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Too many options! Would someone mind giving me a bit of help?

Discussion in 'CNC Mills/Routers' started by McFuddlebutt, Oct 10, 2017.

  1. McFuddlebutt

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    Let me preface by apologizing since this has been discussed several billion times on the forum. Unfortunately none of the threads I was able to find were able to give me definitive answers.

    I've got $2,000 to spend on a build. I'm a Luthier by trade which makes choosing a machine a bit more difficult. While I don't plan to use a CNC on my expensive instruments, I'd like to be able to make some easier to build models for less experienced players. Plus, the inlay options are exciting to think about.

    Anywho. My needs are

    • Needs a 5"-7" cutting depth (5" will be fine)
    • I would like it to be as close to 24" x 36" as possible (roughly 600x900)
    • It would have to have the ability to cut aluminum, this is actually my main reason to buy one of these, right now, I melt down and mill my own steel to have a bolt on neck plate that is hand hammered then stamped with my signature. I'd like to be able to cut some really beefy aluminum ones for cheaper instruments so I'd like for the aluminum option to be at least 2" if possible. I assume the cut speed is going to be significantly reduced for a 2" depth of cut but I'm cool with that.
    • I would REALLY love to have a ready to order build, I don't know if it's possible to share a shopping cart but I have a habit of ordering a ton of parts and inevitably ordering the wrong one :)
    Any help is GREATLY appreciated! I'm really impressed with how awesome this forum is as a resource for folks like me looking to build a CNC without dropping 50k.
     
  2. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder

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    seems to me you should start with a OpenBuilds C-Beam Machine XLarge

    and to correct you gently "I assume the cut speed is going to be significantly reduced for a 2" depth of cut but I'm cool with that."
    no, cut speed does not reduce, just cut depth per pass. so total time will increase, but 'feeds and speeds' stay the same for the material.
    • the material and tool type (carbide/HSS/high carbon steel) determines the speed at which the cutting tool moves through the cut, the SFM, surface feet per minute.
    • The number of flutes on the tool, and tool diameter, determines the RPM, calculated from SFM and D.
      • RPM: revolutions per minute/rotational speed: (3.82 x SFM)/D or SFM/(.262 x D)
    • The depth of cut per tooth, generally 1 to 5 thou, but specific tools differ), determines the feed speed IPM
      • IPT: inches per tooth/feed per tooth
      • IPM: inches per minute/machine feed rate: T x IPT x RPM (T = # of teeth)
    • and the axial depth of cut is determined by the power of the spindle and the stiffness of the machine.
    what can you expect from a C-beam? about 0.5mm depth per pass though HSM techniques in the Gcode generation might increase that.
     
    MaryD likes this.
  3. McFuddlebutt

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    Thank you for the reply!

    My apologies, I meant the total time to make a cut, not the spindle speed :) The main problem with that particular build is it only offers 1" depth of cut.
     
    #3 McFuddlebutt, Oct 10, 2017
    Last edited: Oct 10, 2017
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Turn the Z axis gantry around and it'll do 2".

    Not sure though how well it'll do 2" in aluminum though. You may have problems with chip removal and and bit flexure.
     
  5. McFuddlebutt

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    But would any configuration be able to offer me a 5" depth of cut on wood?
     
  6. McFuddlebutt

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    Side question, is it possible to increase the distance of the table to the bit on the C-Beam machine by possibly adding more height to the supports on the side? Can you increase the depth of the Z-travel by simply buying a longer ballscrew and extrusion?
     
  7. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Currently discussing that in another thread.
     
    David the swarfer likes this.

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