Seam welding (RSEW)
Seam welding, a type of resistance welding process, uses the resistance to electric current through the metal pieces to get the weld joint, as the pieces are held under pressure by electrodes. Seam welding is widely used where strings of spot welds re required or leak-tight joints are required. However, uses of this type of welding include creation of flange welds, watertight joints for tanks, drums, tin cans, and domestic radiators, etc.
Seam welding uses a complex control system, which involves the travel speed as well as the sequence of current flow to provide for overlapping welds. However, the timing schedule, spots per inch, and the welding speed are interdependent of each other. The pressure, current, and the size of the weld are provided by the welding schedule.
Various types of seam welding
Seam welding is mainly of three types, viz., standard seam welding, mash seam welding, and roll seam welding. These different seam welding process differ in their equipments used, and also in the product applications for which they are used. A little description of each seam welding type is given below:
Standard seam welding
Standard seam welding is used to create continuous leak tight weld nudges, as the wheel electrodes rotate along the pieces to be welded and a continuous current passes.
Mash seam welding
This is a variant of seam welding process in which sheets are overlapped, usually one to two times, and mashed along with the passage of current and a solid-state joint is created in the process of mash seam welding. The thickness of the weld is about 110-150% of the original thickness; however, can be reduced by reworking.
Roll seam welding
Roll seam welding is used to create a line of spot welds, which are not leak-tight joints. In roll seam welding process overlapping of sheet does not occur, and therefore, the leak-tightness of the joint is not achieved.
Advantages of Seam Welding
Resistance welding processes, in general, are not that very easy to use; however, their application and advantages make them one of the most used ones! Some of the advantages of seam welding process are given below:
" Formation of leak-tight welds
" Speedy processing times
Seam welding process, like any other manual welding process, involves risks to the operator; however, using certain precautions can minimise them. Some of these precautions are listed below:
" Installation of all Seam Welding equipments should be done by a qualified electrician. There is no scope of a make-break system that acts as a pseudo system!
" To prevent the access to some unauthorized person, all doors and access panels of equipments should locked, as there is potential risk to anyone unskilled and going near the equipment.
" While applying pressure, if the fingers of the operator are supposed to be under the line of action, proper guard should be provided, which may include an electronic eye safety circuit and two hand controls.
" To prevent accidental operation of the machines, all foot switches should be effectively guarded.
" Two or more emergency buttons must be there on special welding machines.
" Safety glass is also suitable to prevent flying sparks, and should be used wherever applicable.
Seam Welding Resources