|
|
Hey guys I am going to be building a new table for in the shop. I will be picking up materials some time this week. I will be putting together a 5 sided table using 1 1/4" plate with ribs under the table every 1 ft. on center. It will be 5' x 3' and the sides will be 6" tall. I will be drilling and tapping holes on 2" centers through out whole table. The table will be blanchard ground and squared after it is built. I will be welding whole thing together rather then bolting just to make sure after it is ground that it will not move. Do you think that with out some sort of stress relieving that over time the stresses from the welds may move the table out of wack after it has been ground? It will be quite the project to build and don't want any issues after it is finished. I know the bluco tables are welded together but not sure what they do after that besides the grinding. ThanksMillermatic 252Lincoln 175 plusTA 185tswTA 161stlhypertherm pmax 45Victor torchHenrob torchAn S10 for each day of the week
Reply:Once welding is complete, the stresses are locked in. It takes a form of stress relief to relieve them. You'd be amazed at how much stress there is in a weldment in addition to the work it was designed to do. The structure is resisting internal stresses while resisting load stresses.Sometimes stress is used to advantage in cambers etc.I don't believe you'll have a problem. Any warping from the welds will be ground out of the table top. Short welds, welding at different positions on the frame alternately, and allowing for cooling time between welds, should keep warping to a minimum. Preheating also helps to alleviate some distortion."Any day above ground is a good day"http://www.farmersamm.com/
Reply:You could bake it in an oven to relieve the stress. I do not know what that temperature is though. I would think red hot, for some duration and then a slow cool down. If you are doing something super critical the structure of your table might be more important than anything. In other words if the structure of your table causes it to warp or bend upon heating and cooling that may be far more movement then any weld relief from hammering or a sudden shock to the table. The car companies noted that their automobiles grew 1/8" from winter to summer. Imagine that your tables ribs grow at a different rate then your table top. Or that the sides grow at a different rate then you table top. That will cause a belly or bow to occur. They use large granite stones to create certain fixtures, and for chip manufacturing for this reason. Because stones do not seem to change shape or bend upon heating and cooling as much as metal does. Sincerely, William McCormick
Reply:Heat soaking would be too inconvenient for such a large piece. BIG OVENI really feel that the stresses won't matter at all. The main thing is to keep distortion to a minimum so the top can be successfully ground without taking off a ton of material.I've seen the granite used for precision machining layout too. Nice stable stuffBESIDES......THE WELDING DONE TO THE STUFF HE'S GONNA JIG UP ON THE TABLE WILL WARP TO KINGDOM COME ANYWAYI don't care how flat a table top is, or how restrained the joints are, there will always be some distortion when welding anything. And sometimes overly restrained joints crack because there's nowhere for the stress to goAh, the wonderful world of metal"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Well thanks guys for the responses. They do have units big enough to stress relieve the table. The joint prep on the bracing and table pieces will be nice and tight. I guess if I do small stringers rather than big fat beads it should be fine. Nothing I build on it should ever transfer enough heat to the table or supports to cause it to move. Just worried about with fixtures on it holding a weldment tight that the piece being welded could potentially move the table if there are some extra stresses within the table that could make it want to move easier then if bolted together. Easier to weld together then to bolt and use alignment pins or something.Millermatic 252Lincoln 175 plusTA 185tswTA 161stlhypertherm pmax 45Victor torchHenrob torchAn S10 for each day of the week
Reply:Maybe you can adopt vibratory stress relieving to reduce & redistribute welding stress |
|
发表于 2021-9-1 00:40:41