2.4% response rate at hobartwelders

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Of the viewings of my posts at hobbart I had a 2.4% response rate. I think that is pretty low. Maybe you guys can be more helpfulGranted my explaniations and descriptions left much to be desiredI know very little about welding. I have a problem I would like to solve or be presented with convincing arguments why it can not be solved.the problem is the melting of polyurethane sheeting inside a sheetmetal constructed enclosure using welds as a construction/fastening option.Here are the details and a simple list of questions.thanks in advance for any repliesSee doc attachment for detailsI'm using 1.8-1/4" pop rivets to  join these two pieces now but it is impraticle and I would prefer a welded solution.Q. H&S 4500 UNI-SPOTTER STUD WELD GUN -VS- Chicago Electric (Harbour freight stuff)--Quality?I know a Stud Weld is for pulling dents in autobody and not intended as a fastener.How would a stud weld hold up as the actual faster for the two sheetmetal panels? Anyone know how they would compare to say 1/8" pop rivets? sheer stength---cost--etcOk Stud welds are about one second welds--so given that if I'm joining say two 1/16" U shaped sheet metal pieces with polyurethane insulation sheet in the center. 1. will this stuff melt much under the heat of a stud welded in place using the equipment noted above? 2.How much heat can be expected to be generated with different welding techniques? Fire issues?3. Any melting I guess could be ceased by water cooling (quenching) imediately after the fastening? what kind of compromising of the weld strength would occur under this action to say a mig welded continues bead? other welding methods? 4. How about this -- say a 1/8-1/4" layer of fiberglass between the polysheet and the sheet metal . If it were to be seam welded (Mig I guess) would that protect the poly from melting? How much would a single bead 6-8 feet in length cost per weld? Approx? Material only not labor?Another set of basic questions. Someone must know how much heat is generated with the various welding techniques, cost etc...5 Submerging the piece in water just below the seam to be welded. Would it still be possible to weld the piece since the piece is being cooled? Is a MIG weld localized enough that the seam itself will stay hot enough for a bead to form and adhere? Say 1/8 above the surface of the water? And if so will there be extreme heat generated on the surface of the piece, which would cause the poly to melt?Any other fastening ideas? I would like to use a spot weld but the two pieces are long U shaped (channel) pieces of sheetmetal [] with sheet insulation in the center. No way to get behind it with spot welder tongs. I, after using a cry baby tact for getting no responses at the other forum, I received a helpful response as follows"How much strength do you need? Are you concerned about sealing? Can you slide the polyurethane sheet into place after welding? A few well placed tacks or short weld beads may be sufficient. I suggest that you reduce the length of the red piece by a material thickness so that you are making a lap joint."A-1 As much strength as is practicle/cost effective it will need to bear a loadA-2 Sealing is not required but would be nice as a byproduct of the fastening techniqueA-3 No insertion of the polysheet is doable as it will be slightly compressedQ. Will tack welds not melt the polysheet?Thanks for any comments help etc.. Attached Filesfasten5.doc (21.5 KB, 35 views)
Reply:Well maybe 2.4% was great considering the level of engament here so far 0.0%anyone care to answer the more basic questions?
Reply:Zeldadll,I am sorry that you are getting little response however what might have appeared to start out as a simple question turned into an engineering exam that crosses many disciplines. The guys on this site have probably welded everything imaginable amongst themselves.  You're asking for data that needs to be provided by some of the material's OEM, ie, melting points of Polyurethane, metalurgical changes as a result of quenching in water etc.  If you were to give the guys more information as to what you are building and break it down into steps they might be able to help you out.  Spot welding localizes a tremendous amount of heat to melt both panels together so you're probably looking at temperatures up to 1800 F or more depending on the alloy.  I would imagine any of the welding techniques are going to melt, reduce or damage your polyurethane filler.  Is the filler for insulation or is it to create rigidity within the panel sandwich while reducing weight. You're not being specific enough when you say it has to bear a load....that's fairly critical information and if it fails what's at stake.  You might be better off with some kind of honeycomb structure inside the panels that has a higher melting point.  I think seam welding will give you more strength but at the expense of more heat and possibly more damage to your intermal material not too mention cost.I would be suspect of any welding equipment from Harbor Freight however resistance welders may not need to be built as well as MIG, TIG and Stick machines.Let us know what you doing and I'll bet some good ideas will come from this board.Michael
Reply:now im not familiar with this type of welding but ill try to help.1. id assume YES2. the amount of heat isnt going to vary much between different welding proccess', its going to require around 70 amps to weld 1/16th" and its gonna get hot around the weld. i would suggest short beads layed in a manor to minimize excess heat .start on the top left section, then move to the bottom right section, then the top right section, then bottom left, then the middles (if i understand how it is to be assembled). you can also allow the material to cool between passes. what is the fire issue? remove any flammable items in the area, and have a fire extinguisher on hand (ive never needed one, but ALWAYS have a method to extinguish "accidents")3. the melting would take place during the welding, not afterwards. i wouldnt consider this option.4.replace "fiberglass layer" with "block of aluminum" and it may work. as for the cost of welding question check out the following links, they get a little detailed so you should be able to calculate ALL of your details to reach a conclusionhttp://www.weldingdesign.com/323/Glo...e/False/10760/http://www.weldingdesign.com/323/Iss...se/10864/Issue(thank you to Bruce Vernyi for the links in the "cost of welding and fabricating" thread)5.you could weld it in water (could weld it underwater with the right proccess) but its still going to reach such a great temp. directly at the point your welding it will likely melt the poly.how plyable is this poly once its in place, could you slide a spacer the length of the channel (or halfway) to create a gap between the 2 materials? (the gap distance would depend on weld technique, and how much of a load it would need to hold) if you dont need full penetration of the weld it would make things easier for you, but is likely doable with full penetration (although thats gonna be a headache i imagine)
Reply:and as 383 said, more info could be exactly what everyone needs to jump in and tell you exactly what you need to accomplish this (he posted while i was still typing)
Reply:I can't think of a good safe way to weld with the poly in place.  First off, burning that stuff creates pretty noxious fumes that are really bad for your respiratory system.  BTW, see wood in this list.http://www.swdurethane.com/SWDpages/...g_schedule.pdfsee alsohttp://inquirer.philly.com/specials/...fireside30.aspSecondly, I wouldn't get anything like a stud welder from HF (or from anyone else for that matter) anywhere near a puddle of water, much less a dunking booth.  They will have to be in pretty close proximity to accomplish what you are considering.I am not sure if the fiberglass insulation will accomplish what you are considering either.  I really don't know what max temps that stuff is meant to accomodate, but probably it will have to handle somewhere north of 1500-2500 degrees, depending on whether the insulation actually comes in contact with the molten steel.What you are talking about sounds a lot like the way refrigerators are made, except I think they do it the other way around.  First they weld the frame together, then they squirt in the foam in semi-liquid form to fill in the spaces.  Isn't Great Stuff polyurethane foam?  If the container is fairly closed, why is this not an option?Last edited by smithboy; 08-03-2006 at 11:20 PM.Smithboy...if it ain't broke, you ain't tryin'.
Reply:Hey thanks alot all for the attention to the matter383--Nothing like an american made big block yes? I am sorry that you are getting little response however what might have appeared to start out as a simple question turned into an engineering exam that crosses many disciplinesFair enough and I agree with that asessment completelyThe guys on this site have probably welded everything imaginable amongst themselves.Agreed--That is why I'm going to the expertsThis is a small external structure to house an electronics/computer system with thermal/electromagnetic pulse protection and sound dampening propertiesIt would require surving the elements. storms/ high wind/moisture the weight of snow etc.. contructed of panels of 20 or 25 Guage galvanized steel sheet as indicatedmelting points of Polyurethane?approx 200F - 250FIs the filler for insulation or is it to create rigidity within the panel sandwich while reducing weight?Both as it would be somewhat mobile
Reply:Great answersthank you very muchIsn't Great Stuff polyurethane foam? If the container is fairly closed, why is this not an option?This was my first approach which was inadequate as the foam is integral to the structural rigidity and essential for sound dampening and thermal protection---And Oh so expensive!!!  And I had stuff sticking to me for a weekIt seems welding would not be cost effective unless the structure was enlarged to allow for a housing structure separate from the internal requirements. Which greatly increases the cost.Rivets seem the best solution or adhesives which add another cost engineering variable.I can not seem to find any another fastening/joining optionsthanks again for the engagement on this issue
Reply:Thanks LuzRD exactly what I needed! Great links and info
Reply:Thought I'd take you up on your offer to come visit from the other thread.  After reading through, I think I have an idea of what you're trying to do.  Do not attempt to cool the parts with water while you're throwing oodles of amps at them.  Yes, welding can be accomplished underwater with the right process, this aint the right one.  I might suggest the use of copper or aluminum heat sinks adjacent to the weld, as metioned previously in this thread.  We'll work on getting above 2.4%I r 2 a perfessional
Reply:kbnitThanks for taking the time to reply. That may be a doable solution. Any idea how large a sink may need to be for say a tack weld? I could also place a mat of fiberglass around the sink to further disipate to heat maybe. Cost may be an issue though. Too bad I can't get ahold of a shuttle tile or two.
Reply:If you look at the doc attachment I was thinking of a solution much like the steps of an aluminum ladder---You know how they are flared at both ends through the frame---not shure what the technique/hardware is called -----or what flaring tool produces this effect---does anyone know? Or what the additional cost would be chopping up steel tubing to fabricate. Of course with a smaller diameter say 1/4". Or a piece of steel tube flanged/flared at one end---insterted through----then capped with another short flanged/flared piece with the ID of the OD of the first piece pressed on. Is there a name for this type of fastener? Been looking at fastener suppliers but haven't run across any of these. Not sure if anyone can visualize this
Reply:Yes Yes this thread is getting long in the tooth and this post will be the last by me barring any other ideas offered.I can hear you all now --- Yea--Yea-thank GodI think this information may be useful for some of you all. And the later link--cliching ---is a possible approach for me as it is a substitute for welding/typical fasteners."To make an aluminum ladder, manufacturers drill holes in the side rails and then heat the ends of the rungs before inserting them into the holes," says Krajewski. "They then compress each one, so that all along the rails are holes with crumpled metal that fits around the rung ends. That wouldn't be possible without applying heat - the aluminum would break."http://www.gm.com/company/careers/ca...m_forming.htmlClinchingProcess descriptionClinching, or press joining, is a high-speed mechanical fastening technique for point joining of sheet metal, using no consumables. With clinching, the sheets are clamped between a die and a blankholder, see Fig.1 (1). The punch locally pushes the sheets down into the die (2). The sheets are squeezed between the punch and die expelling material sideways (3) forming an interlocking button (4). It is this interlocking button that holds the sheets together. Alternative process variants use a solid circular die or a rectangular punch and die which allows partial shearing of the sheets. Clinching is a fast and simple single-step technique requiring no consumables or pre-drilled holes. http://www.twi.co.uk/j32k/protected/...kschjg001.htmlThanks for all the help!--this is by far the best welding forum on the planet---and I've been to quite a few--- I hope to make use of it once I delve into welding.Regards,Dll