Selected Vibration  Related  Processing Variables
To study the effects of vibration-assisted injection molding, six parameters  related  to  the  imposed  vibration  were  selected  as  follows:  Delay  time  to  begin  vibration,  vibration  duration,  vibration frequency, intracycle compression duration, intracycle decompression  duration,  and  duty  cycle.  The  first   three  of  these  parameters are  self-explanatory.  ‘‘Delay  time  to  begin  vibration’’  is  the amount  of  time  between  the  start  of  injection  and  the  start  of applied  vibration.  The  vibration  duration  is  the  amount  of  time that the applied vibration continues once it is initiated, and lastly,the  vibration  frequency  defines   how  many  compression  and/or
decompression  cycles  are  applied  per  second  while  the  vibration
is  ongoing. The  intracycle  compression  and  decompression  durations  correspond  to  the  amounts  of  time  that  the  injection  screw forward  valve  and  injection  screw  backward ~decompression! Are activated  in  each  mode  during  each  vibration  cycle.  The  duty cycle is determined basically by the ratio of the screw forward to the  screw  backward  duration  per  cycle.  The  latter  three  parameters combine to indirectly control the amplitude of the screw oscillation.
Experimental  Design
Materials and Product Selection. The material type utilized throughout  the  study  was  polystyrene (PS).  The  specific   new  or virgin  material  used  was  STYRON  666DW  produced  by  Dow Corporation.  This  material  has  an  average  molecular  weight  of approximately  230,000  g/mol  and  a  claimed  tensile  strength  of 44.8  MPa.  For  a  recycled  material,  PC-9000,  which  is  a  very low-grade  recycled  PS  available  from  Polystyrene  Recycling Company of America (PRCA), was selected. This recycled material  has  an  average  molecular  weight  of  approximately  100,000g/mol.  During  the  study,  the  two  materials  were  processed  inpidually  and  in  the  form  of  two  blends.  The  two  blends  selected possessed  virgin  to  recycled  weight  based  mixtures  of  75/25  and 50/50,  respectively.
The  injection  molded  parts  produced  and  tested  during  study were  ASTM  D638  Type  1  specimens.  Two  pressure  transducers were installed, roughly centered in each grip section of the ASTM tensile  specimen  cavity,  to  monitor  the  pressure  changes  during the  cycle  due  to  the  vibration  energy  applied  by  the  injection screw.
The focus product quality characteristic on which the study was based  was  the  ultimate  axial  tensile  strength  of  the  specimens produced.  This  parameter  was  determined  by  performing  standardized  tensile  tests  on  a  Measurement  Technology  Inc. (MTI)Phoenix  mechanical  testing  machine.  During  all  mechanical  testing, the specimen elongation rate imposed was 5 mm/min and the ambient  temperature  was  kept  at  23°C. 回收塑料材料注射成型英文文献和中文翻译(4):http://www.youerw.com/fanyi/lunwen_17270.html