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Servo Motor CNC Project — Parallax Forums

Servo Motor CNC Project

ScopeScope Posts: 417
edited 2010-01-26 00:38 in Robotics
Hello Wonderful Folks,

You too Whit (j/k, ha), I have a desire to make a *simple* CNC router using my Boe-Bot.

Does anyone have any suggestions for hardware - getting the servo motors to work with gears, belts/chains, or whatever?

I thought of something totally crude that involved sliding mechanisms used in drawers. I've asked the IT person where I work for some old, unusable printers but he's extremely busy. I also thought of using a long threaded rod w/fabricated nuts that . . . it seems crazy to talk about this, so, I'll just ask for some suggestions rather than prove my mechanical understanding shortcomings.

Thank you,

Scope

Comments

  • Brian_BBrian_B Posts: 842
    edited 2010-01-22 12:49
    Scope,
    After seeing this video, I'm convinced that anything can be made into a cnc router.

    www.youtube.com/watch?v=quN37YskoaM


    I have done a lot of thinking about the possibility of making a small cnc mill out of hobby servo's ,but have to finish up some other stuff first.


    Brian

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    "Imagination is more important than knowledge..." Albert Einstein
  • ScopeScope Posts: 417
    edited 2010-01-22 12:55
    I'll peruse the video upon my return to the PRB (personal residential base) - they block lots of stuff here at work - but thanks for the link.

    I don't care about cutting 6061 to within thousandths of inches - I just want to demonstrate a functional model to my students - show them what can be done - and do so w/minimal financial investment. [noparse];)[/noparse]

    Thanks - I'm really looking forward to this project - a departure from the excellent books & lessons that come w/all my Parallax systems.
  • Brian_BBrian_B Posts: 842
    edited 2010-01-22 13:05
    Scope,
    ·Here is what you are missing :-)

    Brian

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    "Imagination is more important than knowledge..." Albert Einstein
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  • WhitWhit Posts: 4,191
    edited 2010-01-22 13:24
    Scope,

    Even though you tried to start some trouble above smilewinkgrin.gif - you might get some ideas here - http://forums.parallax.com/showthread.php?p=828989
    Steve's ChessBot has a neat, but simple servo and wheel gantry (which he calls it the cart)·to move his robotic arm. I like the wheels running in channels part of the design. The pics and the videos might get some ideas flowing. Check it out.

    Good luck and be sure to post back if you get something going.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

    Post Edited (Whit) : 1/22/2010 1:34:21 PM GMT
  • icepuckicepuck Posts: 466
    edited 2010-01-22 16:49
    You wouldn't want that kind of robot to be roaming around a house with hard wood floors!freaked.gif
    -dan

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    Arguing with myself--sometimes me, myself, and I don't always agree.
    (Former) Caterpillar product support technician
  • Possum79Possum79 Posts: 30
    edited 2010-01-23 17:57
    Hey all. New here and loving it. I have been wanting to build a CNC for a while now. I highly recommend you check out www.cnczone.com They have a ton of adivce as far as home brew projects go. Also good place to "borrow" some design concepts.
  • ScopeScope Posts: 417
    edited 2010-01-23 18:33
    Thanks Possum79 . . . missing an "o" by any chance?

    Here's a quick sketch of what I'm thinking about - using threaded rods supported w/ball bearings inside c-channel - the trolleys (?) are attached to the threaded rod via two nuts and along they go . . . blah, blah, blah . . .

    mmc32g.jpg
  • ScopeScope Posts: 417
    edited 2010-01-23 22:11
    I just returned from the home supply store w/some hardware . . . time to make a prototype! [noparse]:)[/noparse]

    o5ufxf.jpg
  • ScopeScope Posts: 417
    edited 2010-01-24 01:07
    Getting a little closer to testing prototype 1

    90zgb5.jpg
  • ScopeScope Posts: 417
    edited 2010-01-24 02:22
    ARGH!!! The rubber band drive belt didn't work . . . this was probably obvious to everyone but me . . . but, I'm still working on getting it going . . . one axis at a time . . . [noparse]:)[/noparse] . . .
  • Brian_BBrian_B Posts: 842
    edited 2010-01-24 03:22
    Scope,
    I went through this whole cnc deal about 8 years ago and can tell you from experience that you'll have alot of disapointments if you don't do a little research.

    The hobby servo's you are trying to use don't have enough power to pull that big of lead screw ,if you must use treaded rod then go with a small fine tread one (1/4 or so) and the hook directly to it with a hose or somthing, Also they will not provide you with any position feedback.

    Just my 2 cents

    Brian

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    "Imagination is more important than knowledge..." Albert Einstein
  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2010-01-24 05:27
    Scope,

    I agree with Brian_B·... "The hobby servo's you are trying to use don't have enough power to pull that big of lead screw" ... "if you must use treaded rod then go with a small fine tread one (1/4 or so) and the hook directly" ...· This method will work, but it's not very fast.


    Servo Interface to 1/4 inch all-thread:
    Next time you are at the·hardware store, look for 1/4 inch inner diameter plumbing·pipe, I think it's for Hot/Cold water lines.· For some reason they keep it·away from the normal plumbing section.· Anyway it only takes a small amount about an inch or so to make a nice interface between a standard continuous rotation servo and 1/4 inch all-thread.· For finer pitch use metric all-thread.· Between the servo and the plumbing pipe I used a small shirt-pin as a cotter pin.· Hint: to drill a very small hole, use a shirt-pin of the same size in a dremel tool.· Between the plumbing pipe and the all-thread use a nut on the all-thread (not shown in picture) to form a 'lock' against the plumbing pipe as to not unwind the·all-thread from the plumbing pipe during operation.····

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.

    Post Edited (Beau Schwabe (Parallax)) : 1/24/2010 5:32:48 AM GMT
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  • W9GFOW9GFO Posts: 4,010
    edited 2010-01-24 05:31
    If you haven't already, check servocity.com for chains and gears that will fit on servos. I think the servo could drive that lead screw if it were geared down. You will need an encoder somewhere though.

    Rich H

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    The Simple Servo Tester, a kit from Gadget Gangster.
  • ScopeScope Posts: 417
    edited 2010-01-24 12:22
    You folks are awesome! Rather than feeling really embarrassed and frustrated, your comments make me feel encouraged and optimistic.

    Thanks!

    I have a few large - as in gigantic - r/c servos I was thinking about converting to continuous rotation, but it seems like I should figure out what works, and let the experiences of others help shorten my learning curve.

    Just curious, has anyone ever converted an Etch a Sketch to CNC?

    Happy roboting,

    Scope
  • Brian_BBrian_B Posts: 842
    edited 2010-01-24 13:57
    Scope,
    I like the Etch a Sketch idea. I've been thinking of building one of these flex pickers with 4 servo's and giving a small router.





    Here is another link to get the juices flowing.

    http://fabathome.org/wiki/index.php?title=Main_Page

    I hope some of this info will help.

    Brian

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    "Imagination is more important than knowledge..." Albert Einstein
  • ScopeScope Posts: 417
    edited 2010-01-25 00:52
    Thanks

    Here's just a quick "what if" sketch:


    bw_boe-bot_cnc_021.jpg?t=1264380791

    (and yeah, I realize there would have to be holes above the servo horns which would allow attaching the bracket to the servo - I'm lazy)
  • kf4ixmkf4ixm Posts: 529
    edited 2010-01-25 14:26
    Just fyi, McMaster-Carr is a great place for just about anything like roller bearings, threaded shaft in both left and right hand threads, couplings, flat, round, square stock in just about any type material·and such. plus they have no minimum order.

    http://www.mcmaster.com/#
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2010-01-25 23:49
    Beau

    Where did you get those servo's I need to get some that have some power to them

    I hope that you do not have to pay and arm leg for them··

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    ··Thanks for any·idea.gif·that you may have and all of your time finding them smile.gif

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    Sam
  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2010-01-26 00:38
    sam_sam_sam,

    Those servo's are Parallax's continuous rotation servos...

    In that particular application I used a metric all-thread that had a pitch of 40 threads per inch allowing me to get away with a lower torque servo motor.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
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