There are tuning parameters for the BST drives, however the descriptions/translation are pretty poor.
Pn153 up for Speed Control mode, and Pn188 up for Torque Control Mode.
Speed control mode is generally easier to setup, but Torque Control mode will give better performance if it can be set-up correctly (if you don't get it setup correctly, it'll give much worse and far more unstable performance than Speed Control mode).

Without an autotune function, you need to play with the settings manually, and you need to tune them while attached to the machine, as the extra load acts like a damper.


For comparison, my lathe holds within 6 counts on the Z axis, and 17 on the X-axis. The X-axis is a slant axis with a turret on it, so it's got a bit of an imbalance.
I ended up using speed control mode, as in torque control mode I came to the conclusion the internal filtering of the servo drive was causing too much of a delay to change of input voltage, as even with all filtering reduced to an absolute minimum, there was still a delay in the response plots (KFlop lets you plot position commands against encoder feedback, so you can see exactly what is happening).

Interesting, thanks. As you said, the translation is pretty poor, I would need an illustrated  "How to.." guide before going anywhere near those settings i think