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  1. #11
    Quote Originally Posted by mekanik View Post
    Hi John
    Regarding vertical mounting you will have to build yourself a substantial base, if you make another post asking for ideas for designing a vertical assembly machine Dean(JAZZCNC) might give you some advice regarding this, he has a video of one of his larger builds but i couldn't find it.
    Regards
    Mike
    Okay, thanks a lot, I'll have a think about some options.

  2. #12
    Kitwn's Avatar
    Lives in Don, Tasmania, Australia. Last Activity: 2 Weeks Ago Has been a member for 4-5 years. Has a total post count of 977. Received thanks 115 times, giving thanks to others 52 times. Referred 1 members to the community.
    John,
    I haven't tried this but have wondered if polystyrene concrete could be used to damp the gantry without it getting too heavy. I found an article once (don't have it to hand I'm sorry) that described using up to 60% by volume of polystyrene beads (you can buy them for making bean-bag furniture) to make concrete for light-weight structures. It's still quite strong at that percentage and I think the density came out at a little over 1Kg/litre.
    An optimist says the glass is half full, a pessimist says the glass is half empty, an engineer says you're using the wrong sized glass.

  3. #13
    Quote Originally Posted by Kitwn View Post
    John,
    I haven't tried this but have wondered if polystyrene concrete could be used to damp the gantry without it getting too heavy. I found an article once (don't have it to hand I'm sorry) that described using up to 60% by volume of polystyrene beads (you can buy them for making bean-bag furniture) to make concrete for light-weight structures. It's still quite strong at that percentage and I think the density came out at a little over 1Kg/litre.
    Hey. Thanks! That's quite interesting. I was thinking of something similar with perlite and concrete or epoxy. I was told that concrete may react with aluminium though somewhere but I can't recall where exactly. Does a anyone have any insight on that? On this note I was looking at some local companies that sell recycled tyres, chipped up for playgrounds. I was thinking that could make a good aggregate for a damping composite maybe, with either epoxy or liquid platinum cure silicone to bind the chunks together in a similar way to making epoxy/granite.

    It sound like some tests might be in order, luckily I'm an acoustics specialist with oscilloscope etc here so could at least test a few solutions on a small scale.

  4. #14
    Quote Originally Posted by mekanik View Post
    Hi John
    Regarding vertical mounting you will have to build yourself a substantial base, if you make another post asking for ideas for designing a vertical assembly machine Dean(JAZZCNC) might give you some advice regarding this, he has a video of one of his larger builds but i couldn't find it.
    Regards
    Mike
    That would probably be this 8x4 then. 10 x 5 with a Vacuum bed will be coming soon if I ever get out of this bloody house again.!!.

    The vertical machine works amazingly for large machines with no downsides other than cannot use it as a bench. The advantages are many and I wouldn't go back to a horizontal machine if larger than 4x4. That said I'd still have a vertical machine under 4x4 for some of the hidden benefits like longer tool life and better chip management but below 4x4 the space-saving isn't so great.

    Regards the filling of tubes then I've tried sand and while it does help a little it's not a massive difference. Don't fill tubes with concrete because it can shrink, it also doesn't mix well with aluminum. Expanding Foam and Silicone etc don't do diddly squat so don't waste your time money.

    The best thing I found is to use a thicker wall tube in the first place and brace it well. Regards the aluminum profile then if you use HD version then you shouldn't have any issues with vibrations and I don't think to fill the voids with Epoxy granite will dampen to any great degree but it will certainly affect performance because of the extra weight.


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  6. #15
    Kitwn's Avatar
    Lives in Don, Tasmania, Australia. Last Activity: 2 Weeks Ago Has been a member for 4-5 years. Has a total post count of 977. Received thanks 115 times, giving thanks to others 52 times. Referred 1 members to the community.
    Quote Originally Posted by Evengravy View Post
    It sound like some tests might be in order, luckily I'm an acoustics specialist with oscilloscope etc here so could at least test a few solutions on a small scale.
    You're the man then! I like the idea of bendy concrete made with old tyres
    An optimist says the glass is half full, a pessimist says the glass is half empty, an engineer says you're using the wrong sized glass.

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  8. #16
    Quote Originally Posted by JAZZCNC View Post
    That would probably be this 8x4 then. 10 x 5 with a Vacuum bed will be coming soon if I ever get out of this bloody house again.!!.

    The vertical machine works amazingly for large machines with no downsides other than cannot use it as a bench. The advantages are many and I wouldn't go back to a horizontal machine if larger than 4x4. That said I'd still have a vertical machine under 4x4 for some of the hidden benefits like longer tool life and better chip management but below 4x4 the space-saving isn't so great.

    Regards the filling of tubes then I've tried sand and while it does help a little it's not a massive difference. Don't fill tubes with concrete because it can shrink, it also doesn't mix well with aluminum. Expanding Foam and Silicone etc don't do diddly squat so don't waste your time money.

    The best thing I found is to use a thicker wall tube in the first place and brace it well. Regards the aluminum profile then if you use HD version then you shouldn't have any issues with vibrations and I don't think to fill the voids with Epoxy granite will dampen to any great degree but it will certainly affect performance because of the extra weight.

    That's awesome! This has given me some ideas for sure... Design wise it's not a million miles away from mine, I really wish I could weld. Maybe I can think of something I could make work using aluminium profile.

    Ten four on the cement filling. I think I'll go with sand on the Y rails that don't need to move just for the added benefit, and try some test pieces for composites on the X gantry, to see if it's worth the hassle. I can't recall if it was HD rails, it was this type of profile from Dold Mechatronic: https://www.dold-mechatronik.de/Alum...-type-groove-8 maybe there is heavier type out there and that was my mistake.
    Last edited by Evengravy; 06-04-2020 at 03:03 PM.

  9. #17
    Quote Originally Posted by Kitwn View Post
    You're the man then! I like the idea of bendy concrete made with old tyres
    Thanks. Sure, I'll do some more in depth reading and maybe some tests soon, the complication at the moment is getting out of the F'ing house to get materials but gives me chance to do some research if nothing else.

    I came across a guy on another CNC forum that recommended bitchumen (tar) plus sand, that could potentially be a cheap and available solution, if it isn't too heavy that is. Maybe roofing tar plus rubber chips. Certainly it's common to use roofing bitchumen sheets (old school roofing felt) in acoustic dampening solutions in a studio environment, I see no reason why it wouldn't transfer here, in theory.

    Silicone would likely be expensive but should be quite efficient, maybe recycled rubber plus a binder might help. It's always going to be a tradeoff of weight vs dampening factor for a gantry though.

    It's simple enough to test smaller pieces in practice though; with a contact mic/measurement mic and some shorter pieces of profile and an oscilloscope, I have some 80x80mm profile I could donate to the cause so I could side by side a few possible solutions as an experiment. Could be useful to see what approaches might work down the line.

    At the moment, I'm just awaiting the new ballscrews to arrive so I can get rid of these cheaper ones.

    Thanks for chipping in guys, appreciated.

  10. #18
    Quote Originally Posted by Evengravy View Post
    That's awesome! This has given me some ideas for sure... Design wise it's not a million miles away from mine, I really wish I could weld. Maybe I can think of something I could make work using aluminium profile.
    Welding isn't that hard, esp if you can get your hands on a Mig welder. You can even hire them from some a decent hire shops.
    The welds don't need to be industrial strength. Steel is very forgiving so it allows you a few attempts if get it wrong and along with a grinder you can hide all your screw ups away.

    Quote Originally Posted by Evengravy View Post
    I can't recall if it was HD rails, it was this type of profile from Dold Mechatronic: https://www.dold-mechatronik.de/Alum...-type-groove-8 maybe there is heavier type out there and that was my mistake.
    That is the ITEM "L" section the "L" stands for light. It's exactly what you see on that vertical machine but I'm using the heavier version which doesn't end with "L".
    However, I've used the "L" on many machines and it works perfectly fine so I wouldn't be too worried.

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  12. #19
    If you are going to do vibration tests then I wouldn't waste time testing individual pieces of profile or steel etc off the machine because all that matters is the tool. Testing at the tool is the only thing that matters IMO. You'd be better investing time on designing a strong Z axis.

  13. #20
    Quote Originally Posted by JAZZCNC View Post
    If you are going to do vibration tests then I wouldn't waste time testing individual pieces of profile or steel etc off the machine because all that matters is the tool. Testing at the tool is the only thing that matters IMO. You'd be better investing time on designing a strong Z axis.
    Yea, that's a good point. I did a bit more reading around the subject and a guy on CNC zone recommended pea gravel in the non moving parts and nothing in the gantry, for now. I'll try that first and see where it is. I actually have a MIG that I bought years ago but never got around to learning to use the thing, a gas-less 150 from draper (I'm not sure if they're much good). It's been shelved in my dads place for years but maybe it's time to dust it off.

    I think the Z axis I have is pretty solid though, it's foundation is milled from stainless. I know the opposite arrangement than most recommend, with the rails on the z plate which seems to be preferred, but it was a simple solution for me. I've tried to keep everything as close to moving bearings and having as little overhang as possible. The Z only has 100mm of travel but after using my other machine for a few years I realised I've never needed to mill anything over a couple of inches thick so the z overhang was really compromising the strength. That plus the momus design is not very good generally. Live and learn. I thought it would be a good idea this time for me to keep the gantry and Z axis as tight to the part as is feasible.

    It's a shame about the profile, maybe I'll change it for something heavier but at this stage I might just run with it and see how it does, should be easy enough to swap it out for a heavier profile down the line.

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