Converting a rotary table

Have any of you converted one of the "Little Machine Shop" rotary tables and
would be inclined to share your experience and/or advice? I scanned through
the files section but nothing jumped out at me.

Thanks,
Andrey

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of ibewgypsie
Sent: Tuesday, July 26, 2005 1:36 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Windows timing subroutines, how do they work?
JitteryMonkey pic

Howdy Mariss..

Are ya after my heart and mind? I'll check it out. If you don't know
me, I love new toys.. Anything to make my machine better, quicker,
stronger, shinier.. (I bolted some polished stainless to it)

I found your Jittery Monkey..
http://home.alltel.net\dec4857\jitterymonkey.jpg
http://home.alltel.net\dec4857\jitterymonkey1.jpg

My page..
http://home.alltel.net\dec4857\index.htm

David

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis"
<mariss92705@y...> wrote:

> David,
>
> Has happened already. Conventional constant contouring techniques
> use "look-ahead" schemes and complex math to move at a constant
> velocity along a concatened line segment path.
>
> The G101 uses a velocity-word stream to the step pulse engine. This
> allows for a unique and very simple constant contouring method I
> call "look-behind". Simply put, the generated velocity-words (along
> the concatenated path, no accel/decel) are passed thru a moving
> average filter whose output goes to the pulse engine.
>
> Some advantages over conventional techniques is this method requires
> no analysis of the line-segment coordinate data, uses only add,
> subtract and division by powers of 2 (bit right-shift). It natively
> adapts to the requested vector velocity, automatically increasing the
> rounding at line-segment nodes the faster it goes. The filter can be
> switched in and out on the fly to allow accel/decel where sharp
> direction changes are required.
>
> If you want to see it run, please see www.geckodrive.com, go to
> the 'support' page and pick the very last item listed (video). The
> pen in the video is tracing at 300 IPM on a 6" by 6" XY stage having
> 5 TPI screws. The motors are 3A/phase PK268s at 24VDC. The drives are
> G201s. It could go much faster but the screws sound very unhappy
> above 1,500 RPM.
>
> The file is about 5 megabytes so having a broadband connection is a
> real plus.
>
> Mariss
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "ibewgypsie"
> <ibewgypsie@h...> wrote:
> > What is probably needed? One Timing generator running at a obscene
> > speed, smaller processors that get a bluetooth into buffer dump for
> > distance or usb, or? Each processor handles one axis, reading the
> > encoder to adjust it's own loop-feedback, running pulse ratio per
> main
> > engine. All interpolated, All with a error out line back to main
> > source to err-out. Each axis dedicated to itself. Then here-we-go..
> > Look ahead software that processes speed changes per gcode line and
> > pid's it all to that frequency to make desired end of line
> directional
> > changes without losing it's interpolation between axis. Ramp up,
> Ramp
> > down each line is not a good way to machine, but the only thing I
> have
> > saw on my machine.
> >
> > Will it happen, probably not.
> >
> >
> >
> >
> >
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "caudlet" <thom@t...> wrote:
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis"
> > > <mariss92705@y...> wrote:
> > > > In my opinion it should not be the task of a PC to do
> the 'donkey
> > > > work' of generating step pulses be it Linux, DOS or Windows.
> That is
> > > > a task that belongs to dumb dedicated hardware.
> > > >
> > > > A PC is an 'intelligence engine'. It's task is to do a lot of
> math
> > > > and make decisions. Its output product should go to a 'pulse
> engine',
> > > > hardware finely tuned to the task of generating of producing
> pure and
> > > > clean frequencies on demand from the PC.
> > > >
> > > > These are tasks are so diametrically opposed it's like using a
> claw
> > > > hammer for a screwdriver. In a pinch you can do it but it's not
> > > > pretty.
> > > >
> > > > That also pretty much surmises what I have seen from most PC
> based
> > > > CNC programs. The step pulse phase jitter is horrible even from
> the
> > > > most popular out there. The motors sound like a barrel of
> agitated
> > > > monkeys and I have the scope pixs to prove it.
> > > >
> > > > If things are going to be done right, the PC has to interface
> to some
> > > > kind of step pulse engine.
> > > >
> > > > The 'agitated monkey' part. Motors that sound like that are
> being
> > > > robbed of their potential torque especially at high speeds.
> Phase
> > > > modulation imposes unnecessary torque demands (infinite
> impulse
> > > > functions) on the motors. Said more simply, you pay for all
> that
> > > > noise in performance.
> > > >
> > > > Mariss
> > > >
> > > >
> > > The problem in the past and currently in the present, is that
> there is
> > > no "standard" for an external pulse generator so you end up
> having to
> > > buy a "system" that is composed of software and matching
> hardware.
> > > Your options start to dwindle and if you want/need/desire to
> change
> > > the software you have to throw away the entire system. It would
> be
> > > like every car manufacturer deciding to use non-standard tires
> that
> > > only they provided or each TV network broadcating in a different
> > > format so you had to buy a set specifically for their signal
> format.
> > > From a pure engineering standpoint it might make sense to hand off
> > > signal processing to another circuit like a DSP card, but it
> needs to
> > > have an open set of standards that ANY software company could
> write
> > > to. If it's going to end up as a PC perhipheral then it needs to
> have
> > > drivers or open standards that make it useful with different
> > > programs. Show me a pulser card that is not single source, has
> open
> > > standards and is supported by multiple vendors (especially MACH)
> and
> > > I'll get in line to buy one.

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