BASIC GAS METAL ARC WELDING All MIG welders have the same 4 basic systems POWER SYSTEM: Converts alternating current (AC) into the direct current (DC) used to produce the arc. The Power System also delivers current to the end of the torch where the arc is established. WIRE DELIVERY SYSTEM Provides the force and conduit needed to move the wire through the torch in a consistent and smooth manner. SHIELDING GAS SYSTEM The Shielding Gas System delivers inert gas from the gas source to the end of the torch. CONTROL SYSTEM Regulates and adjusts the settings necessary to perform welds on metal.

Maintaining and setting up of the welding equipment is the most frequent maintenance task performed by the Welder/Fabricator. These are general procedures which will minimize the operator to unnecessary hazards. OPERATORS SHOULD ALWAYS REFER TO THE MANUFACTURERS’ MANUAL FOR EACH SPECIFIC PIECE OF EQUIPMENT. STEP 1 Turn off the welder! Using your Welpers cut off the welding wire at the end of the torch and remove the gas nozzle, contact tip and gas diffuser from the end of the torch.

Gas Nozzle: Contact Tip: Gas Diffuser: Directs shielding gas over the molten puddle. Requires cleaning periodically to maintain proper gas flow. Contact Tip: Transfers current from the power source to the end of the wire. The size of the opening must be matched to the diameter of the wire. The diameter of the contact tip will open up over and will need to be replaced periodically. Gas Diffuser: Allows shielding gas to enter the gas nozzle and holds the contact tip and nozzle in place. Obstructions may effect gas flow.

STEP 2 (Changing to a different type wire) Release tension on wire. Carefully back up the roll of wire with one hand, while with your other hand, keep tension on the wire. DONOT let go of the wire at any point during this step! When the end of the wire comes through by the drive rolls, carefully place the end in one of the holes in the spool and bend the end over so the wire cannot unravel. STEP 3 Carefully disconnect the connector from the torch to the power source (1) by turning the connector where it attaches to the power source. Open the cover on the side of the power source and loosen the wing nut that holds the torch in the wire feeder (2).

Identify: the liner (1) o-ring seals (2) shielding gas holes (3) and the shoulder (4).

Purposes of components: Liner: Guides the wire through the torch. Over time the liner will become clogged causing wire feed inconsistencies resulting in erratic arc. The liner should be blown out with shop air after each changing of the wire spool. O-Ring Seals: Prevents air from entering the shielding gas system. They may become damaged over time resulting in contaminated shielding gas. This is a potential cause for porosity. Shielding Gas Holes: The shielding gas holes allow shielding gas to enter the welding torch. Shoulder: The shoulder is the fixed alignment reference for inserting the torch into the wire feeder. Failure to insert the torch to the shoulder will misalign the o-ring seals in the torch with the shielding gas inlet. This will result in shielding gas contamination.

STEP (4) (Changing an empty roll of wire) Grasp the wire at location (1). Using your welpers, cut the wire at location (2). Failure to correctly follow this sequence will cause the wire to unravel when the wire is cut. Take the end of the wire and insert it into a hole on the spool (3) and bend the wire so it remains in the hole. You may now release the retaining ring and remove the spool of wire.

Identify: Drive roll tensioner (4) Drive roll (5) Inlet Guide (6)

Purpose of components: Drive roll Tensioner Adjusts tension between the upper and lower drive roll. The tension must be firm enough to consistently move wire through the torch, but, low enough to prevent bird nesting when a burn back occurs. Drive Roll The drive roll forces the wire through the torch and out the contact tip. It has grooves and the size of the groove must be matched to the diameter of the wire. Inlet Guide The inlet guide is a tapered insert and is located where the wire from the spool enters the wire feed system.

Identifying the wire classification and diameter. The meaning of the classification system. E Electrode The end of the wire is the location where the arc is. R Rod The wire becomes the weld deposit. 70 70,000 PSI The tensile strength of the wire. S Solid The wire is solid metal. 6 Chemical Composition The different elements and the amount of each in the wire. In most cases it is necessary to replace the spool with the same wire and classification when the wire runs out.

STEP 5 Shielding Gas Tank/Regulator Identify: Tank valve (1) Relief valve (2) Tank pressure gauge (3) Flow Gauge (4) Regulator adjusting screw (5)

Purpose of components: Tank Valve Opens and closes the compressed gas cylinder. Pressure in the tank can be up to 2500 PSI. Must be turned all the way open or all the way closed. Relief Valve Opens automatically to relieve pressure if tank pressure becomes too high. Tank Pressure Gauge Indicates the pressure in the tank. Usually measured in PSI (Pounds per Square Inch). Flow Gauge Indicates the flow of gas to the welder. Usually measured in CFH (Cubic Feet per Hour) Regulator Adjusting Screw Changes the flow of gas to the welder. Turning the adjusting screw in, increase the flow rate. Backing out the adjusting screw decreases the flow rate. Set the regulator at 15-18 CFH.

High Pressure Gas Cylinders High Pressure Gas Cylinders require certain procedures to handle them safely 1. Prior to the removal of the metal safety cap, the tank must be secured. This is commonly done by chains or straps. This is done to prevent catastrophic damage to the bronze valve it protects. Damaging the tank valve may result in serious injury to the person/persons in the area. 2. Prior to tank being removed from the secure place, the metal safety cap must be reinstalled.

3. Tanks come in different sizes and you may need assistance from another person too handle them. They are identified by the type and volume of gas they hold. 4. They must be transported upright, with the metal cap installed.

Attaching the Regulator to the Tank Regulators must be in proper working order. If you find the regulator is damaged, tag it and find a regulator that’s working properly. Repair of regulators must be performed by certified personnel. They must be kept clean and free of oil. Once the tank is secured and the tank cap has been removed we will need to attach the regulator. Stand to the side of the tank and open the tank valve slightly to remove any dirt or debris. Check to see if the regulator is in proper working order and free of contaminants. Insert the male end of the regulator into the female end of the tank valve and tighten with an adjustable wrench to a snug fit. Back out the regulator adjusting screw. Stand to the side of the regulator and slowly open the tank valve. Once pressure is observed on the tank gauge open the tank valve completely. Turn the regulator adjusting screw in and set the desired flow rate. Check for leaks by closing the tank valve and observing the tank pressure. In a properly functioning system the tank pressure gauge will remain at pressure. A tank gauge reading that slowly declines indicates a leak in the system. You will have to check the fittings and hoses with leak detection fluid to determine the location of the leak.

Flow Meters Many of the welding shops and training facilities distribute gasses from a central location. When this occurs there will be flow meters to control the flow of gasses. There will be a valve near the meter that turns the gas on. When this lever is parallel with the direction of the pipe the gas will be on. When the lever is perpendicular to the pipe the gas will be off. To set the gas flow rate turn the gas lever the on position. Turn the welding machine and depending on how the machine is configured either press the purge button or turn the wire feed setting to the lowest setting and trigger the torch. NOTE: be careful triggering the torch because the wire will become live and will arc if brought into contact with the work piece. Turn the thumb screw in the front of the flow meter until the ball is at the desired pressure. Release the trigger.