Vacuum mold cooling

Efficient mold cooling also depends on accurate venting. Air trapped between the mold cavity and the plastic will significantly slow down cooling and also could cause problems with the part. Certain molds incorporate vacuum lines to ensure proper contact. 

The block size is about 1 x 1.2 m with a length of 4 to 8 m. The block mold is mostly nonadjustable. There are systems with one or two adjustable side walls to adjust the size to the end product to be produced. It is common to position the block molds vertically. This saves installation space, and the foamed blocks are mostly transported in standing position and stored in standing position at the temporary storage. After filling the mold, the foam particles are fused with water steam and are then stabilized with a vacuum. However, cooling with water is not done. 

Sheet is drawn over mold with additional force, other than provided by the vacuum, until cooled. 

Sufficient time must be allowed to cool the molded part under pressure to 90°C to prevent vacuum voids and distortion. 

Eig. 3. Coasumable-electrode melting ia the vacuum-arc furnace (13). A, arc B, buttoa E, electrode I, iagot L, Hd M, water-cooled mold and P, pool of... 

Blow Molding. Blow mol ding is a multistep fabrication process for manufacturing hoUow symmetrical objects. The granules are melted and a parison is obtained by extmsion or by injection mol ding. The parison is then enclosed by the mold, and pressure or vacuum is appHed to force the material to assume the contour of the mold. After sufficient cooling, the object is ejected. 

During the thermoforming process (see Fig. 12), the sheet is heated above the glass transition temperature and below the melting point of the crystalline phase [35]. Afterwards, the hot sheet is formed into a chilled mold using vacuum, pressure and/or mechanical force. After a cooling step, the thermoformed containers are punched out and ejected. The skeleton (30-70% of the total volume) is recycled in the same application (Fig. 12). 

The neat epoxy resin was prepared by casting. The as-received B-stage material was subjected to degasification at 85 °C inside a vacuum oven. The softened resin was then transferred into a preheated silicon-rubber mold. The curing schedule was 121 °C for 2.0 hours, 177 °C for 2.5 hours, followed by a slow cooling at 0.5 °C per minute to room temperature (23.0 °C). 

In contrast to standard cooling, which keeps the mold temperature at a certain temperature below transition temperature, the surface of the mold is heated up with the help of an inductive heating almost to the melt temperature in order to gain a lower melt viscosity during filling. Compressed air causes problems. So the air in the mold must be evacuated by a vacuum pump. This is necessary to provide complete part filling as well as to prevent the burning of plastic by the compressed, hot air at the bottom of the cavity. 

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