set to low can causedramatic changes in current density and may be evident by pitting of the electrode surfaces.

Pressure should not be confused with "follow-up." Follow-up is the ability of the welding head tofollow the minute expansion and contraction of the weld during heating and cooling. This actionmaintains a constant forging action during the manufacture of the weld and insures consistent

weld uniformity. Low-inertia and friction are important to providing rapid follow-up during a weld,and are feature of a good weld head design.

x. Heat SettingsAlways start with low weld current and time settings and work up to the optimum weld results.Power supplies provide several output options including: multiple pulses, off time, upslope, downslope and polarity. A standard technique used to displace plating and or oxides is to use a dualpulse weld where a lower amplitude first pulse is followed by a higher amplitude second pulse.Off time settings are used to cool or quench the weld between pulses. Upslope feature graduallyincrease or decrease current into the parts, and is beneficial when welding materials that are

sensitive to heating and cooling rates. Polarity settings, positive and negative are used toappoint a specific direction to current flow through the parts.

Requirements of the materials being welded determine what methods of heating are necessary.Keep in mind, heat loses by conduction into surrounding parts and electrodes, as well asradiation into the surrounding air. These losses are essentially non-controllable, increasing withincreases in total time. At some period during an extended welding interval, the radiation losseswill equal the heat input, thus stopping further temperature rise.

Factors affecting the amount of heat being generated by a given weld current for a unit of timeare:

1. The electrical resistance of the materials being welded2. The electrical resistance of the electrode materials3. The contact resistance between the parts as determined by surface conditions, scale, weldingpressure, etc.4. The contact resistance between the electrodes and parts as determined by surface conditions,area of electrode contact and welding pressure.

xi. Time SettingsGenerated welding temperatures is a linear function of time. Heat may be affected either by achange of current or by a change of time. Finite values of time are required before any weld is

formed. The exact minimum length depends upon current magnitudes, material thickness andcomposition. If weld time is to short now weld will form, regardless of the increase in current.

xii. Testing the WeldThe most reliable test of weld quality is its strength compared with the strength of the materials

joined. A very simple and practical test is described below:

After joining two pieces of sheet metal with one spot weld, peel them apart. If one of the twopieces fails or has a hole in it the weld should have adequate strength. If a hole pulled in one of


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the materials has a diameter at least twice the thickness of the thinner material the weld isprobably as strong as can be obtained.

Note, the above information has no mention of the variables regarding materials being welded.There is plenty to say about material variables, but for now just remember variables left un-monitored can shut your production down. A change in vendor or materials should be closelymonitored to ensure optimum welding results.

What Next?

You now have some basic information to assist you in your welding operations. If it is helpful toyou please let us know.


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XIII. FAULT FINDING:

Problem 1---Welding Machine Is Dead

One common indicator of this problem is no light or displays are working on the welding control.A simple test with a voltmeter at the incoming power source to the welding control should show if

power is coming into the box.Dont measure from one power line to the cabinet ground or the conduit. This can give falsereadings because voltage runs through the welding transformer and shows a reading to thecabinet metal, even if one side of the power line is dead.If power is present, check the welding control for small power fuses, making sure that power isturned off to the equipment before removing fuses for testing.Check for continuity on these fuses.If the fuses are fine, power can be turned on and the voltage into the control measured.Ensure the reading is a normal 440 volts across phases and 220 V betn neutral and phases.Make these measurements at controller and machine terminals.

Any blown fuses should be replaced with ones of exactly the same type and rating. These fuses

are selected by the manufacturer to protect the electronic components.

Problem 2---Control Has Lights but Will Not Cycle

If closing the foot (or hand) initiation switch does not elicit an action, the most common cause isa bad switch.Check this switch electrically by multimeter. Or shorting link.The fact that a switch mechanically closes does not guarantee that the welding control will cycle.Switches are designed for high-current switching (amps). Welding control uses low voltage andvery low current (milliamps) for initiation. Over a period of time, the contacts inside a switch canform a very thin oxide layer that block conduction of electricity.

To check this unwire the initiation switch and replace it with another switch. If the machine thenoperates, the problem is solved.

Problem 3---Machine Cycles, but Tips Do Not Close

If the machine cycles but the welding electrodes will not close; it could be the result of a bad airsolenoid or a non-electrical problem, such as insufficient air to the system.check that sufficient air pressure (typically 2.5 ~3 Kg/cm sq minimum) is shown on the airregulator's gauge.If air pressure is present, the solenoid valve that operates the machine's cylinder with a manualoperating screw., operate it to see if the cylinder operates. If it does not close the welding

electrodes, the solenoid valve should be replaced.If the manual operator works in this test, the problem might be in the solenoid valve coil or thewelding control valve drive circuit. To check these, locate the terminals on the welding controlthat provides voltage to the welding solenoid valve.controls uses 220 volts AC to operate the solenoid coil, the solenoid valve coil's nameplateshould be checked to confirm this. With the equipment initiated, control's output terminals forvoltage when the system has been initiated.


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If voltage is present and the valve does not operate, the test should be repeated on wires at thecoil end. If voltage still is present and the valve still does not operate, the valve coil should bereplaced.If no voltage is present, output fuses for the control's valve terminal should be checked. If theseare all right, the problem probably lies in the control.

Problem 4---Welding Electrodes Close, but No Weld Occurs

If the welding electrodes close but no weld occurs, one of the following maintenance tips may beappropriate.Controller Key lock switch is in set mode, make controller keys at proper position forwelding.i.e. keylock sw at run mode . It was observed on overturning this switch (if it is loose ); causeswire soldered to sw broken .energy setting at weld 2 is not selected or selected very low. Check schedule and putappropriate values.Problem in Machine's Secondary. By far, the most common cause of this condition can befound in the machine's secondary circuit.It is not uncommon for welding electrodes not to touch the part after they have been adjusted or

after new ones have been installed. The welding machine should be adjusted so that at least 10mm more travel (over travel) is available after the electrodes have touched.

Another very common problem occurs when someone has wrapped Teflon tape around theelectrodeshank to stop water leaks. This certainly stops the leak, but, unfortunately, it alsoelectrically insulates the electrode.

A good way to test the secondary of the welding machine is to first turn off the power. Then, withthe electrodes open, the continuity between the top and bottom electrodes should be checked.If the secondary is working, the measurement should be about 1 ohm or less. If the reading ishigh, go across each mechanical junction of the welding machine secondary until a high value isfound.Heavily used spot-welding machines commonly have oxidized connections. If this is the case,

the connection should be opened and the surfaces cleaned with a fine abrasive and polished.The use of coarse abrasives will make the problem worse a few years down the road.Terminal connection pads are plated. These junctions are conducting thousands of amps.Secondary connections should be tightened fully, and questionable bolts always should bereplaced.NO-WELD Switch Problemcontroller NO-WELD switch should be in weld position to initiateweld.

Problem 5---Major Metal Expulsion When Electrodes Close

Major metal expulsion occurring just as the welding electrodes touch, blowing copper and metal

sparks , is another common resistance welding equipment problem.Often, the welding electrodes will even "weld" together. In this case, one of the followingproblems may be responsible.

1.The welding machine was fired too soon.

Expulsion usually occurs because too little time is allowed for the required welding forcebetween the welding electrodes to be achieved before welding current starts to flow. In this case,the electrodes close "live" and act like an arc-welding machine.ensure that the squeeze time set in the program is long enough. This squeeze time is set inhalfcycles (1half cycle = 1/120 second).


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This setting is directly proportional to initial distance between top and bottom electrodes more isdistance, more should be squeeze time.2.Leakingwelding cylinder.Expulsion also can occur if the welding machine's air cylinder has a large internal cup seal leak,which prevents the cylinder from producing the required welding force.Welding with very low force causes major expulsion and electrode sticking. If the cylinder hasthis internal leak, air comes out of the solenoid valve's exhaust port when the welding electrodesare closed.

Problem 6---Welding Electrode Meltdown

If the electrodes close "live," weld together, and continue heating until they have been reducedto a molten glob, the operator probably has pulled the disconnect before calling maintenance.There are two possible causes for an electrode meltdown.

Values of weld time and energy selected very high. Recheck schedule parameters.

Transformer grounding. One possible cause of welding electrode meltdown is a weldingtransformer with a primary winding that has become shorted to the welding machine case. While

this is a fairly unusual condition, it can happen.A resistance welding control switches voltage only on one side of the power line. The other sideof the power line goes directly to the welding transformer.To test for this condition, the technician first should turn the power off and then remove the wiregoing from the silicon-controlled rectifier (SCR) contactor to the welder transformer, and theninsulate the end of that wire.With the power then turned on, a weld sequence should be attempted. If the problem still occurs,the transformer should be checked and probably replaced.

SCR contactorshorted.A more common problem is a shorted SCR contactor. This deviceactually is two SCRs mounted in a single water- or air-cooled assembly.

SCR contactors normally operate for long periods without problems, but they can fail.Unfortunately, 99 times out of 100, they fail in the shorted condition.SCR contactors fail either because of excessive internal heat or because of a high-voltage spikeacross the device.Excessive internal heat can occur when the SCR contactor is not being cooled properly. On awater-cooled SCR contactor, the flow of cooling water through the SCR heat sink should be atleast a 20 liters per minute. If there is a restriction or if the back pressure on the return hose istoo high, water will not flow properly.High voltage can happen when lightning strikes an outside power line or when the weldingmachine is run with excessive expulsion for a long period. A properly sized SCR contactor

should have a voltage rating of at least three and a half times the line voltage.There is a metal oxide varister (MOV) installed across the SCR contactor to clamp high-voltagespikes around the switch. When an SCR contactor is replaced, this MOV also should bereplaced as preventive maintenance.The SCR contactor is used as a solid-state switch to pass electricity to the welding transformerwhen the weld is made. At all other times, it should be an open switch. If the SCR contactor isshorted, electricity flows through the welding transformer constantly.


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Shorted SCR contactor test. If the technician suspects that the SCR contactor has shorted, avoltage meter can be installed across the two large power terminals.When power is turned on tothe control, the line voltage should be present across these points (unless the control has anisolation contactor installed).If the line voltage cannot be read at these points, the technician should turn the power off to thecontrol and disconnect the wire going to the welding transformer. With the power still offcontinuity across the same two terminals should be measured.If the SCR is shorted, it will read about 1 ohm. If the SCR is not shorted, the reading will be

1,000 ohms or more. This usually is a reading of other components, such as snubbers, that areinstalled across the SCR contactor.

Problem 7---Loud Transformer Growling, Saturation

A properly operating welding transformer has a smooth humming sound when welding. If,however, the operating sound suddenly changes dramatically, the system has a problem.When this occurs, continued use of the machine can cause permanent damage to the weldingtransformer and the SCR contactor. Under this condition, line fuses sometimes blow or circuitbreakers open. Also, welds that are produced will be very weak or might not stick at all.This problem often occurs when the welding transformer is operated in an unbalanced condition

in which the AC that flows into the transformer is more in one polarity than the other.The difference produces a direct-current component in the welding transformer and causes thetransformer to go into the saturation condition. When this happens, the primary current (linecurrent) will jump from hundreds of amps to thousands. This excessively high amperage cancause the power wires feeding the machine to slap within their conduit.

SCR Problem. One cause of saturation can be a bad SCR contactor. This is quite rare, but itcan happen. In this case, only one polarity of the line voltage is conducted.The SCR contactor actually is an assembly of two individual SCR elements installed back-to-back. One of the SCR elements conducts the positive side of the AC line, and the secondconducts the negative side.

If all are working correctly, these SCR elements are fired alternately at the same timing (relativeto the line voltage frequency) to provide balanced AC to the welding transformer. However, ifonly one of the SCR elements operates, the welding transformer saturates quickly.Take following steps to test operation on both sides of an SCR contactor that has been removedfrom the welding control:1. Connect two 1.5-volt batteries in series with a 3-volt flashlight bulb across the SCR contactor.2. Touch the gate wire from either SCR to the + side of the battery pack as shown. Note that thegate wire is connected to the center of each individual SCR. If the light does not turn on, connectthe gate wire from the remaining SCR to the + side of the battery pack. The SCR should stay on.Once the light is on, remove voltage from the gate wire. The SCR should stay on.3. Momentarily touch a wire from one side of the SCR contactor to the other, and the light will

become very bright. Remove this wire and the light should go out.Now, reverse the battery pack/lamp wires to the SCR contactor and repeat the same test withthe remaining SCR gate wires.If both sides check out properly, the SCR is operational.

Control Problem.Asecond cause of saturation is an improperly operating welding control.Controls synchronize firing of the SCR contactor to the line voltage frequency. If the circuitry isnot operating properly, weld transformer saturation occurs.

Also, controllers have fuses on the SCR firing circuits. check these fuses and replace them ifthey are blown. Additionally, firing wires (gate and cathode wires) coming from the SCR


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contactor to the control should be checked to ensure that they are connected properly andtightened.

Another cause is minimum firing angle setting is put too high so as to overlap with next weldingcycle.The procedure to set min firing angle is given in the manual but please be very careful as this isa system setting and should be done under instruction of manufacturer. and is not required tochange unless the controller is changed or used for other machine.


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Fault Observation Possible reason Possible solution

Controller not cycleon pressingfootswitch and nocylinder movement

Controller display off No control power. Fuseblown off

Replace fuse

Isolation controltransformer faulty

Replace

W.power LED off No power 440 V restore

Controller display on'ready LED ' do notlit after pressing FS

No input signal/ faultyfoot switch

Check foot switch /connections

Ready LED lits onpressing foot sw

Solenoid coil bad or nosupply to solenoid

Check solenoid coilpower supply; changesolenoid coil

Air pressure insufficient Check /restore air supply

Controller cycles onpressing foot switch ;cylinder operates butno welding

Cylinder goes backafter removing footswitch signal

Insufficient pressingduration

Press foot swich forlonger

Wrong input signalconnection to 1ststart

Contact electrician ,check input to start1 *

Cylinder stops atsueeze,Squeez datadisappears .

Interlock hold, pressureswitch setting ;pressure switch faulty

Adjust input pressure andpressure switch setting, ifother interlock is provided,check the interlock.

Cylinder operatenormally ; no error;no welding ; readyLED not on

Weld no weld switch off Check external weld noweld ; and weld no weldswitch on controller ,.

short link 12~13 open Connect short link

Error 21 oncontroller

Several resonspossible

Check error list andcause in controllermanual

Improper contact due

to rust, carbon

Observe for heating;

Clean secondarycontacts

Teflon tape in electrodePhase1 , k1 mismatchif controller rewired/reinstalled

Remove teflon if put onelectrodes of waterleakage ; use taperreamer to clean taper

Contact expert electricianinterchange ph1;ph2*


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XIV. Spare parts List

Sr.No.

Item Specification Make

1 Control Transformer 440 V in, 230v, 25V out Kirti

2 Lower Electrode SK 3430AsiaAutomotive,Nasik

3 Upper Electrode SK 0003AsiaAutomotive,Nasik

4 Linear bearings LME 50 UU THK

5 Copper Flexible 75mm Width X 350 Length Kirti

6 Pneumatic Connectors/ tube Push in Type Festo , SMC

7 Electrode Holder SK1215 250 OR 300 LENGTH.Asia AutomotivePh-0253-2350165

8 FRL Unit FRC 1/2 "Janatics

9 Coil for valve MSFW 230 (4540) Festo

10 Pneumatic Valve MFH 5 1/4 p no. 6211 Festo

11 MOV variaster 420 V Kirti

12 Thyristor assembly 504 Water Cooled AssemblyRectifierHouse,Mumbai

13 Digital weld controller AK54 V 230V Forwel Kirti

14 Transformer 50 Kva Kirti


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Circuit Diagram

XV. Circuit Diagram


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StandardStartingParametersForNutProjectionWelding

Nut

Lower

Sheet

(mm)

Pressure

(K

gf)

Squeeze

(Cycles)

Weld1

(Cycles)

Cool1

(Cyc

les)

Slope1

(Cycles)

Weld2

(cycles)

Cool2

(cycles)

Weld3

(Cycles)

Slope2

(Cycles)

Hold

(Cycles)

Cu

rr1

(kA

)

Curr2

(kA)

Curr3

(kA)

M6

0.8

2.5~3

20~25

0

0

0

4~6

0

0

0

4~6

0

7.5~

9.5

0

M6

1

3~

3.5

20~25

0

0

0

5~7

0

0

0

8~12

0

8~10

0

M6

1.5

3~

3.5

20~25

0

0

0

5~7

0

0

0

10~14

0

8~10

0

M6

2

3~

3.5

20~25

0

0

0

6~8

0

0

0

10~14

0

10~12

0

M8

1

3.5~4

25~30

0

0

0

6~8

0

0

0

12~15

0

10~12

0

M8

1.5

4~

4.5

25~30

0

0

0

6~8

0

0

0

8~15

0

10~12

0

M8

2

4~

4.5

25~30

0

0

0

8~10

0

0

0

12~17

0

12~14

0

M8

3

4~

5

25~30

0

0

0

8~10

0

0

0

12~17

0

12~14

0

M10

2

4~

5

25~30

0

0

0

8~10

0

0

0

12~20

0

12~15

0


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KIRTI PRESSINGS PVT. LTD.W-35,MIDC Waluj,Aurangabad,Maharashtra,431136,India.

Website: http://www.kirtipressings.com email: [email protected]: +91-240-2554596/555502 Fax: +91-240-2551233

ac resistance welding machine manual 50kva

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