Mild steel box section pricing

[reefy86]

Stupidly expensive now right?

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[Neale]

That looks very like my local supplier, Austen Knapman. All I can say is that their online prices are always higher than you pay if you just walk in or order over the phone for collection. Saves maybe 20-30% on web prices. I last bought box section from them a few years ago when I built my router, and that was only 50x50x3, so no idea how that matches the going rate.

You are a long way from South Devon, though...

[reefy86]

Few years ago when I was going through the pricing up stage the mild steel sections was dirt cheap and it was costing me around £500-£800 tops to make the frame now I'm looking at probably around £2.5-£3k. The 3mm thickness ain't too bad but isn't that a little too thin?

[JAZZCNC]

Steel prices have at least doubled in the last year or so but that does sound expensive for only 3mtrs, I would expect to pay about that for 7.5mtr length. Steel is also in short supply and I think some suppliers have their pirate hats on.!

Like Neale says deal with a local supplier rather than through the internet and you'll get it cheaper.

3mm is too thin for the mainframe but will be ok for a base frame, I wouldn't go less than 4mm for the mainframe. Why 90mm.? That's not a common size so you'll be paying more for that.!

[reefy86]

Mainframe and base frame?

[reefy86]

Thanks Dean and Neale I'll hunt around my local area.

[cropwell]

Check out Nottingham Steel Supplies in Colwick. It doesn't hurt to talk to them,

Cheers,

Rob

[reefy86]

I live 5 mins from there as well lol. Thanks Rob I'll check them out

[Kitwn]

Mainframe and base frame?

My definition would be that the main frame has all the exciting bits like rails, ballscrews, motors etc. fixed to it and the base frame has the main frame fixed to it to keep you from grovelling about on the floor.

Kit

[Neale]

Quick comment on thickness - yes, with experience, 3mm is too thin. It's strong enough (the sections supporting the X rails are 100x50, the rest is 50x50) but is inclined to ring a bit. Thicker would provide more intrinsic damping, I think, and I would go for 4mm and, possibly, 5mm for some elements despite the extra weight. That's for a 1500x750 cutting area. There are other things I would change as well with experience, but at the time I built it, there was less information around than there is now.

But this one took me long enough to build so no plans for replacing it any time soon!

[reefy86]

Ah OK I figured that but going from my old drawing I think I had the frame at 4mm and then had the beams that the linear rails and ball screws being attached to at 10mm thick.

[Neale]

I added steel strips to the faces where the rails bolt on - good for fixing but no damping effect, I suspect.

[reefy86]

Sand is your friend for dampening but wouldn't surprise me if that's gone up 5 times the price too lol.

[Kitwn]

Sand is your friend for dampening but wouldn't surprise me if that's gone up 5 times the price too lol.

I've wondered if foam concrete would do the trick. Less weight and the air component of the mix is relatively inexpensive.

Kit

[cropwell]

I've wondered if foam concrete would do the trick. Less weight and the air component of the mix is relatively inexpensive.

Kit

My late next-door neighbour was a builder. His trick (and I suspect a trick common in the trade) was to give a good squirt of washing-up liquid into the compo mixer. It foamed up the mortar and made it lighter to handle and slippier off the trowel.

Of course for filling beams you really need high density, low elasticity, acoustic decoupling air.

[Kitwn]

My late next-door neighbour was a builder. His trick (and I suspect a trick common in the trade) was to give a good squirt of washing-up liquid into the compo mixer. It foamed up the mortar and made it lighter to handle and slippier off the trowel.

Of course for filling beams you really need high density, low elasticity, acoustic decoupling air.

Making foam concrete the DIY way is basically taking that a step further. I've been looking at it for possibly making raised garden beds. Suggesting it for damping a machine is primarily for the practicality of not being too heavy for one person to handle on their own, which is a consideration for all of my construction work.

Kit

[reefy86]

Just got a quote from my local and they only do 7.5 meter lengths and for 80x80 5mm thick works out at £85 for 3 meters

[JAZZCNC]

Just got a quote from my local and they only do 7.5 meter lengths and for 80x80 5mm thick works out at £85 for 3 meters

Well, that's half the price of the other place so you are already in front.

[reefy86]

More happy with the 5mm then the 4mm. Still worth filling with sand or is there an alternative way now?

[JAZZCNC]

More happy with the 5mm then the 4mm. Still worth filling with sand or is there an alternative way now?

Sands ok but only to a point, depends on what you want the machine for.? If you're wanting to cut steel then your probably building the wrong machine with the wrong materials.?
If it's for cutting wood and light aluminium work then I wouldn't waste your time and mess it makes, just use thicker material with plenty of bracing.

[John McNamara]

Re Damping.

This (Excellent) paper may interest you of you are thinking of building a machine and filling steel tubes with damping material. There are practical examples towards the end. Of note is the thin flexible layer between the concrete and the way it is sectioned within the tube in plastic bags in one case, it is not just poured in.

The machine designed in the paper, a tool and cutter grinder was actually commercially built by Star.

https://my.mech.utah.edu/~bamberg/research/StarToolGrinder/EberhardBamberg-PhD.html

Youtube "edge precision" to see one working.
https://www.youtube.com/watch?v=N2vPng7O5bQ

You can download the paper from MIT
https://dspace.mit.edu/handle/1721.1/88839

Regards
John

[reefy86]

Sands ok but only to a point, depends on what you want the machine for.? If you're wanting to cut steel then your probably building the wrong machine with the wrong materials.?
If it's for cutting wood and light aluminium work then I wouldn't waste your time and mess it makes, just use thicker material with plenty of bracing.

Just wood/acrylic and aluminium but not sure what I could achieve when it comes to aluminum (20mm would be good)

3d detailed carving is a must and that's where I was thinking sand would be needed?

[reefy86]

quick question, is 80x80x5 all around with 100x100x10 for the rails strong enough for a large machine or will i need to go 100x100x5 all around?

thanks

[JAZZCNC]

quick question, is 80x80x5 all around with 100x100x10 for the rails strong enough for a large machine or will i need to go 100x100x5 all around?

thanks

Depends on how large and design, do you have any plans or models to show.?

[reefy86]

having to start right back from beginning but shouldnt take too long as most of it is still in my head. this design so far is using 80x80x5 and just the support beams for rails is 100x100x10. also thinking of making it half weld half bolt on and have the main rail support bolted onto 10mm plates rather then welded to the legs if this makes sense but then i dont want to over complicate things.

this is mine now

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this is how i think i should do it

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[JAZZCNC]

Well first, the bottom picture is a very old design of mine and isn't actually complete.! It's missing the adjustable height bed which bolts to the sides and adds a little more rigidity, but even then it's not the stiffest design in the world and uses smaller thick-walled tubes. It's also a relatively small machine and was only ever really designed for cutting woods, plastics.

Regards your design then it needs a little work, for instance, you have no supports for the bed base or any bracing between each side. Would add some supports lower down on the sides to support and brace the legs as well so it doesn't change shape when moved around.

Whether you fully weld or not is up to you but what I will tell you is that when you start going large things are not so easy to get flat or surfaces planer to each other so building in adjustment is a good idea.
To be honest, if you have never built a router before then going large can be a big mistake, esp if you are wanting to machine materials like aluminum to any degree of accuracy.

It's a very common mistake to assume it can't be any more difficult to build a large machine than a smaller one.! . . . This is the mother of all Fu@k up's because when starts to go past 4ft in length things get real funky very quickly.! Have you ever wondered why there are so few build threads showing large machines.? It's not because people haven't tried, many have tried, it's because very few succeed, and most give up well before completion.

Also, doesn't matter how thick your tubes are if the design is crap or it's poorly welded or aligned with out-of-whack surfaces, etc.

My advice is to think long and hard before you go BIG and be sure you know what you are taking on and are doing because it's super easy to get wrong.
Starting with a smaller machine would be a better idea to get the feel and knowledge for whats required to build a BIG machine, plus it can help you build the Big machine.!

[reefy86]

appreciate the advice Dean if im honest i do have the confidence and i was tempted to start with a 4ft cutting area and use that to make a bigger machine in time but for the work i want to do it still needs to be wide enough to cut 4ft sheets so the only difference if i was to build smaller is just the length. i understand its a different ball game once going past 4-6ft but i would really like to put my head and heart into it and give it a good go. you have warned me though and if i fail its on my own head but im one of those guys that looks back and thinks oh well atleast i gave it a try. like i said im confident in giving it my best shot.

also i never knew solidworks had a rendering feature built in, had a little play earlier and here is my frame so far. done it this way so i dont have to weld the support rails and risk twisting ect and i can always add shims to those plates if needed.


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