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  1. #1
    Ok, here we go!

    Name's Mart and I come from lovely boring rural Suffolk. Well I come from Down Under before that but its another story altogether...


    I've been lurking around here for a while now, gathering ideas after going thru about 10 different design iterations. So, after gathering some ideas, comparing them with my metal stockpile and aluminium prices online, I've done another one :)

    What I'm trying to achieve is a machine with a quesstimated work area of around 800x600x300. Why these measurements. Well, first of all, I had a look at a workbench I have here and thought "this looks about the right size" :) Then I tried to optimize the measurements with the steel stock I hold in the junk pile. And well, it felt about right :)

    I have hardly any experience with CNC other than just sending DWG-s to suppliers, so its a proof of concept if you like for a bigger machine in the future. And also, hopefully I can actually fabricate the bits needed for the bigger machine then :)

    So. The frame is welded out of 50x3 and 20x2 box section (just because I have too much of it) It's probably a massive overkill (in some ways but weak in others), but well. The massive amount of 20x20 box is just because I have so much of it kickin about. The green bits on the drawing, on top of the frame are 60x6 flatbars, stitch welded to frame to provide something more solid to mount the rails on.

    Gantry is 120x5 aluminium box section. End plates are 15mm ali. Rails are planned SBR16. Ball screws 1610 for X and Y and 1605 for Z.


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    What else. Cheap 3Nm steppers. Haven't decided yet on direct drive or belts. Have no idea about drivers/PSU-s :)
    Somehow I managed haggle myself Thisl from Zapp. Don't even know if it works but I got it free :)

    Spindle. About 2Kw ish, China .


    So, some quick pictures. I swapped computers lately and for some reason I can't open my z axis or drive assemblies. But I'll work on it and hopefully get more decent design up tonight.






    All help would be appreciated, as I feel kind of stubid about these machines :)

    Regards,
    Mart

  2. Hi - Which part of Suffolk are you in?...i'm just over the border in Norfolk.

    Whilst i'm still in the process of designing my steel/aluminium build & am not as wise as many of the others round here, there are a couple of things that stand out to me.
    I think you'll want to replace the middle side legs with 50mm box rather than the 20mm box.
    The gantry looks to be uber chunky - the distance between the front of the gantry, the Y leadscrew & then the front Y plate all look far too big. It's also better to keep the Y leadscrew either behind the gantry or inside it to help keep gunk/chips away from it.

    Good first draft though - much better than mine was

  3. #3
    Im near Stowmarket.

    About the sides and rear end. I plan to fill the sides/rear in with some MDF to control dust a bit better and I actually hope it'll make it a good bit stronger from there as well. With all the triangulation and say ~15mm MDF it should be pretty strong. Bear in mind that the straight legs are only 250mm long.


    As for the gantry and Z carrier, the gap should be 42mm. Thats 43mm high ball nut carrier sunken into the plate 3mm and 2mm for good old air. I have to check the drawing. There might be a horrible mistake there somewhere.

    I'm not really fond of the idea of cutting a 120mm box section apart to fit the lead screw in there... and then starting to strengthen it :)
    As I have understood it would be best to keep the lead screw as close to the Z as possible to minimize leverage?

    I might mount some little brushes on the ball screw to keep it clean when this comes an issue. Someone has done it on my Bridgeport and seems to work pretty good.

    Edit: oh, about the base and those 20mm box sections there. Base is going to be covered with 20mm ali plate. Should be plenty strong then?
    Last edited by mart154; 28-08-2013 at 05:11 PM.

  4. #4
    That looks to me that it will be difficult to load the media, especially if full size and heavy. G.

  5. #5
    Quote Originally Posted by GEOFFREY View Post
    That looks to me that it will be difficult to load the media, especially if full size and heavy. G.
    The work envelope is pretty small, so I can't see doing any heavy lifting :)
    Front diagonals should be designed just so a "full size" 600mm wide sheet fits in between them.

    Basically, the heaviest "full size" I can see myself working on, would be maybe a 25mm-ish aluminium plate. 800x600mm of that weighs in just over 32kg, so wouldn't be much of a problem to wiggle in even if the front diagonals would be in the way...

  6. #6
    Quote Originally Posted by mart154 View Post
    The work envelope is pretty small, so I can't see doing any heavy lifting :)
    Front diagonals should be designed just so a "full size" 600mm wide sheet fits in between them.

    Basically, the heaviest "full size" I can see myself working on, would be maybe a 25mm-ish aluminium plate. 800x600mm of that weighs in just over 32kg, so wouldn't be much of a problem to wiggle in even if the front diagonals would be in the way...
    If you have so many steel, why don't you move the supporting braces outside or think of something else.

    Correct me if i am wrong, but when you design a thing from scratch there shouldn't be any compromises. Thats the whole point, yes?

  7. #7
    You are correct. There shouldn't be any compromises and I can't see the front supports being an issue with the work I plan to do.

    I will have a crack designing outside supports but it seems to complicate frame I planned to bolt the machine on to have it higher.

  8. #8
    Been busy with other things recently and finally decided to have another crack on the design.

    The work area has increased a bit and gone a bit beefier.

    The work area is now 890x1000
    The cutting area should be about 670x780 now.

    Main frame is now 50x50x3 box. The rails bolt on to 60x60x5 (blue)
    The green bits are 30x30x2 box to support the baseplate.
    The gantry is still 120x120x5 ali box.

    So any feedback is greatly appreciated before I start cutting the steel :)

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  9. #9
    Looks ok to me but I'd change the way the bed is constructed to help keep side frames from being pushed while welding and cut down on steel.

    You won't need mesh that tight so I'd drop 2 of the long rails and flip other around and take rail across machine from each side in centre, this will hold sides together better and lessen chance of welds pushing/bending side rails. I'd then run the others up the machine and space outer ones so they land on the edge of the planned cutting area, they will support whole cutting area better. You will probably have a lower bed that goes right up to the sides but you'll also have a spoil board that is the size of your cutting area so ideally you want the edges of this to land on the supports and not rely on the bed underneath which isn't supported.
    This also means you could drop the green bits because the bed will be supported where it matters, in the cutting area, and the small overhang which is a cantilever won't matter has it has no forces acting on it.

    Other than that then fire up the saw. .
    Last edited by JAZZCNC; 16-09-2013 at 10:23 PM.

  10. #10
    Oh forgot to spot this but was more looking at the frame than the gantry.! . . . . Mentioned this before many times .!! Wouldn't have the Y axis like that with a rear piece so basicly creating a box with no sides. It's just adding weight and costing money it gives very little strength. Get your self a card box and cut sides out and see what it does.?? . . .Same principle.

    It also adds other complications in the build because if the edges are not machined perfectly 90deg it skews the box making it parallelogram which will cause bearings to bind and stick when bolted together.
    Last edited by JAZZCNC; 16-09-2013 at 10:35 PM.

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