Molded-part setting

The clamping debars (rods) can be used to support the fixed and movable platens on which the mold is attached. They serve as equally loaded tension support members of the clamp when the mold is closed. The open distance between tie rods through which the mold must fit and eject molded parts sets up the maximum outside dimensions of the mold that can be used. Different designs are used to meet different... 

The beater additive process starts with a very dilute aqueous slurry of fibrous nitrocellulose, kraft process woodpulp, and a stabilizer such as diphenylamine in a felting tank. A solution of resin such as poly(vinyl acetate) is added to the slurry of these components. The next step, felting, involves use of a fine metal screen in the shape of the inner dimensions of the final molded part. The screen is lowered into the slurry. A vacuum is appHed which causes the fibrous materials to be deposited on the form. The form is pulled out after a required thickness of felt is deposited, and the wet, low density felt removed from the form. The felt is then molded in a matched metal mold by the appHcation of heat and pressure which serves to remove moisture, set the resin, and press the fibers into near final shape (180—182). 

Molded parts (e.g., TV sets/business machines, computer housings, household appliances [hairdryer, curler], automotive parts, electronics,... 

The resulting program created a link between IMM capabilities, machine settings, and mold/part characteristics. The need to detect if a particular machine was certainly suitable for a specific job or not, was clear from the beginning. This situation is not typical, since the causes of machine inadequacy are not always directly evident. While the size of the tool is an obvious factor in the machine suitability, the clamping force requirements can remain questionable even with a complete set of the most advanced FEA analysis.1 The latter must be integrated with part quality, cost considerations, and skilled judgment of the complete project. 

In the injection molding process, setting the temperature involves optimization of the temperature profile of the plasticating unit (extruder barrel), temperatures of the mnners and gates, (aU these determine the molten polymer temperature) as well as the mold temperature. The temperature setpoints depend on the material type (viscosity profile, thermal and shear stability, thermal properties) as well as machine or process considerations (machine capacity to shot size ratio, screw design, mold and part design, cycle time, etc.). Temperatures of the two basic units, the injection system and the mold, should be discussed separately since their selection stems from very different considerations. 

The third mode is the shuttle method, where usually two or more sets of molds are used. Each set of molds can have at least two or more molds. Their blowing stations are around the periphery of the extruder die head and parisons. One set of molds in the open position is located under the die. With the proper length of the parisons (a parison for each mold), the open molds underneath close. After the molds are closed, parisons are cut, usually with an electrically charged hot wire, and quickly shuttled to a blow station, where blow pins are inserted into the parison openings. Blow-molding parts solidify and are released from the molds when they open. In the meantime, the parisons continue to be extruded as another set of open molds is positioned around these parisons. Thus, the molds alternately shuttle producing molded parts. 

For a number of years now, libraries of standards have been available in coimection with CAD programs. Both individual standard items and complete mold accessory sets can be called up. Individual parts of the mold accessory sets can be taken out and altered, whereby such changes are then also included in the 2D production drawings and parts lists. 

Every molded part can be custom blended while in production for optimum color usage and cost savings. Settings are recorded and used for exact repeatability on future runs. 

Examples of good preventive maintenance activities include (1) establish the frequency of lubrication and what types of oil or grease must be used (2) check for oil leaks and have a procedure to correct/eliminate them (3) check heaters, thermocouples, pressure transducers, and so on (4) set up schedules and procedure to clean machines and molds/dies (barrels, screws, sliding mechanisms, clamps, etc.) (5) check control circuits (electrical, hydraulic, mechanical, etc.) (6) schedule checks of conditions wherever questions of alignment, level, parallelism (mold parts, mold press, die system, etc.), and other similar situations exist (7) set up a schedule to check safety devices on all equipment and (8) schedule sessions to repeat instructions on safety equipment procedures to all personnel. Figure 11-8 shows where accidents usually occur (324, 325). 

TPV market is primarily in automotive sealing where TPVs are displacing EPDM in less demanding (e.g., static) molded window seals. However, compression set remains an issue in more demanding (e.g., dynamic) applications such as door seals. TPVs are also increasingly used in overmolding on engineering plastics to achieve soft-touch tactile feel to the molded parts. 

---