Decent size of material... Best options...

[Tennalum® 7068]

Hi I am currently prototyping a larger intense project. I expect there to be a lot screwing up before I get it perfect.

Looking for cheapest steal and aluminum chucks 36”X36”X6”(Thick)

At this time grade really doesn’t matter as long as it can be machined easily and costs cheap I don’t care. Like I said this is simply stock to screw up on.

What would this run me you think cost wise?

 

[YYCHM]

Unless I did this wrong.... that's 2200 lbs of steel What kind of machines are you playing with?

 

[Tennalum® 7068]

I honestly don’t want to go steel but steel is cheaper than aluminum.

Not hobby machines that’s for sure lol...

 

[Tom Kitta]

Just over 1t of steel. Problem is the shape may not be available. If shape was available in your exact size I expect to pay around $2000. Less if you are frequent buyer. Best thing to do is to ask for a quote - I think main problem will be availability of the shape you are looking for - what I mean is that 6" thick sheets may be sold in size of for example 4' by 8' only and you will be asked to purchase whole thing. I was assuming relatively easy to machine 1008 - obviously here you may also run into issues as certain grades will not be available in selected size.

Obviously you can go cheaper with say remelted rebar "steel" but I doubt anyone is selling that.

What I am sure of is that you cannot get it cheaper then current wholesale price of steel unless you buy at an auction. Current price of steel scrap is 100 per t and price of steel wholesale is around 10x that.

 

[PeterT]

OnlineMetal in USA just as rough guidance. So US$ and FOB wherever they are located. At that price, hopefully not too many screw ups LOL
Sadly, even at 1.3x FX I have found them to be cheaper than many of the local places (meaning new stock) but it varies by product & size & availibility.

 

[DavidR8]

OnlineMetal in USA just as rough guidance. So US$ and FOB wherever they are located. At that price, hopefully not too many screw ups LOL
Sadly, even at 1.3x FX I have found them to be cheaper than many of the local places (meaning new stock) but it varies by product & size & availibility.

Don't forget to factor in shipping.
Edit: sorry I missed the FOB in your post...
I'll bet when freight, taxes, duty and brokerage are factored in I'll bet it will be the same price as local.
Metals are a commodity so the market dictates.

I did a price compare between Online Metal and Metal Supermarket and when I added exchange into the Online price and Xometry and both were within pennies per ft. of my local Metal Supermarket price. But that was before shipping which basically means my local store is not ripping me off terribly much if at all.

Now that's not for 6" plate mind you!

 

[PeterT]

Yes it always pays to shop & compare all in costs because it can vary back & forth.

 

[Janger]

Could you use wood for testing?

 

[Tennalum® 7068]

Potentially @Janger been thinking about it and even plastics just need to be able to be cut and shape possibly with ballnose endmill and not not crack or blow up or fall apart.(The material not the endmill) Some more critical dimensions need to checked and finalized so material needs to keep shape be sturdy and not chip or deform.

 

[PeterT]

People that do CNC prototyping like for larger composite molds will often laminate stacks of MDF before committing to more expensive materials. A sheet of 0.75" works out to about 1 cent per cubic inch FOB your local lumber yard. By comparison the aluminum works out to about 90 cents at source so +90X more. Its pretty dense, relatively stable. I've seen some decent looking limited run composite parts come off both male & female MDF molds. Sometimes they finish the plug itself like with resins & paint autobody style. Some pull a shrink wrap liner kind of like what the car guys wrap those fancy graphics. Another advantage is you can 'castle' the lamination contours to either be a semi hollow body or if it is an irregular shape which potentially saves milling time hogging down a block shape.

If its just a mock up you could go cheaper yet & laminate insulation foam. That is common material for special FX industry. Actually you can get urethane tooling foams in all kinds of grades & densities, they are very common for this application. Tooling urethane blocks can be similarly laminated, but last time I was involved in this stuff it actual cost more than aluminum on a volume basis.

If you are doing something more substantial like a metal die for plastic injection molding or stamping/forming (ie. where cheaper, lower density/strength materials don't serve any purpose) well that's kind of the big leagues. Even then I'd be shocked if they didn't mill a cheapo tester rather than commit to a big chunk of alloy.

 

[Tennalum® 7068]

@PeterT

Thanks man I think I’ll try to get the 0.750 MDF sheets and laminate them to together to get my 6inch depth. At 40 bucks(Home Depot) a sheet seems a lot cheaper than using metal to shart with. Cut and laminate my 36X36X6 block together.

Don’t know much about laminating tho and never done it. Seems one could whip up a block pretty easy for cheap.

 

[PeterT]

Generally woodworking glues work well enough. A notch trowel type spreader can help regulate amount. Some guys lay them up in pairs, let them cure, then double the pairs... If you try to laminate them all at once it can can be unweildly & probably need lots of big clamps etc. If a shop is set up with vacuum bagging they can do the whole enchilada in a big bag exerting lots of uniform pressure. Then epoxy can be used as adhesive. Some wood glues don't play nice under vacuum, they need air to cure. But I know they have wood glues formulated for vacuum.

Pressed wood products like MDF have a slight density difference as a function of how they are made (pressed). The outer skin is slightly more dense than the core. This isn't really a problem with thick blocks but on thinner & non-symmetrical sections can lead to some minor warping as some core material is exposed & the shape stress relieves. So that's why you might see a multi stack-up of 0.25" rather than a single 0.75". MDF is also prone to chipout & fuzz & you need a healthy vac system. The cnc router guys are set up for this. The cnc metal machinists generally aren't crazy about wood & MDF doesnt take coolant anyways LOL. Good luck!

 

[PeterT]

Maybe peripherally related to your project, maybe not but nice eye candy anyways. Workshop pics at bottom of intro post shows the typical technology state of RC model composite molds CNC milled from aluminum. And I hear not just any old billet, they are semi machined, heat stabilized, then fully machined, then hand polished etc. There's a reason most come from eastern block countries these days. https://www.rcgroups.com/forums/showthread.php?3066115-Ultima-2

 

[Tennalum® 7068]

There will lots of machining to do your suggesting to use 0.250 sheets as opposed to the 0.750 sheets for less chipping and fuzz?

0.750 sheets= 8 layers to 6 inches
0.250 sheets= 24 layers to 6 inches!

 

[trlvn]

You can get thicker mdf, as well. Try an internet search for 'mdf thickness sizes'. The first hit I looked at said they had sheets from 3 to 32 mm thick available and would custom cut.

You haven't said anything about the final shape of the part. Is a casting a possible starting point? There are still foundries that cast parts for locomotives and ocean-going ships, so I would guess a part the size you are describing is possible. Could save a tonne of material and machining time, depending...

Craig

 

[PeterT]

There will lots of machining to do your suggesting to use 0.250 sheets as opposed to the 0.750 sheets for less chipping and fuzz?

Re the potential for fuzz and chipping is common to any MDF & has most to do with the cutter, rpm & how its feeding on that particular part of the surface.

Re the lamination's, really depends on your application. I'm just pointing out that thin or more complex varying shapes can stress relieve a bit. For example a propeller blade, thick in the hub where its meaty cross section but varying airfoils & thin at the tip with a desire for close overall dimensional control. So maybe a better way of saying this is strive for minimum 5 lamination's for any given shape, after that it probably doesn't matter, 5 vs 20 will probably be the same. Some carvers hate the glue lines because that's where some of the chipping occurs or it is a 'hard line' that shows up in finishing. The resin application & finishing techniques to go from CNC milled wood to 'shiny object' is a whole other discussion if for example producing a plug or mold for composite part. But you haven't really said if this is the end result so I'll leave it at that. This (MDF) is not 'within a thou' type application, more for prototyping on the part & milling itself. Some shapes can be complex where how to hold it in the mill or leave remaining sacrificial material is the biggest concern... things like that

 

[Tennalum® 7068]

I am basically building a frame and want to do it as one whole piece for strength reasons. So yes there is going to be crap ton of milling. No pun intended here.

Now let’s say the weight calculated of the steel block at 2200 pounds is deadly accurate. My guess and really not sure but frame will probably be 50 to 175 pounds once all the milling is done again rough guess.

Now was thinking of building it multiple pieces it would be cheaper for sure no question. But think I would lose to much strength, alignment factor and symmetry would be concern as well.

I don’t like the cast idea billet block is stronger and quality is very import to me on this project as there may be liability issues if I don’t do this 100% right or try to cut corners. I don’t want cut corners and probably can’t afford to cut corners. I don’t want to give the liability freaks and other controlling body’s a snowballs chance in hell to complain. I already know it’s already going to be milling nightmare and what you do 1st,
2nd, and 3rd etc... in terms of processes is going to matter a big deal as vibration and other milling issues will surface.

 

[Former Member]

A little late to this thread, couple of comments for future reference if you are looking to go down this route.

Buy from a distributor at that weight, at least half the cost of any metal retailer/outlet. For reference that piece of Al is about 770lbs +/- and current cost would be approx $3,850-4000.

Second, if this is for a mould, laquer and wax it, MDF is a great (best) option, if you are layering might as well lighten the weight even more, and create hollow pockets (BTW works with aluminium bar stock as well, and is cheater than a block, lower cost).

You want a preduction mould, consider the first MDF mould a plug, create a mould and than create a reinforced fibreglass plug. This how the pros do it.