Injection Molding Machines
“Injection molding machines consist of a material hopper, an injection ram or screw-type plunger, and a heating unit. They are also known as presses, they hold the molds in which the components are shaped. Presses are rated by tonnage, which expresses the amount of clamping force that the machine can exert. This force keeps the mold closed during the injection process. Tonnage can vary from less than 5 tons to 6000 tons, with the higher figures used in comparatively few manufacturing operations. The total clamp force needed is determined by the projected area of the part being molded. This projected area is multiplied by a clamp force of from 2 to 8 tons for each square inch of the projected areas. As a rule of thumb, 4 or 5 tons/in2 can be used for most products. If the plastic material is very stiff, it will require more injection pressure to fill the mold, thus more clamp tonnage to hold the mold closed. The required force can also be determined by the material used and the size of the part, larger parts require higher clamping force.” (Wikipedia, Injection Molding, 1/27/2011)
“Injection molding machines are known in which a reciprocating screw equipped with a back flow valve implements the plastification of the plastic granulate and generates the injection pressure. Other approaches involve an operational division between a screw plasticizing unit, on the one hand, and a plunger-type injection unit, on the other hand. Constructions of this type have the advantage that a screw plasticizing unit can operate at optimum plasticizing capacities. Moreover, the use of several plunger-type injection units, fed from a screw plasticizing unit, permits the screw plasticizing unit to be continuously operated because melt can be fed alternatingly to the various, normally two, plunger-type injection units.”
“A screw plasticizing unit in combination with plunger-type injection units can also be used as compounder for mixing varied components. As the plasticizing screw is not moved back and forth, solid and liquid additives can always be fed at the same location relative to the screw. The same is true, when producing foamed products, because foaming agent can also be added always at the same spot. The continuous operation prevents an undesired pressure drop of the foaming agent, as has been-experienced with injection molding machines withreciprocating screws during shutdown period.”
(Zimmet, US Patent 7,815,838; 10/19/2010)
Electrically Driven Injection Molding Machines
Injection Molding
Injection Molding Manifolds
Shut-Off Valves
Processing
Recent US Patents
3/8/2011
7,901,127
Drive for a machine for synthetic material plasticization and injection
Knauff and Schunk of Siemans, Germany, developed an injection molding machine consisting of a main drive drivable in a first and a second direction of rotation and a hollow shaft rotatable about an axis of rotation. (RDC 9/16/2011)
3/1/2011
7,896,637
Injection molding machine
Yamaura and Unno of Nissei Plastic Industrial, Japan,developed an injection molding machine that is equipped with hydraulic pumps which control discharge flow rates by variably controlling the number of revolutions of a drive motor. The injection molding machine is equipped with a hydraulic drive member having the multiple hydraulic pumps and a hydraulic oil supply circuit which jointly or independently supply the hydraulic oil to be discharged from the multiple hydraulic pumps to a selected hydraulic actuator out of the multiple hydraulic actuators. (RDC 9/10/2011)
12/28/2010
7,857,614
Continuous molding machine
Di Simone of Husky Injection Molding System, Canada, has developed a continuous molding machine consisting of a frame, a mold structure non-movably connected to the frame, and a cam movably linked to both the frame and to the mold structure for driving the mold structure including a mold stroke function, a molded article ejection function, an melt handling function, a valve gate function, and a mold clamping function. (RDC 6/29/2011)
10/19/2010
7,815,838
Method of operating an injection molding machine with continuously operating plasticizing unit
Zimmet of KraussMaffei Technologies, Germany has developed an injection molding machine with an injection plunger for pushing melt from an injection space anteriorly of an injection plunger into an injection mold, a plasticizing screw of an extruder is continuously operated to continuously feed melt through a melt channel into the injection space. A passage through the melt channel is closed to allow backup of melt backwards into the extruder, and the injection plunger is moved forward to inject a shot amount from the injection space into the injection mold.(RDC 1/24/2011)
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