Twin Wire SAW Head

By Tino Date 07-10-2007 22:15

I was recently involved in an attempt to upgrade a "standard" K-129 Tiny Twinarc contact nozzle to a K225 "Heavy Duty" twin wire contact nozzle. We wanted the upgrade because the long welds that are being made are burning up the relatively small contact tips in the "standard" contact nozzle. The alternative "heavy duty" nozzle has large copper contacts that are tension loaded onto the wire. We expected that the heavy copper would handle the high heat better and would allow us to frequently re-dress the copper shoe before replacing.

We couldn't get it to work. The Heavy Duty contact nozzle seemed to reduce the robustness of our welding procedure. In other words, we couldn't get it dialed in. The welds were undercut in some places and humped up in others. We were welding 5/16" horizontal fillets with two 5/64" wires and slighlty active flux. We tried using all three wire spacers availabe for the nozzle and adjusted voltage and amperage but we just couldn't get consistency.

We ended up switching back to the lighter duty nozzle. Things worked fine when we switched back. However, we are stuck replacing contact tips too frequently. Even worse is that the tips get so hot that they fuse into the nozzle and we end up replacing the lower assembly of the nozzle on a regular basis.

Any comments or experiences on this subject would be appreciated.

By ssbn727 (*****)

Date 07-10-2007 23:09 Edited 07-10-2007 23:16

Hi Tino and "Weldcome"
If you could elaborate more on the welding parameters; Current, Voltage, wire feed speed, type of flux, etc. Also the type of steel, thickness joint configuration and anything else besides what you already mentioned that would enable many of the participants of this forum to help you find a solution to your dilemma. Btw, did you contact the folks in Hanover, PA about your problem because they're usually the "go-to" guys for ESAB in the US.

I'm not that familiar with the process variant your working with although I've seen it applied successfully on a couple of occasions so, I apologize for not being more helpful. Without the above mentioned data, it's not going to be easy for someone here that really wants to help out. ;)
I look foward to your response. ;)

Respectfully,
Henry

By Tino Date 07-11-2007 11:33

Hi Henry and thanks for the response.

The key to my question has to do with the welding nozzles - in particular a contact assembly with tension loaded contacts. This style has been around for a while. I think MK has (or had) one for aluminum. I've seen it demonstrated too. But I was searching to see if there is any real experience with these types of contact tips.

The welding procedures are typical of the process and application as mentioned. To be more clear than what I wrote previously, we are able to eventually get things dialed in, it's just that the operating window has shrunk too much.

My hunch is that the nozzle is adding another variable. - being the tension and friction of the copper contacts. Maybe the point of contact is varying - added to that maybe the extra friction has mildly affecting feedability.

By Joseph P. Kane (****)

Date 07-10-2007 23:40

Tino
Just a stab at this.
Many years ago, I had a problem with the symptoms you describe with the undercut and then humpy weld profile. I didn't have the problem with the Tiny Twin Arc, but with different single wire heads. It seemed that I had to adjust the wire straighteners when I changed heads. I had NA-5 controlers and was at a loss for an answer to the problem. The Lincoln Rep helped me out in about ten minutes!