LT200 pre- and post-flow?

[smcewan]

Hi. I am slowly saving up for a welder. I've done some reading and watched some training videos. They've used Miller and Lincoln Electric models in their demonstrations, and there is mention that post-flow is important to keep the weld and tungsten from getting contaminated at the end of a weld, and depending on what is being done, sometimes pre-flow is important.

How does the LT200 implement pre- and post-flow?

Thanks.

Sean

PS I did try to sign up on the new forum, but for some reason I didn't get an e-mail after trying to sign up.

[bhardy501]

There should be dial controls that control both pre and post flows. On the 160P there is also a switch 2T and 4T that controls post flow and down slope on the arc.

[smcewan]

Well, lookinag the the picture of the 160P, it looks like there's about 9 knobs, and maybe some switches.

The LT200, 1 knob, 1 switch, for amperage and TIG or MMA.

The picture of the torch appears to have a finger control on it. That might be an answer to the question.

[bhardy501]

I was looking at the pic of the 200 and it doesnt have a selection to adjust pre and post flow. It looked pretty basic. The switch in the torch is what starts the high frequency to weld. It is a DC only machine from the looks of it so you cant weld aluminum with it. It may have a pre set post flow but I doubt it has any pre flow other than initial start up when the trigger is mashed. Simon may be able to give you more info.

[smcewan]

Yeah, I'm ok with it being DC. I'm restoring a 67 Cutlass, so I will only be welding steel.

And yes, hopefully Simon will shoot me an answer tomorrow. I'm pretty sure he knows his products quite well.

[bhardy501]

If I were just going to be doing body work I would use a MIG instead of TIG. A lot of areas, like floor pans can be a pain in the a## to try and get into with both hands to weld up. With a MIG gun you dont have to worry about trying to use filler metal. Most body shops rely on MIG.

[smcewan]

I've looked over TIG and MIG options. I am on a limited budget. I started with a Harbor Freight cheapy flux-core only MIG welder, with 2 heat settings, 90 AMP. That was only about $100, so that wasn't a real expensive lesson. I did fix something on my grill with it!

I learned 3 things from that:
1. Flux core MIG generates a lot of smoke
2. 2 heat settings doesn't provide much flexibility
3. 90 Amps isn't enough to repair the frame
4. Welding body panels probably wouldn't go well

Looking around, I've seen a basic TIG for about $300, and then discovered the LT200 that goes for $400 (plus shipping). The TIG gives the most flexible heat control in this price range.

For $400 with Longevity, I can get the heat control, 200 Amps that should be enough capacity for my needs, a 3 year warranty, and support. I think if I went down the MIG path I'd have to spend more.

And if I get good at it, should get some good looking welds that will need less cleanup than MIG. Yes, the TIG process does call for 2 hands, and there's times 1 free hand would be good for other stuff. Maybe I'll put things together with sheet metal screws, or may I'll tack in with the flux core MIG I already have. Or maybe I get a helper. It is a car restoration, so I don't have any real deadlines to meet.

I've already bought the tank, filled it with Argon, some gloves, filler rod, and a regulator, so I'm already a few $$$ into the TIG path. The plan was to have enough $$$ to get those things and the TIG welder, but the plan fell apart, so I've had more time to read up on the free info out on the Internet, and renting a DVD on TIG welding.

[LONGEVITY]

The WeldMate LT-200 does not have a pre or post flow option. Our WeldMate LW-200ACDC does have that option.

Sorry

[smcewan]

Ok, doesn't have a pre- or post-flow option.

So, I guess that brings another question to mind: What starts the gas flow? When the welder is turned on? When the arc starts?

Perhaps the gas flows when the welder is turned on, so it's always flowing. This could "sort of" provide pre- and post-flow, but will end up comsuming more gas unless the person welding does a lot of turning off of the welder.

Or, am I asking about something that isn't a big deal for welding steel? Does the LT200 work well for welding, or does the gas turn off too early at the end of a weld, potentially contaminating the weld and tungsten?

[bhardy501]

I dont think it is that big a deal welding steel. Your gas will start flowing when the trigger is mashed or the pedal (if so equiped) is mashed. Your high frequency will start and it will take a second for your arc to establish. The whole time your gas is flowing until the switch or pedal is released. As far as stopping the weld you wont have any problem from ending the weld. You can TIG off a "dry rig" on a standard DC Stick welder with out HF The torch has a round knob to turn on and off the gas. You turn it on and strike an arc or "scratch start" it. For steel you dont need a dedicated TIG machine. I have both a TIg machine the 160P and a dry rig for my Lincoln Ranger 10,000 gas powered portable machine. You can also weld Stainless Steel with the dry rig. I have seen Aluminum done with AC on a dry rig, but you definitly need to know what you are doing and I wouldnt reccomend it. The key points you need to remember with the TIG is you need a very good fit with very little to no gap for automotive application on thin material and it has got to be very very clean. If it nice and shinny then you need to clean and grind it until it is. Any rust or corrosion, paint, oil or anything will contaminate your weld and leave it looking like crap and weak. Thats another reason its not a very good choice for automotive type work. To many things that can contaminate the weld. Check out ebay. You can get a good deal on a MIG machine, 120 -140 amp, for a couple of hundred bucks up to 4-5 hundred bucks. A good flux cored MIG machine can also be used in windy areas and you dont have to worry about your sheilding gas getting blown away. Thats another thing about the TIG if you have much wind blowing across the weld then your sheilding gas is blown away and the weld oxidizes. I dont want to mess Simon up on a sell, Ijust think you will be very dissapointed in the TIG machine for your application.