[Robotgroup] Still working on XY frame

[Paul Atkinson]

http://www.raymortool.com/Sprocket_Index.html is one source for beaded chain
drive components. Since beaded chain is used in some clocks, maybe a clock
supply place would have them, like SLaRose.com or timesavers.com.

On 10/25/07, Paul Atkinson <pmatkinson at gmail.com> wrote:
>
> I was going to mention the bead chain drive at Maker Faire, but you saw
> that already. I did see someone making their own pulley for bead chain by
> using a small V-belt pulley and some epoxy putty (thick knead-able stuff) to
> get the bead-grabbing-shape.
>
> Another variation is the string drive that was used in radio dials.
> Basically they wrapped string around a couple of pulleys and had a spring to
> keep it tensioned. I imagine that there was some slippage, but with a human
> in the loop it didn't matter much.
>
> Since there are a lot of cheap printers out there, you could use their
> method - toothed belts and matching pulleys. Maybe harvest some parts from
> dead printers.
>
> Paul
>
> On 10/25/07, Gray Mack <gray_mack at yahoo.com> wrote:
> >
> > This is to be a stepper driven 2ft x 2ft frame.
> > The goal is to move a small object around inside the
> > frame like a white board marker or robotic gripper and
> > only needs enough torque to lift itself, this is not a
> > machining tool.
> >
> > My first experiment was with pieces of an actual
> > etch-a-sketch. I cut the corners off, mounted them in
> > the corners of the 2ftx2ft frame and attached motors
> > to the drive wheel and ran the mono-filament line. The
> > line loops around 3 sides of the frame and then back
> > again (about 12 feet total) and the cross bar attaches
> > at two points for parallel travel.
> > Results- the torque was a little much for my steppers,
> > the wheels made screeching noises and there was
> > occasional slippage at the drive wheel. Any slippage
> > means I don't know where the XY plotting tool is and
> > that's bad.
> >
> > Next I tried a screw drive. I wanted to mount the
> > screw drives on the sides rather than the middle of
> > the frames to keep it open and this increased the
> > amount of side torque, but maybe that could be offset
> > by having something better than one bolt connecting
> > the drive hardware around the all-thread push rod.
> > Results- the movement was 200 steps per rotation of
> > the stepper motor times 20 threads per inch on the
> > all-thread, thus 4000 steps per inch. So the speed of
> > my stepper tops out at about 1 inch per minute or 24
> > minutes to draw a line from end to end -unacceptable
> > for this application.
> >
> > I am considering going back to some sort of
> > etch-a-sketch like design that wont slip
> > so I would probably need some type of ladder chain or
> > toothed belt drive with at least 2-3 feet of drive
> > belt spliced to the rest of the cord to make 12ft
> > length.
> >
> > I have also been thinking about ball-chain or
> > bead-chain drive (
> > http://www.raymortool.com/Sprocket_Index.html ) Does
> > anyone know anything about this type of stuff? I have
> > seen metal bead-chain at Breed&co but have not seen
> > bead-chain sprockets. Maybe they could be made somehow
> > or found in old window blinds?
> >
> > I saw a ball-chain drive used at maker faire on a
> > Hektor like plotter ( http://www.hektor.ch/ ) An upper
> > right and upper left chain are adjusted and gravity
> > triangulates the plotter tool position.
> >
> > I am looking for some low cost ideas I can experiment
> > with in order to find what will work best.
> >
> > Another possibility is a belt drive horizontal
> > positioning system that is vertically lifted
> > mini-blind style?
> >
> > I am hoping for something relatively quiet.
> >
> > -Gray
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Tired of spam?  Yahoo! Mail has the best spam protection around
> > http://mail.yahoo.com
> > _______________________________________________
> > Robotgroup mailing list
> > Robotgroup at puremagic.com
> > http://lists.puremagic.com/cgi-bin/mailman/listinfo/robotgroup
> >
>
>