You land in China, late for a business meeting. Your cell phone goes off. On the other end, it's not your boss, but an injection press that says: "We have started molding your parts now." The message is sent directly from the lead press at your custom molding plant in Atlanta, a lights-out operation. You forward the information to a worried colleague in Sao Paulo, Brazil. Eight days later, when you're back home in New Jersey, the machine e-mails that the job is finished.
This type of scenario could happen in 20 years. Or next year.
Regardless of when, experts say that, in the early part of the 21st century, an information revolution will rock the world of injection molding machines more so than any mechanical improvement, with the possible exception of the all-electric machine.
Electric presses and several other technological trends already are on the scene, including gas-assisted injection molding, micromolding, metal injection molding and the tiny-bubbles MuCell process.
Turn of the screw
Speaking of mechanical issues, here's a question for the millennium: Will that 50-year-old bedrock, the reciprocating screw, be around decades from now, still melting and mixing plastic, then pumping it onto molds? Yes, say the gurus. They think the screw is safe from more-exotic concepts such as particle beams and microwaves, ultrasonics and magnetic fields.
"The screw at the moment is here to stay. It's stood the test of time. There have been many attempts to change it, but nobody's succeeded on a commercial basis," said Irvin Rubin, a New Yorker who wrote the book on the subject. First published in 1972, Rubin's Injection Molding, Theory and Practice is still used today.
In the history of plastics, two machinery innovations stand out as major transformations: the screw's displacement of the old plunger machines in the 1950s and 1960s, and the programmable logic controller in the late 1970s and early 1980s.
Plunger machines were still being used in 1960, when Donald Paulson got into the business.
"If we're talking specifically about melting plastic, the reciprocating screw is the most efficient way ever found — yet," said Paulson, president of Paulson Training Programs Inc. in Chester, Conn.
William Willert designed the reciprocating-screw injection unit in 1952, and secured the first U.S. patent in 1956. Reed-Prentice built the first reciprocating-screw press in 1953.
Rubin, a chemist who began working at plastics factories in 1940, said the plunger machine just wasn't very good, despite the use of heater bands and the Gastrow torpedo. Because of their limited melting capacity, the biggest shot size a plunger press could run was about 24 ounces, he said. The only way to run more material was to use a fatter barrel, but then the material in the core had a tendency to freeze up, unmelted.
The screw opened things up. Large-part molding. Thin-wall parts. Difficult-to-run materials such as polycarbonate, rigid vinyl, nylon and acetal.
"The screw was always a good plasticizer because it mixed the material very well and made it a very good, homogenized material," Rubin said.
Soon, processors began scrapping their plungers, or converting them to screw machines.
Glenn Beall, a product designer who teaches processing seminars, called the screw "revolutionary, because ... better quality melt allowed us to mold much better quality parts, especially the thin-wall parts."
In the decades since, there have been advances in screw design, nonreturn valves and the metallurgy of the screw and barrel. But maybe some things don't have to change. The screw's benefits are still the same — it melts lots of material, very fast.
"The screw is substantially the same as it always was. They've made little improvements on it, but it's been the same for 50 years," said Beall, who owns Glenn Beall Plastics Ltd. in Libertyville, Ill. His plastics career began in 1957, right when the reciprocating-screw craze hit. Beall worked at General Electric Co. and Abbott Laboratories before starting his own design firm.
Here's how the reciprocating screw works: After each shot, the screw begins turning, pushing the plastic melt along to the front of the screw. As the melt builds up, it forces the screw back. The screw then stops turning and acts as a plunger to push the melt into the mold. The screw begins to turn again to build up the next shot.
Rubin said Willert's biggest achievement was developing a way to pull the screw back to reduce pressure during recovery of the next shot. This invention, which Rubin calls "simple but incredibly ingenious," prevented liquid plastic from spewing out of the nozzle — a common occurrence on early machines that used traditional extruder-type screws.
"His patent made the use of the screw possible in injection molding," Rubin said.
Willert, who is retired and lives in New Jersey, did not want to comment for this story.
Barr Klaus, who works on new technologies for Milacron Inc., said the screw has endured because it does melting, mixing and pumping at a reasonable cost. Klaus said Milacron has toyed with some exotic technologies, including microwaves.
"But whenever you get two or three uses out of one device, it becomes pretty hard to get rid of it. It probably, in my book, has real good job security," said Klaus, technical director of Milacron's Elektron Technologies unit in Cincinnati.
Ironically, Elektron went back to the plunger for its new, all-electric injection molding presses with large shot sizes. According to Klaus, it's an example of new technology casting a new light on old technology. Hydraulics can push large-diameter screws easily, but very large electric components, such as ball or roller screws, are still too expensive, he said.
The solution is a two-stage injection unit, with an extruder that charges a shooting pot, and a plunger to fill the mold.
All-electric presses are the next big thing. Nearly every company offers one. Advocates say they run quieter, cleaner and with more precision, and use less energy than hydraulic machines.
Klaus predicts that by 2005, all-electric presses will capture 70 percent of the market for presses in clamping forces from 80-1,500 tons.
Glenn Beall also is bullish on electric presses. Electric machines swept through the machine tool industry. "They're sweeping through medical and electronics right now, and they'll just spread out and grow from that," he said.
While the screw does a good job of melting the plastic, several industry pundits think new ways to cool back down again will be the key to cycle-time reductions in the near future.
"Cooling is the area that probably has the greatest potential for improvement," said Donald Paulson. "In molding, you can melt more plastic than you can cool."
Although lots of work already has been done, the way to cool a part has stayed basically the same for years — chilled water runs through the mold and conducts heat out of the part. One way to reduce cooling time is to design thin-walled parts. Other improvements have come from changing the mold itself, such as the growth of beryllium copper alloys and other materials that dissipate heat quickly, and developing new ways to form water channels that follow curves and bends of a part.
"The biggest part of the cycle time is cooling," said Lou Zavala, vice president of marketing and engineering at AEC Inc. in Wood Dale, Ill. AEC and other auxiliary manufacturers are working on new chiller technologies. For example, scroll compressors, which use less energy and have fewer moving parts, are replacing reciprocating-type compressors.
There are a few radical ideas out there. Have you heard about magnetic refrigeration? Some materials heat up when magnetized and cool when removed from the magnetic field, according the U.S. Department of Energy. DOE scientists in Ames, Iowa, are building the first prototype.
But for now, water running through molds remains the standard. As Zavala points out, regardless of how fast a part is cooled, the cooling also has to run evenly across the entire part or it will warp.
Paulson said resin firms could even develop new plastics with quick part-cooling in mind.
"That would be a breakthrough if it could be done," he said.
On the information technology front, the next era of injection molding will be driven by smart machines that can arrange molding schedules, diagnose mechanical problems and communicate worldwide. The hard part will be how to use the huge amounts of information generated.
"The first trend we're seeing is a digital revolution, from the machine level on the floor to a total integration with the rest of the plant and other plants," said Bart Polizotto, product manager of automation systems at Barber-Colman Co. in Loves Park, Ill.
Cellular phones are moving from analog to digital communication, and Polizotto said injection molding machines will follow. Digital sensors and controllers will allow unprecedented amounts of data to flow from the machines to the plantwide system, he said.
Digital will usher in wireless and fiberoptic communication from the machine. "I think in the next two years you'll start seeing wireless communication," Polizotto said.
Evros Psiloyenis, president of FullMetrics Inc., which makes systems for at-the-press monitoring and plantwide management, thinks processors of the future will be fully connected — with customers, suppliers and resin companies.
"A perfect product could be manufactured anywhere in the world, simply by replicating the information to the other sites," he said. "The result will be that you have better supply-chain management, and information would be timely because it would be information that comes off the press, in real time."
FullMetrics, the former Nicollet Process Engineering Inc., is based in Minneapolis.
Future machines also will diagnose their own problems and even order spare parts online. Silos can be rigged to order more resin when the level drops below a certain point.
Psiloyenis said process data could be fed back into simulation programs that help design future parts.
Computers are great, but in some areas Irv Rubin, the New Yorker, is a bit old-fashioned.
"Computer simulations are very well-educated guesses. And the real problem we have is that, like sex, you can't read it from the book. You have to go with hands-on experience in the actual process," he quipped.