Author Topic: Welding on clean DC  (Read 2060 times)

BruceM

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Re: Welding on clean DC
« Reply #30 on: May 30, 2019, 06:46:14 PM »
I got my new cables made up last night, will do some rewiring to day. Hopefully I can get some help for current and voltage measurement.

Pity 6V batteries cost twice as much as 12V!


BruceM

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Re: Welding on clean DC
« Reply #31 on: May 30, 2019, 11:45:37 PM »
I did some test welds with my new cable setup.  Some improvement- with difficulty I can now use the 7018 rods...which as MikeN suggested, don't have slag inclusions. With the 7018, the arc keeps stopping, but I can restart and work back to the still hot old puddle, without pausing for chipping, and I still see no slag inclusion.  As Mike said, it 7018 works way better (arc is steadier) pushing the rod instead of dragging it.  Thanks, Mike!

I measured the amps and volts,  recorded the meters via camera on tripod while welding.  I seem to be in the 85-100 amp range most of the time on 3/32 rods, but some blips to 110 and 60. I was using a digital clamp on amp meter so difficult to see the real picture. (Digital curse.)  I put the meter between the battery and the choke in hopes of seeing the smoother, average current. 

I tried 6011 rods-  they are terrible, slag inclusions, bubbles.  They are the AC version of the 6010 rods, which I have on order because no one stocks them locally. 

I tried a 6013 - 1/8" rod. It seems to work fine, more metal for the same flux, no harder to work with. I didn't check the amperage on that, and I should.  Given the problem with slag inclusions with 6013, I think I'm better off getting the hang of the 7018 rods. 

I had some trouble seeing with my new welding helmet filter; it's supposedly a 9 when "on".  It's a bit too dark for me, and then I realized that my cataracts are probably adding to the problem. An old T shirt taped to the helmet to get rid of back lighting helped, but light is still coming up from underneath, and it's still so dark I can't see well.  Plan C- maybe some welding googles, with a 6 filter???

Edit: Current on the 1/8 6013 is about the same, 80-110. Voltage drop on the choke at 100a is 0.4V, as expected for 16 feet, 6 strand 12 awg. 

I must drag/work the rods very close, right on the flux edge, can't pull back at all.  I will try 36V tomorrow for comparison.  Oh, for a 6v battery!







« Last Edit: May 31, 2019, 02:58:26 AM by BruceM »

BruceM

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Re: Welding on clean DC
« Reply #32 on: June 03, 2019, 04:18:03 PM »
Decided to skip the 36V as all written reports indicate it's excessive, too high current, splattering mess maker.  30V would be appealing to try but I don't care to blow another $150 for a 6V battery to try it.  A linear regulator to hold constant selected current starting with 36V is possible, but needs about 27 NOW/Fairchild linear rated mosfets (and 27 controlling op amps)  in parallel due to the high current, a big heatsink and fan. The mosfets are rated about 10 amps at 10V drop, (100W of heat to be dissipated) but for a robust design I'd want to only pull 6 amps each.  160 amps max/6= 27 mosfets and op amps.  Possible but impractical.  Makes me like the limitation of a fixed 24V welder with stabilizing choke.

In reading more on the web about DC welders, I find that all the old school big name DC welders have substantial DC filtering/arc stabilizing chokes designed in...and buying those "dialed in" chokes as replacement parts for Miller MIG rigs run about $435. and up.  I thought it was interesting as 38ac's sage comment about high quality welders being worth the money recently started making lot's of sense, electronics- wise. In the cheapy units, the lack of a well dialed in choke reportedly results in more spatter and more difficulty starting and maintaining arc. Arc smoothness and stability suffers, making welding difficult and poorer quality.  A large choke will cost more than the total price of the cheapy switching power supply stick/mig welder.  In the better quality "inverter" welders, the arc stabilization is done electronically, allegedly. 

I'm dabbling with my poor welding vision issue this week, while waiting for some 1/2 steel plate needed for my latest attempt at a 5" wide trencher-bolt-on to a deep ripper from County Line.  My 24VDC arc is so short, and my cataracts (a special MS related type)  bad enough that I just can't see enough area ahead of the arc with the shade 9 or 10. I'm going to try to open up one of the $11 active (pv controlled) welding lenses to see if I can add some circuitry to adjust the shade level.  Even the fancy digital ones don't allow adjustment below shade 9. 


BruceM

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Re: Welding on clean DC
« Reply #33 on: June 03, 2019, 08:09:48 PM »
I tried a gold shade 9 lens in the helmet- with a hood of fabric to stop glare, I can see the work piece just fine in full sun.  Yea!  I made a permanent hood out of a navy blue shirt fabric, glued with contact cement to the helmet.  Once it dries up for a bit in the sun I'll do some test welds.
If the shade 9 is dark enough to weld with, I'll be all set.

I did take one of the cheap PV/auto-darkening lenses apart, though since I had to cut through the glued plastic case, I broke a couple surface mount resistors.  I was able to experiment with the LCD and little PV panel.  3V turns the LCD fully dark, 1.5V perhaps 25% dark. It stays dark so is holding the charge if 3V is removed, must be discharged to clear (shorting leads).  The PV panel is 6V  open circuit in full sun, and 3.5ma short circuit.

There was a battery on the circuit board, and some sort of oscillating circuit, which I could hear on the AM radio right near the board. I suspect charging the 3v battery from the PV, or one of the chips is a micro controller.  I may feel better when welding without this on my head. 

The LCD could be controlled with some linear circuitry and have no emissions at all, plus adjustable darkness up to shade 11.  A bit of a project, as rapid and reliable arc detection will take a fair amount of fiddling, plus switching to a variable darkness very quickly may also take some fussing about; the capacitance of the display must be overcome.

An interesting project if I was getting paid for a couple weeks work, but I'm not that desperate, yet.





mikenash

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Re: Welding on clean DC
« Reply #34 on: June 04, 2019, 08:02:03 AM »
Bruce FWIW I reckon as we get older & our eyesight gets crappier - welding is a lot easier if the work is well-lit, even what we would think of as over-lit

Sure you can weld in bright sun but the auto visor may not like that . . . but if you have a big lamp shining on the work - I have found that better.  It seems counterintuitive as the arc is light - but I have found it good

Do you know about diopter inserts for your welding helmet?

Cheers

glort

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Re: Welding on clean DC
« Reply #35 on: June 04, 2019, 01:13:17 PM »

You should see about having your cataracts done Bruce.
My dad had one done about 6 weeks ago and reckoned he could see better that night. He's booked in to have the other eye done in a few weeks.  From the time they took him into prep till the time they rang to come get him was under 2.5 hours. I think the doc did about 20 people that morning. It's only about a 15 Min actual op they said.

I know Dad is a lot happier for having it done much as he was scared about it. It's taken a lot of his frustration away and made him more relaxed apart from the fact he has been squinting to see out the good eye as the one he hasn't had done is now so much more limiting.
The only thing he said was the eye felt a bit scratchy for a couple of days but I couldn't slow him down and get him to take it easy afterwards.
Didn't deter him a bit.

I'll ask if they can give him a prescription for something to sedate him for a few days after this one so he''ll  have no choice but to rest.
Sure didn't put him off his Tucker either!

BruceM

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Re: Welding on clean DC
« Reply #36 on: June 04, 2019, 09:51:49 PM »
I've got an odd type of cataract associated with MS.  It's not "ripe" for surgery, yet.  With amber tinted aviators that fit well, I can see quite well for driving.

I'm building a rolling box for the batteries and choke, with some storage on top.  Down to the welding lead connectors (which oddly have no isolation from the mounting screw) and then some cosmetics.  8" main wheels in case it goes traveling.   I'll post some photos when it's completed.

For 1/8 to 1/4 steel, with 7018 and 6013- 3/32 or better, 1/8" rods, it works pretty well once I got used to the DC short arc.  MikeNash's tip on pushing and not dragging the 7018 was a game changer; thanks Mike!  It just wouldn't stay lit otherwise.





mikenash

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Re: Welding on clean DC
« Reply #37 on: June 05, 2019, 09:49:11 AM »
Bruce, you're welcome of course.  Cheers

BruceM

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Re: Welding on clean DC
« Reply #38 on: June 10, 2019, 01:08:23 AM »
I got the trencher welding done, it's over at my neighbors for testing.  We need to add more "wings" to keep the diggings out of the trench.

I'd love to add another 6V for hotter rods, but it's not in my budget and it's serviceable now on 3/32-6013 rods.  Because this is a choked fixed voltage welder, no long arcing is possible, nor much whipping.  It's limiting, but it will do serviceable work.

As a side note,  I think direct battery welding might be better with a MIG setup, since that is by design a fixed voltage, and 23V would be well suited to 0.032" wire that is commonly used.  A smaller choke or none might suffice, also.

I made a rolling case for the two group 29 marine deep cycle batteries and my custom gapped toroidal choke/arc stabilizer.  I used standard welding connectors and made 12 foot, 2 awg cables, brass C clamp grounding connector.  I'm using fixed shade 9 glass in the welding hood, which is OK if I can weld in direct sun.  I've got a shade 6 lens to try for shaded work.

Floor space in my shop is getting tight so I wanted a small footprint.  The front and back are removable. Welding tools in the bin on top. I intended to fill in the sides but decided it was fine open; the batteries are accessible but well protected from an accidental short.  I'll give it a coat of gray Behr Ultra once the green Douglas Fir has dried. Pictures attached. 

I know you're thinking; why didn't I weld a steel rolling cabinet.  I'm cheap, and this was built with about $25 worth of wood.  I had the salvaged castors, and paid $8 for the other wheels.   Wood also makes me feel safer when connecting cables and such; a wrench touching the frame won't cause a melt down/explosion.






glort

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Re: Welding on clean DC
« Reply #39 on: June 10, 2019, 09:29:58 AM »

That is without doubt, the best looking welding trolley I have ever seen! I think it would look great just with a coat of clear lacquer.

I also think wood was a good choice as is leaving it open at the sides.  No chance of shorts and I don't trust  batteries any more especially in applications like this. I have had good batteries explode on me for no reason. They were well connected, in free air and no where near any ignition source. It was something internal that could not be forseen.
 If that were to happen with this setup, with the open sides the pressure is vented and things, especially metal fragments, are not going to go flying.
That said, some louvred panels to stop acid splash may be good.  Last battery that went off showered me in acid and right on my face. Was the Middle of winter but luckily I was right next to the swimming pool and threw myself straight in. Fortunately I just got away with a lacerated wrist from a piece of flying plastic.

As with many things you discuss Bruce, you have had me thinking about this.  I looked up spool guns and far as I can see, they can be used for steel welding although for some reason are not often used for that.  I thought a gun would be easy as you just have to hook the power up and don't have to worry about the long wire feed.  I see that regular setups could be had for a bit more money. Tempted to try the mig setup with solar panels although it's likley the volts would be too high at around 30 but with thicker 1.2mm wire and welding heavy plate may be OK.  Not sure what amps would be needed though and the Volt/ amp relationship.  100 amps on solar would be bit of a pain to parallel all the panels even with those x4 adapter leads.

Interested to see where you take this Bruce and well done with the setup.  Looks more like furniture than a welder.  :0)

mikenash

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Re: Welding on clean DC
« Reply #40 on: June 10, 2019, 11:02:36 AM »
That's the best-looking welding trolley I have ever seen  :)

dieselspanner

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Re: Welding on clean DC
« Reply #41 on: June 10, 2019, 11:44:48 AM »
Nice trolley!

And an interesting thread, too

Cheers
Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

BruceM

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Re: Welding on clean DC
« Reply #42 on: June 10, 2019, 04:41:31 PM »
Thanks, Gort, MikeN, Steff.  Yes, it was like sloppy, fast and fun furniture work, using construction lumber, exposed screws. A far cry from fussy hardwood furniture/cabinet work.

MIG welders use a fixed voltage regulation, which is just what you get naturally from batteries. The shorted wire feed method to the puddle will cause some spikes in current, and I think it's interesting that fixed voltage proved to be the best regulation scheme for MIG, instead of the current regulation long used for stick welding.

If I ever mess with a direct battery powered MIG type setup, I'd prefer keeping the wire feed motor away from me, instead of the spool gun.  I'd have to shield and filter it as I expect the cheap ones are brushed DC motors, and I'd have to make a linear regulator for motor speed control.  Stepper motors might also be used for better speed control, and that means a microcontroller to shield and filter, and I could use the soft switched H-bridge PCB board from my low EMF inverter.

A battery powered MIG would be an interesting project and I suspect a far better welder, but for my limited use I think the utter simplicity of the 24V dual marine battery stick welder is OK, even though the fixed voltage regulation (with some current regulation aid from the choke) is quite limiting compared to the fixed (adjustable) current regulation most stick welders provide.

I did have an interesting development when checking out the active welding filter; the small one I bought for $11 was in fact still a radiating EMI source, with a microcontroller.  It was just a better design so I had initially missed it with the AM radio at a distance; it only could be picked up right next to the filter.  I feel MUCH better after welding using the passive glass filter.  No matter how bad my hearing gets, I won't be wearing a digital hearing aid!



BruceM

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Re: Welding on clean DC
« Reply #43 on: June 13, 2019, 03:03:45 AM »
Got a 120VAC powered trickle charger finished today for the 24V welder batteries.  It's designed to be left plugged in, and whenever I turn on the inverter for laundry, it will charge at 1.5 amps max to 14.2V x2 (28.4V) and hold it there while the inverter is on.  I was motivated to do this when I found that I had a small toroidal transformer on hand that would do the job perfectly.  I didn't have a project box the right size, but I did have some light gauge galvanized sheet steel on hand, so I made the box. 

It's job is to keep the batteries in good shape when not in use.  I designed it to be low stray magnetic field, but I had to make it a small regulated DC linear supply (with bulk capacitors added later after initial testing) when I found that the large current loop at the batteries was causing too much stray field when fed "lumpy" DC.  9000 uF of 50V electrolytics was almost everything I had on hand, and that works fine. Screwed up my perf board layout but oh well.  An LM317T linear regulator I had on hand limits current to 1.5 amps, which is fine.  Even at these low currents, I had to add a fair amount of EMI suppression for the bridge diodes;  0.1 uF caps snubbing each diode, and common mode chokes on incoming AC and outgoing DC to knock down what's left.  The diode noise is stronger than normal because of my 5 step sine inverter with 43usec rise/fall times on each step. 

I plan on using a commercial switching battery charger for regular recharging after welder use.  I ordered one for $35 that will charge 24V at 10 amps.  If that checks out OK,  I'll add some EMI suppression and call it good.
« Last Edit: June 13, 2019, 03:13:21 AM by BruceM »

mikenash

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Re: Welding on clean DC
« Reply #44 on: June 13, 2019, 07:39:24 AM »
Life would be so much more do-able if I understood how to think through all that stuff . . . But I just don't

Good onya Bruce