Subject:
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Re: the LEGO CNC-Machine
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Sat, 1 Sep 2007 20:31:21 GMT
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Viewed:
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18456 times
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"daniel" <daniel.formatc.at.gmail.com> wrote in message
news:Jnp0Cy.2CJ@lugnet.com...
> In lugnet.robotics.rcx, Robert G Fay wrote:
> >
> > http://www.ozbricks.com/bobfay/newmill.htm
>
> i see that the x axis on your machine is driven by a worm gear, over a 24t
> to a
> 16t gear to the gear rack on the bottom of the table.
This X axis gear box is loaded so there is no backlash. The 16T gear on the
right side has a hole through it and is fixed to the shaft with a serrated
half bushing. This allowed me to counter rotate the gear to take up all the
backlash including the double row of rack gearing.
also, the z axis seems to
> use an idler gear. that's exactly the setup i've built, you can see it
> here:
> http://formatc1702.prul.net/gallery/v/robocnc/DSC03536.JPG.html
> on top left, next to the tool changer idea (right next to the tiny word
> "tool").
> i drew an 8t gear but i'm using a 24t now.
I am not sure what your seeing on my Z axis. The four gears all engage the
two segment worm drive and transfer motion to the dual racks on the slider.
This is not a good design because the head is a little off center line. This
is due to the offset of the worm thread from one side to the other side.
Fun, but not practical.
>
> >
i am planning to use a pole reverser short-circuited on one
> > > side as
> > > a rotation counter
> >
> > Is this Lego?
>
> yes, check out this link:
> http://lego.brandls.info/legtips.htm#Rotationssensor
> scroll down a bit to see how to short-circuit the pole reverser with a
> looped
> cable. this acts like a touch sensor that opens/closes 8 times in one
> rotation.
That was a new name for me and I did not recognize the part. I have never
tried to use it that way. I will be interested to see if it performs well
for you. All of my machines were mostly "open loop" as I did not have more
than one rotation sensor. I finally acuired three more when I built Jin
Sato's "Mibo". That was such a luxury to know where the axis would go.
>
> out of curiosity, how long is the axle for your y-axis worm beam? because
> i
> guess your max axle length limits the length of your axis unless you build
> a
> more advanced setup..
The worm segment has splines all the way through, so it can act as a
coupling for additional axles. I used some plastic washers to make sure all
the segments stayed engaged with each other. If your a purist, you can use
Lego rubber bands for washers.
Your drawings show a lot of good planning. Try to keep your X and Y drive
ratios the same. It will make the programming much easier if you have to
start out with "open loops",
Bob
--
http://www.ozbricks.com/bobfay
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Message has 1 Reply:
 | | Re: the LEGO CNC-Machine
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| (...) by loaded, you mean it carries the workpiece and not the tool? (...) ooh i see now, so that's the anti-backlash gearbox!! awesome, i would never have thought of that. but i don't know if i will be able to integrate that mechanism into my (...) (17 years ago, 2-Sep-07, to lugnet.robotics.rcx)
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Message is in Reply To:
| | Re: the LEGO CNC-Machine
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| (...) 16t gear to the gear rack on the bottom of the table. also, the z axis seems to use an idler gear. that's exactly the setup i've built, you can see it here: (URL) top left, next to the tool changer idea (right next to the tiny word "tool"). i (...) (17 years ago, 1-Sep-07, to lugnet.robotics.rcx)
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