Rear ventilation allows air to escape upwards, unlike other systems that use a piston, which is more likely to result in entrapped air
and bubbles in molded parts, KM says.
Without venting this entrapped air
, blowholes can be produced.
"Surface voids are usually found on vertical casts as a result of entrapped air
or water," notes Martin Engineering Vibration Product Specialist Larry Horrie.
A vacuum removes entrapped air
from the preform and resin is infused into the preform and cured.
Apparently, the entrapped air
promotes the surfaces to be super hydrophobic.
If the elevated discharge (H) is greater than the height between the tank and high point (J), the pressure within the entrapped air
column will increase sufficiently to stop all flow from the elevated reservoir (see Figure 3).
First the crew attached a vacuum pump to the liner to eliminate entrapped air
and make wet out easier.
In addition, Airase 4500 defoamer is designed to eliminate foam, pinholes and entrapped air
in water-based inks, adhesives and coatings, without generating surface defects.
The mixtures were then degassed in vacuum desiccators for 1 hour to remove the entrapped air
, followed by pouring into trapezium shape release-coated silicone mould before cured at room temperature for 24 hours.
* Place wetted paper on to the area under test, pressing firmly into contours and irregularities to remove any entrapped air
The HSOP light scattering efficiency rises with increasing average coating refractive index (i.e., increasing [TiO.sub.2] content), because the difference in refractive index between the entrapped air
void and its surroundings increases.
Hence, the numerical values are deduced from the simulations by taking the water level and deducting the height of the (possibly present) entrapped air