Bought used machine, need tips

[ultimos]

hey guys

i bought a used miller maxstar 200 sd for tig especially
first thing i love it
the machine was store in a shop, not connected for a while. when i use it, it tends to do porosity. i checked everything; gas flow, connections, cleaned base metal, diffuser... now i suspect that there is contaminants inside the machine gaz pass. is there a way to clean this up? what if i shoot some compressed air while gate is open?
any inputs?

[H80N]

hey guys

i bought a used miller maxstar 200 sd for tig especially
first thing i love it
the machine was store in a shop, not connected for a while. when i use it, it tends to do porosity. i checked everything; gas flow, connections, cleaned base metal, diffuser... now i suspect that there is contaminants inside the machine gaz pass. is there a way to clean this up? what if i shoot some compressed air while gate is open?
any inputs?

Not likely to be the Maxstar itself.... you might have a gas or torch problem...

100% Argon..?? Gas flow how many CFH..?? Torch tight..?? no cracks..?? leaks..?? Torch type..?? 17..??

[ultimos]

100% argon, about 15-20cfh and i tried to boost it up to 60-80, still the same. all is well tight in connections. torch is brand new, 17 with valve.

the porosity is mostly at the arc start, then reduce to near nothing.

[H80N]

100% argon, about 15-20cfh and i tried to boost it up to 60-80, still the same. all is well tight in connections. torch is brand new, 17 with valve.

the porosity is mostly at the arc start, then reduce to near nothing.

Pics of porosity..??

Might keep Flow closer to 15CFH...Be aware that too much gas flow is as bad as not enough.... too much will cause turbulence and draw in air

Also might want to up your gas preflow setting ....

See Section 5-11. Adjust Controls (Preflow/Post Flow/DIG/Purge) in your manual

Serial number..??

[H80N]

Don't know your experience level

But these guidelines & tips might be helpful

https://www.millerwelds.com/~/media/...s/gtawbook.pdf

https://www.millerwelds.com/resource...ing-tips-intro



Sometimes a little tweaking of the technique will make all the difference

[ryanjones2150]

Clean your filled metal too. There will be a surprising amount of gunk on the rod right out of the package. <br />
<br />
Change one thing at a time until you figure it out. Start simple...stick out, torch angle, etc...before you go cracking into your machine gas passages to find a problem that is likely to not exist. <br />
<br />
If you're using old nasty metal like I usually am, try welding with 309 stainless instead of er70-S-whatever you're using. That boiling puddle will smooth right out. It's not a crutch, but it will help you out in a pinch when you need to get something done.

[Portable Welder]

Sounds like your pre-flow isn't kicking in soon enough, not likely your problem but a bad regulator will give you a burst of argon and fall off to almost nothing.

Make sure your cup isnt to small, the bigger the better.

[ryanjones2150]

Something I do, a bit wasteful I suppose but maybe it saves me abrasives, before I get the torch close to the work, I purge the line by giving the foot pedal enough of a bump to trigger the post flow. Then I know the gas is flowing well. I also try to get into position before the post flow turns off so I don't get a burst of shielding gas.

[buffumjr]

On any welding, MIG, TIG, stick, torch, clean your metal if you can. Amazing the difference in weld quality and strength. Coatings can really drive you nuts. Don't think you can just burn them off. For those tight corners, use folded sandpaper. Any cleaning is worth it.

15-20 cfh should be plenty.

This may be a little wasteful, but it seems to work. I release the tension on the wire feeder. or just hold the tig torch not near anything, and hold the trigger down for about 10 seconds. Remember, when you are not using your welder, there is just plain air in the system. That 10 seconds allows gas to go from the tank, down three feet of regulator to welder hose, through the welder, through 15'-25' of hose to the weld handle. After that, the system holds shielding gas, so you should be all right.

If it still persists, try a different regulator.

If it still persists, come back and tell us.

[ultimos]

thanks guys for your input. seems like my torch was clogged in by a piece of teflon?! thats the last time i buy rebranded chinesse welding stuff

[H80N]

thanks guys for your input. seems like my torch was clogged in by a piece of teflon?! thats the last time i buy rebranded chinesse welding stuff

Glad you got it sorted out....

9 out of 10 times it is the simple stuff that bites ya...

Tef Tape is a no-no around welding gas connections... guess they missed the memo...

[buffumjr]

Tef Tape is a no-no around welding gas connections... guess they missed the memo...

(GULP!) I just looked at my Oxygen tank, and there is Teflon tape in the K-valve to tank joint! Should I worry?

[Aeronca41]

I've seen that too. So long as the Teflon is kept a couple of threads back from the end of the male fitting it's generally OK. Just Another reason for a healthy release of oxygen by opening/closing the valve before installing the regulator. Plumbers use it all the time with the appropriate caution on connections to gas valves/regulators on furnaces & appliances which could be just as fouled by Teflon as our welding eqpt. HOWEVER, in my mind that is not a reason to use it on welding eqpt. I just don't do it. Another application of the adage "Just because you can doesn't mean you should".

[H80N]

Maybe this will help to clarify what I'm trying to convey

You can use tape ONLY when the threads do the sealing. like on NPT fittings

If the threads push two mating surfaces together, you do NOT use tape like on the CGA fittings common in welding gas connections

CGA Fitting Chart

http://www.concoa.com/cgachart.html

Compressed Gas Fittings - CGA Fittings Brass
Air Liquide offers Compressed Gas Association (CGA) fittings for use with various gases. The Compressed Gas Association is the group that established standards in the gas industry for fittings which are used to attach to gas cylinders. For nearly a century, the Compressed Gas Association has been dedicated to the development and promotion of safety standards and safe practices in the industrial gas industry. CGA fitting standards are developed through the combined efforts of more than 200 member companies worldwide. Gas handling equipment that connects to your gas cylinder must have a compatible CGA fitting to mate with the gas cylinder valve outlet. For safety, it is important that you do not force connections. Moreover, never use any pipe dope of or PTFE tape with CGA fittings, when mating to the cylinder valve. In general, these connections are designed for metal to metal sealing. Scott™ CGA fittings come in brass or chrome, in a variety of pressures and sizes. A sealing washer is provided on those fittings that do not have a metal to metal set. Adapters from one CGA fitting to another should not be used to connect equipment to a high pressure cylinder.

.
Putting Tef Tape in places not required only increases the chances of loose teflon shreds creating clogs----

http://www.scottecatalog.com/equipsp...2568b20058a744

[Jerry U]

hey guys

i bought a used miller maxstar 200 sd for tig especially
first thing i love it
the machine was store in a shop, not connected for a while. when i use it, it tends to do porosity. i checked everything; gas flow, connections, cleaned base metal, diffuser... now i suspect that there is contaminants inside the machine gaz pass. is there a way to clean this up? what if i shoot some compressed air while gate is open?
any inputs?

Some excellent suggestions posted, I'll just reinforce some i have seen: 1) never use Teflon tape or pipe sealant of any kind on CGA fittings! They are metal to metal seats and the nuts are just to press the metal seats together they are NOT pipe threads, 2) have seen TIG rod with drawing and straightening machine oil lub left on. Use alcohol and clean it, should be nothing left on a paper towel. Once you start welding the radiant heat from the arc can burn some residuals off but at the start it's worse. 3) It takes ~3 seconds to fully purge the torch gas hose, torch and weld start area. This is especially important when welding aluminum. Since the porosity is more at the start, I'd try a longer preflow time or just hold the torch above the work for 3 seconds, 4) have found gas leaks inside a welder at the gas connections, solenoid etc.
Just some thoughts, will be interested in what you find.