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Concrete filled C-Beam?

Discussion in 'Concepts and Ideas' started by trentaw, Jun 8, 2016.

  1. trentaw

    trentaw New
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    Just throwing the idea out to see what others think. What if I were to close the open side of the C-Beam with some plate, and then fill the interior with concrete? This is similar to what Taig does with their lathes, I believe. I would do this in hopes of strengthening the machine and possibly get some vibration dampening out of it. Any comments?
     
  2. Karl Miller

    Karl Miller Well-Known
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    take a look at CNCCookbook's diatribe on epoxy granite polymer.
     
  3. trentaw

    trentaw New
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    Just took a look. That is exactly what I was talking about. So it does seem to help, but I was more concerned about limiting the functionality of the C Beam. What I mean is; as far as out of the box attachments go, would this limit their use? Would it cause aggravation further down the line in the build? Or would it be of little concern?
     
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    For what you are suggesting, you would probably be better off stacking 2 40x40 sections, bonding them together and then filling the cavities with the epoxy granite polymer. This gives you a much more balanced section, it has greater fillable area, and the polymer gets closer to the faces where it does the most good. You also don't lose a face to the additional plate so there are no obstructions to any gantry system that grips around the perimeter.


    [​IMG]
     
  5. Karl Miller

    Karl Miller Well-Known
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    I am also working on a design that would use the E/G. I am focusing on the base of the machine and the stationary axis because I am unsure of the change in chacteristics it would put on a moving axis (the one I think of as the Y axis)... i.e. I would think it would add too much weight for that Y axis to keep moving all that weight around for those two steppers (my electronics are limited to the CNC xPro board and 2 amp steppers). I would think deflection wouldn't be an issue, but I imagine the steppers running hot and not keeping up in my scenario.

    The way I intend to use the E/G is as a truly flat and level base on top of four equally sized 2x3 steel 11ga tubes all arranged in a box (5'x5') with each laying on their sides so the 3in sides are facing up, and each corner welded at 45deg and the whole base filled with E/G. Once those tubes are filled and welded together, I would form a one inch layer of E/G on top to form one big 3in x 1in frame on top of this tube box (after leveling it as good as possible).
    The E/G would settle to be a perfectly flat and level reference surface for the gantry system. I will be embedding large tapped bolt thread inserts about every foot, on which the X axis will be mounted. These bolts will allow for adjustable vertical movement of the X axis which can alleviate that last 1/100th of an inch adjustment.
    I am also going to embed heavy L brackets in this base on which to secure the X axis. These will secure to the T-slots on the lower inside of the X axis on both sides.
    I believe this machine should survive the big earthquake coming from Yellowstone.
     
  6. Karl Miller

    Karl Miller Well-Known
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    BTW - for anyone not using their machine for a water table for plasma cutting, E/G can provide a great base on which to 3D print (because it settles into a super flat surface). That would probably be a lot easier and cheaper than having on big slab of metal surfaced to be true / flat. Embed some I threaded inserts and you can use it as an inexpensive way to make a really flat spoiler base (mount T-tracks to it).
     
  7. trentaw

    trentaw New
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    @Rick 2.0
    I like that idea. Any recommendations on how to fasten the two together?
    @Karl Miller
    I'm interested in your machine design. I would love to see it when it's finished. Though, I wonder how the epoxy would stand up to cutting fluid or any solvents that may happen to get on it.
     
  8. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    If I was doing it, I'd probably print out a bunch of V-slot Connectors in 1" lengths, mix up a substantial batch of JB Weld, and then start packing it all down the slots of the mating surfaces, alternating between plastic connectors and enough JB Weld to create a fully filled 2" plug as the next connector was packed down upon it. The plastic joiners are basically there to hold the two sections tightly together and in proper alignment until the JB Weld sets up which then becomes the true strength of the connection.

    Please note, I've never tried this. But if I were needing to combine two sections, this is how I would go about it. There are probably other ways to achieve the same goal. The simplest solution would be to put a good epoxy on the mating surfaces and use the connectors to hold it together until the epoxy cured. The problem is finding a good epoxy for aluminum. There's not much out there and what is out there isn't cheap. The epoxy granite polymer may work the same as the JB Weld but as I've never used it, I really can't say how good the grip to aluminum is or what kind of shearing strength it has.
     
  9. Karl Miller

    Karl Miller Well-Known
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    @trentaw, I am almost done. I will post it soon. it is a C-beam based design (1500mm for both x & y axis) . I am using a cross between cncrouterparts.com rack & pinion parts and area51 plate design to get more wheels to improve rigidity, but am not using the openrails.
    My design allows for a plasma water table as well so it can be a router or plasma cutter. I am hoping to be able to add a 80Watt CO2 laser to it as well.
    I am currently looking for 20 pitch, 20deg 60 tooth 1/4 bore gears to directly drive against the rack instead of using the 3-to-1 Pulley system cncrouterparts.com designed. I believe I should get the same results but would love to hear from all of you if that is a mistake.
    I haven't read anything about cutting fluid effecting the E/G. I think it would be like getting wd-40 on your kitchen solid surface countertop. I think you would have to research the effect of cutting fluid on epoxy. I think it is too viscous and alkaline to have any effect.
     
  10. Karl Miller

    Karl Miller Well-Known
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    THE E/G is recommended for thicknesses greater than 1/2 inch.

    What would be wrong with just drilling a hole vertically through the two sections, and bolting them together every foot or so?...
    ... I mean if you could do it in such a way as to avoid getting in the way of wheels using the t-slots.
     
  11. Metalguru

    Metalguru Master
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    Hey guys:

    Further to the discussion of filling the cavities in C-Beam and other extrusions with epoxy or concrete, I just ran across this material called HardBlok. It is used in engine blocks by racers to partially fill the water jacket of an engine to increase the strength of the block. It is a dry powder mixed with water and contains iron particles along with some kind of cement like mixture. Apparently, it is extremely hard and dense, and is easily mixed and poured into any cavity.

    Looks like it would be the ideal material for this application. Fully bonds to steel and aluminum, will not shrink or expand, is waterproof, and lasts forever. Kit of 2 6lb bags is under $100 from Summit Racing, and that makes about 3 quarts.
     

    Attached Files:

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  12. Moag

    Moag Master
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    Looks interesting @Metalguru, massively expensive and hard to source in Oz though, but I think your onto something Mate.:thumbsup:

    Did a rough calculation in Fusion 360 of the volume needed for filling the main voids in a 1000mm C-Beam section.

    148.375mm squared + 148.375mm sq + 150.295 mm sq + 148.375mm sq + 148.375mm sq = 743.795mm sq

    converted to volume of 1000mm C-Beam

    743.795mm sq x 1000mm = 743795 mm cubed

    converted to litres = 0.74375 litres

    converted to US quarts = 0.7859 US quarts

    So you should be able to do three 1000mm C-Beam sections with One Short-Fill Unit if I got my calculation right:rolleyes:

    @X-Gantry-Re v2.png
     
  13. EvanBruner

    EvanBruner Veteran
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    Look at Moroso Block Filler, it looks like the same thing and is much cheaper.

    Interesting idea. I ran some simulations and found that even modeling the epoxy as full cast iron only acheived a reduction in deflection by about 40% with the force applied laterally into the beam. I modeled the same test with a 1/4" plate of aluminum bolted to the back of the extrusion and achieved a 60% reduction. That seems like a better route to me but you of course will only be able to use one set of wheels. Something to think about. I would run some extensive simulations before investing any money into this. As many have said before, the main advantage of filling the extrusions will be resonance reduction which is still important but don't expect drastically stronger machines.
     
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  14. Metalguru

    Metalguru Master
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    It's a bit pricey, but have you priced out 3 quarts of Epoxy?

    Of course HardBlok claims their product is way better than Moroso's, what else is new?

    EvanBruner , what are you using to model this? The plate idea is good, and in fact with judicious use of spacers you could still use double wheel sets. You'd just have to space your back plate out an additional 3/8"...

    Moag , Hardblok does list some dealers in Oz on its website, but I did quick searches and did not find the product on any of them...

    MG
     
  15. EvanBruner

    EvanBruner Veteran
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    I'm using Fusion 360 to model the results on a 750mm C Beames model I already had. I made the beam simply supported at the end and put a point load in the center of the beam of 15 lbf. The plain beam had a max deviation of .01", the filled beam .006" and the bolted plate .004".

    Hadn't thought of spacers for the back, even better.
     
  16. Metalguru

    Metalguru Master
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    Hey EvanBruner, the problem, in my mind, is not simply downward deflection of the c-beam due to gravity and the weight of the router etc. , although this is important. But, the c-beam is reasonably stiff in this direction. Where I think the problem lies with c-beam is the twisting or torsional stiffness. It is much less stiff in this direction.

    Can you model torsional stresses? Ie. pulling forward or back on the top of the Z axis, which is equivalent to the bit getting pushed or pulled in the Y plane.
     
  17. EvanBruner

    EvanBruner Veteran
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    I modeled the load as an applied load perpendicular to gravity just as a baseline for the differences in strength. Torsional load may be more telling, you're correct. I will rerun the sim but apply the same force about 100mm from the rotational axis of the beam. That should give you a good idea of what kind of deflection the beam will have taking an aggressive cut in aluminum with the bit 100 mm below the beam. I'll whip up a few models and see what we get in a few minutes.
     
    #17 EvanBruner, Aug 15, 2016
    Last edited: Aug 15, 2016
  18. Metalguru

    Metalguru Master
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    I didn't realize Fusion 360 had finite modelling capabilities.

    Have to take another look...
     
  19. EvanBruner

    EvanBruner Veteran
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    Alright, the simulation took forever since my desktop seems to not like the simulation meshing...gets stuck at 80%. Had to use my laptop but I still got the results. The results are much the same as the point load of the original. Each beam was modeled with a 6600 Nmm moment about the center of the beam. This is roughly equivalent to a 15 lbf load applied 100 mm from the center line of the beam.

    Test 1: Plain Beam

    [​IMG]

    Test 2: Filled Beam (45% reduction in maximum deflection

    [​IMG]

    Test 3: Attached Plate (55% reduction)

    [​IMG]

    Test 4: Filled And Attached Plate (%75)

    [​IMG]

    Some issues with the results. I again modeled the extrusion fill as cast iron so the numbers are pretty optimistic. Also, Fusion models the contacts bewteen the filled sections and the aluminum beam as bonded with no seperation or sliding. In the real world, we would expect a small amount of seperation due to the effects of thermal expansion and, as these beams are farely slick its hard to say whether the epoxy will fully bond with the beam. Perhaps one could etch the insides of the beam with a lye solution prior to filling to promote adhesion.

    The simulation with the bolted plate is modeled with a .25" x 80mm 750mm 6061 bar fully adhered to the aluminum. Again, results are optimistic as bolting the plates will not give perfect bonding between the surface, but its a close approximation.

    These results make the filled beam look more promising if you can find a low cost and high strength filler for the beams. The bolted plate is only 3 lbs of material that can be had for $20, but will require more hardware to allow the use of double wheels.

    To get the best results possible, you could bolt the aluminum plate to the opposite side of the beam and fill the beam with filler. You would have to find a solution for mounting the lead screw, but you would be eliminating the weak point of the C Beam, the channel to house the leadscrew.
     
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  20. EvanBruner

    EvanBruner Veteran
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    Fusion can do static, modal, and thermal studies. Something like Solidworks is much more powerful but Fusion is incredibly easy to use. Their automatic contact setting makes it super easy to simulate having to tediously select contact faces.
     
  21. Metalguru

    Metalguru Master
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    Cool, nice work, EvanBruner. Hey, I had an idea to put tension rods through the c-beam holes, just a threaded rod with nuts on each end to put the c-beam under tension. maybe just 2 or 3 3/8" or even 1/4" threaded rods in the top, middle, and bottom pockets. Is there any way you can model that?

    According to the makers of Hardblok, it bonds well to aluminum or steel, and contains a lot of powdered iron as an ingredient, so it's probably close to cast iron in density. According to them, it has almost the same thermal coefficient as cast iron, which is shy they use it in engine blocks, but they also say it works just as well in aluminum blocks.

    I think the c-beam is clear anodized, not sure if it is also anodized on the inside, but anodizing usually goes all the way through holes and things. This may affect the adhesion. Epoxy should have no issues with adhesion.

    Hey Moag, I just noticed the u-channel inside your rendering of the c-beam. That looks like a good idea, have you actually tried it? BTW, nice rendering, what did you use?

    MG
     
  22. Joe Santarsiero

    Joe Santarsiero OB addict
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    Don't overrate Solidworks modeling. It's the least intuitive and still takes way too long to setup even if you are a trained modeler using it. From experience, edit; nvm. lol. story for another thread. Fusions approach is intuitive which lets users jump past the stupid setup time, program quirks, and some of the additional training for SW modeling. Sure, for the time being SW can do some more complex analysis, but with f360 the designers and engineers can actually verify a lot of considerations they may have without spending anymore time on set up or having to rely on a modeler to verify to others what you've already calculated and simmed for yourself. That's been my experience with F360 modeling anyway. Sure the program has some ways to go, but their updates are about every month now and are based on their huge ears for all users, pros and the diyers a like. The F360 team is on a mission and they've been making it clear that failure is not an option.
    Both, whether or not the expoxy delaminates is hardly a concern. That stuff is so ridged and brittle that after it sets the void geometries will not let it move much as with say a circular void. Unless there is significant shrink, I think this subject is akin to getting lost in the weeds.
    On another note, the beam is screwed into two plates at the ends and the resistance to a vertical load perpendicular to the spoil board that the plates and wheels combined create make this closer to a beam with fixed ends rather than one that is simply supported. btw, that's better for realistic vertical beam deflection calculations.
    All that said and back to torsion, torsion calculations at the center aren't going to be too far off if you place the loading points correctly. The downfall of running wheels like this in any extrusion is the fact that the outer webs will flex no matter what. Unless....you figure a way to fill those too!
    Other than filling the outside webs, fillings the internal voids isn't a bad idea. Personally, I think that the general reader/user here has to understand that web flex is the nature of the beast with any profile extrusion machine. Adding, has anyone done any calcs on the negative effect of accel and decell that this type of mod will have?
    Regardless, much thanks to all of you tweakers for making the OX and C-beam great machines. Within the past decade CNC equipment for the home shop in general has been an out of reach, yet very desirable technology. A reduction in the cost of components, the surge in community, and especially the tinkerers like you continue to increase the commonality of finding these machines locally. In some cases even alongside other more expensive pieces of single job equipment in our retired neighbors garages. In the past few years all of us have seen a significant uptick in diy cnc from various sites and sources. Folks are cruising through hardwoods, cutting aluminum, and building more machines from a machine using ingenuity combined with precision automation.
    Because of you, this site and community is part of that history.
    So thanks for making cnc something that is no longer unobtainium.
    Tweak on guys. Tweak on. ;)

    Joe
     
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  23. EvanBruner

    EvanBruner Veteran
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    I'm not sure how I would model the tension rod idea, I'll look into though.

    My foggy memory of mechanics tells me that it won't provide any rigidity torsionally or from lateral loads though.

    It might be similar in density, but not in strength. Solid metals are strong because of their grain structure. Epoxy granite gets its strength, as I understand it, from the packing of the aggregate in the suspension. I'd be interested to know where this block filler sits in the spectrum. I don't know of any materials that are a close approximation to it to model with but if anyone finds info let me know.
     
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  24. EvanBruner

    EvanBruner Veteran
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    You are correct, I did model it with fixed ends. Not sure why I said simply supported. I agree this isn't the best way to simulate this but I think its a decent approximation to see what kind of effect filling the beams will have. The best way would probably be to model the entire assembly and apply the load on the spindle collet but thats frankly far more involved than I'm willing to go haha.

    On the subject of Fusion... honestly I don't know why us hobbysists bother with any other programs. It does everything we could need for the most part and its free. Extremely powerful tool and great for these quick simulations. Being able to model and do CAM in the same software is a huge boon too. It definitely has its quirks though (chain selection is killing me).

    The effects on acceleration are going to be dependent on the density of whatever you fill it with. Fusion tells me the block filler will quadruple the weight of the beam if its density is similar to that of cast iron. Intuitively we'd say we need 4 times the amount of torque but since the mass of the other components will remain the same, we're probably looking at maybe a 50% increase for the entire moving assembly. I don't think this will be an issue so long as you aren't using small motors. You will be losing some rapid speed though as these motors don't have a lot of high end torque.
     
  25. Moag

    Moag Master
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    Not yet buddy, in the process just at the moment, thanks, and Fusion 360 mate. I was going to use 40 mm x 20 mm x 2 mm (36 mm x 18 inside) which would fit nicely inside with clearance for the nut blocks, the only place I could source some here was from the big smoke with $60 freight, so visited the local aluminium shop and got some 40 mm x 20 x 3mm (mill finish) for $10 cut to length to play with. A little sanding down will be needed to fit inside the C-Beam (39.8 mm) and the sides of the nut blocks will need about a mm trimmed off each side to have some clearance. If I can get a good press fit it might help stop the slight difference in pretension of the wheels front to back with a double wheel setup and hopefully help the torsional twist of the C-Beam in longer lengths. Ordered some Moroso Block Filler to play with, as it was way easier to get hold of here, which might be better than the dirt cheap casting plaster I was going to give a go, which expands about 0.03 on drying. I ruled out Epoxy firstly because of its shrinkage on curing and secondly cost.

    Thanks @EvanBruner for the simulations matey, great job, I think my computer would just burst into flames if I tried.;)
     
  26. Moag

    Moag Master
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    Test fit @Metalguru, more like press fit on a 500mm actuator but I think it might work, just needs the other nut block filed to fit and filed down to match the length of C-Beam and maybe some Low Profile Screws and Tee Nuts to hold it in place.;)

    _X8A4062.jpg
     
  27. trentaw

    trentaw New
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    What the heck!? I somehow got unsubbed from the thread that I created :confused:. Now I have some serious research / testing to go do to get on the same level to which this conversation has elevated.
     
  28. Moag

    Moag Master
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    So sorry @trentaw, but it's such an interesting, thread heading:thumbsup:? That will be easy to find with a quick search by others later on. It has got me going that's for sure ...so thanks muchly for starting a great conversation.

    So finished fitting, U channel to two 500mm C-Beams, which needed a fair bit of precise sanding so not an easy solution but works well at strengthening the C-Beam weak spots, and near to finished fitting the 1000mm C-Beam which is a harder precision sanding job. Got some Moroso Block Filler delivered in the afternoon and mixed up a little and filled a trimmed off a section of 40x40 V-Slot which is setting way stronger than I expected. It's kind of like grout. It appears to have a chemical reaction with the Aluminium when wet, with bubbles being produced, like a charging lead-acid battery where it is in contact with the Aluminium, and spills etch the anodising if not wiped off.
     
  29. Joe Santarsiero

    Joe Santarsiero OB addict
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    Did it bond or set-up loose?
     
  30. Moag

    Moag Master
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    On the short section, 40mm cut off section of 40x40 V-slot of the test, it bonded but there are pathways / small voids at the interface with the aluminium where it was releasing gases from some kind of chemical reaction. There appear to be finer softer particles in this area as well, I might go out and try and smash it out with a hammer and small cold chisel to see what went on inside, and try an experiment with plaster for interest sake. In the whole, it has got rid of any ringing, not suitable for wind chimes, added a lot of weight and feels rock solid, so might be suitable for non-moving sections of V-Slot.
     

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