Removal from the Mold

As soon as the set cooling time in the injection molding cycle has expired-in other words, once the injection-molded article has solidifed within the mold-the mold opens in the parting plane. The mold halves separate far enough to allow the article to be ejected. 

Ejection is usually carried out by guided metal pins - ejectors - that are part of the mold. These ejectors push the molding off the cavity surfaces. Here it is important to ensure, that the article is not damaged by the ejector pins. 

Moldings of high quality and sensitivity (e.g. bumpers), as well as parts subjected to further processing immediately after removal, must not be allowed to just drop into a box or onto a conveyor belt. They should be removed from the mold by a handling device. 

All of these criteria apply also to the Compact Disks. CDs cannot be allowed to drop onto one another, because this would damage their highly sensitive surfaces. CDs are coated (sputtered) and lacquered in subsequent operations. A handling device is used to place the CDs into the machines used for these operations. 

In most cases the article is removed mechanically by ejector pins, integrated into the mold. With sensitive or soft moldings, the pins are often replaced by air ejectors. Air ejectors separate and push the molding off the mold surface by compressed air. 

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Thermoforming. Thermoforming is the most common method of fabricating sheet into three-dimensional packaging. In conventional thermoforming, the sheet is heated to its softening point or just below the melting temperature. The softened plastic is forced by differential air pressure into an open-top mold to assume the shape of the female mold. The mold is chilled and the plastic sheet solidifies and is then removed from the mold. 

Reiaforced plastics may also iaclude fillers (qv), which are iaexpeasive materials such as calcium carboaate used to displace resia and reduce cost curing agents (catalysts), promoters, inhibitors, and accelerators, which affect thermosetting resia cure colorants release agents (qv) to faciUtate removal from the mold and other additives which can impart a wide variety of properties to the finished part, such as fire resistance, electrical conductivity, static dissipation, and ultraviolet resistance. 

The soft-mud process is used to make handmade btick. Mote water is added to the clay to make a thinner paste, typicaHy about 20 to 30% by weight of water. The resulting slurry is packed into molds that have a sand or water coating on them that acts as a release agent. The wet brick shapes ate removed from the molds when they have set up enough to handle and ate then stacked for drying and burning. 

Many modifiers and additives have been described for use with nylon composites, but generally a small amount, 0.05—1 wt %, of a lubricity aid, such as sodium or 2inc stearate (4) is added to enhance both resin flow during processing and removal from the mold after consoHdation. 

Angle of clearance between the molded article and mold, allowing removal from the mold. 

Fig. 8-63 After removal from the mold, work continued on the ship to which the super structure was added.

I, After the part is removed from the mold, it is often necessary to perform additional post-lit processing functions on the product. For example, holes may need to be drilled or protrusions cut off to create an opening into a storage tank. Some parts have very thin regions from which the polymer has to be removed, for example the eye socket of a plasticized polyvinyl chloride doll head. Sometimes multiple parts need to be affixed to one another using adhesives or [It. solvent adherents. 

The 6 mm cylindrical segments can then be embedded by placing them into an appropriate-sized embedding mold, on top of which is placed a prewarmed plastic embedding cassette. Molten wax is then added to the mold and cassette before transferring onto ice and allowed to set. The complete blocks are removed from the mold when sufficiently solidified. 

The various morphological variants available in bead form can be repHcated in thin films ( 2 cmx8cmx50-100 pm) produced simply by photo-initiated free radical polymerization of comonomer mixtures introduced by capillary action into an appropriate mold formed with microscope sHdes [48]. With appropriate choice of comonomers, and porogen in the case of macroporous films, reasonably mechanically robust self-supporting films can be removed from the mold for further exploitation (Fig. 1.9). 

After subsidence of temperature following initial exotherm, the fiber bundle with the partially cured pot is removed from the mold for fiber end exposure. The mechanical integrity of the potted end in this green state must be sufficiently great to permit careful handling and insertion in the machine necessary for fiber-epoxy excision. 

The mold and sample were placed in the press also preheated to 185°C and the cure cycle started immediately. Press temperature and pressure were microprocessor-controlled for consistent cure cycles. The cure cycle consisted of an initial 30 minute hold at 185°C with 1300 psi of pressure followed by 45 minutes at 221°C with 850 psi pressure and finally 15 minutes at 260°C with 300 psi pressure. The mold was removed from the press immediately following the completion of the final step and the sample removed from the mold while still hot. 

Cured BCB/BMI specimens are a transparent golden brown in color, similar to what was seen for the BCB oligomer. Once the specimens have been removed from the mold they are postcured for 1 hour at 300 C in nitrogen resulting in an extent-of-cure of greater than 95X. 

In cold molding, the compound is compacted in a mold at around room temperature. The compressing operation is similar to that employed in the production of KBr pellets from powdered KBr. The compound generally contains a lot of filler and binder. The compacted material is removed from the mold and placed in an oven where it becomes cross-linked. Ceramic materials are often produced using cold molding. 

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