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  1. #111
    D.C.'s Avatar
    Lives in Birmingham, United Kingdom. Last Activity: 05-01-2016 Has been a member for 4-5 years. Has a total post count of 326. Received thanks 30 times, giving thanks to others 24 times.
    Quote Originally Posted by wilfy View Post
    i cant see how 3mm flat bar can replace a 50x25mm piece of box section, the bed bending is the one thing i'd imagine u dont want.
    Fair enough, if you do end up with a load of flat bar left over it is quite easy to weld two pieces together into a single piece of angle.

  2. #112
    Quote Originally Posted by D.C. View Post
    Fair enough, if you do end up with a load of flat bar left over it is quite easy to weld two pieces together into a single piece of angle.
    never thought about that, but if you look back at the previous page, dean has kindly gone over my design and reduced it down and says that it should leave me with 3 meters now out of a full length and all i have to use is 50mm x 5mm instead. which outs the cost at 90 on the dot so i'm more than happy.. and it looks a damn sight better than mine lol

  3. #113
    right, i've finally too jazz's drawing and re-drew it back in to sketchup. i couldnt get on with rhino, its possibly something i'll go back to as i'm aware sketchup isn't that great for actual cnc work.

    any way here it is

    Click image for larger version. 

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    all colour coded as previous designs, the white flat bits are 50 x 5mm flat bar.

    travel is around 450mm x axis, 578mm y axis and 100mm z axis.

    i havn't worked out how much steel is used here, but i know already it's going to come in well under the 2 lengths now.. but as a trade off i've gained 50x5mm flat bar so that total cost of the steel as i said before will be 90. i'm happy with that and i still feel it's going to come in under my 1k budget.

    i think it's time to start clearing the garage up a bit and think about ordering the steel :D

  4. #114
    just added everything up total length of steel is 11.7mtrs before cuts which will probs be closer to 12mtrs leaving me a good 3mtrs spare..

    now i've just done this rough but with 3 mtrs if i extend the legs down by 500mm shown in white here, i have enough flat bar to put support where the longer bits are pictured and that will be pretty much it, but i have a feeling that wont be enough :s

    in this picture i have dropped the legs down 500mm, as shown by the white bits, i've also moved the rail supports down and put a piece of 50x25 in the middle of the rail support. the turquoise blue bits can be removed i've just left them in so i can revert back.

    my question is will this extension of the legs work or will it be a bit wobbly? this is the maximum use of the extra steel left over but it would make it better for me to have it floor standing as i know the bench is no longer big enough to support it.

    Click image for larger version. 

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  5. #115
    Wilfy sounds like you need to take a trip to the scrap yard? Go have a poke around and you never know what you may come up with. look for old metal cabinets or similar. this would work for your base, stick a wanted on Freecycle? save your money for the best bits
    If the nagging gets really bad......Get a bigger shed:naughty:

  6. #116
    Take this with a pinch of salt as my experience is with wood not metal but I'd say that your (white) bracing at either end is too long for that thickness of steel your using. I would shorten the bracing to roughly half way between old and new and then put stretchers between the legs (like a dining chair has). Grab a length of your 50x5 bar at the length you've drawn the brace and see if you can flex it by hand, if you can I don't think it'll be strong enough to act as a brace at that length.

  7. #117
    it doesnt have to be done this way, it was just an idea i had to use the rest of the steel what you see in the picture is all the steel end of.. if it doesnt work, i'll just figure out a way to make it work as a desktop machine it might mean that 2 legs are secured to my worktops and with the left overs i will have enough to extend the other 2 legs down to the ground and do it that way and brace as you said like a chair.

    is it likely i'll need any adjustment in the feet of the machine??

  8. #118
    I agree with the earlier post - those strips are too thin to be useful for bracing. Your problem is they need to be strong in tension (which they are) and compression. A strip is the worst cross section under compression as it'll just bend. Angle would be better, or better still more box section. Also using thin strip for bracing is asking for trouble with resonance as the strip can vibrate, just like a rubber band. If the resonant frequency of the strips is a long way from the frequencies induced due to the motors and cutter then you wont have a problem, however calculating that is not trivial. Shorter strips will have a higher resonant frequency, so are less likely to cause problems, but clearly to an extent offer less support so it is is a compromise.. There's some good information on this site, Mechanical Resonance - Factors that Affect Natural Frequency.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  9. #119
    Quote Originally Posted by Jonathan View Post
    I agree with the earlier post - those strips are too thin to be useful for bracing. Your problem is they need to be strong in tension (which they are) and compression. A strip is the worst cross section under compression as it'll just bend. Angle would be better, or better still more box section. Also using thin strip for bracing is asking for trouble with resonance as the strip can vibrate, just like a rubber band. If the resonant frequency of the strips is a long way from the frequencies induced due to the motors and cutter then you wont have a problem, however calculating that is not trivial. Shorter strips will have a higher resonant frequency, so are less likely to cause problems, but clearly to an extent offer less support so it is is a compromise.. There's some good information on this site, Mechanical Resonance - Factors that Affect Natural Frequency.

    sod it then i'll stick to the original plan above and find some other use for the spare metal.. i may cock bits up yet anyway so it's good to have back up i suppose.. plus i can use some scraps to set the welder up properly before i go at my good cuts

  10. #120
    are these 100% the only steppers suitable for my machine??

    Nema23 Stepper Motor 3.1Nm x 3

    and these the only option for drivers to suit them??

    Best Selling! Wantai Stepper Motor Driver DQ860MA 80V 7.8A 256Micro CNC Router Mill Cut Laser Engraving Grind Foam-in Motor Driver from Industry & Business on Aliexpress.com

    i'm just asking so i can cost up the rest of the machine and them 2 seem to be the least popular models i'm coming across, seen plenty of 425oz steppers

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