Re: Knee or Quill Drive?

Hi Bernard,

You should get the Z feed on the knee to work. It is worth the effort.

A knee feed will save your back
allow longer holes to be bored
may improve the holes as the quill being locked will not shake

also, if you think of the feed speed, it is VERY slow for boring. this means you can drive it 4:1 or 8:1 and still have it very useful.
instad of your 2:1 Also, vertical travel is less and you do it less often so a slower Z is not a large problem.


Don't scrap the quill feed idea though. no reason not to fully automate your machine.

Dave

--- In CAD_CAM_EDM_DRO@y..., "bwrfromuk" <bwjarandall@c...> wrote:
> Hi Group,
>
> I am in the process of converting an Enco 9x42 mill to CNC. X & Y
> axis are working fine and I recently connected drive to the knee. I
> am using 600oz-in peak servos with G320s, all axis are geared down
> 2:1. Using Master5 X and Y feed limits at 46 in/min, Z loses track at
> 3 ins/min. The torque measured to lift the Z axis is 40lb-in (belt
> off). The measured motor current (lifting)is 8 amps, measured across
> a 0.1ohm resistor with a 'scope, ripple across the 37 VDC supply is
> 2.5Vp-p. From the limited data on the motors the peak current rating
> is 12 amps max, nominal voltage is 38 volts, RPM is 900.
>
> The question I am now facing, and asking the groups advice on, is it
> best to carry on working on the knee drive or would I be better off
> somehow driving the quill?
>
> To date I have not replaced the Z acme screw, how much improvement
> would a ball-screw give and would it add further complications like
> the knee dropping if the drive kicked out?
>
> How large a motor do I need for the measured torque? From the
> measurements and talk with Marriss I could and should improve the
> supply with additional capacitance and the supply voltage could be
> increased some, but the fundemental problem seems that the motor is
> too small. Does anyone have a source for reasonably priced brush
> servos?
>
> What strategies do you recommend for driving the quill? I've looked
> at Jon's method of driving a dog through the stop mechanism in the
> quill and also seen a pulley on the quill coarse feed lever. Any
> others?
>
> All comments / suggestions gratefully received.
>
> Bernard Randall