584,316 active members*
6,650 visitors online*
Register for free
Login
IndustryArena Forum > Mechanical Engineering > Epoxy Granite > Epoxy-Granite machine bases (was Polymer concrete frame?)
Page 77 of 253 2767757677787987127177
Results 1,521 to 1,540 of 5053
  1. #1521
    Join Date
    May 2003
    Posts
    792
    Quote Originally Posted by ckelloug View Post
    Walter's old standby, the cary company, carries the 3m fluoro-surfactants. I'm not up on fluoro-surfactants at the moment.
    Cameron

    Aye,Aye Sir! I will pay them a visit.

  2. #1522
    Join Date
    Apr 2007
    Posts
    777

    OT: Why I'm here lest anybody think I'm up to something

    Jay,

    The rocket science comes in figuring out how to do it in a DIYable way. The beauty part of theory is that it allows you the knowledge of a thousand epoxy pours without having to spend the time. Once it's figured out, then it ought to be pretty easy for any of us to make. It's figuring out the ratio between eye of newt and toe of frog that seems to be the issue or perhaps the incantation: Is it "double, double toil and trouble" or "fumble, fumble, compact that bubble, fire burn and mixer rumble".

    FWIW, I'm here because I thought of the idea of concrete machine tools on the way home from breakfast one morning. I googled for it and found walter's thread. I happen to have some machines I'd like to build someday that aren't routers.

    I have a degree in general engineering from Harvey Mudd College class of '97. I come from a very open academic culture and the software engineering tradition of open source. I felt it would be nicer to add the information that I can provide to this thread to what was here than to take all of the information the thread had already come up with before I got here and then go construct another secret formula.

    As for what I get out of this thread besides some interesting discussion (and the fact that working on this problem is fun for me) is a chance for me to review materials science for a research project I started last year in an area outside my immediate expertise.

    Because of the wonderful discussions on this thread and the chance to work out a bunch of stuff and explain things clearly, I was recently able to articulate an idea I had on a totally unrelated subject for submission to the U.S. Defense Advanced Research Projects Agency, DARPA. (I work for one of the largest not for profit research companies in the country). I must also say that I just got off of two months of sabbatical and needed something to do besides solo construction of a 24x14 machine shop, re-roofing a section of the house, installing a sprinkler system, and replanting my lawn.

    In that a lot of people obviously want E/G and the company around here is pretty darned good for an eccentric engineer, I just can't resist the challenge. In short, this is what I do for entertainment. It is at least pi times the fun of watching American Idle/Idol

    If you'll pardon me, I need to get back to looking at the RF signal distribution I need to be looking at.

    Regards to all and thanks for continuing to post and share here!
    Cameron

  3. #1523
    Join Date
    Dec 2004
    Posts
    1137
    Damn, 2 for 2. I wasn't insinuating "ulterior motives" That's twice I've been misinterpreted .. .I'll quit while I'm behind. Ok, maybe not. I wasn't criticizing you Cameron ... more in awe of the amount of resources you've poured into this thread with no real stated goal. Most guys are here to see if E?G is the future of DIY machines I think. It's still unproven.

    As for me, my interest lies in the "is it feasible" question. I mean it's possible to build a lathe and mill from scratch using Gingery methods but not many can or do. So while it may be possible to "pour" a machine ... is it worth it (time, money, results) compared to other options. at this point, there are no other options for me that I can see other than Harlow's X2 base ... but that's a different thread.

    Keep on keeping on. I'll skip the engineering posts and keep looking for the pictures of success. Maybe I'll join the German thread to see how they are getting on.

    FWIW,
    Jay

  4. #1524
    Join Date
    May 2003
    Posts
    792
    Quote Originally Posted by Jay C View Post
    None of this is meant as an insult, more of an "ah, ok, I see now and can cut Dwayne some slack"
    Jay
    Quote"I myself have visited the monster polymer concrete/ epoxy granite thread (1500+ replies as of today) ... and well, no one is even close to doing what Dwayne has shown except for some German guys, and one US company that tipped their hat, but disappeared.. In fact, the closest anyone has come is filling their RF45 base and column with epoxy granite/quartz. It's mind boggling the amount of research and discussion from some seemingly intelligent folks but nothing to show for it" End Quote


    Let me explain, why taking vendor's side and standing against the little guy makes you look bad.


    You see, the only "research" vendors do, is to how to get in your pocket, repackaging something they bought for 10 cents on the dollar. Plenty of them trolling these boards. There's the one who sells 3 Geckos with power supply bolted to aluminum box for $2500.( Must have been quite a research )

    So, there are vendors and there are the hobby folks, like us, who spend many months learning, testing, and finally bolting their own 3 Geckos and power supply, for $500. See the difference?

  5. #1525
    Join Date
    Jun 2003
    Posts
    2103
    Hi guys,

    I've only posted once or twice on this thread but have watched it off and on. Because of that off and on watching I don't know what all as been discussed, so this question may have already been discussed, and if so disregard it.

    Has RTM been discussed as a means of introducing the resin to a closed form already packed with agg? If the form (mold) was positioned so that the intake was higher than the outlet, gravity would assist in the transfer process. No vibration, no heat and no mixing of the agg and the resin. Now a question arises as to whether or not the fly in the honey problem would exist in this process or not????

    Mike
    No greater love can a man have than this, that he give his life for a friend.

  6. #1526
    Join Date
    Apr 2007
    Posts
    777
    Jay,

    No offense taken. After getting flamed here a while ago however, I just wanted to be clear on my motives which have gotten more complicated as I actually started learning about this subject. I'm having fun and learning stuff which helps me. I've not got any actual materials yet, just reading materials of which you can never have too many. Not having my shop done means that I can't pour blocks yet.

    Some vendors like Accures have put large amounts of engineering time into making excellent reproducible products. I talked to them when I noticed an error in one of their datasheets. They're nice guys and they're in business to serve people who afford $60,000 molds and forklifts to move the 100's of resulting 1 ton parts by selling machines we home shop folks will lust for but never will need or be able to afford.

    Other vendors bolt stuff together that we could have done for ourselves. These are the aggrevating ones.

    A poster on another board PMed me and said that accures makes harlow's parts. Unless harlow has a huge research staff, it is better for him to use Accures and better for the community that they are able to get mill tables that would be unobtainable if harlow was waiting for us. . . Time is money if you need to sell machines to eat.

    Time isn't money if you are doing the work for a hobby or for the power of obtaining the knowledge.

    Even with an optimal recipe, making the E/G parts for a home-built machine will be some work that not everybody wants to do. Some people want to buy machines to make something. Others want to make machines. Others want to make machines because they can't afford or find what they need.

    While Jay has my art of saying the wrong words for an obvious concept, He has made good points.

    I'll conclude here by saying that vendors who have worked hard to create their products are as much an asset to the community as we are even if we cannot afford their products. In engineering economics, it's true that you should never make what you can buy cheaper. There is no shame in paying money to somebody like Accures for materials or parts because they did the research: You get the benefit of that research without paying for the whole research program and without having to worry if you "got it right".

    Go forth and find me a material and I'll guarantee that epoxy will develop a new material parameter to avoid sticking to it.

    --Cameron

  7. #1527
    Join Date
    Dec 2004
    Posts
    1137

    Smile

    Quote Originally Posted by walter View Post
    Let me explain, why taking vendor's side and standing against the little guy makes you look bad.

    You see, the only "research" vendors do, is to how to get in your pocket, repackaging something they bought for 10 cents on the dollar. Plenty of them trolling these boards. There's the one who sells 3 Geckos with power supply bolted to aluminum box for $2500.( Must have been quite a research )

    So, there are vendors and there are the hobby folks, like us, who spend many months learning, testing, and finally bolting their own 3 Geckos and power supply, for $500. See the difference?
    There are both kinds here. Sometimes you are willing to pay for convenience. I see nothing wrong with dealers packaging free information into a kit. If someone is willing to buy it ... good for both of them. I must be missing something about Accures. So what if Harlow buys his casting from them? If he can supply bases at the price he's advertised then all the better I'd think.

    Can you name any other options for expanding the X2 working envelope. Again my post in Harlow's thread pointing back to this one was to show the difficulty of the task (both to myself and to the others). I would think that'd be a compliment (I know I'm 3 for 3 in striking out on this ... maybe I'm being too direct). I mean there are 1500+ posts from all manner of experts all over the world working on this ... yet no visible progress. A Google search reveals some big CNC centers that use polymer concrete bases but nothing in the range I'd consider hobby (or hobby budget ). Do I want Harlow to succeed ... yes I do. Do I want the guys on this thread to succeed ... yes I do.

    And with all that said (hopefully I've cleared the air this time :rainfro I will slink back to lurk mode.

    Ok, one final note ... I got hooked on a project like this in the RC hobby of building CD ROM motors. I was so hooked I helped write magazine articles, build databases, write simulators, and author tutorials. Did companies profit from my free work ... I sure hope so. But I wasn't looking to start my own business and gave the information freely. If you post it publicly, then it's free to use by anyone. If a P.T. Barnum can price a few components for 5 times their retail value and the hordes buy it ... or put another way a fool and his money are soon parted.

    FWIW,
    Jay

  8. #1528
    Join Date
    Jul 2005
    Posts
    12177
    Quote Originally Posted by walter View Post
    ....You see, the only "research" vendors do, is to how to get in your pocket, repackaging something they bought for 10 cents on the dollar. Plenty of them trolling these boards. There's the one who sells 3 Geckos with power supply bolted to aluminum box for $2500.( Must have been quite a research )

    So, there are vendors and there are the hobby folks, like us, who spend many months learning, testing, and finally bolting their own 3 Geckos and power supply, for $500. See the difference?
    Nonsense; you generalise far too widely here. Yes I know about the class of vendors who mark something up outrageously; I have had it happen to my product, however, they are in the minority in my experience.

    Tarring everyone with the same brush is not valid criticism.

    Furthermore you give no evidence that your example is valid; how many hours do you spend doing your example for $500? Perhaps $2500 is a fair price for what is being provided; to some people time is money. Obviously if this vendor has had sales at that price his customers must consider the price fair.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  9. #1529
    Join Date
    Jun 2005
    Posts
    1425
    Some time back I posted my thought that spinning the mold might be worth considering as an alternative to vacuum de-airing.
    I've been considering all the posts concerning the complications of doing that, the surfactant required, the equipment, both container and pump etc. and decided to look again at my spinning(centrifuging) idea.

    Consider this. There are two forces on a bubble in the epoxy. The air pressure and buoyancy. The first exerting a pressure of 14.7 lbs/sq in downward, which in the case of a small bubble is a pretty small force, and the second, upward, coming from the effect of gravity trying to pull the epoxy column above the bubble down.
    If we remove the air, the bubble will expand, and its buoyancy will increase, allowing it to rise faster.
    However this change in the forces on the bubble is very small.
    If, however, we spin the epoxy mix, the effect of increasing the force of gravity is somewhat larger.

    Just to get a handle on some figures - if the mix is in a container 6" in diameter, and is spun at 600 rpm, the force on it is 60 G.

    Until I try it I can't be certain, but I suspect the bubbles will travel to the axis a lot faster than in a vacuum chamber with the mix at a similar depth.

    I also think that building a suitable piece of kit to do this is a lot more practical than trying to equip my old cement mixer with a vacuum pump !

    John
    It's like doing jigsaw puzzles in the dark.
    Enjoy today's problems, for tomorrow's may be worse.

  10. #1530
    Join Date
    Jun 2005
    Posts
    1425

    E/G sample testing jig No.2

    My mark 2 testing jig.
    While I'm only drawing a schematic, I want to keep the construction as simple as possible. The idea is that all should be able to fabricate the final version with simple tools and the sort of material that they shoud have no difficulty in obtaining.

    For example laser pointers are available just about anywhere now, and will replace a complex optical construction. The front silvered mirrors are commonplace in photocopiers/scanners etc so the scrap bins should be able to provide. The pivot is a darning needle, and the flat spring could be an old clock spring, a piece of steel flexible tape, or a relay leaf. etc. etc.......

    I've got rid of my double mirror for reasons of ease of adjustment. The idea is to have two or three weights in order to plot a short graph of displacement/ weight for any sample.
    I'll try and compute the laser spot movement for a given displacement later.

    John
    Attached Thumbnails Attached Thumbnails flex test 2.jpg  
    It's like doing jigsaw puzzles in the dark.
    Enjoy today's problems, for tomorrow's may be worse.

  11. #1531
    Join Date
    Jul 2005
    Posts
    12177
    Quote Originally Posted by greybeard View Post
    Just to get a handle on some figures - if the mix is in a container 6" in diameter, and is spun at 600 rpm, the force on it is 60 G.

    Until I try it I can't be certain, but I suspect the bubbles will travel to the axis a lot faster than in a vacuum chamber with the mix at a similar depth.

    I also think that building a suitable piece of kit to do this is a lot more practical than trying to equip my old cement mixer with a vacuum pump !

    John
    Your 60 G may or may not be correct, what is it omega to the power of 2 times R with omega expressed in radians per second. I think you may have used diameter instead of radius because I come out with 30G.

    Even so the mind boggles a bit at an old cement mixer spinning at this speed.

    And you need to consider the forces on your centrifuge, this idea works because you have effectively increased the density of the E/G. You will need a sturdy container.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  12. #1532
    Join Date
    Jun 2005
    Posts
    1425
    I took the easy way out - I used the www.centrifuge.jp page to do the calculation for me, so I assume it's correct

    I wasn't contemplating using the cement mixer, just another piece of plastic drainpipe, especialy as I am also thinking along the lines of batch working.
    I think 600rpm is hardly fast, but perhaps that's the way I drive.

    Mind you, the possibility of a continuous feed revolving drainpipe with the mix going in one end and coming out the other.......

    Regards
    John

    EDIT - SORRY Geof - it was my conversion of cms to inches let me down - I converted 15cms to 3" as the radius, then doubled that (chair) (chair)

    Edit 2 Could someone do the calculation on the bouyancy of say a 1/8" bubble under 1" of epoxy and vacuum ? It's beyond me I think.
    It's like doing jigsaw puzzles in the dark.
    Enjoy today's problems, for tomorrow's may be worse.

  13. #1533
    Join Date
    May 2003
    Posts
    792
    Quote Originally Posted by Jay C View Post
    None of this is meant as an insult, more of an "ah, ok, I see now and can cut Dwayne some slack" type of epiphany for both myself and the guys that have ponied up some money over the past 6 months. Or in short ... this ain't easy

    FWIW,
    Jay

    So, let me get this straight..

    Your vendor didn't invent anything- he's buying E/G kits from another vendor, bolting stuff together, and your lead time is what.. 6 months?
    Hmm. We're only 5 months into this.. And, we're not using anybody's kits, we're trying to invent the thing. From scratch.

    Plus we're pretty dysfunctional here, and this is not a paid work- no wonder it takes so long lol. But we're enjoying it and wouldn't want it any other way Those of us who know everything about Epoxy/Ganite have never touched Epoxy. Those who did touch it aren't doing any sampling, and the guy who is doing the sampling has no knowledge whatsoever and is totally lost We really are awesome, and our readers agree... It's a great entertainment and we have readers around the globe! Just check out the Google rankings- we are a farse to be reckoned with.


    Now I don't have anything against Harlow. I do hate vendors- but nothing against him. He has something special and I think he's a hero; anyone who brings composite machines to the masses is a hero. That is my opinion and will not change.
    This E/G stuff is awesome and there is simply nothing like it. And him bringing top notch Accures product in this great little form factor is extremely cool and also very brave.

    I was the first one to link to his thread (see post #1 of my thread), and I think his X2 base is one of the best looking things on the Zone. There you have it.


    As for the Geof's comment... I think he understands the market and knows that you set the prices according to whatever people will bear and that's that. And $2500 for 3 Geckos and power supply bolted to piece of aluminum is definitely a fair price



    D
    ysfunctionally yours,
    Walter

  14. #1534
    Join Date
    Jun 2005
    Posts
    1425
    I've just done some calculations re my post #1530 on the forces on the bubble, and I think I've got it horribly wrong.
    Is the effect of air pressure on the bubble far greater than the bouyancy that is due to the density of the epoxy mix above it ?
    Not what I expected.
    Just shows how easy it is to jump to the wrong conclusion if it's the result you want.
    Ho hum.
    Could someone confirm one way or the other ?
    I'm going to bed, somewhat chastened.
    John
    It's like doing jigsaw puzzles in the dark.
    Enjoy today's problems, for tomorrow's may be worse.

  15. #1535
    Join Date
    Jul 2005
    Posts
    12177
    Quote Originally Posted by greybeard View Post
    I've just done some calculations re my post #1530 on the forces on the bubble, and I think I've got it horribly wrong.
    Is the effect of air pressure on the bubble far greater than the bouyancy that is due to the density of the epoxy mix above it ?
    Not what I expected.
    Just shows how easy it is to jump to the wrong conclusion if it's the result you want.
    Ho hum.
    Could someone confirm one way or the other ?
    I'm going to bed, somewhat chastened.
    John
    I think you are correct that the bubbles do get driven up with a greater bouyant force if you spin it. The bouyant force depends on the pressure differential between the bottom and top of the air bubble; in a centrifuge the pressure gradient is enhanced because bottom is at a larger radius than top.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  16. #1536
    Join Date
    Apr 2007
    Posts
    777
    Greybeard,

    I'd think about using water instead of weights in you Mk2 jig. Everybody can measure water but weight takes a scale. You need to go all of the way to failure to find flexural strength while you only need a regular set of weights vs. displacements to find flexural modulus. I'm a bit vague form the diagram about how the needle suspension of the mirror and the adjustments work.

    As for the bubble in a vacuum question, like many of your questions it sounds simple but it isn't. These are the questions we learn from as I have from all of your other questions.

    As best I understand it which may be flawed, please correct me if I blow this completely: There will be the unbalanced pressure of 14.7 psi + the hydrostatic pressure caused weight of the epoxy column above the bubble in the upward direction on the top hemisphere of the bubble. As the bubble rises, it will be under less epoxy so the hydrostatic pressure will go down causing the bubble size to increase as it rises. Fluid dynamics will have to be invoked to figure out how fast a sphere moves through liquid except that it is changing size. Buoyancy will also need to be involved. I think that there is actually a retarding component of the bubble's movement speed upward in the column that is proportional to my favorite new parameter: surface energy.

    The problem is bad because it involves a sphere (that's not actually spherical) with a depth dependent volume moving in what I would assume to be turbulent flow in a viscous liquid driven by the pressure differential between it and a vaccum (which is also changing with depth due to the volume change) which is retarded slightly by losses caused by having to overcome the surface energy of the epoxy as the bubble expands.

    It sounds like a good masters thesis to me. I have attached the buoyancy equation but it's true whether or not there is vacuum.

    I would assume that to first order, you could model the vacuum contribution initially as 14.7psi of pressure equating to a force on a circle the same diameter of the bubble creating an upward force opposed by the weight of the bubble and the weight of the epoxy above it.

    I've stolen the buoyancy equation form the wikipedia but the value for density of the bubble won't be constant. If there are any nobel laureates with computational fluid dynamics software in the house, this sounds like a great thing to assign to a grad student!!!

    All I can say is that I think I'd rather have something under vacuum even with the morass I see above than 5kg of epoxy granite spinning at 600 rpms. The latter should make some nice molded in place architectural molding however.

    --Cameron
    Attached Thumbnails Attached Thumbnails buoyancy.png  

  17. #1537
    Join Date
    Apr 2007
    Posts
    777
    Turmite,

    Resin transfer molding has been discussed briefly at times here but it hasn't taken root yet. It's a good idea but as of yet, nobody has dropped the dollars on a vacuum pump. It will likely come up more later and your comment serves as yet another reminder that it should as soon as anybody has tried a formula with the proper additives.

    Welcome back turmite and make sure to post any more ideas!!!

    Regards,
    Cameron

  18. #1538
    Join Date
    May 2003
    Posts
    792
    That's it. I'm getting that pump. (chair)

  19. #1539
    Join Date
    Jul 2005
    Posts
    12177
    Quote Originally Posted by ckelloug View Post
    ... Buoyancy will also need to be involved....I would assume that to first order, you could model the vacuum contribution initially as 14.7psi of pressure equating to a force on a circle the same diameter of the bubble creating an upward force opposed by the weight of the bubble and the weight of the epoxy above it.....--Cameron
    I think you are making it more complicated than necessary.

    Buoyancy is all that is involved as the driving force, the retarding force is much more complicated having to do with viscous drag and other imponderables.

    Viscous drag depends on the viscosity of the fluid and viscosity can be reduced by heating but that is about all you can do on that side.

    Buoyancy depends on the difference in density between the ascending bubble and the surrounding fluid which largely depends on the size of the bubble and local gravity which provides the driving force.

    When dealing with a pre-existing bubble the size can be controlled by pressure so all applying a vacuum does is make the bubble bigger and less dense.

    Using a centrifuge simply increases the local gravity. Greybeard's suggestion would work but it could be difficult to implement.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  20. #1540
    Join Date
    Apr 2007
    Posts
    777
    Geof,

    You're correct that my modeling effort on the bubble was way too complicated. I wrote it mainly trying to show that the number of imponderables involved seemed to outweight the simple value of the buoyancy. It does however show that there exists a depth of epoxy for which vacuum deairing is theoretically impossible.

    I'm not so sure that graybeard's solution will work well, not because centrifugal (pseudo)force won't compact the mixture but because I think vacuum is the only way to get rid of adsorbed air in addition to bubbles.

    I'd settle for any deairing method that worked at this point but I personally am planning on deairing with high vacuum once I get my shop completed. If John gets his centrifugal deairing system to work, I'll doff my cap to him but in my shop, I suspect that I'd end up with a nice epoxy-granite chair rail lining the wall as the epoxy escaped when I forgot to screw something down tight. If I could sell epoxy granite chair-rail, I'd think it pretty cool but I don't think so.

    Vacuum may suck but I personally like it more than spinning drums of epoxy.

    Regards to all,

    --Cameron

Page 77 of 253 2767757677787987127177

Similar Threads

  1. Replies: 71
    Last Post: 08-25-2020, 01:18 PM
  2. Replies: 14
    Last Post: 11-13-2015, 02:57 AM
  3. Replies: 9
    Last Post: 01-15-2014, 11:39 AM
  4. Index to "Epoxy-Granite machine bases" thread
    By walter in forum Epoxy Granite
    Replies: 13
    Last Post: 12-02-2011, 05:45 AM
  5. Epoxy-Rice Machine Bases (was Polymer rice frame?)
    By mdierolf in forum Mechanical Calculations/Engineering Design
    Replies: 18
    Last Post: 11-02-2008, 04:16 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •