David A's Benchtop CNC Version 2 - Page 2


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  1. #21
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    Default Re: David A's Benchtop CNC Version 2

    Using the linear rails in this manner is "rigid enough? I would think there would be a serious resonance issue.



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    Default Re: David A's Benchtop CNC Version 2

    4thseal, thank you for the question.

    Functionally, I would say the arrangement of these linear shafts is in line with their intended purpose.
    They slide in two ball bushings in a linear direction with axial and radial loads applied along the linear shaft.

    In this case, instead of being typically on the Y or X axis, they are used in the Z direction and instead of the
    bushings moving, the shaft moves.

    Keep in mind that these are two 1.18" diameter hardened steel shafts over a span of about 8" and
    the unsupported portion of the shaft never exceeds the ball bushing spacing at any time.

    I am pretty sure Peter (peteeng) can show some quick calcs how the two 30mm shafts would compare
    to a conventional aluminum extension plate most designs use.

    To get back to your original question, I have not observed any resonance issues whatsoever on the
    prototype machine over the two years I have been testing it on various materials.

    BryggaCNC.com


  3. #23
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    Default Re: David A's Benchtop CNC Version 2

    Quote Originally Posted by davida1234 View Post
    Hello all,

    Some of you might remember, I had posted a thread called "David A's New 2x3 Benchtop CNC" about two years ago.

    https://www.cnczone.com/forums/diy-c...h-top-cnc.html

    The machine has been running good and received quite a bit of changes in those two years so I thought I start a new thread showing the improvements I made since then.
    Good to see you back with more good ideas with your machine build

    Mactec54


  4. #24
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    Default Re: David A's Benchtop CNC Version 2

    Hi David - The proof is in the pudding (prefer lots of chocolate sauce) no need for calcs, if you know it does the job. Keep Making Peter



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    Default Re: David A's Benchtop CNC Version 2

    Hey, good to hear again from you guys.

    On this build, I really concentrated on making all forces
    as much planar or inline as possible.

    I strongly believe that by minimizing any offsets and
    cantilevers you also minimize stress and deflection.

    BryggaCNC.com


  6. #26
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    Default Re: David A's Benchtop CNC Version 2

    The sand ballast is finally dry enough for the top to be placed.
    There is a 1/4" HDPE sheet covering on top of the plywood:

    David A's Benchtop CNC Version 2-base-finished-jpg

    BryggaCNC.com


  7. #27
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    Default Re: David A's Benchtop CNC Version 2

    The machine frame is on the base:

    David A's Benchtop CNC Version 2-machine-base-jpg

    Now the assembly of the machine can start.

    BryggaCNC.com


  8. #28
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    Default Re: David A's Benchtop CNC Version 2

    Machine Assembly:

    Installation of machine feet:

    The four feet consist of 1" diameter SS bolts and nuts
    pressed into plastic bases with 1/4" screw-down holes:

    David A's Benchtop CNC Version 2-feet-1-jpg

    Lift one side of the frame. I use a car jack for that:

    David A's Benchtop CNC Version 2-feet-2-jpg

    Screw in the 1" bolt directly into the bottom of the upright profile:

    David A's Benchtop CNC Version 2-feet-3-jpg

    Do the same on the other uprights.

    BryggaCNC.com


  9. #29
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    Default Re: David A's Benchtop CNC Version 2

    INSTALLATION OF Y/A-AXIS REAR CAPS:

    Parts of rear caps:

    David A's Benchtop CNC Version 2-rear-bumpers-1-jpg

    Puts a bit of glue to the backs of rubber bumpers and push into recesses.
    No screw necessary as they only work on compression.
    I used liquid tape for that but any glue will do:

    David A's Benchtop CNC Version 2-rear-bumpers-2-jpg

    Rear caps ready for assembly:

    David A's Benchtop CNC Version 2-rear-bumpers-3-jpg

    BryggaCNC.com


  10. #30
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    Default Re: David A's Benchtop CNC Version 2

    Using the 5/16 cap screws, install rear caps to the back of Y/A beams:

    David A's Benchtop CNC Version 2-rear-caps-jpg

    Rear caps installed:

    David A's Benchtop CNC Version 2-rear-caps-4-jpg

    David A's Benchtop CNC Version 2-rear-caps-5-jpg

    BryggaCNC.com


  11. #31
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    Default Re: David A's Benchtop CNC Version 2

    INSTALLATION OF Y-A RAILS:

    All rail mounting surfaces have been machined for flatness:

    David A's Benchtop CNC Version 2-y_a-rails-jpg

    Y/A axis uses the shorter 20mm linear rails with flanged trucks.
    All trucks have been re-lubricated with Mobilux EP1 grease:

    David A's Benchtop CNC Version 2-y_a-rails-1-jpg

    Install the self-centering T-nuts with 5mm screws onto the linear rails:

    David A's Benchtop CNC Version 2-y_a-rails-2-jpg

    Make sure the grease nippels are facing outwards.
    Slide the linear rails with the T-nuts into the top groove of the profile:

    David A's Benchtop CNC Version 2-y_a-rails-3-jpg

    Push the rail until it lines up with the front of the rubber bumpers:

    David A's Benchtop CNC Version 2-y_a-rails-5-jpg

    BryggaCNC.com


  12. #32
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    Default Re: David A's Benchtop CNC Version 2

    Y rail and A rail on the frame:

    David A's Benchtop CNC Version 2-y_a-rails-frame-jpg

    Before tightening, wiggle the rails side to side to fully seat the T-nuts:

    David A's Benchtop CNC Version 2-y_a-rails-6-jpg

    Slightly tighten the rails by starting from one end.
    Then go back to start again and fully tighten:

    David A's Benchtop CNC Version 2-y_a-rails-7-jpg

    Once everything is fully tightened, use a piece of plastic and a
    hammer to seat the green covers over the screw heads.

    David A's Benchtop CNC Version 2-rail-covers-jpg

    BryggaCNC.com


  13. #33
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    Default Re: David A's Benchtop CNC Version 2

    INSTALLATION OF Y/A CARRIAGES:

    Y/A carriages:

    David A's Benchtop CNC Version 2-y_a-carriage-1-jpg

    Remove the four dust covers and brushes on the carriages:

    David A's Benchtop CNC Version 2-y_a-carriage-2-jpg

    David A's Benchtop CNC Version 2-y_a-carriage-3-jpg

    Place them on the linear rail trucks, making sure the 5/16 threaded holes
    are towards the front of the machine and the notch faces outward:

    David A's Benchtop CNC Version 2-y_a-carriage-4-jpg

    Tighten the carriages to the trucks with M6 screws in an
    alternating pattern like you do with car wheel nuts:

    David A's Benchtop CNC Version 2-y_a-carriage-5-jpg

    Y/A Carriages on the machine:

    David A's Benchtop CNC Version 2-y_a-carriage-6-jpg

    BryggaCNC.com


  14. #34
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    Default Re: David A's Benchtop CNC Version 2

    The gantry uses the 20mm narrow trucks:

    David A's Benchtop CNC Version 2-gantry-1-jpg

    Place the gantry beam on the carriages.
    Make sure the machined slot is towards the front:

    David A's Benchtop CNC Version 2-gantry-3-arrows-jpg

    David A's Benchtop CNC Version 2-gantry-2-arrows-jpg

    BryggaCNC.com


  15. #35
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    Default Re: David A's Benchtop CNC Version 2

    Install the shorter linear rail like the previous rails:

    David A's Benchtop CNC Version 2-gantry-4-jpg

    Flip over the gantry beam. Linear rail fits between the carriages.

    Install the longer linear rail to the top like the previous rails.

    Upper and lower linear rails installed on the gantry beam:

    David A's Benchtop CNC Version 2-gantry-5-jpg

    BryggaCNC.com


  16. #36
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    Default Re: David A's Benchtop CNC Version 2

    Hi David - How are you squaring the gantry rails to the table rails? Peter



  17. #37
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    Default Re: David A's Benchtop CNC Version 2

    Hey Peter - Final squaring of the gantry will be done after all the mechanicals are installed.

    For rough installation, the top of frame in the back is pretty square to the table.

    David A's Benchtop CNC Version 2-frame-1-arrows-jpg

    Last edited by davida1234; 05-28-2021 at 07:34 PM.
    BryggaCNC.com


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    Default Re: David A's Benchtop CNC Version 2

    Take the two front caps and install two 1/4" screws and T-nuts:

    David A's Benchtop CNC Version 2-gantry-6-jpg

    Temporarily install the end caps to the back bottom slots of
    the gantry beam at both sides as shown:

    David A's Benchtop CNC Version 2-gantry-7-jpg

    Slowly push the carriages and the gantry beam to the back
    until the caps hit the back beam of the frame:

    David A's Benchtop CNC Version 2-gantry-8-jpg

    BryggaCNC.com


  19. #39
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    Default Re: David A's Benchtop CNC Version 2

    Gantry beam will be attached to the carriages using the 4 holes on both sides:

    David A's Benchtop CNC Version 2-gantry-9-jpg

    Align the holes on the carriages with the slots of the gantry beam.

    Make sure the gantry beam is still up against the rear frame
    and slightly clears the carriages on both sides:

    David A's Benchtop CNC Version 2-gantry-10-jpg

    DOING THE INSIDE SCREWS FIRST, use a magnet stick to push the
    T-nuts into the slot and install the 5/16 screws from the bottom:

    David A's Benchtop CNC Version 2-gantry-12-arrows-jpg

    David A's Benchtop CNC Version 2-gantry-11-arrows-jpg

    Once everything is tightened down, remove the end caps
    from the back of the gantry beam.

    BryggaCNC.com


  20. #40
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    Default Re: David A's Benchtop CNC Version 2

    Install a bracket finger-tight on both sides of the gantry beam:

    David A's Benchtop CNC Version 2-gantry-13-jpg

    Install two braces on both sides.
    Make sure the holes are facing down and the short part is up:

    David A's Benchtop CNC Version 2-gantry-14-jpg

    David A's Benchtop CNC Version 2-gantry-14arrows-jpg

    Check for squareness:

    David A's Benchtop CNC Version 2-gantry-15-jpg

    Tighten down everything.
    Gantry beam braces are installed:

    David A's Benchtop CNC Version 2-gantry-16-jpg

    BryggaCNC.com


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