Wire feed problem.

[rmjsugwas]

i am finding it difficult to sort out a wire feed problem. i am welding 7mm plate to some 10mm plate however after welding for about 10cm the wire feed starts to play up and not feed well. i have a Murex 2x2 roller wire feed unit.

i have checked the liner in the gun and that seems fine (not broken anywhere).
the drive rollers seem to work ok, but can only check when not welding (cos i am on my tod).
i have changed the tip.

i only have an air coolled torch and it does all get very hot while welding. i am running 1mm wire with a 1.2 tip to over come any problem that may occur from the tip getting hot.

is it a heat problem or is my drive motor and gear box on the way out.
if it is the drive motor and gear box what sort of money should i expect to pay for a new one?

regards rich.

 

[Welderpaul]

Using a 1.2 tip with 1.0mm wire might be the cause of your problems. However hot the torch gets, you shouldnt need to have a tip size that is mismatched to the wire size.

What size torch are you using - You will probably fry an air cooled MB25 if your doing plenty of welding at those amps/volts.

Remove the tip and check that the wire feeds ok (Dont let the wire earth itself). If the feed is jerky, it could be a knackered liner or badly wound wire. Why do you suspect the drive motor?

 

[Tino]

I doubt its the motor or gear box, though it is possible. Before looking at the unlikely, expensive parts, try replacing the liner. It can look fine on the outside but could be worn or getting clogged with dust and dirt from the wire. New liner, new 1mm tip, set the pressure on the rollers (check they are 1mm rolls), and check there isn't to much drag on the wire holder (brake) and I'd bet it'll run like new.

 

[rmjsugwas]

right cheers lads,
new liner it is first thing in the morning.
i was welding with a 1mm tip but just seemed to be chewing through them. is this because of the constant high heat? 230- 250amps.
would a water cooled unit prevent this happening?

 

[the snooper]

if you have the same problem every 10cm it could well be a bad connecion that is heating up and changing the resistance.
if it was the liner i would expect it to do all the time not after 10cm after all what will change with he liner after 10cm of welding
i would be checking the connections everywhere before spending any cash

 

[Tino]

Personally I think water cooling is unnecessary (just something else to go wrong) there are air cooled torches that can handle a lot more power than that. If the torch is getting to hot it could be as the snooper pointed out bad connections or as welderpaul said the size of the torch. What changes after 10cm of welding?(Apart from things heating up) To be honest I don't know, but I have had the same problem many times and often a new liner and tip has sorted it where a new tip alone hasn't.

 

[rmjsugwas]

talking of bad conections,
my earth clamp gets very hot and has started to melt the rubber lead around it....is this normal?

 

[Tino]

talking of bad conections,
my earth clamp gets very hot and has started to melt the rubber lead around it....is this normal?

It happens. Over time if you are running high amps the copper starts to oxidise with the heat, that increases the resistance and getting hotter the copper oxidises faster increasing the resistance and getting hotter and on it goes . Best to cut it back to clean copper and a fresh clamp or clean the old one. If after you have sorted your torch and made sure every thing else is in order, the running problem persists, try dropping your voltage a little with the same amps. Its a bit of a balancing act, trying to keep the voltage up to reduce spatter but to much cooks the tip.

 

[rmjsugwas]

cheers tino,
will let you know how i get on.