burning back...why?

[Peloquin]

I'm getting done really nice welds, good penetration etc but every now and again the Wire is burning back to the tip and sticking. It is happening either as i start a new weld our as i finish it and take the torch away.
I keep missing it and pulling the trigger, causing the wire to kink by the rollers. I'm wasting loads of wire, of boss noticed he'd moan his nuts off.
Any help explaining why its doing it and how to stop it would be very welcome.
Ive tried turning the line speed up a bit but it still does it. Do i need more speed?
Cheers folks.

 

[Wozzaaah]

Bad tip, partially blocked liner, badly wound wire, pilot error......
If it's birdsnesting at the rollers then your tensioner is too tight, the rollers should slip if the wire stops en route to the tip.
I'm assuming the machine doesn't have a burnback control on the front panel?
What machine are we talking about?

 

[Sub-arc]

^ Yep. Its a Citoarc M308c I think (going from other thread)

Turn back the tension knob on the clapper arm assy to the point where the rolls won't drive the wire. Then tighten the knob so it feeds the wire through. Don't tighten it much further than that.

Burn back at the end of the weld is sometimes related to taking the nozzle away too quickly/too slowly. Experiment with the timing of releasing the trigger and pulling away from the welded piece.

There may be a Burn Back trimming pot on the pcb too (although this would be getting a bit complicated)

The more I think about it, I'd say its a wire feed issue.

 

[Peloquin]

Sub-Arc, yeah, cheers mate. Thats the machine.
Wozz.. I'm suspecting pilot error but will be trying to slacken the rollers off a little.
Unfortunately I couldnt get back on after break so have struggled on. It's happened less if I hold the torch a little further away from the work.
Thanks gents.

 

[Wozzaaah]

How close are you holding the torch to the workpiece?
Tip to workpiece distance should be around 8-10mm.
I'd still check the liner and tip, they're both standard service items.

 

[Peloquin]

I'm about 10mm away, I was a bit closer but not much.
When I started there I noticed the tip was knackered so I went and got a few new ones. I also got a couple of shrouds as the old one was totally shot.
As far as I know the liner has never been replaced so I'll do that this week.
The way I see it, if I'm gonna be the resident welder then I want it as good as possible.
I'll see how it goes tomorrow but I've been tweaking the settings and am happy with the welds I'm getting now.
I'll (you lot will anyway) get it sorted. haha.
Cheers