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  1. #1
    Hi all,

    I figured it was about time I started a proper build log since starting a thread in the new members section. Before I get into the details, a little background of myself. By day I am an Electronics Engineer and by night I am a keen hobbyist! I have built many projects, re-built a couple of motorbikes and fix my car on a regular basis (its french ;) ) but building a CNC router is something I've wanted to do for ages. Now I have some spare time (girlfriend depending!) and a little spare cash (girlfriend depending ;) ) I feel I can finally go ahead with one.

    So here goes...I guess the first question to ask myself is what I want the machine to cut. To that I answer: Wood (MDF), Plastics (Acrylic, Delrin etc) but also Aluminium (basic plates/small parts).

    I have kicked off a design in solidworks and have a VERY basic outline (not done any detail yet) of what I am looking to achieve:

    Click image for larger version. 

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    Along the way I have already made some decisions on parts, as follows:


    • 20mm Hiwin Rail/Carriages all round.
    • RM1605 Ballscrews.
    • FF/FK12 Ballscrew End Supports.
    • 80x80 Profile 8 Extrusion for the Y axis supports.
    • Chinese 2.2kW Spindle
    • Nema 23 Motors.
    • THK KR33A Z axis (Purchased this cheaply off ebay)
    • Approximately an A3 build dimension.


    Like everyone, I have a TON of questions to follow but will post those up separately when I get time to compile them all.

    As always, I'm open to opinions/criticism! It may well be that the whole design changes before I start ordering parts.

    Best Regards,

    Dave

  2. #2
    Hi Dave,

    On the basis that it is broadly similar to my machine, but with slightly better components and smaller footprint (and assuming that the sides are 15-20mm aluminium plate?), I would expect this to perform very well for MDF and plastics. Aluminium would be best cut in the middle of the bed since you only have a central ballscrew (like my machine). Even so this would not suit regular aluminium cutting.

    Adding a plate across the back of the gantry, between the 2 cross members, would be a useful addition.

    I know it is only A3 size, but if you ever think you would upgrade to twin ballscrew in the future then you could increase the width of the end plates and add ballscrew mounting holes so it is ready to go. You would also need more holes in the gantry sides to mount the ballscrew.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  3. #3
    Thanks for the feedback. Twin Y axis (I assume you mean Y?) ballscrews was on my list, I will probably add the mounting holes in so I can add them in the future. All plate will be 20mm thick I think.

    Been doing some more work...

    Click image for larger version. 

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    At the moment I only have 2x Hiwin carriages on the X axis. Would there be much benefit/need to double up on these? I.e. two carriages per rail? If so then I will need to increase the X axis length to get a decent travel. I am leading towards this anyway...

    Dave

  4. #4
    Quote Originally Posted by biketrialsdave View Post
    Would there be much benefit/need to double up on these? I.e. two carriages per rail?
    Definately. The rigidity will be greatly reduced if you don't use two, since with only one on each rail the axis can more easily pivot (or 'rack') about the center point, i.e. the ballnut, which on the gantry will cause the cutter to deflect substantially.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  5. #5
    Will add some more carriages in tomorrow :) thanks!

  6. #6
    I believe routercnc meant twin X-axis ball screws rather than Y (where Y is the gantry). On a small design like this you'd still be able to use a single motor to drive both X-axis screws if you go down that route.

  7. #7
    As in the following?

    Click image for larger version. 

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  8. #8
    No the other way round lol, from what I understand there is no standard but on this forum they refer to the X axis as the back & forward axis, (longest axis on you build) & the Y axis as the left & right movement. Z is as you have it up & down.
    Reason for the twin ballscrews is to prevent the gantry from twisting as it moves backwards & forwards.
    Last edited by martin54; 04-01-2013 at 08:35 PM.

  9. #9
    Normally the longest and lowest down axis is called X and the gantry Y with the Z going up and down like this:
    Click image for larger version. 

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    I've seen one or two designs where the gantry is wider than the bed is long and in that situation it's a little less clear which is X and Y. I believe our American cousins also refer to Y as X.

  10. #10
    JAZZCNC's Avatar
    Lives in wakefield, United Kingdom. Last Activity: 22 Hours Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 5-6 years. Has a total post count of 5,859. Received thanks 910 times, giving thanks to others 37 times.
    Quote Originally Posted by martin54 View Post
    No the other way round lol, from what I understand there is no standard but on this forum they refer to the X axis as the back & forward axis, (longest axis on you build) & the Y axis as the left & right movement. Z is as you have it up & down.
    Reason for the twin ballscrews is to prevent the gantry from twisting as it moves backwards & forwards.
    Depends if you view machine from front or side. Really your just using the Cartesian coordinate system which is X Axis horizontal or left/right and Y Vertical or Forward/backwards.

    If you stand in front of machine like milling machines user's do then the moving table is X axis and it goes Left/right and Y axis goes away and towards you.

    Router users often load and stand at the side of machine which is often the longest Axis. So setup machine to work from the side and match the coordinate system of left/right is the X axis and again the y axis goes away and towards you along the gantry.

    When I first put my machine vertical the hardest part or strangest part was getting my head around the fact it was still setup to be used and viewed from side and know I was stood in front of it. Kept thinking the code was wrong because I was expecting it to move L & R for X when it went UP/down instead.?? Very confusing.!! For it all to make sense all I had to do was tip my head to the side and things looked right.!

    To match the CAD/CAM coordinate system and still look right in Mach I should set it up so that the X axis runs along the gantry left/right and the Y axis vertical Up/down.
    I haven't done it yet but I should really has it's a simple has swapping the motor inputs so X axis uses the Y axis input and vise versa.

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