Arvid's first CNC machine! - Page 3


Page 3 of 5 FirstFirst 12345 LastLast
Results 41 to 60 of 85

Thread: Arvid's first CNC machine!

  1. #41
    Registered
    Join Date
    Jan 2004
    Location
    United States
    Posts
    490
    Downloads
    0
    Uploads
    0

    Default

    Definately talking about different things! I am going to put a steel frame machine together...eventually, that will use these bushings, then see what they can do! As far as your bushings, why not tap a commercial bushing for the thread?

    Stop talking about it and do it already!!!!!

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  2. #42
    Registered
    Join Date
    Oct 2003
    Location
    Sweden
    Posts
    399
    Downloads
    0
    Uploads
    0

    Default

    It would be interesting to hear your judgement on the Igus slides when you are done!

    I'm not sure what you mean by the "tapping a bushing" comment? The thing is, I want to rigidly attach a timing pulley to my leadscrew journal, for driving the screw. But since the journal is so small (only 10 mm dia) and also smooth, it's difficult to find a pulley that would grip the axle well enough.

    There are pulleys with something called taperlock bushings that would work well, except these have a too big dia for my journal. So now I've found a "loose" taperlock-style bushing that you can place between the hub of the pulley and the axle, that expands and therefore holds the pulley in place on the journal. Only they're a bit expensive

    Arvid



  3. #43
    Registered
    Join Date
    Jan 2004
    Location
    United States
    Posts
    490
    Downloads
    0
    Uploads
    0

    Default

    I thought you meant that you wanted to attatch a bushing to the thread of the rod to enlarge it for a given pulley ID. Sounds like what you need is to have an extended hub on the pulley, with a set screw to tighten against a flat on the lead screw journal. If the ID of the pulley is too big for that, talk to a machine shop about turning up a bushing that will prss fit on the lead screw journal. Shouldn't cost too much. What time is it in Sweden right now?
    Jens

    Stop talking about it and do it already!!!!!

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  4. #44
    Registered
    Join Date
    Oct 2003
    Location
    Sweden
    Posts
    399
    Downloads
    0
    Uploads
    0

    Default

    It's also a question of torque handling capability; peak torque will be somewhere around 5.75 Nm or about 810 oz-in. But I'll keep it in mind as an option!

    When I wrote my previous message, the time was about 11:30 PM here. It's now about 9 in the morning. (GMT+1)

    Arvid



  5. #45
    Registered
    Join Date
    Oct 2003
    Location
    Sweden
    Posts
    399
    Downloads
    0
    Uploads
    0

    Talking

    I found a pair of 280 mm THK HSR25 rails with slides on ebay. I *am* a lucky one! They are perfect for Z guides, especially considering I already bought THK HSR25 for my Y. They are even preloaded!

    (I hope one of the administrators tells me to stop if I post too many pictures...)

    Attached Thumbnails Attached Thumbnails Arvid's first CNC machine!-02210024-z-guides-jpg  


  6. #46
    Registered balsaman's Avatar
    Join Date
    Mar 2003
    Location
    Canada
    Posts
    2139
    Downloads
    0
    Uploads
    0

    Default

    Nice!

    No need to stop posting pictures. Keep going.

    E

    I wish it wouldn't crash.


  7. #47
    Registered
    Join Date
    Oct 2003
    Location
    Sweden
    Posts
    399
    Downloads
    0
    Uploads
    0

    Default

    Thank you balsaman! I will .

    ... and I recently got a Servo Pack (Yaskawa term for servo amplifier) for my motor. I'm having some trouble getting it to work at the moment... the Servo Amplifier thinks the motor encoder is 1024 pulses per rev, while it is, in fact, 2048... and as of now, I have no way to set this. At least I *think* this is the problem...

    The Servo Pack and Servo Motor were bought used, and all the connector cables had been cut right off when they were dismounted from their previous machine. So there were some tricky soldering of micro-DB20 connectors and splicing of cables to get this far.

    In the picture below, you can see one of the connectors (that luckily were delivered with the Servo Pack) lying on the table, and the Servo Pack and Motor connected. The motor has two cables coming out of it, one for the encoder and one for power. The grey one is power (U, V, W phases + Frame Ground), and connects to the cable shoe terminal on the left of the Servo Pack. The black one is the connector cable, connected to the Servo Pack with the micro-DB connector.

    The white cable connected to the Servo Pack is for connecting it to a computer for programming. But I don't have the correct program for this (yet) .

    In the background, wrapped in plastic, are the different linear guides.

    Arvid

    Attached Thumbnails Attached Thumbnails Arvid's first CNC machine!-02210010-overview-jpg  


  8. #48
    Registered
    Join Date
    Oct 2003
    Location
    Sweden
    Posts
    399
    Downloads
    0
    Uploads
    0

    Default

    Closeup of the motor... crudely clamped for testing

    Attached Thumbnails Attached Thumbnails Arvid's first CNC machine!-02210008-motor-jpg  


  9. #49
    Registered
    Join Date
    Oct 2003
    Location
    Sweden
    Posts
    399
    Downloads
    0
    Uploads
    0

    Default

    ... and the Servo Pack

    Attached Thumbnails Attached Thumbnails Arvid's first CNC machine!-02210006-servo-pack-jpg  


  10. #50
    Registered
    Join Date
    Oct 2003
    Location
    Sweden
    Posts
    399
    Downloads
    0
    Uploads
    0

    Default

    And a warning label on the outside of the Servo Pack cable shoe terminal lid.

    There's no transformer in the Servo Pack, the mains is simply rectified and smoothed with two big capacitors.

    This is lethal in two ways: first, there's about 20 uF of >300 VDC waiting to kill you, and secondly, there's no isolation from the mains. So I obey the warning labels, believe me!

    Arvid

    Attached Thumbnails Attached Thumbnails Arvid's first CNC machine!-02210017-warning-label-jpg  


  11. #51
    Member
    Join Date
    Feb 2004
    Location
    Flagstaff,AZ
    Posts
    304
    Downloads
    0
    Uploads
    0

    Default

    Here's another way to attach pulleys on a shaft with at lease one flat. I's better than setscrews or a keyway bacause it won't slip. With no flats I'd go for a taper-lock if you can find one small enough.

    Attached Thumbnails Attached Thumbnails Arvid's first CNC machine!-pulleys-jpg  


  12. #52
    Member
    Join Date
    Feb 2004
    Location
    Flagstaff,AZ
    Posts
    304
    Downloads
    0
    Uploads
    0

    Default

    Sorry I obviously need an automatic spellchecker.



  13. #53
    Registered balsaman's Avatar
    Join Date
    Mar 2003
    Location
    Canada
    Posts
    2139
    Downloads
    0
    Uploads
    0

    Default

    Avrid, do those drives use step and dir signals? You should be able to fool the drives by setting the resolution incorrectly in the software. Two wrongs making a right in this case....?

    E

    I wish it wouldn't crash.


  14. #54
    Registered
    Join Date
    Jul 2003
    Location
    CA,USA
    Posts
    200
    Downloads
    0
    Uploads
    0

    Default

    Kevin,

    That's a good idea!

    How is the vibration? How fast--rpm's-- have you run pulleys modified this way?

    Thank you in advance,

    Ballendo

    Originally posted by kevincnc
    Here's another way to attach pulleys on a shaft with at lease one flat. I's better than setscrews or a keyway bacause it won't slip. With no flats I'd go for a taper-lock if you can find one small enough.




  15. #55
    Registered
    Join Date
    Oct 2003
    Location
    Sweden
    Posts
    399
    Downloads
    0
    Uploads
    0

    Default

    Originally posted by kevincnc
    Here's another way to attach pulleys on a shaft with at lease one flat. I's better than setscrews or a keyway bacause it won't slip. With no flats I'd go for a taper-lock if you can find one small enough.
    Yeah, I'm looking for taperlock, either pulleys with a taperlock bushing, or a separate taperlock to insert between journal and pulley bore.

    Thanks for the nice pic! It's a great idea, if I can't find taperlocks for the right price, I could very well file flats on my journals and go with your idea.

    I had kinda postponed the timing reduction problems for now, focusing a bit on the motors. But this is a good solution!

    Arvid



  16. #56
    Registered
    Join Date
    Oct 2003
    Location
    Sweden
    Posts
    399
    Downloads
    0
    Uploads
    0

    Default

    Originally posted by balsaman
    Avrid, do those drives use step and dir signals? You should be able to fool the drives by setting the resolution incorrectly in the software. Two wrongs making a right in this case....?

    E
    They use an analogue +/-10 V signal for speed input. There's no position servo loop built-in, I'll have to build electronics for that part myself.

    And unfortunately, since they are 3-ph AC servos, the amplifier needs to know the position of the rotor to run the motors. No way to get around this, I'm afraid. Well unless I build a hardware divide-by-two circuit between the motor and amplifier, something I probably could but would rather not do.

    As it is now, the commutation loses sync with the rotor magnets, so the motor just jumps and hums when I jog it.

    Arvid



  17. #57
    Member
    Join Date
    Feb 2004
    Location
    Flagstaff,AZ
    Posts
    304
    Downloads
    0
    Uploads
    0

    Default

    I thought it was a good idea too, but it wasn't mine. The pulleys came on some brushless motors I bought a while back. I wouldn't think vibration would be a problem unless the motor is on a very light assembly. I haven't tried it yet but will on my router I'm building.

    Another pretty good method (better than setscrews on flats in my opinion,) is to drill a "drill point" for a cup-piont setscrew to tighten into. That keeps the shaft from scarring and works even better if you use a short one and tighten another on top of it to keep the first one from backing out. Sorry if someone already suggested that.



  18. #58
    Member HuFlungDung's Avatar
    Join Date
    Mar 2003
    Location
    Canada
    Posts
    4826
    Downloads
    0
    Uploads
    0

    Default

    Originally posted by HuFlungDung
    Here is another belt to check on: Eagle PD synchronous belts by Goodyear. This is a "herringbone" style of belt which is supposed to be much quieter, perhaps 15 dba. The pulleys do not need flanges because of this belt tooth pattern. For the "white" belt series (second to narrowest belt), the backlash is .8 degrees on 22 tooth sprocket.

    I resurrected this post just to update: when I retrofitted my knee mills, of course I threw out the variable speed pulleys and went to a VFD drive.

    On one machine, to connect the motor to the spindle, I used a PolyV belt drive, which is a really fine ribbed belt and pulley. This is nice and quiet, but maybe not really dependable for high torque transmission at low rpm (for tapping).

    The other mill, at first I used a Gates PolyChain. This was all right (very positive drive) up to about 2400 rpm, but when it got up to 3600 rpm, it was damn painfully noisy to be near. And, I have to be near it I was running 6" dia pulleys.

    Then, I went and got the EaglePD belt and pulley system. This is a herringbone belt and pulley. I dropped the pulley diameter to 4.5", because I noticed the momentum of the larger pulleys on the Polychain drive created kind of a start up "lurch".

    Anyways, the Eagle PD herringbone belt is really nice. They say 15 db quieter than regular gear belts, but it is likely 40db quieter than that PolyChain at full rpm.

    Last edited by HuFlungDung; 02-28-2004 at 11:03 PM.
    First you get good, then you get fast. Then grouchiness sets in.

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  19. #59
    Registered
    Join Date
    Feb 2004
    Location
    hh
    Posts
    813
    Downloads
    0
    Uploads
    0

    Default

    Originally posted by Mr.Chips
    How would the resolution on these screws be, since the TPI is fairly low?
    did you look closely at them; they must be .500" pitch



  20. #60
    Registered
    Join Date
    Oct 2003
    Location
    Sweden
    Posts
    399
    Downloads
    0
    Uploads
    0

    Default

    I want to thank everybody for all the ideas on timing reductions. I still haven't decided, but I will keep the different solutions in mind when it comes to chosing. All ideas are appreciated!

    Arvid



Page 3 of 5 FirstFirst 12345 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

Arvid's first CNC machine!

Arvid's first CNC machine!