The authors have examined the performance of four configurations of screws and nonreturn valves
, and have determined which combination will enhance color mixing performance.
This area is dry and has recently had nonreturn valves
Finally, the presentation examines the use of nonreturn valves
in the system, the potential benefits of using variable speed drives in conjunction with gas boosters and the significance of 'ramp rates.
Over half the NSB machines sold are used for production of clear PET cosmetic containers, an application made possible, Novapax says, by its screw designs, nonreturn valves
, and highly accurate temperature control.
Unfortunately, variability is a fact of life due to check-ring design, wear factors, contamination, lack of maintenance, and the fact that most nonreturn valves
have a propensity to leak differently from shot to shot.
Spirex will introduce the PowerPurge system, which cleans screws, barrels, and nonreturn valves
without disassembling the injection unit.
Also showing Mallard four-piece nonreturn valves
, and Wexco bimetallic barrels.
According to consultant Jack Stroup of Cuyahoga Falls, Ohio (formerly an executive at Van Dorn Plastic Machinery), who has been working with Dray to develop the new valve, typical nonreturn valves
require excess pullback beyond that which is needed to prevent drool into an open mold.