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  1. #1
    Hi Everybody
    My name is Vagelis and I am from Greece
    I would like your advice and your opinion on the plans below.
    Involving a cnc (1500mm x 1000mm) which
    will runs with Yaskawa servo 400 watt
    Supported profiled rails 20mm, ballscrews X, Y 20mm Z 16mm
    Spindle 2,2 KW water cooled

    The following plans have to do with the table
    I want to make something stiff and adjustable
    The main table is made with 80X80 5mm square tube and the X axis rails will be placed on two ( each side ) I beams. The one I beam (120mm height) will be welded on the table and the above will be adjustable up-down left-right with screws. Before i go on with the plans i think that it will be good to get some opinions from the "experts" as i am amateur at cnc constructions ( sory for my english).
    My main concern is if I beam is suitable for this purpose, or it is better to go with 120X60 5mm tube
    The cutting surface will also be adjustable from the brown L shape angle that can be moved up and down.

    Thanks everybody for your time
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  2. #2
    Vagelis,

    I am an amateur like yourself but have recently read a lot of information about cnc machines. I am designing a frame myself at the moment using 50x50x3 steel box section, my work area will be about 1000x650.
    You see where you have two crosses in the side panels, I think if you had just 2 diagonals like this I/I\I it would be enough because you just need to create a triangle. For your size machine I would say the 80x80x5 might be more than you need but if you are fine with that then more is better than less. The I beams I would change for box section because I beams are not so good with twisting and you might get more sideways twist than you would with box section. Also you have not put any diagonals at the ends like you did with the sides. Good things you have included are 3 legs each side, adjustable feet, adjustable top I beam to get the top surface straight. Looking at the drawing, I can't see much adjustment on the brown angle and wonder if it's worth it other than making sure the table is the same height under the cutter across all of the table.
    Last edited by EddyCurrent; 11-10-2013 at 10:56 PM.

  3. #3
    In my opinion your legs are overbuild and the rails support underbuild.

    The I beams are bad idea.

    After a lot of thoughts and considerations for me:
    -a whole machine build from 80x80x3mm with a careful design could be the best solution for a DIY sturdy CNC
    -a whole machine build from 100x100x3mm with careful design could be a real beast of a DIY extremely sturdy CNC

    The people who build with more than 3mm thickness either have a design which is not so perfect or are pro builders who know what they are doing and definitely its not their first machine, usually some beast with a special heavy duty purpose


    It would be nice if you take your time and read the entire Tony CNC build here where he started with similar to yours idea, the calculations of the price and weight, how he implemented and personalized the design from another build of mine adjusting to his dimensions and needs.


    More or less i could say that the particular design of mine could hardly be beaten for strength, weight and $$$ combination, permitting the final result to be extremely sturdy CNC with deep 160-200mm Z travel.
    The trade offs are that it is better to be all soldered and adjust the table bed by fitting thick table bed instead of raising and lowering the bed structure itself.
    The plus is that its very easy to cut to size, one profile only, cheap, very easy to solder precisely and completely scalelable from small to big machine.
    the gantry could be made from 2 profiles soldered together so finally will be 200x100 or 160x80, which both a are great and in the ideal range for 20 size supported rails

    Its not tested on a finished machine, but i am currently building one and can assure you is steady like a rock. If you scale it, mind the distances between every element and don't change them, just add or take elements to make it bigger or smaller.
    Its deceivingly simple but many things are taken into consideration.

    Hope that it helps.

    My advice is when comparing designs take the calculator and see the KG and what you receive for these KG in strength. Then compare. Every KG is an euro

    Click image for larger version. 

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    PS. FYI just went in the garage and measured the deflection of my machine under 100kg weight/me/. Its very similar, with different measures. Table bed is 67cm wide and is 135cm long. So stepping on any of one the table bed beams gave me 0.05mm deflection of that beam and stepping on any of the sides that that support the gantry/supported at both ends only/ gave me 0.03mm deflection. So keeping the design and not under doing something when everything mounted will give you real life deflection which is unmeasurable/or for sure less than 0.05mm/ . So my machine with mine particular dimensiones with table bead mounted will have over all deflection of less than 0.01mm. isnt it great?
    Last edited by Boyan Silyavski; 11-10-2013 at 11:52 PM.

  4. #4
    Thanks everybody for your advices
    The basic conclusion is that I should replace the I beam with square profile. That was what I have in mind from the beginning. The reason that I choose I beam for the drivers support, was because it was easier to connect the two I beams ( upper and lower ) with bolt and nuts in order to have a fully adjustable table.
    The plan that you suggest me to make Syliavski looks very strong and stiff. My question is how am I going to adjust that table if I have imperfections as cause of arc welding. The basic advantage of arc welding is the stiffness, on the other hand if I only weld and have no ability to adjust with bolts, I think is more than sure that my X axis rails wont be on the same plane. So I think that I will keep the solution of the bolt adjustment an replace the I beams with 80X80X3 or 4mmsquare beam. The Chinese says 1 picture 1000 words, I will design it and I will come back. Meanwhile I will be glad to hear any suggestion.

    Thank for your time

    Vagelis

  5. #5
    Quote Originally Posted by ba99297 View Post
    Thanks everybody for your advices

    The plan that you suggest me to make Syliavski looks very strong and stiff. My question is how am I going to adjust that table if I have imperfections as cause of arc welding. The basic advantage of arc welding is the stiffness, on the other hand if I only weld and have no ability to adjust with bolts, I think is more than sure that my X axis rails wont be on the same plane. So I think that I will keep the solution of the bolt adjustment an replace the I beams with 80X80X3 or 4mmsquare beam. The Chinese says 1 picture 1000 words, I will design it and I will come back. Meanwhile I will be glad to hear any suggestion.

    Thank for your time

    Vagelis
    Hi Vangelis

    - between 80x80x3 and 4mm, the best choice is or 80x80x3 or 100x100x3 .
    Why?
    80x80x3 1m=7.17kg/m
    80x80x4 1m=9.47kg/m
    100x100x3 1m=9.02kg/m

    Looking at their properties from my suppliers brochure the conclusion is that roughly the second is 20% stiffer than first and the third is at least double stiffer, hence for the same weight ~9.kg the 100x100 x3 will make quite stiffer machine structure



    About soldering:

    With careful thinking and careful soldering and only 2 big clamps i achieved a structure where not only is up to the mm precise but the beams are on one level and the supporting beams are on one level too. Nevertheless i will use Epoxy to level bellow the supported rails. As suggested by fellow members here i bought West system Epoxy with Hardener
    from dansonmarine.co.uk who will ship in europe, contact them.
    1kg of 105 resin and .33kg of 209 hardner, £45.00 per pack +£17 to Spain
    Delivery is £17.00 to spain

    It took me a whole day to weld it and i would not go other way. You can do it with a helper, 2 or even better 4 big clamps and a 2m aluminum profile or a real straight edge.
    there is an procedure that has to befollowed, check my build or if you dont understand i will explain later.But mostly it consist of designing and welding "stair like" the individual assemblies, which at the end are soldered together in a "stair like" fashion. That means left and right part of the table should be finished first and then connected as suggested above.

  6. #6
    Hello Vagelis,

    Following your PM I did see this thread and forgot to post Sorry.

    First Agree with Silyavski that your double I-beam design is bad idea and would drop it like hot potato.

    Also agree that a fully welded Bed is slightly stronger but it doesn't allow easy adjustment if you need large items and having raising platforms like suggested can be inconvenient and take up space for storage.!

    To decide which best suits your needs then you'll have to consider closely what your cutting needs are.? . .If you only plan to raise the bed to say just cut Aluminium so bringing table surface closer to spindle a fixed amount every time then go with the fixed bed and build raising platform to suit. (If you have room to store it.!!)

    But if you what to cut a range of material thickness's then adjustable bed is the better option. If designed correctly and built strong then the strength difference is negligible for most cutting conditions except really heavy duty or very hard materials, In which case you have probably built the wrong design machine.!!

    Now regards the table Bed and getting it parallel to the cutter then don't worry this is not a problem.? Because every time you move the bed or in Fixed bed case Add the raiser block you MUST surface the table to be sure it's parallel to Cutter.
    This also means it doesn't matter if the adjustable table isn't perfectly level or even in twist because after being surfaced it will be parallel to cutter and thats all that matters.

    NOW what is VERY VERY important is that the X axis~(long axis) rails are on the same plane and not in twist.!! This is where all your efforts need to be concentrated on getting correct. The Bed could be Banana shaped and slopping at an angle it doesn't matter because after surfacing it will be flat and parallel to cutter BUT ONLY if the X axis rails are on the same plane. Any errors in this department affect the whole machine.

    Several ways to ensure this but really only 2 that are realistic to the DIY builder. These are Epoxy levelling or adjustable top rail and careful measurement.
    Epoxy is probably the easiest because it doesn't require accurate straight edges or equipment.! It's just more time consuming because of prep to surface to ensure clean and setting up dam walls and bridge etc . . .Plus it's messy and requires clean up afterwards!.

    Thou For first time builder then I'd probably suggest taking Epoxy route has it's easier to ensure rails are on same plane and doesn't require machines to ensure top rail is surfaced flat.


    Quote Originally Posted by silyavski View Post
    - between 80x80x3 and 4mm, the best choice is or 80x80x3 or 100x100x3 .
    Why?
    80x80x3 1m=7.17kg/m
    80x80x4 1m=9.47kg/m
    100x100x3 1m=9.02kg/m
    Now regards this Silyavski then there's little more to it than just weight.? The thicker material will lessen resonance and resonance affects the quality of cut, it can also affect motor performance to some degree and I recommend Digital drives with good resonance damping built in if building from steel. Also fill the Tubes with sand for best affect.

    Some times it's better having less speed but Stiffer machine with less vibrations than trying to save weight. Again this depends on what your doing with machine.

    Let me say for cutting anything below Aluminium these steel built machines are massive overkill and would need huge spindle power to achieve the Depths of cut and feed rates that would stress the frame or make it become the weak point.

    For Cutting aluminium or harder materials correctly to high standard requires a certain attention to design and detail that is very hard to Achieve, just look at Jonathans latest post about his friends excellent machine to get an idea of what's needed to do it correctly and I'd even say this is a minimum requirement if high standard of finish and feed/DOC rate is needed.
    This is just medium sized machine and with every 100mm wider or longer the level of engineering gets more and more important and harder to achieve accuracy.

    So my Advise is THINK CAREFULLY about your cutting needs and be REALISTIC about feeds/DOC etc you expect to achieve.
    No point using a Sledge hammer to crack a nut and same goes with cutting wood, Machines built to this level are Sledge hammers to wood.!! . . . . Build it just stronger than needed for the Job it's doing, any more is waste.

    If you need to mainly cut aluminium and correctly then build a different machine designed to do the job correctly.!!

    If you want one large machine to do all jobs then it will have weak spots in every area, it CANNOT Excel at cutting every material just impossible to achieve realisticly.!!
    Last edited by JAZZCNC; 15-10-2013 at 04:35 PM.

  7. #7
    This is how I plan to do my top rail.
    legs 50x50x3 steel box
    top rail 100x50x3 steel box
    6mm or maybe 10mm plates welded on top of the legs and welded to the underside of the top rail.
    Bolts will pass through the plates on the legs and will screw into threaded holes in the top rail plates and right through into the box.
    These joints will be shimmed to level the top surface of the rail and to ensure both sides are in the same plane.
    Before bolting the pieces together I will grind the surfaces of the plates flat, checking with a straight edge
    It would be easy to weld 2 further intermediate points if this found to be flexing.

    Click image for larger version. 

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  8. #8
    Quote Originally Posted by EddyCurrent View Post
    This is how I plan to do my top rail.
    legs 50x50x3 steel box
    top rail 100x50x3 steel box
    6mm or maybe 10mm plates welded on top of the legs and welded to the underside of the top rail.
    Bolts will pass through the plates on the legs and will screw into threaded holes in the top rail plates and right through into the box.
    These joints will be shimmed to level the top surface of the rail and to ensure both sides are in the same plane.
    Before bolting the pieces together I will grind the surfaces of the plates flat, checking with a straight edge
    It would be easy to weld 2 further intermediate points if this found to be flexing.

    Click image for larger version. 

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    That's pretty much I do my rails but to make life simpler and do away with grinding and shimming etc I spread a layer of Epoxy putty on the bottom plate. Then I put layer of plastic between rails and plate then lightly tighten together pushing some excess out then set the rails on same plane and parallel etc. The putty gives plenty of time for adjustment and dries hard has metal.
    It has dampening quality's has well so helps with vibes transferring thru frame. It drills and taps easy and fills any voids, I can shape to match radius etc and it easy grinds and sands if needed.
    When set 24hr later I have a perfect hard surface that sets rails exactly on same plane. The rails can be removed and go back exactly on same level so no messing around with shims etc.

  9. #9
    Sounds like a plan, plastic metal would be okay too, I have some of that.

  10. #10
    First of all thanks everybody for the participation to the thread.
    Next i would like to introduce some of my conclusions and ask some things about all these that i have already read

    1. I beam will not be used
    2. For the rails support beams I am between these profiles
    80X80 4 mm
    80X80 5 mm
    100X100 4 mm
    100X100 5 mm
    and for the table structure
    80X80 4 mm or
    80X80 5 mm
    i want your advice


    Jazzcnc wrote
    Now regards the table Bed and getting it parallel to the cutter then don't worry this is not a problem.? Because every time you move the bed or in Fixed bed case Add the raiser block you MUST surface the table to be sure it's parallel to Cutter.
    Jazzcnc when you say "MUST surface the table to be sure it's parallel to Cutter" you mean that the spindle should make a full pass over the cutting table and milling the table surface ?


    Jazzcnc wrote
    NOW what is VERY VERY important is that the X axis~(long axis) rails are on the same plane and not in twist.!! This is where all your efforts need to be concentrated on getting correct. The Bed could be Banana shaped and slopping at an angle it doesn't matter because after surfacing it will be flat and parallel to cutter BUT ONLY if the X axis rails are on the same plane. Any errors in this department affect the whole machine.

    Several ways to ensure this but really only 2 that are realistic to the DIY builder. These are Epoxy levelling or adjustable top rail and careful measurement.
    Epoxy is probably the easiest because it doesn't require accurate straight edges or equipment.! It's just more time consuming because of prep to surface to ensure clean and setting up dam walls and bridge etc . . .Plus it's messy and requires clean up afterwards!.
    Here i have two question

    1.when you say "adjustable top rail and careful measurement" you mean the X ( long) axis rails should be adjustable right?
    2.when we talk about self leveling polyester epoxy, is it specific epoxy or common marine polyester can do the job. Should i need a primer in order the epoxy to bond with the metal?



    Jazzcnc wrote
    I recommend Digital drives with good resonance damping built in if building from steel. Also fill the Tubes with sand for best affect.
    When you say "digital drives" you mean the motor drives. I reminds you that i will use 400watt yaskawa servo motors Sigma II generation, and i plan to put all the electronics not under the cutting table but to a separate enclosure in order to avoid vibrations for the electronics.


    My main concern of using epoxy is the aging and the temperature effect to the table. I am talking about contraction expansion. The machine will be placed at my basement where i have temperatures from 8 ( winter ) to 26 ( summer ). Would that be a problem? What will happen if one day i decide to move the machine to another place. The truth is that epoxy look a good and easy solution, on the other hand i donít fell good if i donít have the ability to adjust. Also do we know how epoxy reacts. It is more than sure that epoxy doesnít have the same contraction expansion ratio as steel. I have heard that pro builders that use cast iron, leave the metal for aging for 10 years...
    Thanks again everybody. If anyone has something to suggest i am anxious to hear

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