Re: [CAD_CAM_EDM_DRO] Re: Video of my resonance

Dan,

I have tried that, I even have the jumper over for the larger 42 sized motors. I think that I need more reduction, as 0.1mm is only 6.8 steps. Which means that it is really only 0.68 steps without microstepping, and they say that microstepping isn't that accurate etc. So I really think that I need a much larger reduction.

At the moment it is about 2.57:1.

Peter
Australia

----- Original Message -----
From: Dan Mauch
To: CAD_CAM_EDM_DRO@yahoogroups.com
Sent: Tuesday, September 26, 2006 8:12 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Video of my resonance


From what you did it now does sound more line a resonance/ midband
stabilization problem. Have you tried adjusting the G201 trim pot ? Simply
run the motor at the speed that is giving you the problem and adjust the
trim pot. If this adjustment doesn't help at all or neally not at all then
open up the G201 case and set the jumper to the Nema42 setting. I have
found some nema34 motors that require this change and it make a heck of a
difference.
Dan Mauch
low cost stepper and servo motors.
cases for Gecko drives
kits and assembled 3-4 axis drives
www.camtronics-cnc.com
www.seanet.com/~dmauch
----- Original Message -----
From: "Apalais" <apalais@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, September 26, 2006 8:34 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Video of my resonance

> Dave,
>
> Yes I will have to get a larger pinion, as it will be smoother. Actually
> it isn't too bad now. The main reason why I have used a smaller pinion
> rather than the proper larger sized pinion is so that I could make
> advantage of more reduction.
>
> John,
>
> Well, I disconnected the spring that has tensioned the pinion up to the
> rack. Then I disabled the slaved A motor in mach so that only the X motor
> was running.
>
> Then I repeated the speed tests etc, the noise was much much louder with
> it just hanging loose in the air. Obviuosly the spring pulling tight to
> the rack some how cancels out some vibrations.
>
> Then I done some more stuffing around and though to myself. When you
> first setup Mach, the set steps per unit number is 2000. I asume that
> this is a pretty common value for people who run ballscrews or similar
> with the higher gearing/reduction.
>
> My steps per unit is only 68. So then I thought I would change that to
> 300. Then I ran a program at 68 steps per unit and then again at 300
> steps per unit. What happend? .....The program running at 68 steps per
> unit still had lots of vibrations. But at 300 steps per unit, the
> vibrations disapeared. Then the motor sounded like some CNC milling
> machines that I have heard before, with that funny pitch changing sound.
>
> This really does make me beleive that I need more reduction on my table.
> If I am using 68 steps per unit and that is with 10x microstepping. That
> is only 6.8 steps per mm, compared to the one at 30 steps per unit or the
> 2000 steps per unit which equate to 200 steps per mm with out
> microstepping.
>
> I'm 99% sure that all it, is is the motor spinning so slow that every step
> in the motor is felt. When you turn the motor shaft by hand, you can feel
> the steps in the motor as well. I really think that I need more
> reduction.
>
> I'm going to post a question on the mach yahoo forum asking if anyone else
> has the larger 34 sized motors and what their steps per unit is set to.
> Then I will see if I can get someone to change it to 68 steps per unit,
> and move their machine slow to see if they get the same results.
>
> Peter
> Australia
>
>
>
>
> ----- Original Message -----
> From: John Dammeyer
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Sent: Monday, September 25, 2006 7:20 PM
> Subject: RE: [CAD_CAM_EDM_DRO] Re: Video of my resonance
>
>
> Hi Dave,
>
> Just one thing about your process below. If indeed the resonance is like
> the twin engine beat (or two almost in tune instruments), then just
> loosening and retightening might not do it. What I'm thinking is that if,
> at their rest position the first step energizes different windings, they
> motors could still be out of sync although now not by micro-steps so
> perhaps
> it's not an issue?
>
> But, depending on how his hardware is configured, does one motor turn
> clockwise and one counter clockwise? What I'd try for, is to ensure that
> each motor energizes the same winding from that 'rest' position you
> describe
> below and that the motor moves in the correct direction when those
> windings
> are energized.
>
> Again, perhaps that's not needed. Might well just be a micro-step out of
> sequence issue. Normally the beating of the two out of sync propellers
> comes from one engine running at a slightly different speed. Just like an
> analogue mixer in radio, what we here is the sum and the difference of
> the
> two frequencies.
>
> One way to find out, if it's mechanically possible is for him to
> disconnect
> and decouple one of the two motors. Since the gantry is on a track and
> not
> running a double worm, one motor might be able to move the works at the
> slow
> resonant speed.
>
> Just more ideas. Perhaps I'm way off too.
>
> John Dammeyer
>
> > As for the out of sync, that would be simple to handle.
> >
> > I think you could just power off everything (lock the table to keep it
> > in posistion.
> >
> > Loosen the motor pulleys so the motors can move easily.
> >
> > Then tighten the pulleys again.
> >
> > That should have the motors cog into a natural posistion.
> >
> > If the tightening of the pulley moves something, then it may go out of
> > sync.
> >
> > I could be wrong, so comments are welcomed.
> >
> > Dave
>
>
>
>
>
>
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