Shock pattern (corrugated)
  PS rigid plastics parts in the gate near the surface, forming a dense corrugated to gate as the center. When called shock pattern. The reason is the melt viscosity is too large to stagnant form filling, the front end of the material exposed to the cavity surface soon condensing shrinkage, alternate and then melt and swell open cold material has contracted to continue process can make the material flow formed surface seismic lines in advance.
Solution:
(1) improve the barrel temperature especially nozzle temperature, should also increase the mold temperature.
(2) increase the injection pressure and speed, the fast filling cavity.
(3) improve the runner, gate size, prevent excessive resistance.
(4) die exhaust to be good, to set the cold slug well enough.