At the beginning, the printer moves to the object to be lasered with a button. This is the first point, because with a round object this can be more difficult....
The distance is set with the button, because anything that is a few mm higher or lower is no longer in focus and is therefore not engraved and/or engraved weaker and wider.

So if the writing on the biros is only supposed to be an estimated 3mm high, it might work... otherwise rather not.