In order to make sure the letters don’t look too perfect, Wachs said the robots vary letter shapes, line spacing, the left margin, and the strokes that join letters together.

“We do all this stuff to try to create the most accurate human writing, without falling into that uncanny valley,” Wachs said.

Using robots that can write in nearly three dozen styles of penmanship — some of which carry alliterative names like Enthusiastic Erin and Slanty Steve — the company sends about 20,000 cards a day to customers or, more often, directly to the recipient.