The CNC experiment build.

[NeoTech]

So in casa NeoTech, the crazyness has stirred up under the winter and a new CNC machine build has been planned, parts begun to be sources.. So this is a bit of "so far i have."...

So basicly i started to read upon this polymerconcrete thingymajig. And its an awful interesting material. And an awful interesting theory of outcome and use.
But one thing.. even tho this material is a epoxy base concrete.. It still a concrete. Something most threads i have read seems to forget.

So my approach to this a bit different. Instead of casting in anchors i have decided to cast in a subframe as integral structure. And this is what i have come up with.

edit: changed out some of the internal frame after i reevaluated ridigity by reducing internals until it started to flex alot.

As seen a series of interconencting 2mm sheet parts are welded into the exposes metal parts that are meant for bolting stuff to. These in turn will be the reference points for the mold as well and later on ground parallell in place.

So this is basicly the project, and parts have begun to be sourced.

The list basicly looks like this atm.
-- Servodrivers: Granitedevices Argon - http://www.roughedge.se/blogg/wp-content/uploads/2015/01/IMG_0466-e1421069123861.jpg
-- Servomotors: 1.5kW 130mm framed Quadrature motors from MiGE (china) http://www.roughedge.se/blogg/wp-content/uploads/2015/01/2015-01-20.jpg - Click this link for size reference, this is the motors intended for motion.
-- 32mm ballscrews with a 5mm pitch: ordered
-- 30mm linear guides from hiwin: ordered
-- Mesa 7i90HD + 7i48 Servo card: Ordered
-- Misc electronics parts: Orderered.
-- BT40 @ 8000rpm Spindle with ATC (chinese): Still haggling.
-- 7.5kW spindle servo motor from MiGE: Still haggling.
-- Lasercut metal parts for the frame: on hold until all cad is set in stone.

And yes yes, i know "buy an old machine and convert instead, bla bla".. not interested in that.
The whole project is, how would a polymerconcrete machine be able to behave - and what precision, speed and force would it be able to handle.

I plan to make the drawings, parts list and all that available on my website as an openhardware effort when i get that far.

[DMIOM]

Neo, I'm eagerly awaiting to see this come to life, meantime just a couple of thoughts:

The Y rails don't seem to be exploiting the full width of the base - if they were further out (i.e. towards L / R sides of the base) then there might be less tendency for the saddle/table to droop when at min/max X travel - it looks like you could almost double the rail spacing within the same footprint.

The Y ballscrew looks to be quite a way below the saddle / rails - when its pulling or pushing, I suspect part of the force will be racking - trying to tilt / lift the front or back of the table - I'd be wondering about getting the ballnut as high as practical (like your X ballnut looks right beneath the table, in the same plane as the rails).

I'm not sure of the overall size of the machine; but the table looks a bit out of proportion to me. On my CNC mill, I tend to leave a vice mounted on the right of the table and use the left hand side for clamping-down, fixtures etc.  Even if you're using a pallet-style or tooling plate to quick-mount your vice, there may be times when you need that length of table - e.g. using a fourth-axis and tailstock?

Dave

[NeoTech]

Thanks, for constructive feedback. And you are right, there is alot of "height" for the Y axis down to the bottom screw, from the center of the ballscrew to the bottom side of the saddle its about 100mm. whichwill prob, create a problem. Each ballscrew will have double ballnuts, with the flange pointout outward in their respective travel.
The same problem actually exists under the pallet and behind the head.. And i havent figured something good here yet. The motor frames is 130mm and they require alot of free space to center well actually, more than one could imagine.

This is the main reason im not ordering the laser cut parts yet, i need to reiterade over this when i have the 32mm ballscrews and flange nut in my hand and know how they are in relation to the motors.


That palette is 400mm x 400 x 40mm mm palette. The idea of it is to have a quick lock system with 4-5 screwed inserts. (see attachments).
The overall travel of this machine would be in the range of half a cubic meter. - And the idea of a 4th and a 5th axis has occured to me, but atm im thinking of it as a module that can be lifted into the machine and locked into the pallette.

[RotarySMP]

 cool project. 1.3kw would seen total overkill for this size machine. The epoxy grantir machines made by Nucky in the cncecke.de forum use 400-800W drives for roughly this size machine with very high performance.
What are you truing to acheive through the embedded sheet metal parts? You are still going to need to build forms for casting the epoxy granite.

Do you plan to source premixed aggregate, or mix your own. The difference in E modulus is suppossed to be about 2x between a home mix and a mix donebto the Fuller curve.

Have you designed in the way covers?
Mark

[sparky961]

You may want to consider a longer (wider) table, more like a Bridgeport-style mill.  There are many setups where this length is an advantage.

If you swapped your table and the piece between that rides on the Y axis, it wouldn't be much different but it would give a lot more working area for larger parts and clamping support.

[NeoTech]

If i can, i will try to source premixed aggregate - actually nothing that is sold in Sweden.. Dont know why. Something something, about enviroment something something..
You know those dilly wagger tree huggers, making it hard for people doing what they want.

If you have suggestion on a premix by name, i can see if i can source it from somewhere close, would be much appreciated.

The idea of the steel metal parts.. Well for one thing, what kills concrete in the end, vibrations that have broken it up and it wither and well breaks down.
And after looking at several of large machines built with this technique i notices they hade alot of sheet metal steel parts and fasteners within the casting.
But yes, i will still need to make forms/molds for casting this, its not a way to get around that problem. Im more thinking ridigity.
And when simulating this in solidworks, it reduces the elasticity of the casting by alot - so it seems to worke like rebar.. =)

About the 1.5kW motors. uhm well.. i talked to this chinese lady that really doesnt seem to speak english. And after alot of back and forth it ended up with "i take what the 99.8% of your other customers want in a 130mm frame".. and i got these.. they cost me like 600 usd, so not that expensive actually. =)

So if i wanna run a larger, longer table, that would mean i would make the saddle smaller. The big issue i see with that is that a smaller granite casting, even with reinforcment would be prone to breaking and flexing. And sure i could just make a larger table and space out the rollers, but that would limit travel instead. I need to ponder this tho, many people suggests the larger table, and just bolting down a wider palette ontop of that palette doesnt seem to be a good solution based on that. =)

[NeoTech]

Well here is the build video that started me on this route anyway. =)

[Brass_Machine]

That is an interesting video.

I will be watching this as much as I can. Have a huge interest in it. Spent most of a day a few years back reading the huge thread on CNC zone about this stuff. I have ideas to build on myself.

Eric

[NeoTech]

To note from that video is that he uses a high performance fiber filled concrete for the base. And the polymerconctete is used for the saddle.
He does use some internal structures but most of it is just rebar bent and twisted and then welded to the anchoring points.
That will surely prevent ripout - but will it prevent fluid dynamics during resonance.?

The cnczone epoxy granite thread is mainly 600+ pages where the useful stuff is less than 20 pages. (i know i read em all, twice) ;D

There is actually several german and chezch builds with the material; polymerconcrete and high performance concretes.

And one thing that hits me after digging into this subject for the last 3-4 months - their machine bases is basicly completely dead in a resonance perspective.
Not even my half ton Aciera mill is that quiet many times when running a crab or a large endmill. =)

[sparky961]

I've come across this idea before in various threads but have yet to read exactly why you'd do this.  I'm just looking for the the main talking points, not trying to start an argument or debate on the merits.

[NeoTech]

Well why is a good question.
Mainly out of curiosity. And secondary because i exhausted ways of getting a 1-1.5t cnc machine into my shop by, just buying it.

I live in sweden, the country were logistics basicly stop at the border. I can find good deals in uk, holland and germany easily. And i can have them
shippe basicly to the border quite inexpensivly. (less than 2000 euro). But here we hit a snag. From the swedish border and home to me, its about
an 8 hour trip. For a like say a tormach with the more commong shipping companies that would run me an additional 4000-4500 euro.

And ontop of that they will want taxes for the import and such. A ok machine can be found for about 7500-10.000 euros no problem.
But when adding the shipping, im in a price range where buying a new one starts to be more affordable.

So i started researching alternative routes, and i knew i read the epoxy granite thread a while back, and i knew i have seen concrete machines in production
facilites i have visited before. So it seemed to be a valid route of doing things.

In the end i will have spent about 4500 euro on this, for that price i can even afford to make mistakes.
I have a small shop with a manual Aciera F3 and a small lathe, so i will be able to produce alot of the parts myself.
Only thing im a bit worried about is howto level everything properly.

[RotarySMP]

There is Silimix 282 from Euroquarz.de or Sikadur 43 from Sika. I contacted Euroquarz. The have no distribution network, but are happy to ship. Unfortunately shipping sand is very expensive.

Sikadur is sold as a system with the epoxy. It was used by Alpenheli.at for his gantry. He informed me it was about €7/kg back then when e made it.

I am still trying to source a fuller curve graded mix locally. Have you talked to local companies. The highest grades of concrete used in bridges (or at least in bridge repairs) also seem to use fuller curve graded aggregate.

I think the 2x theoretical improvement in rigidity gained by added all that steel would be much cheaper and more easily gained by simply increasing the profile depth of your E/G castings. One of the huge advantages of E/G is that it is a casting method which is not sensitive to changes in thickness or very thick sections (as cast iron is). Especially your base is not that thick relative to machine size. It would be very easy to add a few more cm in depth, maybe with some hotwire foam cut inserts to form ribs reducing the total E/G consumed, and thus acheive your stiffness goals. With the steel ribbed construction, you have to build the frame twice needing two very different methods to ensure alignment. Once in steel, then again the mould for the E/G. With some changes in profile depth you save a whole set of construction steps with no loss of performance.

The most active forum for practical E/G builders I found is CNCECKE.de (german language). Mineralguß is the german term for E/G. Nucky seems to have built the first one, and went on to make a business of E/G gantry mills. There are lots of other practicle examples of builds on there, including some which continued to post the performance of their machines in use.

[NeoTech]

Thanks, will see if i can find a local dealer for those aggregates or if a car trip would be needed. ;D

I joined cncecke.de - but it does not work well through translate.google.com - and every other thread i clicked on didnt have any post the last 365 days.
so couldnt actually find the nucky thread. And overall it seems the germans have the upperhand on us in this subject. All the really working machines on the tube is from germany as well. =)

And ridigity, actually i agree with you - but... (there is a but).. Epoxy is like 30x more expensive than steel, i can have inexpensive 240mc steel cut from 2mm sheet, and welded onto bar stock with a jig alot cheaper than it would be adding more volume to the casting.

That said - a ribbed construction isnt something i had considered yet. And maybe i can reduce the amount of aggregate that way - because 7 euro kg, i need about 160 litres of the stuff as is ( no idea what one litre of E/G would weigh in at )

[NeoTech]

Damn, i actually found Sika-43 in sweden.. *emailing companies* 

[RotarySMP]

Epoxy is more expensive than steel is not a very good argument

Granite should be nearly free (obviously not if we have to have 25Kg bags of it shipped from Switzeland, but there must be some way of getting correctly graded aggregate locally, especially in Sweden and Austria. They countries are made of Granite aren't they?

You only need 8-9% epoxy. So it's maybe 16L for your current design, or say 20L of epoxy, if you bulk up your castings a bit. If you can get the aggregate cheaply locally, those extra four liters are not going to cost more than a fraction of what the steel, plus cutting, blus assembly, plus straightening that the steel will need.

Sikadur43 is 2.0 kg/l according to the datasheet. If you can still get it for €7 /kg you are looking at €2240 for the casting.

Euroquarz said that shipping 50kg of Silimix 282 to Vienna would be €170, and 20L of Expoy can be had over Ebay for under €300.

Mark

[NeoTech]

Well, you could try to import Epoxy from ebay to sweden.. it would flagged in customs, confiscated and destroyed in those volumes.. (shitty country) something about enviroment rules and ****.. have tried it before - it was not a funny experience..

Granite is effin expensive here in aggregate form. Its common yes, and the companies crushing it knows its worth. Overall, you can take any price from europe or any other country and add a 0 on it, welcome to sweden.. =)

That "base" part is;  171500950.28 cubic milimeters.. i would get that to be around 171litres.. not 16-17 litres.. wrong?

Edited:
Pillar: 132656661.98 cubic milimeters (~132 litres)
Saddle: 26020000.00 cubic millimeters (~26 litres).

[RotarySMP]

Normally aggregate used in concrete is sold by the ton not the kg. You dont want crushed granite, you want the rounded stuff they dredge out of rivers. I am still assuming a local source can be found. 16L is the epoxy needed. I can get some graded 4-5mm pebbles, graded 0.8-1.2mm sand and  a couple other grades  at my local hardware store for about 4€ for 20kg. I am assuming if I drive the 40km to St Pölten when they produce the stuff and sell it in 1 ton bags to industry, I can get for next to nothing.

Why on earth would there be customs between Germany and Sweden? Haven't they heard that Sweden joined the EU a while back?

How do you plan to get the epoxy?

Mark

[NeoTech]

well, customs.. epoxy falls under chemicals, Sweden has weird ass rules about chemicals. So they will try to make it as hard as possible for you to buy and handle.
Then you have this, and its a common thing here. Companies doing buisness in industrial materials - dont want private customers. Its to much hassle, they just dont want
to deal with end consumers. So its not that the materials is not available. They are not just available to me, as a private consumer. Because im mostly headache to them. =)

I was planning to use this epoxy; http://www.nilsmalmgren.se/Datablad/DB%20Gjutharts%20094.pdf
Its a casting resin where i can buy 53kgs of it for around 1500 euros.

[RotarySMP]

Sounds like you should take a ferry to germany, drive to Euroquarz dorsten and pick up Silimix, and then on the way home pick up 30L of Epoxy from some german vender like
Marlies Breddermann Kunstharze

Otto-Hahn-Str.22

48480 Schapen

Germany

, and save about €3000.

Mark

[NeoTech]

I actually have to agree with you. A road trip would save me alot of cash.. Will just have to program a GPS and do a roundtrip bribing my other half with stops in some makeup store ;D

[RotarySMP]

"roundtrip bribing my other half with stops in some makeup store"

There goes the €3000 savings right there

[RotarySMP]

Your numbers add up to about a 650kg frame. What are you travels?

It sounds like your machine plan might be a little light. If it is about 180cm tall, it would be in a class where the industrial CNC machines are normally well over a ton. More like 2-5 tons if they designed for high dynamics (which your 1.5kW servos would imply).

Mark

[NeoTech]

Ok, i got it to about 825kg actually. But yeah its a bit on the light side actually.
And that something that have been a concern of mine., its about 1500mm from top to bottom.

The travels is
z: 425mm
x: 450mm
y: 450mm

And the motors, and screws would put the machine somewhere in the 500ipm atm, thinking of gearing the axels with belts and push about 1100ipm - not entirely sure if thats possible tho.

[sparky961]

Well why is a good question.
Mainly out of curiosity. And secondary because i exhausted ways of getting a 1-1.5t cnc machine into my shop by, just buying it.

<snip>

Thanks, that clears up a lot.

[RotarySMP]

Hi Neotech,

I found my post in the Monster CNCzone E/G :
http://www.cnczone.com/forums/epoxy-granite/30155-epoxy-granite-machine-bases-polymer-concrete-frame-8.html#post245588

This summarises a book I got out of the library.

Mark