oxford mig not working properly

[bigtip]

Hi all, I used the mig a few days ago when it was very cold and did a little bit. It seemed to be behaving oddly but i managed to complete the task which was just welding 2 short lengths of dexion upright together to help tidy up the workshop with another set of shelves. I assumed it was just the cold that was making it behave weirdly but yesterday it did the same though the weather was not that cold. The symptoms are that it doesn't transfer the weld to the job, the nozzle gets a big glob of metal on it or the metal drops to the ground and the sound is very quiet. I managed to get the dexion welded as i was in the flat position but yesterday trying to weld uphill or downhill was impossible.

Fitted new tip and nozzle and I have followed a few ideas that i have read about fault finding and tested the voltage which is about 20v on a low setting and 30v on a high setting, open circuit. There is nothing obviously wrong looking inside the machine, the wire feed seems to work fine etc.

please help with any suggestions of what to test next and what to expect.

thanks,

john.

 

[daleyd]

What your welding isn't galvanised is it?

 

[Tom Orrow L]

So, is the machine actually welding or is it just not penetrating the metal?
Have you tried the obvious things like earth quality, maybe a different torch, gas etc..

 

[bigtip]

Dont have another torch to try. Earth was clean both times.

it seems as if the weld metal is repelled from the job. Like i said (in my edit) it got the dexion welded only because it was in the flat position but welding uphill and downhill (had no choice) it just dropped blobs of weld on the floor. Even the dexion weld was poor but it did the job for a few shelves if you know what i mean.

no not galvanised.

 

[rikrobson]

Sounds like you need to turn it up a bit. What thickness is the dexion ? 2 mm?
What welder are you using?have you tried to run a bead on some scrap?

 

[bigtip]

Oxford 200 migmaker is the machine i am using.

It is mild steel to mild steel, settings fairly correct, moved up a bit, moved up a lot, moved down a bit, a lot. Tip replaced, nozzle replaced.
Maybe my description is a bit unclear but I've never found 'turning it up' stops gobs of weld forming and then dropping. I've welded the exact same materials many times before.
I am pretty sure it is a problem with the machine so what could be wrong with it?

 

[500e]

Dexion use bolts to join it, not the best of metal to start with

 

[mike 109444]

As the Oxford has Capacitors I assume (as a big thing is made of it in comparison with the portamig !) check the connections to the capacitors. Not sure if they have spade connection or screw terminals or are on a buzz bar but I had much same fault on my very old Clarke machine that had one LARGER capacitor (can of peas size!) and the rivet of the spade connection on top the cap had worked loose and was giving intermittent good then poor connection and poor penetration.

 

[Tom Orrow L]

Oxford 200 migmaker is the machine i am using.

It is mild steel to mild steel, settings fairly correct, moved up a bit, moved up a lot, moved down a bit, a lot. Tip replaced, nozzle replaced.
Maybe my description is a bit unclear but I've never found 'turning it up' stops gobs of weld forming and then dropping. I've welded the exact same materials many times before.
I am pretty sure it is a problem with the machine so what could be wrong with it?

Could give les a call at Technical Arc & see what he reckons?
Are the globs just kind of sitting on top of the metal that they drop on?

 

[mike 109444]

Like this

 

[bigtip]

Thanks for the last comments there, will try and check the caps tomorrow. I can see its got two so maybe one is ******** and the outgoing polarity is the wrong way round or something. How could i check them? (got no capacitor setting on my meter).

yes good point, dexion can be bolted but that's pretty boring.

 

[mike 109444]

Caps can dry out over time BUT I would assume your machine is only <10 years old so should not be dried out. Before you touch the caps, unplug machine and using a screwdriver short across the two terminals of the caps. Reason they can hold a charge which will need discharging before playing with terminals. There SHOULD be a "bleed" resistor connected to them that is designed to "bleed off" this charge BUT that can some times fail hence the screwdriver to be sure.

 

[Rosepuds]

Shorting the caps if there charged would create a very large spark, probably lose the end of the screw driver and the end of the cap terminal. just touch the mig wire poking out of the end of the torch down to the work piece. If the caps have failed there is usually a sign of them leaking or swelling.
If the weld is not penetrating the metal the fault is usually a poor connection in the welding circuit. Check all welding cables are tight , the torch is tight on the euro connector, earth return is tight, connection inside the machine and tight, etc.
I am not familular with dexion. If there is any resistance in the material (coating), It would not help with weld penetration. Try welding some normal mild steel .

 

[rikrobson]

The capacitors are there to smooth out the current. If its blobbing then its sounds like the weld pool is not wet enough. what gas and flow rate?

 

[bigtip]

I was welding ms when decided i definitely had problem with the machine. Machine is about 3 years old.
will check all connections later today.

 

[Wendelspanswick]

What happens when you turn the wire speed right up, does it push the torch away from the material?

 

[mike 109444]

See post 5 line 2
http://www.mig-welding.co.uk/forum/threads/smoothing.22288/#post-244335

 

[bigtip]

Thanks for the link, that is very jnteresting and i have saved it to read properly later.

tried the welder yesterday and it's working normally again so i've put the side cover back on. Everything seemed solid in the there, nothing loose, nothing looking burned etc. but i did wonder why it had two transformers but reading that thread i now gather that that is an inductor. If anyone has info i would love to know what is the procedure for fault finding, what to test and what values to expect, if/when this happens again.

john.

 

[mike 109444]

Thanks for the link, that is very jnteresting and i have saved it to read properly later.

tried the welder yesterday and it's working normally again so i've put the side cover back on. Everything seemed solid in the there, nothing loose, nothing looking burned etc. but i did wonder why it had two transformers but reading that thread i now gather that that is an inductor. If anyone has info i would love to know what is the procedure for fault finding, what to test and what values to expect, if/when this happens again.

john.

If it happens again (which I think it will!) Then UNPLUG welder and remove cover, then feel along any joints and bolted connectors. Reason : the cables inside will get warm in use and where there is a connection if it is a poor connection this will cause a resistance which will make that connection hotter indicating a problem. If you have previously checked through the connections and believe they are ok then I still think you may have an issue with the caps and or there connections. As I said before I had same symptoms on one of my welders which was down to the cap connection.

 

[bigtip]

Thanks for the info Mike,. The welder was stone cold when i checked it as it was a day later when i got round to taking off the side etc but next time, (hope not!) I will follow your directions.