Compression molds designs

By contrast with ICM, a compression mold design is used where male plug fits into a female cavity rather than the usual flat surface parting line mold halves for IM (Fig. 8-27). The melt is injected into the cavity as a short shot thereby not filling the cavity. The melt in the cavity is literally stress-free it is literally poured into the cavity. Prior to receiving melt, the mold is slightly opened so that a closed cavity exists the male and female parts... 

A knowledge of processing methods will be useful to the designer to help determine what tolerances can be obtained. With such high-pressure methods as injection and compression molding of 2,000 to 30,000 psi... 

Sample Preparation. Samples for mechanical studies were made by compression molding the polymers at 150°C between Teflon sheets for 15 minutes followed by rapid quenching to room temperature in air. These will be referred to as PQ (press-quenched or simply quenched) samples. The thickness of the PQ samples was around 10 mils (0.25 mm). The thermal history of all of the PQ samples (HBIB, HIBI, and LDPE) were essentially the same. They were used within one week after they were pressed. Samples for morphology, SALS and SEM studies were prepared from toluene solutions. These films were cast on a Teflon sheet at 80 C from a 1% (by weight) solution in toluene. These films were about 5 mils in thickness. When the polymer films had solidified (after 5 hrs), they were stored in a vacuum oven at 80°C for two days to remove residual solvent. These samples will be designated by TOL (solution cast from toluene). 

The largest volume of fluoroelastomers (about 60% of total) is processed by compression molding. A blank (preform) is placed into a preheated mold, compressed, and cured at the appropriate temperature (see above) for a time established empirically. A good estimate for the curing time in the mold is the value of Co from the measurements by oscillating disk rheometer. In the mold design, it is necessary... 

Different processes have been developed with a few in use. Their designs usually start with an extruded thermoplastic sheet. Circular blanks cut from the sheet are compression molded into the desired preliminary shape. During the compression action, the blank can be simultaneously stretched, or being thermoplastic can be stretched after compression molding. They generate no trim scrap when formed... 

The final product may take any one of a vast multitude of final forms. These include, but are not limited to, construction materials, toys, automotive parts, kitchen aids, industrial parts, sports and recreational equipment, containers of all sizes and description, and an unlimited variety of packaging products for foods, drugs, cosmetics, and other consumer products. The processes that are used to produce or mold or fabricate the final products are also varied and depend on the design and purpose of the product. Some of these processes include extrusion, compression molding, roto-molding, blow molding, sheeting, and films. 

Now, let US consider a WPC deck. In a simple case, it is assembled with boards, made of a composite material. The boards can be solid or hollow, or of an opened, engineered design (see Figs. 1.1-1.25), which can be extruded (in a common case) or compression molded. Typically, but not always, WPC boards have a width of 5V2 in. (139.7 mm), height (thickness) of P/4, 1.00, 15/16, or 13/16 in. (31.75-20.64 mm), and—for standard boards—12, 16, or 20 ft. in length. The board s surface can be smooth (unbrushed), brushed, embossed, or having an exotic pattern, such as streaks, simulated wood texture, among others. 

---