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  1. #1
    First of all I want to say hello to everyone and thank you for sharing with their experience and knowledge!


    After a year or so reading on CNC forums I decided that I have more knowledge about it than before and I think I'm ready to go to the next step.
    But first of all I would like to hear from more experienced members than I about my CNC design and hardware, any input or criticism are more than welcome guys.

    So there is a components which I decided to use in my build:

    Whole machine will be from aluminum, plates (10, 20 and 25 mm thick) and profile 45x90
    Ball screw for the X - RM 2005-RM 2010 ???, with fixed + fixed ends
    Y - RM1605-RM1610 ???, same as X fixed ends
    Z - RM1605
    Hiwin profile rails, X-25mm, Y and Z 20mm
    Nema 23 motors 320 oz-in 2.8 mH 3.5A, all axis
    48V 12.5A power supply
    Gecko G540 4 Axis stepper driver
    Water-cooled spindle motor 2.2kw with a VFD

    oh yes, I forgot to say that is cutting area is about 1220x845 mm

    So that is all for now, Thanks again to all and good luck to everyone !

    Excuse me for my bad English


    Gytis


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  2. #2
    X isn't long enough to warrant a 20mm diameter screw, so use RM1610.

    Gecko G540 is a waste of money - get something like this:
    CNC Micro-Stepping 57 Stepper Motor Driver 2M542 2phase 4.2A Switch Controller | eBay
    Or better, a higher voltage driver, like DQ860MA - cheap at AliExpress.com - Online Shopping for Electronics, Fashion, Home & Garden, Toys & Sports, Automobiles from China.

    These motors are good and probably cheaper than what you specified.

    25mm profile rails are completely over the top, so unless you've found some cheap ones on eBay I'd go for smaller rails - even 15mm would be fine for this size machine.

    Your gantry could be made a lot stronger without using more material - flat plate is the worst cross section for the gantry since the forces are often in the direction where it is weakest. Box section would be better, or even better remove the gantry sides and have the Z-axis operating below the level of the X-rails.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  3. #3
    Hello Jonathan, and Thank you for your reply !



    X isn't long enough to warrant a 20mm diameter screw, so use RM1610

    well, you are right., I was thinking same as you., but when I got my first ball screw RM1605 1m long it was bent about 5 mm in the middle, so I can just imagine what will happen with 1.6m long screw


    Gecko G540 is a waste of money - get something like this
    These motors are good and probably cheaper than what you specified.
    I can not argue with you about the drivers and motors, probably you are right .,
    but : 1. I already have one G540
    2. maybe I have spent to much my time on American forum before I found you guys in the UK (so there is reason why I have chosen these drivers and motors)

    25mm profile rails are completely over the top
    I'm not sure about 15mm rails, it seems to me that is too weak

    or even better remove the gantry sides and have the Z-axis operating below the level of the X-rails.
    no, I don't like this design, I want to keep open table design and keep rails & ball screw from dust as much as I can

    And finally, this machine will be built not for hobby use, she has to be strong and durable


    Thanks

    Gytis

  4. #4
    Hi Gytis,

    First don't listen to Jonathan the G540 is a great bit of kit for a small machine. There are cheaper but it's a quality unit with great back up and warranty from Gecko and worth the money.

    BUT every thing else he's correct about.

    Quote Originally Posted by Gytis View Post
    I'm not sure about 15mm rails, it seems to me that is too weak
    15mm profiled rails will be plenty strong enough and carry far more load than you'll put on the machine.
    The only issue with smaller profiled rails is the small bearing blocks can be a pain, esp with making the Z axis has the low height often means using spacer blocks to allow clearance for ballscrew etc. I find 20mm a much better size bearing and plenty on top of the job.

    Quote Originally Posted by Gytis View Post
    no, I don't like this design, I want to keep open table design and keep rails & ball screw from dust as much as I can

    And finally, this machine will be built not for hobby use, she has to be strong and durable
    Your design will be substantially weaker than what Jons suggesting and if you want strong and durable then it doesn't get much better.
    Has for keeping the screws protected then that's easy enough with a bit of thought regards covers etc. The high sides don't cause any issues in use for most work and actually help contain the cutting mess to the table area instead of slinging it all around the shop.
    The advantages of the much increased strength and far better quality of finish on work combined with allowing higher feeds is well worth the sacrifice of bit of access when loading material. End of the day it's the quality and speed of cut that matters.

    Both Jon and I have been there done/seen that route so believe me we speak from experience on this.!!
    Last edited by JAZZCNC; 06-07-2013 at 03:00 PM.

  5. #5
    Hello JAZZ, and thanks for your input !

    Your design will be substantially weaker than what Jons suggesting and if you want strong and durable then it doesn't get much better.
    Has for keeping the screws protected then that's easy enough with a bit of thought regards covers etc. The high sides don't cause any issues in use for most work and actually help contain the cutting mess to the table area instead of slinging it all around the shop.
    The advantages of the much increased strength and far better quality of finish on work combined with allowing higher feeds is well worth the sacrifice of bit of access when loading material. End of the day it's the quality and speed of cut that matters.
    now I'm sitting and scratching my head ..,
    new design?, short as possible sides?, Z-axis below the level of the X-rails?, Hiwin rails 15-20mm?


    Gytis

  6. #6
    Quote Originally Posted by Gytis View Post
    Hello JAZZ, and thanks for your input !
    now I'm sitting and scratching my head ..,
    new design?, short as possible sides?, Z-axis below the level of the X-rails?, Hiwin rails 15-20mm?
    Don't despair thats par the course with first machine.!!. . . I had full head of hair before getting into CNC now I'm follicle challenged. . Lol

    To be honest I may have jumped the gun slightly because I didn't ask what you intend to cut with this machine.?

    If soft materials plastics,softwoods etc then the high sides won't be a problem. There's no disputing the high sides are weaker design than no sides design but they do work ok in soft stuff if rest of gantry is stiff enough.

    That said sorry to say your gantry design is very weak and the single piece of plate for gantry is real bad idea. Also the Y axis ballscrew hanging down is just asking to get clobbered with rubbish.

    Look around the forum you'll see pics of similar built high side machines with strong gantry's, I've posted pics of similar machines I've built that use profile which is strong design and can handle cutting upto light aluminium work.

  7. #7
    If soft materials plastics,softwoods etc then the high sides won't be a problem
    you wouldn't believe me, but I was almost sure that I will be able to cut hardwood and do light aluminum work (now you can laugh of me)

    Ok., I think I know what you both trying to say for me..,
    so now in my head I have new CNC table plan ( I hope it will cut at least hardwood ).
    Version_2 will be here soon

    Thanks guys for the advice!

  8. #8
    Hello,

    quick update., the Version_2 is nearly done.
    now I thinking about X axis ball screw fitting,
    my very first idea was to put it between the aluminum profiles, but now I'm not sure or it good idea, I think distance is to big between rails and screw approx.150mm?
    what if I run it through the side plate support box?, right now there is few brackets., just one what I do not like, that the screw will be very few cm. above the table.
    But maybe I can fix on each side of the box some brush or seal to wipe the dust away from screw ?

    btw, what about design? Version_2 will be stronger then the first?

    Thanks
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  9. #9
    There are two areas that look like they need strengthening on that design. The bed plate needs support otherwise it'll bounce and flex like nobody's business and you'll get a crap finish. Can you not just use the profile as the base and put profile laterally across under the bed plate to stiffen, seems like there's an awful lot of empty height under the bed plate?

    The Y axis plate also looks like it needs a length of profile or two behind it otherwise it might also flex when cutting in the middle of it.

    Hope this post doesn't sound negative, just a couple of observations :)
    Neil...

    Build log...here

  10. #10
    There are two areas that look like they need strengthening on that design. The bed plate needs support otherwise it'll bounce and flex like nobody's business and you'll get a crap finish.
    Hello Neil,
    I just forgot to mention that now I working on Z axis, and this table top sitting just to see what travel I need in the Z or how low bed has to be.

    Sorry for confusing you

    Gytis

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