end of the mixing cycle to simulate the letdown chamber effect next the valve between the spin cell and the accumulator is opened and then the spinneret orifice is opened immediately thereafter in rapid succession the resultant flash spun product is collected in a stainless steel open mesh screen basket because of the relatively small amount of material and high pressure used most of the spins in these examples lasted only a fraction of a second e g 0 1 to 0 5 seconds it usually takes about two to five seconds to open the spinneret orifice after opening the valve between the spin cell and the accumulator when letdown chambers are used the residence time in the chamber is usually 0 2 to 0 8 seconds however it has been determined that residence time does not have too much effect on fiber morphology and or properties as long as it is greater than about 0 1 second but less than about 30 seconds when the valve between the spin cell and the accumulator is opened the pressure inside the spin cell drops immediately from the mixing pressure to the accumulator pressure the spin cell pressure drops again when the spinneret orifice is opened because of the pressure drop in the line the pressure is measured during spinning just before.