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Moag's CNC Mill

Discussion in 'CNC Mills/Routers' started by Moag, May 9, 2016.

  1. Moag

    Moag Veteran
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    Design@2 v27-03.png
     
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  2. Joe Santarsiero

    Joe Santarsiero OB addict
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    Ahh. I see it. Cool.
     
  3. Joe Santarsiero

    Joe Santarsiero OB addict
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    The location in this pic looks good from a part and programming stand point. That being that you'll be working in the first quadrant. It's not a hard rule though. More a good habit. That said, a lot of CAM programs will allow you to choose where part 0,0,0 is located and generate the code from there.
    From an operational standpoint, you can place your machine home anywhere you like and give it multiple homes(as long as your electronics and control software aren't somehow limiting factors).
    Another secondary machine home to consider is the back left. Use it at the end of a program to have the worktable move towards you for retrieving the part.

    Nice build. Post some vids when done.

    Joe
     
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  4. David the swarfer

    David the swarfer OpenBuilds Team
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    I added an option to SketchUcam for exactly this, to move the tool away from part 0,0 so you can retrieve the parts.
     
  5. John Mueller

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    Back to the t-nut issue, just push them into place with a flexible rod and micro magnet epoxied to the end of it. After doing a few like that it is easy enough to work with.

    Otherwise I want one in red or blue! With the extrusion in silver. ;)
     
  6. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Seriously, the t-nuts are really not that big of a deal. Get them in alignment, slap a strip of blue tape over them to hold them in position and then peel it as you slide the connection together.
     
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  7. TerryOx

    TerryOx Well-Known
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    What are your thoughts about using a single high-torque, 345oz/inch NEMA-23, with the two outriggers for stability? NEMA 23 Stepper Motor - High Torque Series

    Isn't that better than two 175 oz-in NEMA 23 motors on the same axis?
     
    #67 TerryOx, May 18, 2016
    Last edited: May 18, 2016
  8. Joe Santarsiero

    Joe Santarsiero OB addict
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    Depends on motor characteristics and drivers. You may want to hunt down the torque curves for each motor and run through the math to see if one is more preferable over the other for a given cutting feedrate.
    It's possible that the 175s might be fast and zippy with a long curve, but they may not have the right kick at cutting speed or stall easily. The 345 may not have a high rpm, but have the torque where it's needed. Its curve could drop off so steeply that at high rapid fees rates steps get lost easily. These are just hypothetical.
    In the end it's tough to say. You could have 5 different 175 motors that all act differently. It depends on how they're built and the equipment running them. Good quality drivers can mean the difference between having a motor perform like garbage or gold. If you don't go far into specing the motors then at least invest in some decent electronics to help reduce the chance of having a motor package that doesn't run great.

    Joe
     
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  9. John T Miller

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    OK, complete newbie here, but ... if the perplex sides were aluminum instead, and mounted to the outside, couldn't you reduce the total number of parts and increase the rigidity of the overall assembly?
     
  10. Moag

    Moag Veteran
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    Yes, John it could if not counting how they are mounted and it would also increase the rigidity of the frame in that plane. The main design consideration for using Acrylic sheet (a cheap alternative to polycarbonate) is that you can see what is going on from the side and it is also a fairly rigid material until you hold a hot air gun to it.
     
  11. Javier Canedo

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    Hi Moag, great job. Its just the idea I had (but better developed).

    I was planning to buy the basic parts for a 1000mm x 500mm machine and create reinforcement plates, etc. with it.

    Is your Part list updated? Do you have cad files of the reinforcement plates?

    Javi
     
    #71 Javier Canedo, May 31, 2016
    Last edited: May 31, 2016
  12. Moag

    Moag Veteran
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    Stay tuned Javi,

    There is a bundle deal in the pipeline based on this design, which I'm working on at the moment ;)
     
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  13. chuangatronic

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    I just want to give a word of warning about the z-axis in that configuration. I've been getting a lot of chatter on aluminum when the z-axis is extended to maximum length. I've had no problems on anything softer though. So even though the frame is rigid and the x and y configurations are bulletproof, the z-axis is seems to be the weak link due to the c-beam's deflection behavior at maximum length. Those stiffening channels seem like a good way to help mitigate this problem though, I look forward to seeing the performance of this machine when all is said and done!

    The big caveat is that my x-z gantry only uses wheels at the corners and doesn't have a wrap around ox-style for the x-axis. It may be that my lack of wheels could be compromising the stability of my gantry. Because of that, I switched back to a c-beam machine like configuration with the z-axis bolted straight to the x-axis carriage and a lower gantry height from the table.

    My current cut profile for 6061 T6 hardened is as follows:

    RPM: roughly 16000 (but not fixed due to using bosch colt, no clue how accurate the rpm range actually is since I'm not using a VFD with closed loop control)
    SFM: roughly 500, but it's at the mercy of the colt.
    IPT: for my tools it's recommend to run at 0.0381 mm, I definitely don't run at that since my feed rate is significantly lower.
    MMPM:
    • Rough: 700mm/m, but risk of chattering moderate. I set the stock to leave at .5 mm because of that. I would run it at the calculated 1200mm/m, but the z axis vibration just kills tolerances and makes it hard to estimate stock to leave since the vibration isn't constant. This may have to deal with levelness of my table, I didn't run a surfacing operation to true it up since I all I own is 1/8" tools.
    • Finishing: 380mm/m leaves a pretty nice finish, sandblast and powdercoat effectively cover any flaw. The chips off this feed are still acceptable, haven't had a double cut or chip fusing problem yet.
    Depth of cut: between .2 to .5mm because I'm a chicken, lol. I tend to go with the middle at .35mm
    Tolerance: .41mm or roughly 16 mils total runout

    Hope this helps with anyone trying to work on improved builds.
     
  14. Moag

    Moag Veteran
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    Thanks for the heads up @chuangatronic and for sharing your "feeds and speeds" mate.

    Not actually seeing your machine all I can suggest for your chatter problem cutting aluminium is to bring your workpiece up higher with a extra thick spoil board to reduce the length your Z-axis extends if this concerns you and or using a shorter milling bit may help. May I ask what you are using to move your gantries (belts, lead screws) as what I gather chatter is often a result of backlash among other things such as squareness and rigidity of frame, rigidity of mounted work piece, runout of spindle, number of flutes and design of milling bit, climb cutting for example it's complex. It may just be a resonation feedback in your machine, so increasing your feed a tad might take you into a sweet spot for cutting aluminium, slowing it down a little might do the same but risk,rubbing and not cutting. Caveat I'm no expert, but there are some here that may be willing to help if they have all the information at hand;).

    Always looking for better ways of designing stuff so please let me know of any suggestions on how to improve this design.
    Here's a quick render of how I'm planing to set up the ZX gantry, note double Acme nut blocks to adjust out backlash. X axis C-Beam removed because I'm a lazy renderer with lots of others that I need to complete.

    ZX Gantry Assembly v1.png
     
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  15. chuangatronic

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    @Moag I'm using all lead screws with anti-backlash nuts. You've nailed it with saying to use a thick spoiler board, I've been doing that for all my cuts recently haha.
     
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  16. Moag

    Moag Veteran
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    Yep, best practice if not needing a large depth of cut;) hey.
     
  17. David the swarfer

    David the swarfer OpenBuilds Team
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    in the OX build videos Mark mentions keeping Z short and using thick spoilers to keep the work close to the gantry to increase stiffness.
    short things are always stiffer (-:
     
  18. shelbylewis

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    Any info regarding a bundle for this?... I love the design of this machine. Approaching my first build, and this would be perfect for my purposes. Thanks for sharing!
     
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  19. Mark Carew

    Mark Carew OpenBuilds Team
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    @shelbylewis We are working one up. We just want to be sure it meets all the needs and still has room for modification while keeping cost down. So look for a new post coming soon with the C-Beam Machine XLarge version as a Build bundle!
     
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  20. Javier Canedo

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    Great!!! Please, hurry up!!! :ROFL:
     
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  21. Moag

    Moag Veteran
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    "Patience Grasshopper"
     
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  22. shelbylewis

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    Sounds great. I look forward to it!
     
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  23. Mark Carew

    Mark Carew OpenBuilds Team
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    Just a quick update guys, we are getting a beta Build together now for a clean Build and once that is complete we should be good to go on the C-Beam Machine XLarge! :thumbsup:
     
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  24. Bad Sequel

    Bad Sequel Well-Known
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    *drumroll*
     
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  25. David the swarfer

    David the swarfer OpenBuilds Team
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    I'll beta that (-:
     
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  26. GrayUK

    GrayUK Openbuilds Team Elder
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    Great news. :thumbsup::thumbsup::thumbsup::thumbsup::thumbsup::thumbsup::thumbsup::thumbsup::thumbsup:
     
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  27. gwandad

    gwandad Well-Known
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    Prolonged Drum roll!
     
  28. Moag

    Moag Veteran
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    Prolonged Drum roll kind of like those buildup storms at the end of the long dry; you know it's on its way, you just don't know when going to fall, but you know it's going to rain in the future for sure. ;)

    Apologies for the waiting folks.
     
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  29. gwandad

    gwandad Well-Known
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    You could launch a Saturn V off [email protected]
     
  30. Moag

    Moag Veteran
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    Ah, but could you land one back on it... Now that's the biggy @gwandad o_O

    Cheers Mate.:D
     

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