Projection Stud Welding|Capacitor Discharge Method

INTRODUCTION:

 Projection Stud Welding is the method of welding studs or fasteners of various shapes and diameters onto a parent material without making holes. This is the fast and economical method of fixing studs, normally you have to adopt operations such as drilling, tapping for mounting the studs of the work piece. By using this method you can completely avoid these operations.
Projection welding is an electric resistance welding process that produces welds by the heat obtained from the resistance to the flow of welding current. The resulting welds are localized at predetermined points by projection or intersection. The major factors that should be considered are Welding current, Weld time, Electrodes/Dies, Electrode force. 

TYPES OF PROJECTION STUD WELDING:

There are two types of Projection Stud Welding:
1.Capacitor Discharge Method
2. Drawn Arc Method
Selection of process depends upon thickness of parent material,diameter of stud, weld strength required and welding aesthetics requirement.
Drawn Arc Method is used for the higher diameter studs and heavy parent material.
Capacitor Discharge Method is used for thinner material and small diameter studs.

Capacitor Discharge Method
In this method small projection (pip) at the end of the stud makes contact with the work-piece and energy from the bank of charged capacitors is discharged across the contact,melting the stud projection and creating a shallow molten pool in the parent plate. At this time stud is pushed into parent material under spring pressure,completing the weld.
Energy required for given welding operation is obtained by selection of voltage across the capacitor.

SYSTEM IMPLEMENTATION

230 volts AC single phase supply is given as an input. then 230 volts is step up by using step up transformer  ,input is given to the phase control .phase control adjusts the phase in between 0 to 180 degree , rectifier rectifies  converts AC into DC.  Storage capacitor stores the energy. There are 3 inputs to microcontroller. Microcontroller sends the command   to power control card. It sends command to phase control. SCR   acts as a switch .A gate triggering method is used turn on the SCR.


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HARDWARE SPECIFICATIONS:

Primary Voltage: 230 V, AC, single phase

Input frequency : 50/60 HZ

Current source: Capacitor

Capacitor rating : 33000 mfd / 200 volts

Maximum charging voltage : 190  volts

20x4 alphanumeric display cum keyboard