MIG Welding & Metal Fabrication 101
What Can the MIG Welder Do?
Join two pieces of steel together.
Safety Considerations
Keep a fire extinguisher beside you
The biggest dangers come from our complacency and not being totally aware of what we are doing. Don't take shortcuts that compromise safety.
Point out the following safety equipment:
Fire extinguisher
At each doorway
Fire exits
First aid kits located at front desk
Metal Shop Safety Guidelines
Wear appropriate clothing:
Clothes should be made out of natural fibers such as cotton or wool. Do not wear synthetics as they melt to the skin
Full length pants which fit over your boots – to stop hot metal/sparks from getting into your footwear
Wear a long sleeved shirt and pants without cuffs and have your pant legs cover your shoes so sparks can't drop into your footwear
Wear leather boots, CSA approved boots are best, no sandals or open footwear (green shield)
Wear leather gloves (demonstrate different types of gloves)
Long hair, drawstrings and shirt tails/sleeves tucked in/ tied back,
Safety glasses at all times in shop, hearing protection recommended
Avoid wearing jewelry
Main causes of injury are:
Sharp metal edges
Sparks
Heat and flame
Arc Flash
Electric Shock
Welding Gases
Fumes
Metal safety:
Hold it like it's glass (sharp edges)
May be very hot, always check before you grab or wear gloves
Electricity:
Electric shock can occur when arc welding. This usually happens when the current passes from the electrode through the welder to the piece being welded and through contact with poorly maintained electrical cables
Don't set handle on table - hang from cart
Primary electric shock is much more hazardous because the voltage is much higher than the secondary or welding voltage.
AC is 2 to 3 times more dangerous than DC welding.
Inspect your equipment to make sure it has been properly maintained.
Wear proper PPE (personal protective equipment) to insulate yourself from electrical hazards, dry gloves and rubber soled boots.
NEVER touch ground & tip at the same time (ground is kept up at the front desk)
MIG (Metal Inert Gases) = cable is hooked up to (+) port on box
DCEP (Direct Current Electrode Positive) (electrode = welding gun)
Don't weld in damp conditions
Gas:
Never move without cap!
Fire Hazards:
No flammable items/substances in a welding area, e.g. no wood dust or stains, etc. (wood welding jigs are ok)
UV light:
Don't wear white (reflects under mask = neck burn)
Cover all skin (to prevent sunburns)
Always use red UV shield to protect others
Warn others before you start, e.g. "Arc up!"
Masks:
Auto-tint = when it sparks, vision darkens
Blocks UV light
"DIN" = can adjust auto-tint setting
9 = brightest
6 = plasma cutting
How to adjust knobs to head
Air extraction:
Can wear a mask, but welding mask may not fit over it
Open door, turn on overhead extraction
Aluminum is worst, steel not as bad
Rust & paint on metal pose dangers as fumes
Wear a mask if you grind off (dust)
Welding Fumes
When welding the melting metal oxidizes and produce gases such as carbon monoxide, carbon dioxide, oxides of nitrogen and ozone. We also use gases such as argon and carbon dioxide in the welding process to shield the weld and prevent oxidization.
Metals contain many alloys that can release contaminants into the atmosphere during the welding process.
A coating on metal which could emit harmful contaminants (such as lead, chromium, organic materials, or toxic combustion products) must be removed from the base metal, whenever practicable, before welding or cutting begins
Confined Spaces
Always test for oxygen levels before entering a confined space. Any reading lower than 19.5% (at sea level is said to be deficient). Use fans to ventilate the space or use a welding helmet with an air line bringing in an outside source of fresh air.
NOTE: Inert gases like argon are heavy and will displace oxygen in a confined space. If you see someone unconscious in a confined space DO NOT ENTER the space unless you a wearing a self contained breathing apparatus. In January 2003 four workers at Westminster Marine Services died. Three of them were would be rescuers.
Welding Fees
Welding is $10/hour to cover gas and welding wire.
Drop-ins need to pay the $45/day drop-in rate plus the hourly rate for the gas / wire.
Material Set-up
For cleaner welds, material needs to be prepped prior to welding. This can be done by using some of the basic tools in the shop.
Angle Grinder
What it’s used for:
Cleaning/finishing/removing/cutting material
There are different disks/wheels for different purposes and materials
Zip discs are for cutting
Grinding discs are for grinding
Wire wheel for removing paint and rust
How to set it up:
How to properly install each disc
Correct position of the nut on zip vs. grinding discs
Handle location
The speed is variable. The harder you squeeze the trigger, the faster it goes.
When cutting, first do a shallow pass, then a deeper cut.
Capacity:
Max disc size: 4.5”
Max material thickness: 1” (note, this is borderline. Cutting something this thick could be dangerous)
Tolerance: Accurate up to .1”
Parts:
Wrench, guard, nut, discs, safety switch, lock for changing discs
Important safety guidelines :
Clamp material to work table
Be aware of where the sparks are going
Do not remove guard
Zip Disks can chip off
Be careful that you’re not in the plane of the disc as it can go flying
Bench Grinders
What it’s used for:
Cleaning/finishing/removing material
There are different disks/wheels for different purposes and materials
Capacities: 2” wide material
Tolerances: Accurate up to .1”
Important safety guidelines:
Pinch points
Don't cross-contaminate - Steel on the steel grinder and Aluminum on the aluminum grinder
Horizontal Bandsaw
What it’s used for:
Cutting stock down to size
Parts:
Blade, guides, vise, coolant, hydraulic gauge with dial (adjusts feed rate) and lock-off valve (will hold saw/stop from moving), feed rate (2 is a good feed rate; looks like it's barely moving)
Important safety guidelines:
Keep hands far from blade!
Clamp the narrowest side of your material
Adjust throat. It can get in the way of the cut if not adjusted for larger material
Let saw stop before grabbing anything too close. Blade still spins when saw is turned off - let it stop completely before putting hands anywhere near
Careful not to let it flip over when saw is in top position
Pay attention to dial before you flip lock-off valve up (make sure saw won't fall quickly!)
Make sure piece is supported if large
Feed rate adjustment (~2 is good, aluminum especially needs slower bc it melts/sticks to blade)
Coolant (should be just dripping off blade, not pouring)
Keep switch on all the time - will automatically start when saw starts
Look at flow tube for bubbles/foam - add a few L of water if low (staff only))
Watch for coolant flowing out back - put bin under to catch any drips
Machine Setup
MIG (Metal Inert Gas) vs TIG (Tungsten Inert Gas)
(define, what they're used for, etc)
TIG stands for Tungsten Inert Gas and is technically called Gas Tungsten Arc Welding or GTAW. The process uses a non-consumable tungsten electrode that delivers the current to the welding arc. The tungsten and weld puddle are protected and cooled with an inert gas, typically argon.
Metal inert gas (MIG) welding or metal active gas (MAG) welding, is a welding process in which an electric arc forms between a consumable wire electrode and the workpiece metal(s), which heats the workpiece metal(s), causing them to melt and join.
Tank:
Don't open too fast
Watch gauges: flow (cfh) & pressure (psi)
35 CFH
Machine:
Switch on back
Select settings:
Dial @ top
Guide inside box door - shows settings for different types of materials
Then use +/- to select material thickness
Spool inside machine (for steel/MIG)
We have a handheld spool gun for aluminum
Black knob = pressure; too much friction, wire won't push through
Pinch with fingers, guide roller under black knob should spin and spool still moves
Gun itself:
Nozzle comes off, spatter can be inside (which affects shielding gas) - can clean with MIG pliers
Contact tip (inside) - specific to wire size: 030 & 035 = standard wire sizes
Cable:
Both gun & gas run through
If it loops, do not pull on them - will kink wire
Expensive to replace
Treat carefully - don't step on it
Table setup:
Use magnetic squares to get 90-deg welds, etc.
Types of Welds
Welding Technique
Cleaner metal = better weld
Grinding taught in Metalshop 101
No sheet metal on bench grinder
Wire wheel/flap disc/grinding discs - clamp down!
MIG = adding material, needs somewhere to go
Grind 45-deg corner on each piece to make a valley
Start with wire out about 1/2"
Hold gun at 45-deg to the weld
Do a "tack weld” first
on both sides
so weld doesn't pull over
add one bead where you plan to end actual weld as well - cleaner ending
Then "stitch" back and forth between surfaces as you push/pull the puddle
Keep puddle the same size and moving
too slow = puddle may melt thru
too fast = only sits on top, like hot glue
want a consistent sizzling bacon sound - no popping or sputtering
Wire speed
this machine keeps it ok
assumes 2 metals are the same
whereas if two different gauge metals, wire could need adjusting
Close tank
Press trigger so gauges go back to zero
Turn flow handle so it's loose again (spins)
Turn off machine (switch at back of box)