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Thread: SIP MIG welder improvements (WIP)

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    Paid Member Trev16v's Avatar
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    Default SIP MIG welder improvements (WIP)

    (This is still under construction and so contains a few TODOs.)

    Introduction

    This is a short write-up I've thrown together to show the modifications and fixes I have done to my SIP MIG welder. I can't take any credit for any of these ideas because they originate from other people on various welding forums. I also didn't think to take detailed images while doing the modifications I'm afraid, but hopefully some might find this useful and inspiring. I'll provide links to other forum threads where you can get more information.

    By doing these fixes, particularly the wire feed transformer modification, a turd of a machine that I always found to be pretty much unusable since buying it brand new has been transformed into something that performs reasonably well.



    Replacement of plastic liner with metal liner

    As standard the welder comes with a plastic liner which is deteriorates quickly and provides too much resistance against the wire feed. Eventually you might even get bits of plastic 'swarf' from the liner clogged up in the torch valve. I bought a replacement length of metal liner off eBay. When I received it, I was not amused to find that I had paid quite a few quid for what looks exactly like net curtain wire! So to replace the liner in your SIP, you could first try just getting a few metres of net curtain wire from a furnishings / DIY place / Argos. When you remove the old plastic liner from your machine, you will find that the metal threaded fittings can be removed from each end of the old liner and they can be fitted onto the curtain wire (they thread onto the outer white plastic coating).

    With the metal liner (net curtain wire!) fitted, the wire feeds very nice and freely.

    Replacement the torch valve

    You probably don't need to replace this unless yours is damaged or contaminated. I replaced mine because the thread for the contact tips was damaged, and I also suspected it may have been contaminated with lots of junk inside.

    The mistake I made was to buy a plastic-bodied one off eBay. This was a problem in the case of my torch because the metal body of the original one is used to make the electrical connection with the torch button contact. Therefore I had to make a new contact strip that you can see in the image. Bear this in mind should you be looking to buy a replacement for yours. I had to bend the contact strips to ensure that arc and wire feed only started after gas has started to flow.






    Wire feed mechanism brace

    The wire feed mechanism chassis is made of plastic, and the tensioner is pivoted on a plastic pillar that bends far too easily. Fitting this little metal brace is an absolutely essential modification that's easy to do. I spent about three minutes making mine (as you can tell). Does the job lovely. Even when brand new and gently tensioned, the feed mechanism always sounded unstable. Now it can provide a very strong wire feed, at a much more stable speed, and actually sounds like its running smoothly.



    Dedicated power supply for wire feed mechanism

    (This section is still work in progress; I will add more detail shortly.)

    Even after replacing the torch liner, torch valve, and modifying the feed mechanism and being satisfied that everything had been perfectly tweaked and set up as it should, the machine would still be infuriating to use. By this stage, the wire feed was working very well when tested with no arc, and would withstand much resistance I placed on it by hand. Yet when actually creating an arc and welding, particularly at lower power levels, and with everything set up correctly, the wire feed would fluctuate or even stall completely such that the wire just kept balling up.

    The actual problem is that the wire feed mechanism is supplied from a tap off the secondary of the main transformer which supplies the arc. The supply to the motor is therefore electrically noisy and unstable when arcing. The answer is to install a dedicated mains transformer for the motor drive.

    Threads where this modification is discussed:
    http://www.mig-welding.co.uk/forum/s...ead.php?t=4061
    http://www.mig-welding.co.uk/forum/s...ad.php?t=40097

    Parts required:
    Farnell 1780896 - PRO POWER CTFCS100-12U (Transformer) (http://uk.farnell.com/jsp/search/pro...sp?SKU=1780896)
    Farnell 9549374 - GBPC2501-E4/51 (Bridge rectifier) (http://uk.farnell.com/jsp/search/pro...sp?SKU=9549374)
    (TODO - Complete this list. Refer to threads above also.)

    Note that there is a slight disadvantage to this modification. As standard, the motor speed is governed not only by the speed control potentiometer but also by the setting of the three power rating switches. The selection of these switches determines which taps of the main transformer primary are used and hence control the current at the secondary for arc and motor drive. This is useful because at a lower power arc, the speed control knob gives you a lower range of speeds, and so on. After doing the modification, the motor speed is only controlled by the speed control pot, so a bit more care is needed to adjust it between power settings.

    Location of new transformer

    I mounted the transformer in a different place to that seen in all of the existing threads that discuss this modification. Many people mount the transformer inside the wire feed area (which can be dangerous if not done properly). I found that there is a convenient area it can be neatly mounted inside the welder itself as shown. Some care is needed to get it there, and I took care in particular to ensure that the nearby metal plate that the two rectifiers are mounted on (see left of photo below) won't come into contact with it (because the anodes of those rectifiers are mounted on that plate, so it's not at chassis potential - beware). New transformer is positioned towards bottom of image, beneath the black component which is the reverse side of the plastic wire feed assembly.



    More images.







    Nuts and bolts visible on the wire feed side show where I mounted the transformer.



    Bridge rectifier mounted nearby at the back there (blurred).




    I'll come back and expand on this and provide a more detailed guide if needed, but all the information is already captured in the links above, so my images here really just serve to show how I went about physically mounting the components which to be honest is possibly the trickiest part in such a cramped machine.
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    The main problem with these migs as I now know...............DUTY CYCLE!!!!
    It's absolutly shocking. Weld for 1 min and give it 3 hours rest is not the way to go, and as for calling them 'Turbo' migs by placing a crappy little fan inside is a joke.

    If you have a SIP (like myself) then Trev, you're a star and what you've done hits the nail on the head. If you haven't, I recommend you buy something else, with better control, duty cycle, euro torch and more power.
    I think my next big buy is a TIG. I've done MMA, MIG and gas welding courses, and tried a bit of Tig in work. It's a b'stard to get right so a trip to college maybe on the cards too

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    I did a fair bit of reading up on that welding forum prior to buying the MIG and the over all consensus was that these SIP units are not that fantastic, but much better than the Wolf stuff on Ebay. In fact a mate offered me one for free as it was bough while his big MIG was getting fixed. But I stumped for a new Clarke 135TE. I have not done much high amp welding yet with it but have done a fair bit of long runs and not had any overheating yet. But I have some work to get done on a boat trailer next week so fingers crossed.

    I have swapped the liner out for a metal one before I even used it so can’t really say if it has made any improvement.

    But I have replaced the earth cable and the earth Clamp and I think it has enabled a more stable arc.

    Still need to plumb in the larger gas bottle but at the moment I find it is being lobbed into the boot of the car so the wee bottles are handy for mobility.

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    I must say I don't think I ever recall the thermal shutoff kicking in on my SIP. That's perhaps one positive thing I can say about it. Maybe it's because I'm a bit slow with the welding and don't work it hard. Having said that, I have worked it pretty hard on occasions where I've done heavy stuff like building my steel bench and also building the chassis rotator.

    Regarding the separate motor drive supply transformer modification, one thing that immediately struck me about it is how nice and stable the arc 'buzz' is now. It's like more of a constant "bzzzzzt" because of the fact that the wire feed speed is so much more stable. And of course the resulting weld is nicer.
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    I have a spare old 'chocolate teapot' SIP. Big bugger, but pretty useless really ATM. Have already fitted new liner etc. No real improvement. Will give these mods a try, unless someone has some spare time wants to buy it from me cheap......

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    Quote Originally Posted by Trev16v View Post
    I must say I don't think I ever recall the thermal shutoff kicking in on my SIP. That's perhaps one positive thing I can say about it. Maybe it's because I'm a bit slow with the welding and don't work it hard. Having said that, I have worked it pretty hard on occasions where I've done heavy stuff like building my steel bench and also building the chassis rotator.

    Regarding the separate motor drive supply transformer modification, one thing that immediately struck me about it is how nice and stable the arc 'buzz' is now. It's like more of a constant "bzzzzzt" because of the fact that the wire feed speed is so much more stable. And of course the resulting weld is nicer.
    It'll depend on what you're welding. If you're doing thin panel work then you should be OK. Thicker metal - for roll cages and so on - would be more likely to cause a problem.

    Good tips. I'd still buy a Cebora, Sealey or even a Clarke (assuming it's hobby welding not full time use) before I went near a SIP though
    Megasquirt for the win!! Long Johns for the Win-(ter Mechanic!)

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    Cheers Trev!, will be upgrading mine after looking at this thread. I got mixed results with mine and gave up with it in the end (same model as yours), the wire feed speed was impossible to get right and now I know why!.

    Megasquirted 16vG60/JDM Mitsubishi GTO TwinTurbo.

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    Hello Keith. Really good to see you around on here again.

    Please let us know how you get on with the modifications and if you need any help.
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    Thanks mate, will let you know how it turns out .

    Megasquirted 16vG60/JDM Mitsubishi GTO TwinTurbo.

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    I have a SIP 190 mig and agree whole heartedly, they're not a good mig, worse still for a novice trying to get one of these things to weld correctly could be even dangerous if the welder does'nt know a good weld from a bad one. I have done some of the same mods as the op, I even fitted a euro torch, and I have made a poor mig into an average one. My advice to anyone shopping for a mig is not to buy new but to buy a good quality second hand one, such as Cebora, Elland, Miller (if you can afford it!) Murex or Lincoln ect.

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