Mold types Displacement

Z molding compound (ZMC) was first prepared in France in 1979. This compound needs a special type of injection machine—a combination of plunger and screw—and was indigenously developed by Billion in France. The machine uses a screw to homogenize and measure the shot. The injection is made like a plunger by the displacement of the screw and inner barrel inside the main barrel. Compared to SMC, ZMC parts have lower mechanical properties, but higher performance when compared to conventional injection molded BMC. 

The most common special feature of the mold is the quick change volume control insert. Rigid volume control is necessary for certain products, such as dairy containers. Here HDPE is used (for many excellent reasons), and the container slowly shrinks and changes in size for many hours after molding. Because of production volume control requirements, some dairies must fill containers molded half an hour before fill and then switch to filling containers molded several days previously. Volume-control inserts that displace the difference in volume between the two types are added to the mold, usually as a disc in the side wall, to ensure that the volume and fill levels are the same in both containers at the time of filling. The device works because HDPE shrinkage is reduced virtually to zero for the life of the container when filled with milk or juice and stored at cold temperatures. 

Presently, ram extruders are used in relatively small shot size molding machines and certain specialty operations where use is made of the positive displacement characteristics and the outstanding pressure generation capability. There are basically two types of ram extruders single ram extruders and multi ram extruders. 

Early resin materials used in mold compound formulations were sihcones, phenolic resins, and bisphenol-A or bisphenol-F epoxies. Because of shortcomings in performance, these materials have been displaced by epoxy phenol or cresol novalac resins (ECN resins) and by the biphenyl- and tris(triphenylmethane)-type epoxies (70) (Fig. 20). The high cross-link density of ECN-based materials results in low moisture absorption rate and higher thermal stabihty than... 

As explained above, in UV-NIL, resist displacement is promoted both by the applied imprinting force and by the capillary forces. The balance between the two phenomena is not clear and depends strongly on process conditions (mold treatment, wafer treatment, resist viscosity and surface energy and resist coating type) in UV-NIL the effect of capillarity is invariably increased. Nevertheless, the squeeze flow of a supposedly perfectly viscous resist can be described quite simply to a first approximation by Stefan s law [26]. For a line, the imprinting time can be written as [27] ... 

This type of process uses compressed air to displace and form melted material into shapes. The concept is generally described as blow molding. The application of the strategy works well in the production of hollow shapes, and works in much the same way as blowing up a balloon. Air pressure can be applied over a wide surface area and can be useful in making very large parts. 

The three-dimensional displacements inherent to NIL require resist materials that easily deform under an applied pressure and/or elevated temperature. These resists must have a low viscosity during imprinting, a Young s modulus less than that of the mold, and a low sheer modulus. It should also be mentioned that the resist material should have excellent adhesion to the substrate, provide high-quality, uniform film thickness through deposition via spin-coating, and have sufficient thermal and mechanical properties for subsequent processes. When determining the type of NIL resist to use, one should consider the critical dimensions of the pattern, pattern density, release properties from the mold, required imprint temperature and pressure, etch selectivity for subsequent pattern transfer, and route to eventual removal by dissolution or other processes. 

For each type of specimen, five samples are made at the same molding conditions, and tensile tests are preformed at displacement rate of 25 mm/min based on ASTM D638 standard 8. Average of ultimate tensile strengths for those specimens is analyzed to obtain experiment tensile strength data. 

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