The Vibration-Assisted  Injection  Molding  Concept
Vibration-assisted  injection  molding (VA I M) is  based  on  the
concept of introducing mechanical oscillatory energy to the polymer  melt  by  oscillating  the  injection  screw  axially  during  the  injection and/or packing stages of the molding cycle. Conceptually,the  applied  vibration  energy  appears  to  affect  the  rheological  behavior  of  the  polymer.  This,  in  turn,  affects  the  morphological state  throughout  final   products,  thereby  enhancing  the  final   product performance characteristics. It is well known that the rheological  behavior  of  a  polymer  is  dependent  on  the  pressure,  temperature, and shear rate distributions that are present during processing. In general, shear stresses induced during the injection stage  tend  to  relax  during  the  packing  stage.  The  material’s  temporal  rheological  behavior  along  with  the  rate  of  cooling  affect molecular orientation and relaxation processes, which in, essence,determine  the  final   morphology  throughout  molded  articles.  The application  of  vibrational  energy  to  the  polymer  melt  during  the
injection  and/or  packing  stages  enables  some  control  over  pressure and strain histories, which, in turn, result in altered rheological  states. Therefore,  it  naturally  follows  that  final   morphological states  would  also  be  modified.   In  essence,  the  VAIM  technique can be considered to be a traditional molding process with added real-time  morphology  control.
Experimental VAIM  Capability  Establishment
To study the effects of vibration-assisted injection molding experimentally, a facility was developed that applies mechanical energy to polymer melts during molding by oscillating the injection screw  in  a  compression-decompression  manner. This  was  accomplished  by  developing  an  open-loop  hardware/software  control system  to  actuate  hydraulic  valves  appropriately  and  produce  a forward-rearward  motion  of  the  injection  screw. The  detailed  description  for  the  development  of  the  VAIM  capability  can  be found  in.
The  actual  injection  molding  machine  utilized  during  the present  study  was  a  BOY  15S.  In  addition,  a  LVDT  transducer was installed onto the machine to monitor the screw position during  the  cycle. A Reglomat  RT20,  closed-loop,  hot-water  thermolator  was  used  to  control  the  temperature  of  an  ASTM  standard tensile  test  mold  with  two  Kistler  pressure  transducers  embedded in the cavity. Type I tensile test specimens were produced in compliance  with ASTM  D638.
The experimental system was configured  so that the VAIM controller  would  dictate  the  action  of  the  machine  hydraulic  control valve  during  the  injection  and  holding  and/or  packing  stages  of molding processes. To supply oscillatory pressure vibrations to the polymer  melt,  the  VAIM  controller  simulates  the  manual  operation  of  pushing  and  releasing  the  injection  and  decompression switches on the injection molding machine in an alternating fashion.  Choosing  to  control  the  process  in  this  manner  enables  the completion  of  vibration-assisted  molding  tests  with  constant stroke  amplitude  while  varying  other  parameters,  such  as  vibration  frequency.  The  oscillatory  mechanical  action  can  be  applied to the polymer melt in a manner specified  by the user throughout the  injection  and  packing  phases  of  each  molding  cycle  as  explained  in  the  following  section. 回收塑料材料注射成型英文文献和中文翻译(3):http://www.youerw.com/fanyi/lunwen_17270.html