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A Professional Manual: Polymer Extrusion From Start To Finish!

by Elijah Mort

I was at a point in my life where I wanted to see what it was like to do something I'd never done before. I wanted to see how things so simple that I see in everyday use were made, and who it was that made them! We buy our products from name brand stores, but do we ever stop to ask ourselves how the product itself came to be? Nobody really stops to think of what goes into making something as simple as a roll of tape. When I started asking these questions, I was introduced to injection molding. The name itself was fun to say, and I went to a couple of companies to do some hands-on research on the subject. To my surprise, I learned way more than I thought I would, and I was actually catching on really fast!

The core of the entire process is, of course, the material. The very first thing you'll need is a material with the title of thermoplastic. The form of thermoplastic that you'll need is that of small beads. As in many professions, there is much plastic extrusion jargon to learn. For example, this thermoplastic in the shape of small beads is most commonly referred to as "resin."

Once you've acquired this "resin", you'll need to fill up a hopper with it. A hopper is sort of like a truck, which gravity feeds the thermoplastic into a barrel attached to the extruder. Also, in order to make your injection molded parts more desirable, different colorants can be added. This is to be done before putting the thermoplastic "resin" into the hopper.

Once a specialist operates the hopper, successfully feeding the resin into the barrel, it meets what is called a "feedthroat." All a feedthroat essentially is, is an opening at the rear bottom of the barrel. The resin travels through the feedthroat and it meets an industrial-sized screw. The screw pushes the resin at generally 120 rpm back into the barrel, which then begins to gradually heat itself.

Your typical industrial plastic extruder will come complete with cooling fans. The cooling fans aid in keeping the temperature below the degree that the specialists input at the start of the process. Also, the industrial screw is quite a complex piece of machinery. There are five possible zones in the screw, but since the jargon isn't international, you will sometimes a couple of different names for them.

Once the plastic resin is melted completely into a liquid, the next step is to drain it of imperfections and contaminants. The way this is done is the molten thermoplastic travels down the screw and through a series of screens to be filtered. These screens are secured in place by a piece of machinery with the title of a "breaker plate." All a breaker plate really looks like is a thick, much bigger hockey puck that had 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.

At this point in the plastic extrusion procedure, a specialist must watch to make sure the molten thermoplastic flow is steady. Even the littlest bit of unsteadiness can accidentally cause flaws in the plastic! If these stresses are too visible, they may completely ruin a particular piece of plastic. No company wants a waste, so making sure to pay attention to this is vital.

Finally, we move on from the machine to the cooling process. This is where specialists from the plastic extrusion companies really come in handy. Storm Panels can be really difficult to cool down, as plastic is an excellent thermal insulator. Polymer Injection Molding is quite an interesting process, it's amazing how many things can come from it!

Published November 21st, 2010

Filed in Business


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