Ejection pressure

If a vertical wall is required with no taper, it can be accomplished. However cost of mold is significantly increased since more action will be required in the mold such as moving its sidewalls to release the molding and higher ejection pressure mechanisms are required. 

Structurally diverse cannabinoid CB1/CB2 agonists inhibit peristalsis induced in segments of isolated intestine (ileum or colon) by continuous luminal fluid infusion (41) or electrical field stimulation (43). Indeed, these agonists seem to reduce both the preparatory phase of peristalsis (i.e., longitudinal muscle contractions in response to flnid or electrical field stimulation) as well as the subsequent emptying phase in which intestinal circular muscles contract towards the aboral end. Overall, cannabinoids increase the threshold pressure and the volume for triggering peristalsis but decrease comphance and ejection pressure. 

FIGURE 8.8 The ejection effect, showing that early during blood ejection (systole) the heart generates somewhat less pressure than expected, denoted deactivation (down arrows). Later in systole, the heart generates greater pressure, denoted hyperactivation. Curves 1 and 2 are ventricular pressures for initial and ejected volumes, respectively. Curve 3 is the measured ejecting pressure curve. Curve 4 is root aortic pressure. 

Kono A., Maughan W.L., Sunagawa K., et al. 1984. The use of left ventricular end-ejection pressure and peak pressure in the estimation of the end-systoHc pressure-volume relationship. Circulation 70 1057. 

Other factors that govern the quenching efficacy are the Jet diameter and the speed at which the wheel rotates. These two factors together are mainly responsible for the final dimensions of the amorphous ribbons. Fine orifice diameters and high wheel rotation speeds lead to relatively thin ribbons. The width of the ribbons generally increases with increasing wheel rotation speed as a result of a more effective spreading of the melt. In this respect an important influence is also exerted by the Jet velocity, which is determined by the ejection pressure of the inert gas. 

Most types of ejection methods are used, but due to the brittleness of PS, (and to prevent any cracking of the component taking place), mold surfaces should have draft angles of 1 to 3 degrees per side, and an even ejection pressure should be employed. 

To minimize such ejection stresses, forces for deep molded parts are designed with an appropriate draft or taper, up to 5° in some cases, such that very slight movement of the molded part with respect to the force will suddenly free the part from its strong grip on the force, and the remainder of the ejection stroke exerts almost no stress on the part. Such draft is advisable on all plastic parts, even those with depths of only 6 mm, to minimize ejection pressures and to prevent possible localized damage where the knock-out pins push against the not-yet fully hardened plastic. 

The process parameters that affect the quality of injection molding products include cooling time, injection pressure, injection speed, injection time, filling time, melt temperature, ejecting pressure, mold temperature, mold geometry shape, material property of melt, melt speed, and heat transfer action of flow field. 

The accuracy of the model was tested using a servocontrolled isolated heart preparation (Janicki et aL, 1974) whereby it was possible to have controlled ejecting and isovolumetric contractions. The model parameters (i.e., AI-A6 and yj were calculated from the ejecting pressure-volume data and the model was then used to predict the peak isovolumetric pressure. When the predicted and measured peak isovolumetric pressure from 10 experiments were compared a correlation coefficient of 0.97 was found (Figure 3). Similar results have been obtained in open chest experiments with the heart intact. 

ANS Yes. Our model is independent of valve resistance as well as filling volume and level of ejection pressure. 

ANS Yes, the time varying behavior of elastance will mathematically result in an inverse force-velocity relationship of muscle. However, as I have just shown there is an additional dependence of pressure on flow that is independent of volume and it is this additional pressure loss that must be accounted for by a resistance term. Furthermore, Dr. Suga recently published the results of a study which indicated a correction term had to be added to his time varying elastance model in order for the isovolumetric and ejecting pressure-volume relationships to coincide. This correction term was of the same magnitude as our resistance term. So you cannot just use a time-varying elastance to describe the dynamics of the left ventricle. 

Figure 10.12. Ejection pressure of polyetherim-ide part vs. concentration of release agent based on fatty acid. [Adapted, by permission, from Sanner, M. A., Soc. Plast. Eng., Inc., Antec, Conf. Proc., 1858-62,2003.]...

Figure 10.12 shows the effect of the content of a polyolefin release agent on the reduction of ejection pressure. With fatty acid amides, the reduction of ejection pressure is even more pronounced, but their presence may affect impact properties and thermal stability of materials. Polyolefin release agents were found to not affect mechanical and thermal properties of polyetherimide. 

Studies were conducted on molding polyetherimide with different types and quantities of mold release agents. It was concluded that a too high concentration of mold release agent results in reduced heat deflection temperature and Izod impact properties. Figure 10.12 shows how concentration of polyolefin release agent affects ejection pressure. ... 

Conventional solidification, annealing at high temperature and rapid quenching from the melt (p) were used to obtain precursor alloys exhibiting well defined microstructures. The rapid quenching was performed under helium atmosphere. The temperature of the melt before ejection was kept at about 1560°C. The influence of the ejection pressure and the rolling velocity on the microstructure have been reported previously (5,6). Undoped and doped Ni2 i MxAl3 base alloys were tested (M = Cr, Cu). 

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