Need Help!- small steps on a shallow taper

[Roll1]

On a Mori-Seiki lathe SL-603, with Fanuc 18, I want to turn a shallow taper:
20" on Z axis and .0025" on X axis. The finish is not regular, I feel some small steps (around .0004") every 6 or 7 inches. Is it somethings that could be adjusted in the control?
With our 2nd SL-603, we don't have this problem.

[underthetire]

First thing would check mechanical problems, like level, lube, x gibs etc. Ballscrew comp in wrong can cause this. The other i saw a lot of, was more of a finish problem on very shallow tapers:

Two options, Fanuc comes out either way. First is the high resolution option, gets rid of that completely. Second, is they can set up the drives for a bell shaped torque curve. Both will eliminate that problem, but the high res was much better. BTW, that is common on all fanuc machines when they got rid of the belt drives on the axis.

[Roll1]

Thanks for the reply. I already check mechanical things. No backlash. The machine is in good condition.
Could you explain more on the high resolution option?

[underthetire]

It basically gave you .00005 programming and position, but for some reason on those it got rid of the very shallow taper issues. I also know switching to metric helped some. Ive seen this on multiple machine brands, including Mori. The newer machines with the alpha-i motors and drives don't seem to have this problem.