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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