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  1. #21
    After hours of design i come back with 3 final (!!!!) plans.

    Plan A
    ( i have already post it but i repost it near the other two plans )
    It is the most simple within the other two and also needs the less steel
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    Plan B
    It is the heaviest within the other two
    The difference with A is that the beams of the cutting table are lieing between the two X axis rails support beams. It also have extra 40X40 beams for reinforcing X rails beams
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    Plan C
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    This plan combines A with B. The beams of the cutting table have been welded as plan A and the reinforcing of X axis beams is as plan B

    All plans are made with 80X80 box section steel. Plan B and C also have 40X40 diagonal box section between X axis rails support beams
    I am waiting for your advices
    Thank you
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by ba99297; 31-10-2013 at 11:08 AM.

  2. #22
    Plan A must be strong enough for this size machine. I know that silyavski likes to have the horizontal beams supported at 2 points like your end view but you loose the triangle in the middle and that is not good.
    Also where there are no diagonals or triangular pieces on the cutting table to stop it twisting.
    Having said that it will still be very strong if you make it like the drawing.

  3. #23
    I know that silyavski likes to have the horizontal beams supported at 2 points like your end view but you loose the triangle in the middle and that is not good.
    If you notice all the three plans carefully you will se that the x rails supported beams have contact with the ground at 3 points not 2. It is possible you get confused between the side and the front view.
    At the side view you can see that every pair of supported rail beams has straight contact in the middle with the groun as my plan have 3 ( red ) foot at every side.
    From left to right i upload Isometric-Top-Front-Side view for every plan
    Also where there are no diagonals or triangular pieces on the cutting table to stop it twisting.
    You are right about the diagonals. I will put them to the plan. Thanks for your advice
    Last edited by ba99297; 31-10-2013 at 04:40 PM.

  4. #24
    Is there any need for the bars connecting the legs at the bottom. I'm constructing mine at the moment, interested in the replies.

  5. #25
    Quote Originally Posted by alex wight View Post
    Is there any need for the bars connecting the legs at the bottom. I'm constructing mine at the moment, interested in the replies.
    Alex, that is a very good point. I think the only reason they are in there is to provide a means of adding triangulation support in the horizontal plane at ground level ( i.e. some metal to weld the triangulation members on to) but if enough triangulation was put into the cutting bed maybe that would be enough ? I'm also at this stage in my build log and reluctant to start cutting the metal yet as I feel the best solution has not yet been reached.

    ba99297, I was referring to the front view, the dark colour one.
    Last edited by EddyCurrent; 31-10-2013 at 09:21 PM.

  6. #26
    I've built one of my sides, roughly the same design, but without the material connecting the legs. As there's angled supports at the top, it should be strong enough. It's had the go ahead, so I'm happy to continue with the other side.

  7. #27
    Quote Originally Posted by alex wight View Post
    Is there any need for the bars connecting the legs at the bottom. I'm constructing mine at the moment, interested in the replies.
    Actually no need, that's what i said before. Or they cut be cut in 2 and raised higher at the middle of the M, that's what i suggested before.

    With 80x80 profile or bigger the machine will not twist , so no need for triangulation on the bed itself. remember that the spoilboard willnot permit eventual twist there.

    However for the sake of absolute rigidity i would have soldered additional plate vertically along the center beam of the bed itself , that will strengthen immensely the bed

    PS. option 1 looks perfect
    Last edited by Boyan Silyavski; 01-11-2013 at 10:38 AM.

  8. #28
    Any of these are strong enough but the design can be simplified regards building and be just has strong. No time at moment to get into full debate about why etc but here's frame I've drawn that's similar.

    Main points are the sides and Bed are welded flat has separate units then joined together with end braces etc. The Bed being a separate unit means the outer frame pieces support the bed material at the edges, the way yours is drawn the edges will be unsupported and could bend or flex under cutting conditions.
    Lower diagonal braces help keep machine frame square and stiff, remember it's not just strength you have to consider there's resonances to deal with and bracing helps reduce resonance.

    Welding major parts in sections on a bench then either welding or bolting together is much easier than struggling trying to weld individual pieces together and keep every thing sqaure and flat, aligned etc.

    One other note.!! On this design the top rail extends.? This is to make full use of the Bed without wasting material having the bed/frame longer than needed which can't be used.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  9. #29
    Quote Originally Posted by JAZZCNC View Post
    One other note.!! On this design the top rail extends.? This is to make full use of the Bed without wasting material having the bed/frame longer than needed which can't be used.
    Good idea and after all these frame discussions I think I'm now at a stage to start cutting metal this weekend.

  10. #30
    Deans design is very good, after all he is far more experienced at building and dealing with vibrations. I like the Z at the baze, that would definitely help with resonance. I like the extra bed frame, i have thought it but never included it in my designs, due to extra weight.


    Dont get me wrong on what i will say, but i am fan of simplicity. I will say the same what i said to Tony at his thread

    Look at that design below and adjust it to your needs if you like it. Just don't change anything radically, cause in its deceiving simplicity there is a lot of reason. In fact 2-3 months of reasoning. There are no random distances there. Tony changed it a bit and you can see his great looking machine. He made it from 80x80, mine is 100x100x3
    If you look at my thread i have a frame soldered in my garage with the same design and it has deflection under 100kg of load which is irrelevant.

    Now what Dean says about resonance is true. Its not the same as stiffness. In fact in some cases the stiffness will help the resonance, especially in our case where we build machines from thin walled profiles.The great thing about my design is that all the forces are working only at the upper part of the structure, its stiffness does not depend at all of lower elements. The legs are just legs / i am talking about 100x100 or short 80x80/.

    Now there are hundreds of points why resonance will not happen at all in the machine i am building, nor twist or bending, even if i were able to route deep aluminum and why not steel / which will not happen cause i limited it with 0.8kw spindle/ . This points are too long to explain, but be careful, cause these are particular decisions, like that the machine i am building will have 100mm thick MDF bead, underneath plastic sheet or aluminum sheet and etc...

    Long story short, just take a look and study it. Use it if you like it. It implement Deans idea of the shorter table. Also implements subtle ways of dealing with resonance, like the beams of the bed gradually don't coincide with the short vertical ones. In fact in my next build everything will be slightly offset here and there, to kill the harmonics.
    The best thing is if like Dean says the bed beams flex, at a later time can be added ribs bolted to them vertically and if there is a twist , you can add the same Z diagonals like in Deans drawing of the lower part just drilling from below and bolting. Add if when you need, why overbuild now? Not to speak of that with 100x100 profile is way overbuild as my measurements show on my build.



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