Hello, I read your description of the problem that you are encountering regarding the hole or lack of crater fill that you are referring to. I would imagine that you are well aware of all the variables that can be encountered in GMAW welding of aluminum. Some things to consider that are not always paid much attention: are you preheating the parts to be welded if they are of any considerable mass or thickness?, alot of shop owners and those in charge try to forgo this very important step because of the extra time and cost involved, would the material that you are welding possibly be better welded with an Alumi-Mix gas instead of straight Argon?, in my neck of the woods Alumi-Mix is a Helium,Argon gas mixture which is sometimes a much better choice of shielding gas, are the parts that you are welding on clean of cutting fluids, oils, greases, and other types of surface contaminants?, does your welding machine that you are using have a crater fill feature that can be selected?, you said that it was a Miller wire feeder welder with pulse, some but not all of these machines have a selectable crater fill feature, when you said that you ended up with a blackened area near the end of the weld in the crater area, that is usually an indication of a lack of shielding gas or some other form of contamination, you might look at your flow meter settings and also carefully check all of your hose and fitting connections for leaks. Some people make the mistake of thinking that if a little gas is good then a lot of gas is better, a venturi effect can be caused by using incorrect flow rates (ones that are too high) and actually draw air into the weld zone, incorrect tip to nozzle distances and work to nozzle distances can also effect correct shielding. Another comment on the Miller welder that you might be using, it may or not have a post flow feature that can be adjusted to continue the flow of shielding gas after the trigger has been released, be sure that this is properly adjusted and that you are not jerking the gun away from the crater immediately after you have completed the weld, some of the Miller guns have a mechanical gas feature that is a part of the gun and is not an electrically operated solenoid to control the gas flow, if that is the case you will have to train yourself to not completely release it so that it will continue to flow gas for just a few brief moments. One final note, when you come to the end of the weld you might try backing up onto the previous weld area a few strokes before you stop the arc, this will leave any crater away from the edge of the joint where it is more susceptable to starting a crack. Sorry for the lengthy reply but I hope it helps in some way and good luck on figuring out your problem. Regards, aevald
MY aluminum experience is very limited, basically just what I did at school as part of the pre apprenticeship program I took.
The thickest this stuff is getting is 1/4", so I don't think preheating is necessary at all. The aluminum is completely clean. The aluminum is 4043 IIRC, I think that straight argon is fine for that, correct me if I'm wrong please.
If there is a crater fill feature of the welder, I have not seen it. I have been through all of the settings on the welder that I could access, but it might be under a different menu or something. I'll check the manual and see if there is such a feature.
The welder does have a post flow feature, it's set higher than I think it needs to be at around 1.5 seconds. I think we can rule out contamination of the material from sources other than air, as it's only the end of the weld that has this dark crater.
I'm not all that experienced welding aluminum, do I need the shielding nozzle protruding further from the contact tip than I would usually want with steel? I have it at around 1/8" past flush right now.
Cracks aren't really an issue, these frames are very much overbuilt. I'll try playing around with the shielding gas, thanks for hte advice.
Hello again, I'm guessing that you have the new Miller 350P push-pull welding system. Although I don't know if you are using the cobra push-pull gun or a spool gun. My experience with this particular system is that if you would like to activate the crater fill feature it is not readily explained in the book or the manuals for this machine. As I remember working with these you need to go to the selection portion of the welding process that is titled timers (this is the display portion of the screen that allows you to set the run-in, post and pre-flow, etc.)and turn the selector knob until it shows the last display choice on the screen before starting over again, once you are there press the selector button on the left side of the panel one more time, it should read crtr on or crtr off, use the right hand rotary knob to change the selection from one to the other. I'm telling you this from memory so please understand that I may not have this exactly correct. You may need to speak with a Miller tech. person or a knowledgeable technician from your local Miller distributor. I like to run the contact tip flush with the nozzle or up to an 1/8" recess into the nozzle. You said that you are welding on a maximum thickness of 1/4" 4043 material, you may still find that you will get better results with a slight pre-heat, the reason that I'm telling you this is that you will have less of a lump or cold start on the initial start of the weld, many people will increase the initial voltage and wire speed to avoid the cold start or lump but then they will encounter a problem with the weld ending up overly hot on them if they are welding longer seams or multiple passes, in other words the bead will go flat compared to the start and possibly the weld will drop out on the end of a seam or joint where the weld is terminated meaning the crater will not want to fill readily. Hope this helps, aevald
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