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Ultimo

Discussion in 'Other Builds' started by Brian Slee, Apr 27, 2014.

  1. Brian Slee

    Brian Slee Well-Known
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    Hi Justin,
    It was great meeting you at the fair today. Unfortunately as you saw the room we are in kind of precludes me from doing that kind of work on site. I will definitely look at the acrylic additive though when we do the next frame after the fair is over.
     
  2. Brian Slee

    Brian Slee Well-Known
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    Hi Rob,
    No real chance for fixing it until after the fair, We are inside the center in a meeting room and I am pretty sure they would have a conniption fit if I started dragging in bags of concrete and buckets and started mixing up batches. We are actually so busy talking to people I haven't had a chance to do anything to the robot. The good news is that even with a couple shattered legs the mechanical components for the effector are still all lined up so I can demo some of the functionality by hand.

    I did know that shrinkage was a factor when dealing with concrete but since the v-slot is only attached by friction fit I was thinking the T-nuts would tend to slip inside the slot as it occurred. Note...I did not get a perfectly flat mounting surface so as I improve my processes I might have to include a scheduled maintenance requirement for a monthly loosening and retightening of the T-nuts during the first two years of ops until the concrete is finally cured.

    Vibration transmission has been in my thoughts also, one of my first thoughts after I got the frame all together was "My God it looks like a giant tuning fork" lol. I might add some rubber pads at strategic locations to dampen the vibrations as much as possible to be safe.

    Right now the posts are 60mm square to match the face of the v-slot. I was going to expand the back of the section opposite the v-slot to 75mm to from a wedge profile with a flat face. Is the 2x to 3x number based on a FEA for strength and deflection of reinforced concrete anchored at two ends? I am willing to eat the weight to get the functionality but it would be nice if we can keep it light enough to keep it on castors. Another option discussed was using a steel form and filling it with concrete for stiffening (I am not a big fan of this idea for the shrinkage factor). Or also just making the form part of the final assembly to create more of a composite structure. I will be mixing some small batches next week and experimenting with additives and maybe even doing an experiment with sandwich structures by adding several layers of cloth reinforcing fabric. I think I have some fiberglass and will have to look into what CF is going for these days. I am always open to suggestions and all of your input has been great.

    P.S. OHHHHHHH that's what you mean when you were talking about depth of cut at the edges. Now I see said the blind man
     
    #152 Brian Slee, Sep 13, 2014
    Last edited: Sep 14, 2014
  3. Brian Slee

    Brian Slee Well-Known
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    Hi All,
    Wow what a great show! The turnout is amazing and it's been great meeting and talking with so many enthusiasts and makers. All of the OpenBuilds products are a big hit with the makers and the stuff Mark sent down for the show is getting quite a workout from the folks as they wander through :thumbsup:. I did not get any pictures today because I walked out of the house without my phone :banghead::banghead::banghead:. I will try and remember it tomorrow so I can post up a bunch of pictures for everyone. So...

    Stay Tuned...
     
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  4. Mark Carew

    Mark Carew OpenBuilds Team
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    Great to hear you guys are having fun Brian! I know you have been working so hard setting this up and it nice to hear you both have a chance to sit back and chat with like minded folks at the faire.
    Looking forward to seeing the pics keep up the great work. :thumbsup: and thank you again for letting OpenBuilds be a part of the show.
    Mark
     
  5. Justin Edwards

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    I had a lot of fun, it was really interesting to a lot of other peoples projects. My wife said she'd help me setup a booth if I wanted to do one next year. I got all of my replacement part prints done this weekend on my big delta, I'm hoping that stiffens it up enough, if not I'll probably miter cut my extrusions and drill, countersink, and tap everything and add plates for extra stiffness.
     
  6. Rob Taylor

    Rob Taylor Journeyman
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    Ah, ok. I was thinking it would be a little looser like the Maker Fair Primes over on the West Coast. Still, you got to show off your progress and direction as well as OpenBuilds, so it was still reasonably successful. Next year should go much more smoothly!

    That would make sense to me. Apparently after the first month or so the shrinkage becomes on the micron level anyway. That said, epoxy concrete only takes a week to fully cure, with no shrink...

    Vibration is apparently the original intent of epoxy-based composite structures- epoxy-granite/quartz is an excellent vibration dampener and steel machine structures can be filled with it to increase accuracy and tool life. You don't need to worry about its structural integrity when you're just filling a steel tube with it, either. No vibration or vacuum is really necessary. Might be a good direction for you for a production line, since all you really need for the steel is a drill press for mounting bolts/brackets- welding isn't strictly necessary (I don't have a drill press, hence my fascination with epoxy). It would be quick and easy.

    Not sure I'd go with rubber, since it would probably swing the stiffness:damping ratio too far in favour of damping.

    No, it's not based on math, more on how many concrete-based machines I've been looking at lately and their general gantry support height/width ratio. They're typically very fat, and I'm not sure you have enough mass on those uprights to support the kind of forces you're looking to generate. Some kind of calculations would be handy, though, you're right. It probably ultimately depends on the mass of your milling head assembly and arms, and your projected feed rates. Some kind of computer engineering model would be handy there.

    Castors are available with very high load allowances- up to thousands of pounds each. I saw some on Grainger that could do 750lb for $50 apiece- with brakes. I'm just not sure about the accuracy of a machine tool on castors. Maybe if you could lower the machine onto a fixed base, then raise it up to move it? Seems like vibration would concentrate at the castor hubs.

    I think that's the best idea. I'm up to page 80 of the infamous Epoxy Granite thread on CNCZone, and if you're looking at short lead times on production units, that's the way to go. Just make sure that your steel structure is fully capable of 100% of the load bearing.

    Experimentation is good! I'm hoping to get some pool filter sand, quartz pea gravel and maybe some ceramic microspheres, hit up US Composites for 600cpm epoxy and make me some bricks to smash soon. :D I'm planning on making more simple structures before attempting a big (well, a couple feet cubed) fixed-gantry mill, like a bench sander, flywheels, maybe a simple wood lathe bed... A tape dispenser, even!

    I'm not entirely sure about reinforcement yet. I may go with some chopped 1/32" glass fibres, to see if they affect impact resistance or bending/breaking forces, but it seems likely that I'll end up having to compromise on the vibration front somewhere and add some threaded rod reinforcement for tensile strength.

    Hehe, yeah. I doubt it'll matter unless you're planning on some serious stock removal though.
     
  7. Brian Slee

    Brian Slee Well-Known
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  8. Brian Slee

    Brian Slee Well-Known
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    Hi All,
    I would like to say that I have been hard at work on the new frame but I cannot tell a lie...I slept for a whole week :sleepy:. After resting up I have reorganized and I am just about reset for pour #2. I took a hammer to the first frame and did a post mortem analysis on the overall skeleton. From what I can see it was good pour overall. I did not see any major voids or gaps in the structure during the disassembly. After working with the first one I believe that my post sections are still too thin for using rebar. I did a little research on acrylic additives and unfortunately they are not compatible with air entrained concrete mixes :( , which is my first choice ATM for it's lower density and higher strength. So for pour #2 I will change out the rebar for 1/2" hardware cloth type welded wire and see how it affects stiffness and rigidity.

    Stay Tuned....
     

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  9. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    While moving the steel reinforcing closer to the face of the concrete will be beneficial in the long run, it will do nothing to increase the strength or rigidity of the concrete. The steel doesn't engage until the concrete has cracked and once the concrete has cracked, too much stiffness is already lost. The only way steel is of any value to strength and stiffness is in pre or post-tensioned applications which are not really possible in your situation. I would suggest using 1/4" all-thread rod set 1/2" clear inside each of the 4 corners of the formwork as this will give you a better incremental grip on the concrete than can be provided by the wire mesh. Finally, like the others, I would suggest the polymer modifiers and if that means ditching air entrainment, so be it. The minimal strength loss can easily be overcome with higher strength concrete mixes. Fibermesh is also a good thing.
     
  10. Rob Taylor

    Rob Taylor Journeyman
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    Rick's on the right path.

    I'm now almost finished the CNCZone EG thread, on page 382, and I can now pretty categorically state that 1) Concrete is next to useless for the type and style of machines we make because it has no tensile strength and low damping, and 2) there's absolutely no way you could even use mineral casting (epoxy quartz) in the dimensions you have, even with internal reinforcement, due to both tensile strength of epoxy and shear modulus (-> stiffness) of steel issues over that length of beam.

    Polymer additions to concrete don't appear to be very helpful either- vinyl ester, acrylic and polyester, the typical resins used for polymer concrete, are all too soft, too cure shrinking, too much coefficient of thermal expansion, and/or too chemically non-resistant to be useful for machine tool construction. Epoxy is the only viable resin for hardness (particularly "tabletop epoxy", which also self-levels to very high accuracy), tensile strength, low shrink (as long as it's VOC-free, ie. non-accelerated), thermal stability and chemical resistance (mainly coolants and lubricants, in our case).

    For the base, it'll have to be epoxy-based mineral casting if you're going to get out remotely cheap and avoid expensive months-long metal casting processes or weldments. It should probably be about 6-8" deep, where the concrete round in the photo looks more like 3" deep. Tossing some threaded rod into the form probably wouldn't hurt, and you could use it to attach other parts.

    For the uprights, there are basically three options: 1) thick wall square steel tube, probably about 2.5-3", filled with epoxy quartz for damping. 2) ~6" square epoxy quartz columns with threaded rod and/or carbon fibre tube for stiffness (in the tensile region and neutral zone resepctively, I think). 3) 10"+ epoxy-quartz-only columns, with probably a slight reduction in overall height in order to reduce the torque moment about the anchors. Your EQ columns will have to be significantly thicker at the bottom than the top, too.

    Those are obviously math-free approximations, you'd need to crunch some aggregate numbers and do some kind of finite element analysis on the results to get absolute answers, but yeah, this is an engineering challenge, for sure. Definitely not just a case of pouring some concrete and having at it.

    Put it this way: if you have a big heavy spindle trying to push through metal, the downward force of a column is imparting a force proportional to the compressive force on the head lever (itself proportional to feed rate and workpiece hardness, I guess) and the angle of the lever to the upright. That's not counting sudden forces from the spindle encountering resistance or digging in. The magnification of the stepper and spindle forces through that lever are placing quite significant cross-loads on your uprights.

    I think it's time to make a decision on whether a delta bot is really worth the headache, or scale back your "industrial machine" aspirations. Cartesian machines are more popular for high power applications for a reason, I'm now realising!
     
    #160 Rob Taylor, Sep 24, 2014
    Last edited: Sep 24, 2014
  11. Brian Slee

    Brian Slee Well-Known
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    Hi All,
    Got started on the new frame and thought I would post up a few pictures. I still had a fair amount of the air entrained concrete mix on hand so I decided to stick with it for now. I think with the new reinforcing scheme that it will handle anything the belted system is capable of dishing out.

    @Rick 2.0 I like the threaded rod idea :thumbsup:. I will look at doing a test pour with the heavier mix and acrylic admix in the near future, to see if the extra weight and expense can be justified. when compared to the current architecture.

    @Rob Taylor Lol...I haven't gotten quite that far. I did get through the index and came across the paper from Bamberg on Principles of Rapid Machine Design which has a wealth of tech data to draw from. I noted in his paper that reinforced concrete has damping properties on par with EG and cast iron. Given the price differences I think that the concrete path is still the best approach with possible additional augmentation if needed. We will have to see what kind of results we can get as we progress. At this point all options are still on the table. And no I am not deterred from using the delta configuration I still like the small footprint and potential adaptability ;)
     

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  12. Rob Taylor

    Rob Taylor Journeyman
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    I finished the thread last week, still have the same view, though marginally relaxed on the production tolerance front after the last few pages. I haven't yet started digging into the associated literature, but Principles of Rapid Machine Design and Concrete Mixture Proportioning (Bamberg and de Larrard) are definitely on my to-read list!

    Reinforcement with regular concrete may end up having to be so substantial that you essentially end up with a steel machine. Not that the idea of a non-welded machine from slotted steel with added external damping hadn't occurred to me- rapid bolt-together power CNC would be quite an achievement! I think we're still aligned on the overall concept of simplicity, power and non-expertise (in terms of end users building and maintaining). I think my concern is that trial and error may prove to be a longer, more expensive process than you may be anticipating. Hopefully not, though.

    Interesting, I'll have to look further into the damping of reinforced concrete... Given how readily concrete "tinks" rather than "thuds" on impact, I suspected that the damping was quite low, but didn't have a source to pull from when I made the comment. I imagine that it is reasonably on par with cast iron, but hit the nearest anvil and you'll see how damping that is! Haha. The numbers thrown around as well as the subjective testing in that thread indicate to me that EG is a significant improvement over either of them in damping- as well as all those other properties I mentioned. I should have the opportunity to test that soon empirically, though.

    I'm not sure how much you're paying for concrete, I hear EG comes out to around 60-80c a pound. Concrete's probably cheaper. My issue is trying to get aggregate without having to pay shipping on 50lb bags and drums cross-country. That said, hardness, fracture toughness, etc all being reasonably equal, aggregate sizing seems to be much more important than actual material. I may look into getting some cheap sieves and see if I can't come up with a "Home Depot Mix". Whether that will be sufficient for my final purposes, I don't know. I was, er, "financially motivated" to switch recently towards an initial lower power (maybe 400W?) 150x150x70mm benchtop manual mill/precision drill design using V-Slot and then proceed to the 450x450x200mm CNC desktop gantry-style later. That should provide me with a testbed for a cheaper mix in the shorter term.

    Really, the thing that excites me the most about epoxy is its self-levelling. It's possible to both create a gorgeous, glassy machine as well as almost measurement-free surface production to 0.03%. The only bit that matters is ensuring mating surfaces will be exact right angles, though even that could be designed around so that the actual parts don't have to mate perfectly, but can be later squared and trammed to tolerance after construction. That would be preferable, I think.

    If we stuck to just milling wood, we wouldn't have these problems. :p
     
  13. Brian Slee

    Brian Slee Well-Known
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    Hi All,
    Did you miss me? After taking a break I spent some time working to improve my processes in making the frame components and here is what I have come up with. For this pour I have ditched the rebar and built my reinforcing structure from hardware cloth with extra reinforcements of threaded rod in the area that failed during the transport for MFO. I also devised a method to put the structure under significant tension during the pour and cure cycle to increase the stiffness even more. I should be getting to the pour in the next day or so.

    Stay Tuned...
     

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    #163 Brian Slee, Oct 17, 2014
    Last edited: Oct 17, 2014
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  14. Brian Slee

    Brian Slee Well-Known
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    Ok...The saga continues. First pour for the second frame is done and curing.
     

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  15. Brian Slee

    Brian Slee Well-Known
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    Hi All,
    Ok the new posts are out of the molds. These are much stiffer than the last set. I will be setting up for the second pour and posting more pics this week so

    Stay Tuned...
     

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  16. andrew

    andrew New
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    Of course we will!!
    This thing will be awesome, and the journey is nearly as good as the destination.
    Good luck, thanks, and best wishes.
     
  17. M. Shiraz Kaleel

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    Why cannot steel be used, with temperature compensation for expansion incorporated into the computations for the movements needed from each stepper motor?
     
  18. Rob Taylor

    Rob Taylor Journeyman
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    The TCoE I refer to there is specifically the differential between the steel and the concrete- the structure delaminates itself. That may or may not be significant, depending on the specific circumstances. Under stable conditions this obviously isn't a concern though. I believe aluminium has a much more similar TCoE to mineral casting, but it's also far better at transmitting vibrations.
     
  19. Brian Slee

    Brian Slee Well-Known
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    Hi all,
    Some results from take 2...

    Hardware cloth - Sounds good, looks great, Fails even better. The cloth is just not strong enough locally to handle any significant loading on the long beams. I am still good on my concrete supply so take-3 won't be long in the making and I am getting dialed in.

    I used my mouse sander to vibrate the forms this time while I was doing the pour and saw a big reduction in bubbles and voids and IMO a big improvement in overall quality of the posts.

    I was also happy with the results from adding the extra reinforcement and concrete at the bottom.

    @Rob Taylor For cost comparison I am not sure price per pound is the best measure. Probably a better one would be cost per cubic foot of material. If you have some solid number for E/G based on volume we could compare this last go round with E/G. For the three posts I just did it took one full bag of concrete mix which is one cubic foot @ $7.50, add in approx. $5.00 a leg for the reinforcing material and a few dollars more for misc hardware would give a safe estimate of around $30.00 per cu ft.

    @andrew Thanks for stopping and saying hi and for the positive wishes. I promise it will be worth the wait :)

    More to come so

    Stay Tuned....
     

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  20. Justin Edwards

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    How's it all going? My big delta has been a workhorse for a while. I've worked on making some custom (printed) parts for it and everything has worked out well.
     
  21. Brian Slee

    Brian Slee Well-Known
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    Hi Justin,
    I am sad to say that I have not made much progress recently. My sister passed away just before Christmas and I was helping to care for her in her final days. I hope to get back to building as soon as priorities allow maybe some time by the end of the month.
     
  22. Brian Slee

    Brian Slee Well-Known
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    Hi Everyone,
    I am ready to get back to work, but before I get back to building, I would like to take the opportunity to thank everyone who has helped the family through a difficult period, and to ask that you allow a moment of prayer on Trish's behalf. May her soul land in the arms of love.
     
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  23. Brian Slee

    Brian Slee Well-Known
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    Hi All,
    I am working on getting the drawings finished for the new frame. We have laid in 90' of 1/4" threaded rod for the reinforcement for this pour, and while I was disassembling the last posts I noticed that the hardware cloth was very beneficial in respect to impact resistance, so I am also planning to keep the hardware cloth in the mix. Here are some pics to give you a preview.
     

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    #173 Brian Slee, Feb 10, 2015
    Last edited: Feb 10, 2015
  24. winand

    winand Well-Known
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    Interesting, and why is that?
    If it's the computing power then a Arduino Due with a ramps-FD would be equally capable i guess,
    or is it a software/firmware issue which causes better accel and jerk handling?
    Which firmware are you running on the beaglebone?
     
  25. Brian Slee

    Brian Slee Well-Known
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    BOO!!!
    Hi Again all. Well are you ready for Season 2 ...Ultimo Reborn...The Saga Continues!!

    Guess I am just too dumb to quit when I am behind,...and battered...and bruised lol

    I haven't gotten a lot done in the shop since my last post but I have been working on the drawings and a few minor changes from the last iteration. I went with Ricks suggestion of using four pieces of threaded rod for the concrete reinforcement and am going to use granite as my working surface based on Rob Taylor's input. I am going about it a little different though in that I am using a natural piece of granite set in the concrete base. (Donated by the nice people at ADP surfaces in Orlando, they are super nice folks and if you live around O-town and ever want some stone countertops or other stuff done give them a shout). I have managed to put together a couple of jigs and we got the granite cut Sunday. Take a look and feel free to throw rocks if you are inclined. :O)

    I am planning on getting to work on the new forms this week and "God Willing" I will be back to giving you some regular updates on the project.

    As Always.......Stay Tuned!!
     

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  26. Tweakie

    Tweakie OpenBuilds Team
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    Hi Brian,

    Good to see you back making progress again - I am really looking forward to reading series II.
    Although some of the things / processes you have tried so-far have not been 100% successful I have learned a great deal from your research. Keep up the good work my friend.

    My regards to Boo and Lord Zulu.

    Tweakie.
     
  27. Brian Slee

    Brian Slee Well-Known
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    Thanks Tweakie,
    It's good to be back :). I think it's just a matter of time til we hit the sweet spot on the right mix for the composite structure. How is your little helper doing? Better yet how's your WC football lol.
     
  28. Brian Slee

    Brian Slee Well-Known
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    Hi Winand,
    I noticed you didn't get a reply so I thought I might chime in. From what I understand people running the Delta frames can load down the processor on the Arduino when they set the microstep setting above a certain point. I think it gets to bogging down at 8x or higher due to the trig calcs involved for determining carriage positions from step to step. I will be running at 1x i.e. no micro stepping so I believe the Arduino will have no issues in this case. With the gear set I am using and running the steppers straight up, I have I should have a step distance of app .054mm without it. But the proof is always in the pudding as they say.
     
  29. Justin Edwards

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    Brian, where did you get your metal tie rod ends? I've had good luck with my big delta over the last year, but my tie rod ends are starting to wear down now and I've compensated by preloading with springs, which works fine until they wear down so much that it restricts movement.
     
  30. Brian Slee

    Brian Slee Well-Known
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    Hi Justin,
    Here is where I ordered mine from.
    http://www.midwestcontrol.com/part_family.php?id=1

    I started with Heim Joints and switched over to ball joints at the time because I couldn't get the high misalignment spacers in time for the show last year. The ball joints limit my deflection angles to 23.5 degrees which gives me a working diameter of just over 500mm with a few degrees to spare to help prevent any binding issues (hopefully).

    I would enjoy seeing some of your prints. Do you have any pictures posted?
     

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