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  1. #1
    This story is about Steel Gantry Machine with work-area 1500x750x200 for aluminium and wood.
    First I was going for a fixed gantry machine but bigger work-area changed my mind. As long as I have to purchase expensive components the price difference for longer components is not so dramatic - but it gives nice advantage.



    Main frame welded steel 80x80x4mm.
    Steel gantry consist of 2 pcs 100x100x3mm tubes welded together and some 8mm steel plates.
    Z assembly is mostly 25mm aluminium with 2,2kw watercooled spindle.
    Ballscrews X,Y=1610; Z=1605.
    HIWIN 20mm rails all axes. Epoxy leveled.
    Please feel free to comment my design. In case of positive feedback then next step would be to order rails and ballscrews. Measure them and then finalize design and start the build.

    I have couple of questions for more experienced guys:
    1. Can I use L (0,375" = 9,525mm) pitch pulleys with a 12,7mm wide belt from steppermotor to ballscrew? I can get those pulley for free. Together with 240L belt. But this belt is too long and pulley centre hole is 10mm, whish I cant use on Nema 23 anyway. So I have to buy half the pulleys and belts. May as well buy proper with belts and pulleys all around?
    2. What ballscrew machining are you using when belt pulley will be attached?
    3. Hole gantry with Z and everything will be close to 80 kg. Can I put my money on 2x Nema 23 3,1Nm together with a decent 70Vdc PSU?
    4. What HIWIN blocks do most of you prefer: HGH or HGW? Sure it depends from design but I think I will go with HGH20CA from BST Automation.


    Tanks for reading!
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. The bed looks quite low on this, you may find the z axis is unduly extended if cutting mainly sheet material. That said I don't know what you plan to cut? Looks like a nice strong frame, you will want some leaving feet on it particularly if going for 6 legs...

  3. The Following User Says Thank You to JoeHarris For This Useful Post:


  4. #3
    Thanks JoeHarris!

    I would limit Z axis movement with proximity switches to about 100mm + detachable smaller workarea bed when aluminium cutting. This will keep Z in sweet-spot while cutting but also adds weight. I choose unnecessary weight over adjustable bed? But now when I think about it... I will get both actually! Will have to think this over.

    Also I have made some updates to the model.



    Do you think this long 1610 ballscrew will start whipping on X-axis?

    Brg,
    Toomas
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  5. #4
    Hi, good luck with your build!

    Quote Originally Posted by toomast View Post

    Can I use L (0,375" = 9,525mm) pitch pulleys with a 12,7mm wide belt from steppermotor to ballscrew? I can get those pulley for free. Together with 240L belt. But this belt is too long and pulley centre hole is 10mm, whish I cant use on Nema 23 anyway. So I have to buy half the pulleys and belts. May as well buy proper with belts and pulleys all around?
    No.You can but i wouldn't. The correct belt for this build is 15mm HTD . The correct Nema motor has 8mm shaft. The desired pulley is steel 20t. Belt length maximum 350mm

    Quote Originally Posted by toomast View Post

    What ball screw machining are you using when belt pulley will be attached?
    Standard. Puley bored to 10mm -/16xx ball screw/


    Quote Originally Posted by toomast View Post
    Whole gantry with Z and everything will be close to 80 kg. Can I put my money on 2x Nema 23 3,1Nm together with a decent 70Vdc PSU?
    Yes. You are at the limit of it, but given the working area size and my real life experience, you will not need the maximum achievable speeds at all. When we speak of max speeds and similar stuff we refer to heavy industrial application where your machine works full shift trying to produce max result


    Quote Originally Posted by toomast View Post
    What HIWIN blocks do most of you prefer: HGH or HGW? Sure it depends from design but I think I will go with HGH20CA from BST Automation.
    I buy from him and he has both. They are same price. For the gantry legs the wide blocks. Everywhere else the thin ones.



    Quote Originally Posted by toomast View Post
    I would limit Z axis movement with proximity switches to about 100mm + detachable smaller workarea bed when aluminium cutting. This will keep Z in sweet-spot while cutting but also adds weight. I choose unnecessary weight over adjustable bed? But now when I think about it... I will get both actually! Will have to think this over.
    No need for this. As you may know i have designed and build this machine. last week i was cutting aluminum fully extended Z, speed 900 mm/min and 1.5mm deep without any problem. 0.8kw spindle only. From the sound of it i could dig at 4mm with the 0.8kw spindle but still my friend does not have cooling which is critical.


    Use well the spindle itself for strengthening the Z plate.

    However your Z design slightly but critically differs from mine,may be its its weaker, please show better and closer pictures so we could see it in detail/, you could again read when you have time my first build/link in signature/ how exactly i made the Z.


    Quote Originally Posted by toomast View Post
    Do you think this long 1610 ballscrew will start whipping on X-axis?
    No, don't worry about that. Just design it exactly long. I see you are doing it right. It has been commented many time by more experienced by me members that in real life it will not be a problem. And as i told you before, rarely you will reach similar speeds.


    Some comments:

    At my second build i was again at the point of making the same mistake as at the first one. Same as what you are doing here. Trying to save on frame bed and machine weight. Now checking prices of T slot track, T slot solid aluminum, T slot aluminum profile, plain aluminum sheet and plastic sheet, i have it quite clear: The bed must be as strong as possible, crossing profiles as near as possible even bed made of welded profiles as the gantry is made, if you will do mainly aluminum.

    Why that? Cause all else for serious fixing is darn expensive. Now i am hitting my head these days why i did not weld solid profile 1/2 of the bed for the 2600x1300 i am building for my self now.

    So my recommendation here is to make the near to you half of the bed very strong as possible. So later you will not need to pay ridiculous amount of money for aluminum sheets and so.

    What i am saying is you weld a strong structure for bed with the chosen profile. Then go to somebody who has shop, like a welder or machine shop. Ask them for their scrap and rests of different profiles. And that cheap stuff you use to weld in between to make it solid. It could be thin walled.
    Last edited by Boyan Silyavski; 08-03-2015 at 06:44 AM.
    project 1 , 2, Dust Shoe ...

  6. The Following User Says Thank You to Boyan Silyavski For This Useful Post:


  7. #5
    Thanks Silyavski!

    I will go with HTD belts then.

    Ballscrew standard machining leaves 15mm space for the pulley. Standard pulley is about 26mm. How do you solve this?

    I think Silyavskis steel Z axis is coolest one I have seen :) I have studied that design but dont feel certain that I can pull it off. As I have good access to 20-25mm aluminium flatbars I go with the "usual" aluminium Z axis design.
    Btw what is the weight of you steel Z axis, Silyavski?

    I will beef up the frame and will rethink the bed fixing system.

    I need to order rails and screws before EURO is totally useless :(

  8. #6
    Quote Originally Posted by toomast View Post
    Thanks Silyavski!

    I will go with HTD belts then.

    Ballscrew standard machining leaves 15mm space for the pulley. Standard pulley is about 26mm. How do you solve this?

    I think Silyavskis steel Z axis is coolest one I have seen :) I have studied that design but dont feel certain that I can pull it off. As I have good access to 20-25mm aluminium flatbars I go with the "usual" aluminium Z axis design.
    Btw what is the weight of you steel Z axis, Silyavski?

    I will beef up the frame and will rethink the bed fixing system.

    I need to order rails and screws before EURO is totally useless :(
    If you ask for the machining (F dimension I think but a few years since I ordered mine) for the pulley to be 30mm then you'll have plenty of room...

    Neil...

    Build log...here

  9. #7
    Quote Originally Posted by toomast View Post
    Do you think this long 1610 ballscrew will start whipping on X-axis?
    I know silyavski told you No but he's Wrong it most definatley could whip at that length at higher rapid feeds. 20mm is much better screw to use at this length and won't cost much more in either Money or performance.

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  11. #8
    Quote Originally Posted by JAZZCNC View Post
    I know silyavski told you No but he's Wrong it most definatley could whip at that length at higher rapid feeds. 20mm is much better screw to use at this length and won't cost much more in either Money or performance.
    Sorry, totally missed that 1500mm. I was thinking about something else. I will have to whip myself
    project 1 , 2, Dust Shoe ...

  12. #9
    Quote Originally Posted by silyavski View Post
    Sorry, totally missed that 1500mm. I was thinking about something else. I will have to whip myself
    Argh thought it was strange you saying was fine.. . Lol and Don't Whip your self get a nice fit blonde to do it much more fun..

  13. #10
    I agree Dean. I was deep into reading about HF plasma grounding and just glanced at it and thought 1500 total length of screw -300mm in gantry legs gives 1200, minus more when he betters the design, so he could go away with that, cause anyways most people don't go faster than 10m/min in real life. And it was 1500mm travel , not screw length. I hope he did not order the screws. Anyways i will buy them from him if that mistake happened. its never a bad thing to have some extra ball screws.
    project 1 , 2, Dust Shoe ...

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