Injection Screws
The heart of the injection molding machine is the screw which melts, plasticates and injects the resin into the mold. R.D. Corneliussen 10/15/2009
"The screw is perhaps the most complicated component in the injection unit, comprising of three basic sections: the feed zone, the compression or transition zone, and the metering zone. The basic principle of screw movement is similar to the “sausage-maker” where the handle is turned and the meat moves forward out of the nozzle. A key factor in optimal operation is that the material must stick to the barrel, since if it sticks to the screw it would just continue to rotate without any forward movement. As the screw turns a melt pool develops on the forward edge of the screw flight as it attempts to move the pellets. As the material moves forward in the injection unit the melt pool becomes larger and the amount of unmelted pellets becomes smaller." T.W. Womer 10/15/2009
Basic Sections of the Screw:
Feed Zone
Compression (Transition) Zone
Metering Zone
Screw Designs
General Purpose
Zero Feed
Barrier Screw
Length/Diameter Ratio (L/D)
Ratio of overall length /nominal diameter
Compression Ratio
Amount of work applied to polymer
Feed depth /metering depth
Volumetric compression ratio
Plasticating Rate
the instantaneous throughput rate capacity of the screw that is in the injection unit at that given time
Injection Rate
“rate at which the resin is injected into the mold by means of the forward movement of the screw inside of the barrel”
Recent US Patents
To go to the text version of the patent, click on US Patent Number Search and enter the patent number in the search box.
3/16/2010
7,677,875
Injection molding machine for controlling measurement of an in-line screw.