Compression Molding
“Compression molding is a method of molding in which the molding material, generally preheated, is first placed in an open, heated mold cavity. The mold is closed with a top force or plug member, pressure is applied to force the material into contact with all mold areas, while heat and pressure are maintained until the molding material has cured.” (Wikipedia 7/29/2009)
“Three types of molds used are the flash plunger-type, straight plunger-type, and the "landed" plunger-type molds. The flash type mold must have an accurate charge of plastic and produces a horizontal flash (this is excess material that protrudes out of the mold). The straight plunger-type mold allows for some inaccuracy in the charge of plastic and produces a vertical flash. The landed plunger type mold must have an accurate charge of plastic, and no flash in produced." (Wikipedia 7/29/2009)
Composites: Compression molding is a high-volume, high-pressure method suitable for use with complex, high-strength fiberglass reinforcements. Advanced composite thermoplastics can also be compression-molded with unidirectional tapes, woven fabrics, randomly oriented fiber mat,or chopped strand. The advantage of compression molding is its ability to mold large, fairly intricate parts. Also, it is one of the lowest-cost molding methods,compared with such methods as transfer molding and injection molding; moreover,it wastes relatively little material, an advantage inworkingwith expensive compounds. However, compression molding is often subject to poor product consistency and difficulty in controlling flashing, and it is not suitable for some types of parts. Compression molding produces fewer knit lines and less fiber-length degradation than injection molding. Compressionmolding is also suitable for ultra-large basic shape production in sizes beyond the capacity of extrusion techniques. Materials that are typically manufactured through compression molding include polyester fiberglass resin systems (SMC/BMC), polyamide-imide, polyimide, poly(p-phenylene sulfide) (PPS), and many grades of PEEK.
Wikipedia, Compression Molding, 9/21/2010
Recent US Patents
10/4/2011
8,029,721
Method of molding footwear components
Waaati of Nike, Oregon, developed a mold for compression molding footwear components include molds, heating elements, conductor plates, insulating layers and carrier trays. An upper mold assembly is placed into a fixture attached to an upper press platen. A lower mold assembly slides into and out of a fixture attached to a lower press platen. Heating elements within the mold assemblies connect to electrical contacts in the fixtures when the mold assemblies are installed in the fixtures, thereby providing electrical power to the heating elements and heating the molds. A conveyor is positioned to receive a mold assembly from (or transfer a mold assembly to) the lower press platen fixture when the lower platen is in a lowered position. (RDC 10/4/2011)
9/20/2011
8,021,589
Molded article with metal reinforcing and method for its manufacture
Haimoff of Keter Plastic, Israel, developed a composite consisting of a channel-shaped metal reinforcing element with a molded plastic shell. The reinforcing element may include open channels closed by a plastic coating. (RDC 9/23/2011)
9/27/2011
8,025,825
Method of producing a compression-moulded plastic part comprising a neck which is equipped with a dispensing orifice
Gruau and Zakrzewski of Cebal, France, developed a method for compression molding of a plastic part including a neck which is equipped with an orifice, in which a blank is created and compressed. The part is molded with a neck which is equipped with a top wall including a thin area with a notch, the contour of this thin area defining the orifice, and two zones which can withstand the mechanical stress necessary in order to break the top wall at the notch. One of the two zones is intended to transmit the mechanical stress and the other is used as a support. The section of the notch is slightly inclined in relation to the axis of the neck. After molding, mechanical stress is applied to one part of the top wall, other than the thin area, so that the top wall tears at the notch, thereby producing the dispensing orifice. (RDC 9/29/2011)
2/22/2011
7,891,967
Apparatus having a lifting apparatus
Brussel of Schmidt & Heinzmann, Germany,has developed alifting apparatus mounted on a compensation bearing
unit and that is for receiving and/or delivering a polymer melt, and in particular a tacky polymer melt into the press mold of a molding pres. (RDC 8/30/2011)
10/19/2010
7,815,837
Method for compression molding plastic articles
Steele of Graham Packaging, Pennsylvania developed a method for compression molding based on several moveable molds and mold sections. Each mold includes upper and lower mold sections, with at least one of the mold sections being moveable in a non-circular first endless path, and being moveable with respect to the other mold section to form a mold cavity. (RDC 1/24/2011)
10/12/2010
7,811,491
Method for manufacturing optical electronic component
Takase et al of Towa, Japan has developed a method of sealing and molding an optical device with resin using a die including a top piece, a bottom piece, an intermediate piece, and a mold release film covering the bottom of the die. Resin is injected around the device and cured in place. (RDC 1/7/2011)
7,811,488
Method for manufacturing molded article with core
Ozeki et al of Sanwa, Japan have used a rotary compression molding machine to produce a shell/core structure using and central and outer punches with independent sliding motions. (RDC 1/7/2011