The reciprocating screw has been the gold standard for melt plastication since the 1950-60s when it was adopted by a few forward-thinking injection molders like Bob Cervenka at Phillips Plastics in Hudson, Wisconsin.
Sixty years is a long time when you think how fast other technology–ranging from genomics to digital media–has developed just in the past 10 years.
Herwig Juster, a processing specialist (and clearly a thinker), asks in a recent post on LinkedIn: “Reciprocating screws: successful since ever, but what will happen in the future?”
He offers some ideas, but he doesn’t go all Star Trek on us.
Here is a brief summary of his thoughts:
- Initially there will be improvements in screws through better understanding of the distribution of melt temperatures in the barrel. A university research group is proposing use of an online ultrasonic sensor-based system that determines the axial profile of the melt temperature in the screw chamber and channels via reflection. “Consequently, though the principle of the reciprocating screw will remain, new screw designs may finally arise in a near future to meet the requirements of processing ultra and high performance plastics, such as PI, PEEKs, PAEKs, etc.”
- New approaches such as ultrasonic injection molding hold promise in the micro world. “Overall, this is a totally new concept of injection molding, which requires new strategies for process control as well. Let’s see how this technology develops, but it looks certainly promising in businesses, such as healthcare and watch manufacturing for instance.”
- Another idea is inverse screw molding. The melting benefits of a screw are coupled with the precision of injection with a plunger, says Juster. Also, screw flights for conveying the into melt are built into the cylinder.
OK, these are pretty much existing technologies. What does come after the reciprocating screw for mainsteam injection molding? In the 1950s, newspapers were produced with behemoth, man-operated machines that converted bars of lead into rows of letters that were assembled by the hundreds into blocks that became newspaper pages. Today, newspapers are produced digitally and are virtual anachronisms themselves.
I’m giving Juster, who earned his engineering degree in 2012 from an Austrian university, a lot of credit for putting some thought into this interesting question. I’m also giving him props for giving William Willerts credit for inventing the reciprocating screw. He may or may not be aware that there was controversy back in the day about whether the reciprocating screw was an American or German invention. There was also controversy about whether the technology was adopted faster in the U.S. or Germany.
All I know is what the late, great John Reib, founder of Conair, once told me. He had been impressed with the reciprocating screw machines he had seen at a K Fair in the late 1950s. Some others in the American industry belittled the trend as a passing fad. And that was the case with Bob Cervenka’s competitors who in 1964 were still wedded to the plunger-type machines.
Change will be coming, but maybe it will just be evolutionary.