Modding a really cheap SWIZ AC Welder - some help please?

[eddie49]

If you wire from one end to the other end of one gang of the 50K twin-gang pot, ignoring the slider, that will give you a 50K "fixed" resistor. In series with that, use the "start" and the wiper of the second gang as the actual speed control. This gives you an effective value of 50K to 100K, covering the ~75K "sweet spot" with a higher degree of control.

 

[Peter Millerchip]

Thanks Eddie - it worked a treat - so simple! I guess I wasn't thinking the problem through fully before (I put it down to lack of Marmite).
Anyhow, its much easier to dial in the motor speed now.

I still am not sure about adding an inductor to the positive cable.
I do not have any experience of wire welding and am thus unable to tell whether the fitting of a choke will make any appreciable difference to the weld result.

Will fitting the "wrongly made choke" cause harm, or reduce the quality of the weld?

I suppose this is a theoretical question. None the less does anyone have a view? Is it worth fabricating something - either using the iron ring I found, or re-cycling a transformer chassis from the guts of a scrapped microwave (say)?

 

[Peter Millerchip]

This is possibly a daft question and I sincerely apologise to the wise ones here if this seems stupid, but having read quite a few articles both on this website and others on basic "Mig/flux core wire/gasless" welding for utter beginners, virtually all of them describe the "setting up" of your equipment/adjusting the welder's voltage with an assumption that your electrode voltage is around 15 - 25 Volts (I assume they mean DC? - its never really mentioned which - AC or DC).

Since I started with an AC voltage of about 27 volts on my cheapo buzz box, since rectification, this has risen to 38.5 volts to 52.9 volts DC, depending on the power switch positions.

From what I have read, voltage has an effect on the arc. i.e. : - more volts = bigger/fatter arc. However, some texts warn about "burn through" if the voltage is too high (especially on thinner gauge materials) - or increasing the wire feed speed to compensate.

Basically, I am now a bit worried if the rectified voltage is too high for comfort?

I appreciate that this AC to DC conversion has been successfully done many times, and everyone seems delighted with the results, but the DC voltage is surely going to be a fair bit higher than the base machine AC voltage output.

I cannot see any easy way to drop 50Volts to 25 Volts (say) at 125Amps - but is that really necessary?

Am I making a mountain out of a mole hill here - but nobody has written anything about "higher" DC voltage at the electrode, as far as I can find.
Is this important?

I have done a little bit more with the welder, but its a bit of a job getting it dialled in depending on the thickness of the material - sometimes its very hard to get an arc going - just a lot of angry splatter beads.

Does the lack of a choke have some bearing on this?

 

[eddie49]

Most MIG welders, even the small, low-cost ones, do have an inductor. As long as the wire you use to make your choke is thick enough to carry the welding current, it can't do any harm. I would suggest starting with the cast-iron ring as a core, stuffing it with as much wire as you can fit in. You may have to cut a slot through the ring to create an air gap ( prevents saturation and increases current flow ).

Regarding voltage at the tip being too high for thin metal: many low-cost welders have this problem. To get a lower secondary voltage, there have to be more turns on the primary ( turns ratio effect ), and additional switches and wiring to provide a wider range. This would all cost more. As you have seen, adding a rectifier and capacitor to a welder with an already high-ish AC output has made this issue worse. Contrast your 38.5v to 53v range with my "Eland 175" , which runs from 16.4v ( 20A ) to 32.6v ( 200A ) in 8 steps.

Short of rewinding the transformer, there is no way to reduce the output voltage. As long as you're above a minimum 2 or 3mm thickness it should still be useable. It will need some practise, running simple beads on scrap sheet at various settings, and posting pictures here for comment and advice. I think that starting a weld with "just splatter" means the torch is too far away, or the wire speed is too low.

 

[Rig Pig]

You can still weld thinner material if you do it in a series of short tacks and allow the parent metal to cool a bit in between welds, a bit of a pain but do able.

 

[Peter Millerchip]

Eddie, Rig Pig - thank you for taking the trouble to give such the kind advice.
Now I understand a bit more about the "economics" of producing cheapo welders!!

I have spent the morning wrestling with that iron ring and a length of domestic "earth" cable (green/yellow sheath) - 6 strand thick(ish) copper - discounting the pvc outer sheath its about 8 gauge wire thickness.
I managed to get 33 turns on.
The ring is 3.5" outer diameter, 2" inner diameter and its height is approx. 1".
I am sure there is some scientific calculator somewhere on the web, which will tell me the inductance from those parameters, but there it is.

I also gleaned some data from such measurements as I could take :- minimum wire feed speed - 30 inches per minute at 2.6Volts across the motor.
Max. wire feed speed (based on present "lower" gang configuration) 224 inches per minute at 6.2 volts.
I could re-wire the wiper of the dual gang pot. as you said Eddie, and move everything up, but faster wire speeds do not seem appropriate at the moment.

I should mention that I had earlier fitted a very much larger, chunky spring clamp, (Parweld make) in place of the original Chinese one (somewhat flimsy). Unfortunately, I discovered that (due to my illness/disability) I could not easily squeeze the clamp enough to open the clamp properly - the spring is extremely strong. I fabricated a couple of 9" 12mm steel bars to bolt to the handles of the clamp, giving me a lot more leverage - problem solved.
Equally, I was able to make sure that this time the "earth" clamp was properly and easily affixed, whereas earlier, I do not think I could get it fitted to the welding table properly.

So I clamped up (properly this time) and tried some test welds on 3mm steel plate, with the inductor connected just before the clamp.

Wow - what a difference!
The effect on the test welding was very noticeable. At a wire feed of about 100 inches per minute, at 35Volts, I was finally able to sustain an arc, with the sound of "frying bacon" and virtually no splatter at all!!

I suppose some of the difference may have been due to a poor clamp connection being put right, but in the earlier test there was no sign of the clamp being "troubled" or running hot.
I would like to think that the main improvement is down to my home-brew inductor!

Anyhow, I am much more optimistic now about using my hybrid Swizzer, and my thanks to all you guys for advice and help to keep me going - I was at the point of giving up at one stage.

So now I must practice, and practice some more. I'll post some pics. when done.

Whatever happened to Bloater Paste - as good as Marmite on crispy toast?

 

[Rig Pig]

I'm tempted to build a DC adapter for my stick welder now! Good work, it's a neat little build.

 

[Cobbler]

Peter, bloater paste was discontinued in 2010 according to Wiki. Never heard of it before, is it some sort of magic welding flux? I'll agree with you on the Marmite, toast or really fresh bread & butter ...... What's this got to do with the welder....

 

[Peter Millerchip]

Go for it Rig Pig - just get the biggest bridge rectifier you can, to give plenty of elbow room for amps.
High voltage capacitors are expensive unless you can source something "special". I nearly overlooked the "50% plus-up" factor of voltage increase on rectification of the AC voltage. My whopper 50Volt caps. were not going to cut it with my overly high AC voltage.

Cobbler - Bloater paste, finally manufactured by Princes I think, used to be found on the top shelf, at the back of the "pastes and spreads" shelf in Tesco's in very small quantities. Now long gone it seems.
Bloater paste was formerly made by both Shippams, and Seniors (in the 1960's) - advertised on tv - "insist on your Shippams for tea". You could see the Seniors' factory from the railway line to Waterloo near Wimbledon (now a residential development).
Wonderful flavour and unforgettable aroma.
Marmite and Bloater Paste (if I had some) stimulate the "little grey cells" to avoid making silly mistakes (see mine above). The paste may well act as a super flux - or a laxative!

(I had a J plate 1600 MX5 import - lovely car).

 

[Rig Pig]

Go for it Rig Pig - just get the biggest bridge rectifier you can, to give plenty of elbow room for amps.
High voltage capacitors are expensive unless you can source something "special". I nearly overlooked the "50% plus-up" factor of voltage increase on rectification of the AC voltage. My whopper 50Volt caps. were not going to cut it with my overly high AC voltage.

Cobbler - Bloater paste, finally manufactured by Princes I think, used to be found on the top shelf, at the back of the "pastes and spreads" shelf in Tesco's in very small quantities. Now long gone it seems.
Bloater paste was formerly made by both Shippams, and Seniors (in the 1960's) - advertised on tv - "insist on your Shippams for tea". You could see the Seniors' factory from the railway line to Waterloo near Wimbledon (now a residential development).
Wonderful flavour and unforgettable aroma.
Marmite and Bloater Paste (if I had some) stimulate the "little grey cells" to avoid making silly mistakes (see mine above). The paste may well act as a super flux - or a laxative!

(I had a J plate 1600 MX5 import - lovely car).

I changed the capacitor bank in my Migatronic a few years ago, eBay came up trumps with a set of BHCs at a knockdown price.

 

[cri8tor]

Thank you Eddie for your kind advice.
I guess I was over thinking the way to go forward with the relays' control, and getting a bit mixed up over it.
I had a sit down with a Marmite sandwich, thought it through logically, and came to the same plan as you have suggested re. the "hot-tip fix".

First job was to make sure everything would fit inside the original hand-piece. I had to do quite a bit of careful paring away of plastic moulding with the Dremel and a burr, to get the double pole micro switch to fit. (Its much fatter). It has two NO and two NC sets of contacts. I cut away the two NC contacts to save a bit of space for the wiring, which was going to be tight!

View attachment 156863

The area pared away is lighter grey in colour.
The original trigger (shown above - red thingy with tiny spring!) became impossible to fit properly, but the micro-switch button is pretty big, and functions as well as a trigger.
I'll have a look at making a better (proper) trigger later, but for now, the micro-switch is fine and functions just as well as a separate trigger. It's firmly buttoned up inside the hand piece.

The wiring/soldering to the micro switch of 4 wires was o.k., but the real problem was trying to fit a pair of wires down the outer rubbery plastic sheath to the electrode cable. It took me nearly two fruitless hours of messing about (I even tried using washing up liquid as a lubricant) before I hit on a way of doing it fairly easily - by cutting around the circumference of the sheath every 9" or so, and using a length of thin brass tubing, pushed up each "segment" in turn, then pushing the new wire through the tube, a section at a time and removing the brass tube afterwards. The job then took only a few minutes to do!!

I then tested it all thoroughly with a meter - all seemed fine, the micro-switch/trigger working easily.

View attachment 156865

I then turned to the upstairs area and mounted the pwm wire feed motor control module.
I had earlier re- located a better pot to the front of the welder and bridged the on/off contacts of the original switched pot.
Just in front of the module is a 12v automotive relay mounted on the front wall. of the enclosure.
I wired a diode across the relay coil contacts, and then pretty much followed what you said Eddie. I switched the neutral feed from the main on/off switch, via the relay and 15V psu.

It worked fine. No more hot tip!

View attachment 156866

I tidied up the wiring a bit with the usual cable ties!
The new 25watt finned power resistor only got mildly warm to the touch.

Tomorrow, I'll fit the second automotive relay, and wire it for the output from motor control module to the motor itself and see how the motor speed it behaves with the original value pot.

Finally I've to fit the MOV, and perhaps then have a go at making an inductor to go in line before the clamp (positive).

Do I need to fit any sort of small value capacitor or resistor across the motor contacts?
(I seem to remember seeing this on some older threads which I cannot find).

Eddie - there was no real documentation with it. There is no reverse control as such. There are 6 Mosfets in ?H? configuration to drive the motor. It can handle from 12Volt in to 50 volt input, at up to 40Amps!
Here's the link to the flea bay listing :- https://www.ebay.co.uk/itm/1pc-12V-24V-48V-40A-DC-Motor-Speed-Control-PWM-HHO-RC-Controller-2000W-MAX-9-50V/263117804952?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
There is quite a number of cheap controllers available now (from China!).

New to the this forum and I know its been years since the beginning of this great modification, but hope you're still answering questions. I've been working on basically the same welder and read all of your posts. Could you clarify the part about the relays? I saw that you had used 2 relays and one has a diode. Does the value of the diode matter and could you please post a pic of how it is wired and/or give a more descriptive explanation of how its wired? I'd also like to know how the second relay was wired and the values of both. Maybe even a picture of both relays. Cheers

 

[eddie49]

Hello, and welcome to the Forum !

Before we get in too deep with the mod, I would like to ask whether you have tried to use the welder as-is?
If so, how does it work for your chosen application?

I'm asking because, with a "Low" setting that may be 40 or even 60 Amps, this machine will not be suitable for use on thin metal. The originator of this thread planned to use it for garden ornaments, etc., which I guess means 1/8 inch thick or more, which would be OK.
Adding an inductor is going to improve the arc characteristics, and making the output DC rather than AC will certainly help too. However, putting capacitors across a DC source raises the output voltage by a factor of 1.414 ( the square root of 2 ), so all the four power settings will get much "hotter", making this machine pretty much unusable on thin sheet.

 

[johnrev]

Just to say that I think Eddie is 100% right. I've done a few experiments with various welders trying to add rectifier and capacitors and all have been horrible welders afterwards. The worst was a stick welder which gave an almighty crack when striking an arc and produced loads of spatter and crackle when welding. My vote is definitely to add the rectifier and a choke of some sort. My latest is using a sash window weight section as the inductor core but as yet I can't report if it works well or not as it's a work in progress and I haven't got that far. Others have used a microwave oven tranformer core and wound on as much wire as possible to form the choke.
My two pence worth but I would add that even some really good machines (such as my old Oxford 170amp) use just rectifier and choke and weld beautifully. Capacitance obvious does work but needs a bit more finesse than just sticking a row of caps in the circuit.
John

 

[a111r]

John, I've got some spare ex-MIG aluminium wound chokes you can have for the postage.

 

[minimutly]

My way of looking at it is that (at mains frequency at least), is that capacitors store charge, or voltage. Inductors store current. If you use an inductor it must be capable of carrying the welding current. Capacitors must be capable of surviving the welding voltage.

 

[Seadog]

Capacitors must be capable of surviving the welding voltage.

They really need to survive current outrush as well, so the lower the ESR the better (reduced internal heating). Of course that current is controlled by the inductor, but too low a value will see an increase in the current as the arc is struck.

 

[johnrev]

A111r if you are offering the chokes to me that would be really great. It would remove one unknown variable from the current frankenwelder I'm playing with. This one is in the region of 130-140amps so any choke of that power rating will help no end. If you PM me I'll get payment to you thanks.

I wonder if there is some kind of formula for inductor/capacitor/weld current/voltage to produce a good result. When I tried adding caps to a Topmig 150 it was a hopeless result. I started with all my caps in parallel and found the power actually seemed lower needing a higher power setting for welding and also found the transformer and inductor got uncomfortably warm very quickly although the caps stayed perfectly cool. Although the welds were ok it didn't feel 'right' so started reducing the number of caps (I had fitted 12 and each was 4,700uF) and the welder felt nicer each time I took some away till I was left with two. Removing these made no difference.

I read somwhere on here that someone wanted to fit caps to a new machine (Migatronic or Oxford or something) to bring it up to the same spec as the slightly larger model and was told by the manufacturer that it couldn't be done without major changes to other parts (transformer??). I wonder if this was just because of the higher voltage the caps would produce or if something else was needed to suit the capacitor effect.

John

 

[roofman]

Whatever happened to Peter Millerchip the OP...was not seen since his last post in Oct 2018 so we never got to see his welder results

 

[Barking Mat]

I think in thé opening post hé stated major health problèms?

Dunno, then i skimmed through thé electrickery gibberish.

 

[a111r]

A111r if you are offering the chokes to me that would be really great. It would remove one unknown variable from the current frankenwelder I'm playing with. This one is in the region of 130-140amps so any choke of that power rating will help no end.

I think I've got three. Two from Pro-90s and one from a 150 Amp Sealey.
I'll have a look tomorrow. I suppose they could be connected in series, but that would require a rather spacious case.
Probably the Hermes postage rate will be the deciding factor on the quantity you'll want, 5 to 10 Kg is £6.30, 10 to 15 Kg is 8.30.