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  1. #41
    After thinking that welding all the beams together, according to the previews plans i would have issues with the big weight, i decided to split the contruction into two , the bench and the CNC that will sit on that bench.
    So i introduce the CNC pictures first
    So i have the main frame
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    Then with the red color is the cutting table made by 80X80X5 beam
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    over the cutting table i will put aluminium profile tha will be bolted on the red cutting table. That profile has T slot for clamping item that will be cutted
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    And here we have some picures of the construction with all the items together
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    if i want more depth for 3d cuts i will remove the cutting table(80mm) with the T slot( nearly 40mm) and i will put a 20mm mdf. That will give me about 100mm (80+40-20) more depth

    I am waitting for your comments

    Thanks

    Vagelis

  2. #42
    Nice. Looks great,

    What size of the steel profile you decided on? If 80mm or bigger, you don't need the triangular plates. Believe me, will not move. Reason - the short profiles will hold it firm enough. If you insist, make them L shaped, so they will not bother you fitting longer than the table pieces.

    And as for the size of profile, i am with Jonathan. Bigger the profile, the better. If resonance, its easier to drill a hole and fill it with something later.

    I said it earlier some where but one of the best ways to fight resonance is avoiding perfect symmetry in the machine, meaning all pieces spaced same distance and mirrored exactly. Offsetting each piece even by 1cm here and there will have enormous impact. Same when avoiding mirroring

  3. #43
    Quote Originally Posted by silyavski View Post
    Nice. Looks great,

    What size of the steel profile you decided on?
    At the above plans i use 80X80X5 beam for the red table and also for grey frame except the 4 lower beams that will have contact with the bench. Those four beams are 100X100X4. I think that the triangular pieces will help to achieve triangulation and parallelism and also stiffness.
    I agree with you that if avoid symmetry and mirroring that will help to reduce resonance. As for the beam size i think even 80X80 or 100X100 will not have much difference to the final result.
    The t-slot profiles are aluminium profiles that are used for for clamping solar panels at the roofs. I design the profile from a piece that i had.
    I will come back with the gantry design. I will use one motor for X axis with double ballscrews and i may use double nut (preloaded with a spring) for each side
    I want you opinion about this option. What kind o f spring is suitable for this use and where can I find it. I also would like to know what would be a good distance between Y and Z axis profiled rails ( i will use 20mm profiled rails ). Also what will be a good distance between the carriages of X axis ( outer side of carriages )

    So far thanks everybody for the help

    Vagelis

  4. #44
    Hi Vagelis,

    Looks ok to me. . . . Just a Couple of simple things that will help.

    You could drop those inner triangle braces and just keep the inside corner ones but make them little larger, there will be more room with others gone. Not much gain strength wise from them being there and not having them means less welding which will lessen the chance of heat distortion.! . . . . Would do the same with corner braces for the Bed frame just to help keep it square.

    Also the outer End triangles will be better placed on the outside of the box section and made larger so there is more contact area, they will also cover the ends of the section. Then when you weld just put short welds but on both edges. Again this lessens the chance of heat distortion by allowing short weld runs and balancing the welds pushing/pulling action.

  5. #45
    Dean i made some corrections according to your advices. I am not sure i understood everything you said ( as my english are not excellent)
    Let the photos talk

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    In order to go on with the plans, it would be good if somebody told me about Y and Z rails distances and distance between carriages of X axis. Finally i want your advice about X axis double preloaded ballnuts

    Thanks

    Vagelis
    Last edited by ba99297; 30-12-2013 at 02:11 PM.

  6. #46
    Hi Vagelis,

    Normally people here on the forum use ball nuts and ballscrews bought from China. The most recommended vendors are Fred from BST Automation/aliexpress/ and Chai from linearmotionbearings /ebay/. BST for sure can provide the double ball nuts , i assume Chai also. No reason to buy 2 single, but depends on the design. On Jonathans build i asked about the spacers spring washers, he pointed from where, so the info should be somewhere there. Their prices are very similar, both do perfect machining, so really its up to you.

    To resume various advices for my builds, that i received mainly from Dean and Jonathan , for your size machine
    if stepper driven 1:1 with short belts and pulleys on all axis:
    -short belt HDT5 15 size, if heavy gantry maybe 25 size, pulleys 20t
    -z 1605 screw
    -gantry 1610 screw if mainly woodworking for faster speeds ,1605 if mainly aluminum
    -long axis 2010 or 2005 respectively, i see no reason to go to 25xx size

    the following is my personal understanding:

    -gantry supports ~ 30cm/normal/ to 40cm/heavy duty/ spacing of the bearing blocks , this including the blocks-
    -gantry , depends on the design, but ~20cm spacing vertical and 25 horisontal i see as minimum./ including bearings./ 30 and 30 will make very strong machine/

    PS. Dont be cheap and buy Hiwin or cheaper Chinese square rails not round
    Last edited by Boyan Silyavski; 30-12-2013 at 05:31 PM.

  7. #47
    Quote Originally Posted by ba99297 View Post
    Dean i made some corrections according to your advices. I am not sure i understood everything you said ( as my english are not excellent)
    Let the photos talk
    Yes you have it correct but you can afford to make the triangles little smaller to avoid interfering with material, Or shape them to do same thing.

    Now regards the Gantry bearing spacing then 300mm for X axis(long axis) and 200-250mm for Y axis will be fine for most work. Like Silyavski says the wider the more stable but the figures I've given I know work fine esp when using profiled linear bearings.

    Regards the twinball nuts then I never use twin ballnuts so can't help here and to be honest I don't see the need for a router type machine. They are Ok for a Milling machines that need to hold tight tolerances but in this case I think your just adding extra expense and work, along with extra maintenance for gains that you don't really need or will probably never see due to other weakness in the machine.?

    Remember the machine is only good has it's weakest link and at this size then a single ballnut won't be the weak link so any gains won't be fully seen and the gains you'll get from 2 nuts over 1 nut will be very small to start with and I honestly think you won't see any improvement worth the effort or expense.!!

    Ballscrew sizes and pitch then

    20mm Diameter 10mm pitch for X axis, don't go with 5mm pitch even if aluminium just change the gearing on the pulleys. Don't use 25mm diameter far to large.!
    16mm Diameter 10mm pitch for Y axis, don't go with 5mm pitch even if aluminium just change the gearing on the pulleys. Can use 20mm if you like thou won't accelerate quite has fast 16mm but it will still be plenty good enough and that bit less likely to whip.
    16mm diameter 5mm pitch for Z axis.
    Last edited by JAZZCNC; 30-12-2013 at 06:14 PM.

  8. #48
    You guys are a treasure
    Your advices is for me GOLD
    I go on with my plans. I add profiled rails and carriages ( downloaded from hiwin site). Before I go on with my gantry design I would like your opinion about the issues that I will come up with. What are the the points that I have to be careful. This is my progress

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    But I am wondering if the ballscrew sould be placed between the two 80X80 beams of the gantry, in front of Y axis (near z axis ) or in the back of Y axis. I also wonder about the best way to connect Y axis with X axis carriages.
    Any idea will be helpful

    Vagelis

  9. #49
    Quote Originally Posted by ba99297 View Post

    But I am wondering if the ballscrew sould be placed between the two 80X80 beams of the gantry, in front of Y axis (near z axis ) or in the back of Y axis. I also wonder about the best way to connect Y axis with X axis carriages.
    Any idea will be helpful

    Vagelis

    Hi,
    many different schools of thought here. Basically depends on what you aim to achieve, what rigidity you aim for, the overall weight of gantry you will finish with, and how you intend to move this weight, how fast and not at last the money that you can spend on the structure, the motors and the drivers.

    To resume it all for the gantry sides: 1 side plate like at the drawings could be ok if you keep the gantry not raised, directly on the sliding plates, if you raise the gantry you will have to do a profile like structure to make it stiff and strong in all directions/ possibly from 10mm thick steel sheet will be best/. There is a calculator in the sticky post for that purpose.

    Now to the gantry drawing itself. Have in mind that this is not the voice of experience, i am like you building now my 2 first machines, however i gave it a lot of thought:

    The typical:

    -Screw at the back will work, many make their machines that way, combined with the rails on top and bottom of the gantry. That is how i designed my first build.
    Points to consider: more complicated Z design, rails need more time to be aligned, care should be taken for the Z strength in all directions.

    -Screw in the middle. Great design, but most do it from aluminum-plate at the back and plate at the front with channel in the middle. While i like it i did not choose it due to expensive material, my inability to process it at home precisely-cutting, drilling tapping...etc., Beautiful but quite costly. Of course it could be done from steel plate, but then the combined weight. Or ribs here and there at the back, but still without a front plate will not be strong enough to my liking. Plus the plates will protect the ball screw.

    -The typical commercial router, rails on the front plate, screw inside, raised gantry. I could not help but post the picture of the Techno, which is a typical example
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    If into woodworking and sheet material ok. But not a multitask one. Man, how i hate that design . The z could go left right further, so the table could be not so wide, but then the gantry raisers should be strong enough, then the Z travel is very small, so if we want travel of 200mm then the weight, then the motors...etc.

    Other:
    There are other designs but as they are very purpose specific i would not recommend them.
    You could take a look also of my design of gantry on the second machine i am starting to build.I hope will be successful. Its meant for strength and precision for the long gantry, also an ease of implementing, especially epoxy leveling the rails . Just as an idea that you could further develop if you like it http://www.mycncuk.com/forums/router...html#post52573, though more soldering, various sizes profile, heavier.


    At the end the design is choosing between the various trade offs for the purpose of what will suite you most.

  10. #50
    Hi guys
    Quite a long time since my last post
    I am thinking about an arrangement for the gantry of my machine
    Before i go on with the plans i want your advice about the basic idea
    Three 120X60X3mm beams will be welder making a C shape
    In front of this "C shape" a 15mm aluminium plate ( blue color) will be bolted in order to bolt on this plate the profiled rails
    The plans are not accurate, so any imperfections will be corrected. I just want your opinion in order to see if this arrangement is good or bad an then go on with the way i will attach the gantry on the carriages.
    The gantry will be pulled by two Yascawa servos 400 watt and a 2010 ballscrew
    Thanks for you time

    Vagelis
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