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Most
of us have worked with a mold at some time such as playing with Play-doh
as a kid, working with plaster of Paris in an art class or making
Jell-O. That experience might make it easier to visualize how NUMMI’s
Plastics department manufactures instrument panels, bumpers and other
plastic parts for the Vibe, Corolla and Tacoma, but it doesn’t
begin to compare with the actual process.
For starters, the molds used in Plastics weigh 20 to 30 tons. And
if you thought buying a home in Silicon Valley was expensive, try
taking out a mortgage on a mold. They cost anywhere from $700,000
to $1.2 million!
With so much money invested in our Plastics mold inventory, NUMMI
can’t afford to keep spares around. Minor nicks can be repaired
by the Plastics Maintenance team, but more serious damage means shipping
the mold back East, which could shut down the line once inventory
(usually three to eight hours worth) ran out.
To begin the molding process, small plastic cylinder-shaped pellets
are heated until they just begin to melt. Scrapped parts and excess
pieces of plastic are also recycled by shredding them and adding them
to the mix. This goo is then injected into, for example, a Corolla
bumper mold.
A mold is 4x8x4 feet and split in halves that are forced together
by a press. The press exerts about 3,000 tons of pressure on the mold.
When you consider tire pressure is typically 32 pounds per square
inch, and think about the force released when you blow a tire, you
can see why molds and presses are as heavy duty – and costly
– as they are.
Once the heated material has been forced into the mold, cold water
running through cooling lines lowers the temperature until the plastic
solidifies.
The halves of the mold are then separated and the bumper is gently
removed. At this stage, it’s still warm and easily scratched.
The piece is loaded onto conveyors, prepped, and sent over to the
paint side of Plastics called Fascia. About 15 percent will be shipped
- unpainted - to service parts distributors to replace damaged bumpers
on Corollas already on the road.
In Fascia, the bumpers are placed on conveyors. They go through a
wash, then they are dried, masked, and transported into a paint booth.
Robots prime the bumper in one booth, then paint them and apply a
clear coat in another.
The bumpers exit the booth and pass through a 250-degree oven for
25 minutes to dry. Then they’re inspected for problems. Flaws
are repaired if possible. If the damage is too extensive, the piece
is scrapped. Next, logos and trim pieces are added, then the painted
bumper is conveyed to the line where it’s installed on a newly
assembled Corolla.
A few years ago, NUMMI could make a bumper every 90 seconds, but we’ve
cut that time to 48 seconds. In fact, we have some of the fastest
cycle times of all Toyota plants manufacturing similar size parts.
Mold is one of the few departments at NUMMI that operates three shifts
a day. Of the many team members in Plastics, nearly half work in Mold,
and the rest in Fascia, Maintenance, Engineering and Projects. |
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