Re: [CAD_CAM_EDM_DRO] Z-Axis problem - Not Enough Torque?

Hi WT,

The point I was making was not to do with rigidity,
but with a counter-weight to balance the weight of
your
z-axis. Imagine 2 weights on either side of a pulley?
you can balance the weights and then your steppers
wont have to work so hard.

Regards,

Brian

--- WT <pharmapack@...> wrote:

> Hi, Brian.
>
> Thanks for the website but I believe the problem is
> not related to the
> rigidity of the spindle head or column.
>
> With my very coarse ballscrew (and hence, less
> friction compared to the
> original leadscrew), the stepper motor I used simply
> did not have enough
> power or torque to hold its Z position considering
> that I did not even use
> pulley reduction.
>
> Regards,
> WT
>
> ----- Original Message -----
> From: Brian Worth
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Sent: Wednesday, November 08, 2006 10:42 PM
> Subject: Re: [CAD_CAM_EDM_DRO] Z-Axis problem - Not
> Enough Torque?
>
>
> Hi,
>
> Maybe you could rig up a counterweight affair
> similar
> to what this guy did on his mill?
>
> http://www.pathcom.com/~vhchan/cnc/cnc.html
>
> Regards,
>
> Brian
>
> --- WT <pharmapack@...> wrote:
>
> >
> >
> > Hi, all.
> >
> > I think I have a problem with my Z-axis not having
> > enough torque and will
> > appreciate some suggestions and recommendations on
> > what are the possible
> > solutions.
> >
> > Following are the specs of my CNC retrofitted
> > milling machine:
> >
> > 1) ZAY7032 Mill/Drill Machine, 2 HP spindle motor
> >
> > 2) X & Y-axis:
> > converted to ballscrews: 20 mm diameter x 20 mm
> lead
> > pitch (4 start x 5 mm
> > lead pitch),
> > direct coupled to a stepper motor (Nema34, 4.2
> N.m,
> > 6.0A, 2.4Vdc),
> > stepper driver capable up to 7.8A, 80VDC,
> > microstepping (2, 4, 8, 16, 32,
> > 64, 128, 5, 10, 25, 50, 125) and presently set at
> > 5.7A, 25 microstepping, &
> > 37VDC
> > Mach3 - 250 steps/mm, 2000 mm/min
> >
> > 3) Z-axis:
> > converted to ballscrew: 15 mm diameter x 40 mm
> lead
> > pitch (3 start x 13.3333
> > lead pitch),
> > belt driven (same ratio/no reduction) by a stepper
> > motor (Nema34, 4.2 N.m,
> > 6.0A, 2.4Vdc),
> > stepper driver (same as above) but set at 50
> > microstepping
> > Mach3 - 250 steps/mm, 1000 mm/min
> >
> > 4) Power supply:
> > Has multi-tap output capable of 37, 47, 52, 59, 65
> > VDC,
> > currently using 37 Vdc,
> > about 1 KVA
> >
> > Presently, the X & Y-axis seem to be working very
> > well with no backlash and
> > lost step. However, the Z-axis seems incapable of
> > moving up correctly under
> > load or when cutting or milling. Also, noticeable
> > chatter or vibration of
> > the spindle head when milling MS plate at only 0.2
> > mm downfeed and 100
> > mm/min feedrate.
> >
> > I know my ballscrews are very coarse pitch but I
> > have to live with it as
> > that is what is presently available to me. And
> > hence, the reason I set up
> > the microsteppings to 25 (X & Y-axis) and 50
> > (Z-axis) to gain more
> > resolution. Considering that the X and Y-axis are
> > capable of moving the
> > heavy X/Y table, is there any reason why Z-axis
> can
> > not hold its position
> > under load?
> >
> > So, are there any solutions or suggestions to
> solve
> > the problem within the
> > present hardware parameters? If not, what hardware
> > changes should I make?
> >
> > TIA for all your kind response.
> >
> > Best,
> > WT
> >
>
>

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