Normal speed injection machine is below 300mm/sec; high speed can upto 900 or more. So the material didn't cool down so fast.
Normal machine can add N2 gas to improve speed but the speed can't be control;
High speed machine have two nozzle; One is screw and another is burrel. Speed and pressure can be controled;
I ever made SD cover thickness about 0.16mm with this kind of machine. we use Funac.