Rotary molding

Fig. 14.18 Schematic of the three-position injection blow-molding rotary machine. The third position is easily accessible for removing the blow-molded article. [Reprinted by permission from Modem Plastics Encyclopedia, Vol. 53, McGraw-Hill, New York, 1976-1977.]...

Two or more molds can be used in a shuttle arrangement, so that one or one set is open for parison extrusion while the others are performing the blowing and cooling cycle. There is also a method of mold rotary movement that results in very high production rates. In such machines,... 

Coinjection basically means that two or more different plastics are laminated together. These plastics could be the same except for color. When different plastics are used, they must be compatible in that they provide proper adhesion (if required), melt at approximately the same temperature, and so on (see Table 7-9). Two or more injection units are required, with each material having its own injection unit. The materials can be injected into specially designed molds— rotary, shuttle table, and the like [12]. 

Conventional extmsion or coextrusion may be performed on vertical or horizontal rotary or shuttle mold configurations. In shuttie blow mol ding the extmder and die are in fixed horizontal and vertical position two or more molds shuttie into and out of position beneath the die. By reciprocating in two planes, the mold may remove a parison and permit the extmder to function continuously. 

Horizontal rotary machines employ multiple molds in a horizontal plane on a rotary turret. As each mold approaches the extmder die exit, it opens to accept the parison and then closes. The parison is then blown into the bottle shape. The extmder must extmde on an intermittent basis or be intermittently withdrawn to provide a parison for each passing mold. 

Vertical rotary molds also employ multiple molds on a turret but rotate in a vertical plane. As each mold reaches the die exit, it grasps the parison and closes. Because of the vertical spacing between molds, intermittent extmder action is not required. Vertical wheels are used commercially for high volume apphcations. 

Fig. 2. Rotary die process of soft gelatin capsules where A represents the drug mix B, the mold wedge C, gelatin ribbons D, die roUs E, capsules and F,...

An alternative approach for injection molding is the use of a rotary table injection machine. This type of machine uses the multistation concept, each station having a single cavity mold generally using a point gating/ injection point as previously mentioned. Consider a rotary table machine with eight stations, station one would be the injection station and station seven would be the unload and load metal insert station. This type of process has been successfully used for different types of lip type rotary shaft seals where more expensive elastomers are used and waste needs to be kept to a minimum. 

Over-molding Over-molding is also called in-mold assembly, two-color rotary, or two-color shuttle. Two materials are molded so that the first molded shot is over-molded by the second molded shot first molded part is positioned so the second material can be molded around, over, sections, or through it. The two materials can be the same or different and they can be molded to bond together or not bond together. If materials... 

Add wood furnish (384 g, moisture content 6.02%) to the bowl of a rotary blade paddle mixer (such as a Kitchen-Aid KSM90) and agitate at the lowest speed setting. Add Mondur 541 (7.39 g, 1.9% w/w, a polymeric diphenylmethane diisocyanate of 31.5% NCO, Bayer) dropwise over a 5-min period using a disposable syringe. Continue blending for an additional 10 min and then transfer the blend to an 8 x 8 x 2 -in. metal form at the bottom of which is a metal plate which fits inside. The resin-coated furnish is evenly spread inside the form and another metal plate is placed on top. All parts of the form and plates are presprayed with mold release. The completed form assembly is placed into a hydraulic press (such as a model PW-22 manufactured by Pasadena Hydraulics) with platens heated at 350°F. The furnish is then pressed between the two form plates to a thickness of j in. Press controls are used to ensure consistency of board thickness. The assembly is heated for 4 min. before demolding the cured wood panel. 

A sample of monomer ( 50 g) was placed in a 100-ml round bottomed flask, which was attached to a rotary evaporator. The flask was heated to 150°C with the aid of an oil bath while stirring under vacuum (0.20 mmHg). The monomer was stirred and heated under vacuum for a period of 45 min to 1 h in order to simultaneously degas and B-stage the monomer. The B-staged monomer was then held under nitrogen and poured into a preheated mold, which consisted of two polished aluminum plates (6 x 6 x 1/2 in.) with a three-sided 1/8-in. thick Teflon spacer between the two plates. The spacer was cut from a 6 x 6 x 1/8 in. 

Rotary kiln incinerators, 13 175-176 Rotary kilns, 15 52-53, 603, 26 611-612 puffing and loss of flame in, 13 182 in thermal waste treatment, 25 833-834 Rotary lobe pumps, 21 73 Rotary molds, 18 50 Rotary regenerative heat exchanger,... 

Weighed amounts of PVC and metallic powders were mixed thoroughly for one-half hour in a rotary blender at room temperature. The mixture was compacted in a cavity mold for 10 minutes at 120°-130°C under a pressure of 10,000 psig. The mold was then allowed to cool under pressure to room temperature, and the cylindrical compact was removed. The dimensions are length 3.5 cm diameter 2 cm. Density measurements indicated that this procedure provided samples of porosity <1.5%. 

To increase the production rate, the casting devices and the molds are grouped into one unit. Linear, vertical rotary, and multi-layer units are the most common.171... 

Figure 4.19. Layout of a unit for centrifugal casting (molding) of tubular blanks 1 - rotary mold 2 - mold rotation rollers 3 - heating chamber 4 - blank 5 - rotary gripper of finished pipe extender 6 - exhaust ventilation.

The selection of optimum conditions for rotary molding requires extensive experimental investigations of the various processing regimes. Recently, another way has been developed, i.e., simulation of the flow of a liquid system polymerized in a rotary (rotating) mold.178... 

HYDRODYNAMIC PHENOMENA DURING MOLDING IN A ROTARY MOLD... 

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