Ram Injection Molding Machine

Example 4.1 Force Requirements of Ram Injection Molding Machines We consider a... 

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. 

Figure 4.12 Schematic of a ram (plunger) injection molding machine...

Blends were produced in a small Banbury mixer. About 3 lb of dry-blended material was added to the Banbury. After the flux point, blends were run for two more minutes and dumped. Conditions were speed No. 2, 30 psi on the ram, and a dump temperature of 310°F. Test specimens were molded on a 3-oz Van Dorn injection-molding machine front, middle, and rear zones were 500, 485, and 470°F, respectively. The mold temperature was 160°F the molding cycle was typical for ABS. Test methods were ASTM Standard Procedures. 

Fluoropolymers can be injection-molded in plunger or ram-type equipment but a screw machine works best with this family of plastics. The screw-type injection molding machines have a number of advantages including those listed in Table 6.23. Various components of screw-type machines for processing fluoropolymers are described in this section. 

In the ram extrusion method the parison is formed in a cyclic manner by forcing a charge out from an accumulated molten mass, as in the preplasticizer injection-molding machine. The transport arm cuts and holds the parison and lowers it into the waiting mold, where shaping under air pressure takes place (Figure 2.33). 

Figure 5.30 Schematics of ram and screw injection molding machine with a preloader usually providing heat to the RP compound...

Hydraulie drive elements like these are also the driving forces on injection molding machines. Figure 6-2 shows how the movement of a hydrauhc ram moves the toggle lever elamping unit of an injection molding machine. 

Can be processed on both ram and screw injection molding machines... 

Movable platen n. The large back plate of an injection molding machine to which the back half of the mold is secured during operation. This platen is moved either by a hydraulic ram or a toggle mechanism. 

Plate dispersion plug n. Two small, perforated, parallel disks joined by a central connecting rod. Such assemblies were sometimes inserted in the nozzles of ram-type injection-molding machines to improve the distribution of colorants in the resin as it flows through the nozzle. 

Polyliner n. A perforated, longitudinally ribbed sleeve that fitted snugly inside the cylinder of a ram-type injection-molding machine, replacing the conventional... 

Shot capacity n. The maximum weight of plastic that can be delivered to an injection mold by one stroke of the ram or screw. In the case of screw-injection molding machines that are not equipped with backflow-preventing valves at the end of the screw, slippage of material may occur in the screw flights and may not be reckoned with in calculations of shot capacity that are based on cubic displacement. 

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