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Welding SteelChoosing a Welder for Your ShopIf your looking to buy a welder for your shop, do not ask a welder! Ask an average guy that has tried both and consider your application.
Choosing the welder is all about what and where you will be welding. We are building a 74 foot boat from 1/4 inch steel for the hull and 1/4" aluminum for the pilot house. We currently have a Hobart 210 with a Spoolmate 185 gun for aluminum. It will be pressing the limits to weld 1/4 aluminum so if we can get a system that will do aluminum too then all the better. We could get a better spool gun but another solution is a wire feeder with a push-pull gun. Push-pull guns have drive motors and feed wheels in the gun, just like a spool gun, but instead of a 1 pound spool of wire on the gun they help pull wire that is being pushed from the wire feeder. On a Boat and In the WaterFor us the welder will go on the boat as part of the shop, so we want something that is not extremely heavy, power efficient and will run of a single phase 220 volt AC generator. The more expensive Inverter type welders fit the bill for light weight and power efficient and they also DC which is nice because underwater welding in in our future too. Inverters also output constant voltage or CV so they can power most any wire feeder. Getting a welder with circuit board that is potted or can be potted to protect it from salt water damage is a must. If the board is not potted, it is often no difficult to add heat sinks and a coating of RTV silicone to kept it healthy. Duty CycleDuty cycle correlates to how long you can weld in a 10 minute interval before the welder or gun get too hot. A 60% duty cycle at 200 amps, means you can weld for 6 minutes at 200 amps and then you need to let it cool down for the next 4 minutes. To weld 1/4 steel requires 140 amps, DC, running .045 flux core wire. And we want to do that at 100% duty cycle. Not that we will actually run at 100% duty cycle but because the engineers exaggerate, the marketing department exaggerates more, and neither work outside in the summer in Oklahoma. PortabilityPutting the hull plate together requires a lot of moving around and while stick is a bit slower welding and more difficult than wire, it is very portable around the building site. The plate stitch welds are also relatively short and most will be done with the plates laying flat or almost flat with makes stick welding easier. Once the hull plates are stitched together then finish welding can be done with a faster and easier to use wire feed welder, but mobility around a 70 foot boat is still necessary so the wire welder will be a wire feeder or suitcase wire welder that is powered off the stick welder box. We will set the Inverter power supply out of the way and carry around the 80 pound wire feeder on the end of a 100 foot long power cord that runs back to the Inverter. From the wire feeder box to the gun is another 15 to 50 foot set of cables including; power, the welding wire, control wires for telling the wire feeder when to start pushing and how fast, a hose for shielding gas if required, and possibly a couple of water hoses if the gun is water cooled. There are a number of portable suitcase type wire feeders: Advanced Process Welders
We almost purchased Miller 350MP inverter power supply with
"pulse" ability along with an XR wire feeder. The pulse option is
like a Pulse Width Modulator for a welder. Instead of a
constant supply of power to the arc, the power is chopped up into
very fast on/off pulses. The welder has different programs
that will control the speed and length of the pulses according to
what you are welding and the feed speed you have selected for the
wire. The advantages are less splatter and more wire into the
weld with less heat so you get less distortion. The
disadvantages are there are more control wires between the boxes and
there are a lot more very expensive electronics to fail. This used
system sold for $2700 (2008) which is a good price. The other
detractor for us was this unit has the 15 foot cables between the XR
wire feeder and the gun. The system we ended up buying was
less power, no pulse, but has a 25 ft of cable to the gun. What We PurchasedOur power source for arc welding and powering the wire feeder is
a Lincoln Invertec V300-Pro, inverter type welder for $1500 with a 30
day warranty. Not a great price, but fair, and I was paying
for good advice too. The wire feeder is a Cobramatic with a
water cooled push-pull Python gun that has 25 feet of cable for
$1300. Then add four, 50 foot, 2/0 welding cables with
connectors, a ground clamp and electrode holder for $800.
Having 4 separate 50 foot cables will give us the ability to add
cable where it is needed, and while 2/0 is overkill for the amperage
we will be using, it will be right considering that the summer heat
will degrade it's load ability. All together the package was
$3778.60 with shipping. What We Got DeliveredUnfortunately was not what we paid for. This is one of those, I should have bought it on eBay and trusted the guy in California. Instead I trusted a local guy on CraigsList. When I first talk to him, he is full of promises about making sure your equipment is checked out and comes with a 30 day warrantee. We agreed on the above equipment, paid him in full, and then waited 2 months for him to finally get all of the equipment together. He didn't hang around after dropping off the equipment and I can understand why. What he actually delivered was 1/0 cable, not 2/0, a Cobramatic feeder that was not water cooled and had two broken toggle switches soldered onto the control board and tape on the Python gun that hid damage. The welder had a crushed case and another broken toggle switch. Almost predictably he would not refund our money, and he would not compensate us for the damage or wrong parts. He did offer to take the equipment back and give us a credit! What a guy! So if you live in the Tulsa, or SandSprings Oklahoma area, be careful about fat, greasy bastards selling promises about welders.
Rebuilding a Cobramatic Water Cooled Push-Pull feeder.Three cheers for the support people at Cobra welders; www.mkprod.com, for finding the original documentation for this welder. Documentation: Cobramatic Manual, Gun Consumables (1) Carefully heat the case around the gun and it can be bent back into shape. Then coat it with epoxy to patch up the holes and fill in the gaps. Heat form an acrylic view port to cover the rollers, warp it up with electric tape and it's looking good on the outside. Inside required some solder and epoxy to add a new water connection port. Originally one water line was inside the power cable which is a cleaver idea for keeping the power cable cool. Unfortunately that power cable had been replace with a standard cable, so I cut and soldered on copper tube to give the head two hose connections. The orange hose is 1/4 inch air line that will now deliver and return the coolant. (2) The feeder got two new switches soldered onto the control board and a third switch added so I can power the coolant pump on and off. You can also wire the pump into a 110 AC circuit that is live while the gun is running, but I wanted to give it more time to cool after the gun is switched off. (3) The two water coolant lines now pass through the box and to an aluminum coolant tank. There is a small garden fountain pump in the bottom of the tank. An acrylic cover let you see the coolant level and seal the tank. A plug is treaded into the top to allow for coolant to be added easily. (4) Using vinyl and Velcro salvaged from our school bus, Kay
sewed up a really nice cable cover. See:
Canvas Work for more. Hot Slag Warning
You have to balance the amount of protective clothing against the chance of passing out on a hot day. My brother Pat dropped in to celebrate July 4th. He picked up the welder and put together some beams to support our shade over the build site and demonstrated how quickly you can pick up on wire welding. He also demonstrated what happens if a chunk of hot slag gets inside your shoe. Most of the time you just get a little weld splatter that stings and quickly cools off. The problem is that can't tell the difference between a little weld splatter and a big chunk of molten slag until it is too late. His solution was to stand a piece of cardboard on the ground and lean it up against his legs to deflect the incendiary devices. Boot work too, but who wants to wear boots in July in Oklahoma. I prefer sandals because the slag is easily shaken off. : ) Lincoln Invertec V300 TipsCV FCAW This setting has been optimized for Innershield and
Outershield flux-cored. ARC or Stick Welding - Stick SelectionWe don't plan on doing much stick welding while building the
boat. It will only be used when a few short welds are needed
and it's not worth moving the wire feeder. We'll have 6011 rod
for welding in the flat down positions, 6013 for general
all-position welding and maybe some 7014 for thin materials and poor
fit materials. Wire or MIG Welding - Wire SelectionLets start with the fact that a Wire Feed Welding machine can be
used with 3 kinds of wire.
The most common type used on small to medium sized machines indoors
is solid steel wire, usually ER70S-6.
This wire requires a gas shield, which can be pure CO2, or a
Argon/CO2 mix.
Solid wire means you are MIG welding.
MIG rules the light gauge fabrication world.
Light gauge is steel under 1/4" thick. The wires that use a gas shield can be used with pure CO2 or
Argon/CO2 mixes.
Pure CO2 is very hot and very cheap, but it does make a lot of
spatter, which makes for a lot of clean up afterwards
Argon added to CO2 makes the arc smoother and cleaner. Innershield - Lincoln's brand name for flux core wire. It
needs no shielding gas in moderate wind. Flux-Core, Self-Sheilding
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Resources
http://groups.yahoo.com/group/welding_group
