Re: [CAD_CAM_EDM_DRO] Z-Axis backlash removal

One is to have the mass always down ie loading the head down.
This is common on bridgeports where you mechanise the knee -
as the table and head is heavy, it always takes away any backlash.

Its probably the easiest, and what I would recommend to try at least.
No machining or pieces needed.

A ballscrew has great force -
you can easily have a 100 kg or 200-300 pounds mass on the head and lift
it with a small stepper.
A 200 ozin stepper at 3:1 moved my 60 kg mass cnc grinder head assembly
easily, and gives resolution of better than 0.003 mm.
I used 5/8 rolled mcmaster (nook) ballscrews.

But do not overload on the acceleration ie the acceleration I used on
the z was much lower on the z than on the x or y.
The only situation where this would not be optimum, would be large fast
z-axis movements.
In conventional milling this never occurs, or I cannot imagine any
situation where it would.

This will not work with a very light head assembly - the mass must be
sufficient to prevent bouncing of the head.
I suspect about 60-100 kg is minimum, so may not work with a mill drill
- it will depend on your use.

Dan Mauch wrote:

>
> Your post doesn't say what size your mill drill is or what model.
> Most mill drills seem to come stock with .020" backlash. Most of the
> problem is due to the machining of the bores for the cross shaft and
> pinion. They machine the bore so that the pinion is loose against the
> rack on the quill. The other problem is the worn wheel housing is
> properly adjusted so that the worm contacts the worm wheel properly.
> There are a couple solutions.
> One is to counterbalance the quill so that the backlash is always up.
> The other method is to replace the existing cross shaft flanged
> bearing with a new one that is made excentric. This would also require
> the machining of the shaft on the worm wheel side so that there are
> two eccentric bearings holding the cross shaft. These are then roated
> until the backlash is gone. If you want I have a detailed explaination
> of this procedure. Give me your email address and I'll send it to you
> am also woking on an air spring that has a constant 40 lb lift of the
> quill. I have one in my mill drill but I haven't had time to to much
> testing
> Dan Mauch
> economical 3D scanner software and kits
> low cost stepper and servo motors.
> cases for Gecko drives
> kits and assembled 3-4 axis drives
>