Need help - Fixed gantry design

[NIC 77]

The vertical 'columns' are bits of big box tubing side on. They MUST have a flat plate welded across one end - I think that is shown. Otherwise there could be some ringing or vibration.

He could also cut some plywood pieces to fit the tube very snugly and fiberglass or epoxy them in place or something similar to stiffen it up without welding. Obviously, I think welding is the best choice but I disagree on the word "MUST" because there are a few other things that could be done there and still leave room to bolt them down. The welding would only take a few minutes, so in my opinion, it is easier to find someone who has a welder to help out, so I think we agree on that.

I suggest that the Y axis box section should be capped at the ends to also prevent deflection. Trouble is, that makes it hard to get inside for bolts.

I assume you are talking about the gantry when you say Y axis. Because the span is small, ribs are not necessary. However, if he wanted to add ribs, they could be added just past where the bolts go. I welded ribs into my build using a stick welder duct taped to a broom handle. Also the gantry on my build has bolts at the ends, in the tube, and I put the two end ribs past where it bolts on. My build is a moving gantry. It worked out fairly well believe it or not. 1Jumper10 used a different technique to weld ribs on his build. Even snug fit plywood that is glued in place can be used. I looked at a large commercial router in a different thread, 9mm wall, very large span, no ribs. There are a few options available if he wants to add ribs. It won't make any difference worth mentioning if the ribs are just past where the bolts go as opposed to end caps if he decides to do it that way.

However, all in all, that is a far more robust and reliable-looking design.

Oh thanks. . I hope it helps out the OP with his progress. Perhaps he will use some ideas but modify it to be better.

[RCaffin]

Stick welder on the end on a broom handle ...
OK, I'll pay that one!

Cheers
Roger

[boltzzz]

Thanks guys! Your input is much appreciated. It's amazing how a little discussion and brainstorming can make a huge difference.

Thank you NIC 77 for the drawings. As you say, a picture says a thousand words.
Your design looks great. Very simple indeed. I might try playing around with something similar, just on a smaller scale.

I actually never thought of a base arrangement where each part can be dissemble to assist with transport.

I agree that welding flat plate to the tubing is the way to go. That way I could go with a thinner walled section, maybe 4mm instead of the planned 6mm. This is save a fair bit of weight throughout.

[handlewanker]

Hi.....yesssss.....I like this design layout much more than any other we've talked about........as far as the welding is concerned, an hour with a gassless Mig welder and you are almost an expert.

If this build was in the 6040 size with the design as indicated, and having the 600mm across the width as the X axis, I think it will work out very neat......and compact too.

One thing I would stress........make it ALL from the same size tubing as this is a cutting list that you can pick up ready cut to size from the metal merchants and it saves time and money too.

An EBAY 6040 CNC router made from aluminium would be the model to aim for and it's capabilities.

As it's a 6040 build, but in steel and to a better design, there is no need to have overly thick tubing....... even 3mm wall is massive.

A 6040 in aluminium would be the model you're aiming to replicate with machining cap[ability, but with steel for ease of build and economy......the thinner wall tubing will lend itself to Mig welding better than heavier stuff.

With welding, only use short welds, and cool the sections regularly as this will cut down the heat build up and prevent distortion.

I would highly recommend gassless Mig welding as this is the more cost effective.......eg, no Argon gas bottle rental etc.....gassless Mig wire is more expensive but user friendly.

I personally don't use any conventional welding methods or materials any more, not for the last 5 years as I now use a plasma welder, but I do still have a complete conventional outfit.....up for sale on EBAY....... and have used all forms of welding over the years.

I think the latest design by NIC is a winner from simplicity.

One amendment I think I would make......I would not bolt the 2 bottom tubes to the side base tubes.....they need to be welded as an assembly......they need to be a rock solid box like frame to keep the Y axis rails from going out of alignment to each other......and on that score I'd lay the base tubes down on their broad side instead of the narrow side up and weld the ends closed.......small welds all round etc.
Ian.

[boltzzz]

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?

[handlewanker]

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.

[NIC 77]

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.

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.

[handlewanker]

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.

[NIC 77]

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?

http://www.cnczone.com/forums/vertic...m-posts-2.html

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.

[handlewanker]

Hi....to build in aluminium, steel or wood even...........they all have their own very particular fastening methods and tools to work them.

Unless aluminium welding was your main occupation, that is one method to not even consider....sending out to get it welded will double your cost.

Extrusions?......much more costly but OK if you can do the designing to cater for the shapes etc.

Wood?......well, many people have built with wood for cutting wood plastics and a wee bit of aluminium.

For a hassle free economical solution I think steel tube and then steel plate would be the answer to success.

One thing you can do is work steel with a grinder very easily as it doesn't take much effort.

I'd go back to Nic77's concept drawing and do a full scale model quick build, making a mock up in cardboard, as once you see it in the flesh you get a much better idea of where you want to go and you can hack bits off and add bits in with wood glue until you're happy with the design.
Ian.

[NIC 77]

I wonder if rivits, special aluminum adhesive, and some "L" angle stock could do the trick instead of welding.

I've been thinking about some designs in my head for this, actually the drawings I did for the steel inspired me to think of how to make a structure from aluminum plate, and also Stef's thread. Unfortunately I don't have time to draw them out. It would be more of a puzzle with ribs and stringers that goes together and interlocks with alignment tabs or interlocking slot cuts, similar to what Stef did. Not really similar to what was first proposed in this thread, but a similar idea, to make the entire thing out of a thick aluminum sheet that fits together. Perhaps 1/2" or 3/4".

The expense would be for the big flat sheet of aluminum and to have it cut on a CNC router somewhere.

The thing is, you could design it with all the holes drilled for the rails, rivits, etc. to be cut with a CNC router, and I am thinking it would be easier to assemble and you could make something really cool.

[RCaffin]

Large rivets would work, but I would favour LOTS of M6 or M8 SS cap head bolts - with SS washers. And I would back them up with SS drive pins for absolute location.
Adhesive for aluminium: ordinary epoxy resin (eg Araldite) works wonderfully. Clean all Al surfaces with alcohol first and NO fingers.
Bolting means no heat distortion. More work maybe than welding, but better results imho. Until you go to very large castings, well annealed.

Cheers
Roger

[boltzzz]

I was originally thinking something along those lines. A flat packed ikea design made from alloy plate, CNC machined with alignment tabs and DA (determined assembly) holes. It would be an expensive design though. I quick google of the raw cost of aluminum vs steel is about 4.5 times as much. I also envision the CNC machining of the flat plate wouldn’t be cheap. Maybe something cheaper like water jet cutting would make it feasible. Stef’s design is pretty awesome!

At the moment I think the steel design is the best for simplicity, cost and reliability. I’ve also thought about capping off the ends of the lower base tubes so that they can be filled with sand to increase the machines weight to reduce vibration if needed. The sand can be drained when moving.

The only concern I have about the steel design is weld distortion which I know very little about, so I bought a welding book off the net that will come in a few days.

It’s one of those things. You can continually improve the design over and over and over but at some point you have to commit and actually build something. I’ve been thinking about a CNC router for a good year now, I want to commit to a good design and start building
I think the steel build is a great first build.

Even though you guys have stated it can be done with an angle grinder, I’m leaning towards getting all interface surfaces machines flat.

Definitely NOT welding in an apartment. I have access to a good shed elsewhere for making this machine. I will only be assembly the parts in the apartment; and that’s if I do move it to the apartment. It’s something that I might just leave at the shed, though it is an hour’s drive away and only go there once a week to once a fortnight.
I’m located in Melbourne.

Couple of questions to help me with the design.
How would you aligned all of the parts? Would you use locating dowel pins or would this restrict future adjustment?
Are there any routers you would recommend? I was thinking an ebay water-cooled 2.2kw router. Also, how long is the router bits I would be using (so I can calculated the Z axis), from base to router to base of tool tip?

[NIC 77]

The only concern I have about the steel design is weld distortion which I know very little about, so I bought a welding book off the net that will come in a few days.

Thin walled smaller size tubing is easy to distort. For example 1.5" x 3" x 1/8" is easy to get distortion in. 6" x 6" x 1/4" is not easy to to get distortion in. Flat plate can also distort fairly easily, depending on the thickness.

For the larger flat bar size, weld on the front and back, not on the sides. It's not needed to weld on all 4 sides, and this reduces the chance of making a smiley face instead of keeping it flat.

You tack all around before you start welding. It's not likely that thick material like this will distort too much unless you have way too much heat going to your welds.

I'm not an expert welder, but this has been my experience. I would not worry about it too much with the size of stock you will be using.

Even though you guys have stated it can be done with an angle grinder, I’m leaning towards getting all interface surfaces machines flat.

Check the price. I believe it was $1400 dollars a local machine shop wanted to grind four 1.5" x 4' strips flat for me. No way I went for that. I figure it was only a few hours work at most. The thing is, I called around to a bunch of shops in town and could only find one that could do the 4' length, and I live in a fairly large town. You may get lucky and find someone who will work for an honest wage, or you may reconsider how you do this.

There are also some tricks you can do with epoxy.

Expect to spend many many hours drilling and tapping holes, and when a tap gets dull, chuck it. You will wear out a few taps, and you don't want one breaking. Dull taps are easy to break IMO.

Couple of questions to help me with the design.
How would you aligned all of the parts? Would you use locating dowel pins or would this restrict future adjustment?

No to the pins.

Basically, here's how I'd do it (I've done something similar on my own build).

I'll use the dimensions for the drawing I did so you can understand what I mean, you will have other dimensions for the different metric tube size / flat bar size, which will actually work a bit better than what I drew.

So you take a piece of 6" x 1/2" flatbar that has been cut to length. You drill the four 1/2" holes as precisely as you can using as a minimum a drill press. Have you drilled many holes in steel? The RPM needs to be low. Low RPM for steel! A little oil helps too. If the RPM is too fast, the bit will heat up, and get dull. Then you either need to resharpen it or get a new bit, and it will never be as good as when it was new. You know you have a good RPM when you get nice long spirals coming up from the hole.

Then you take a second plate of the same size, and use the first plate as a guide to put holes in exactly the same places on the second plate. Use a permanent marker to indicate which faces touch each other and which plate set it is, give it a number, 1, 2, etc. You make all your plate sets this way so you have matched sets.

Then you use one of the plates and clamp it to box steel section that will have holes going through it. Use some scraps of wood to help you, I think I had some 1" x 3" scraps kicking around, when you use the same size flat bar as the width of your tube, the tube will have rounded edges, so to align it well, scraps of wood on each side with a clamp at an angle so it doesn't interfere with you drill press, and it's aligned. You use the flat bar as a guide, drill the first hole, put a half inch bolt in the hole so it doesn't move, drill the next hole, etc. When you're done, clean the edges of the holes with a flat file or angle grinder with a flapper sandpaper disk. Then you bolt both pieces of flat bar to it with 1/2" bolts. So for the bottom cross beams for example, each would have four pieces of 6" flat bar bolted to it in two locations.

When you've got all the pieces of 6" flat bar bolted on, then you can take all the tubes and clamp them together using big pipe clamps or whatever. I actually used a bunch of threaded rod, and pieces of wood to clamp everything together. So two pieces of threaded rod and two pieces of wood with two holes in each piece of wood to make one clamp. A level, a measuring tape, a rubber mallet, a square, a long straight edge, some stainless steel shim tape, all good things to have on hand. Set up could take a few hours, check and recheck everything five times.

Then you tack weld all the 6" flat bar to each piece in multiple spots. Once everything is tack welded really well, you take off the clamps and unbolt the 1/2" bolts. Now each piece of flat bar is attached to the piece it belongs to and you can position each piece as needed to weld it properly.

If you did a good job, you can reuse the 1/2 inch bolts and everything will fit perfect. If not, you can switch to M10 bolts and have a bit of adjustment.

After that is done, you can weld the 1.5" x 0.5" flat bar where the rails go. Use stitches instead of trying to weld the entire lengths, and alternate which side you tack then which side you weld.

It will be a fair amount of work.

Then you need to make the mounting surfaces for the rails flat, and then drill and tapp holes for the rails. Then when you have the parts moving well, add the ballscrews, limit switches, cables, etc.

Are there any routers you would recommend? I was thinking an ebay water-cooled 2.2kw router. Also, how long is the router bits I would be using (so I can calculated the Z axis), from base to router to base of tool tip?

I don't know what spindle you should use. I would want to be able to use a bit with a 3" flute length to cut through 3" of material that is held to the table in a low profile vise and also a half inch flute length bit to cut through half inch thick material that is flat on the table. If you can do both of those things, you're probably golden, but that's just my opinion.

Also, as you want to make the pieces portable, I would not fill with sand. As an alternative you could use high density polyurethane which has an expanded density of 4 lbs per cubic foot, and you will have to put your ribs past where the pieces bolt together. See 1Jumper10's new build log, he does this on some parts.

[boltzzz]

Thanks NIC 77.

Check the price. I believe it was $1400 dollars a local machine shop wanted to grind four 1.5" x 4' strips flat for me. No way I went for that. I figure it was only a few hours work at most. The thing is, I called around to a bunch of shops in town and could only find one that could do the 4' length, and I live in a fairly large town. You may get lucky and find someone who will work for an honest wage, or you may reconsider how you do this.

If it's seriously this much, I will need to reconsider. I was thinking it would only be a few hundred dollars. The trouble is, not many people want to do small jobs like this. I would prefer to machine the interfaces but I could always use the epoxy.

Expect to spend many many hours drilling and tapping holes, and when a tap gets dull, chuck it. You will wear out a few taps, and you don't want one breaking. Dull taps are easy to break IMO.

I've never really liked the idea of tapping holes. I thinking of going 10mm plate and just bolting them together with bolt/nut instead of tapping.

[handlewanker]

Hi, all structures I've worked on in the past were mostly....90%.......welded, but some were composites with parts that bolted onto them.

A lot of them were in difficult situations where you had no reference plates or large flat level tables etc to check for alignment, so the good old flat steel strip....known to be flat etc....... and plumb lines did the trick.

For a small build like a 6040 router type you can make a straight edge from a 600mm long piece of bright mild steel strip that you check out by having 3 of them and test one against the other for straightness etc......the end result will be a good as it gets, but without some form of reference to check alignment you won't get off the ground.

Having been long in the trade I speak as if it's a doddle, but if you make/get a few tools to do the job yourself it won't cost you heaps, and many lurks can be applied to get there.

Apply the logic that the longest journey starts with the first step......that means finalise on the design.....even make a mock up model.....then make a start on the basic bits........then you just add bits as you go along.

BTW.....whereabouts in Melbourne are you.......I'm in the southern suburbs......Dandy North.

Here's a pic of the steel build I started before I back burnered it when the mill arrived......the tubing is 75X50 X5mm wall.
Ian.

[NIC 77]

Thanks NIC 77.


If it's seriously this much, I will need to reconsider. I was thinking it would only be a few hundred dollars. The trouble is, not many people want to do small jobs like this. I would prefer to machine the interfaces but I could always use the epoxy.

If you can find someone with a large router and you buy a whole aluminum sheet direct from the main supplier (cut out the middle men) then you might find the cost of your first idea is comparable to having a shop grind your surfaces flat. I don't really know. For me, I'm on a budget, so, 95% of my steel came from the scrap yard, and I use the tools I have available. Also, I have alot of experience using an angle grinder. It's not a hard skill, but it's one that some people are intuitively good at, and some are not.

One more thing, I thought I'd mention, is linux_fan's thread if you haven't seen it.

http://www.cnczone.com/forums/uncate...aluminium.html

He made a pretty awesome gantry for his machine from aluminum plate.

I've never really liked the idea of tapping holes. I thinking of going 10mm plate and just bolting them together with bolt/nut instead of tapping.

Unfortunately, you're not going to be able to avoid tapping holes regardless of what path you follow IMO. Once the holes are drilled, the tapping is tedious, but I have to think it's still better than the bolt/nut combo. Aluminum is easier to tap, but you still have to be careful.

Sounds like handlewanker might be offering to help. Well, if you decide to weld, and you can get some help from someone who's done it, that might be very advantageous.

[boltzzz]

Thanks NIC 77. I haven't seen that design. Those aluminum designs do look great don't they! Over the next week or so, I'll refine two designs. First the steel tube design that you recommended, then a second aluminum flat plate design. I'll compare both and then choose one to start building!

[handlewanker]

Hi.....one method that has not been discussed anywhere that I have seen and that is an aluminium build with riveting.....not a bolt or screw in sight for the frame build......that is almost as good as welding.

You still have to work out your interfaces like right angles and butt joints etc, same as bolting, but without the heads and nuts sticking out of the surface and also no tapping of holes.
Ian.

[boltzzz]

Yes. Riveting could be a good idea. I actually already have a pneumatic rivet gun and bucking bars.

Here's a quick sketch of a design similar to Stef's.

Most of it is 10mm thick which the exception of the base upright pads which are 15mm and the base rail pads which are 20mm.

Disregard the details of the uprights. They're just from the other design.

Was thinking it could be joined with angles and bolts/rivets.