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  1. #61
    I had planned on using one ballstrew for each axis... waht you see would have 100mm legs on each corner and would then have a piece connecting each side of the gantry that can be bolted onto the gantry sides to make assembly that bit easier
    Click image for larger version. 

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  2. #62
    You are weakening the machine having that base like that and it's completely not needed. You need to keep the gantry sides height to a minimum and your creating 60mm more than needed and every bit helps if your wanting to cut aluminium.
    If you want the best strength then having raised sides with rails on top with gantry sat directly on bearings is massively strong and much much more suited to an all round machine. If your wanting to cut aluminium then you WILL need 2 ballscrews on the axis moving gantry. This is not just an opinion it's hard learnt and tested thru building many differant machine designs trying to find the best design for an all round machine without being silly about design.

    The machine your building with single screws will be fine for mostly wood use and occasional light duty Aluminium work but have no doubts it won't handle cutting aluminium correctly and give quality finish. At a minimum you'll need 2 ballscrews moving gantry to stand any chance and very beefy gantry.

    Edit: Oh and the bed base needs far more supports than just one in middle.
    Last edited by JAZZCNC; 05-06-2014 at 11:49 AM.

  3. #63
    So loose the second level of boxsection with the board ontop?

    Keep gantry height to a minimum

    Design in two ballscrews now rather than later

    add more support for bed..

    got it :) The general gantry design.. Is that ok? with a vertical piece and a 45 member to give some strength... How far should i keep the bearing carriages apart? from the faces that would touch..

  4. #64
    Quote Originally Posted by FlyHighRC View Post
    So loose the second level of boxsection with the board ontop?

    Keep gantry height to a minimum

    Design in two ballscrews now rather than later

    add more support for bed..

    got it :) The general gantry design.. Is that ok? with a vertical piece and a 45 member to give some strength... How far should i keep the bearing carriages apart? from the faces that would touch..
    IF you've gone through the build logs then you'll see a pattern in the design of the routers built recently which are 90% (this one isn't...http://www.mycncuk.com/forums/gantry...ercnc_mk3.html) all raised rails above the bed like the pictures I posted previously. They'll also answer most of the questions you're asking about designing them. You don't have to go re-inventing the wheel! Most people on here want to cut the same things that you do (I do as I want to make parts for balsa and ply planes, carbon fibre heli frames and quad frames, ali parts for my helis and quad etc...) so their routers have been designed as a best compromise to achieve this. Re-read all the build threads to see how designs have changed along the build. Mine's a very good example of just this. I started with a similar design as the one you're doing and has evolved as I've read more build logs and asked questions...
    Neil...

    Build log...here

  5. #65
    The 'routercnc_MK3' is my machine and I'll explain why it looks like that.

    It was much easier to build it like that based on a simple evolution of the previous version. It is only intended to cut balsa wood, liteply, and plywood and it works very well. I've been using it recently for cutting some 20mm thick aluminium upgrade parts, but that is not the main use.

    If I do cut aluminium on my machine (6mm carbide 2 flute cutter) I can run at 1.0mm depth of cut and about 800mm/min feed. Any deeper and I get chatter.

    If you want to cut a fair amount of aluminium the raised X axis designs are far superior and probably the best DIY CNC arrangement without simply converting a bridgeport mill to CNC. If you are starting from scratch there is no reason not to really.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  6. #66
    Quote Originally Posted by njhussey View Post
    IF you've gone through the build logs then you'll see a pattern in the design of the routers built recently which are 90% (this one isn't...http://www.mycncuk.com/forums/gantry...ercnc_mk3.html) all raised rails above the bed like the pictures I posted previously. They'll also answer most of the questions you're asking about designing them. You don't have to go re-inventing the wheel! Most people on here want to cut the same things that you do (I do as I want to make parts for balsa and ply planes, carbon fibre heli frames and quad frames, ali parts for my helis and quad etc...) so their routers have been designed as a best compromise to achieve this. Re-read all the build threads to see how designs have changed along the build. Mine's a very good example of just this. I started with a similar design as the one you're doing and has evolved as I've read more build logs and asked questions...

    Not trying to reinvent any wheel, I have lowered the bed...I am still going to keep the sides now as they are good for more strength and will also save me using 3mm poly as a way to stop rubbish going onto the rails...Im quite happy with this though it may need more support on the underneath... I need to make bracket on either end and either side of the machine to hold the motors and ballscrews...

    My one concern is the accuracy in welding...if i take the parts to a welding shop will they know how precise this had to be? Dont want them to weld it up and realise its off by a few mm

    Click image for larger version. 

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  7. #67
    Quote Originally Posted by FlyHighRC View Post
    My one concern is the accuracy in welding...if i take the parts to a welding shop will they know how precise this had to be? Dont want them to weld it up and realise its off by a few mm
    Don't waste your money because they won't be able to stop distortion only lessen it and in any case you will still need to either use shims or Epoxy method.
    Only thing you want to pay special attention to is Twist. If the base frame is twisted then the rails are not on the same plane, Epoxy method is good for sorting this but if you pay carefull attention when welding up then it's possible to get away with just light shimming of the rails. . . BUT with your design the Epoxy method will be much easier and more accurate than your capabiltys to measure rails are on same plane.!

    Squareness of base frame isn't critical either square to 1 or 2mm is fine, obviously less is preferable. The important area is the gantry is square to the rails.
    The base the cutting bed sits on needs to be resonably flat but again it's not critical as you'll surface the bed before using and this will bring it flat parallel plane.

    Like Neil says you really need to go reading some of the build threads more closely and pick up the tips and you'll see whats needed and where your design Lacks or CAN be improved.
    Last edited by JAZZCNC; 05-06-2014 at 07:13 PM.

  8. #68
    I have spent allot of time on the build logs so far. Im seeing allot of parts that require a mill and to me that dsrives up cost and complexity. Im sure it increases strength but above my computer I have K.I.S.S which is proving handy :D

    A couple questions where I cant seem to find the answer..

    When the epoxy is applied to the steel and sets, to bolt on the rail im assuming you just drill and tap? otherwise that must be a very fiddly job getting all them nuts down there haha

    carriage space seperation, Is there an optimum distance between the bearings? im assuming the further apart the better but that obviously reduces work area so i guess there is a happy medium somewhere, right?

  9. #69
    Quote Originally Posted by FlyHighRC View Post
    I have spent allot of time on the build logs so far. Im seeing allot of parts that require a mill and to me that dsrives up cost and complexity. Im sure it increases strength but above my computer I have K.I.S.S which is proving handy :D
    If you made the gantry out of steel or Ali extrusion you wouldn't need a mill.

    A couple questions where I cant seem to find the answer..

    When the epoxy is applied to the steel and sets, to bolt on the rail im assuming you just drill and tap? otherwise that must be a very fiddly job getting all them nuts down there haha
    Depends on the thickness of the steel. If you've read Eddys build log you'll see he glued in 6mm flat and drilled and tapped into that...

    carriage space seperation, Is there an optimum distance between the bearings? im assuming the further apart the better but that obviously reduces work area so i guess there is a happy medium somewhere, right?
    Pass...i settled on 200mm as a good compromise between losing cutting area and strength...



    Sent from my Galaxy S5
    Neil...

    Build log...here

  10. #70
    Thanks, I prefer the epoxy method thatn gluing some flat bar onto the frame... Purely because it sounds simpler :) Thanks on that! I was thinking nuts inside the box section would be very tedious...any special taps Id need for steel? I have a set of taps but arent made for steel...

    In terms of what i said about a Mill, I was talking more along the lines of motor mounts, Even saw one guy with a very nice machine who had his whole gantry cut by laser...



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