Datamax-O'Neil H-Class Operator’s Manual - Manual (Page 101)

H-Class 91
Adjust the Printhead Leveling Cam as follows:
A. With media loaded, download your label format (or use a Test Menu format) then
begin printing a small batch of labels.
B. While observing the printed output, rotate the Leveling Cam counter-clockwise until
the image fades across the label, as shown in Example 1 (below).
C. While observing the printed output, rotate the Leveling Cam clockwise until the
image is complete, with even contrast, as shown in Example 2 (below).

Example 1 – Too much adjustment Example 2 – Correct adjustment
 Under-adjustment of the Leveling Cam can cause problems that include ribbon
wrinkling, label tracking, and excessive platen and printhead wear.