Ram speed

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... 

The second effect of ram movement usually works in the opposite direction (slower ram speeds plus a dwell at the peak press may cause, an increase in density). This effect is due to the fact that, at loading pressures usually used, expls are stressed beyond their yield points and creep or flow plastically. This effect, of course, becomes more important at vary high pressures, such as those used for delays. In addition to increasing the density, slower speeds plus dwell of the ram result in a more uniform density 4) Pelletizing... 

Rough surface distortion Use of scorched blank, less mould flow time, slow closing of the mould. Reject seemingly scorched stock, correct ram speed. 

Finally, Fig. E13.21 shows the recommended ram speed, and Fig E13.2m shows the weld-line locations. 

Fig. 5 A graph of ram force as a function of length-to-radius ratio, depicting conditions under which surface defects occur when extruding microcrystalline cellulose-lactose-water (5 5 6). Die diameter = 1.5 mm ram speed cm/min ...

Pressurization rate or ram closing speed depends on the size and shape of the billet and the type of resin. The slower the ram speed, the more completely the air will leave the preform, but productivity suffers at a low closing rate. Very fast ram speeds lead to entrapment of air, resulting in high porosity and low density areas, even billet cracking. Table 5.2 provides ram speeds that offer compromises between productivity and part quality. 

Reduce the velocity of melt Enlarge runners, gates, or cavities. Slow ram speed. Polymer degradation. Premature melt freeze. 

Tab. 8.10 summarizes some technical information for high pressure ram extrusion presses. Tab. 8.10a presents machine details and Tab. 8.10b indicates the approximate briquette output per channel of the shapes shown at the top. In Tab. 8.10b impact area means the face area of the ram that is contacting (impacting) the material to be briquetted it is approximately equivalent to the face area of the briquettes as represented by the shapes specified in the first three lines of Tab. 8.10b. As mentioned before, at typical ram speeds the contact time is so short for each cycle (0.04 s was mentioned, see above) that compacting is often referred to as being carried out by a blow.

Fig. 2-15. (a) Injection stock temperature vs. injection ram speed, barrel temperature, screw back pressure, injection pressure, nozzle diameter, and screw speed, (b) Injection time vs. injection pressure, barrel temperature, and nozzle diameter. 

This refers to the speed of mold filling, that is when the screw is acting as a ram. When molding thin sectioned components, high injection speeds (sometimes called screw displacement rates or, plunger injection speed or, ram speed ) are essential in... 

Ram speed. When one is selecting the injection speed, careful consideration must be given to adequate mold venting, resin melt temperature and injection pressure, along with the potential for jetting. 

Figure 4 A force-displacement profile for a microcrystalline cellulose-lactose-water mixture showing the three stages of extrusion on a ram extruder Compression, steady-state flow, and forced flow (ram speed, 4mm/sec die diameter, 1.5 mm L/R ratio, 12). (From Ref. 31.)...

Steady state was possible with the MCC and MCC lactose samples but not with lactose alone. As can be seen with the MCC samples, the duration of the compression stage was water level dependent with no effect seen on the steady state stage. Additional studies indicated the effect of ram speed (extrusion speed) and die LjR ratio. An increase in ram speed increased duration of the steady-state stage with no effect on the compression stage. The LjR ratio had no effect on either compression or steady state. Wet mass composition, therefore, influenced the ability to achieve steady state while the water level and ram speed influenced duration. Higher water levels decreased the force to produce steady-state flow but increased... 

Figure 9 Force-displacement profiles at various moisture contents of mixtures of microcrystalline cellulose and water (a-d) microcrystalline cellulose-lactose-water (5 5 6) (e) lactose-water (8 2) (f) at a ram speed of 4mm/sec, die diameter of 1.0, and a L/i ratio of 12. Percentage of moisture content of microcrystalline cellulose-water mixture a, 59.4 b, 51.1 d, 45.0. (From Ref. 29.)...

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