When marking or engraving insulated tumblers and glassware, if there is a taper, the graphics in the drawing need to be adjusted to avoid looking compressed or elongated when engraved.
The same goes for a sphere (i.e. engraving an ornament), which has a continuous taper in all directions.
Why does this happen? When the workpiece on the rotary device has a circumference on the turning wheels, that differs from the circumference where the graphic will be engraved. The area where the graphic goes travels a different distance over a given time (thus at a different speed) than the part on the turning wheels. If the circumference is larger where the graphic goes, the engraved graphic appears stretched; if smaller, it appears compressed.
One way this can be accommodated for is in the drawing, by either compressing or stretching the vertical aspect only of the drawing. To do this, divide the circumference at the turning wheels by the circumference where the graphic goes and multiply that by the vertical aspect only of the drawing, before sending it to the laser. (I use circumference because it’s easy to measure on most items with a cloth tape measure. Diameter will also work in the same formula).