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Thread: Need help - Fixed gantry design

  1. #25
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    Default Re: Need help - Fixed gantry design

    Maybe it's time I got a welder then. I did do a short course while I was in the states last year and it's a skill I would like to learn one day.
    Any gassless Mig welders you recommend?

    Also with the flat bar, is there any particular grade I should use?



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    Default Re: Need help - Fixed gantry design

    Hi.....I'd buy a welder local......Bunnings?....... not on EBAY, even if the price is cheaper....the hassle to get any service when things go wrong is too much and most if not all of them are all circuit boards now with more bells and whistles than you can handle.

    I suggested a Mig as it's pretty universal for light stuff in the cheaper home type models.......probably in the $200 to $300 price range and as simple as you can get ....less to go wrong etc......if you want to get really serious, perhaps a grand will get you there.

    If you want to get ambitious, a stick welder is simple and hard to beat...... 120 amps should see you OK.....plus the rods are quite cheap too, but you need practice to get good corner welds, but after a month you're an expert....almost.

    I welded part time for 3 years after retrenchment and finally retirement, but the plasma welder became my personal main line choice for metal melting......long story.

    I think Bunnings has an Argon gas bottle plan similar to the Propane bottle swap over plan, so if you want to go gas welding, as it's cheaper on the wire.....that's an option.....a lot depends on your budget, but a welder opens all sorts of doors.

    With the flat bar for the rail mounts.....use hot rolled mild steel NOT the cold rolled bright mild steel.......hot rolled has the black rough finish from the hot rolling and is relatively docile when it comes to cutting and welding it.

    Cold rolled has a bright shiny finish and with the rolled in stresses will warp if you look at it too hard.
    Ian.



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    Default Re: Need help - Fixed gantry design

    Quote Originally Posted by boltzzz View Post
    Maybe it's time I got a welder then. I did do a short course while I was in the states last year and it's a skill I would like to learn one day.
    It's not hard to do the basic stuff. Thick walled steel material like this, a few hours practice, watch some instructional videos on youtube, and you should be OK.

    The hard stuff is to do is thin walled. Also it could take a while until you're dropping dimes that look really good. I wouldn't say my welding looks great, but I manage to get the job done. I find it really depends on the rods I'm using.

    I bought an old used miller stick welder from kijiji for $200. It was a great deal. The leads that came with it were worth more than I paid and it came with a couple welding helmets and some rods too. I would look around for something used in local classifieds. You'd want a full face helmet. Forget about the goggles unless you don't mind getting a bad sunburn all over your face. Also, with a MIG, you can have wire feed problems or other issues from things wearing out. Don't get me wrong, I wish I had a nice MIG, but, an older used good brand stick welder like a miller or lincoln, well, they are pretty much indestructible.

    You can't do this in an apartment. Sparks and fumes will fly everywhere. Also, I say forget about any welder that is 110-120Volts. It just won't have the juice to do a good job. I plug my 220V 240V welder into the stove outlet and run a long heavy gauge 220V extension cord outside.

    With a stick welder, the type of rod used, and the current setting make a huge difference. Stick welding gets difficult if you need to do any vertical welds. Horizontal welds are much easier. For vertical welds I have used 6011 rod, you need to have the current set just right, and if you get the weld too hot, it will run downwards with gravity. Nothing in the drawings I did requires a vertical weld, because once you have everything tacked in place, the pieces are small enough to move them around / flip them over so you're always welding side to side and not up and down. You can alternate your stiches on different sides to minimize distortion.

    Still, if you had everything cut / drilled / set up, you could do all the welding in a day, so if you're not going to weld after this, well, finding someone to help you for a day who has the tools may be easier than buying all the stuff your self.

    Quote Originally Posted by boltzzz View Post
    Also with the flat bar, is there any particular grade I should use?
    I am using 6" x 3/4" flat bar on my build. I got some pieces from the junk yard for 15 cents a pound. No idea what grade it is. It's nice and flat, and that is important. The thickness means it doesn't distort easily. I would have used half inch if I could have found some. The weight of it does add up quickly. It's heavy stuff, but for me, the total weight is not as important as the ability to move each piece down a flight of stairs into the basement!

    If you buy from a metal merchant, you will want to buy a full length because its cheaper. I'm guessing that's 12 or 24 feet long. That's why I made everything from the same stock in the drawings I did.

    Cold rolled can be flatter than hot rolled. You want to take a straight edge with you to the metal merchant to see how flat the stock is before you buy it.

    I bought some 10" x 0.5" that wasn't flat at all and it took alot of work to make it flat.

    The nice thing about buying from a metal merchant is that they probably have a nice metal cutting bandsaw and can do all your cuts for you nice and square before you even take it away. Cutting big box steel tube nice and square with an angle grinder can be a real pain in the rear, and is time consuming. From what I've seen, they might charge one or two dollars a cut, so it's a great deal to do it that way. Perhaps it's different where you live.

    Also, just to be fair, the design I suggested will be time consuming. Many big holes to be drilled through steel, and alot of smaller holes and tapping, plus making things flat.

    Also, you will need to design the whole thing first with a Z axis to make sure you have enough Z movement and to make sure that your spindle nose will be in the middle of the table movement when assembled. Perhaps you will come up with some ways to change the design and make it better. It was just a suggestion. I think there may still be some ways to make it better / simpler / easier to make than what I have drawn.



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    Default Re: Need help - Fixed gantry design

    Hi Boltz....basic tools for a steel weld project.......100mm angle grinder and a welder........I've seen some people do embroidery like that......one is a putting on tool and the other is a taking off tool......LOL.

    A poor mans drill press......a cordless drill and 1 metre length of wood.......jam the end of the wood against the wall and apply the middle against the back of the drill body.

    One thing with a steel build, if you make a mistake the taking off tool fixes everything and steel can be ground smooth to make it look perfect......try that with aluminium.

    Best of luck, hope to see the full build run on here.

    BTW.....where are you in OZ?
    Ian.



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    Default Re: Need help - Fixed gantry design

    Boltzzz,

    You know, I've been thinking about your original concept of using cut flat aluminum plate. I'm not sure you should give up on it, good to explore options, but I was thinking more about your first idea.

    Have you seen this thread?

    Concrete VMC

    He makes a structure from steel plate that is custom cut and welded. I don't see why you couldn't do that with aluminum. But the difference would be that you would make box structures from the plate and weld them together with ribs here and there as opposed to simply using flat plates.

    Not sure if you could bolt them together, with thick enough plate you could, so you could countersink the cap screws and have enough plate width to drill and tapp holes on the sides of the ribs. You'd need a heck of alot of screws. The gear and skill needed to weld the aluminum is much more than is needed for steel.

    Something to consider. The more I think about it, the more I think it may be feasible. Up to you obviously, we're just here to discuss options and give opinions. I just started thinking that we may have railroaded your first idea too quickly.



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Need help - Fixed gantry design
Need help - Fixed gantry design