Small injection presses lead the way to "lights-out" automation.

Point Plastics, a medical molder in Petaluma, Calif., has reaped many benefits from its exclusive use of small injection machines - most notably, "lights out" factory automation and low tool-maintenance costs.

Foregoing fancy controllers and computer networks, the company has rigged its nearly 300 small injection machines with simple timers and automatic parts-handling equipment for a molding operation that really goes "lights out" at night. All the company's machines now run unsupervised on the late shifts. "When we go home at night, the plant runs itself," says CEO Philip Stolp.

How did the use of small presses help Point automate? Stolp explains that the small machines all have basic manual controls, which lend themselves to timer-based automation. What's more, the down-to-earth controllers ease troubleshooting and repair tasks: Point's technicians can quickly and inexpensively swap a new controller for an old one when problems arise.

LOTS OF SMALL MACHINES

In all, Point Plastics molds about 60 products, 30 of them being pipette tips for laboratory use. Most of the parts are thin-wall jobs - down to 0.008 in. on some tips. Ninety percent of the moldings are in polypropylene.

The company's arsenal of machines includes 53 Arburg Allrounder K Series machines with old-style manual controls. Forty-nine of these are 28-ton models, but Point also runs a few larger presses - up to 77-tons - for some of its bigger parts, such as a rack for pipette tips.

In addition to these commercial machines, Point has built 240 smaller machines of its own design. These 2-ton injection machines are specifically geared to pipette production in two-cavity molds. "Pipettes are all stroke with no projected area, so we built our own machines to accommodate that application," Stolp says.

TOOLING BENEFITS, TOO

Embracing a small-machine concept has also strengthened Point's tooling management operations. Stolp points out that the small-machine concept lets you tool up cost effectively for small-volume jobs. But he adds that the small machines are the best way to address big-volume applications too. For example, one of Point's pipette tips runs in 60 different two-cavity tools at any given time. "I still wouldn't go with big multi-cavity tool on these jobs," says Stolp.

Another big advantage of the small machine/low cavitation choice has been low mold-maintenance costs achieved by reducing wear and tear on tools. "My competitors would cry if they knew what I spend on mold maintenance," Stolp says. Consider the pipette rack mold: This single-cavity tool has run nearly every day for fifteen years with no need for rebuilding, he reports. In fact, this $20-million-dollar/yr molding business with 293 machines running three shifts employs a single full-time toolmaker for all mold maintenance.

"The key to our success has been sizing the press to the project and keeping things as simple as possible," says Stolp.