Plastic extrusion is an elaborate process, and the number of steps that go into it might overwhelm a newcomer. If you ask a random passerby on the street what their thoughts on plastic profile extrusion are, you’re probably going to get a confused response. This is fascinating to me, because literally so many things that we use every day could not have been created without plastic extrusion! In the past few months, I’ve really begun to dive into this incredible process. My goal has been to learn everything I possibly can on it, and to get others interested as well. So far, so good! You wouldn’t believe some of the things that I’ve learned.
The first thing you need in the extrusion of plastics is a raw material by the name of thermoplastic. It’s important that you get this material in the form of small beads. In my on-site research of plastic extrusion, I have learned several different words from the industry’s lingo! The raw thermoplastic in this form is popularly referred to as “resin.”
The next step is getting the resin into what is really the beginning of the machinery process, the barrel. The best and most widely used way of going about this is using a hopper. A hopper is special in that it gravity feeds the thermoplastic resin needed to make injection molded parts. In order to make a more attractive plastic product, before placing the resin in the hopper, add colorants to jazz things up!
If the previous step was successfully completed, then the thermoplastic resin will run into something referred to as a “feedthroat.” The feedthroat is usually found at the bottom rear of the barrel. The thermoplastic resin then runs into an incredibly huge industrial-sized screw. This screw is on average, pushing the resin at 120 rpm back into the barrel. At this point, the barrel begins to slowly heat itself to a degree that the specialist has already input.
The screw is a really amazing and complex part of the machinery. There are FIVE, not four but FIVE possible zones in a thermoplastic screw. And since the industry can be so diverse and widespread, the names for these different zones can differ depending on where you go. Where I studied, they were referred to as : feed zone, melting zone, metering zone, decompression zone, second metering zone.
The now completely molten plastic travels down the length of the screw. At this point in the process, the plastic has to travel through several compact screens. This is for the sole purpose of clearing up anything that may have contaminated it. Holding up the screens, is a device called a “breaker plate.” This is shaped much like a hockey puck, with holes drilled into it.
A truly grand finale for this plastic extrusion process (except of course, the cooling) is what happens next. The liquid plastic travels from the screens to the die. The die is such an important part of the machinery, mostly due to the fact that it gives the plastic it’s shape. Relying solely on the company and what the final product will turn out to be, the die shapes the plastic.
Now, even though this is an interesting act in this plastic extrusion play, this is the part where a specialist must be especially careful. If the stream of liquid plastic becomes too unsteady, you can find yourself out of luck! The plastic may come out with stresses and weaknesses on it. If they’re bad enough, a specialist may have to throw them out! After coming all this way!
After a somewhat difficult cooling process (plastics are incredible thermal insulators and not the easiest thing to cool quickly), plastic extrusion is complete. polymer manufacturer everywhere make injection molded parts with the help of plastic extrusion everyday. Everything from pipe/tubing, window frames, fence, and adhesive tape comes from this process!
– Elijah Mort