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Up Topic Welding Industry / General Welding Discussion / got them watertight , but what a hassle!
- - By bzzzzzzzzzz (**) Date 09-07-2002 20:32
Just tried the real finished project I was working on. Not the practice piece this time. The 20 gauge 304 welded very inconsistently. Making a pan which is 2x2 feet, with 6" sides. The welds are done after the the sheet is notched in the corners and folded. My technique is open for ridicule or critique. The sides were bent to fit as tight as possible. Then I tacked the joints with .024 308L wire. after tacking it every inch or so I ground the tacks down to a smoothe line, being careful not to grind deeply into the sheet itself. Then I wire brushed it clean. I then set my machine on low power,(45 max. amps.) With 75/25 gas set at 20 cuft/hr. I welded directly into the outside corners. (using a drag motion) I had some burn through. I also had some real problems keeping the arc going along without getting the Pop, pop, pop, thing. Two of the four welds were nearly perfect. The other two required more filler which made it look "bird crappy" to say the least. I can't go any lower amperage-wise with the welder I have. I also cannnot get any suppliers to sell tri-mix in the size tank I have. (40 cu.ft.) I guess the real question here is why is that arc so hard for me to maintain? Are the higher quality low amp machines like millermatic easier to maintain arc with. I don't ever expect to learn "how to weld" from this board, but specific answers to specific questions will be welcome. The pan was indeed watertight when done. I also would like to mention that when I adjust my wire drive, there is a very small window in which the machine arcs smoothely. Is this a function of machine quality or just the nature of wire welders in general? It is a Craftmans 75 amp.
Parent - By welder_guy2001 (***) Date 09-08-2002 06:49
maybe instead of trying to keep a long steady bead going you should try welding 1 or 2 inches at a time. thin sheet metal tends to heat up very fast anyway. it could be a problem with the quality of your machine...could be the thin materials. did you weld inside the box or the outside corners first? a trick you can try to prevent burnthrough is, use a backing plate...preferably a piece of 1/4" copper. if you don't have any copper, a piece of 1/4" steel will work. what you do is, in the area you're having problems w/ burnthrough you put the copper on the back side of the joint to suck the excessive heat away. also, if you do burn through and the copper is clamped tightly against the joint, you can actually weld onto the copper and the bead won't stick to it, but it'll spread out and fill in your hole. if you use a piece of steel i'm pretty sure stainless steel will fuse to it, but it'll still work to take away excessive heat.
Parent - - By Niekie3 (***) Date 09-08-2002 21:19
I have a problem with your gas. I believe your application is not critical, so the C pick-up may not be such a big deal. What is probably a bigger problem for you is that the CO2 in the gas makes it much hotter than would be the case with an Ar + 2% O2 mix.

I am assuming that you are welding with solid wire and not flux core? If you are welding with flux core, then the gas is probably not the culprit.

Regards
Niekie Jooste
Parent - - By bzzzzzzzzzz (**) Date 09-08-2002 21:53
Not using flux-core. Stainless 308L .024 wire. I may try another approach to this project. Rather than weld, after tacking the outside corners, I'll clean them until shiny,apply proper flux, and use 56% silver content braze alloy to seal them watertight. I tried this approach earlier with lap joints and rivets but it was way to elaborate for me to drill, bend, and rivet with the hand tools I had. I think the tacked, then brazed right angle joints in the 20 gauge will tolerate the heat of a fire OK. (actually only needs to stand slighlty over boiling point) Probably will have much better corrosion resistance too. These are finishing pans for maple syrup. For my own personal use.
Parent - - By welder_guy2001 (***) Date 09-09-2002 02:11
in that case, it would be best to make a lap joint for the corners. bend one corner to a 90 degree angle and make the other corner lap over it. that way the braze metal will have something to flow into. and i'm not sure if brazing will work good on stainless steel. i don't see why it wouldn't...maybe somebody else knows about that.
Parent - By bzzzzzzzzzz (**) Date 09-09-2002 02:57
Yes it will work on stainless. Just need the correct flux and alloy. Lap joint means some serious fabrication that I don't want to (cannot?) do. It's very hard to achieve a close enough fit-up on stainless this way. The sheet is extremely prone to warping when heated for the brazing. The tack welds will allow me to stitch them together without changing the fit-up. I think the braze alloy would be plenty strong with the tack welds holding it solid. It was hard enough for me to notch and bend 20 gauge with hand tools. We're talking cut,clamp,pound,bend. The only thing that concerns me is the oxide that form during welding. I can wire brush the outside, but no way am I able to get the inside shiny clean after the arc hits the outside of the joint.
Parent - By dee (***) Date 09-09-2002 08:20
Bzzz
This pan will be unable to exceed the boiling point of the liquid within it up to the level of the liquid (it might come apart down to the level of the syrup but no further) You could use plumbing solder if it would wet the stainless.

Personally I feel you should solve the weld issues, however.

Stock stainless angle could help solve the fabrication problems of a lap joint, and an expedient oven will solve the warpage problem if you can clamp the "tinned" angle in place over the fluxed steel and allow for movement as the silver solder melts, flows, and loostens the hold a typical clamp would have. Preparing the angle by filling its surface with brazing alloy (as I described by calling it "tinning") could also minimize the amount of heat necessary to apply directly to the pan and possibly help normal torch techniques.

It is, I think, a shorter route to solve the weld issue.

Regards
d



Parent - - By dee (***) Date 09-09-2002 07:48
Bzzzzzz
Listen to Neikie3; I agree with him. You will also get satisfactory results from his advice where and if we do not agree.

You should be able to find a supply for the ArO2 he suggested. There is also an alternative mix with a much much smaller amount of CO2 (I think 4% don't trust me on that specific detail) than you presently have which, under your circumstances, I would only consider as a second choice.

More Ar will also fix that narrow band of "sweet spot" issue you noted.

Regards,
d
Parent - - By bzzzzzzzzzz (**) Date 09-09-2002 10:19
None of the suppliers will fill my size tank with a special mix gas. They all require at least a 120 cu.ft. tank before you can order custom mixes. I would like to try the gas you reccomend. How would straight argon perform? I can get this in any size tank locally. Thanks for all the good ideas. I must agree that welding the whole thing would achieve the best results. Assuming the welds lay down well. That problem with the arc sputtering is the real problem here. The joints that didn't have the arc interrupted were perfect in my "unprofessional", yet fussy opinion.
Parent - - By dee (***) Date 09-09-2002 17:15
Bzzzz
Straight Ar would probably be impractical for several reasons, most important of which is that the problem symptomized by the sputtering would probably remain unaddressed and continue to confound your efforts. Measure max volts and amps (or rate of wire feed) and I will see if a practical transfer is attainable at or below those parameters.

Addressing the equipment issue, I would look at the gas delivery at the arc. I found, particularly outdoors in a breeze, that increasing the gas flow can solve similar problems.

Are you sure the wire feed is not balky? A slipping drive roll can cause intermittant problems with symptoms almost like an irregular stick-out or intermittant voltage would present. I understand feed problems increase as wire diameter decreases.
Similar problems with intermittant weld energy can be traced to faulty ground connections at the work, at the cable connection in the clamp, and perhaps at the machine.
Stainless offers a clean surface to connect to but a relatively high resistance; it's a cousin to heating element wire and you will have nothing to loose if you try to insure the welds are similar distance from the ground clamp, particularly at what may be the marginal parameters you are using.

Finally, have you attempted to use the parameters where the transfer is smooth and consistant but tends to burn through, by laying back in the puddle a bit, lengthening the stick out, or changing the feed angle?

I have to admit that I am lucky to have a rep who cooperates with me and appreciates the business I give him in return, sometimes even when I really dont need anything. I have maintained a relationship with several distributors for many years, and ended one of them not very long ago, without burning bridges, in consequence of a problem I had which he wanted to exploit excessively.
You may succeed in a compromise and obtain your gas if you make your intentions clear. A deposit equal to the purchase price of whatever size tank is available of the standard ArO2 stainless mix they stock should let you out of their store informally with a supply of gas for a few days or so and no permanent lease or rental. You will be returning a nearly full tank to further enhance their profit, anticipating return of your deposit at the cost of only a fill. Final cost around here is about $25 US. or less. Locally this is standard practice with established and trusted accounts even with return of an empty tank. Your supplier has needs as well, and you may understand how you are in a position to help him if you can both address each others needs. You will benefit from communicating that understanding and looking upon making various purchases from him that may have been a little cheaper or more convenient if made elsewhere as a long term investment...

I hope you have luck and can break one of the dealers in, at least in time for next time.
d
Parent - - By bzzzzzzzzzz (**) Date 09-09-2002 21:27
VOTAGE MEASURED AT THE MACHINE LUGS-22V. ON LOW, 27V. ON HIGH. MEASURED AT WORKPIECE AND WIRE ARE THE SAME AS ABOVE. ALSO CHECKED THE POT. AT THE MOTOR CONTROL CIRCUT BOARD. INFINITE RESISTANCE FOR ABOUT THE FIRST HALF OF ROTATION. THEN IT GOES DOWN TO THE LEAST.(30 OHMS) IN A VERY SMALL AMOUNT OF MOVEMENT. THE LAST 30 DEREES OR SO DO NOT CHANGE IT AT ALL. THE READING ON THE POT. SEEMS TO POINT TO EITHER A SHORTED POTENTIOMETER OR JUST A POORLY DESIGNED MOTOR CONTROL CIRCUT.
Parent - By dee (***) Date 09-10-2002 02:18
Bzzzz

I have edited out an hours worth of info for the sake of brevity.

You are fighting all kinds of disadvantages. The drive rollers may well be too loose if you seem to have that feeling- tighten them for a few feet of bead to see if it helps. I generally advocate bold adjustment (within reason; dont break anything) of anything for the same reason artillery advocates it, and I bracket the adjustments the same way. It's unwise to change anything like gas, etc unless you are sure of your machine first... These rolls and contact tips are different from the ones you used for FC (is the liner also properly sized for the thin wire?)

Consider a backing plate (or two) of copper or at least aluminum- preferably angle- to permit more latitude with the gas you presently have at a range of perhaps 12 to 14 weld volts (OCV somewhat higher) but you must be confident of the drive rollers, tension, contact tip size and any other drive issues first.

You can use one ground clamp and merely relocate it near each weld.

!00% Ar will work but presents its own difficulties and is not the recommended gas. You will be able to achieve spray parameters but you will likely find the arc difficult to direct. With Ar, short circuit transfer has no practical parameters.

I am sorry I didnt relate to the wire size earlier.

If I am rekoning right, the voltages and current required for that small wire tend to be impractical with Ar rich gasses and raise other issues. With short circuit transfer at a 14 weld Volt range for an 035 wire I can only guess at something like 9 weld Volts are required with an Ar 3% Oxy mix. Wire this size is beyond my experience, and my notes do not cover it. Unless you are convinced your equipment can remain stable and initiate an arc at these parameters, my opinion has changed to: sink away the excess heat and use higher parameters known to be stable on your [adjusted] machine.

Sorry about the confusion
d
Parent - - By dee (***) Date 09-10-2002 02:23
Bzzzz
Sounds like you located a problem in the wire feed system?

You are aware that in-circuit testing can be misleading? Do not hasten to remove it. You neglected to tell us you did not have full range of adjustment of wire feed.

If you cannot get part try MOUSER electronics if all else fails- you must know the value, dimensions, and if it has a linear resistance curve (which it should probably be).

d
Parent - - By bzzzzzzzzzz (**) Date 09-10-2002 02:32
I simply removed the card and checked the pot. with an ohmeter. The wire feed "touchiness" matches the ohm reading quite closely though. As for what type of curve it has-audio or linear. I don't know. The readings from the meter show it to be neither.
Parent - - By dee (***) Date 09-10-2002 02:44
the control works on a linear curve; you have it under conrtol
d
Parent - - By bzzzzzzzzzz (**) Date 09-10-2002 03:03
What do you think the odds are this is the main problem with the machine? I'll bet the new card is at least $30.00 from Sears parts. Hate to buy it and find out still no good.
Parent - - By billvanderhoof (****) Date 09-10-2002 04:56
Very likely to be your problem. You can probably just repair the board. Use a small grounded soldering iron. Radio Shack sells a cheap one that will work fine. Remove the pot from the board. If you don't have experience working on circuit boards just cut the leads on the pot then heat each stub and remove it with tweezers or needle noses. clear the solder out of the hole while it is still hot by blowing thru it. Measure the resistance between the two outside leads on the pot when you get it out. Buy a pot as close to that value as you can. Standard ones only come in a limited number of values which are rather far apart so it will be hard to be wrong. Get one that will fit back in the same spot. It is most likely linear taper but even the wrong taper pot will make your machine work much better. There may be numbers on the removed pot that will help to confirm your findings. Solder the new pot back where the old one was. Let the iron get nice and hot before you start. Work quickly- enough heat to get the solder to flow nicely then no more. 63/37 solder is best. After it cools for a minute check that solder hasn't bridged to other traces on the board. If it has remove the bridge (an exacto knife works well). Done.

Digikey has a web catalog where you can look to confirm if values exist, sometimes you can cross over numbers there.

Don't give up on us now you've been working at this for a while and you are close.

Bill
Parent - - By bzzzzzzzzzz (**) Date 09-10-2002 10:08
Talked to the tech at Century and he spoke of diode replacement. About $40.00. Said arc breaking was classic symtom.
Parent - - By dee (***) Date 09-10-2002 22:20
Bzzz
I concluded you knew enough to do the job when you demonstrated you were aware of the audio curve potentiometers. Dont go to mush on us now, buddy, you have come too far.

In theory you can substitute fixed resistors for the potentiometer's variable resistance, as long as it's within the max and min range of the pot. Why bother to run the risk, though. If your tests can be trusted and the intermittancies occur at the same point on the pot, its a slam dunk. You have found the problem and probably can correct it at component level.

That is, if the pot itself funks out.

If you overheat the circuit traces they will lift from the board; you are undoubtedly aware. You will gain tremendous advantage if it is possible to cut off the stubs from the faulty device, preferably with a small shear, and solder the replacement to them. Diagonal cutters or nippers will do, but, by the way, never use them on leads of a good solid state device as the mechanical shock often does internal damage.

It is possible the board is of the multi-layer variety, perhaps unlikely, but possible. Complex circuits such as computer boards today are. They have traces laminated within the board itself, and, of course, its best to play it safe. Moreover, you will put less heat to the board, eliminate the need to remove solder and create bridges or leave drops that can short later, and of course, not be dissappointed to find a multi layer issue at hand. Of course, if its obviously a simple board, the worst that can happen is you ugly it up and shunt accross the lifted traces with bits of wire or wind up buying a new one as they intended anyway.

If the board has been properly identified as a simple one or two sided type and you do choose to remove the component do so as previously advised by Mr Vanderhoof. However, a fixture to hold the board (a vise of some sort) is a big help.

There are techniques which leave the hole clear of solder without removal and not needing much, if any, clean-up. Solder is drawn to the heat, but although I can work NiCd solder tabs and diode or transistor leads effectively, the size I imagine this potentiometer to be is very difficult to work. I presume, and suggest, you will wick the solder first before removal. From decades of experience I prefer to use an appropriate sized drill in a pin vise and a very light touch to drill out any solder clogging the hole or slot starting from the open side of the hole; slots take a couple of drill holes to clear and I use the same bit as a file or reamer... dont try to push it through the hole, let it cut- the solder is generally softer than the glass filling the epoxy or phenolic board-, and if filing with it, cut on the return stroke or push from the trace side, as pushing force from beneath the foil from the component side can lift the foil from the board.
Some boards, particularly those made by Phillips, seem to loose their traces if you look at them while thinking about heat; they can be very sensitive to heat although they are mechanically durable.

There should be no swearing and your comments should fall far short of blasphemy. In fact, anticipate smooth progress.

It is doubtful you will find silver bearing solder in use here; this isnt a test instrument, but I have seen it. I would add to Mr Vanderhoof's excellent advice that the thinnest solder melts with the least heat. 60/40 rosin core .032" diameter solder can be used successfully on nearly all standard electronics repair unless factory specificifications require a different alloy such as silver- I would, however, tend to agree; Bill's alloy is the best choice here if you can get it.

Before you devote too much energy to the repair, find out the cost of the replacement board. I have been impressed by the reasonable cost of a small percentage of Sears repair parts and you may have a pleasant surprise.

Best luck
d

Parent - By bzzzzzzzzzz (**) Date 09-10-2002 23:46
The pot. is out of the board. I just heated it and used desoldering braid to remove the solder. Now I am not so convinced it is faulty. I should have realized that ohmeters themselves are not linear in movement. What appeared to be zero movement was when the needle was going past the high ohm markings. ( they are much closer together). I also spoke with the Century rep and he pointed toward faulty diodes. ($40.00) He said it was not uncommon in a machine of this type and age. Also said it often manisfested iself with erratic arc. (AC leaking into the circut or something) But he ALSO agreed that a faulty wire drive circut card could also cause similar problems. I think I'll fill the airspace inside the machine with concrete, allow to cure, attach rope. What an anchor!! Actually I'll call Sears parts and see what both of them cost and go from there.
Parent - - By bzzzzzzzzzz (**) Date 09-11-2002 21:42
new pot. put in circut board- little difference in arc stability. I put in a 50k and I believe the other was 100k. It still tunes in ok, but looses arc for no apparent reason. The tech said look into replacing the rectifier(diodes), but I'm not too thrilled with that idea. $85.00.
Parent - - By dee (***) Date 09-12-2002 01:24
Bzzz
That's bad news. On the positive side, nothing can be said to be a total loss... at worst it can be used for educational purposes as a horrible example. You gained a valuable education at a bargain rate.

Did you price Sears parts for the board? What do the diodes cost themselves? Semiconductors are sold all over the internet. I dont have any idea how you can test them; high power diodes from microwave gear required special equipment.

There is no way for us [me] to know if the diodes, or in fact the board, is at fault or not. I cannot advise you on power supply issues; they are beyond my scope. With the closest stuff I work with the symptom tends towards bad capacitors, but they aint nuthin like welders. Does your tech test the circuitry or does he let you pay and pray?

I can do no more than wish you luck and perhaps recommend the power of prayer.

You might focus on one of the other things that affect your arc and eliminate IT as the trouble if you have not already. I am not aware that you have verified the gas delivery at the nozzle.
Non-invasive procedures should be attempted before surgery.

Many regulators put out a high pressure burst which tapers off after a second or three, sometimes outputs are simply irregular because they are faulty... I feel terrible about the trouble you have already had and would hate to feel worse if your guess that it was electronic-based was also wrong and winds up traced to your gas choking up.
Remember that your weld parameters will vary according to the ionization potential and associated characteristics of the atmosphere surrounding the arc; if it is inconsistant, so will be the arc.

Good luck
d
Parent - - By bzzzzzzzzzz (**) Date 09-12-2002 01:53
I believe the diodes are part of an assembly. The tech. advised me per phone so it's definitely pay and pray. It seems to work ok on the high setting with thin(.024) wire though. I would myself not feel at ease substituting parts in the power supply itself. I may just put some flux core in and see if it runs that ok. If so it may just be sold as is. For a reasonable price it's an ok welder. Really did teach me a few things about mig weldiing. And I do mean a few! I may look at a small 220v unit such as 175 amp. As for the gas flow, I would be surprised if it is erratic. I have a flowmeter and it seems to work just fine. I keep it set aroung 15 - 20 cu.ft./hr. How much could the liner effect this situation. I took it out and cleaned it at work with high pressure and solvent. But it is old looking. It was longer than the manual recommends so I cut it and reinstalled it. I just don't want to doctor a dead horse here. Thank you for the advice, this will be my last post on this matter unless a true revelation occurs.
Parent - - By dee (***) Date 09-13-2002 17:40
Bzzz
You need to talk to a real technician, not a salesman with a soldering iron. Today they may be called engineers. A technician who has no means of testing prior to a repair, even if by some means of substitution, will get no respect from me.

YOU do not substitute the part, the manufacturers cross reference and component distributors make the substitution according to the characteristics of the component... the specs are matched.

If it works OK on high why not use it. Go ahead and try a backing if necessary.

The little "T" handle on your regulator is very easy to turn: double the flow to 40 and see what happens... stop back 1/2 way between the two and note what happens. It's gotta be a $1.00 investment in gas to experiment. Whaddayagot to loose?

In new welders, hold out for 250 amp or larger; you will benefit.

My final word, Bzzzz, and speaking as friendly as possible, I believe the most serious problem you are facing is interpreting your own observations. There is probably little, other than experience, that can help. You have to persist and critique your own mistakes to learn from them. Also, it is necessary to build upon known quantities... if that welder does FC OK what's different between that, and this application... it seems you need to establish a base-line which is known good, be it gas, control-pot characteristics, or performance in low or perhaps high range. To complicate things, filler wire has been known to be bad as have gas mixes as well. If you have a buddy who welds perhaps you can try to swap some consumables to see on his rig at similar parameters.
My, in fact our, problem with advice for you is I really dont know what all might be going on. I may have mentioned my new Miller was making me go nuts in a similar way and I know your pain. Good luck.

sincerely
d
Parent - - By bzzzzzzzzzz (**) Date 09-14-2002 21:56
well things have taken a turn for the worse now. the thing won't hold an arc at all with gas shielded wire. Lots of sparks ,but just blobs of weldment laying on top of the surface with zero fusion. High or low power it just does not arc. It acts as if no gas is getting to it. I have an adjustable flowmeter now so I can see what the flow is doing at the tank end. I feel plenty of gas coming out the gun nozzle. I have tried all kinds of flow rates. The unit works perfect with flux core on high or low. good steady arc. decent penetration. no intermitent arc. i am wondering if there is some truth to the bad diode conclusion. Yes I am switching the polarity from fluxcore to gas wire. Maybe the arc with fluxcore is more tolerant to less than perfect rectifying of the ac voltage than with gas shielded wire? I did stress to the tech at century that fluxcore worked just fine. That's when he talked of diode failure. I will go to the gas supplier Mon. and have him check the gas tank for problems. I'll just bring my welder with me and check if right there. Could a bad tank work ok for awhile, then start delivering faulty mix? The tank is still almost full ( 3/4 or so). The mix is C-25.
Parent - - By dee (***) Date 09-15-2002 00:32
Bzzz
Sorry but at this point I cannot be of much help. Odds are that the odds are against any solution over the telephone or internet. That is not to cast any doubt on the Century tech's opinion. He may very well be right, but I cannot repair equipment under his terms and I have a hard time recommending them; my alternative would be to shop around for another repair facility.

Also, be advised yet again that I have no expertise on repair of weld power supplies.

If your supplier has the facility and inclination to try it out himself it should be a tremendous asset. Bringing a piece of steel?

I did not realize you had a fixed flow regulator.
Bzzz, please, dont just do what I or others suggest but think about it and see if it fits your situation. I have various nozzles which work best at different flow rates; I also have a different welder and am unfamiliar with yours. I forgot there were fixed types in the world.
If you find yourself stuck with that flowmeter email me and I may be able to give it a home. I feel responsible.

Hope all goes well
d
Parent - By bzzzzzzzzzz (**) Date 09-15-2002 03:09
not a fixed flow regulator. a victor flowmeter.(ball type) You're right though I need to go to the supplier and discuss it with them. I'll bet he's gonna show me a welder before I leave. thanks for the suggestions though!
Parent - By billvanderhoof (****) Date 09-15-2002 05:01
The diode is probably dead now- that is a good thing- a diode should have a very small resistance in one direction and a very large resistance in the other you can test with a normal ohmmeter- usually they blow to open- infinite resistance both ways.

Perhaps you can get a service manual from century. It should have debugging procedures that will get you right to the problem.

Luck to you

Bill
Parent - By billvanderhoof (****) Date 09-12-2002 05:15
The rectifiers are probably stud mounted things on heat sinks with one wire attached to the top. Could be two or four of them. Might just be one device with 4 wires on it. Get the numbers (could be two different ones, one anode to case, one cathode to case). Look them up on digikey site. If you get hits then century hasn't put on there own numbers and you are in. Guessing at what you need in a super conservative way came to less than 20 bucks.

Do you have circuit diagram?

Bill
Up Topic Welding Industry / General Welding Discussion / got them watertight , but what a hassle!

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