Rotational molding product examples

What types of products are produced by rotational molding Why Give three examples,... 

Specialized training is an absolute requirement for technical service personnel. A typical example is a person involved in supporting a polymer for which the use is the manufacture of rotationally molded consumer products. The technical service person is expected to be reasonably familiar with topics such as polymer rheology evaluations, gel-permeation chromatography, rotational molding, color science, regulatory requirements for use, mechanical and photochemical behavior of the pigmented polymer, optics, and so forth. Expertise of this variety cannot be expected to be obtained without careful... 

Figure 4.35 shows another example of a patented product from PVC suggested for manufacture by rotational molding. The fender (10) is composed of PVC pipe obtained by extrusion and attachment members made by rotational molding. 

The range of processes that may be used for fabricating a plastics product is determined by the scale of production, the cost of the machine and the mold, and the capabilities and limitations of the individual processes. For example, complex and precise shapes can be achieved by injection molding, hollow objects via blow molding and rotational molding, and continuous lengths by extrusion. 

The elastomers and film products highlighted in Table 4.1 represent examples of the introduction of new products into the polyethylene markets that were the direct result of the development of single-site catalysts. The injection molding and rotational molding markets remain dominated by Ti-based Ziegler catalysts. 

Many product designs are inherently limited by the economics of the process that must be used to make them. For example, to date TSs are not blow molded, and they have limited extrusion possibilities. Many hollow products, particularly very large ones, may be produced more economically by the rotational process than by blow molding. The need for a low quantity of products may eliminate certain molding processes and indicate the use of casting or others. 

Process used provides different control capabilities. As an example closed molding (injection, compression, etc.) provides fine detail on all surfaces. Open molding (blow molding, thermoforming, spray-up, etc.) provides detail only on the one side in contact with the mold, leaving the second side free-formed. Continuous production (extrusion and pultrusion) yields products of continuous length. Hollow (rotational or blow) produces hollow products. These processes can be used creatively to make different types of products. For example, two molded or thermo-formed components can be bonded together to form a hollow product, or they can be blow molded. 

The injection molding with rotation (MWR) is an example of processing at lower temperatures, pressure, etc. It is also called injection spin molding or injection stretched molding. This BM process combines injection molding and IBM, as performed in IBM reviewed, except it has the additional step of with melt orientation (Dow patent). The equipment used is what is commercially available for IM except the mold is modified so that either the core pin or outside cavity rotates. The rotated melt on its preform pin is transferred to a blow mold. The end product can come directly from the I MM mold or be a result of two-stage fabrication malting a parison and BM the parison.164... 

Injection molding is the most popular and versatile process for manufacturing plastic products. Using a reciprocating injection molding machine as an example, as shown in Fig. 3, polymer pellets are firstly fed into the hopper, which delivers the resin to the plasticizing screw. The screw rotates and the polymer pellets are fed into its channels. 

If permitted by the product geometry, ejector pins with the largest possible diameter (about 20 mm) have to be chosen to avoid impressions on the opposite side or a breakthrough of the molded parts. Ejector pins can also provide ventilation under, for example, tall, free-standing bosses and ribs to avoid gas entrapment. In the case of contoured surfaces, the pins must be secured against rotation. 

The use of pneumatic cylinders for clamping molds is possible. However, exclusive materials have to be used (e.g., seals from Kalrez ) for the cylinders due to typical temperatures in the rotational production, which will then lead to very high production costs of these special cylinders. Because of the use of such closures, pneumatic cylinders are therefore only suitable for mass production of, for example, planters and children s toys. An example in Figure 1.182 shows a circular spider construction for eight planters with 700 mm diameter each. 

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