How flip-flops are made

Thong sandals go back thousands of years, and a modern pair can come out of a mold that works like a waffle iron.

stations: 6
things upstream: 52
raw sources: 15
steps from the ground: 8

The short version

Modern flip-flops are made by molding or cutting a flat sole from foam rubber or EVA plastic. In one route, pellets are melted and squirted into a hinged metal mold that shapes one shoe at a time. In another, soles are stamped out of sheets. A Y-shaped strap is then pushed through holes and locked from underneath.

Mix the foam compound

Rubber or plastic pellets are mixed with a foaming agent and color, then heated until the batch is a soft, uniform dough. It is rolled into sheets or fed into an injection machine.

Goes in
Synthetic rubber Polyethylene
Form the soles

In the injection route, a machine melts the pellets and squirts them into a hinged metal mold that makes one shoe per fill, and a worker trims the flash. In the sheet route, hydraulic presses mold the foam and a die stamps out foot shapes.
Punch the strap holes

A punch cuts three holes in the sole, one between the toes and one on each side of the foot. The thong and the arms of the strap anchor here.
Cut and print the strap

Straps are cut from soft rubber, PVC or fabric. They are printed with color or logos, and each end is fitted with a plug or a pin.

Goes in
PVC Ink
Lock the strap in

The strap's pins are pushed through the three holes and secured underneath by a cap or a glued insole. The strap then sits snug against the sole.

Goes in
Adhesive
Regrind and pack

Trimmed scrap goes back to be reground and molded again. Pairs are matched and checked, and the flip-flops are bundled for shipping.

End of the lineFlip-flops

Worth repeating

Flip-flops are called thongs in Australia, jandals in New Zealand and plakkies in South Africa.
Thong sandals appear in Egyptian murals dating back to about 4000 BC.
At the Okabashi factory in Georgia, a pair of flip-flops takes about an hour from start to finish.