The assembly line at Feetz has 100 humming 3-D printers. Their sole purpose is to make shoes.

Each printer is named after a cartoon character: Wonder Woman, Scooby-Doo. Though whimsical, the printers, which cost $5,000 each, are out to upend mass retailing by making every shoe to order, cheaply.

“We’re the technologists coming in to help,” said Lucy Beard, chief executive of the two-year-old Feetz, in San Diego. “I saw 3-D printers in a magazine, and I thought ‘mass customization.’”

Each printer can be reset to make different sizes and takes up to 12 hours to make a pair. The company, which recently started selling its shoes, has only 15 employees.

But Ms. Beard, 38, a former actuary, envisions a day when shoes will be printed in under an hour. With limited labor and shipping costs to pay and no back inventory, Feetz has a 50 percent profit margin on every pair, she added.