Troubles with Lincoln Magnum Pro 100SG

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Troubles with Lincoln Magnum Pro 100SG

Postby eurof2 » Wed Jul 26, 2017 9:40 am

I have a Lincoln Magnum PRO 100SG spoolgun I am using to build a Scrambler and it seems like it is overheating. After 10-12 tack welds the wire starts to slow down and eventually stop as it gets stuck in the tip. It is not getting welded to the tip, just stuck on the inside. If I take the tip off and pull the wire out, I can ream the inside with a small drill bit and it works fine for a while again.

I have not done any long welds with this yet and would like to resolve this before I start the serious welding on this boat. So far it has all been short welds.

The tip is the one that came with the welder intended for 0.035 wire and I am using 0.035 5356 wire. I have even tried drilling out the inside to as large as 0.055 and at that point it starts to have trouble maintaining an arc as I think the hole is too big and losing connection with the wire. Even that large it will eventually get the wire stuck again.

This spool gun is setup to have the tip flush with the end of the sheilding nozzle and at first I tried unscrewing the nozzle some to get more stickout and I have also cut the wire tip short as well to increase stickout and have the nozzle not so loose. This has helped a little, but not nearly as much as I expected.

Is there anything else I am missing that might help, or am I expecting too much out of this spoolgun?

Kevin Morin
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Re: Troubles with Lincoln Magnum Pro 100SG

Postby Kevin Morin » Wed Jul 26, 2017 11:34 am

I will take a shot at some possible answers to your MIG torch wire feed issues but not regarding that exact gun as I've not seen or used that model. Most of my experience is with push pull MIG feeders in aluminum welding, so the remarks are mostly generic regarding wire in contact tips and performance.

First, all MIG power supplies initiate a wire welding arc at a high voltage compared to welding voltage. Typically a power supply will initiate the weld process with a second or fraction of a second long voltage of from 20 to 35 V up to 70 to 90Volts depending on the individual power supply and its tested requirements to initiate an arc using wire as both filler and electrode (MIG process).

Next, ONE Setting for OCV (open circuit voltage) may not be as useful for all applications? Meaning that some power supplies allow the OCV to be adjusted up or down compared to some factory setting. I am not familiar enough with your model power supply to offer advice on this aspect, but I do feel confident your manual may provide the adjustments - if you find the OCV is variable (#1) and (#2) if you decide to try to make adjustments?

#3rd point- tacking initiates the arc each time the trigger is pulled at OCV which at (say for example) 70VDC is probably 3 or 4 X higher than the 'background' welding voltage. I'd expect that 0.035" (.89mm) wire to require 22-25 volts depending on your A) speed of wire feed (which is related to) B) travel speed which is dependent on skill and joint type and prep. All these are related rates- but the point is the OCV is much higher than background or 'regular' welding voltage.

AS the highest voltage which will make the longest arc off the contact tip to the wire (inside) is when you're tacking- so that is when the power (potential) in the copper contact tip will be able to jump/gap/span the largest distance INSIDE the tip barrel/bore to the wire. This is why you may want to adjust - if possible with your power supply- the OCV down?

If you've drilled the tips to clean them, and they've become too large ID or used a tip that is too large a bore for the welding ranges you're using (? speculation on my part) THEN the higher OCV may be arcing to the wire instead of the wire sliding along the bore and conducting the welding power off that sliding contact?

Next are the bore of the tip issues. The bore of the tip has to: A) allow for heat expansion with the tip heats up during a seam weld/longer duration weld. B) the tip has to 'contact' the wire sides in a solid electrical connection to conduct the welding power to the wire as before the wire (electrode and filler metal) exit the tip. C) if the tip's bore is too large for the wire- the necessary electrical transfer will not happen instead the wire will arc to the sides (spot weld) to the inside of the tip. D) Higher voltage/amperage (wattage) ranges require a larger clearance inside the tip. 0.055" for 0.035" is pretty wide tolerance? I'd expect to see an approx. 0.044"-0.047" bore tip for tacking 0.035" wire?

If the wire feed is slowed or stopped while welding it is possible for the arc to 'follow' the wire end as it slows and fuse the wire to the outer end of the contact tip - melting the two metals together. I'd call this 'burn back' and conversationally separate this event from arcing in the bore- wire 'sticking' inside the tip.

"Micro Arcing" is the term I've heard from several technical support people with Lincoln, and MK Products (another manufacturer of MIG systems) so I will use that term here. As I understand - if the wire to tip bore is beyond a small gap that micro arcing will create a series of pits or arc craters inside the contact tip bore - and that will eventually reduce the size of the bore and begin to add up to more resistance than the drive motor pinch rollers can force wire through.

You describe something of that nature in your post- as I read it? Therefore, you've had to re-bore your contact tips- I'd suggest that instead of using a tip drill you consider an OA torch tip reamer set of wire scrapers designed to clean tips. This would allow you to scrape clean the bore but not to resize it -oversize it.

These types of feeder problems used to be solved by a long contact tip, several inches long with a distinct bend built in- that ensured contact with the wire and the bore - but that is now longer common.

On item I've also seen is micro arcing of the drive rolls themselves!! That is a small groove of pits around the drive rolls - and this shows the welding current is being imparted to the wire all the way back inside the torch at the wire feed motor rollers. That condition also creates a feed problem- its easy to see too. Just examine your drive rolls carefully to see if there is a ring of pits around them? I'm not discussing the very distinctive and accurately machined V groove (if one exists?) - this pitting is distinctive as the edges are irregular.

Some mfg.'s offer a set of small insulation bushings of plastic to fit over the motor drive spindle- and an 'isolation drive rolls' which has a larger thread bore - so this kit creates an electrical isolation of the drive motor roll from offering a path to the 'work' electrical lead- eliminating the pitting and wire drag.

(also) I suggest you explore the threads of your contact tip and discover if you can use a slightly different type of tip? Often the different manufacturers make the threads of different parts of their guns unique so they are your only source of consumable parts? It may be the case with your spool gun?

In any event a company, MK Products, makes a contact tip for several of their MIG torches that has a ceramic pellet inside the tip- spring loaded to one side- that insures the wire is held against the tip's bore but not so tightly as to increase drive friction. ... partspring this link is to a page with information on a spring retained, ceramic pellet loaded contact tip- there may be some way to adapt to these threads (??) but this is one product that does eliminate micro arcing in the contact tip.

As mentioned above- reducing the open circuit voltage may help as well, and finally using a tip scraper/reamer instead of a tip drill may allow the pitting to be scoured off the bore's walls instead of resizing the tips' clearance?

Not sure if you can adjust the wire drive rolls' tension? If you can then the test I've always heard to be correct is to turn off the gas, and hold a gloved hand infront of the wire at the gas cup- 1-2" away. Pull the trigger and if the tension is correct- the wire will coil into your palm. Keeping backing the tension OFF, until the feed motor rolls spin on the wire- then add 1/4 turn on the tension spring screw and that is where the tension is optimized- not too much and not too little.

If the wire drive roll's compression on the wire is too little that condition means that a small added resistance in the tip- like micro arcing pits' crater edges- can cause the feed to slow as the drive rolls begin to slip.

IF the gun has a plastic liner in the goose neck (?) this too can contribute to wire feed resistance. If you have heated the tip of a plastic wire guide liner too hot and the end near the gas cup has melted to fill the forward end of the wire conduit/gooseneck- this condition can create another added resistance to wire feed.

At least a few things to consider in your trouble shooting and tuning of your MIG spool gun.

Kevin Morin
Kenai, AK
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Re: Troubles with Lincoln Magnum Pro 100SG

Postby chugalug » Wed Jul 26, 2017 12:41 pm

years ago,when I was operating Miller robot at work,I would have problems with tips burning off too quickly so remedied by grinding off 1/4 inch of tip off.gotta make sure to grind a chunk of wire inside tip as well.otherwise the tip would melt hole closed.seemed to help.shortened burnback as well since i couldn't change programming.(not like hand welders can)Kevin-- whats the duty cycle for those spoolguns???
Working on regular-sized Bo-Jest

"If it's not crooked,It's not mine

Kevin Morin
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Re: Troubles with Lincoln Magnum Pro 100SG

Postby Kevin Morin » Wed Jul 26, 2017 2:12 pm

eurof2, Chugalug, I agree that contact tip to gas cup is a variable in the related rates of MIG welding as well.

The contact tip to 'work' distance- all related to the gas cup to work- which does affect gas coverage versus dispersal or dilution of cover gas is an important consideration in MIG. One that can be solved in different ways- unfortunately - which means there is not one single 'answer' for all circumstances; On/Off switches are universal they're either ON or OFF and do not work like dimmer or attenuating potentiometer.

But stick out or total wire to work distance is variable even with the same welder welding different joints - mainly vision and welding bodily position vary the total stick out.

A portion of the stick out is the arc length since the last fraction of an inch of the total stick out is arc. If the wire speed (for a GIVEN wattage = V x A) is relatively slow- or just fast enough to keep an arc fed with wire- then the arc length will be a bigger percent of stick out - longer arc- than if the wire feed -speed is higher for the same wattage. So arc length can be adjusted not only by gas cup work distance but by wire feed speed as you weld.

However, in tacking, the OCV timer- an internal circuit that turns off the higher OCV to revert to the weld voltage/current settings- may not time out? so the entire tack may be done at OVC voltage and if the wire is not feeding well- burn back or tip fusion can result. Short welds would almost assuredly revert to the 'welding' settings from OCV settings.

Let's complicate things a bit- the "stick out"- Arc Length PLUS the additional distance along the filler wire to the Contact Tip; is the total R or resistance in the equation E = IR. Where E is Voltage and I is current flowing while R is resistance.

It is important to realize that MIG power supplies are called Constant Voltage power supplies because these PS.'s have circuits to monitor the R and vary the I to keep E as flat as possible. So in most cases we're getting a circuit R by wire feed speed combined with our hands' holding a gas cup distance off the work.

How does that impact our welding using a CV PS? If you move your torch tip/gas cup up and down you're varying the R/resistance of the equation and that means the CV PS's I/current will be varied in order to try to keep the E/voltage; flat.

Movements of the welding contact tip away from or down to the work changes the resistance and so does the wire feed speed for a given wattage.

One method of getting better gas coverage resulting in a 'hotter' and cleaner weld is to put the gas cup and contact tip closer to the parent metal, but then the arc length is so close to the contact tip- very small variations in EITHER wire feed speed (like drag in the tip or slip at the drive rolls) or movement by the welder can end up fusing the wire to the contact tip from a surge in either voltage or current due to the conditions at the weld.

So, I too cut the contact tip back so it is behind the leading edge of the gas cup- this allows a bit more tolerance in the stick out dimension while giving higher gas coverage to any combination of settings of wire feed speed, gas flow, weld wattage and movement.

However, the disadvantage is that one usually has to crane their neck side ways to see under the gas cup and keep the entire puddle in view.

And to make things a little more of a head ache yet- if you're whipping the puddle or make small 'e's or 'c's' in your weld patterning the bead??? New digital controlled, inverter type power supplies are actually 'fighting' you in some ways- those very high speed reaction circuits are making wild adjustments to the weld if you're making pattern movements (in most modes) because the PS is designed to keep V constant!!

I don't know the duty cycle recommended for this small spool gun but if the barrel heats up doing tacks and short stitches- the Duty Cycle is not a high percentage. Most manufacturers tend to rate their equipment higher service/duty cycles than it turns out you'd want to hold on to them as they heat up sooner than is claimed in the sales literature.

Kevin Morin
Kenai, AK
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Re: Troubles with Lincoln Magnum Pro 100SG

Postby eurof2 » Tue Aug 15, 2017 12:32 pm

I gave up on working with the spool gun for some of the watertight welds I was working on and just TIG'd them instead, so I have not played with the spool gun yet much since I last posted. I did end up cutting off about 1/4" of the tip as suggested and I think it helped. Hard to say for sure as I havent welded with it too much yet. I still ended up with the filler wire getting stuck in the tip, but it seems to have taken longer.

I was wondering for a while if it is my power source as it is just a lowly SP130T 230V MIG machine. Supposedly it is rated the same as the 180, but just as long of duty cycle. I thought maybe it wasnt creating enough heat, but I am very consistently getting enough penetration that I either melt through the backside or at the very least I can see where the welds are on the backside. I am sure some of that is technique, but I think I am getting enough heat in there regardless.

I am sure I am pushing this whole setup to it's limit regardless, so I will probably stick with TIG on the watertight stuff and longer welds as I have a Syncrowave250 with watercooler that seems to handle long weld times just fine.

I will try to update this as I do more welding with the spoolgun and figure out the details.

Chief Ed
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Re: Troubles with Lincoln Magnum Pro 100SG

Postby Chief Ed » Sun Aug 27, 2017 4:04 am

Hi, I'm new to welding, but! I have the same spool gun and a Lin. Easy 180 mig. I'm seeing good
heat penetration and smooth performance. I do get jam when in tight spots. I just thought it was me
moving to slow.
I'm building the "Goliath" in AL. So far I've got the frames mounted and drilled for 3/4" bar.
I've asked my self several times " am I nut's?". This is a lot more than the "Gill 12" tug I made a few year's ago.
Than can be found on "Duck Works" Mag. web site. Regards Ed Davis DSC USN Ret.

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