Benchtop Monster is Born - Harbor freight 44991 / 33686 Hybrid CNC Conversion!!! - Page 5


Page 5 of 8 FirstFirst ... 2345678 LastLast
Results 81 to 100 of 148

Thread: Benchtop Monster is Born - Harbor freight 44991 / 33686 Hybrid CNC Conversion!!!

  1. #81
    Gold Member BobWarfield's Avatar
    Join Date
    May 2005
    Location
    USA
    Posts
    2502
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by HawkJET View Post
    In the above discussion, the pitch accuracy is what is used to determine the AMOUNT of float that will be necessary. The whole point is several posters were commenting that there was no float, but in actuality, the system isn't nearly stiff enough to prevent the float that is needed - therefore the problem that was theorized is non existent (which is consistent with A.S.' experience).
    There are two reasons for float.

    One is as you and A.S. have said: to deal with irregularities in the ballscrew. I will grant the 125 millionths figure and forget about this issue.

    But the second is to deal with inaccuracies in the bracket that fixes the nuts together. Consider a typical wavy washer from McMaster Carr: 9715k92

    It has a total deflection available of 0.069". That's about 120 degrees of rotation on a 0.2" lead ballscrew, so the couple of degrees of rotation the flex allows is fine. But the accuracy of those fasteners on that aluminum strip is pretty iffy. Are the forcing the ballnuts closer or further apart? Do you have 100lbs of preload, 75, or 50?

    I'm sure there is probably some preload there and things are working relatively well. It's just that's it's extremely easy to make a floating assembly and it makes things a bit more predictable. That's a pretty light mill, so the cutting forces will likely never overcome whatever preload is available.

    To each his own. The mill is working, its a nice simple assembly, rock on!



    Cheers,

    BW



  2. #82
    Registered HawkJET's Avatar
    Join Date
    Mar 2009
    Location
    USA
    Posts
    336
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by BobWarfield View Post
    But the second is to deal with inaccuracies in the bracket that fixes the nuts together.
    You got me on this one Bob. As a master craftsman mold maker, I forget that not everyone has the skill to work to the tolerances I routinely use.

    From your comments, I see there is an implication that one could build their anti-backlash system this way. But if they don't get it just right - it could be trouble.

    Yes Bob, your point is well taken. Using a different system can make the required tolerances much easier to manage.

    "Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away." Antoine de Saint-Exupery (1900 - 1944)


  3. #83
    Registered SScnc's Avatar
    Join Date
    Jun 2008
    Location
    USA
    Posts
    457
    Downloads
    0
    Uploads
    0

    Default

    A.S.,

    How long did shipping take to get this table from China ?

    And I use flood coolant, are there "acordian style" way covers available for this size table that you know of ?



  4. #84
    Member CROSSHATCH's Avatar
    Join Date
    Sep 2006
    Location
    US
    Posts
    1732
    Downloads
    0
    Uploads
    0

    Default

    Keep us updated, Love the work!


    -Jason



  5. #85
    Registered Crevice Reamer's Avatar
    Join Date
    Mar 2008
    Location
    USA
    Posts
    3655
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by SScnc View Post
    A.S.,

    How long did shipping take to get this table from China ?
    Already answered:

    Quote Originally Posted by asammons View Post
    It took about 7 weeks - I ordered parts by calling harbor freight 800 number, they shipped them from factory to warehouse, and delivered on a semi.
    CR.



  6. #86
    Registered
    Join Date
    Jun 2005
    Location
    USA
    Posts
    57
    Downloads
    0
    Uploads
    0

    Default

    The truth is, as was stated earlier, deviations and inaccuracy of these screws is insignificant - rolled screws are smoother then ground screws, and the rolling process by default is repeatable over short distance. The preload is far greater than what the bracket can resist due to lack of stiffness. Can the design be improved? Sure it can... Will it yield a better performance? Not at these loads...

    Keep it simple, stupid (KISS).

    As for springs, I have used two 81lb springs in each assembly (1/16" deflection of full load). McMaster part number 9717K62.







  7. #87
    Member
    Join Date
    Feb 2006
    Location
    USA
    Posts
    7087
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by escott76 View Post
    That's all well and good, but I agree with Pete. Using the mounting holes from the return tube looks like it will constrain the motion of the nuts such that they aren't allowed to float back and forth lengthwise on the screws. If they can't do that, then they might as well be rigidly attached to each other and ditch the springs.
    A detailed picture would be worth a 1000 words here, as it's possible I'm missing something.

    You see, if I LOOKED at the pictures it might be better. I reaffirm what I said, it constrains the system in a way that isn't the best. You want the second nut to float axially while being constrained radially. I used a dowel pin against the side (two actually, but it only technically requires one).
    Here's how I did mine....

    Regards,
    Ray L.

    Attached Thumbnails Attached Thumbnails Benchtop Monster is Born - Harbor freight 44991 / 33686 Hybrid CNC Conversion!!!-p1040521-jpg   Benchtop Monster is Born - Harbor freight 44991 / 33686 Hybrid CNC Conversion!!!-p1040522-jpg   Benchtop Monster is Born - Harbor freight 44991 / 33686 Hybrid CNC Conversion!!!-p1040527-jpg   Benchtop Monster is Born - Harbor freight 44991 / 33686 Hybrid CNC Conversion!!!-p1040528-jpg  



  8. #88
    Registered
    Join Date
    Dec 2008
    Location
    United States
    Posts
    445
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by HimyKabibble View Post
    Here's how I did mine....

    Regards,
    Ray L.
    Nice! Very simple and compact.



  9. #89
    Registered
    Join Date
    Jun 2005
    Location
    USA
    Posts
    57
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by HimyKabibble View Post
    Here's how I did mine....

    Regards,
    Ray L.
    Looks good! How much force are you applying between the two nuts?



  10. #90
    Member
    Join Date
    Feb 2006
    Location
    USA
    Posts
    7087
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by asammons View Post
    Looks good! How much force are you applying between the two nuts?
    I don't recall exactly, but in the neighborhood of 250 pounds. These are 1" screws on my knee mill. This arrangement was trivial to machine, and works very nicely.

    Regards,
    Ray L.



  11. #91
    Gold Member acondit's Avatar
    Join Date
    Apr 2005
    Location
    USA
    Posts
    1778
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by HimyKabibble View Post
    Here's how I did mine....

    Regards,
    Ray L.
    I don't see any Belleville washers or springs for tension. How do you deal with any inaccuracy in your screws?

    Alan



  12. #92
    Member
    Join Date
    Feb 2006
    Location
    USA
    Posts
    7087
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by acondit View Post
    I don't see any Belleville washers or springs for tension. How do you deal with any inaccuracy in your screws?

    Alan
    There's a stack of Bellevilles inside that aluminum sleeve between the two nuts. They're not in the pictures, because I hadn't received them yet when I took the pictures.

    Regards,
    Ray L.



  13. #93
    Registered
    Join Date
    Jul 2007
    Location
    USA
    Posts
    212
    Downloads
    0
    Uploads
    0

    Default

    Sammons,

    How did you keep the ballnuts from rotating? Looks like you crossdrilled holes in the coupler....were those for set screws? Wouldn't that be hard on the threads?

    Harbor Freight X3, Keling 387inoz 23's, 640inoz 34, G203V's, Homebuilt 65V PSU, PMDX-122 BOB, NOOK XPR screws, NOOK SBN ballnuts, Shuttle Pro2, Mach3


  14. #94
    Registered SScnc's Avatar
    Join Date
    Jun 2008
    Location
    USA
    Posts
    457
    Downloads
    0
    Uploads
    0

    Default

    I'm going to be ordering this table from HF shortly. I currently have 270 oz-in steppers on my X2, will those still work reliably with this setup considering they are direct drive right now but with this new table there will be some reduction with pulleys ? Or do I really need to go up to more like the 480 oz-in ones like asammons has used ? thanks



  15. #95
    Registered
    Join Date
    Sep 2004
    Location
    US
    Posts
    35
    Downloads
    0
    Uploads
    0

    Default

    I saw on LMS that you can get an X3 head and column. Anyone though of putting an X3 on this table?



  16. #96
    Registered Crevice Reamer's Avatar
    Join Date
    Mar 2008
    Location
    USA
    Posts
    3655
    Downloads
    0
    Uploads
    0

    Default

    Quote Originally Posted by jfseaman View Post
    I saw on LMS that you can get an X3 head and column. Anyone though of putting an X3 on this table?
    With a 20% off coupon you can buy the whole MILL from Harbor freight for $50 more than what LMS wants for just the column/head.

    An X3 or SX3 column should bolt up even easier. If I added my SX3 column with 18 inches of Z to this base/table--Now THAT is a mill!

    Yeah, I'm thinking about it.

    CR.



  17. #97
    Registered
    Join Date
    May 2009
    Location
    Isralel
    Posts
    1
    Downloads
    0
    Uploads
    0

    Default

    Great job on the project - I have a couple of questions:
    So this is basically just an X3 table on an X2 mill right (Not putting down your project, just simplification)?
    For someone who doesn't already have mill to work with (me), would it be better to go this route or just buy an HF X3 for $720 ($899 - 20%)?
    Is there any advantage to the X2/X3 hybrid over a "normal" X3, or did you create this to expand your current mill's capabilities vs buying a new mill?

    Thanks



  18. #98
    Member jalessi's Avatar
    Join Date
    Feb 2007
    Location
    United States
    Posts
    4555
    Downloads
    1
    Uploads
    0

    Post

    Joe,

    Thats not a X3 table, its a Harbor Frieght 33686 round column mill table.

    Its much bigger than a X3.

    Where did you find a X3 listed for $899? Please post a link.

    I have the 20% percent off coupon however the current price for the x3 is $999

    http://www.harborfreight.com/cpi/cta...emnumber=93885

    Jeff...

    Patience and perseverance have a magical effect before which difficulties disappear and obstacles vanish.


  19. #99
    Gold Member LeeWay's Avatar
    Join Date
    Jun 2004
    Location
    United States
    Posts
    6618
    Downloads
    2
    Uploads
    0

    Default

    There are several ways to handle the double nut system. I had plenty of room on my lathe and router builds, so I went with simple compression springs.
    I mill a channel in some aluminum and fixed this fast to the first nut. The second nut can't turn, but can move relative to the first. I think I have about 95 pounds of force on these. I don't see any backlash on my lathe, but do see slight irregularities on the router. Likely due to different types of bearing mounts.


    http://www.cnczone.com/forums/attach...2&d=1230561899

    Lee


  20. #100
    Registered kanton's Avatar
    Join Date
    Jun 2003
    Location
    USA
    Posts
    232
    Downloads
    0
    Uploads
    0

    Default

    Is anyone willing to make up a kit and stock the parts to help a newby do this conversion?



Page 5 of 8 FirstFirst ... 2345678 LastLast

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

Benchtop Monster is Born - Harbor freight 44991 / 33686 Hybrid CNC Conversion!!!

Benchtop Monster is Born - Harbor freight 44991 / 33686 Hybrid CNC Conversion!!!

Benchtop Monster is Born - Harbor freight 44991 / 33686 Hybrid CNC Conversion!!!