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Another approach to a DIY CNC? — Parallax Forums

Another approach to a DIY CNC?

Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
edited 2010-04-13 11:50 in General Discussion
I've had this idea rattling around in my head for the last couple weeks.
(Due to the Propeller contest, and a thread on Savage Circuits.)

There are several folks who are working on a DIY CNC using a combination of salvaged parts and various materials.

What if...?

Most of the DIY CNC projects I've looked at use an old scanner as the base of the unit..

I've been thinking that if someone were use some common, but very specific sources for salvaging the parts,
say an HP Scanjet 4c (common and cheap) with an additional parts purchased from large "chain" sources,
we could create a CNC which could be replicated by almost anyone anywhere.

Obviously, I'm not talking about anything which is going to fabricate steel, but cutting plastic, or being able to
do PCB fabrication on my bench would be pretty slick.

There's the idea... comments? toss reality into it? [noparse]:)[/noparse]

OBC

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Comments

  • Chris_DChris_D Posts: 305
    edited 2010-04-12 22:48
    OBC,

    Hmmm, I can't say as I remember what the inside of the last scanner looked like that I took apart.· I suspect that it would be far too weak to do much of anything beyond moving the light bar inside it.· As they are driven by stepper motors, having an under powered machine is a really bad thing.· Once your stepper skips steps, they can never be made up and the end result is not going to be so good.

    Perhaps you could look for some flat-bed plotters. I remember those being fairly robust.



    Chris
  • CannibalRoboticsCannibalRobotics Posts: 535
    edited 2010-04-13 01:36
    @OBC: I agree with Chris, scanners are too much plastic to even move a reasonable cutting mechanism much less push against the blade. BUT!

    If you used a LASER or a Plasma Torch as a cutting medium, there is no lateral force on the cutting tool!



    Jim-

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  • MicrocontrolledMicrocontrolled Posts: 2,461
    edited 2010-04-13 01:49
    CanabelRobotics has a good idea. If just etching PCBs these may do the trick.

    cgi.ebay.com/808nm-DPSS-pump-high-power-burning-laser-diode-1-watt_W0QQitemZ180488966749QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2a05fb125d

    For larger items like plastic try this

    cgi.ebay.com/High-Power-Laser-Module-450-mw-Cutting-Burning-diode_W0QQitemZ180446582275QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2a03745603

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  • mctriviamctrivia Posts: 3,772
    edited 2010-04-13 05:08
    there is no way you will etch a pcb with that laser. however if you spray paint it black you could probably burn off the paint then etch it in feric cloride.

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  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-04-13 05:20
    could a laser expose a negative-acting photo resist coating?
  • mctriviamctrivia Posts: 3,772
    edited 2010-04-13 05:56
    yes thought the spray paint method would be cheaper and give you the same end result. using photo resist though may give you finer detail if you can get a finer point on a low power laser.

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  • Alan BradfordAlan Bradford Posts: 172
    edited 2010-04-13 11:50
    Hi All,
    The first thing you need to do is decide what you want·Your CNC to do.
    CNC machines do everything from cutting, making screws, carving wooden signs,·to measuring the thickness of Bubble Gum.

    Next you·have to determine the accuracy needed for your machine.
    A lot of the cheaper CNC Kits use a PC as host and stepper motors in open loop mode.
    There is no way to correct for any position errors as the system does not know where it is.
    It navigated bt 'Dead Reconning'
    This works suprisingly well, when you are not pushing a cutting tool very hard.
    Plasma torches and routers work well, and knives and lathes do not work as well.
    This would push the limit of a Stamp but the Propeller should work well.(I havent figured the prop out yet. 41 years of Basic programming is hard to undo!!)

    The next step is Servos or Steppers with encoder feedback.
    This would allow your machine to correct for position errors.
    It puts more burden on the CNC to track Actual position versus CNC Position.
    This is called following error, and is helpful to keep your finished product inside your design parameters.

    Check out··· www.cnczone.com
    They have lots of information on all types of CNC's and most of them are hobby grade products and people.
    There is also a forum on many diffrent types of CNC's.
    It may be easier than reinventing the wheel.

    Good Luck,


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    Alan Bradford ·N1YMQ

    Plasma Technologies
    Canaan NH 03741
    www.plasmatechnologies.com
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