The proper size of orifice diameter is very important for extrusion blow molding (EBM). Large air inlet orifices provide high blowing air pressure. As high a blowing air pressure as possible is desirable to give both minimum blow time (resulting in higher production cycle rates) and finished products that faithfully reproduce the mold surfaces. Often too high blow pressure will blow out the parison. So orifice diameter can not too large. Small diameter provide small blow pressure, and result in long cycle time. Too small pressure will yield end products lacking surface detail. So what size diameter is suitable need experiment and experience. Below table 1.1 of the air entrance orifice size for your reference.
Orifice diameter Product capacity
(in) (mm) (vol.)
1/16 1.6 Up to one quart (0.95 liter)
1/4 6.4 1 quart – 1 gallon (0.95-3.8 liter)
1/2 12.7 1gallon – 54 gallons (3.8-205 liter)
Table 1.1 Guide to air entrance orifice size for extrusion blow mold (EBM)
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