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Hi,I just join a small company that plan to produce a series of kart model that have already being developed internally on a crude jig. Based on our limited welding experience (i.e. only 20 karts or so already produced but we are no way a professional welding shop) + info found on weldingweb and other websites, here is what we came up with for serial fabrication: To build the jig for the chassis, our plan is to - get a 5x3 plate of ¾ steel laser cut it ,- then CNC drill all the attachment points of our clamps to position them accurately,- then have the plate surface grinded (flatness 0.1mm/m) and bolted to a supporting frame.This reference jig will be used at the beginning and end of the welding process-First we will use one 1 set of clamps to position the tube for the frame and proceed with tack welding . After tack welding, the chassis will be put in other basic jigs to complete the welding of the tubes and brackets except for the stub axle and rear axle holders. -End of process: once all tube and brackets have been weld together, we will put back the chassis on our reference jig table in an unconstrained state . The clamps we will use will be taller than those used for tack welding so the chassis sits a bit higher and does not bump into the clamps used for tack welding. We will then weld the rear axle support and stub axle support. The idea is that by welding those supports at the very end, we can make sure the wheels are properly aligned & on the same plane even if the rest of the chassis is a bit twisted/not perfect. Although expensive, we chose this setup has we want to make it a straightforward process to duplicate our welding process (i.e. built another copy of our jig) and accurately mirror any design change we might make in our 3D computer model. Since we have limited experience/mistake are costly ; ) , I would welcome any advice experienced welders may on the below points:#1 : PLATE THICKNESS : Would ½ or ¾ thickness for our steel plate be strong enough? (we plan to to use basic construction steel SM50 or SS400). The guys we contacted use face milling said that if we use less than 18mm thick (for example ½ ~12.7mm), the plate may flex during milling and spring back thus ending up being not flat. #2 PLATE GRINDING and FIXTURE: Current plan is to have our 5x3' plate surface milled on both sides( Blanchard grinding is apparently not available in our area of the world ) and then bolted/resting on 6 attachment points/shims located ~2.5 apart from each other. This mean the top plate will only rest on those 6 points. Do you think we risk having our steel plate sagging a bit if it rests only on 6 points? Do you think grinding both face is an overkill/unnecessary expense? #3 SUPPORT FRAME : The support frame is made out of 1/8t thick 2x2 square tube (3mm thick, 50x50mm) made of basic structural steel. ( JIS SS400, similar to A36)) and will have wheels and adjustable feet.Does it sound strong enough, knowing that we will likely have to load it/transport it a few times in our pickup truck (full table with ¾ plate ~ 400 lbl weight)?#4 GENERAL ADVICE : Any suggestions to improve on our planned jig design/welding process i.e. did we miss something obvious??#5 TIG vs. MIG : For this type of job, would you suggest TIG or MIG? In our shop we use TIG but the company to which we will outsource the fabrication can use either TIG or MIG.#6 COOL CLAMP DESIGN : I put some pics of the clamps we plan to use to lock our tubes in place. Any better/cheaper design you would suggest? #7 RUST PROTECTIONSome recommended touse oil,WD40 or PAM for spatter and rust protection. Are there any other more resistant ways to do it as our table may have to cope with very humid environment and be stored unused for several weeks at a time? Would hot black oxide coating be a solution? Only issue I see with black oxide coating is that it means that during coating you have to expose steel plate to 140C ~280F. Would that heat deform/mess up the flatness of our steel plate?Thanks for any piece of advice you may have. I ll try to post a few pictures below.GKReference documents:http://weldingweb.com/vbb/showthread.php...ight=blanchard
Reply:Do you guys have someone who knows how to weld doing this I see alot of liability in learning to weld on a motorized product someone's kid is gonna ride on350P 30A spool gun cut master 51 syncro 250 other stuff " take a dog off the street and make him prosper and he will not bite you sad the same cannot be said for man" i didnt use punctuation just to piss you off
Reply:Oops, just noticed my previous post was quite long. Here are some pictures to make it more explicitOur old jig to tack weld : Some rough sketch of the project for our new jig to tack weld (in blue, some of the clamps):sketch detail for our new clamp The support frame for our new jig (the 3/4" steel plate will rest on top)The jig used to finish welding of the frame after tubes have allready been tack weldedThe jig to position and weld our brackets and platesSome interesting web example of what other are doing for clamps-jig (web source : alibaba). We were concerned about price/clamping strength of these clamps so we did not use this solution although they probably would allow for slightly faster setup time
Reply:Originally Posted by umahunterDo you guys have someone who knows how to weld doing this I see alot of liability in learning to weld on a motorized product someone's kid is gonna ride on
Reply:I am wondering why you are going to all the trouble of surfacing the plate. Only the support pads need to be levelled. I suggest welding pads at all the critical locations. Weld with SMALL fillets so that you don't twist the plate too much. Set the plate on your milling machine/planer and machine the pads to the correct height and with CNC locate and drill the mounting holes. When setting the plate on the bed do not clamp to pull it down flat. Set it on and shim then clamp. You avoid all the extra machining costs. There is nothing wrong with the old jig if it was made of heavier material and the supports were machined after welding. Your new jig plate could be set on a heavy tube table ... say a frame made of 4 x 4 x 3/8 wall. In the same way that the plate was set on the machine table set the jig plate on the frame, shim then bolt/clamp to tube frame.
Reply:Originally Posted by GoKartOops, just noticed my previous post was quite long. Here are some pictures to make it more explicitOur old jig to tack weld : Some rough sketch of the project for our new jig to tack weld (in blue, some of the clamps):sketch detail for our new clamp The support frame for our new jig (the 3/4" steel plate will rest on top)The jig used to finish welding of the frame after tubes have allready been tack weldedThe jig to position and weld our brackets and platesSome interesting web example of what other are doing for clamps-jig (web source : alibaba). We were concerned about price/clamping strength of these clamps so we did not use this solution although they probably would allow for slightly faster setup time
Reply:Neat tableWhen I get some time I want to examine the jig set up.Dave ReberWadsworth Ohio
Reply:I recent saw some really cool jigs for welding up tubular steel frames, somewhat similar to a go-kart at a fabrication shop. I can't mention the name of the company, nor was I allowed to take pictures.However.Their jigs were made by using a grid pattern of 3/16" plate standing on edge. The plates were laser cut with notches so the whole thing would lock together and maintain flatness and square. They were then tack welded at all the intersections to keep distortion minimal, with most of the structural strength coming from the super tight tolerances at the interlocking notches. In addition to the notches for assembly, each plate was cut with the exact cross sectional view of the parts at that particular location, so the jig provided perfect 3-D alignment of every part, every time. Each jig was mounted on a rotisserie to allow FULL IN-POSITION welding of the entire product before removing it from the jig.It's kind of hard to describe in just words, I guess... however it seemed to be a SUPER economical way to build accurate, reproducable jigs. You appear to have a good handle on CAD, so it would be pretty easy for you to take your go-kart frame drawing, lay out a couple dozen cross-sectional views, and have the plates cut. Laser, water jet, or a real good plasma table would provide the tolerances needed.This method is quick, because you can design the jig DIRECTLY from a CAD drawing of your part, and it doesn't require hours of painstaking alignment and adjustment like a manually built system.You didn't build that.'85 Miller AEAD-200LE
Reply:Originally Posted by lotechmanI am wondering why you are going to all the trouble of surfacing the plate. Only the support pads need to be levelled. I suggest welding pads at all the critical locations. Weld with SMALL fillets so that you don't twist the plate too much. Set the plate on your milling machine/planer and machine the pads to the correct height and with CNC locate and drill the mounting holes. When setting the plate on the bed do not clamp to pull it down flat. Set it on and shim then clamp. You avoid all the extra machining costs. There is nothing wrong with the old jig if it was made of heavier material and the supports were machined after welding. Your new jig plate could be set on a heavy tube table ... say a frame made of 4 x 4 x 3/8 wall. In the same way that the plate was set on the machine table set the jig plate on the frame, shim then bolt/clamp to tube frame.
Reply:Originally Posted by anickodeI recent saw some really cool jigs for welding up tubular steel frames, somewhat similar to a go-kart at a fabrication shop. I can't mention the name of the company, nor was I allowed to take pictures.However.Their jigs were made by using a grid pattern of 3/16" plate standing on edge. The plates were laser cut with notches so the whole thing would lock together and maintain flatness and square. They were then tack welded at all the intersections to keep distortion minimal, with most of the structural strength coming from the super tight tolerances at the interlocking notches. In addition to the notches for assembly, each plate was cut with the exact cross sectional view of the parts at that particular location, so the jig provided perfect 3-D alignment of every part, every time. Each jig was mounted on a rotisserie to allow FULL IN-POSITION welding of the entire product before removing it from the jig.It's kind of hard to describe in just words, I guess... however it seemed to be a SUPER economical way to build accurate, reproducable jigs. You appear to have a good handle on CAD, so it would be pretty easy for you to take your go-kart frame drawing, lay out a couple dozen cross-sectional views, and have the plates cut. Laser, water jet, or a real good plasma table would provide the tolerances needed.This method is quick, because you can design the jig DIRECTLY from a CAD drawing of your part, and it doesn't require hours of painstaking alignment and adjustment like a manually built system.
Reply:Originally Posted by GoKartThanks. We will follow up on the idea to weld first and CNC machine afterwards.For the support table, i noticed that you mentioned about using 4x4 with 3/8 wall. The support table we already started to built is 2x2 with 1/8 wall (actually 50x50mm with 3mm thick wall). Would you think that this type of frame will be too weak to support our ~240 lbl jig plate ? the support table we are building :
Reply:Originally Posted by anickodeI recent saw some really cool jigs for welding up tubular steel frames, somewhat similar to a go-kart at a fabrication shop....Their jigs were made by using a grid pattern of 3/16" plate standing on edge. The plates were laser cut with notches so the whole thing would lock together and maintain flatness and square. They were then tack welded at all the intersections to keep distortion minimal, with most of the structural strength coming from the super tight tolerances at the interlocking notches. In addition to the notches for assembly, each plate was cut with the exact cross sectional view of the parts at that particular location, so the jig provided perfect 3-D alignment of every part, every time. Each jig was mounted on a rotisserie to allow FULL IN-POSITION welding of the entire product before removing it from the jig....This method is quick, because you can design the jig DIRECTLY from a CAD drawing of your part, and it doesn't require hours of painstaking alignment and adjustment like a manually built system.
Reply:Originally Posted by lotechmanYou are after rigidity on a welding fixture. Strength is not a consideration. You want zero flexing. In my opinion the blue thing you have for the plate is too light.It is barely enough for the weight of a heavy plate you are proposing. I think my 4x4 is on the heavy side being overly cautious. The blue frame is made up of square bays. At the very least place some diagonals in so that it cannot Lozenge.
Reply:Rigidity goes more than one direction. When you are welding, it's going to be putting forces on that table in all different directions, not just down.You didn't build that.'85 Miller AEAD-200LE |
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发表于 2021-8-31 23:15:02