Dear friends,could you help me solve the cap nut welding problem?

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my plant wants to manufacture a new products, we want to weld a cap on  a nut,we have a resistance welding machine,we have tried many times, but there are some problems, in the connecting area of the cap and the nut, there is some seam,we think we may set the wrong welding parameter, and the cap's shape is not good enough, could you please give me some advice, thanks in advance, Attached Images
Reply:can anybody help?
Reply:You can buy those already made in the USA, very good qualityBilly
Reply:Can also buy them in Australia, vely cheap, excellent qualityBilly
Reply:let me help you out.they are called acorn nuts.you can get them from herehttp://www.mcmaster.com/#nuts/=1mpa42on the left side of the screen you will see a chart. select the one that says "acorn nut"Last edited by ace4059; 04-27-2009 at 03:17 PM.
Reply:For ordinary acorn nuts, the best quality ones are either forged or turned from hexagonal bar stock, with the threads applied as a second operation. The 'construction' method would be more difficult, give a poorer product and make little sense here.If these need to be a specialty item with a thin cap and extra room inside, the cap could have a flat base (end of the 'U'), fit into an annular groove, and be silver soldered, preferably in an oven with inert atmosphere.Last edited by Oldiron2; 04-27-2009 at 05:14 PM.
Reply:Originally Posted by Oldiron2the best quality ones are either forged or turned from hexagonal bar stock, with the threads applied as a second operation.
Reply:thanks all of you, i really appreciate all your help!
Reply:Hmilyvoid,I dont think you get it. they really Are not welded on the nut. The Pm you sent me, makes it sound like you still want to build these instead of buying them.please tell us what you are wanting these for? do you want to sell them, do you need them for yourself or a certain project, what? I think they are not welded but they are make from a solid piece of metal. take a look at these in the pic. there is no weldshttp://www.chinafasteneronline.com/N...D-CAP-NUTS.jpg
Reply:ok I see what you want them for.you want to make them so your plant in china can sell them as you stated in the first post.you need to look into another method of making them, and not welding them.
Reply:Is this a joke?  I don't see how resistance welding could ever be a viable process.  For one thing, the force might crush the dome.  Then getting a good grip on the dome or a good power transfer is difficult.  Then it might put a burn spot on top of the dome.  Then the weld faying surface will not have a contact area conducive to good welding. Then there will probably be expulsion and burrs to clean if you want a solid weld.  If you do not weld at expulsion you will risk having weak and frail welds. For what these cost, it might be a lot cheaper to just buy them from machined stock.
Reply:Originally Posted by obewanIs this a joke?
Reply:Originally Posted by obewanIs this a joke?  I don't see how resistance welding could ever be a viable process.  For one thing, the force might crush the dome.  Then getting a good grip on the dome or a good power transfer is difficult.  Then it might put a burn spot on top of the dome.  Then the weld faying surface will not have a contact area conducive to good welding. Then there will probably be expulsion and burrs to clean if you want a solid weld.  If you do not weld at expulsion you will risk having weak and frail welds. For what these cost, it might be a lot cheaper to just buy them from machined stock.