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IndustryArena Forum > Mechanical Engineering > Epoxy Granite > Epoxy-Granite machine bases (was Polymer concrete frame?)
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  1. #1
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    Epoxy-Granite machine bases (was Polymer concrete frame?)

    Did anyone managed to build anything out of polymer concrete? I would be interested in your experiences and materials suitable for machine frames, tables, etc.

    Here's a nice looking polymer/epoxy(?) machine table called X2 Mini Mill base

    http://www.cnczone.com/modules.php?n...threadid=24879

    Do machine manufacturers use reinforcements in their frames?

  2. #2
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    its been discussed many times - search will find it, but i haven't seen a diy effort yet. I like the idea of a normalized fabrication filled with epoxy and stone as a machine superstructure... maybe one day will get to it, until then its hearsay, at least on my part. the worlds best tool manufactures do use it, hardinge for example or some of the extremely sensitive and precise optics equipment manufacturers, millionth of an inch stuff.

  3. #3
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    Yeah, I've seen the threads...Not much in there. I think I'm gonna buy a bag and experiment a little

    Do you think they use straight polymer concrete or the mix of many components, epoxy, etc?

  4. #4
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    try Google search."epoxy granite"
    Larry

  5. #5
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    I just noticed this material too and it has amaizing properties.
    yesterday I spent all day searching in google info about this material and found these 2 companys which make polimer comosite castings for industrial machines

    http://www.itwpolymercastings.com/
    http://www.accurescasting.com/index.html

    I send emails to both companys about their product prices and then will see if they will reply to induvidual (lot of companys work just with companys ignoring non company people )
    I want to experiment too with this material

  6. #6
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    ill tell you

    optical grinders,lathebeds,surface measurement columns bases,grinding beds heads,castings for centrafuges,lasers,high frequency test beds,milling beds columns heads laser engravers lots fabricated infills

  7. #7
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    Hi Roach,

    Welcome to the thread.

    You do know that you are going to be 'pestered' with loads of questions... I'll be one of the first...

    You mentioned lathe beds, well, I intend to use this material for a lathe bed.
    I am in the process of designing the lathe; I would like to build it so that I don't have a steel insert the length of the rails, I would like to have inserts present only for the mounting screws.

    My question is this: Is it simpler to construct a precise mold so that the linear rail beds are ready to receive the rails right away when the lathe bed is de-molded, or is it simpler to just post grind the E/Q (polymer concrete) before mounting the rails?

    Thanks and best regards

    sandi

  8. #8
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    Damping

    If we use an electrical analogy, the damping will determine the width of the peaks when we measure the resonant frequency of a component. It will also determine the rate of decay when we ring a bell.

    We could put a piezo tranducer at one each of a rod of our material. Put a signal in one end and display the signal at the other. Then sweep the frequency from low to high. Plot the signal amplitude as a function of frequency. The peaks we see will be the resonant frequencies of the assembly. Materials with low damping will have narrow peaks. Materials with high damping will have wide peaks.

    Instead of applying a sine wave at the input, apply an impulse. The output signal will be a pulse if the material is well damped. If the assembly is under damped, there will be a decaying sine wave.

    The various resonant frequencies will depend on the dimensions of the sample, the speed of sound in the sample, and probably lots of other things that I am ignorant of.

    If all you want is comparative information, that should be pretty easy to get with simple apparatus. Quantitative info is harder to get without calibrated transducers.

    [This stuff is off the top of my head. It might be partial or total BS. Feel free to tell me so. In fact, I insist.]

    Ken
    Kenneth Lerman
    55 Main Street
    Newtown, CT 06470

  9. #9
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    Episs
    Companys fabricating machine bases of epoxy granite are not in the business of selling the raw material.I did a lot of research on the subject and there is little to be found.Sand is basicly granite and probably a good filler.
    Idon't remember exactly the figures,but epoxy granite has 10 times the damping factor of cast iron and 50 times the damping factor of steel.
    THE COST??? 1gal. epoxy $80 Maybee 10 sq ft/gal/1/4 thick.Figure it out,its
    gunna cost mega bucks even with sand fill at 50%.
    This is just off the top of my head.If anyone wants more accurate figures I will look them up again.
    Any how I figured out a slab of real granite is 1/2 the price of epoxy granite,maybe less.A 4X8'X4"epoxy granite table top could cost 5or6 grand or more.A black granite surface plate 4X8'X8"with stand is $2600 from an E-Bay store.If anyone is still interested I will try to answer any questions or re-research my findings.
    Larry

  10. #10
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    Yes please continue- that's a very good info..

    I'm interested in all kinds of solutions.

  11. #11
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    EG Machine base

    I just came across an EG machine base on the CNC Cookbook site ( http://www.cnccookbook.com/ Blog 10/12/08) that referenced it to the German CNCZone site. The machine was described as a German Epoxy Granite Milling Machine and is made with R L & G epoxy resin. This looks like the finest example of a DIY EG casting. Is R L & G epoxy available here in North America ? We are looking to try this for the first time and we need to learn as much as possible about this process.

    Bruce

  12. #12
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    Hello Bruce,

    Yes, the Germans do some impressive work.

    I also experimented a little with the EG mixture closer to the beginning of this thread, and I used the Epoxy the Germans use: L1100 from R&G Epoxies.

    Now, I don't know if the R L & G epoxy that you have mentioned is the same as the one I have posted, but I think it is.

    I also don't know if this range of epoxies is supplied in North America...

    Regards

    Sandi

  13. #13
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    Hi Sandi

    Thanks for the response
    I haven't found a NA supplier for the same epoxy but there are many others, I'll need to determine what differences there are between them. How did your results turn out. What problems did you encounter ?
    We are looking to cast some lathe tailstocks.

    Bruce

  14. #14
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    Quote Originally Posted by lgalla View Post
    ...Any how I figured out a slab of real granite is 1/2 the price of epoxy granite,maybe less...
    Hmm...
    How about using some of those kitchen 5"x2" granite slabs?
    Should be relatively easy to put few of those "together" and encapsulate it with E/G...?

    (This could work for smaller machines, up to 3'x5')

  15. #15
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    Quote Originally Posted by lgalla View Post
    Episs
    Companys fabricating machine bases of epoxy granite are not in the business of selling the raw material.I did a lot of research on the subject and there is little to be found.Sand is basicly granite and probably a good filler.
    Idon't remember exactly the figures,but epoxy granite has 10 times the damping factor of cast iron and 50 times the damping factor of steel.
    THE COST??? 1gal. epoxy $80 Maybee 10 sq ft/gal/1/4 thick.Figure it out,its
    gunna cost mega bucks even with sand fill at 50%.
    This is just off the top of my head.If anyone wants more accurate figures I will look them up again.
    Any how I figured out a slab of real granite is 1/2 the price of epoxy granite,maybe less.A 4X8'X4"epoxy granite table top could cost 5or6 grand or more.A black granite surface plate 4X8'X8"with stand is $2600 from an E-Bay store.If anyone is still interested I will try to answer any questions or re-research my findings.
    Larry
    I got a a 2 x 4 block of granit for $100 at an auction. Nobody wants them and they are a pain to move. But they can be had reasonably cheap. Side note my block of granite came with a cmm. And threaded mounting holes.
    Richard

  16. #16
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    Hi there veteq Roy,

    The mass percentage of epoxy is useful only for measurement purposes. The volume percentage of epoxy is what determines the physical properties of the mixture.

    According to the compressible packing model from Francois de Larrard's <u>Concrete Mixture Proportioning: A Scientific Approach</u>, the maximum achievable aggregate percentage is 92% plus or minus 3%. Thus no mixture with more than 11% epoxy by volume could be optimal and no mixture with less than 5% epoxy by volume is possible. The model assumes vibratory compaction. Slightly better compaction is available with huge hydraulic presses but that isn't what we're about here.

    This model results from de Larrard are entirely consistent with Mr. Jolincks and the Ph.D. thesis of German Castillio (in French) from the Usinages group, and disagrees with the German group.

    There is no question that the German group has done some good machine engineering but I have always felt that their material design was suboptimal. According to their last post in this thread, the Germans are using the Fuller distribution which is demonstrably suboptimal providing at least 6% lower density than the optimal distribution and 5% worse than virtually every other common aggregate distribution. AS for your question about 17% by volume, see the <A href=http://www.cnczone.com/forums/showpost.php?p=444339&postcount=3119>nomograph</A> on pg 260 generated from a formula in A.J. Kinloch's <u>Advances in Resins and Structural Primers</u> and follow the cyan line to 83% aggregate=17% epoxy. You'll find that pine wood with a young's modulus of 2e6psi has a similar stiffness to that proposed E/G mixture. I have tested a few similar materials myself to failure in ASTM D790 flexural tests and gotten modulus numbers that match the nomograph results.

    The German group have shown that there is no problem working with a high-tech plastic-wood like formula but if you need stiffness for a large part, there's no substitute for using the optimal aggregate mixture. As long as you can do engineering analysis either on paper or FEM to ensure that you meet deflection and strength criteria you could build a machine out of a suboptimal E/G like the one you propose. The amount of epoxy needed is that amount which fills the voids in the aggregate and perhaps a tiny bit more to aid in processing. The perfect epoxy is a lot less important than an aggregate distribution that achieves a density of at least 92% when compacted.

    The vibration numbers I have seen cited in both Castillo and de Larrard suggest that the entire mold must be vibrated at between 2g and 4g at 50 or 60 hz. This is a somewhat difficult proposition for the average contributor here. In general, the longer the mixture is vibrated, the more it compacts. What you can get away with depends on the pot life of the mixture. Most of the epoxy formulations I have considered reasonable have pot lives in the 4-8 hour region and it's almost certain that vibrating this long cannot be good. I have only made small samples with minimal vibration so far so I can't shed any light on the right way to do it. My only certainty is that to make a single production quality E/G machine requires more capital that getting a whole bunch of cast iron and scraping it.

    If you are using a suboptimal aggregate mixture, it will segregate and as a result, there is a balance between vibration time and compaction. The de Larrard Minimum-S mixture is ideal as it can be vibrated with limited segregation but I don't have my compressible packing model code implementing it correctly right now so I can't solve the general case for arbitrary aggregate.

    There are huge 220V 3 phase vibration motors available but they are expensive. I have a 3 horsepower unit over at my lab that I found surplus for maybe 1/5 the cost of a new one. I think it's 15 Hz by default but with a nice VFD, I should be able to get it up to 30Hz or a bit more. A standard concrete vibrator is too small by all accounts I have read. The 3HP unit I have weighs 400 lbs and the rotors are so heavy I can barely spin them with my foot. The problem is that you need a sturdy table to which you can attach the vibrator and isolators so that you move only the table, vibrator and contents without trying to move the building the vibrator is in. A large steel plate for the table and the vibrator itself will add substantial weight to the weight of the part in your calculation. The deflection will also be based on the weight of the table and the stiffness of the springs on which the table rests. Stiffer springs will provide less deflection and less isolation from the building.



    Material Design Conclusion:

    If you would be confident in holding the desired deflections on your machine if it were made of softwood like pine, your proposed material design is sufficient. This is a very good approximation as the moduli are almost exactly equal between pine and epoxy-rich E/G. Approximately 2.5 times better stiffness would be available with an optimal material.

    On Vibrators and Vibration:

    With regards to your second post about building a vibration system, it is my opinion that your 3rd design has the potential to fail catastrophically. The reason that commercial vibrators are expensive is that they have huge bearings and are very heavily built. The forces at the bearings of an off balance rotating item are astronomical. I have reservations about the third drawing because you have the rotating mass rather far from the bearing. This will tend to cause cantilever deflection in the shaft and I would worry about catastrophic failure of either the shaft itself or the bearings. The bearings of a precision motor are not built to handle the abuse of running as a vibrator for long but the setup is probably sufficient for a one-off. If you are okay with the potential of catastrophic failure and loss of the motor, make sure to build a sturdy containment housing to catch the airborne parts.

    With regards to the calculations, I see nothing wrong with what you have done but I think your weight estimate of the entire setup might be too low. Pay special attention to the section on isolation in the Deca vibrator page you cited. This static system deflection that they cite is the amount that the vibrator, table etc deflect the springs that it rests on due to their weight. The numbers that they give here are a surrogate for solving the second order differential equation of motion for the vibration table. See <A href=http://www.thevmcgroup.com/springmounts.html> The VMC Group</A> web page and get a copy of the Korfund Dynamics Catalog under downloadable PDF's to get a better feel for what you might need.

    Also note that commercial vibrators have adjustable rotors that allow the amount of off-balance to be adjusted by controlling the angular separation of two parts of the rotor. The page you are designing from seems to assume you will use this adjustment to correct the operation of the system into the nominal parameters.

    With the type of motor you are proposing, I think I personally would want to belt drive the off balance rotor and house it separately in a housing with very substantial bearings. This would at least preserve the motor should something fail.

    At any rate, I wish you the best of luck in your endeavor and think I can speak for everyone when I say we look forward to hearing about your progress.

    Regards,
    Cameron

  17. #17
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    Quote Originally Posted by lgalla View Post
    .Sand is basicly granite and probably a good filler.
    ...
    Guess again. Sand can be derived from many rocks, including granite, but if you buy a bag of "sand", you probably get primarily quartz sand (silicon dioxide); at least in the continental US. I have personally experienced black lava (basalt) sand, green olivine sand, and white coral sand in their native environments (Big Island, Hawaii); these aren't what people mean when they talk about sand and thus have prefixes as qualifiers. Real epoxy quartz is another contender but not the same as epoxy granite and has different properties. Sand, of any sort, is not that good a filler by itself, you want a variety of sizes of material and shape matters, too. If you use sand, you are likely to end up with a result that more resembles the properties of epoxy than that of rock. Oh, and 50% aggregate fill is ridiculously low and would have lousy properties, though if all you used was sand you would have a hard time getting a reasonable fill ratio. Epoxy sand would be useless structurally but would provide some damping as a filler material but would cost more than epoxy granite due to the poor fill ratio and high epoxy content. Done right, the aggregate is not a "filler" - it is the primary constituent and epoxy is the filler - it fills in the gaps between particles, holds them together, and contributes viscoelastic damping.

    Granite is not the same as epoxy granite. The mixture of a rock material and a viscoelastic polymer material has some damping advantages. Granite doesn't mold, it is hard to machine to shape and cut holes in, etc. and surface plates typically hold their flatness specs with smaller loads than would be encountered in a machine tool and aren't designed to handle the weight. Surface plates come in more or less flat slabs that have lousy strength to weight ratios. You want a honecomb/waffle/ribbed design or you end up with a machine that is too flimsy or too difficult to move, or both.

    You haven't suggested anything that hasn't already been discussed.
    There are over 50 pages in this thread alone and there were prior threads. Overwhelming, yes. But it is even more overwhelming for the next guy who has to read 50+ pages plus yet another rehashing of worn out ideas and errors that have already been dispensed with. Read and learn.

  18. #18
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    used granite surface plates

    Quote Originally Posted by lgalla View Post
    Episs
    Companys fabricating machine bases of epoxy granite are not in the business of selling the raw material.I did a lot of research on the subject and there is little to be found.Sand is basicly granite and probably a good filler.
    Idon't remember exactly the figures,but epoxy granite has 10 times the damping factor of cast iron and 50 times the damping factor of steel.
    THE COST??? 1gal. epoxy $80 Maybee 10 sq ft/gal/1/4 thick.Figure it out,its
    gunna cost mega bucks even with sand fill at 50%.
    This is just off the top of my head.If anyone wants more accurate figures I will look them up again.
    Any how I figured out a slab of real granite is 1/2 the price of epoxy granite,maybe less.A 4X8'X4"epoxy granite table top could cost 5or6 grand or more.A black granite surface plate 4X8'X8"with stand is $2600 from an E-Bay store.If anyone is still interested I will try to answer any questions or re-research my findings.
    Larry
    If you follow the auctions you will find used surface plates quite cheap. (I got a 3 x 5 for $50. Moving it was real fun though) Epoxy based is crazy expensive. Better to play with concrete.

  19. #19
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    Walter thanks for showing some interest.Also check www.moglice.com.Interesting stuff.
    Why epoxy granite?It takes 4 to 6 months to develop a machine tool of traditional cast iron.After casting,it has to age for 4 months to releive stress before being surfaced and then get heat stress relief.Cast epoxy/granite can be ready in one week with coolant lines and other inserts or ways moulded in.As I stated before Epoxy/granite is super $$$$,But a machine tool manfacturer can save tons of money from the time saving and have better properties than cast iron.As stated in geoligy reports granite was stress releived billions of years ago.
    Also companys are filling weldments or machines made of steel tube to eleminate resonance.Since epoxy has 0 VOC or solvents,when filled it has ZERO shrinkage.If you poured raw epoxy on the floor it will self level to .005 or better.What a way to get an accurate table surface to measure and build your machine on.
    I am in the composites business,Know little of CNC stuff,but have knowledge of fillers and micro packing.
    BTW in my business polymer concrete is out of date Polyester resin mixed with rocks for garbage cans and parking lot thingies.
    Never Never get the idea I'LL use polyester or fiberglass resin as a bonding agent.It just shrinks too much and is extremely brittle.
    Walter thanks for expressing interest,all the research time seems worth it.
    I am not discounting the hobbyist use of the materials as they cost so much,but will not recommend usage until I am sure of performance.
    Wow thought this would be short as I am swamped with orders righ now And
    don't have much time.I am guilty of going on and on.I have tons more info on the subject if you want to hear more.Let me know if your intrest is still there and I will try to post something {short}daily.Questions are welcomed,Hope I can answer.
    Larry

  20. #20
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    Hear I go again replying to my own post.I am not good at typing so lets give epoxy granite an easy name to type.Fourtwith epoxy granite shall be nameth
    E/G
    Larry
    E/G sweeper

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