Injection molding controls

Distances can be controlled during injection molding. Control of distances is critical to producing high quality products at alow cost because longer distances result in longer cycle times. The most common distances are used for mold close, dosage or shot size, cushion or pad, screw return, mold open, and ejection. 

In injection molding control, along with cavity pressure, nozzle pressure, melt temperature, melt viscosity, and mold separation are widely employed. Process variables are dependent upon the collective effect of the machine setting. Process variables are melt temperature, melt pressure, melt front advancement, shear stress, and the rate of heat dissipation and cooling. 

Principles of process control Instrumentation Data acquisition/monitoring Servo control for injection molding Control of extrusion processes Blow molding/parison control SPC/SQC... 

D-Tex Intermeshing twin screw extruder, Davis- Standard DAC Injection molding control, Hunkar... 

Gompared with injection molding, control of the anisotropy by orientation of wood flour is difficult in extrusion molding. Anisotropy has many demerits, except for some properties such as use in a sound component In order to overcome these demerits, cross-sectional design of the composite is elaborated in many cases rather than controlling the orientation by molding conditions. 

Injection Molding. Any standard design plunger or reciprocating screw injection machine can be used for PEA 340, although a reciprocating screw machine is preferred (32). Slow injection into mold cavities avoids surface or internal melt fracture, and control of ram speed is important at low... 

Mold Coolers for Plastic Injection Molding. Heat pipes are used for local temperature control in the injection molding of plastics (see Polymerprocessing). A heat pipe is often used to force local cooling within a mold to speed operation, control viscosity, retention of material in a difficult mold area, or to reduce thermal stresses on cooling. 

PS or copolymers are used extensively in injection blow mol ding. Tough and cra2e-resistant PS containers have been made by multiaxiaHy oriented injection-molded parisons (238). This process permits the design of blow-molded objects with a high degree of controlled orientation, independent of blow ratio or shape. 

Extrusion Resins. Extmsion of VDC—VC copolymers is the main fabrication technique for filaments, films, rods, and tubing or pipe, and involves the same concerns for thermal degradation, streamlined flow, and noncatalytic materials of constmction as described for injection-molding resins (84,122). The plastic leaves the extmsion die in a completely amorphous condition and is maintained in this state by quenching in a water bath to about 10°C, thereby inhibiting recrystallization. In this state, the plastic is soft, weak, and pHable. If it is allowed to remain at room temperature, it hardens gradually and recrystallizes partially at a slow rate with a random crystal arrangement. Heat treatment can be used to recrystallize at controlled rates. 

Understand the critical properties of the mixed compound that affect processability. It should be understood that the properties and acceptable operating values of those properties, which control the compound processability, are dependent on the processes under consideration, e.g., hot or cold feed extrusion, compression or injection molding. 

To ensure consistency, the two critical areas for control specific to injection molding are shot size control and temperature control on the injection system, i.e., screw portion for the reciprocating screw machines, and both the screw and ram sections for the screw/ram machines. As mentioned previously, for temperature and cure control, the use of microprocessor controls has significantly improved the performance of injection molding machines, including control of the shot size. 

MOLDEST Provides product design, mold design, and injection molding process control by Fujitsu Ltd., Tokyo, Japan. 

In order to judge performance capabilities that exist within the controlled variabilities, there must be a reference to measure performance against. As an example, the injection mold cavity pressure profile is a parameter that is easily influenced by variations in the materials. Related to this parameter are four groups of variables that when put together influences the profile (1) melt viscosity and fill rate, (2) boost time, (3) pack and hold pressures, and (4) recovery of plastica-tor. TTius material variations may be directly related to the cavity pressure variation. Details on EQUIPMENT/PROCESSING VARIABLE are in Chapter 8. 

The extrusion process has fewer process control problems with TPs than does injection molding but has greater problems in dimensional control and shape. During... 

Examples of the more sophisticated controls used with injection molding are seen in Figs. 8-70 and 8-71. Based on the process... 

Injection Molds and Molding A Practical Manual , 2nd Edition, Joseph B Dym Kluwer Academic Publishers (1987) ISBN 0442217854. Highlights include a description of CAD/CAM potential and process control capabilities, and a... 

Design of injection molding equipment to produce car bumpers made from polymers Designing feedback control systems for bioreactors... 

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