Welder Question

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suffolkpete
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Welder Question

#1 Post by suffolkpete » Tue Oct 31, 2017 8:06 pm

I have a SIP Migmate 130 welder, I actually won it in a Practical Classics competition some years ago. The problem is that when I strike the arc, the wire feed motor slows down or stops, extinguishing the arc. The motor then speeds up, the arc restarts and the cycle is repeated, resulting in a weld that is a series of blobs. Any idea what could be the cause? The tip and the wire are new.
1974 Rover 2200 SC
1982 Matra Murena 1.6

rich.
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Re: Welder Question

#2 Post by rich. » Thu Nov 02, 2017 6:26 am

have you changed the liner tube recently?

suffolkpete
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Joined: Sun Jan 23, 2011 11:54 am

Re: Welder Question

#3 Post by suffolkpete » Thu Nov 02, 2017 8:28 am

I haven't, but I haven't used it a lot as one of my cars is plastic. Anyway, I think that if the wire was sticking it would "birds nest" in the welder, rather than the motor slowing. When there's no arc it feeds perfectly well.
1974 Rover 2200 SC
1982 Matra Murena 1.6

alabbasi
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Re: Welder Question

#4 Post by alabbasi » Sun Nov 05, 2017 8:24 am

It sounds like you have a kink in the liner that's causing the wire to feed inconsistently. Either that or you're not using the right sized drive wheels.

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Luxobarge
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Re: Welder Question

#5 Post by Luxobarge » Sun Nov 05, 2017 8:52 am

Hmmm - another point of view: it sounds to me like it might be electrical, e.g. the wire feed motor is losing power when welding is taking place. It might be worth taking the covers off and making sure that all the electrical connections to and from the transformer and to the wire feed motor are good and sound, and also a good look around to se if there are any signs of overheating or other maladies.
Also a good look at the wire feed motor switch etc.

I's not sure what voltage the wire feed motor uses, but if you have a multimeter that will measure it, I'd suggest measuring the wire feed motor voltage when not welding and then when welding, and see if it's the same. If it is the same then it's probably mechanical, but if it drops when welding then it's electrical - at least this test will narrow down the area that's faulty.

If it's the transformer that's faulty then it's probably time for a new welder, but hopefully not.

Cheers! :D
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arceye
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Re: Welder Question

#6 Post by arceye » Sun Nov 05, 2017 10:13 am

The SIPs were a good welder straight out of the box but I found mine didn't last too well. As Luxo says check all connections, as others say a liner replacement is also a good idea.

Other things assuming yours is pretty much the same version as I used to have, whilst a decent enough welder they get really fussy if not in perfect fettle to the point they quickly become unusable.

So, the plastic feed tube that introduces the wire to the feed wheels gets grooved over time, believe it or not that alone can spoil performance, either change it or at least spin it round so the wear is swapped over.

The biggie is assuming your wire guide / drive wheels are mounted on a plastic block, this was one of the SIPs biggest failings and all just to cut a few pennies from manufacturing costs. Over time the plastic warps and puts a twist / slant on the wheels, which then don't drive the wire properly and cause all sorts of troubles. The answer is to put a strip of metal to brace the two wheels and stop them flexing. The problems with the SIP were well documented, and another mod was to use a seperate transformer for the feed rather than taking the power from the same supply as the arc.

I've just had a quick google, and here is a thread which shows the brace on the wheels, I haven't read through it but it looks like it will get onto the transformer mod aswell so its probably worth a read. http://www.mig-welding.co.uk/forum/thre ... tion.3993/

suffolkpete
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Re: Welder Question

#7 Post by suffolkpete » Sun Nov 05, 2017 12:59 pm

Interesting thread, it looks as if others are having the same trouble and that the motor voltage is dropping due to the load of the arc on the transformer. I've checked all the connections inside and all is good. I don't believe the wire is sticking, if it was it would do it all the time and I can hear the motor speed fluctuating when the arc is struck.
1974 Rover 2200 SC
1982 Matra Murena 1.6

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